Chapter 27 Brewery Effluents, Emissions, and Sustainability

In the process of brewing and packaging beer, many secondary streams are produced that are not part of the beer product stream, and they cannot be used in the final product. There is also an inherent loss of product through the process, and much of this lost beer cannot be recovered and put back into the main product stream. Some of these streams that cannot be recovered and reused can be recovered and converted into valuable by-products. Technological advances and improved microbiological control continue to enable the brewer to reduce product losses and produce valuable by-products from materials that were previously not usable and considered waste. However, some secondary streams as yet have no viable reuse options, so they are discharged to the environment, with or without treatment.

Economics has been a primary incentive to reduce beer losses and to develop ways to produce valuable by-products from brewery waste streams. The cost and regulations of waste disposal and emissions—in solid, liquid, and gaseous effluent streams—also has a significant economic impact. Also, in recent years, a growing sense of social responsibility is evident in the vision statements of many companies, including breweries. They are using the concept of the triple bottom line,¹ first introduced by John Elkington in 1997. The triple bottom line consists of profits, people, and the planet. Profits are important because without profits the company will cease to exist. People refers to the social responsibility that a company has to its employees and to the society in which it does business, in fact the global society. Planet refers to concern for the environment. The goals become zero discharge, minimum carbon footprint, and green operations for environmental concerns and sustainable operations. Sustainability includes efficient use of raw materials, with minimum negative impact on the planet.

Sustainability means many things and has many aspects. Its goals include making positive impacts on profitability and social issues and preservation of the environment. In the production process, it has come to mean ongoing efforts to reduce waste and negative impacts on the environment—not just in the brewery itself but starting with the farmer and sources of other raw materials, all the way to the customer. This can mean buying raw materials from suppliers with the same sustainability goals to minimizing transportation of products and expanding production with new plants that are close to the market rather than shipping product long distances. These practices are among those embraced by global organizations such as the World Business Council on Sustainable Development.²

A basic goal in achieving sustainability is the dedication to energy conservation in the design and operation of the brewery. More and more breweries, primarily in the United States, have signed the Climate Declaration, launched by the nonprofit organization Ceres in 2013. The Climate Declaration calls on businesses and policy makers to take action and implement sustainable business practices to combat climate change. Through this advocacy, breweries in their own ways have improved sustainability in all phases of the brewing business, including complete life cycle analyses of their products.³ Breweries, large and small, are striving to reduce greenhouse gas emissions; to minimize their carbon footprint, water usage, and beer losses; to minimize waste; and to operate efficiently.^4–7

Around the world, large breweries and small craft breweries alike have adopted sustainability programs. All have the goal of being profitable so they can stay in business. Many have special programs for people, such as promoting responsible consumption of alcoholic beverages. Other sustainability activities give attention to the planet to ensure a clean and safe environment. In many cases, these programs go above and beyond what is required by local environmental regulations. Most have benefits in two and sometimes all three parts of the triple bottom line. There are many common efforts among breweries such as using fewer hectoliters (hL) of water and less energy for each hectoliter of beer produced. Other activities for sustainability, such as some types of waste treatment or collection and purification of carbon dioxide (CO₂) for reuse, are viable in large breweries but not economically feasible in small breweries. Despite this, aggressive goals for improvement are being established and achieved by breweries of all sizes.

27.2 EFFLUENTS, EMISSIONS, AND EFFICIENCIES IN THE BREWERY

The following sections of this chapter examine the different areas of brewery operations and how they affect the profits, people, and the planet in terms of effluents, emissions, and energy usage. Emissions and effluents are described along with various treatment options. Progress in reducing energy usage and beer losses throughout the process is also reviewed.

Measurements used to describe effluents are biological oxygen demand (BOD), chemical oxygen demand (COD), and suspended solids (SS). The units of COD are milligrams of oxygen required to chemically oxidize all of the oxidizable organic material (both soluble and insoluble) in 1 L of the liquid effluent. The units of BOD are milligrams of oxygen required to oxidize all of the biologically oxidizable organic material in 1 L of the liquid effluent solution. The COD level of a given sample is often around two times the BOD level.

Suspended solids are reported as milligrams of insoluble materials present in 1 L of effluent. BOD and SS are also reported per unit of production (e.g., kg BOD/1,000 hL of beer produced).

Air emissions such as particulate matter (PM) or volatile organic compounds (VOCs) are reported as tons of particulate matter per year from a source, or as tons of VOC per 1,000 hL of beer produced. Particulate matter consists of solid and liquid particles that are suspended in air. VOCs are compounds that contain carbon and evaporate at room temperature. Some particulate matter and VOCs may be hazardous and may be regulated. A few gases (or groups of gases) are classified as greenhouse gases by the Kyoto Protocol because of their contributions to global warming. Each gas or group of gases has a global warming potential (GWP) number assigned relating back to CO₂ whose GWP = 1.

Greenhouse Gas	Global Warming Potential
CO₂ (carbon dioxide)	1
CH₄ (methane)	25
N₂O (nitrous oxide)	298
HFCs (hydrofluorocarbons)	124 to 14,800
PFCs (perfluorocarbons)	7,390 to 12,200
SF₆ (sulfur hexafluoride)	22,800

Utility usage is normally reported as an amount used to produce a given amount of beer such as kilowatt hours (kWh) of electricity used per 1,000 hL of beer produced. Water usage is reported as the volume of water used to produce one volume of beer, for example, 7 hL of water/hL of beer.

27.2.1 The Brewhouse

27.2.1.1 Dust

Receiving and conveying grains and other raw materials into the brewery can be a source of dust emissions into the atmosphere. Inside the brewery, additional conveying, grain cleaning, milling, and weighing generates more dust. The dust is typically collected using a cyclone separator at the end of a pneumatic conveying system. In some cases, dust from these operations is collected with a vacuum system that has bag filters to keep the dust from being exhausted to the atmosphere. In employee work areas, this may be an important step to ensure worker safety.

27.2.1.2 Atmospheric Emissions, Aromas

The mashing and wort boiling processes produce aromas that are considered pleasant and, in most localities, they violate no emission regulations. Measurements by the California Environmental Protection Agency (EPA) Air Resources Board showed that brewhouse vessels contribute 0.85 to 1.7 kg of VOC/1,000 hL (2.2 to 4.4 lb/1,000 US bbl) of beer produced.⁸ More than half of the total comes from the brew kettle.

Some breweries have decided, even though it is not required by local regulations, to eliminate both the aromas and the sight of steam leaving their brewhouse to maintain positive relations with their neighbors and the community. In a few cases, this is conducted in order to comply with local regulations. The two most effective methods to eliminate the steam vapors are to recompress the vapors and reuse them for heating elsewhere in the process or to condense the exiting steam in water-cooled heat exchangers as it leaves the vessels.⁹ The condensing steam heats some of the water required for mashing and sparging. Once condensed, the condensate containing aroma compounds is discharged as wastewater because it contains flavors that make it unsuitable for recycling as brewing water.

27.2.1.3 Effluents

The brewhouse generates liquid waste streams produced during lautering or mash filtration, from processes that separate hops and trub in hot wort after boiling, and cleaning-in-place (CIP) rinses and cleaning solution discharges. Additional effluent streams are generated if the spent grain is dewatered.

27.2.1.3.1 Lautering

When wort runoff to the kettle is complete, based on a low final gravity of the runoff liquor, the liquid still draining from the spent grain is diverted from the brew kettle to a final collection tank or to the sewer. If collected, these last runnings are called sweet water and are used in a subsequent brew to improve both brewhouse efficiency and reduce water use. Recovering the extract in this liquid has the positive effect of increasing brewhouse efficiency but with the possible negative effect of adding end-of-sparge components that have negative flavor effects on the final product.

When sweet water collection is complete, the liquor remaining in the grain bed is usually drained to the sewer. At this point, the wet brewer’s grain still contains 77% to 81% moisture. After discharging the wet grain from the lauter tun to a holding tank, the area under the false bottom is rinsed. The rinse water, which may contain a considerable amount of suspended solids, is usually drained to the sewer. Mash filter plates are also rinsed to the sewer after the filtration of each brew (further details in Chapter 11).

It is estimated that the total volume of lauter tun effluent plus rinses discharged to the sewer varies between 40 and 120 hL for each 1,000 hL of final product.¹⁰ The dissolved solids concentration in this effluent may vary from 0.4 to 3.0°Plato, whereas the suspended solids concentration may be as high as 1.0% w/w. Typical solids produced per 1,000 units of production are shown in Table 27.1.

Table 27.1 Effluents from Lautering

	Concentrations of Solids in Effluent	Range per 1,000 hL Produced	Typical Amount per 1,000 hL Produced	Typical Amount per 1,000 US bbl
Effluent + rinses		40–120 hL
Dissolved solids	0.4–3.0°P	16–360 kg	120 kg	300 lb
Suspended solids	up to 1% w/w	40–120 kg	40 kg	100 lb

This “typical” lautering effluent contributes 100 kg BOD/1,000 hL produced (260 lb/1,000 US bbl). Studies in the literature report BOD from lautering effluents equivalent to 2 kg BOD/1,000 hL to more than 200 kg BOD/1,000 hL packaged.¹⁰ Breweries have made considerable improvements in this sewer loading that were reported in 1986 when Pabst Olympia reduced the BOD load of last runnings from 210 to 8 kg BOD/1,000 hL packaged (from 560 to 20 lb/1,000 US bbl).¹¹

Wet brewer’s grain may be dried or sold wet. Before drying, it may be dewatered, creating another high-strength effluent. Dewatering is performed with a centrifuge or a filter press, and the water that is removed (press liquor) can be up to 3.5% dissolved solids and up to 5% suspended solids.¹⁰ This stream is usually discharged into a sewer, but it could be combined with the other lauter tun effluents and waste beer. This combined stream is processed to make by-products such as brewer’s condensed solubles (BCS). Drying spent grains with no dewatering has the advantage of not dealing with the liquid effluent stream that is created. When the grain is dried, BOD costs are reduced. In addition, the protein level of dried grains is higher than in dewatered spent grains.¹²

Discharge of brewer’s grain liquor to the municipal sewer or to the plant’s waste system was formerly the most common way of disposal. However, brewers have evaluated the economics of other options due to wastewater surcharges based on the concentration of BOD and suspended solids. Dissolved solids (DS) in this stream contribute from 0.5 to 1.0 kg BOD/kg DS, whereas suspended solids (SS) contribute to BOD by as much as 0.45 to 0.75 kg BOD/kg SS.¹⁰

The amount of wet brewer’s grains remaining is approximately 20 kg/hL of a 12°Plato beer (52 lb/US bbl). Wet brewer’s grains are around 80% moisture, and around 42% of their weight can be removed as press liquor. This means 8.5 kg of press liquor is removed from the spent grains per hectoliter of wort (22 lb press liquor/US bbl of wort).

