CHAPTER 15

Making and Sharing Waste Recycling: Recyclebots

According to the U.S. Environmental Protection Agency (EPA, 2015), the average American produces about 4.5 pounds of waste every day. In nature, there is no such thing as waste; anything generated from one species is simply used as a resource by the next species. Think of mushrooms living on dead trees. There is no reason humans can’t learn from nature and follow that design methodology (McDonough and Braungart, 2010). The waste that is generated in your home and business, rather than being a source of loss (e.g., landfill tipping fee), can be treated as a resource. Countless environmental organizations flog “reduce, reuse, and recycle” as a mantra to help the environment by saving money, energy, and natural resources.

This book has already covered a lot about reusing what would be waste as feedstock for our making. We know from Chapter 1 that using an efficient version of Linux, you could resurrect a Microsoft Windows–based computer and then load it up with all kinds of open-source software to make all manner of creations covered in Chapters 2 through 8. Chapter 9 covered some ways to use free patterns and old clothes as starting materials for new, better clothes. Chapter 10 discussed how makers are using waste wood, such as pallets, to make incredible furniture, and Chapter 11 covered how you could use open-source designs to reuse electronics parts. Sometimes waste cannot be simply repurposed and reused, however. In these instances, the waste needs to be recycled, and Chapter 12, which relied on digital manufacturing techniques, hints at the types of feedstocks that would be the most useful to you as a maker: polymer or composite feedstock and metal wires for 3D printers, sheets of plastic or composite for cutting, and blocks of material for milling. There are many paths to take for this distributed recycling and manufacturing (Dertinger et al., 2020). Let us consider the most mature methods now.

Recycling Waste for 3D-Printer Feedstock

The explosive growth of 3D printing discussed in Chapter 12 brings with it the risk of creating even more un-recycled and wasted plastic. Not every print is perfect. Most people with desktop 3D printers have a box under their desks of failed 3D prints. Could this be a resource as well? The most common types of 3D printers derived from the RepRap use fused-filament fabrication (FFF) and thus demand filament. Fortunately, the economic advantage of distributed manufacturing proven in Chapter 12 increases by an additional order of magnitude with the introduction of recyclebots (Baechler et al., 2013). Recyclebots (www.appropedia.org/Recyclebot) are waste plastic extruders that are used to produce 3D-printer filament from ground-up plastic waste. As you might guess, these tools are pretty good for the environment. Previous research on the life-cycle analysis of distributed 3D printing (Kreiger and Pearce, 2013a, 2013b) already shows that the environment benefits from the reduced transportation of products using traditional manufacturing. The recyclebot process using postconsumer plastics instead of raw materials, however, showed a 90 percent decrease in the embodied energy of the filament from mining, processing of natural resources, and synthesizing compared with traditional manufacturing (Kreiger et al., 2013, 2014). The plastic waste that can be recycled in the United States, shown in Figure 15.1, can all be converted to 3D-printer filament with a recyclebot, but there are many more types of plastic than just the seven identification codes listed in Figure 15.1. In China, the polymer identification system has seven different classifications of plastic, five different symbols for postconsumer paths, and 140 identification codes (Standardization Administration of the People’s Republic of China [SAC], 2008). I was told by the head of the U.S. committee in charge of recycling codes that politics will ensure that the U.S. system is officially trapped in only identifying seven polymers. Luckily, the maker community in the United States is not as challenged. A recent study (Hunt et al., 2015) has already provided a solution for this problem by developing a recycling code model based on the Chinese resin identification codes that is capable of expansion as more complex 3D-printing materials are introduced. If you become the manufacturer, you can tag your own products with the code for the plastic you use so that you can recycle it later when you are tired of it or it actually wears out.

