 What's that smell? That sulfur-y swampy stink? It's Methane, and this is the Lotech Podcast. Hello and welcome to the fifth episode of our new series, our season. I'm Scott Johnson from the Lotech technology institute, your host for podcast number 76, coming to you on February 9th, 2024, out of the Lotech recording booth. Thanks so much for joining us today. We're continuing our tour of Cooksville in 2100, and today we are exploring the world of Methane. And a quick note here at the top. This weekend, that is the 9th, 10th, and 11th of February, we'll be at the Wisconsin Garden Expo in Madison, where I'll be giving presentations on worm composting, gardening in a changing climate, and four-season gardening in Wisconsin. Join us if you're in the area, but if you can't make it, don't worry. I'll post the presentations to the podcast feed as the next few episodes. Also, don't bother following us on Twitter, X, or whatever it's called right now. 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If you've ever let a compost pile sit too long before turning it, passed by a cow lot, or opened a garage can, excuse me, a garbage can on a hot day, you've probably smelled biogas. Once upon a time, this was called marsh, swamp, or bog gas, and was naturally occurring as a source of methane or, chemically speaking, CH4. Although methane is colorless and odorless, what you're actually smelling is another byproduct of anaerobic, that is oxygen-free decomposition of organic materials, and that's hydrogen sulfide, which is H2S, often called rotten egg or smell. Indeed, both marshes and our own intestines are teaming with methanogens, a family of microorganisms that convert decaying organic matter into stinky, flammable gases. Methanogens are a key link in the carbon and hydrogen cycles on Earth and can be tapped into for human friendly energy and global cooling. Over 50 species of microscopic spherical or rod-shaped organisms digest carbon dioxide and hydrogen into methane and water. So that would be CO2 plus 4H2 becomes CH4 and H2O. Free oxygen or O2 doesn't come into this equation. In fact, these methanogens will die in the presence of too much oxygen, and that is why they are in marshes where oxygen has been depleted out of this stagnant water. They also thrive in extreme environments, such as mid-ocean ridges beneath the sea, miles under ice sheets in desert soils, and even on Mars. They can function in extreme heat and cold. Unlike natural gas, which is ancient methane trapped and concentrated beneath the Earth's crust, biogas is a renewable resource and does not introduce new carbon into the atmosphere. A tree growing in a swamp is absorbing atmospheric carbon while it lives. That would be 6CO2 plus 12H2O becoming C6H1206 plus O2 plus H2O. When the tree dies, its cellulose can rot, turning back into carbon dioxide, water, and other components when it's above water. But the carbon released in a tree's decay is just returning to the atmosphere, and the life cycle emissions are essentially zero. But if that tree were to collapse and sink below the water surface of the marsh, methanogens would take over creating methane out of the organic material. When I lived in Alberta, Canada near the oil patch, I'd drive by natural gas wells where they were flaring off huge volumes of methane. I always wondered why burning was better than simply releasing the methane. It turns out that the end result of combustion produces less of a greenhouse effect than raw methane. But the real crucial difference between natural gas and biogas is its impact on that same atmospheric greenhouse effect. Now, methane is more than 28 times more potent to greenhouse gas than carbon dioxide. Luckily, it degrades in one or two decades compared to carbon dioxide, which can hang around for up to a millennium. Stopping the use of fossil methane in the mid 2000s helps stabilize globalized temperature rise. Additionally, by avoiding anaerobic decomposition, we have also been able to decrease atmospheric methane. Yet another way we reduce the greenhouse effect is counterintuitive, burn that methane. Potent methane is turned into less warming carbon dioxide when burned. That's CH4 plus O2 becoming CO2 and H2O and heat, of course. It turns out that at a larger scale, the same principle that an adolescent boy uses to light his flatulence on fire helps stabilize global climate and provide heat for cooking and power for machines. Don't worry, I have no sound effects for this portion or really this entire episode. Generation. So as with all our power sources, we try and use methane in the same location as its production. Although it is a flammable gas like hydrogen, it is an unwanted byproduct and really only used to combust it before it goes into the atmosphere. We use significantly less methane than hydrogen. Where we have processes that create large amounts of decomposing organic matter, we try and find a way to capture the ensuing methane and put it to use. We'll visit our composting operations in another episode, but in many cases we try to avoid anaerobic digestion in the first place and limit methane production except where it's specifically useful. The heart of any system is the methane digester shown here if you're watching us on YouTube. The process starts with so-called waste collection, be it animal manure, green material or other organics. This feedstock may be pretreated by chopping it up and cleaning it up and leaving it to rest, or it can be fed right into the digester. And now these digesters come in many shapes and sizes, but they all consist of basically an airtight container with a minimum of three ports intake, biogas and outtake. Some digesters have a flexible top allowing for the expansion of methane gas and inputs. But as rubberized materials became more difficult to source around mid century, most digesters moved to a solid vessel format, as high pressures are no problem for methanogens. Feedstock is introduced through the intake, which is designed to exclude as much oxygen as possible and maintain pressure. The existing reservoir of digesting materials