The total amount of BOD and suspended solids in press liquor are calculated for the following example:

The amount (weight) of press liquor is assumed to be 42% of the weight of the wet brewers’ grain.
The amount of wet brewer’s grain is assumed to be 20 kg wet grain/hL of packaged product (52 lb/bbl).
The amount of press liquor would be 8.4 kg/hL packaged (22 lb/US bbl).
If this liquor has a dissolved solids concentration of 2% (wt/wt) and a suspended solids concentration of 1% (wt/wt), the amount of dissolved solids is 0.17 kg/hL (0.44 lb/US bbl) of packaged product, and the amount of suspended solids is 0.085 kg/hL (0.22 lb/US bbl )of packaged product.
The total BOD in spent grain press liquor is in the range 0.124 to 0.236 kg/hL (0.32 to 0.61 lb/US bbl) of packaged product.

Prior to disposal, press liquor is often further clarified by centrifugation and/or screening. Screening equipment includes vibrating screens or hyperbolic screens with screen sizes of 75 to 100 mesh. Hyperbolic screens can reduce press liquor SS, including their contribution to this stream’s BOD, by about 60%. The recovered solids can be returned to the wet or pressed grains to become a by-product instead of a pollutant.¹⁰

27.2.1.3.2 Spent Hops

The average hops usage for US breweries in 1977 was 0.09 to 0.14 kg/hl (0.22 to 0.35 lb/US bbl).¹³ By 2015, the average hops usage in the American craft beer sector had grown to 0.57 kg/hl (1.46 lb/US bbl).¹⁴ Only about 15% of the hop constituents end up in the beer at low International Bitterness Unit (IBU) levels and much less at high IBU levels. More than 85% of the original hop material will become spent hops requiring disposal.

Hops usage currently is mostly in the form of pelletized hops and hop extract (details in Chapter 7). Most of the solids from pelletized hops are separated from the hot wort along with the trub, and this process is discussed in the following section. Use of hop extracts produces essentially no effluent.

When whole hops are used, the spent hops leaves and other material are separated from the hot wort in a strainer called the hop jack. A filter bed is formed in the hop jack, and it also traps a large portion of the trub. If the spent hops for beers with around 12 IBUs are discharged to the sewer, the BOD and SS levels in the effluent are as shown in Table 27.2.¹⁵ If the IBU level of a beer is increased, both hop usage and whole hop waste increase faster than linearly due to lower hop efficiencies that occur with high IBU targets.

Table 27.2 Solids and BOD with Whole Hops for a 12 IBU Beer

	Amount/1,000 hl (kg)	Amount/1,000 US bbl (lb)
Hopping rate	0.09–0.14	0.22–0.35
Suspended solids	77	100
BOD	39	200

It is convenient to add spent hops to the brewer’s grain, but this compromises the quality (protein concentration) of that by-product.¹⁶ Due to their high moisture content, the fuel value of spent hops is usually too low to make combustion of spent hops economically feasible for heat generation. If by-product use is not available, the hop leaves are disposed of in landfills. Other by-product uses are discussed in Chapter 19.

27.2.1.3.3 Trub

Before and sometimes after wort cooling, solids are removed from the wort. These consist primarily of coagulated protein formed during mashing and wort boil along with solids from hops. Most of the mashing precipitate will remain with the brewer’s grain in the lauter tun but some is carried into the brew kettle with the wort along with other solid particles containing starch, lipids, and plant gums. During boiling, more components (proteins) coagulate to form the trub. Trub solids can be removed from the hot wort by settling, centrifugation, or filtration, but they are more commonly removed in a whirlpool tank (discussed in Chapter 11). After being removed from the wort, trub solids are often added to the spent grain. Sometimes, they are discharged to the sewer along with residual wort that remains with the trub. Wort loss is “appreciable” when using a settling tank such as a coolship, and wort recovery from the settled trub sludge is required.¹⁷ With a properly designed whirlpool, wort losses are 0.2% to 0.3%.

At the end of boil, wort contains 6,000 to 8,000 mg of SS/L. In a good whirlpool operation, these solids are reduced to 100 mg/L in the clarified wort. However, the settled trub in a whirlpool tank may still contain a considerable amount of wort, enough to increase brewhouse yields from 0.6% up to 1.5% or more if recovered.^{18, 19} Whirlpool operations conducted in dished bottom tanks have losses close to 5%.

Average values from several large US breweries²⁰ (expressed per 1,000 bbl of packaged beer) are:

Total trub solids	1,010 lb (390 kg/1,000 hL packaged beer)
Total suspended solids in this trub	340 lb (132 kg/1,000 hL packaged beer)
Total BOD in this trub	713 lb (276 kg/1,000 hL packaged beer)
Total recoverable wort extract	373 lb (144 kg/1,000 hL packaged beer)
Total BOD after wort recovery	411 lb (159 kg/1,000 hL packaged beer)

Recovery of wort from trub is accomplished using a filter press, a vibrating screen, a centrifuge, or by recycling the trub to the top of the grains in a lauter tun prior to sparging. The latter method is simple, but has a disadvantage—it can only be employed when the lauter tun is processing the same or similar wort type at the time of recycle. Recycling trub to the lauter tun has another disadvantage—it slows runoff and can decrease the efficiency of wort extraction.²¹ Recovery of wort by means of a decanting centrifuge has been successful and exhibits none of these disadvantages.¹⁹ Another method is recovery of wort from trub by means of cross-flow filtration.²²

27.2.1.3.4 Cleaning Operations

Other brewhouse effluents are rinses and spent detergent solutions from the CIP of brewhouse pipes and vessels (further details in Chapter 13). Heating surfaces in the brew kettle or external boilers can quickly become fouled with a buildup of burnt proteinaceous and carbohydrate materials. These surfaces may require cleaning after every one or two brews. Similarly, wort coolers are often cleaned after every one to four brews. The first rinse is normally sewered, the caustic and acid wash solutions are saved and reused, and the final rinse saved to be the next first rinse. If the caustic and acid wash solutions are not saved, an equalization tank may be required to prevent pH “spikes” in the effluent.

Brewhouse CIP protocols usually include an end-of-week cleaning of the brewhouse vessels with rinses and a strong (as high as 5%) caustic soda solution. Ideally, this solution is saved and used again. If it is sewered when the CIP is complete, it may create a significant wastewater concentration spike and require dilution or neutralization.

27.2.1.4 Energy Recovery

Wort cooling is probably the oldest significant energy-saving step in the brewing process. Fresh water that is used to cool brews to the fermentation temperature is heated by the boiling hot wort and saved for mashing and sparging future brews. Optimum design of the wort cooling operation includes the water balance—providing the right amount of water at the right temperature to satisfy process needs.

Many approaches have been taken to recover and use more of the brewhouse heat that would be otherwise lost. Most of these studies have concentrated on wort boiling and decoction mashes. Wort boiling, where up to 10% of the water in the brew kettle is evaporated, is significant if all of that heat is lost to the environment. Some of these improvements include:

Thermal vapor recompression,⁹ where high-pressure motive steam entrains vapors from the brew kettle. The resulting combined stream at an intermediate pressure is then used for heating.
Condensation of brew kettle steam in a heat exchanger using water that is heated to provide some of the mashing and sparge water for later brews.⁹
Specially designed hot water storage tanks to recover heat from more parts of the process and thereby satisfy all needs for hot brewing and CIP water.²³
Design of wort boiling systems that achieve the same process quality results with less than 10% evaporation.^23–26

27.2.2 Cellar Operations

27.2.2.1 Spent Yeast

For every yeast cell pitched (inoculated) into wort, three to five or more yeast cells are present at the end of fermentation than at the beginning due to yeast growth. On average, one or two of these cells is needed for pitching a subsequent fermentation, thereby requiring disposal of a significant amount of surplus spent yeast. There are many markets for spent brewer’s yeast, and in many areas, waste treatment systems do not accept a brewery’s surplus yeast in the effluent. Unfortunately, it is still common for small breweries to discharge all of their spent yeast to the sewer for subsequent waste treatment by someone else (further details of the disposal of spent yeast are in Chapter 14).

At the end of fermentation, the amount of yeast is at its highest, and most of it will be separated from the end-fermented wort. Some of this yeast is saved for repitching, but the bulk is surplus, and it is either sewered or sold as a by-product. Yeast that settles well is drained from the conical bottom of a uni-tank, or yeast scrapers may be used to manually push or pull settled yeast to the outlet of horizontal tanks. This settled yeast may contain from 8% to 15% dry solids. If the yeast is a nonsettling strain (nonflocculent), it can be removed from the beer by centrifuging (details in Chapter 15). After an aging period, a smaller amount of residual yeast in suspension and other insoluble solids are removed from the beer, some by settling as tank bottoms and some by filtration or centrifugation. Residual solids remaining in empty fermenters and other tanks in the cellaring process are usually rinsed to the sewer in the first step of the tank washing cycle.

