 The year is 2073. Fossil fuels have run out and been abandoned two decades ago, and our ways of life have changed dramatically. Without an excess of cheap energy, our ability to create and transport fertility came to an end. Dispressed villages and neighborhoods are organized around food production, local energy sources, and surviving infrastructure. Waste never disappeared, and composting systems have attempted to pick up the slack. This is the Lotech Podcast. Hello and welcome. I'm Scott Johnson from the Lotech Technology Institute, your host for podcast number 63 on January 13th, 2023, coming to you from the Lotech recording booth. Thank you for joining us. Today I'm chatting with Matt Crisp about the future of composting. And don't forget to follow us on Twitter. Our handle is at low underscore techno. Like us on Facebook, find us on Instagram, subscribe to us on YouTube, and check out our website, lowtechinstitute.org. 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Today I'm chatting with Matt Crisp, a farmer and forester who you may know as one of the co-hosts on the Poor Pearls Almanac podcast, where he recently wrote and presented an episode on composting. He just completed a BS in plant biology at the University of Vermont, focusing on sustainable agriculture and statistics. His current areas of study are in agroecology and appropriate technology, which as an aside, wasn't originally going to be the name of the Institute, but I didn't want to explain what appropriate technology was every five minutes. But now I find myself describing our own definition of low technology regularly. So at any rate, you can find Matt on Instagram under at matt.crunchy. But for the next bit, I'm glad to welcome him here to the podcast to talk composting. Hello, Matt, and welcome. Hi, Scott. Thanks so much for having me on. I'm really excited to dive into this. Okay, so the year is 2073. And as regular listeners will know, we're dealing with a world that has transitioned away from fossil fuels. If we were going to visit a village in that future, they'd certainly be composting. Would they be composting like we are today? Well, the short answer is probably not. The reality is a lot of the composting that happens today, alcohol, quote, industrial composting is built onto a fossil fuel dependent waste system. From garbage trucks hauling scraps out of town to the giant windrow turning machines and earth movers that are required to keep the operation running. Now, of course, these systems don't account for all our composting today. But the important thing is that if you live in an urban area, which is roughly four and five Americans today, your options for organic waste removal are compost, the landfill or the sewer. Before we jump right into the future, why don't we talk a little bit about compost generally? Matt, anyone listening to this probably is familiar with composting generally. But can you break it down and I guess pun intended and lay out what is composting at its most basic level? Sure. So composting at its most basic is the breaking down of organic material into a nutrient rich soil like product called hummus. That's H-U-M-U-S, not like the food. Right. The vast majority of this breakdown is the result of fungi and bacteria that live in the pile and essentially eat it. If listeners want to learn more about the process, I did an episode for the proper almanac called the science of compost that provides a lot more info on what's going on inside the pile. Can you maybe give us a few brief examples of the most common composting method seen outside of the industrial system today? Yeah. So composting is one of those things that can be as simple or complex as you want it to be. At the very simple end of the spectrum, it looks like a pile of scraps and organic waste that you turn every now and then with a pitchfork. The other end, it might look like a decomposition heated greenhouse, a home hot water system or a full on biogas refinery. Are there some less known methods that are really effective or easy or should be better known? I mean, the thing about compost is that it's so approachable. I'm going to go out on a limb and say that anyone listening to this podcast thing can take up composting in one way or another. A couple of methods I think are really cool. Compost tumblers that aerate the material by like tumbling it in a closed barrel. Another is Johnson Sue bioreactors that essentially have airways and an irrigation system built in so they require no turning. For a system that requires no daily maintenance, they require surprisingly few materials, some landscape fabric, a metal cage, a bit of hose, really nothing that couldn't be sourced pretty much anywhere. The Johnson Sue bioreactors are really cool and I wish I could say I had any relation to the Johnson part of that name, but alas, I am of no relation. But and I don't know about you, but if you post about composting on social media, you probably get the ads for the electrical appliances that sit in your kitchen counter and claim to compost your scraps in just a few hours. Correct me if I'm wrong, but from what I can tell these things just use a ton of electricity to dehydrate and chop up food scraps, which still need to be finished in a real compost pile. I only mentioned it to warn folks away from picking up one of these. Yeah, I really don't have a lot of time for those like a several hundred dollar piece of machinery that's outperformed by like a five dollar bucket and some reading on the internet. Exactly. So OK, let's turn now to our post transition future and climb into our time machine. Let's visit a Midwest village that is locally sufficient without fossil