contains the bacteria or methanogens needed to break down the feedstock. The more regular the feeding, the better for the system. As methane is produced in bubbles to the top and is drawn out through the biogas port. Depending on the size and format of the system, it can be stored or used directly as discussed in a few minutes. Now, as the materials are digested, they're removed through the outtake, which is similarly designed to avoid introducing oxygen or losing pressure. Both liquid and solid fractions are removed for use as fertilizers. All digesters have pressure valves and alarms to avoid too high pressures and the uncontrolled release of a flammable gas because that could be dangerous. Now digesters come in a variety of sizes and complexity. We share a small household system smaller than an old Volkswagen Begadol with our neighbors. Stoughton just down the road has one of the largest digesters in the area measuring hundreds of feet across, which I'll discuss in a second here. But our system is fairly simple with hand operated in and outtake doors. But even these systems have a pressure regulated biogas port to draw out methane at relatively low pressures to avoid dangerous buildup. Midrange versions of these systems have manual cranks to operate drive screws to push solid effluent towards the outtake. Stoughton system is large enough to use a hydraulic or otherwise powered in and outtake ports as well as tighter regulations on biogas draw off because we really don't want to build a pressure there. Many of the larger systems have even internal arms to circulate material for more efficient digestion. Carbon dioxide production is significant at 40 to 60% of the total gas volume. This means the collected gas is only half combustible at home. This is really no problem. And we just push more gas through large reports to get enough material flowing through to heat a pot on a stove. But for factories and other more exacting uses, the CO2 must be removed. One process is pressure swing absorption or PSA. The one in Stoughton is older and only uses four pressure vessels. Newer ones have nine. These are partially filled with carbon dioxide absorbing material. The biogas is pumped under pressure, CO2 is absorbed and the methane is released and then the carbon dioxide is off-gassed. This takes time and a simple cycle uses four tanks each staggered so that a constant supply of methane is produced. More efficient and effective cycles use up to nine tanks with more complex cycling and refining of the gas I'm not going to get into. Another process, water scrubbing relies on the ability of water to better absorb carbon dioxide than methane. Pressurized biogas and water are sprayed into a pressure tank and mixed, allowing much of the CO2 to be absorbed by the water. Methane is drawn off and the water is routed to another tank and the carbon dioxide is released. While less efficient, water scrubbing is more flexible than PSA, so the end use determines really which of these scrubbing methods is used. So now let's talk about storage. As with hydrogen and our other fuels, we use our methane as close to its point of production as possible and attempt to minimize storage. Luckily, as flammable gas, some of the same options used for hydrogen can be converted to store biogas. But unlike hydrogen, methane liquefies at only 260 degrees below zero Fahrenheit, that's 162 centigrade, that's compared to hydrogen's liquefification point of negative 487 Fahrenheit or 253 Celsius. This makes a denser fuel possible, even though frozen or this type of methane is almost never used. The simplest systems do not really store biogas outside of the digester. An isolated farm that uses biogas for cooking, heating or powerage generation simply draws gas out of the gently pressurized digester through a regulator. Cooking on a stove stop, for example, needs about a half a therm an hour and a therm is 100 cubic feet, that's 2.8 cubic meters of gas at atmospheric pressure. A therm of gas is easily created each day with a small digester handling the approximate leaves, in this case 21 gallons or 80 liters of manure from their four cows. If the pressure in their system, our neighbors rises to high, it's bled off and burned to heat water for space heating in the winter or other energy uses in the summer. Simple systems often make use of legacy propane tanks, which are discussed in more detail next time or next time we come back to 2100 because these tanks are more typically used for compressed air. The only difference is that biogas is filtered through steel wool to remove any sulfur, limestone crystals to remove CO2 and silica to remove moisture before they're being bottled and stored. When biogas is stored in the same pressure tanks that have been developed for hydrogen, we get less energy than a similar volume of hydrogen. Small scale producers and users of biogas typically use low pressure tanks that are rated to over 5000 psi or 350 bar. Compressed natural gas essentially is stored at 3000 psi or 200 bar. The standard five gallon or 20 liter tank holds up to a thermon half of natural gas and this would dry about eight loads of laundry in an early 2000s natural gas dryer equivalent. Although this would be about 45 kilowatt hours of energy because raw biogas is approximately half CO2, the capacity is diminished by about 50% without scrubbing. You can compare this to 30 kilowatt hours for the same tank with hydrogen at 5000 psi or 350 bar. Workshops and factories that use biogas often use scrubbers to store pure methane in a series of linked or plumb together 50 gallon, 200 liter tanks. Each tank can hold up to 450 kilowatt hours worth of methane if scrubbed clean of carbon dioxide. That's quite a lot. Some vehicles are also designed to run on biogas, especially tractors and machinery on farms where biogas is more readily produced and vehicle cargo space is not an issue. Although these vessels typically measure fuel use by the hour, to give you an idea of an equivalent, a car going 100 miles or 160 kilometers would need 15 pounds or about 7 kilograms of methane