Fassing centrifuges can clarify end-fermented beer when the yeast is powdery and does not settle. These are usually disk centrifuges with an intermittent bowl opening discharge or a continuous nozzle discharge. To function well, they require a reasonably constant feed consistency, which in turn may require agitation in the tank feeding the centrifuges. With proper operation, fassing centrifuges can produce a yeast slurry of more than 20% dry solids. In actual practice, an average yeast solids concentration of 17% to 18% is more achievable.

In a lager fermentation, dry solids in the surplus yeast typically amount to 230 to 310 kg/1,000 hL (600 to 800 lb/1,000 US bbl) of final product.^{10, 27} The solids in surplus yeast include yeast solids, beer solids, hops solids, and trub.

Settled yeast recovered from the bottom of fermenters or aging tanks contains beer (often called barm beer) that represents a loss of 1.5% to 2.5% of the total beer production. It is usually worthwhile to recover at least a portion of this beer from the fermenter yeast, not only to reduce beer losses but to avoid excessive BOD surcharges for the waste streams.²⁸ This is also very important in countries where excise taxes are paid on all beer produced during fermentation, including beer that is wasted. Beer in aging tank bottoms is usually not suitable for recovering and adding back to the main product.

Many breweries, especially smaller ones, discharge all surplus yeast to the sewer without recovering any entrained beer. This may contribute considerably to a brewery’s sewer loadings. For each 1,000 hL of beer produced, about 350 kg BOD and 230 kg of suspended solids (900 lb and 600 lb per 1,000 US bbl) could be discharged in this waste stream.

Methods to recover entrained beer from surplus yeast were reviewed in detail for 90 breweries by the Institute of Brewing and the Allied Brewery Traders Association in Great Britain. In 1985, this review was summarized by Young²⁹ and Boughton.³⁰ Their findings showed advantages for pressure leaf filters and filter presses over rotary vacuum filters and decanter centrifuges. They evaluated cake dryness, filtrate clarity, labor, and oxygen pickup. Since this study, cross-flow filtration using ceramic cartridges has been developed as a very effective way to recover beer from spent yeast.^{31, 32}

27.2.2.2 Carbon Dioxide

The CO₂ produced during fermentation offers another opportunity to improve sustainability. A 12°Plato, 65% fermentable wort produces about 3.7 kg of CO₂ /hL of packaged product (9.5 lb/US bbl). This is about 1 kg of CO₂ for every kilogram of ethanol produced. A small portion of this CO₂ partially carbonates the wort as fermentation proceeds, but about 90% of the total escapes to the atmosphere or to a CO₂ collection system. If the CO₂ is not collected, then CO₂ must be purchased for uses in the cellaring and packaging processes.

Carbon dioxide exhausted to the atmosphere may appear to be a significant contributor to the carbon footprint of a brewery or any fermentation process. It has been noted, however, that the CO₂ emission from a wine fermenter has a minor effect or possibly a negative effect on the carbon footprint. When it is compared to the atmospheric CO₂ absorbed by the growing grapes or other crops that are used, its carbon footprint is less, even when the carbon footprint of farm machinery used to grow the crops is included.³³ In spite of this, sustainable uses have been found for CO₂ so that it not discharged to the atmosphere. These include fumigating grain silos, neutralizing alkaline wastewater, and uses in greenhouses.

Some fermentation by-products present in the CO₂ are VOCs. Their concentrations have been measured in the CO2 as follows:³⁴

Component	μg/L (ppb)
Ethanol	1,070
Ethyl acetate	50
Acetaldehyde	5
Acetone	3

27.2.2.3 Lost and Waste Beer

Beer losses are a major source of BOD in brewery effluent, and they also represent losses of raw materials, utilities, labor, and plant capacity. Efforts to improve sustainability and reduce carbon footprint are therefore also focused on lost or wasted beer and brewing materials. Additionally, these losses occur in many different areas, so substantial reductions are difficult but possible.^{35, 36} Some beer loss is unavoidable in both brewing and packaging if product quality is to be maintained and product specifications are to be consistently met.

The BOD value of beer depends on the type of beer; for a 12°Plato lager beer, it is approximately 9 kg/hL (24 lb/bbl). A reasonable correlation exists among alcohol, residual dissolved solids, and the BOD of that beer:¹⁰

BOD (kg/kg beer) =

0.81 × dissolved solids (kg/kg beer) + 1.63 × alcohol (kg/kg beer)

For wort that is 15°Plato, the BOD is 0.81 × 0.15 × 10⁶ = 121,500 mg BOD/L. If this wort is fermented to 64% real degree of fermentation (RDF), the BOD is 0.81 × 5.4 + 1.63 × 5.0 = 120,000 mg BOD/L.

Other correlations have shown that the COD of wort or beer is linearly related to its gravity.^{37, 38} For example, if the specific gravity is 1.060 (15°Plato), the COD is 60 × 2,925 = 175,000 mg COD/L.

Beer losses in brewing and by-product processing include:

Beer lost with unrecovered fermenter yeast
Loss in presses and centrifuges during yeast harvesting
Losses due to over-foaming of fermenters and surplus yeast storage tanks
Residual beer left in fermenters and other tanks in the cellars
Beer left in spent filter cake and filter shells
Beer left in chill-proofing systems
Beer left in tanks and lines after a production run
Beer lost as a result of disconnecting hoses and swing panel jumpers
Leaks from pumps and clamp connections
Beer left in bright beer tanks and supply lines to packaging
Beer that is foamed out of bright beer tanks to reduce oxygen content
Out-of-specification beer that is discarded.

There are many opportunities to reduce beer losses as outlined by Bott³⁵ and Barnes.³⁶ They list process modifications, operational procedures, operator involvement, and process automation. An important area of improvement has been in methods to fill a pipeline at the beginning of a run and to displace all the beer at the end of a run.

27.2.2.4 Spent Filtration Media

Beer is filtered to remove yeast, proteinaceous and colloidal materials, fining and stabilizing agents, and bacteria. The key objective is to remove all yeast and other solids so that the beer’s clarity can be described as “brilliant.” Additional tighter filtration may be used to remove beer spoilage organisms. All filtration processes employ filtration media. These media, along with the solids removed from the beer plus some residual beer retained in the wet filter media, must be discarded.

The amount of waste generated, and therefore the amount of filtration media used to achieve the filtration objectives, can be reduced by cold storage in a lagering tank (which by itself may be sufficient for physical stabilization³⁹) and by centrifuging the beer before it is filtered. Sterile filtration can be replaced with flash or tunnel pasteurization, but this would likely contribute to a much greater carbon footprint.

Filter media that require disposal are as follows:

Diatomaceous earth (DE)
Perlite
Cellulose
Silica gel
Polyvinylpolypyrrolidone (PVPP)
Tannic acid
Filter pads
Filter cartridges
Sock filters
Cross-flow filters.

Landfill disposal is the easiest and most widely used disposal method for all of these filtration products. In many cases, filter washouts containing the diatomaceous earth or perlite along with residual beer and beer solids are discharged directly to the sewer. If the brewery is small enough compared to the host town, these discharges may not be too significant or even noticed. If the discharges are monitored, substantial surcharges for suspended solids may become high enough to justify a project to remove that material from the effluent and send it to a landfill or to one of the many recycling possibilities that have been developed. These are discussed in Chapter 19.

Spent filter cake from primary and polish filtration consists of diatomaceous earth or perlite, yeast, trub, and protein/polyphenol complexes. In addition, there will be cellulose filter aid, finings, and stabilization materials, if they are used. The filter discharge also contains beer that is left in the filter cake and filter shell. Diatomaceous earth usage for a large US brewery was found to be 0.15 kg/hL packaged (0.4 lb/US bbl).⁴⁰ This usage rate and the subsequent disposal problems can be decreased by applying automatic body feed control. This is performed by measuring the turbidity of the incoming beer and adjusting the feed body rate accordingly with feed forward control. Cross-flow filtration is also an effective technology that, when coupled with centrifuging, can totally eliminate diatomaceous earth for beer filtration.^{41, 42}

The effluent load for diatomaceous earth filtration has been estimated in Table 27.3.⁴⁰

Table 27.3 Effluents from Diatomaceous Earth Filtration

Measurement	kg/hL Packaged	lb/US bbl Packaged
Diatomaceous earth usage	0.15	0.4
Organic solids in filter cake	0.008	0.02
Stabilizers in filter cake	0.04	0.1
Total filter cake solids	0.20	0.52
Beer left in filter cake and housings	0.0065 (hL/hL packaged)	0.0065 (bbl/bbl packaged)
BOD generated	0.06	0.15

Some breweries employ dry discharge filters in which most of the beer is pushed out of the filter shell and the cake with CO₂. The cake is then mechanically removed from the filter elements by spinning, cutting, or vibrating and it is generally transported to a landfill. In most municipalities, the cost for landfill disposal is considerably less than for sewer disposal. Many breweries still discharge spent filter cake and rest beer to the sewer along with a considerable amount of rinse water. Typical sewer loadings based on the aforementioned example are 0.20 kg suspended solids/hL packaged (0.52 lb/US bbl) and 0.062 kg BOD/hL packaged (0.16 lb/US bbl). Spent filter cake slurries can be concentrated with vacuum or pressure filters^{40, 43} to a cake of about 35% to 39% solids. This cake can be disposed of in a landfill or utilized in a number of ways.