Figure 15.1 Plastic recycling chart. Image courtesy of SouthPack LLC. (Pexel free license) https://www.pexels.com/photo/plastic-recycling-chart-237535/

With a recyclebot, you can recycle plastic in your own home to save money by offsetting purchased filament, as well as the products you can make with the filament (Zhong and Pearce, 2018). Many versions of recyclebots have been developed by both amateurs and professional makers, such as Matt Rogge from Tech for Trade and even retirees who make them for fun like Hugh Lyman. Major recycling organizations have also made completely open-source versions of recyclebots, including: Plastic Bank, Precious Plastic, and Perpetual Plastic. In addition, there are recyclebots that you can simply purchase, such as the EWE, Extrusionbot, Filastruder, Filafab, Filabot, Filamaker (also has shredder), Noztek, and the Strooder, Felfil (OS). Many of these recyclebots have been used on common 3D-printing failures—so they are comfortable working with polylactic acid (PLA; Cruz Sanchez et al., 2015, 2017), as well as acrylonitrile butadiene styrene (ABS; Mohammed et al., 2017, 2019; Zhong and Pearce, 2018). Recyclebots can also be used for more common plastics, such as high-density polyethylene (HDPE; Baechler et al., 2013), and trickier materials such as flexible elastomers (Woern and Pearce, 2017). Perhaps most excitingly, you can combine wastes in a recyclebot to make new materials. For example, you can take waste saw dust and add it to PLA to make waste-wood composites (Pringle et al., 2017) that you can use for 3D printing. This early work, however, hardly begins to scratch the surface of the potential to use distributed methods to recycle a much longer list of polymers, as well as composites made up of multiple distributed waste streams. Recently, to carry on the open-source design mentality (Oberloier and Pearce, 2018) in hardware espoused by the RepRap community, my research group and I made a RepRapable recyclebot. This type of recyclebot, shown in Figure 15.2, can be largely manufactured in your living room with any of the types of RepRaps discussed in Chapter 12. It works for a wide range of common 3D-printing plastics such as PLA and ABS.

Figure 15.2 RepRapable recyclebot, a waste plastic extruder that makes 3D-printer filament, which can be used to print most of its own parts. (GNU GPL) https://www.appropedia.org/File:Recyclebotrep.png

Recyclebots can even be mounted directly on 3D printers. This is what re:3D, an open-source 3D-printer company made up of a bunch of NASA engineers, has done. My lab, in conjunction with re:3D, has demonstrated the ability to directly print large products with what re:3D calls the GigabotX (shown in Figure 15.3) from waste from PLA, ABS, polypropylene (PP), and polyethylene terephthalate (PET [what makes up water bottles]; Woern et al., 2018b) and advanced stronger materials such as polycarbonate (PC; Reich et al., 2019). Being able to print in PC is important because of its higher melting temperature and strength. This allows you to print molds for lower-melting-temperature plastics. Thus, if there is something you want a lot of—or if you want a really large solid object—it is much easier to print the mold (just the outside) and then use a recyclebot or injection molder to fill it. Ultimaker’s open-source Cura slicing software already has a default mold-making slice, so if there is a 3D object for which you want to make a mold, you don’t even need to specifically computer-aided design (CAD) it because you can start with an STL file.

Figure 15.3 The GigabotX, an open-source plastic pellet 3D printer. (GNU GPL) https://www.appropedia.org/File:Gigarecycle.png

Figure 15.4 An open-source pelletizer that can be used to make sophisticated feedstock mixtures for composites in 3D printing, sheet forming, or block molding. (GNU GPL) https://www.appropedia.org/File:OSpellets.JPG

To assist with this type of recycling, my student and I also developed the sophisticated pelletizer seen in Figure 15.4 (Woern and Pearce, 2018). This pelletizer can be made with a drill and some 3D-printed parts to enable fractional mixing of several material streams (up to four with the current design). This gives you the power to make sophisticated, controlled composites with different plastics or entirely different types of waste, such as paper, cardboard, sawdust, powered metal, glass, and so on.

Printing with waste plastic even improves the economics further for 3D printing your own products. As we discussed in Chapter 12, you can normally save 90 to 99 percent of the total cost of an item when 3D printing a product with commercial filament than when buying it from a store or online. Commercial filament has a huge markup and costs anywhere from about $15 to $80 per kilogram. You can make filament with a recyclebot from pellets for less than $5 per kilogram. Better yet, if you shred your own waste, the cost is only the electricity to run the machines, which drops the cost below 10 cents per kilogram. If you use insulation on the hot end of your recyclebot, this value can come down to only 2 or 3 cents per kilogram, depending on how much you pay for electricity. If you happen to have built a solar-powered recyclebot (Zhong et al., 2017) or 3D printer (King et al., 2014; Gwamuri et al., 2016), the marginal cost of the whole process is essentially free to you. Critics will point out that I didn’t factor in a time cost. Of course, it will take you some time to make the products you want, but normal people don’t charge for their own time to do things for themselves. When was the last time you calculated the opportunity cost to butter your toast in the morning? Or if you go to McDonald’s, do you calculate the opportunity cost to drive yourself? Even Warren Buffett (net worth $74 billion) drives himself to McDonald’s for breakfast every morning on his way to work (Elkins, 2017). Not that this is his best idea ever—so don’t copy that one!