or double that for unscrab biogas. Because this would require two 5 gallon or 20 liter storage tanks just for pure methane, biogas is impractical for passenger vehicles but perfect for tractors, loaders, and other utilitarian equipment in isolated areas. In a few instances, liquefied biogas or LBG is used as a fuel. By chilling the biogas down to negative 260 degrees Fahrenheit and putting it in a super insulated tank at regular pressure, LBG can pack a large amount of energy into a small space. Although we do lose about 14% of the input energy to run the compression and freezing equipment. This is mostly used for long distance transportation on trains and cargo ships, which traverse long stretches between stops using vaporized natural gas escaping from the super cool tank. A gallon of LBG contains the same energy as about 82 cubic feet, that is about 0.82 therms, and have to dry four loads of laundry, which has become our standard comparison for biogas power apparently. So now let's turn to how we use biogas. It's not to dry laundry. A century ago natural gas we used for industrial processes such as fertilizer production, electric power generation, residential and commercial heating and cooking, and transportation in descending order. Today's biogas is used for, in descending order, high temperature industrial applications, transportation, cooking, heating and power. We'll look at each of these in turn as we see examples of large and small systems. Even in small communities, neighborhoods, or even individual households, most have at least access to a simple biodigester to handle organic waste. Although compost could also take care of all this material, in northern climates especially, a source of compost or excuse me combustible gas adds a welcome diversity to energy mix. These small digesters work in the winter and have the simplest input and output hatches and a pressure-containing vessel to hold methane at low pressures as we talked about. Most neighborhood scale units have an automatic compressor system attached, and this is used to fill small tanks for local use, largely for cooking and heating. Isolated farms are a big producer and user of methane. Gone are the confined animal feeding operations known historically as CAFOs of a hundred years ago, but even our smaller dairy and beef farms create a large amount of manure in the winters. During the summer cows are typically in larger pastures where their droppings are aerobically broken down in the fields, but when confined to smaller yards and barns for the winter though cows produce concentrated by-product which can be controlled or are collected into large sealed domed tanks where methanogens can go to work. Methane gas rises and the water and solids sink. The gas can be piped to the farmhouse now for heating, hot water, cooking, transportation, and if all those needs are met small energy generators can be run for electricity. The resulting liquid and solids can then be drained from the tank and spread in the fields as fertilizer. It's a closed loop. Many farm tractors and machines have been engineered to run on methane stored in large tanks that would be awkward for use in passenger vehicles, but not a problem in these utilitarian vehicles where locally generated mobile power is needed. Some operations use the methane to heat greenhouses which has the added benefit of increasing the carbon dioxide level which further benefits plant growth because they like that carbon dioxide rich environment. Some of the largest users of methane are industrial workshops where they fuel metal smelting and other high heat processes. These rely on large predictable feedstocks and they've also invested in scrubbers to provide pure methane from the digesters. Compact, large communities mostly concentrate around legacy cities. The nearest area for us is the Chicago area. These produce tons of organic waste from humans, another animal manure to yard, garden, and kitchen waste. In return for supplying these large digesters the community then gets compost back and in some cases a share of the methane for local use while the factory uses the majority of the methane for production. Excess heat is often shared in densely built communities as free winter heating which is going to come into play in another episode when we talk about that. An additional source of methane has been legacy landfills which continue to produce a small amount of methane even a half a century after they were shut down as part of the closed loop economy. Outside of densely populated areas workshops and factories work in concert with farmers to collect animal manure and other green materials to feed their digesters. Other large users include long distance transportation in isolated areas. Although hydrogen can also be used in these contexts, some container ships and isolated train routes use methane as a fuel also. In the next episode we're going to be taking a quick detour to talk about gardening in a warming world. A talk recorded at the Wisconsin Garden Expo so stay tuned for that. That's it for this week. The Lotech podcast is put out by the Lotech Technology Institute. The show is hosted and produced by me, Scott Johnson. This episode was recorded in the Lotech Recording booth in Cookville, Wisconsin. Subscribe to the podcast on iTunes, Spotify, Google Play, YouTube and elsewhere. We hope you enjoyed this free podcast. If you'd like to join the community and help support the work we do please consider going to patreon.com slash Lotech Institute and sign up. Thank you to our Forrester and Land Steward level members, the Hambuses for their support. The Lotech Technology Institute is a 501c3 research organization supported by members, grants and underwriting. You can find out more information about the Lotech Institute membership and underwriting at LotechInstitute.org. Find us on social media and reach me directly. I'm Scott at LotechInstitute.org. Our intro music today was 50 over the speed limit off the album Power Pop by Halizna, that song in the public domain. 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