27.2.2.5 Cleaning-in-Place (CIP)

As in the brewhouse, cellar cleaning operations generate effluents that include rinses and spent CIP solutions from pipelines, tanks, and filters. In a CIP system, the first rinse is sewered, the recirculated caustic wash solution is saved and reused, and the final rinse is saved to be the next first rinse. The first water rinse (that is sewered) can be high in suspended solids and BOD. If saved rinse water from an earlier final rinse is used, it may also be slightly alkaline. If an acid wash is used, it normally follows the rinse after the caustic wash, but it may be the only wash used as with bright beer tanks. If there is no CIP system, all of the wash and rinse solutions will be discharged directly to the sewer. In this case, an equalization tank may be required to prevent pH spikes in the effluent. (Further details of CIP systems appear in Chapter 13.)

27.2.3 Packaging

27.2.3.1 Waste Beer

The biggest source of waste beer in packaging is during bottle filling and the practice of “crown on foam.” After the beer is in the bottle but before the crown is put on, beer is made to foam and overflow the bottle in order to flush out air. The foam is generated by mechanically “knocking” the bottle or by “jetting” a tiny pressurized stream of hot water into the filled bottle or can. This practice generates a beer loss of around 1.5%⁴⁴ for bottles, but it can be as high as 3% or even 4%. Filling losses in canning range from 1% to 3% or more.⁴⁵ This beer usually goes to the floor and then to the sewer, but in some cases, it is successfully recovered, fermented further with enzymes, and distilled to recover the alcohol for fuel.¹¹

Beer losses in packaging and distribution include the following:³⁵

Packaging line startup losses
Warm beer discarded after cooling the fillers before a packaging run
Filler valve leakage
Bottle foaming after the jetter or knocker operation
Out-of-specification beer that is discarded
Spillage from cans at the bubble breaker and transfer
Crowning losses and can seaming losses
Rejected short fills and over-fills
Glass breakage on the packaging line and in pasteurizers
Beer lost in flash pasteurizers during water recirculation steps
Labeler and packer losses
Snifter losses when depressurizing containers before application of the crown or lid
Beer spillage at the racker head
Keg short fills and leakers
Product returned from the trade.

In most packaging plants, 80% of the beer losses can be attributed to jetter losses, seamer losses, under- and overfills, and bowl dumps. Goetz⁴⁵ discusses several methods to reduce packaging beer losses. Some over-foaming because of jetting is necessary to expel the oxygen from the headspace of the bottle, but over-foaming of about 1% of the contents should be more than sufficient to accomplish this.

Modern fillers have a feature to measure fill volumes of individual packages. These are related back to specific valves on the filler bowl to show which must be adjusted or require maintenance. Beer losses at the beginning of a packaging run can also be reduced by using cold deaerated water instead of beer to chill the filler bowl. If beer warms up during a packaging run because of unscheduled down time, bowl dumps can be avoided by utilizing a blowback system in order to return beer back to the brewing department.

It is obvious that beer losses vary widely from one brewery to another. It is estimated that beer losses in brewing vary from 2% to 5% and in packaging from 2% to 6%; average overall beer losses for an entire brewery can be as high as 5% to 7% or more.

27.2.3.2 Carbon Dioxide (CO₂) Emissions

Significant amounts of CO₂ are discharged to the atmosphere during packaging operations. Bottles, cans, and kegs are flushed with CO₂ to remove air. To remove the air more effectively, preevacuation of bottles with a vacuum is combined with CO₂ pressurization. The container is then pressurized with CO₂ to around 1.5 bar so that the beer will flow in by gravity without foaming. When beer flows into the bottle, can, or keg, the displaced CO₂ is exhausted to the atmosphere. These steps represent two to three volumes of CO₂ discharged for each volume of beer processed or around 15% of the CO₂ produced during fermentation. This CO₂ may be collected from fermentation and purified for reuse, otherwise it is purchased. In either case, it has a negligible effect on the carbon footprint, and attempts have not been made to recover it.

27.2.3.3 Cleaning-in-Place (CIP)

Equipment in the packaging department is generally cleaned like the equipment in the cellars with water rinses, caustic and/or acid washes, and sanitizing with chemicals or hot water. Effluents include the first water rinses, which contain smaller amounts of solids than those in brewhouses and cellars. Bright beer tanks may be cleaned with acid rather than caustic to avoid losing the CO₂ atmosphere in the tanks. Hot water around 80°C (180°F) may be used to sanitize fillers and pipelines. Kegs are most commonly cleaned with a caustic wash followed by an acid wash and, subsequently, steam sterilization. Discharges to municipal sewers may be subject to high temperature limitations.

27.2.3.4 Emissions of Volatile Organic Compounds (VOCs)

In packaging operations, the largest VOC emission is ethanol. Ethanol is introduced into the atmosphere primarily at the bottle and can fillers. It is present in the CO₂ gas that is vented as the containers are filled, and it evaporates from the beer that is spilled as the container moves from the filler to the crowner or seamer. The US EPA studied brewery emissions and reported on “emission factors” in 1996.⁴⁶ The bottle filling emission factor was 11 to 21 lb of ethanol/1,000 US bbl (4 to 8 kg/1,000 hL). For cans, the range was 11 to 17 lb ethanol/1,000 US bbl (4 to 7 kg/1,000 hL). Neither of these amounts has resulted in regulatory action, and there have been no attempts to capture these emissions.

27.2.3.5 Solid Waste Materials

Breweries, especially their packaging plants, produce large amounts of solid waste materials, much of which can be recycled. These materials include broken pallets, aluminum, cullet, corrugated paper, cartons, paper, fly ash, and spent granular activated carbon, If not recycled, disposal of these materials can be costly. Recycling, on the other hand, requires labor, sorting equipment, and space. Employee involvement is essential for a successful recycling program. In 1998, Asahi Breweries, in Japan, reported achieving 100% recycling of their wastes; the most difficult were plastics. Asahi attributed their success to thorough separation of all of their wastes and employee education!⁴⁷ A comprehensive review of the available literature on recycling is available from the National Soft Drink Association.⁴⁸

27.2.3.5.1 Aluminum

Aluminum waste results from under-filled aluminum cans and cans damaged in the seamer, on conveyors, or in the pasteurizer. Also, cans in damaged packages and over-aged canned products are rejected as waste. These cans are collected in dumpsters, brought to the dump area, and flattened in a can crusher. Glass, cartons, and plastic materials should be kept out of the can dumpsters or removed prior to crushing. Recycle rates of about 0.1 lb of aluminum per barrel packaged are not uncommon in large US breweries. Aluminum should seldom be a waste stream because its recycling is so easy and usually profitable.

27.2.3.5.2 Glass

In a brewery, both returnable and nonreturnable bottles generate cullet or broken glass that requires disposal. Bottles that are improperly filled or contain beer that does not meet specifications may be emptied by hand and recycled back to the rinser or bottle washer. Labor requirements for this process are very high, and this extra handling may damage the glass finish. Most breweries resort to crushing the glass and selling the cullet along with the cullet from other damaged bottles to bottle manufacturing companies. If not recycled, this glass must be disposed of as solid waste in landfills.

Worldwide, more than 50% of bottled beer is sold in returnable bottles. According to MillerCoors, returnable bottles have a lower carbon footprint than cans or plastic bottles.⁵ Use of returnable bottles requires a large investment in equipment, organization, and logistics. Brewery size therefore is a deciding factor in the economic feasibility of glass recycling (further details are in Chapter 16).

Development work is underway to produce a wood fiber paper beer bottle. Energy costs are a fraction of that for producing glass bottles and the wood fiber bottle would be biodegradable.⁴⁹

27.2.3.5.3 Paper, Cardboard

Large amounts of corrugated cardboard and other paper products used as packaging materials throughout the brewing process, must be disposed of. Rarely is it necessary to haul waste paper to a landfill as recycling is so easy. Once the system is in place, management stresses its importance!

27.2.4 Utilities

Efficient use of energy impacts the triple bottom line of profit, people, and the planet. All three benefit when energy is used efficiently with minimal impact on the environment. The brewing process is an intense consumer of heat, electricity, and water. Progress continues, not only in finding ways to save energy and water by using them more efficiently but by replacing traditional sources of heat and electricity with sustainable sources that reduce greenhouse gas emissions (carbon footprint). Windmills and solar panels are being used as sources for electricity. Solar panels are also being used to produce process heat and steam that is generated by burning biogas from waste treatment systems.

Process improvements to boost brewhouse efficiency and reduce beer losses have an important effect on reducing energy usage. In addition, these improvements decrease raw material costs and waste disposal costs per hectoliter of final product.

27.2.4.1 Water

Beers are mostly water, ranging from 88% or slightly lower to more than 99% water. The traditional yardstick for efficient water use in beer production is volume of water used per volume of beer produced. For example, hectoliters of water used to produce 1 hL of beer—or barrels water per barrel beer. For the beer itself, slightly less than 1 hL of water is in 1 hL of packaged beer.

Water use is a concern for several reasons. One is economics. Every hectoliter of water has a cost that is paid to the water utility or a cost of operating the brewery’s own wells or other captive sources. In the case of municipal supply, an additional charge per hectoliter of water purchased is added for wastewater treatment of that water when it is returned as an effluent back to the municipal waste treatment plant. The wastewater charge is often higher than the cost of the water itself. The water that does become part of the beer may be exempt from the wastewater charge. Some examples of these costs are shown in Table 27.4.⁵⁰

Table 27.4 Water and Wastewater Costs in Some US Cities, 2013

City	Water Cost ($/1,000 gal)	Wastewater Cost ^a ($/1,000 gal)
Chicago	2.89	2.66
Boston	6.86	8.56
Seattle	6.87	15.61
Los Angeles	7.26	4.82

a Surcharges for high strength wastewater are not included.

