8 PILLAR 4: NON-ENERGY SHIFTS

Over a third of emissions come from processes other than burning fossil fuels, and yet they don’t get nearly as much attention as fossil fuel emissions. Non-energy emissions come from three sectors: agriculture, industry, and wastes.

AGRICULTURE

About 20% of the world’s emissions are related to growing crops or raising livestock to feed everyone in the world. Some of these emissions come directly from the soil and livestock, and a large portion come from the conversion of land to make space for them.

DEFORESTATION

The biggest slice of agricultural emissions, making it the source of around 10% of total global emissions, is deforestation. To make more land area available to graze livestock or grow crops, farmers regularly cut down tropical forests which have been storing CO₂ in their plant matter and soil for a very long time. The one-time emissions from cutting forests (which are either released right then if the forests are burned, or over a short amount of time if the materials are left to decompose) are large. Then, without those trees to sequester more CO₂ from the atmosphere, a less immediate form of emissions occurs by reducing the annual amount of carbon sequestered by forests. This reduction is significant, but hard to quantify among annual emissions as it continues indefinitely without an objective “starting point” to compare any given year’s total amount of global tropical forest to.⁵³

Over a third of emissions come from processes other than burning fossil fuels.

Tropical deforestation contributes the bulk of this slice of emissions. Tropical forests store much more CO₂ in their dense growth and are often much older than temperate or boreal forests. However, forests are not the only relevant ecosystem—when this book refers to “deforestation” it also includes what the Intergovernmental Panel on Climate Change calls “other land use change,” encompassing the draining of peat bogs and loss of certain coastal ecosystems such as mangrove swamps. These other carbon-rich ecosystems can also fall prey to the need for more agricultural land and cause a portion of what we’re calling “deforestation” emissions.⁵⁴ They are also just as good targets for “reforestation” (or “ecosystem restoration,” to be more accurate) as a sequestration method—in fact, recent reports have suggested that they have a stronger short-term potential for sequestering carbon than forests, and should be the prime initial target for ecosystem restoration.⁵⁵

Not all ecosystem loss is caused by agriculture, but the bulk of climate change–relevant land change is. The culprits are a mix of small-scale subsistence farmers and large-scale commercial farmers, in roughly similar proportions depending what region of the world one looks at.⁵⁶ There is virtually never a malicious intention: people simply need money to survive, and growing food is one of the only ways they can make money, so they make the space to do so. Clearing ecosystems is cheap, and even if the soil becomes unhealthy and crop yields decline in a few years, growing a cash crop for that time can be well worth it to many farmers around the world. The greatest drivers of tropical deforestation are raising cattle, growing soy (some of which becomes feed for the cattle), and growing palms for palm oil.⁵⁷

Government regulations are particularly effective in limiting deforestation. Brazil did this successfully for about a decade until deforestation rates started increasing again around 2014 (and have since spiked significantly after anti-environmentalist president Jair Bolsonaro took office in 2019).⁵⁸ Other solutions involve practices that reduce demand for land and therefore reduce pressure toward deforestation. These could include better crop rotation, cover crops and interspersing of crops and livestock, denser livestock grazing practices, use of greenhouses (which extend the growing season and improve crop resistance to heat waves or pests), “vertical farming” (indoor growing in tall columns with plants densely packed, artificially lit using clean electricity, and maintained by automated machines in the building), and other techniques that achieve the goal of growing more from a given amount of land.⁵⁹

Vertical farming might look something like this, with columns of growing greens packed close together.

