Posted on July 1, 2010 by onestrawThere are several themes here on One Straw, but it can all be summed up with the statement that we need to build a regenerative culture as we skip merrily down Energy Descent. To do that we need to rebuild our culture, grow more of our own foods, find a way to power our civilization, learn a shit ton of new/old skills and stabilize the climate whilst dealing with the next 50+ years of weather silliness and rather a lot more. Any good permaculturist likes to hit more than one goal with each throw so I have been focusing on biomass lately.
I really need to write a biomass specific essay, but here is the skinny. Where I live in south central Wisconsin there is only fair solar and wind resources, no geo thermal to speak of and it has been several million years since we had a decent tide. But, thanks to plentiful rains, if you stop mowing your lawn for a decade you get a nice old field sucession. They don’t call it the “Northwoods” for nothing; we are really good at growing trees. Solar is a great way to make electricity and you would be insane to not consider something with such crazy low maintenance needs, but biomass has alot of fringe benefits to offset the labor input. Primarily – if you do it right you sequester literally tons of carbon. We all know that is cool ever since Al Gore told us so, but not only can we help offset truly catastrophic climate change, if we do it right, we can also heal our soils to feed our burgeoning billions. Carbon is a pain in the atmosphere (above 275ppm anyhow), but DAMN is it cool in the soil. We need to put it back.
Here is one of my all time favorite sustainability facts:
By raising the organic matter content by 1% you have effectively sequestered all the carbon above that area of soil.
Dang, sucka! This is why agriculture is such a huge contributor to global climate change – conventional ag destroys organic matter, removing it from the soil and getting it airborne through massive nitrogen fertilizers and tilling. But the simply beautiful thing is that we NEED to raise the organic matter content of our soil by 2-5% everywhere if we want to produce food organically and by doing so we heal the atmosphere. Trees, woody stalks, and straw are the best ways to get carbon out of the atmosphere (plants do it for free and are, by nature, carbon negative). The trick is to harvest that biomass efficiently and then process it in such a way as to sequester it for the mid/long term. Enter my Tuesday project.
I live right on a freeway. In addition to the noise and pollution, the salt spray in the winters also have a tendency to kill off or stunt just about anything I have planted there (trying siberian pea shrubs). But buckthorn thrives. Now I would never intentionally plant buckthorn, but there are several specimens on the D.O.T. side of the fence and one mature one just on my side. I have left it up as a windbreak to protect a maple I have planted. But that buckthorn is rather vigorous, as is their wont, and needs to be hacked back every few years. We call it trimming when its a chore and the material is thrown away, but when it is done with the specific goal of harvesting the biomass the proper name is Pollarding.
Here is a shot of the buckthorn with about 20% of the south side of it pollarded.
Its a BIG buckthorn! Pulled about 80#'s of biomass out and you can barely tell.
I essentially limbed up everything I could reach that had limbs facing in the 30 degree arc around the maple. This freed up a lot of room, and made too big piles of material. I separated these by use – the larger diameter wood (.75″-3″) I intended to chip up for oyster mushroom growing media, the leafy material at the end of the limbs would be shredded for compost.
I did not put any of this down as mulch due to the presence of very green berries on the tree. By composting this material I will essentially sequester half the carbon from the tree (the rest is off gassed by bacteria) for 5-50+ years in the soil as humus which is pretty stable. The results of chipping are always mind boggling. What started as enough material to fill my dump truck bed (11 cu yards) I am left with about 2-3 cu feet of wood chips and perhaps 9 cu ft of green shredded branches that will compost down significantly. Total weight was roughly 100#’s.
After composting it will be about 15# once the water is consumed by the bacteria and half the material is off gassed. The chipper does use fuel, but this stunt only consumed about 1/2 a cup which is less than my neighbor used mowing his lawn while I did this. Larger chippers are more efficient and can be run on methane from the midden or ethanol if gasoline engined, or biodiesel if not.
The shear scope of our problem can be staggering at times. I would like to add 1″ of topsoil to my new garden, which is 1100 sq ft. That works out to just shy of 7000#’s of compost. For one garden. That is why I am becoming more and more convinced that the single most important thing we can do is to plant trees. LOTS of trees. The great thing is that it isn’t that hard. 1.5 acres of willow will produce 22000#’s of chips annually (harvesting .5 acres a yr) for 2 decades or more before needing to be replanted. And that is dry trunk chips only, not the leafy biomass of the fronds. While we can’t grow the biomass needed to heal our soils in our own backyards, we can certainly plant enough trees and “woody” plants into our home landscapes to maintain the soils once we have healed them. 100 acres of marginal corn land – say near rivers that flood seasonally and shouldn’t be planted to annuals anyhow- planted to willow coppice would produce enough biomass to rebuild almost 100,000 sq ft of garden a year. Every year after year 3. In 8 years we could have a garden as large as mine in every yard in my hometown of 500 homes churning along at 5%+ organic matter and be producing 500,000#’s of food annually while also sequestering hundreds of tons of carbon annually.
When combined with energy systems like the Methane Midden, which has 6000#’s of chips in it, sequestering carbon can also offset carbon emissions for energy production. I planted 15 willows on our property this year specifically to begin coppicing in a few years. Next year I will pull rods from them to start 50 or so more. Box elders are another strong coppice candidate in this area. The hedgerows for a 5 acre sustainable produce farm divided into 1 acre plots would grow enough biomass to run a gasifier for a year while sequestering 11000#’s of carbon to be added back to the fields as biochar to help create terra preta.
We can partner with nature to heal the damage we have done. Even in the burbs.
Be the change!
Posts
No comments:
Post a Comment