Efficient use of water is also a goal prompted by a sense of social responsibility to preserve natural resources. Sometimes, more efficient water use is forced because of a limited water supply. In the 1970s, a usage of 10 hL water/hL beer was considered average, but it was as high as 30 hL/hL in some breweries. Usages of 6 hL/hL did occur at that time, but they were the exception.⁵¹ Today, brewers are reporting water usages approaching 3 hL/hL of beer^{4, 5} and as low as 2.5 hL/hL.⁵²

Reducing water usage requires attention in many areas. Large overall reductions will be the sum of many small reductions, some of which are listed here:

Water leaving in the spent grain
Equipment rinses
CIP solutions
CIP rinsing
Housecleaning
Carbon filter backwash
Boiler makeup
Boiler blowdown
Water softener regeneration
Cooling tower losses
Water-cooled condensers
CO₂ purification
Bottle and can rinsers
Bottle washers
Pasteurizer
Keg cleaning
Water hose stations for wash downs.

27.2.4.2 Thermal Energy

Brewing is an energy-intensive process, both in terms of thermal energy and electrical energy. Thermal energy used in beer production is reported as kWh/hL (Btu/bbl). The amounts used in major areas of the brewery are estimated as follows:⁵³

Thermal energy usage in brewing
Brewhouse	30% to 60%
Packaging	20% to 30%
Space heating	< 10%
Utilities	15% to 20%

Thermal energy is traditionally supplied using steam boilers that burn coal, fuel oil, or natural gas. Environmental effects are limited in part by government regulations, but breweries often go beyond the regulatory standards to reduce fuel consumption and reduce their carbon footprint.

Besides VOCs from the brewing process itself, the most serious emissions to the atmosphere are from the combustion of fuels to produce process heat. Emissions from fuel combustion are regulated and include allowable levels for nitrogen oxides, carbon monoxide, ozone, lead, and sulfur. These emissions—pollutants—have been linked to respiratory problems in humans and adverse effects to the environment. The World Health Organization (WHO) issued guidelines for human exposure to these materials beginning in 1987, and the guidelines are updated periodically.⁵⁴ The legislation controlling emissions of these pollutants in many countries is influenced by the WHO guidelines, the U.S. Clean Air Amendment of 1990, and the European Union and Germany’s Technische Anleitung zur Reinhaltung der Luft.

There is a growing sense of responsibility in the brewing industry, separate from regulatory mandates, to minimize the carbon footprint and to improve the sustainability of operations. Emissions from steam boilers have been reduced with cleaner fuels, improved burners, and better boiler maintenance (air/fuel mixtures). Treatment of the flue gas to remove pollutants is also possible and often mandated.

Sustainability implies operating the boiler at maximum efficiency. Boiler controls must be tuned and air flow must be sufficient—more than the theoretical amount required—to ensure that 100% of the fuel fed to the boiler is burned. It also means not overfeeding excess combustion air. Excess air is not involved in combustion but only passes through the boiler being heated on its way to return to the atmosphere. Proper daily care of the boiler, in terms of water treatment, blowdown, and soot blowing, is essential for both safety and efficiency. Key is preventing buildup of scale and thus keeping the heat transfer high and preventing increases in boiler stack temperatures.

Returning the condensate from the plant back to the boiler has a significant impact on efficiency and sustainability. Less cold makeup water must be heated and treated with chemicals. Reusing the condensate also means less liquid effluent going into the sewer.

Boiler efficiency is improved if a boiler economizer (heat exchanger) is used to recover heat from the hot combustion flue gas. Boiler economizers usually heat the boiler feed water. They can also be used to preheat the boiler combustion air. These actions, usually undertaken to improve boiler efficiency, have a rapid economic payback as well as reducing the carbon footprint of the brewery.

Many breweries have reduced their fossil fuel use with solar energy. Photovoltaic systems use solar cells to convert sunlight directly into electricity. Concentrating solar power systems use a geometric arrangement of mirrors or reflectors to concentrate sunlight from a large area into a small space where it can heat process water and even produce steam. These systems can even produce superheated steam to run turbines/generators that produce electricity and process steam.⁵⁵

Replacement of some of the brewery’s fossil fuel-derived thermal energy with renewable sources along with proper maintenance and operation of the equipment contributes to greater efficiency and cost savings. These efforts to reduce the brewery’s carbon footprint and increase its sustainability are very important in advertising and customer relations. Consumers are aware of and make purchasing decisions based on the company’s responsible business activities.

27.2.4.3 Electricity

Demand for electricity will continue to grow worldwide, with a predicted increase of almost 70% by 2040 compared to 2012. Concern about the greenhouse gas emissions and the environmental effects of burning fossil fuels, primarily oil and coal, has increased interest in natural gas, which produces less CO₂; there is even greater interest in renewable fuels such as solar energy, wind power, and hydroelectric energy. Data from the U.S. Energy Information Administration,⁵⁶ shown in Table 27.5, predicts that electrical power generation from all renewable and nonrenewable sources, except oil, will continue to increase. Solar, wind, and geothermal are expected to have the greatest growth rates, accounting for 22% of the total in 2012 and increasing to a predicted 29% by 2040.

Table 27.5 Changes in Resources Used for Electrical Energy Production

Estimated Electricity Production from Resources (10⁹ kWh/year)			Change (%)
Resources	2012	2040	2012–2040
Petroleum	1.06	0.56	47
Nuclear	2.34	4.50	92
Natural gas	4.83	10.14	110
Coal	8.60	10.62	23
Geothermal	0.07	0.40	480
Solar	0.10	0.96	836
Wind	0.52	2.45	371
Hydropower	3.65	5.57	53
Other renewables	0.39	1.25	219
Total	21.56	36.45	69%

Many breweries use renewable electrical energy sources to further reduce their carbon footprint and to reduce costs. Several breweries produce biomethane in their waste treatment plants and burn this gas to generate high-pressure steam that operates turbines to produce electricity. The lower pressure steam leaving the turbines is used for heating processes in the brewery. The burning of biomass, such as waste wood, paper, and cardboard, is also used. Combustion of brewer’s spent grains has been evaluated, but this has not been shown feasible due to the high moisture content.

Breweries in many countries are also using windmills and solar panels to generate electricity. In the United States, MillerCoors installed 10,000 solar panels at their brewery in Irwindale, CA.⁵ These panels generate 3.2 megawatts, enough electricity to produce 7 million cases each year (596 hL/year, 508,000 US bbl/year). Many craft breweries in the United States, notably Sierra Nevada,⁴ are using solar power. And Heineken⁵⁷ is using solar power at several of their breweries worldwide as part of their global sustainability strategy.

Electrical energy used in beer production has been reported as kWh/hL, the range being 8 to 12 kWh/hL of beer produced (9.4 to 14 kWh/ US bbl), and the areas of use are shown below.⁵³

Electrical Energy Usage in Brewing

Refrigeration	32%
Motors	46%
Lighting	7%
Other	15%

Electric motors are used extensively in the brewery for pumps, blowers, conveyors, compressors, and so forth. Premium efficiency motors and variable frequency drives provide major opportunities for reducing electrical energy consumption. Motor efficiency standards (premium, standard, super, etc.) have been defined by the National Electrical Manufacturers Association (NEMA) as well as the International Electrotechnical Commission (IEC) and similar organizations around the world. Most countries have established minimum energy performance standards (MEPS) for motors. High-efficiency motors result in reduced electricity consumption and, in turn, reduced emissions from electrical power plants and the possible elimination of the need to expand electric power-generating capacity.

Variable speed drives are very effective in reducing electrical power usage. When equipment such as pumps, blowers, and compressors does not need to run at full speed, a throttling valve on the pump discharge or a damper on the blower discharge can be used to obtain the desired lower flow rate. The valve or damper creates more pressure drop (friction) in the line to dissipate the unneeded energy provided by the pump or blower running at full speed. Variable frequency drives change the hertz (cycles per second) of the electric power supplied to the motor. This lowers the rpm of the pump or blower to provide the desired flow. Using a variable speed drive reduces the power usage by as much as 60% with operation at 40% of full speed.⁵⁸

27.2.4.4 Refrigeration

Refrigeration is the largest user of electrical energy during the brewing process, accounting for 30% to 40% of the total electrical energy used. Cooling towers provide sufficient cooling for some cooling loads, but the temperature of the cooled water depends on the weather and can only approach the current dew point temperature within a few degrees. To meet brewery cooling requirements, chillers (vapor recompression systems), with compressors powered by electric motors, are needed to lower the cooling medium temperature to −4°C (25°F). For large cooling loads, ammonia refrigeration systems, either direct or with a secondary refrigerant, are often used.

The efficiency of a vapor recompression refrigeration system is related to the difference between the low refrigerant temperature and the high refrigerant temperature at which it operates. This means, for example, that a 52-ton chiller cooling a glycol solution to 7°C (45°F) would have to be derated to approximately 35 tons of refrigeration if it were used to cool the glycol to −4°C (25°F). Because of the lower cooling temperature, the chiller would be using 52 tons of power but only providing 35 tons of refrigeration. This also means that chiller efficiencies will be higher in the winter than in the summer because the high refrigerant temperature is the outdoor air temperature (or the temperature of the water from the cooling tower if a water-cooled condenser is used).

Operating at the warmest possible chiller refrigeration temperature will give the highest chiller efficiency. It is estimated that increasing the evaporator temperature 1°C will save 3% in electricity costs.⁵⁹ There are brewery situations where two refrigeration systems, in a cascade arrangement, are used because of large the very low temperatures required. This happens in breweries that liquefy the CO₂ collected from their fermenters. The CO₂ is liquefied around 17 bar (245 psi) and −24°C (−11°F). This requires a refrigerant—usually ammonia—that can cool at −30°C (−20°F).

