In the book Another Kind of Garden, the methods of Jean Pain are revealed. He spent his entire short-lived life studying brush land and forest protection, specifically fire prevention, alongside his wife Ida. These studies led to an enormous amount of practical knowledge for composting, heating water, as well as harvesting methane, all of which are by-products of maintaining a forest or brush land with fire prevention techniques. While this knowledge is applicable in many instances, it is worth remembering that the root of all of this knowledge lies in forest preservation. All of the activities described below are by-products of that process. The book goes into detail with the economics of such an operation. I will focus on the applications.
“Just think that it is a question here of trying to safeguard 1 000 hectares, with success guaranteed, that 16 people will directly find a well paid job, that the equivalent of 480 000 liters of motor fuel will be produced each year, as will 6 000 tons of this precious humic improver which has great value as a fertilizer, and which could even enable reafforestation of the same number of hectares in the same year. ”
Brushwood Composting Overview
To first understand the process of composting brushwood, Jean Pain set about creating a heaping row of chipped material. By chipping the brushwood into 8mm pieces, you can accomplish the fastest rate of decomposition. Larger chips and even small branches will work just as well, but with a longer processing period. This “drawback” could be used as a benefit, keeping the hot water running longer. There is little difference in temperature for chips of most sizes, 58-60C. The ideal weight is 520-550kg/m3 of chipped brushwood material.
Once you have your chips, pile them 1.6m tall with a base of 2.2m. The pile can then be drawn into a long mound if more material is available. Wet the pile to saturation as you build it; you can dig a small gully to collect and recycle water that drains through. You want your wet chips to be saturated to the point where a tight squeeze only produces 1 or 2 drips of water. When you have finished your pile, cover it with 2cm of leaves, sand, soil, or a previously finished batch of compost. Lastly cover it with large boughs or a tarp to keep the moisture constant and the elements out. In three months this will be a rough mulch ready for surface application. Two months later it will be a thick leaf mulch that will incorporate well into the soil, and 1 month longer would give you a wonderful humus. This process produces no bad odors. Typically it will have a sweet earthy smell for the entire production cycle. You are not required to turn, or add any inputs to the pile as it decomposes. It is a set-it-and-forget-it system.
Humus – The End Product
By allowing the system to go a full 6-7 months, humus is created. Humus is the most basic particle of soil you can get. It is the one of the hardest, and therefore last, of the particulates in the soil to be broken down. It is brown to black in color and nearly insoluble in water, which it also holds onto with its large surface area. Chemically it is mostly carbon, about 55%, and lot of nitrogen, 3-6%. This ratio usually settles somewhere around 10:1, but varies over the process. The rest is made up of minerals and such that the plant and soil life can utilize. This creates a very rich environment for a lot of micro organisms to live, which leads to even more fertility in the soil through the interactions between the roots of whatever is growing and the micro-organisms living in the soil.
Most compost piles get to around 60°C; brush land compost is no different. If you run a polyethylene pipe through the brush compost as you are building your pile, you can harvest hot water. An open loop system, where the input is your tap water, and the output is your hot water is a simple straight forward design. Jean Pain found that a 50 ton pile of brushwood compost could provide 60°C tap water for six months at a rate of 4 liters per minute. Later experiments with a 120 ton pile showed that a pile of sufficient size would be able to produce 58°C water at several liters per minute over 18 months. A closed loop system, with a pump or thermo siphon where applicable, can be used with a radiator to provide space heating. The addition of a radiator will not overly adversely affect you ability to make hot tap water. The radiator should be regulated by a thermostat so as not to leech excess energy from the pile. You would quickly feel the effects; Jean Pain noted an unregulated 50 ton pile connected to a small (12m3) shed kept it at an unbearably hot temperatures all winter. The extraction of this heat can also regulate the rate of decomposition.
Many applications may require a pump, but a thermo siphon can also be used when applicable. A thermo siphon works by placing the compost pile lower than the radiator which allows the heated water to gravitate up to the radiator while the cooling water in the radiator tends back down to the heat source. The thermo siphon moves less heat, but can be useful nonetheless; especially since it uses no energy. To heat larger spaces, buildings, or swimming pools, a pump will be required.
