Suburban Pollarding: Making your own mulch

There 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% in the top 6 inches of soil, you have effectively sequestered all the atmospheric 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.

the left pile is half off frame and is intended for compost, the right is about 10' long and intended for mushroom media.

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.

Chips in foreground for mushroom growing, green shredded material in background for compost.  Entropy!

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!


17 Responses

  1. I’m planting willows this coming spring. Mine will find another duty as withes for fences, baskets, and the like, as well as fueling compost and serving as mulch.

    Got any chipper recommendations?

    • Don’t skimp on size and make sure the shredder element has a straight shot through – the shredding clogs easily. Electric is NOT an option even for just leaves – you need HP. Flywheel size is a HUGE factor. Many manufacturers skimp on flywheel and try to overcome with engine hp, but you really need the inertia to push through a clog. My BCS Bio-80 has an 18# flywheel and only a 5hp motor. Easy on fuel and can handle 3.5″ logs if you meter them (only designed for 2.5″ though). Bearcat and DR make the best farmette scale, but you are in 4 figures there. Some of the Troybuilt are ok, though, again, check flywheel and shredder design. Craigslist usually has 3-4 decent ones for $250-$400 around here. If you get a used BCS/Grillo they make really high grade units like mine for them🙂

  2. I am working on a permaculture project and this helped to confirm the need for willows to be planted on the site. Thanks.

    • Cool! And as Emily said, they have other uses like habitat, basketry, aspirin, etc! Forest Farm has a HUGE selection of willows, or just go snip off some new growth from any in your area, stick them in the ground, and keep well watered. I had 11 of 11 root that way this spring.

      • You can also use willow bark to create your own DIY rooting hormone to propagate cuttings that are a little more difficult to root on their own! Rooting hormone can get expensive if you are propagating a lot of plants to fill a site.

  3. Great article!

    Have you considered sea buckthorn (not a true buckthorn) for that salty space, or is it too shady & damp? I hear the Soviet bloc developed some interesting food varieties a while back.

    I’d also like to mention briefly that coppice/pollard operations can put up a fair amount of winter feed for goats to replace their browsing, in the same way that hay might replace grazing.

  4. I’m going to be experimenting with coppicing and pollarding later this year. I’ve only got 1 acre, but a lot of mature and semi-mature trees (many of which are in the wrong place!).

    I’m planning to get firewood from the trunks and main branches, kindling from the smaller branches, and mulch/compost from the leaves and smaller stuff.

    We live in such a mild climate that I probably only need a half-cord to a cord per year for firewood (maybe more once I get the pizza oven built!), so I think I can probably provide all I need from our block.

    As always, I’m keen to follow your progress in this area.

  5. Thanks again for a thoughtful insight into a better but equally
    plausible future.

    I wonder if you can share thoughts on using bamboo instead of woody species for the same purpose?


    • You’re welcome Bryan! I think Bamboo is a great candidate due to its simply incredibly growth rates. Not sure how well it chips or breaks down, but due to its insane hardness the resulting humus should be very durable. I have very close to zero experience with it, is it less hard when green like most plants? My concern is that it will dull chipper blades with incredible rapidity, but this could be offset by the shear ease of harvest and the reduced space needs for the coppice plot.

      To help me answer these nagging questions, I have planted a very hardy strain of clumping bamboo in the backyard to see what will happen. At best, it will grow slow in the frigid north, and never achieve full size, but it will help me better understand this marvelous plant.


      • One strategy for bamboo might be to cut it into reasonable-sized sections (maybe three feet?), then use a rolling mill to crush them. The strands would be long and sharp, but could be handled with a fork and would still be useful for most of the same things as wood chips.

      • My experience is that once established, the easiest way to convert living bamboo into biomass is to just let it dry out. It will drop its leaves in no time, giving new meaning to the word bioMASS.

        We shred it if we can be bothered, or just throw it on top of wherever we want it. Great mulch becomes great soil.


  6. Joel’s advice on Sea Buckthorn is on point, assuming it isn’t invasive in your area. Mulberry, russian olive, and goumi also produce a phenomenal amount of biomass on marginal soil, as well as fruit.

  7. Trully epic shit brother. Thanks for postings clearly and positively.. much needed and inspiring.

    Could you recommend books, sites and other resources on pollard/coppicing? Where should i start?

    • Thanks Adam. As far as books and sites go, I am mostly self taught. Most of the comercial stuff on coppicing is from Europe, especially England. The equipment they use is INSANE. But if you think about the amount of fuel they are harvesting per minute, and the fact that there is no weeding, nor tilling, it is likely energy positive and certainly carbon negative. There are at least a half dozen workshop type vids on you tube on coppicing as well.

  8. Just a question for the crowd. I’ve heard that when you trim back a tree the roots associated with what you’ve trimmed also die back, then re-grow along with renewed growth in the canopy. Is this the case? If so, you’re probably underestimating the carbon sequestration potential of the methods you discuss.

    Love the blog!

    • Roots aren’t technically associated one for one, but it is true that root die back is typical in coppicing or even pruning. The, now dead, roots would then become part of the soil food web and be sequestered for some time with some portion eventually becoming humus with a much larger staying power. It is a very good point, but I have no way to quantify it unless someone has a common figure.

      One very interesting side shoot would be if one was coppicing a nitrogen fixing tree –black locust comes to mind– the bacteria nodules on the roots would also die, thusly freeing the nitrogen into the soil ecosystems. So managing a black locust coppice intercropped with fruit tree guilds could really push soil fertility. Also, black locust is a much harder (denser) wood than willow, though still fast growing. I suspect (but have not found evidence) that the btu’s per acre of a black locust biomass coppice would be very attractive indeed. Also, the added density of the wood also likely indicate more carbon sequestered (humus) per cu ft of compost.


    • I tend to think along the same lines as Rob with this one. My experience with soil creation has taught me one thing more than any other – drought tolerant, deep rooted, nitrogen fixing “weeds” are the ultimate in creating a positive cycle of organic matter adding, soil water retention, biological activity generation, humus creation. In our dry part of the world, the preferred option pigeon pea. Just broadcast the seed, then chop and drop – repeat and repeat and repeat.

      Interestingly, this has led to the creation of a soil that now supports bamboo which offers a more accelerated introduction of biomass. But still, it is chop and drop. Pigeon pea as a deep rooted, mineral mining, plant, and bamboo as a shallow rooted humus creator.


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