Refrigeration efficiency can be increased by making ice at night, when the outdoor temperatures are lowest. The stored ice provides cooling during the day when warmer outdoor temperatures mean lower refrigeration efficiencies.

Heat is removed in vapor recompression condensers. Air as warm as 85°C (185°F) is exhausted to the atmosphere as waste heat. An economical and environmentally friendly practice is to recover this heat for other uses in the process such as heating water.

The load on the refrigeration system can also be reduced with proper insulation of the cold parts of the equipment, the distribution system itself, and the pipelines, equipment, and tanks where cold liquids are stored. The correct insulation type and thickness determines heat loss and the need for more refrigeration. Proper sealing of the insulation prevents condensation and the accumulation of moisture within the insulation that would greatly reduce its insulating ability.

Refrigerants in vapor recompression refrigeration systems have traditionally been ammonia and chlorinated fluorocarbons (CFCs). Commonly used CFCs have been found to have serious environmental impacts, such as

High ozone depletion potential (ODP)
High global warming potential (GWP)
High atmospheric half-life.

For these reasons, CFCs are prohibited by the Montreal Protocol. By 2040, new virgin production of all currently known CFCs is to be stopped worldwide. Accepted refrigerants today are HCFC-123, HFC-410a, HFC-134a, and refrigerant R-513A. Freon 502 was previously used to condense CO₂, but now R404A or R408A is used. Ammonia (along with CO₂, propane, and butane) is referred to as a natural refrigerant because its ODP and GWP are both zero. Ammonia’s thermodynamic properties make it the ideal refrigerant over a wide range of temperatures in industrial refrigeration systems. In cascade systems for very low temperatures, ammonia may be used in the first stage, with CO₂ in the second stage.

27.2.4.5 Compressed Air

Compressed air is used throughout the brewery for operating valves, conveying grain, aiding with container and closure transport in packaging, drying wet containers in packaging, and operating tools and pumps. Although it is useful in many applications, compressed air is a very expensive utility and receives much attention in sustainability programs. When air or any gas is compressed, its temperature increases. This heat is usually discharged into the atmosphere in part because of air compressor temperature limitations. So much heat is exhausted that the energy increase of the compressed air represents only 12% to 15% of the work performed by the compressor motor.⁶⁰ For this reason, compressed air should always be used judiciously.

Air should always be compressed to the lowest possible pressure that will satisfy the process. Using 6 bar air when only 2 bar air is needed wastes energy and deviates from the goal of sustainability. Control valve actuators, positioners, and other machinery components require compressed air at 5 to 6 bar. It may also be necessary to dry this air, either with a refrigerated dryer or a desiccant air dryer system, which adds to the equipment and operating costs. Normally these are small volume uses, but they determine the pressure at which the compressors are operated.

Air-powered tools and pumps require large volumes of air and should only be used if there is a definite reason not to use electricity. It may be possible to operate these at a pressure lower than the compressor pressure, but there is normally only one compressed air distribution system through the plant. An exception is the conveying of grains and spent grain. These should be conveyed with low-pressure, high-volume blowers that are designed for the specific grain conveying application.

Air leaks are a common and a very expensive source of inefficiency in a compressed air system. They have been known to account for as much as 40% of the compressed air being used. Although difficult to locate, especially when equipment is running, the time spent finding and fixing these leaks will have a significant economic return.

27.2.4.6 CO₂—A Brewery Utility

Carbon dioxide is used throughout the brewery, in small part to carbonate the beer but in larger part to prevent or correct oxygen pickup in transfers, filtration, and packaging. In some breweries, there is enough CO₂ generated in fermentation to supply all of the brewery’s CO₂ needs if it is collected, purified, and stored for reuse. Normally, CO₂ is stored for reuse as a liquid at a pressure of 11 bar and near −24°C (240 psig, −11°F). Before being used, the liquid CO₂ must be vaporized and that requires heat. Electricity, hot water, or steam can be used, but other methods have been employed in sustainability programs to operate more efficiently. The evaporating CO₂ is being used in heat exchangers to precool glycol refrigerants on the way back from the process to the chiller or ammonia system. Atmospheric vaporizers (finned tube heat exchangers that take heat from atmospheric air) have also been used to avoid using heat energy to vaporize the CO₂, but the process cooling benefit is lost to the atmosphere.

Energy savings have been demonstrated for collection systems where 73% to 83% of the collected CO₂ was purified and compressed and then reused without liquefaction and subsequent vaporization, saving a large portion of those inherent costs.⁶¹

If CO₂ is collected for reuse in the brewery, the purification process generates a liquid effluent and possibly a gaseous emission. Water-soluble fermentation by-products are first removed in a water scrubber, and the scrubber overflow is discharged to the sewer. A second step removes other components by adsorption onto activated carbon. When the activated carbon becomes saturated with these components, it is regenerated with steam or hot air, which is exhausted into the atmosphere. All of these fermentation by-products, which include volatile organic compounds, would be vented to the atmosphere if the CO₂ were not collected. As pointed out earlier, the carbon footprint of this vented CO₂ may be negligible or perhaps negative.

27.2.5 Distribution

Transporting raw materials to the brewery and shipping the products to the customer contributes to the brewery’s carbon footprint. A study at the University of Colorado in 2009⁶² compared the carbon footprint of a 10,000 US bbl (micro) brewery with that of a 1,000,000 US bbl (regional) brewery. The comparison, shown in Table 27.6, indicates that transportation’s contribution to the carbon footprint is more significant for a larger regional brewery. For raw material and product transport, the carbon footprint was 3.6% of the microbrewery’s total and 9.3% of the regional brewery’s total.

Table 27.6 Carbon Footprint for Transportation of Raw Materials and Products

Carbon Footprint	Microbrewery (10,000 US bbl/year)	Regional Brewery (1,000,000 US bbl/year)
% of total	3.6	9.3
Kg CO₂e/hL	1.05	2.76
Lb CO₂e/US bbl	2.72	7.13

Breweries are reducing their transportation carbon footprint as well as their transportation costs by:

Using rail or a combination of rail and trucks instead of only trucks for long distances.
Expanding capacity with new breweries close to customers.
Filling trucks with products leaving the brewery and bringing back raw materials on the return trip.
Using the most fuel-efficient, streamlined trucks commercially available.
Packaging in cans rather than one-way bottles to reduce weight.

27.2.6 Buildings, Offices

Breweries around the world are achieving LEED certification for energy-efficient building design. LEED stands for Leadership in Energy and Environmental Design. It is a global organization with projects in 160 countries. Buildings in the United States are responsible for 73% of electricity consumption and 38% of all CO₂ emissions.⁶⁰ LEED certification provides independent verification of a building or neighborhood’s green features, allowing for the design, construction, operations, and maintenance of resource-efficient, high-performing, healthy, cost-effective buildings. LEED is the triple bottom line in action, benefiting people, planet, and profit.

LEED uses a rating system (Certified, Silver, Gold, and Platinum) devised by the U.S.Green Building Council (USGBC) to evaluate the environmental performance of a building. LEED buildings with Gold ratings consume 25% less energy and generate 34% less greenhouse gas.⁶³

Breweries with LEED-certified buildings enjoy the cost savings of greater efficiency and, in addition, they can use it as evidence of their commitment to working for a greener planet.

27.3 BREWERY WASTEWATER TREATMENT

27.3.1 Introduction

Brewery wastewater is relatively simple and highly biodegradable. A complicating factor, however, is that wastewater volumes, pH, and concentrations of included solids are significant and they vary constantly. To develop a good characterization of the wastewater, the flow rates and the concentrations must be measured and sampled simultaneously during an extended period of time to produce a representative composite.

Suspended solids in the effluent consist of organic matter such as grain, trub, yeast, and label pulp as well as inorganic materials such as filter aids, silica gel, broken glass, and bottle caps. Dissolved solids are mainly from beer, wort, and cleaning and sanitizing solutions. Typically, the BOD is used to index the concentration of biodegradable organics in brewery waste streams. BOD determinations are cumbersome and not very accurate. However, they have historically been used to assess the pollution potential of wastewaters and have become the basis for design and operation of wastewater treatment plants.

Wastewater from a brewery may be discharged several ways: (a) directly into a river or ocean; (b) directly into a municipal sewer system; (c) into a river or municipal system after pretreatment; and (d) into the brewery’s own wastewater treatment plant.

Discharges into public waters are often subject to limitations in organic load, suspended solids, pH, temperature, and chlorine. The maximum allowable BOD limit for discharge of effluents into public waters near densely populated areas can be 20 to 30 µg/L (ppm) and may be as low as 10 µg/L (ppm). Surcharges for discharge into municipal systems are based on the average volumetric load, on peak discharge rates, average BOD load (0.39 $/lb BOD or 0.64 €/kg was an average in the United States in 2014), and average suspended solids load (0.33 $/lb suspended solids or 0.55 €/kg was an average in the United States in 2014).⁶⁴

Some breweries have been required to contribute to the construction and operating costs of municipal treatment facilities. It is also becoming common for large breweries to construct their own complete wastewater treatment facilities or to pretreat their effluent. The high costs that are often required for waste treatment offer brewers an additional incentive to eliminate unnecessary wastes and to optimize the reuse of effluents.