fuels or a lot of external inputs. OK, we step out of our time machine. What do we see? Well, the systems this village has in place are really going to depend on what's called the logic of the ecosystem. I'm borrowing this term from Ray Reese, who defines it as the nature of the energy technologies and resources to be exploited in an ecosystem without inflicting damage upon it. We could debate how this is worded, but I think it's a good starting point when we think about what a future way system might look like. Sure. Part of a technology being appropriate is that it fits in where it's used. It makes a lot more sense to take advantage of the energy that's already in an ecosystem rather than importing it. OK, so the Midwest in 2073. What are we looking at? Well, this village would most likely be in a former industrial agricultural landscape at large seasonal temperature change and prone to storms and droughts. The road infrastructure would probably be in poor shape and farming would most likely have turned towards more subsistence, perennial and or drought tolerant crops like tree nuts, potatoes and sunflowers. Much of the landscape might support grazing or have started regenerating into a fire-mediated savanna. Larger towns might be supported by rivers, canals and railways. Sure, the area where people have access to transportation and fresh water are the ones that are going to thrive. It probably would reflect areas that were occupied before the fossil fuel era. In this landscape, composting can and probably will take many forms. Manoa collected from barns, for example, may be composted together with garden residues in a greenhouse to provide a more stable and extended growing season for the highest value and most delicate crops. The New Alchemy Institute worked on a project like this and stood you, right? Yeah, exactly. The New Alchemist had a purpose-built greenhouse to capture the heat, moisture and CO2 from the manure bays built into it to grow all winter. I'm trying a modular version of this that we installed in a neighbor's greenhouse. We're testing it right now, but I can tell you it does put off a lot of heat. But getting back to the real future farmers of post-industrial America, what are some other ways that our future mid-westerners may be composting? Well, the Johnson's Soup by React, as we talked about earlier, may be a fixture of fermiads in this new landscape where simple materials needed to build them can be sourced. Clustered around an elevated rain barrel, these would provide rich soil for studding seedlings or maybe mixed into a slurry and used to coat larger seeds like acorns and hazelnuts before planting. I guess it would be the closest thing to what we generally think of when we talk about farmyard composting. But why not just turning regular piles? That seems like much less of a complex system to take care of. Absolutely. Yeah. Building these by-reacted requires a certain amount of materials as well as know-how. The decision to put this system in place or to put any of these systems in place comes down to a couple questions for our future composters. One, do I have access to the things I need to make this happen? And two, is it going to be worth my investment of time and energy to build, run, and fix it when it breaks? Got it. So for any of these systems, those questions need to be answered. Assuming the answer to both of these questions is yes for any one system, how else might they be using decomposition to their benefit? One of the most interesting composting systems, and I'm using the word compost kind of broadly here, involves producing methane, something that we usually try to avoid. Usually, aerobic bacteria are in charge of breaking down our piles, but when they run out of oxygen and aerobic bacteria take over and start to produce methane. Which is why some people think that compost piles stink? Right. They can smell if they're not getting enough oxygen, but if we do it on purpose, we can capture that methane and we can use it for fuel the same way we use natural gas. In a future where fossil fuels have run out or we simply can't access them, this might be a very attractive option. Now, this isn't some far-fetched possibility. This is something that people have been working on and doing for some time. There are lots of reasons we don't see more of it, mostly based on the fact that fossil fuels in the US are in many ways more attractive alternative, but elsewhere it's making strides. Germany is Europe's biggest producer of biomethane with a capacity of 5.8 gigawatts. To put that in perspective, that's producing the same amount of energy as almost 2,000 of those larger wind turbines you see, or for fun it equals about six and a half million horses. And just like those horses, the bioreactors also produce compost in the end, right? It sounds like biogas has a lot of potential, especially in a more distributed energy network, one that lacks access to the dense fuels that our lives are built around today. Not only that, but biomethane can use a lot of the same equipment that natural gas uses today, meaning retrofitting is a real possibility in a lot of places. Yeah, that's absolutely right. And so the first thing you talked about was the logic of the ecosystem. If we get back in our space time machine and went somewhere different, like the Southwest, how would things be different? I'd say one of the starkest differences would be the water, right? Any composting system is gonna have to do its best to conserve its water. The microorganisms that process compost need roughly 50% moisture content to remain active, depending on the starting material. However, if we think of just our standard garden