To extract the heated water the polyethylene pipes must be buried in the pile. Jean Pain’s experiments show no variance in production in any of the arrangements – horizontal, vertical, or spiral. The set up and take down of them is different. The horizontal placement tends to settle unevenly, making the removal of the finish product more difficult. The vertical placement does not suffer from settling issues, but is more tedious to set up initially. The spiral configuration seems to be the easiest to set up and take down. First build a pillar of compost material, then wind the poly pipe around it. Bury the pillar inside larger and larger piles of compost material, stopping to wind more poly pipe as you go. Even when this settles, the pipe can be easily collected by digging out and unwinding – the exact reverse of the set up process.
Directly heating air with a compost pile is also possible as Jean Pain shows. By burying a 125mm air duct in a 50 ton pile, a 12m3, uninsulated forest shed can maintain a constant temperature of 52°C for 8 months. This system used a thermo siphon effect, the hot air coming in at the ceiling of the shed, and the cool air falling to the floor and exiting through a pipe there.
We can go beyond just some basic heat extraction by pumping water through our compost piles and harvest methane gas almost as simply. When looking at 10kg of chipped brush matter, you can expect to extract 2m3 methane gas, which has the energy equivalent to 11,000 kilo-calories. In practical terms it is the equivalence of 1 liter of high grade petrol. After the methane is harvested, 8.5kg of compost mass remains. This is a perfectly usable form of completely composted humus, ready to be integrated into the soil. 10kg of chipped matter gives us 1 liter of petrol and 8.5kg humus! Even this part of the cycle, which is still very simple will produce no bad odor. The finished product will have a heavy carbon smell to it at worst.
When constructing a pile that will harvest methane you need to place a sealed container, in the case of this study a 25m3 cube, full of already soaking wet composted material inside a larger 80m3 pile of fresh organic brushwood matter. To construct this pile, you make a flat base for the methane cube to be placed on, fill the cube 3/4 full with compost and fill it the rest of the way with water. Seal the container completely except for one tube the methane will travel through. Next wrap poly pipe around the cube as the first layer to be used for heating water. Continue to cover the center cube and wrap more layers of poly pipe until you reach the desired size.
Hook up your hot water pipes as you will and connect the methane container’s tube to a bank of deflated inner tubes. The more water you cycle through the system, the cooler you will keep the center mass. This will only affect the time it takes to harvest the methane and break down the fresh material; it will not affect the quality or quantity of products. To prolong the process as long as possible, to keep a house heated with water for example, you can keep the center mass as close to 36°C as possible. This is the coolest temperature methane will be produced at. The outer layers will need to reach at least 50°C to decompose properly. Allowing the core temperature to rise higher, to near the normal 60°C will hasten the methane harvest time. Under these conditions you can expect 2000m3 of methane over a 4 month period. By keeping the temperature at a cooler 36°C the process will provide the same 2000m3 of methane, but over a 6 month period. 1 cubic meter of methane has an energy potential of 10 kwh which can produce 4.5 kwh of electricity. This methane is stored safely under atmospheric pressure in the tire inner tubes, but can be compressed with a compressor and a high pressure storage canister. Once compressed, it has all the same uses as other compressed gas, including running diesel engines with a slight modification to the carburetor.
The ideal schedule for producing methane, as well as hot water and humus, is a seven month process. Step one is an initial two month pre-compost; a simple pile or row where hot water can be harvested if desired. After pre-composting you can pile the resulting mass around the methane tub for four months of methane and hot water harvesting. This will generally coincide with your winter season. In the spring, a final one month aeration composting will give you humus ready for that year’s application in the garden. You’ve gone from brushwood clearing forest protection to hot water, methane, and a rich fertilizing humus for the soil in seven months
Use of Products
There are a variety of products produced from this composting technique. The thick mulch produced after 2-3 months can be used to prevent evaporation to the extent that no additional watering was needed all summer at Jean Pain’s farm in the Var forest of France. The mulch should be applied heavily at the beginning of summer, about 7cm thick. Forest restoration once again comes into play; Jean Pain harvested pine needles from the forest, which were a perfect tinder for forest fires, and piled them on top of the already thick mulch to another 10cm thick. The pine needles help keep critters from making nests in the mulch, keep the soil shaded, cool, and allow for good air circulation. Straw, leaves, etc., will have the same effect, sans discouraging critters, and can even be integrated into the soil, whereas the pine needles need to be removed before they decompose into the soil to prevent acidification. Both the brushwood mulch and the cover layers should extend about a meter out from the edges of the garden to stop evaporation around the edges.