Government intervention to shift economies toward denser farming or non-agricultural sectors and enforcement of policies against deforestation can play a significant role in reducing this slice of emissions. Leadership from key tropical countries, and from other national leaders who can form partnerships with them, may be key to seeing progress in reducing deforestation. A relatively small number of countries contribute most of the deforestation emissions in the world, with a hugely disproportionate 45% of the total coming from Brazil. Indonesia is next at about 9% and about twenty more countries contribute around 1–3% each.⁶⁰

Shifting diets away from meat, especially meat from livestock, could also reduce deforestation. Grazing cattle takes up far more land area per unit of nutrition that someone will eventually eat compared to growing food crops. On top of that, cattle are usually fed with crops (corn and soy) that could have fed humans directly. The growth of those feed crops requires yet more land area.⁶¹

Policies that discourage the consumption of livestock—for example, carbon prices that incorporated surcharges on emissions-intensive goods, including beef—might slightly reduce global demand for livestock and thereby reduce the market for converting forests to grazing land.

CATTLE METHANE EMISSIONS

Livestock farming’s role in driving deforestation represents its largest contribution to emissions, but it creates emissions in another way as well. Cows, goats, and sheep belch methane as they digest food, and methane is a greenhouse gas eighty times stronger than CO₂ as measured over the ten- to thirty- year timeframe we have to keep temperatures from increasing more than 1.5 degrees Celsius (it’s actually closer to a hundred times stronger, but only stays in the atmosphere for about ten years, whereas CO₂ stays for thousands of years, so methane is often measured as thirty times more powerful over one hundred years, or eighty-four times more powerful over twenty years).⁶² Enteric fermentation (the process of methane being created as these ruminants digest food) is the second-largest source of agricultural emissions behind deforestation, equal to about 5% of the global greenhouse gas total.⁶³

Reducing the demand for livestock meat (and milk, which is much more carbon intensive than plants but much less than beef) could reduce these methane emissions. But in this case, a technological solution also exists. Several studies in recent years have shown that a certain species of seaweed, when mixed into cattle feed, dramatically reduces the cows’ methane output—some studies show reductions of 99%. There are several startups working to scale up production of this seaweed and commercialize its use in the near future.⁶⁴ Investment in such efforts and in projects to educate farmers about using these products in their cattle feed could virtually eliminate the livestock methane slice of greenhouse gas emissions.

FERTILIZER EMISSIONS

That leaves us with crops. To grow plants, farmers have to add some kind of fertilizer to the soil. Fertilizer, whether organic (compost or manure or similar) or synthetic (urea or other ammonia-based compounds) supplies nitrogen to the growing plants. The addition of nitrogen-dense fertilizer has enabled the vast growth in agricultural production over the past hundred years, and is one of the greatest forces countering pressure toward deforestation. Applying fertilizer means more can be grown per hectare of land, meaning less land area is needed. However, all fertilizers also cause emissions, because some of the nitrogen spread on the soil becomes nitrous oxide, another greenhouse gas that is hundreds of times stronger than CO₂, which spreads into the atmosphere.⁶⁵

Global emissions by type of greenhouse gas (based on the standard comparison over one hundred years—methane would look more important if compared over ten or thirty years).⁶⁶

Some farmers wrongly assume that more fertilizer means more yields. This is only true up to a point, after which extra fertilizer may actually decrease yields, while increasing nitrous oxide emissions.⁶⁷ So government or nonprofit programs could educate farmers about how to use fertilizer more efficiently to decrease, but not eliminate, these emissions. This is one slice that will need sequestration to make up for it by 2050, as these emissions cannot practically be eliminated while still growing enough food for the world.

SOIL EMISSIONS

Other crop-related emissions include those from the soil itself. Various chemical processes, largely inside bacteria that live in soils, both produce and consume greenhouse gases. For instance, in wet soils (such as rice paddies), anaerobic bacteria tend to produce methane. Dry soils may be a sink (sequestration site) for methane. CO₂, methane, and nitrous oxide are all produced and stored in soil, with the balance depending on how wet the soil is, its temperature, what kinds of crops (or grasses, or forests) are being grown on it, and more.⁶⁸ Some of these emissions can be mitigated by managing soils differently, which may also contribute the first few gigatons of sequestration needed (see Chapter 9).