compost pile, a couple things that are working against this 50% figure, it's heating up which allows the water to evaporate faster. This is accelerated when it's turned and the water inside is exposed to the drier air. So what can you do to avoid letting more water evaporate than you need to? Well, the Johnson's Zoo bioreactors could also provide a good answer here. They do require a regular supply of water, but none of that really goes to waste. And the fact that the compost doesn't have to be turned means that this is a really pretty efficient system to be used in dry areas. In fact, it was developed at New Mexico State University. Another option that I mentioned that I think has some merit but needs some work, a large compost tumblers. The problem with most small compost tumblers in dry areas is that they don't use water very efficiently. Water is constantly escaping with the air exchange and the smaller volume of compost means that it uses water less efficiently. On the other hand, if the system is scaled up to using say like 55 gallon drums, this becomes less of a problem. Add events that only open when areas the cool list at night and your water savings might become pretty significant. Another issue I've noticed with the small tumblers is that their volume is so small they lose heat too fast. Really under a yard at a time is tough to keep going hot. But anyway, to me the Johnson Sioux system is looking like the more efficient system, not to mention less complicated. Well, hold on because there's one more important factor in the potential decision here, time. While a Johnson Sioux biodegesta takes between nine months and a year to produce finished compost, a tumbler can produce compost in as little as three weeks. That's pretty significant, especially when you think of how much water and organic material is tied up in the Johnson Sioux systems for this long period of time. In the tumblers on the other hand, if there's a critical lack of water, it doesn't mean that the whole thing needs to be taken apart. If a Johnson Sioux system dries out, the whole thing needs to be rebuilt and that's a pretty big blow. It seems like there's a real trade-off between efficiency and how quickly this system is able to adapt. If you really want to be efficient with your water, it seems like you're locked into one method for a while. Right, and it's demonstrated here nicely, but this is sort of a general pattern we see in lots of things, including ecosystems. Generalists can work in a lot of different places, but efficient and complex systems are adapted to one specific set of conditions and are vulnerable to disruption. Anyway, it's just interesting to see where this pattern pops up, especially when making decisions around the appropriateness of one technology over another for specific conditions. Okay, well, talking about specific conditions, if we're ready to get back in our space-time machine and see the same year, but this time in New England, how would things be different? So we'll likely face the same issues with the degraded bird infrastructure due to freezing winters that the midwest faces, but there's one important difference, coastal access. This well, it means a lot of things, but a dense coastal population that at the same time has to deal with more intense storms will undoubtedly be a characteristic of 2073 New England. And in terms of the ecosystem? Well, the forest regeneration is a big difference. Now, future New Englanders, New English. Isn't it Yankees? Yeah, it is Yankees, right? Anyway, in areas where farms, silver pasture systems or carpuses are being established, or just broadly speaking, woods are coming under management again. There's likely to be a surplus of brush and woody material. That's where Jean-Pain thermal composting piles might come into play. What it is, is essentially a big pile of shredded wood through which a long pipe is wound. Mother Earth published a great article on this back in 1980 with an account of their own experiment. They found they could produce a two gallon per minute flow of 85 degree Fahrenheit hot water with a pile measuring roughly eight feet tall and 10 feet wide. In addition to heat that can be captured by either air or water, these piles produce high quality compost and even biogas. Okay, I'll be honest, that sounds like a huge amount of wood in a pile to move around. It is, but Jean estimated that a pile can be built from 16 tons of clippings. The amount of brush that can be removed from an average acre of timber during a year of normal stewardship. After it has posted it provides the right amount of hummus to add to an acre of land used for growing cereal grains. That's a lot of work for one or two people, but for a small community and as a byproduct of normal timber management, it might be a good use for waste aid to keep a tree nursery or something like that warm. All right, that makes a bit more sense for how the system might find its place. Yeah, the scale at which these systems find their use is really important for a person or a family, the fixed cost of some of these more complex systems like that more complex compost tumbler we talked about can be overwhelming. If you're growing a personal garden, a simple hand turned pile may very well be your best option, but when you're aiming to meet the fertilizer requirements or part of the energy requirements of a community, those fixed cost don't seem so daunting and there's some more room to experiment with these other systems. Okay, so hang on, we started this episode talking about how these large composting facilities were unsustainable and now you're saying that large composting systems are the way forward for us. I