We are actively looking in to designing a Community Supported Energy system here in JEfferson County Wisconsin based on a wood chip gasifier powering a small co-gen unit providing roughly 30,000 kWh of electricity and enough BTU’s to heat 10,000 gallons of water for tilapia aquaponics similar to what Growing Power of Milwaukee is doing. To that end I spend alot of my free time researching the myriad aspects of that system. Of late I am focusing on a working the fuel source into the site plan, my thoughts are beginning to coalesce around using willows on a Short Rotation Coppice plan – the willows would then be chipped or pelletized for use in the gasifier.
I found a short Power Point from the Baltic university that has some great shots of willows being grown for coppice. VERY industrial, but how cool is it to see perennial carbon crops being harvested by combine rather than GMO corn?
Now for the Math Fun:
A hectare is just shy of 2.5 acres, so translated to Ameri-speak that is roughly 60,000#’s per hectare on a three year rotation – 10 tons/acre/year. 1-2 acres so planted would likely run one of our gasifiers for 2000 hours (50 weeks @ 40 hours/wk using 10#’s/hr), but I would rather see it in a mixed planting as windbreaks around CSA food gardens in an integrated Energy/Food farm. Using a 10′ wide windbreak dividing the gardens into .5 acre plots one could sustainably grow 15 tons of biomass annually on the windbreaks of 4-5 acres of cropland. For ease of reference 7 acres could produce about 100,000#’s of potatoes equating to roughly 43 million calories at the yields I achieved this past year. Of course I would never plant that much of one crop!
The point is to show the possibilities of using about 3-7 acres of land when combining food and energy systems into a permaculture plan specifically designed to produce significant surpluses for the community. The equipment to make the pellets for the gasifier could also be used to convert virtually any carbon source into pellets using a hammermill to break it up into little bits first. If you make ethanol on site with the waste heat from the gasifier using various sugary cover crops in your rotations, some of the dried distillers grains not used for the Tilapia can act as the binding agents for the pellets.
7 acres producing 5 tons of Tilapia, huge amounts of vegetables, ethanol, electricity, and wood pellets while employing several people in full time wages in a system that can be scaled up/down as needed? This is the rural community planning I want to see as we transition to a brighter, more localized, future!