27.3.2 Wastewater Volumes and Concentrations

Both dissolved and undissolved materials in the effluent are of concern for waste treatment. The undissolved or insoluble materials are measured in mg/L, dry basis, and referred to as total suspended solids (TSS). The chemical strength of wastewater is referred to as COD (chemical oxygen demand) and BOD (biochemical oxygen demand), both expressed as mg/L. Both are a measure of the amount of oxygen needed to oxidize the organic material, soluble and insoluble, using an oxidizing agent. In the case of BOD, the analysis uses bacterial breakdown of the organic component and “BOD₅” is milligrams of oxygen consumed per liter of wastewater by the bacteria in 5 days at 20°C. BOD levels in various waters are as shown as follows.^{64, 65}

Biochemical Oxygen Demand of Various Waters

Water Sample	BOD₅, mg/L
Clean river	<1
Moderately polluted river	2 to 8
Tertiary treated municipal sewage	20
Untreated sewage	200 to 600
Brewery wastewater	1,200 to 3,600

The considerable variation in strength and amount of BOD and suspended solids in brewery effluents depends on waste management and on the degree of recycling that is applied by the particular brewery. Table 27.7 shows levels of BOD and suspended solids that might be expected from a large brewery.¹⁰

Table 27.7 Generation of BOD and Suspended Solids in a Large Brewery

Brewery Source		Weight Generated/Volume Packaged
BOD		Suspended Solids
	kg/hL	lb/US bbl	kg/hL	lb/US bbl
Lauter tun, rinse, and drain	0.10	0.26	0.04	0.10
Trub and wort losses	0.04	0.11	0.02	0.06
Other brewhouse: losses, CIP	0.03	0.08	0.02	0.05
Press liquor (NA if grains sold wet)	0.18	0.46	0.09	0.22
Waste from yeast handling	0.03	0.08	0.02	0.05
Spent filter materials (if all is sewered)	0.06	0.16	0.20	0.52
Fermenting, cellaring waste	0.17	0.44	0.04	0.10
Packaging waste	0.28	0.72	0.03	0.08
Total	0.89	2.31	0.46	1.18

The average BOD discharged reported for 12 large North American breweries ranged from 0.37 to 1.4 kg/hL packaged (0.96 to 3.7 lb/US bbl) with an average of 0.81 kg/hL packaged (2.1 lb BOD/US bbl).¹⁰ For German breweries with careful waste management, Rosenwinkel and Seyfried⁶⁶ reported an average of 0.60 kg/hL packaged (1.55 lb/bbl) with a range of 0.39 to 1.06 kg/hL packaged (0.9 to 3.03 lb/US bbl). Suspended solids discharge from seven North American breweries averaged 0.35 kg/hl packaged (0.9 lb/US bbl) with a range of 0.12 to 0.85 kg/hL packaged (0.3 to 2.2 lb/US bbl). A typical split of discharges from parts of the brewing process is given in Table 27.7.

Concentrations of BOD and suspended solids vary considerably, depending on where samples are taken and how much water is used for flushing and rinsing and therefore dilution. Many brewers have made concerted efforts to reduce water usage to lower costs for water, water treatment chemicals, and wastewater treatment surcharges based on flow. Not all wastewater requires treatment. Noncontact cooling water and rinse water for nonreturnable bottles and cans, for example, are relatively clean and may be discharged directly into a river or storm sewer depending on temperature and chlorine limitations.

Volumes of wastewater that are discharged to a sanitary sewer or treatment plant from large modern breweries are in the range of 2.5 to 6 hL/hL packaged. Smaller breweries, older breweries, and breweries located in hot climates usually have higher volumetric discharges per volume of production.

Most large breweries require some degree of wastewater pretreatment at the plant before their effluent is discharged to public waters or to a municipal treatment system. In many cases, mere pretreatment might be sufficient to meet local regulations. Pretreatment is conducted by physical, chemical, or biological methods, or by a combination of these.

27.3.3 Physical Treatment

Physical pretreatment methods for breweries includes removal of coarse suspended solids, flotation, and sedimentation. The first process step in pretreatment is usually screening in order to remove coarse, suspended solids such as labels, caps, glass fragments, plastic, and grain particles.

After screening, the effluent is usually passed through a rectangular grit removal chamber where stones, sand, and other objects fall to the bottom. A grit chamber may have a continuously operated scraper mechanism to remove these solids.

Natural sedimentation and flotation, with or without the addition of additives to promote coagulation, is used to remove smaller particles that coagulate and either settle to the bottom or float to the top. Dissolved air flotation is an effective pretreatment method. In this process, air is dissolved in water under pressure and comes out of solution as tiny bubbles to which particles attach.

Major problems associated with treating brewing effluents include the highly variable nature of the flow, the BOD concentration, and the pH. The most efficient action that can be taken to make the effluent more uniform is the installation of a buffer or equalization tank that allows the highs and lows to blend and maintains the contents well mixed.⁶⁷ Aeration or oxygenation may be required to prevent microbial production of hydrogen sulfide odors.⁶⁸ Some breweries use a separate tank (a “calamity” tank) to collect their alkaline CIP effluents, bottle washer effluents, spills, and unusual spike discharges. These abnormal effluents can then be treated separately or gradually blended into the main discharge stream to avoid spikes that could upset the treatment plant downstream. The grit chamber after screening can also serve as a mixing chamber for pH control as well as a preaeration unit to prevent anaerobic conditions.⁶⁹

27.3.4 Chemical Treatment

Organisms in digesters are sensitive to pH. Effluent feeds to a digester need to fall between pH 6 and 9 to protect the organisms. Chemical treatment is used in a number of breweries to neutralize alkaline effluents from CIP systems and bottle washers with waste CO₂. Neutralization with sulfuric or hydrochloric acids is usually not recommended because of their corrosive nature as well as limitations on sulfate and chloride discharges.⁷⁰

To obtain larger flocs in sedimentation and flotation tanks, flocculation aids such as alum, lime, or ferric chloride are used to increase removal of colloidal matter. This action decreases the load on downstream waste processing systems. Lunney⁷¹ reported removal of 60% of the suspended solids and 45% of the COD, whereas Hughes⁷² achieved removal of 95% of the suspended solids and 6% of the COD.

27.3.5 Biological Treatment

Biological treatment systems include aerobic systems with a short residence time and anaerobic systems. After the initial physical and chemical pretreatment, the wastewater is treated either aerobically or anaerobically. Sometimes, aerobic treatment is followed by anaerobic treatment.

27.3.5.1 Aerobic Treatment Systems

Aerobic waste treatment systems use a mixture of microorganisms, mainly bacteria, to metabolize the organic material in the wastewater in the presence of air (oxygen). Aerobic treatment yields more microorganisms (sludge) and coproducts such as water (H₂O), CO₂, and ammonia (NH₃). There are two general options for aerobic digester design:

The activated sludge process
Biofilm processes.

An aerobic system can be as simple as an aerated and agitated equalization tank (an activated sludge process) or it can be a tank or tower with support media such as gravel for biological growth, or wood chips, or plastic pieces (biofilm process). A clarifier is required downstream to separate the sludge from the treated water.

27.3.5.1.1 Activated Sludge Processes

After the initial chemical and physical pretreatment, the waste stream is fed into an aerated and agitated tank that contains biomass—a mixture of organisms, mainly bacteria. BOD may be reduced up to 60% to 70% as the biomass converts the organics in the waste stream into water, carbon dioxide, and more biomass. After a residence time of hours in the aerated tank, the mixture overflows into a settling tank or secondary clarifier to allow the sludge (biomass) to separate from the cleaned water. Sludge is recycled into the aeration tank, and the water is discharged. Depending on the process, liquid residence of the whole process may be several hours to several days. This may be all the treatment that is required, or this reduction may be part of a full treatment process. Reviews of aerobic-activated sludge systems have been written by Leeder,⁷³ Miller Brewing,⁷⁴ and Barrett and Hayden.⁷⁵

A fluid bed system is probably the most efficient biological growth system as a very high density of biomass can be kept in suspension. In a fluid bed system small “bioparticles” of sand, activated carbon, plastic pieces, and so forth are kept in suspension by upward flowing wastewater and/or air in the reactor. Another advantage of fluid bed systems is that a settling tank is normally not required for sludge removal. The excess sludge is recovered by removing some of the sludge-laden particles from the tank, separating the excess sludge followed by returning the particles to the reactor.⁷³

27.3.5.1.2 Biofilm Processes

Other aerobic systems use the attached growth or biofilm process. In these systems, the microorganisms grow on fixed surfaces. The surface becomes covered with a biofilm and, when water containing organic compounds flows over the biofilm, the organisms digest these compounds. The media can be gravel or plastic solids in a trickling filter of wood or plastic chips in a biotower. As the wastewater flows over the medium that is covered with biofilm, pollutants are consumed in the presence of air. The wastewater is usually recycled to obtain sufficient flow for uniform wetting. Unpleasant odors may be a problem with these systems.⁷³

Another approach is the rotating biocontactor. This process uses a series of plastic discs mounted on a horizontal shaft with the lower portion of the discs below the surface of the wastewater. The discs are covered with the aerobic medium or biofilm that removes the pollutants from the wastewater.⁷⁶ These biofilm processes all provide contact with oxygen to maintain aerobic conditions. They all also produce large amounts of excess activated sludge that must be removed and disposed of. Disposal may be in landfill or the sludge may be further processed for fertilizer.⁷⁷

Another novel aerobic system requiring only a small land area is the deep shaft aerator system, which is successfully operating at a Molson brewery in Canada.⁷⁸ In this process, wastewater is in contact with biomass and compressed air in an underground shaft 152 m deep that promotes a high rate of biological oxidation as the mixture flows upward, reducing pressure and releasing air (oxygen) from solution.