think when it comes to appropriate technology, one of the things we need to look at closely is scale. You can go and look up a definition for appropriate technology and part of it will almost always be quote small scale, but that doesn't really get us or these like future communities very far in making decisions around the systems they want to put in place. That's true, at LCI we often talk about individual household or community scale solutions to give people a real sense of how big or small we're talking about and you've mentioned the fixed versus variable cost of a system and that's one way of making a decision and an earlier episode also examined various technologies with the is it low-tech test, both of these provide a way to examine the appropriateness of a scale. So how do we put it all together? A good way of doing this is looking at diminishing returns and again the logic of the ecosystem. Let's take wind turbines for example, they're a great way of taking a resource from the ecosystem, wind, and making it useful to us without causing extensive damage. Now proponents of large-scale wind farms, let's call it like utility-scale generation, will say the massive blades on the three megawatt turbines mean they can capture more energy even in lighter wind, but if we take into account the true cost of materials, maintenance, manufacturing, transmission, and vulnerability damage of a utility system it becomes clear that we don't pay the full price of it today. The point of diminishing returns really is a lot closer than what is reflected in our current energy infrastructure. I mean there are other reasons for that too that involve legislating and contracting these projects, but in terms of cheap energy it's just not a limiting factor yet. Well that's bad news isn't it? Based on what we're choosing to build a so-called green energy infrastructure out of? That's right. The area covered by the average turbine rotor has grown 600% since 1998 according to the Department of Energy, but if we want to scale down our systems we have to be aware that there are diminishing returns in that direction too. At a point it doesn't really make sense for everyone to be building and maintaining their own big turbines. There's too much redundant material. It requires too many people to have expertise in generating power. It just doesn't make sense from a low tech perspective and that's why determining the appropriate scale of the technology is important, but you didn't bring me on to talk about wind power. Yeah I wanted to talk about future compost and now we've been blown way off course by all this wind. Well let's talk about a technology that I think will probably be a fixture of these coastal communities, seaweed biodigestion. As a bioenergy crop seaweed can yield over 10 and a half tons of dry mass per acre. Compare this to two of our most popular crops, corn and soy, which yield just over two tons and less than one ton of dry mass per acre respectively. Not only this seaweed is between 85 and 90% water making it very suitable for anaerobic digestion. It sequesters over 25 tons of CO2 per acre and requires no fertilizing. In fact taking into account all the fertilizer that's produced as a byproduct of the biogas generation it's actually in that fertility gain for our communities. That's pretty significant. If these end up being denser settlements relying on many vegetable gardens like we've seen through history this fertilizer will probably be very important. So bring it back to scale. What scale do you think would be appropriate for this? Harvesting seaweed is a much different process than harvesting biomass from a field or forest. It requires usually boats, crews, networks of shipyards, builders and repair people to keep a fleet running. So to answer your question it necessitates production at a community scale rather than a family or a personal one. The other thing I think might happen different from the systems in Midwest that we talked about is a certain amount of refining of biogas into biomethane. Wait what's the difference between biogas and biomethane? Well biogas is the raw product of anaerobic digestion. On the lower quality end biogas contains about 50% methane, 45% and CO2 and up to 200,000 parts per million hydrogen sulfide which can damage the tanks and tubes it passes through. But the refining process can be surprisingly low-tech. There are two main things we need to remove from our biogas, CO2 and hydrogen sulfide. The first step is removing the hydrogen sulfide by running it through an iron sponge. This sponge is made of wood chips impregnated with iron oxide or rust. That's it? Well that's not hard to get rust. That's something you could do at home. Ever heard the term rust bucket? Usually we say this about a car but it used to be a bucket or more likely a barrel where all the iron would be chucked when it was no longer usable. This was filled with water and the rust would slough off and form a thick layer at the bottom. It was used in barn paint as a microbe inhibitor and that's why barns were red before paint was commercially available. Anyway I got a little carried away. Tell me more about the gas refinery I'm now building in the town square. I had no idea that was the origin of the term rust bucket but okay so for this town square refinery this iron sponge reaction works best at between 77 and 122 degrees Fahrenheit which really isn't that hot all things considered. Next the CO2 is separated by dissolving it in a column of water at high pressure because CO2 can dissolve more rapidly in water than the methane can. This happens at about 150 psi which is what a nail gun uses so high pressure yeah complex and expensive