There has been long-developing research into whether tilling soil is good or bad for climate change. For decades it was thought that tilling stirred up and released CO₂ stored in the soil, and that no-till agriculture practices would sequester more CO₂. More recently, researchers have noted that most studies examined only the top layer of soil (about a foot deep), and while the results are true for that layer, tilling actually mixes CO₂ into the slightly deeper soil, thereby sequestering about as much as it loses from the top layer.⁶⁹

OTHER AGRICULTURE EMISSIONS

Finally, small amounts of agricultural emissions come from the decomposition of crop residues and manure, as well as from energy use in agricultural processes.⁷⁰ The latter emissions will be eliminated through either electrification or synthesized fuels (see Chapters 6 and 7). The former may be reduced through increased use of composting or anaerobic digesters, which at least provide productive use of such crop or animal wastes, but some of these emissions will also likely remain.

In all, we can expect about half of agricultural emissions to be eliminated by 2050. Those from fertilizer, which are mostly unavoidable (and which prevent larger deforestation emissions if food were grown less densely without fertilizer), some portion of deforestation emissions (which would require strict regulation and enforcement in every country to eliminate), and small portions of soil and other emissions, perhaps as much as 10% of global total emissions, are likely to remain in 2050. Agriculture emissions are the hardest to totally eliminate, but they are also the easiest to balance with farm-based and forest-based sequestration of greenhouse gases, as we will see in Chapter 9.

GLOBAL OUTREACH INITIATIVE

All agriculture emissions can be reduced through changes in agricultural practice—for example, growing more food per hectare of land to reduce pressure toward deforestation, or managing crop rotation, cover crops, and sharing of land between crops and livestock to build soil carbon and reduce fertilizer use. A global outreach initiative should be created to get as many farmers as possible to adopt these practices. Such an initiative—working on the ground with every farmer in the world—could be carried out by a private nonprofit organization, perhaps with public funding support. Or it could be run as a public program akin to the Peace Corps, with one or more countries funding, training, and sending volunteers around the world to work with farmers.

The most important and viable practices to adopt will vary from location to location, but in general crop rotation (growing two or more different kinds of plants in succession in the same plot of land to balance the nutrients taken from and added to that soil) is known to improve yields and decrease demand for fertilizer.⁷¹ Grazing livestock in more efficient ways, such as interspersed with certain crops, could reduce pressures for deforestation.⁷² Public funding and direction should support not only the outreach project to get practices adopted, but also research efforts to quantify which practices will have the most impact in which locations.

A global outreach initiative should be created to get as many farmers as possible to adopt these practices.

The outreach initiative will not only reduce emissions, but contribute the first few gigatons of carbon sequestration by promoting ecosystem restoration and soil carbon sequestration (see Chapter 9). In connection to the initiative, national and local governments in key countries (especially those with tropical forests) should enact policy favoring forest growing or accelerating the adoption of new agricultural practices, and should implement stricter and more consistent enforcement of anti-deforestation laws. Where viable, partner government bodies could also create policies that reduce food waste, which contributes both to unnecessary agriculture emissions and to direct landfill methane emissions (see “Waste” section later in this chapter).

INDUSTRY

Industrial processes use a lot of fossil fuels for energy (mostly to heat raw materials in manufacturing), but some also involve chemical reactions that release greenhouse gases unrelated to energy inputs. These appear in the pie chart as non-energy “industrial process emissions.”

CEMENT

In the course of producing cement, limestone is heated in a kiln to turn it into lime, off-gassing CO₂ in the process. Lime, a chemical subset of limestone, makes up over half the material in the final cement. Most of the emissions from cement production don’t come from the fossil fuels burned to power the process: half to two-thirds are given off during this step of converting limestone to lime.⁷³

