Living in southern France, Jean Pain developed a self-sustaining ecosystem in the 1970s that supplied his home with 100% of the energy needed.
He built a 50 tons compost mound from chipped wood – brushwood that had to be cleaned out to lower the risk of forest fires. Heat exchanger pipes were buried in the heap while it was built. According to the book written by his wife Ida Pain about their experiments this pile was able to heat water at a rate of 4 liters per minute from 10°C to 60°C, and its power did not degrade within 6 months. The life time of one mound was about 18 months.
This translates to a power of about:
(60 – 10)K . 4,19 kJ/kgK . 4kg / (60 seconds) ~ 14kW
or an energy of
14kW . (6 . 30 . 8)h ~ 20,2kWh (in 6 months)
… equivalent to our yearly energy demands for room heating and hot water.
Jean Pain’s ideas seem to have ‘gone viral’ in the past 5-10 years. Since I have read about his compost pile the first time a few years ago several epigones have popularized his ideas and started consulting and support for such projects. Here is a German and an American initiative.
Jean Pain also generated gas for cooking, and as fuel for his car motor and his electrical generator: A sealed vessel filled with pre-fermented compost was buried in the mound in order to produce gas. Jean Pain stored the gas in tire tubes.
The final remainder of the mound was used as manure and mulch in his garden – he was able to grow vegetables like eggplants without watering.
Pain was an autodidact and he developed and built many machines himself, as the chipper that was required to generate very fine-grained chips of wood (he was awarded a prize at an agricultural trade fair for this invention), the electrical generator, or the compressor used to fill the tubes.
According to these videos about Jean Pain it takes 1 hectare of forest 8 years to produce that much brushwood. So 8 ha would be required per home. A group of people worked for a few days to collect the wood, and 500 liters of fuel are burnt when chipping the wood. The pile needed 20 tons of water to get going.
Given today’s building standards one might conclude that you better use the fuel burnt on chipping directly. Looking at that group of hard-working people I think of aging home owners who want to replace their biomass-fuelled heaters by something more convenient. But these are not the essential points in my opinion.
Jean Pain’s method perfectly matched his era – after the oil crisis – and the heating demands of a standard house in Southern France at that time. It matched his personal convictions and talents, and his profession as a forester. And his wood was for free.
I can relate to this although or because our own solution is very different. But I know what it means to be driven by the quest for self-consistency in your life-style choices, your hobbies, and in the way you work.
Our heat pump system seems to be natural fit for those living fairly close to renewable sources of energy, such as wind power in Eastern Austria or Northern Germany, and whose premises don’t allow for building traditional heat sources for heat pumps easily. In contrast to Jean Pain’s pile a heat pump is attractive for those who just don’t want to deal with processing and storing wood logs or pellets (but who are quite interested in monitoring and control as a hobby, way beyond economical necessities). This is a personal choice, but the more rational, the less wood is available within a certain distance from your home.
I believe the best way to judge such solutions is to ask: What would happen if everybody else – at a certain time, within a certain radius – would do the same?