equipment not really. Okay I take it back putting together a biogas refinery in 2073 seems pretty doable maybe not every house on the block but certainly a group of families or a small community could run one but why refine it in New England and not the Midwest? I think it would come down to where it's required there's no reason Midwesterners couldn't build one they would have roughly the same access to materials but I think they would probably just be less of a need to export the energy they create using it as close to the point of production as possible means a simpler and more robust system if you're using it for heat light electricity whatever you might be able to do it without the added complication of refining however I think in New England seaweed based biomethane could become a viable maritime fuel for short journeys. Now through this whole episode we haven't really talked about a pretty big problem that we need to tackle that's human waste through all these different systems and locations we know that any system we choose is going to be matched to the logic of the ecosystem and implemented at an appropriate scale let's talk through some of these for each of the locations we looked at. Sure so for a theoretical Midwest farm maybe a multifamily farm um population density is pretty low and there's lots of potential uses for the waste so there's plenty of options where orchards or woods or corpses are being planted arborlews might be a good option I'm sorry say that again arborlew? Yeah arborlews are these moving outhouses and the previously used locations are planted with trees after each move to produce a boost of fertilizer to the new plant things. Another option lined pitla tree ends are simple to build however they can potentially pollute groundwater especially in areas prone to flooding. Here I think urine diverting dry toilets are a good idea they're relatively simple the toilet designed to separate urine and fecal matter and store them separately after each use the dry waste is covered with ash or soil dust or something that absorbs moisture and it's the chamber is periodically emptied there's a few options to treat it before it's used as fertilizer or soil conditioner these include heart composting polarization chemical treatment or simple storage for two years. The urine also needs treatment if it's going to be used in agriculture but not for as long. It might surprise you to hear that one of the most popular pages on our website is where I outline how to use urine and ash to fertilize tomatoes. I think more people are interested in this than we actually might think would it work in other regions. Absolutely so let's look at the southwest in areas where water in this sanitation system is probably the most limiting factor urine diverting in dry toilets also provide a good option. Diverting urine means that for many crops especially slow growing ones or ones that are cooked before eating water can be reclaimed quickly and efficiently. There are several barriers to disease spread for both consumers and workers that include really simple measures like storing the urine for a month, wearing gloves and washing your hands after application which if you're working in fields is just you know good practice anyway. So I guess solarizing the waste in the southwest might also be a good option? Yeah definitely. Lastly in the northeast where denser settlement could continue for longer around local sources of energy. I think these urine diverting dry toilets also could have a role to play. The dry matter may be collected and used in bio digesters the urine might be stored in a drought and otherwise just let to infiltrate into the soil. Hang on you just recommended the same system for three totally different areas of the country doesn't their ecosystem logic have anything to say? They do but there are lots of other factors outside the ecosystem that contribute to this decision as well. These urine diverting systems are appropriate in areas that like energy security they require very little infrastructure you know sewer piping or leech fields and because of that they're also cheap. Lastly they turn something that's a waste into a resource to be used. In other words they can make use of a resource human waste without inflicting damage on the ecosystem. I think that's a good way to think about a lot of our proposed solutions for more locally sustainable living now and in the future not just compost. I think it's clear that there really isn't a one-size-fits-all answer to this question which I'm finding to be the case in just about every avenue we go down. I think our culture really likes straightforward solutions like banning CFCs in the Montreal protocols has helped shrink the ozone hole which was a huge deal in the late 90s but with multi-causal problems like climate change or depending on finite races like fossil fuels we need a variety of interconnected solutions and that's too complicated to fit on a bumper sticker and thus it's hard to get across to people who have day-to-day problems to deal with and feel like they have no bandwidth for disasters looming on the horizon. It's really tough but it has been great to ride along with you in the time machine Matt and look at the at look at some of the workable compost systems in different regions of the US 50 years out. Thanks for joining us today and if people wanted to hear more about this where would they find you? You can find more of my work in writing over the Paul Pearls Almanac podcast where I'm a co-host with Andy and Elliot. If you want to learn more about the chemical and biological processes involved in composting I recently wrote an episode called The Science