Over the years, various academic researchers have developed alternative cement production processes, which either off-gas less CO₂, or lock the CO₂ into the cement material itself during the process, thereby preventing most or all emissions into the atmosphere. A couple such processes are now being demonstrated commercially, such as one that reduces the proportion of lime in the final product, thereby reducing the direct emissions from turning limestone into lime, and which also requires lower temperatures in the cement kiln, thereby reducing the amount of coal used to heat the kiln. At least one company is commercializing cement that is hardened into concrete by absorbing CO₂ (rather than being hardened with steam as most cement is today), which further reduces the total emissions. That startup claims processes for hardening concrete could eventually lock up more CO₂ than is released in the cement production. While all concrete exposed to air absorbs small amounts of CO over decades, concentrated streams of CO₂ (from factories with CCS or filtered from the atmosphere) could be injected into and sequestered by this kind of concrete in larger amounts.⁷⁴

Other new processes can be designed to reduce the amount of fuel needed to create cement, or to reconfigure cement kilns to run on hydrogen for their heat input. Government efforts to convene academic researchers and bring more minds to the problem, to support startups, and especially to test out the most promising ideas at scale (proving new processes’ reliability is key to convincing companies to switch over to them) will be crucial to ensuring that most cement production is decarbonized by 2050. Some of the near-term reductions in cement emissions may also need to come from mandated or incentivized use of CCS.

STEEL

Like cement, direct emissions come from the process of steel production, where coking coal is added to raw iron ore to “reduce” it to pure iron. The carbon from the coal combines with the oxygen from the iron ore and becomes CO₂, about two tons of the greenhouse gas being generated for every one ton of steel produced. This “reduction” process can be accomplished with hydrogen instead of coal (as can the heating of the steel furnace), and the necessary input of carbon to turn the iron into steel could come from charcoal (which would have to be sourced from sustainably harvested wood) instead of coal. One Swedish company is working to commercialize hydrogen-reduction iron. One Massachusetts company is working to commercialize a different process which uses electricity and catalysts at high temperatures, rather than hydrogen, to reduce iron ore into iron.⁷⁵

About a third of the world’s steel furnaces already run on electricity (“electric arc furnaces”) but those are generally only used to process scrap steel rather than raw ore, and may not have large potential to replace traditional blast furnaces in the next thirty years.⁷⁶ Policies to encourage greater use of scrap steel could help drive the electrification of more steel furnaces.

Large-scale demonstration of alternate processes or pieces of equipment for both cement and steel production will be essential. Because these industries are massive, longstanding, and deal in structural building materials, they have little tolerance for risk in their processes. New processes must be proven thoroughly so companies know their material quality won’t be compromised if they switch over. Wherever policy mandates or incentives can push it, CCS on both steel and cement plants can also eliminate the process and heating emissions, though some technology development might be necessary to make it affordable.

Scaling up the use of other building materials can displace some demand for cement and steel and reduce—but not eliminate—these emissions. Wood, for example, sequesters carbon in a building itself when it is sustainably grown and harvested. Recent developments in cross-laminated timber make it possible to build even skyscrapers out of wood, often with equal or better strength characteristics compared to steel.⁷⁷ Growing a market for construction wood could help incentivize keeping forests as forests and managing them sustainably rather than clear-cutting them to grow soybeans for a few years until the soil is depleted.

AMMONIA/HYDROGEN

Beyond cement and steel, a couple smaller sources of industrial non-energy emissions stand out, including ammonia.

The synthesis of fertilizer (mostly ammonia) itself is energy intensive, but the direct emissions come when methane is split to get hydrogen as a feedstock for the process. Ammonia production happens to be the largest industrial use of hydrogen, but as noted in Chapter 7, almost all hydrogen currently used in industry has the same problem: methane (CH₄) is split using steam into hydrogen (H₂) and CO₂, and the CO₂ is released into the air. Hydrogen can also be produced by using electricity to split water, which does not release CO₂, but which is currently more expensive than “steam reforming” methane.

As discussed in Chapter 7, innovations to reduce the capital cost of electrolysis equipment may be the most significant improvement needed, as the up-front cost for electrolyzers can be larger than the total cost of methane-derived hydrogen for several decades. Other clean hydrogen produced from sustainable biomass or from methane with CCS could also decarbonize the ammonia synthesis process.