27.3.5.2 Anaerobic Treatment Systems

Anaerobic digestion is a complex process in which a large variety of bacteria break down organic materials and convert them into methane and CO₂ in a ratio of about 3:1. The bacteria are generally grouped into three basic types.⁷⁹ First are the acid-forming bacteria called acidogens. They provide extracellular enzymes that hydrolyze soluble and insoluble complex organics and convert the hydrolysis products into fatty acids, alcohols, CO₂, ammonia, and hydrogen. The second group, called acetogens, transforms the resulting products into acetic acid, hydrogen, and CO₂. The third group consists of methanogens, which convert acetic acid, hydrogen, alcohols, and some of the CO₂ into methane. The methanogens are sensitive to cleaning and sanitizing chemicals such as quaternary ammonium compounds, chlorine dioxide, hypochlorite, peracetic acid, and ethylenediaminetetraacetic acid (EDTA).

Anaerobic systems have found a wide acceptance as biological treatment systems for brewery effluents. Advantages of the anaerobic system over aerobic treatment mentioned in the literature are⁸⁰:

Low energy consumption, especially in hot climates
Net producer of methane gas, which can be used as a fuel
70% less space requirements
Less nutrient requirements
Up to 90% less sludge production
Lower capital cost because of a higher loading rate.

Several potential disadvantages for anaerobic systems have also been discussed,⁶⁷ including:

The slow growth rate of methane-forming bacteria
Anaerobic systems are more sensitive to temperature and pH shock discharges than aerobic systems and generally require a balancing tank.
BOD removal efficiencies vary and may be insufficient so additional aerobic treatment may be required.
In addition to 70% to 80% methane, the biogas is saturated with water and contains 20% to 30% CO₂ and 1,000 to 2,000 µg /l (ppm) hydrogen sulfide (H₂S), which may cause corrosion problems in steam boilers.

In general, anaerobic treatment systems work well for effluents with high BOD concentrations. To reduce costs, it is desirable to have a separate collection system for high-strength brewery effluents destined for anaerobic treatment. If complete treatment of all waste is desired, the low-strength effluents should be treated aerobically, along with the effluent from the anaerobic system.

The biogas generated in an anaerobic digester consists primarily of methane and CO₂ with trace amounts of water vapor, ammonia, hydrogen, and hydrogen sulfide. Crude biogas can be burned to produce steam that can drive turbines to generate electricity and provide process heating in the plant. The biogas is usually pretreated to at least remove enough of the hydrogen sulfide to prevent corrosion problems and bad odors when burned.

27.3.5.2.1 Upflow Anaerobic Sludge Blanket (UASB)

The most commonly employed anaerobic system in breweries is the upflow anaerobic sludge blanket (UASB) system developed at Wageningen University in the Netherlands. In this system, the influent wastewater is uniformly distributed over the bottom of the reactor and it then flows upward through a thick, dense bed of active anaerobic sludge. Gas, liquid, and sludge are separated from each other above the bed.⁸¹ Most of the sludge returns to the bed, while a portion may be diverted to the surplus sludge tank. Difficulties with this system have been excessive H₂S formation and the loss of solids from the sludge bed resulting from shock loads.

27.3.5.2.2 Other Designs

In a fluidized bed reactor, the wastewater flows upward through the media that is covered with a biofilm of anaerobic organisms. The media can be sand, and the upward liquid flow fluidizes the media and keeps it in suspension. The biomass growing on the media converts the pollutants into methane and CO₂.

Another design for an anaerobic digester is a packed column in which the biomass is attached to plastic media. A system of this type with a downflow mode has been successfully applied to treatment of distillery wastes.⁸²

A good solution to anaerobic digester problems such as excessive H₂S formation and the effects of shock loads has been the design of a two-stage process. The first stage is a stirred tank reactor where acid formation takes place and the second stage is a UASB reactor, where methane formation takes place.⁸³ This two-stage system was found to be quite stable and COD removal rates of 70% and higher were obtained at temperatures as low as 15°C to 20°C. A two-stage system has been employed for the treatment of a yeast plant effluent, with a fluidized bed reactor for each stage⁸⁴ As the biogas from this system contains 1% to 2% H₂S, it is highly corrosive and reactors are made of glass fiber-reinforced polyester with a polyvinyl chloride (PVC) lining. Problems with H₂S have been solved by removal of H₂S from biogas with silica gel adsorption⁸⁵ or by the addition of iron to form iron sulfide.

27.3.5.3 Sludge Treatment, Disposal, and Utilization

One of the more expensive steps in wastewater treatment is the handling, including dewatering, of excess sludge. Dewatering the sludge is important to control the costs of drying, incinerating, or transporting the sludge to a landfill. This is especially true for aerobic treatment systems where large quantities of sludge are produced. A high solids concentration is required to reduce transportation costs or to keep fuel costs down if sludge is dried or incinerated. Landfill requirements sometimes also dictate maximum allowable moisture levels.

Excess sludge that is collected from settling tanks generally contains 1% to 2% solids. This sludge can be held in consolidation tanks for an additional two to three days to increase the solids concentration to about 4%.⁷³ Solids can also be concentrated to about 4% using dissolved air flotation⁸⁶ or with centrifuges. Sludge, squeezed from the plastic sponges that are laden with biomass in some fluid bed systems, has solids concentrations up to 6%.⁷³

Further dewatering may be carried out by means of vacuum or pressure horizontal belt filters, by rotary vacuum filters, by plate and frame or recessed plate filter presses, or by centrifuges. A precoat of fly ash or diatomaceous earth is often used in filter presses to prevent cloth blinding. Overall dewatering rates may be enhanced considerably by using chemical coagulants such as alum, lime, ferric chloride, and body feed such as fly ash, diatomaceous earth, or paper fiber.⁸⁷

Lime contributes to the value of the sludge if the product is to be utilized as fertilizer. Fly ash and diatomaceous earth are often brewery by-products that need to be disposed of anyway, whereas ferric chloride may sometimes be obtained inexpensively as pickle liquor, which is a by-product from the metal plating industry.

By adding about 25% lime, 10% ferric chloride, and 10% fly ash based on sludge solids, sludge from an aerobic treatment plant can be consistently dewatered to 35% to 50% solids in a filter press. Sludge from the deep shaft process, which has 3% to 5% solids after flotation, can be dewatered to 16% to 17% solids by using a belt press.⁷⁸ Sludge from most breweries is hauled to a landfill, but some brewers have found the product to be useful as fertilizer or as animal feed.

27.3.6 Land Application of Brewery Effluents

Some large Anheuser-Busch breweries in the United States as well as others use the system of land application of selected brewery effluents. The Anheuser-Busch land treatment systems⁸⁸ were designed for an annual average fluid loading of 0.12 in./day, a suspended solids loading of 43 lb/acre/day, and a nitrogen loading of 585 lb N/acre/year. The land application system was combined with a year-round turf operation to ensure intensive management and utilization of nutrients.

The high-strength segregated waste streams at Anheuser-Busch are collected in aboveground steel tanks with a combined hold-up capacity of 3.6 days. The tanks must be aerated to minimize odor problems. The pH is adjusted to an appropriate level for the particular soil. The effluents have to be passed through a screen to prevent coarse suspended matter from plugging up the rotating irrigation systems. The soil requires extensive preparation to be able to maintain a minimum water table of 3 feet over the entire area. Regulatory monitoring and effluent sampling requirements are extensive. Turf grass may be harvested two to three times per year.

27.3.7 Production of Single-cell Protein and Electricity from Brewery Effluents

In aerobic and anaerobic waste treatment systems, the microorganisms used to break down organic matter consist of a wide variety of different bacteria, protozoa, and rotifers. One of the products of feeding waste to these organisms is the production of more organisms (sludge or biomass). The excess that cannot be reused is waste that must be disposed of. There has been significant research to identify other organisms such as yeast species and filamentous fungi that can also successfully reduce the BOD in brewery effluents. This opens the possibility of producing a biomass that may be more acceptable to regulatory agencies and to the public at large as a high-protein feed or food supplement. The nature of brewery waste streams is regarded as ideal for this type of food production, and commercial-size facilities are being constructed. Huige¹⁰ described work underway in 2006 by Noel and Bertrand,⁸⁹ Church,⁹⁰ and Irvine⁹¹ to develop systems using yeast and fungal species with these goals. This development continues, for example by Lee,⁹² to produce single-cell protein from brewery wastewater that could be used as a sustainable protein source for animal feed.

Other anaerobic organisms that produce electrons when they consume organic waste are being used in microbial fuel cells to generate electricity.⁹³ Microbial fuel cells have an anodic section (the anaerobic reactor) and a cathodic section (the aerobic reactor).⁵³ The effluent from the anaerobic section is the influent to the aerobic section. Electrons flow from the anode to the cathode, thus creating electric power.

27.4 SUMMARY

The brewing industry has been attentive to the environmental effects of their operations for decades. A major part of this attention was prompted by government regulations on waste streams that were discharged to the environment. There was also the important economic incentive to turn wastes into valuable by-products and to reduce product losses, which also reduces the brewery’s impact on the environment.

These concepts have evolved into the idea of sustainability, the concept of being able to satisfy the needs of our present activities and operations without negatively affecting future generations. Sustainability encompasses the triple bottom line of our activities, which are responsibilities for profits, for people, and for the planet.

These responsibilities have been included in the vision statements of large and small brewing companies worldwide. Their efforts are now also driven by a sense of social responsibility along with the traditional incentives of complying with regulations and maintaining efficiencies. Knowing that their customers expect and demand this corporate culture of responsibility along with a vision for sustainability has influenced corporate priorities and advertising. The results have greatly surpassed past performance in all areas and will surely continue to improve in the future.

ACKNOWLEDGMENT

Parts of this chapter (effluents) have been updated based on the original chapter in the second edition of this book, and the author wishes to acknowledge this former contribution by Nick J. Huige.

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* This Chapter has been updated based on the Chapter 18, “Brewery By-Products and Effluents” by Nick J. Huige in previous version.