reading time: 5 Session minutes
Learn more about biogas and biodigesters and how they can help you process chicken feces, from a permaculture writer Jonathan Engels.
Whenever there is a chicken, or any animal for that matter, the poop is sure to follow. While this is often mistakenly referred to as waste, the truth is that we can do a lot of very useful things with compost. Most of us know its use to fertilize crops, and it is not possible to add it to compost. These are probably the most common uses for using manure.
There are other uses as well. It’s time to look at how chicken manure can be used to produce biogas, which can then heat a home, power a generator, or even cook a meal. That’s right: chicken poop can save gas for making chicken soup.
Survey says: Biodigester
The key to converting feces into biogas is a biodegrader. Biodegraders are airtight structures that feed on organic matter, including animal dung, so that they decompose anaerobically. When a breakdown occurs, the gases are naturally released within the biodegrader, transported to the bladder, and stored for later use. The bladder can be connected to a cook stove, heater or generator to provide a clean burning fuel: biogas. Biogas consists primarily of methane, with an appreciable amount of carbon dioxide and trace amounts of other gases, such as hydrogen, oxygen, and nitrogen.
How Biodigesters Work: Belch-y Anaerobic Magic
Unlike decomposers in intact (aerobic) compost heaps, which rely heavily on a lot of oxygen, biodecomposers rely on anaerobic or oxygen-deprived decomposition. Anaerobic microorganisms (antique) is a very ancient form of life that occurred before plants released oxygen into the Earth’s atmosphere. They are still around and hungry, but they need airless homes to survive.
Underwater inside the biodegrader, naturally occurring archaea happily break down organic matter, such as chicken feces, other (including human) manure, as well as kitchen scraps. While this process is occurring, the slush material inside the biodegrader causes biogas to be produced. This same procedure occurs in swamps, known as swamp gas, and other places with waterlogged soils, such as rice paddies. It also occurs in the digestive system.
Large-scale bioanalysts: sanitation secrets
Probiotics are nothing new. They have been used in wastewater treatment plants for over a century now. In these systems, wastewater enters a treatment plant and passes through a two-digester system. The first biodegrader is used to break down volatile organic matter, and the second is used to separate the remaining solid residue from the water. The gas produced from this is used to heat the digesters to certain temperatures in order to create ideal environments—medium (86-100°F) and thermophilic (122-140°F)—for different types of anaerobic microbes to thrive. Eventually, the once-harmful sludge becomes safe and used on farmland as fertilizer.
Energy production from industrial farms: chicken tube chicken houses
With this process in mind, it only makes sense that places with a lot of stray litter—industrial farms and feedlots—would benefit. While pigs and cattle are driving the biodegradation of industrial compost, large chicken farms are now also entering the game. Not only did it provide a more ecological way of dealing with feces, but it also provides savings in the end because the birds heat their homes. In fact, energy production provides a surplus that can power a home, as well as slurry that can fertilize chicken feed farming.
Backyard Poultry and Biodigesters
The admission here is that chicken feces are not the ideal choice for digestive sweeteners. It is on the acidic side, or high in nitrogen. On the other hand, cow and horse manure is an ideal ratio of carbon to nitrogen (25:1). However, chicken manure (6:1) with bedding will turn this ratio closer to correct. Food scraps, fresh grass clippings, weeds, and green leaves are also good ratios for digestifs (and compost-making). The point, however, is that when properly balanced, a small amount of chicken manure, as well as kitchen and yard waste, will make biogas.
Make your own biodegrader at home
Smaller biodegraders can be made at home using simple hardware available at any DIY store, as well as reused materials, such as shipping drums and IBCs (International Bulk Containers). In fact, two families with small farms can team up to efficiently provide plenty of gas for two households, maintaining multiple digesters while sharing one large gas storage container.
For those interested in trying the idea, it is also possible, and inexpensive, to build individual digester systems suitable for a small backyard herd and one family’s amount of manure. These single appliances will realistically save enough gas to cook every day.
Design experiment of the C3ities solar micro-biodegrader
A small bioinfuser, also known as a “little dragon,” can be made with a five-gallon water bottle and some basic plumbing fixtures. While this won’t provide enough gas to do a lot of cooking, let alone power the heating system, it does provide the nuts and bolts of how biodegraders work. The same principles apply regardless of scale, so this is a good experiment for curious adults and science classes for kids alike. It can also be a good way to explain to friends and neighbors exactly what you do.
Small scale home biodegrader
Redirected IBC containers are great for home-domain systems. The container will have three tubes: a feed tube for adding food scraps and/or manure, a gas outlet tube for biogas harvesting, and an effluent discharge tube for catching the liquid manure you produce after each feeding. The ideal content composition inside the biodegrader is 40% organic matter, 50% water, and 10% gas headspace.
For a biodegrader to provide reliable service, gas-producing microorganisms require consistent feeding. Adding a gallon and a half of food waste, or five gallons of compost per day, realistically provides enough fuel for about two hours of full cooking time on one burner.
Many home biogas producers choose to connect two or three digesters to one large gas bladder, so that if one needs to be retrofitted, the other(s) can still supply the gas. And of course, gas production goes up without having to create entirely separate systems.
Biogas storage for on-demand use
While most of us are used to gas going in pressurized bottles, this doesn’t work with biogas. Squeezing it is very expensive and involving simple home systems, not to mention that uncleaned biogas corrodes metal cans. Industrial systems clean the gas into pure bio-methane for pressing into bottles. Home systems often use durable PVC bags.
In optimal conditions (about 95 degrees Fahrenheit), the biodegrader will produce its volume of gas each day, but obviously conditions are rarely ideal. Twenty-five gallons of biogas equals about 15 minutes of cooking time. The IBC load is usually around 300 gallons, which translates to a maximum of three hours of cooking each day, all things adaptive.
Use your own gas to cook
While biogas is clean-burning and easy to produce, it does require specialized or appropriate equipment to use it. There are specific biogas cooktops, which require a larger orifice than high-pressure gases but do not require the ventilation that those gases use. These cooktops are available online for under $50.
Otherwise, typical gas appliances can be converted to work with biogas, providing virtually free energy for years to come. Propane, butane, and natural gas burners can be easily changed to operate on biogas by removing the pressure restriction pin and capping the air inlet on the gas feed. This allows things like barbecue pits, propane generators, and gas heaters to be converted for biogas disposal.
Complete biogas systems are available for purchase
For those who aren’t exactly the DIY types but are interested in using biogas, complete home range systems are available for purchase, which simplifies the process and provides peace of mind. HomeBiogas and Puxin are two companies that sell off-the-shelf systems, including biogas appliances to use with them.
HomeBiogas 2.0 System
For a more in-depth investigation of biogas production and autonomous systems for non-professionals, The Complete Biogas Handbook is a sensible next step. The Biogas Handbook focuses more on large biogas plants and the serious science involved on an industrial level.
Jonathan Engels Traveler, writer and botanical gardener. Born and raised in Louisiana, he has lived as an expat for over a decade, working in nearly a dozen countries, and visiting dozens of others in between. His interests include sustainable farming, cooking and music. More of his work can be found at Jonathan Engels: A Life About.