Some new ammonia production technologies show promise for replacing the entire current pathway and in some cases synthesizing ammonia directly from water and air without separately creating pure hydrogen.⁷⁸ However, clean hydrogen will still need to be produced not only for ammonia production and other industrial uses of hydrogen as a feedstock, but also for use as a carbon-free fuel itself and as a feedstock for the synthesis of carbon-neutral drop-in fuels (see Chapter 7). This should be a key priority for enabling synthesized fuels, and could benefit from government convening and coordination, extra research and scale-up funding, information sharing, and testing and demonstration initiatives.

ALUMINUM AND OTHER SOURCES

Finally, aluminum production, which is one of the few major chemical manufacturing processes currently powered by electricity, has some direct emissions from CO₂ being off-gassed by the electrodes as they operate.⁷⁹ New electrodes could be invented that use different materials and don’t have the same side reaction that currently creates CO₂. Basic research funding and then prototyping and testing-phase support are the key efforts needed for aluminum.

Still other direct emissions come from tinier industrial sources, but those explored here are the most important and readily fixable ones. The others, too, will need similar new processes developed, or in some cases may be small enough that we can rely on sequestration to make up for them.

WASTES

Agriculture accounts for almost 20% of total emissions, and industry direct emissions amount to another 7% or so. The final non-energy category includes material waste systems (contributing about 3% of emissions) and wasted “fugitive” methane (contributing about 5%).

BIOMASS AND WASTEWATER

Some emissions are released by wastewater treatment, and some from landfills. In particular, organic matter (food or farm waste) that gets thrown out into landfills decomposes into methane, some of which leaks into the atmosphere.

Policy to reduce food waste could cut down this slice of emissions, and increased use of composting, anaerobic digesters, and other non-landfill methods for processing organic waste could reduce those methane emissions. Methane can also be captured from landfills and burned, which at least converts it into CO₂, a weaker greenhouse gas than methane itself. Through policy, the plants that burn this waste methane could be required to use CCS and make that process truly carbon neutral.⁸⁰

FUGITIVE METHANE

A different category of waste emissions is “fugitive” methane that escapes from the energy system. When methane is extracted from the ground (and sometimes when coal and oil are extracted, even if methane is not also being intentionally extracted) some bit of it leaks into the air. When it is transported to end-use equipment through networks of pipelines, a little more leaks out. And in various bits of equipment along the way, methane is used for mechanical processes or partially burned in compressors to maintain pressurized pipelines, and the unburned methane is released into the air. Sometimes methane pipeline leaks cause explosions or fires in cities, but usually the methane simply floats into the atmosphere.

Methane being such a stronger greenhouse gas than CO₂, these fugitive emissions account for a full 5% of the global total of emissions.⁸¹ They come from the energy industry, but the leaks are a total mistake, not a result of burning fossil fuels for energy, and the equipment-based emissions are basically accepted but not intended. They are one category of emissions that comes with absolutely no benefits to anyone (in fact, they mean economic losses for the methane extraction and distribution companies, meaning slightly higher costs for consumers). Tightening pipelines and other methane infrastructure, switching to electric compressor pumps, and adopting new equipment at wellheads could reduce these emissions. Switching to synthesized methane (see Chapter 7) could eliminate the half of fugitive emissions that come from extraction. And eliminating methane use altogether through electrification and conversion to other synthesized fuels would of course eliminate these emissions, though it’s well worth pursuing policy mandates or business campaigns to reduce fugitive emissions in the meantime, because that can cut out a slice of emissions much sooner than we can expect all methane use to disappear.

REMAINING EMISSIONS

Including wastes, industry direct emissions, and agriculture, there are portions of emissions slices that probably won’t be eliminated by 2050. Sequestration will have to make up for this remainder, which will probably be something around 15% of our current emissions (maybe 2% from material waste, 1% from pipeline methane leaks, 2% from industry, and about 10% from agriculture, with possibly tiny bits of energy-sector emissions also remaining).⁸²

In order to keep eventual sequestration costs reasonable, this means that it is all the more important for energy system emissions to be virtually eliminated.