By allowing the brushwood to compost more completely, over 4-6 months, as with a methane or hot water harvesting system, you will end up with a leaf-like mulch that will easily crush between your thumb and finger when squeezed. This can be applied as needed, usually yearly, and will integrate fertility into the soil over the year. This is also what will be placed into the center methane harvesting container.
A final stage of composting can be added at the end of the process. By allowing the compost that had surrounded the methane tank to compost for one more month after it has been removed from the system will increase aeration. The end product will be a rich humus.
All of these soil products can keep indefinitely. The end result of one year’s composting can easily be used in the next years methane harvesting. These products also provide a great balanced nutrient content for your soil. This can be best utilized by planting a number of different species that can take advantage of the multitude of nutrients available. In more traditional gardens you can crop rotate to make sure all the nutrients the compost provides get used over a number of years. Jean Pain was able to grow tomatoes to a height of 2.5m that produced 20kg of fruit per plant without additional nutrients beyond the compost.
Thicket management can be done on a commercial scale at a profit, create jobs both directly and indirectly through the markets created by the outputs of the system, and most importantly it can save forests from wildfire. Jean Pain lays out a grid of 40 hectare zones. 25 zones in all with each one being harvested every 8 years. Each 40 hectare area provides 1600-2000 tons of brushwood, about 50 tons per hectare. The land is not totally cut down — but just enough to prevent fire from easily spreading, and will regrow within the next 8 years, before the next harvest cycle. This system also gives wildlife a more permanent place to live, as well as offering ample areas to move to when that section is up for harvest.
All the material should be chipped on site, and then transported to a central processing location located within the grid. This is key to reducing the overall impact on the land, as well as to provide the most energy efficient layout for the operation. You can easily notice the orders of scale on the trails that mimic things in nature, like leaf veins. This layout, coupled with Jean pain’s chipper and 4 unskilled workers, will be able to harvest 1 hectare a week, which is about 80m3 of material. This is the same amount of material used in the methane harvesting experiments, roughly 50 tons.
Once the chips are back at the processing site, they must be impregnated with water. While soaking them down with a hose works fine, it specifically takes 700 liters of water 3 days to be absorbed by 1 cubic meter, about 550kg, of chipped material. Again if you utilize a soaking system, dig a gully to trap and recycle water that will inevitably run off. Soak the pile down every 6-10cm to make sure you have an even water content. Your target will be 40-50% humidity under your covered pile. Test by squeezing the compost — it should drip just 1 or 2 times.
Jean Pain goes into great detail over the economics of such an operation. The system provides a safety measure against forest fire, provides jobs, methane, humus, and is a sustainable practice. Once the initial operation is under way, 12% of the methane harvested by the site will go back into the site. Overall 26% of the total caloric output of the operation will be reinvested to maintain the operation and keep it under way.
While Jean Pain’s 50 and 120 ton experiments may be a bit large for a household or small farm, the techniques employed can be used on scaled down projects. A 55 gallon drum (208L) at the center of a 1.5m3 pile is just scaled down to one fifth of Jean Pain’s 50 ton experiment. This should produce about 20m3 of methane. While not nearly the 2000m3 Jean Pain harvested, 20m3 of methane is still the equivalence of 90kwh. The compost itself, the land management, and heating water are also all still valuable outputs a farm of any size will appreciate, even without scaling a system up to produce large amounts of methane.
To give some perspective of how large a resource is not being taken advantage of, Jean Pain illustrates the outputs of some of the world’s forests. The Var Forest includes 400,000 usable hectares. This would annually produce 2.4 million tons of humus, 192 million liters of petrol equivalent in methane gas, and create 6,400 jobs, not including any created downstream of the resource generation. These numbers pale in comparison to those that would be created from the Belgian Forests 192,000 hectares, the French Forest’s 14.5 million hectares, or the California Forest’s 17 million hectares. Just these forests add up to 42,000,000 hectares of exploitable land. It is also worth mentioning again that the management of these forests will result in controlling wildfire. This responsible management will lower costs associated with fire prevention and damage repair as well as providing new sustainable resources and jobs.
The book, which has been out of print and hard to find for a number of years, can be viewed online here (PDF).