Imagine being able to heat water, buildings, and greenhouses using energy captured from compost without buying or burning any fuel while creating a by-product that is worth more per ton than coal. If you’d like to stop imagining and hear about people who are actually doing this today—while learning how you, too, can put compost power to work—keep reading.
Compost-powered, combustion-free energy is beyond just a fantastic imaginative possibility. Modern innovations around an old idea have made compost power a reality that many people are putting to work around the world. I wrote the book “The Compost Powered Water Heater” to give you everything you need to know to take the first steps toward applying compost power to your heating and hot-water needs, whether you are a homesteader, a landlord, a farmer, a commercial compost producer, or anyone else who needs heat and is interested in producing compost at any scale.
The book gives a broad and deep introduction to compost-heat recovery at all scales. You’ll learn about modern engineered approaches of extracting heat from compost systems using animal manure and food scraps as the main input, as well as time-tested low-tech methods that you can build in one day in your own backyard out of wood chips and sawdust.
You could think of compost power as hot shit, but there need be no obnoxious odors or manure involved. In fact, compost-heat-recovery systems often have the added benefit or reducing or eliminating odors that might otherwise be part of the compost production process.
In short, rot makes hot. And at present there are people all over the world who seem to have collectively scratched their heads at the same time and said, “Let’s use that compost heat. Why not?
In recent years the resurgence of organic farming in Western economies has driven investments in expanded production of high-value compost. Cost increases for conventional fertilizers and shortages of supplies like potash have driven up the demand and prices for organic compost. Certified-organic fertility cannot use the chemically derived fertilizers of conventional agriculture that have been common during the past half century.
The corresponding investments in organic compost production have also sparked recent innovation on compost-heat recovery, particularly in the past decade in Vermont, Canada, and Germany, where several compost scientists, engineers, and tinkerers have, independently of one another at first, but eventually through collaboration, developed several economically viable methods of recovering predictable amounts of heat from the composting process.
How It Works
So how does compost heat really work? Briefly, any biomass material that has enough air and water present, and enough thermal mass, will naturally go through a thermophilic composting process, otherwise known as rotting. The microbes that produce heat through the composting process need food, air, and water, like any other living organism. Even aside from our ability to use that energy, the heat has multiple benefits, such as eliminating pathogens to produce healthy soil.
French farmer Jean Pain developed a simple method of capturing large volumes of heat and hot water from his composting mounds of wood chips in the 1970s, but the concept was all but forgotten after his death in 1981. About ten years ago a handful of innovators and tinkerers, operating independently of one another for the most part, developed promising approaches and started to revive Jean Pain’s legacy. These individuals eventually formed networks of permaculture practitioners, engineers, renewable-energy experts, and compost scientists in Vermont through CompostPower.org, Highfields Center for Compost, Yestermorrow Design/Build School, and Agrilab Technologies.
A predictable and engineered approach to compost-heat recovery has been developed by Agrilab Technologies and Joe Oullette of Acrolab Ltd, known as the Isobar system. The system works by pulling air down into the floor of a compost-production area, actively aerating the compost; this eliminates the need for stirring and tumbling of the material. The hot air is then run through a patented heat exchanger, producing steady volumes of 120°F to 140°F water which can be used for space heating, process heat, or wash water. The Isobar system in general pays for itself in less than five years and is ideal for commercial compost producers and farms with more than 100 cows or the equivalent amount of manure or other compost feed stocks such as food scraps and forest residues.
In 2009 the collaborations of several individuals in Vermont became more formalized through an open-source research project known as the Compost Power Network (CompostPower.org). This network has built or assisted with dozens of demonstration systems across New England and beyond, including successful experiments at a monastery in Siberia, a system integrated into a greenhouse at the University of Vermont (UVM), a system heating a college dorm at Evergreen State College in Washington State, and a project at an eco-village near Santiago, Chile. Many of these projects were used as training programs through workshops that I taught at Yestermorrow Design/Build School, UVM, Evergreen State College, and other venues.
By 2013 CompostPower.org had assisted with dozens of projects around the world, and Agrilab Technologies had reorganized with new leadership and an expanded team of people from the Compost Power Network. As of this writing Agrilab Technologies has designed and begun offering a containerized “plug ’n’ play” version of its system, including lease-to-own financing.
This resurrection of Jean Pain’s methods, along with development of entirely new approaches like Agrilab’s Isobar system, has created exciting new momentum. This momentum has also taken root across the globe with many people learning from the open-source experiments of others, finding ways to capture heat from compost.
Folks are Jumping On Board
Today there are many working examples of homes, greenhouses, and farms that have used compost-heat-recovery systems alongside existing heating/hot-water systems, reducing or eliminating the need for fuel combustion. These systems range from simple low-tech designs made mostly of wood chips and sawdust, to large-scale engineered systems at farms and compost-production facilities.
I have been involved with compost-powered heating systems in dozens of states across the United States as well as Quebec, Ontario, Siberia, Norway, Chile, Argentina, and many other locales. Of course many of the first attempts for various projects were not totally successful, but in recent years best practices have been fine-tuned to create predictable and economically viable process.
In 2006 Agrilab Technologies installed the first of these systems, at Diamond Hill Custom Heifers in Sheldon, Vermont.The system generated more than 200,000 Btu/hr continuously, and the farm gained tens of thousands of dollars in compost sales annually. Today, there are several Isobar systems in successful operation in VT, NH and NY that are each capturing an average of 1000 btus/hr per ton of compost continuously during an 8 week batch cycle. This amounts to more than 1.4 million btus of thermal energy captured per ton of compostable materials processed, which is worth about $45 in terms of hot water fuel savings. Forty five dollars in energy value per ton of compost produced is a very large value. A ton of high quality coal currently costs $40 by comparison.
Jasper Hill Farm in Greensboro Vermont heats a large winter greenhouse and large volumes of wash water with their Isobar system. The University of New Hampshire’s organic dairy farm and Sunset View Farms in New York, use their Isobar systems primarily for making combustion-free hot water. More information about the Isobar system including “How it works” videos can be found at www.compostpower.org and www.agrilabtech.com.
As of this writing collaborative projects are under way among most of the previously mentioned people and organizations, including new market-ready systems being sold with bank-approved financing, and new research being undertaken. Compost power is now a market-ready and economically viable concept, and there is tremendous opportunity for innovative applications of it.