When you make things yourself, the savings get simply silly. Consider the whole process shown in Figure 15.5 for making a camera lens cover. It is made out of ABS, the same plastic as Legos. There is a lot of ABS waste in anything computer related. The source of the ABS used in this case was from e-waste from my university’s information technology (IT) department dumpster. It was ground up in an open-source granulator (Ravindran et al., 2019), made into filament by a vertical recyclebot, and then printed into a lens cover. The total cost in electricity was only 3 cents! An equivalent camera lens hood costs $9.99 on Amazon. Thus, you could make 333 camera lens hoods for the same economic cost as purchasing a single one (Zhong and Pearce, 2018). Lastly, I should point out that you are not limited to making only small things. It all depends on the size of the printer you can get access to. Today, many libraries, community centers, makerspaces, fablabs, and machine shops have 3D printers on which you can start to make large products. For example, the kayak paddles that you can custom make for yourself (Figure 15.6) can be made for a small fraction of the cost of high-end kayak paddles (Byard et al., 2019).

Figure 15.5 The whole process of waste plastic conversion to a product through a vertical recyclebot. (GNU GPL) https://www.appropedia.org/File:Recycledabs.jpg

Figure 15.6 3D-printed kayak paddles made from waste ABS. (GNU GPL) https://www.appropedia.org/File:Kayak3dp.jpg

Sheets, Blocks, and Bulk Extrusions

You can use recyclebots as compounders and the pelletizer to produce plastic for making sheets, blocks, or bulk extrusions. Although you might want to own a 3D printer yourself to manufacture products for yourself (and the average person may even consider a recyclebot), for larger, more expensive tools such as a GigabotX, hot presses, or large extruders, it may make more sense to use them in a shared facility.

For example, Waste for Life (www.wasteforlife.org) is a loosely joined network of makers who work together to develop poverty-reducing solutions to specific ecological problems. One of its projects involved collaboration with researchers and community members in Canada, Argentina, the United States, Australia, and Lesotho to build the open-source Kingston Hot Press to provide the means of production to smaller cooperatives in communities anywhere in the world. A hot press allows the user to produce a value-added composite tile out of waste plastic and fiber, most commonly cardboard and paper. You can use a hot press to start to recycle waste plastic for larger, bulkier projects for which you need a good source of sheeting. The sheets can be made into millions of products by either heat forming them by hand or by using something like an open-source CNC cutter to cut them into 2D shapes for assembly.

Similarly, Precious Plastic (preciousplastic.com) is a global community of hundreds of people working toward a solution to plastic pollution. All of its recycling solutions are free and open source as well. Precious Plastic’s systems are designed to be modular, and you can construct them yourself if you have access to a decent machine shop. If not, the group runs an online bazaar where people who have access to welding and metal-cutting tools will make the parts or the whole machines and sell them for reasonable prices. Precious Plastic currently has shredders, an extruder (recyclebot), an injection molder, and a hot compression machine. By making large metal molds and attaching them directly to the extrusion machine, the group can make large recycled plastic blocks or even plastic timber (just like the really expensive stuff some people use for decking).

The tools for plastic recycling at the distributed home user scale are relatively mature and well-documented, as shown earlier. For other materials, such as glass and metal, the communities are smaller and the technologies less advanced. Sand is relatively inexpensive, so recycling glass in an economical way, even at the industrial scale, is challenging. There are some projects that you may be interested in if you have some top-tier maker skills, such as the Kube OpenLathe, which is an open-source glass-blowing lathe that was funded on Kickstarter. Open Source Ecology (www.opensourceecology.org), a nonprofit group I will talk a lot more about in Chapter 16, is also working on an open-source induction furnace that will bring metal recycling much closer to home in the future.

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