Willow Coppice Math Fun

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?  

 

I loved the shot of the willows towering over the people in the shot … after only 5 months!  Wow these buggers grow fast!

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!

Be The Change
-Rob
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Fall Cover Crops

 

Next Years early potatoes...

Next Years early potatoes...

 Several weeks ago I wrote an atypically lyrical bit on Fall and my gardens.  I love this season, and now I would like to pass on a bit more of the practical bits of what I have been up to – tucking my beds in for winter.  My preferred method of soil stewardship is cover-cropping. Last year I used alot of straw in my home beds after reading Ruth Stout and Lee Reich and their deep mulch gardening.  It worked very well – my garlic was essentially weed free for the entire season.  And I will continue to use straw mulches on my permanent home beds.  But out at the market garden I am using cover crops almost exclusively.  Above is a shot of a cover cropped field that had been in Garlic, and will be an early potato planting in 2009.  This field still has a fair amount of perrenial weeds -primarily quack and thistle so leaving it bare is not an option if I am to turn the tide.  Rye/Vetch is a great standby for both nitrogen and biomass, but I hope to plant this field in April -too early to let the vetch really fix nitrogen and the thick masses of rye roots decompose.  

Oilseed Radish and Field Pea Cover -5 weeks

Oilseed Radish and Field Pea Cover -5 weeks

So instead I wanted to put in a “winter kill” mix of annuals that would put on biomass in the fall, but be ready to plant in early spring.  For this I choose a mix of 4 crops: Oilseed Radish (good root mass and nematode protection), Field Peas (nitrogen and cold resistance for late growth), Oats (biomass and root structure to outcompete weed roots) and Buckwheat (quick cover to let the peas and oats get going).  This worked fabulously -the buckwheat sprang up quickly to shade and stunt the resprouting quack, only to be killed off in the first mild frost 3 weeks ago.   This was timed perfectly to let the radish and field peas to shoot for the last vestiges of Fall Sun.  Despite some 28 degree frosts, all crops are going strong, with only some minor frost burn on the radishes.  The plot is a dense mat of greenery about a foot thick that will be killed off by Christmas to blanket the soil for the winter.  Come spring it will be easy to till under or transplant through.

 

3 Week old Rye/Vetch

3 Week old Rye/Vetch

On this years potato patch I did plant Rye and Hairy Vetch.  This plot will hold melons in 2009 which matches very well.  Melons and Squash will not be ready to plant until June, leaving plenty of time for the rye/vetch cover to be mown and begin to decompose.  My hope is to plant directly through the rye stubble; if the mowing is timed correctly it will not resprout. Also, the decomposing rye is naturally allopathic (prevents weed germination) which will not inhibit transplants, and the thick mat of straw will help reduce damage to the growing fruits.  That is the hope, we’ll see how it works.

My choice to cover crop on the larger market gardens was made for a variety of reasons.  First, there are some very real practical ones – laying out a 4″ thick mat of straw takes alot of straw.  I don’t have a bale blower so labor would be extreme, and straw bales are going for $3.50 up here (none of it organic) and it would have been $200 to cover my beds, rather than $30 in seed.  Secondly, I would rather not import 5000+ pounds of organic matter to the site if I can just grow it in place, cycling the nutrients in house as it were.  Finally, from a soil ecosystem perspective, I like to have living roots in place as much as possible to foster the soil flora/fauna that I will need next year.  

Mulching works wonders on the soil as well – the soil under my garlic this year was incredibly light after the worm population exploded while feasting on the year old straw mulch.  One hope next year is to grow my own mulches with a 3000 sq ft crop of sudan grass which can reach 4-6′ tall and produces several cutting annually.  I tried this in 2008, but the resident chickens ate all the cover crop seed before it sprouted (I planted too early) so I will need rethink it a bit in 2009.  The Sudan Grass mulch would cover my tomato and potato rows early in the season, and the later cuttings will blanket the Hoop House and other beds.  

Later this week I will post the 2008/9 picks of the Hoop House which has been moved and replanted.  Stay tuned!

-Rob

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