Bio-Char Composting

So I’ve written about Bio-Char before – its the essentially pure carbon that is left over from burning wood in the absence of oxygen.  We make some while running our gasifiers and its a prime component in Terra Preta – the incredibly fertile soils found in bits of the Amazon.  It has also been in the eco-news a ton lately as a means of carbon sequestration.  There have even been some low tech trials (low tech are my favorite!) using it as a soil amendment.  What those trials have found is what I had suspected: that while long term fertility potential is increased due to the addition of carbon to the soil, all those free ionic bonds “fix” nitrogen out from the soil and initial fertility is lessened for a year or more.  The trail found that by saturating the bio-char first (in this case with human urine) the results on harvest were substantial.  I have dreamed of using bio-char from our gasifiers as a final filter in a aquaponics system – not only to clean the water, but as importantly to “pre-charge” the bio-char with nutrients for its use as a fertilizer.  Since I don’t have my aquaponic greenhouse yet, and my suburbanite neighbors wouldn’t take to kindly to me pissing in a bucket each morning in the backyard, I decided to use my compost bins as the nutrient source.

Compost bins leach out a significant amount of nutrients -either through runoff, or through ammonia gas.  My thought is that by mixing biochar into a pile, I would precharge the char, and the end result would be an even better soil amendment.  So, putting action to thought as is my wont – here is what I did this afternoon:

35#'s of hardwood charcoal from Whole Foods. $28 and likely a better use than grilling steaks.

We don’t have access to our own charcoal yet (next year I may make my own charcoal maker), so Whole Foods helped me out with an end of season sale.

Next I needed some material.  As I wrote about yesterday – that is no problem anymore.  400# of willow coming right up!

2 days old and free. The things people throw away these days!

Finally, I ran the willow and the charcoal through the chipper.  The thought was to make the char into itty bitty bits to increase surface area.  I figured dust would be an issue, but DAMN is dust an issue!  Carbon dust is quite dangerous – rather explosive and wicked rough on your lungs.  I had a dust mask on, and mixing the charcoal in with the leafy fronds helped, but soaking the char first might be better.  Its an issue, and you’ve been warned.  Here is the results:

Always amazing how much it reduces in volume once its chipped. Plan on soaking this a lot - that char is DRY.

The plan for this bin is to fill a raised bed for a side by side run next year.  My hypothesis is that the compost char will increase the fertility potential of the soil by preventing leaching and raising the overall carbon content of the soil significantly.  Bacteria LOVE to live on the incredibly rich surface structures of char particles, so soil life should explode.  This will hopefully be a major component of my pushing for 10# ‘ sq ft in some raised beds next year.

It will be interesting to see if the added char will affect the composting process at all.  It may inhibit it due to the char sucking up nutrients.  I have a good idea of the process with 4 brush piles in the works, so it should be readily apparent if more nitrogen is needed in a charified pile.

Much more to come!


Brush Composting – 5 wks to Humus

So this summer I went Compost Crazy.  First with the Midden and its ongoing Epic Insanity, and then once I saw the power of shredded brush composting, I starting going ape shit with my chipper.  Over the past 1.5 months I have cut or scrounged over 5000#’s of brush, run it through my chipper / shredder and all but filled my Compost Bin of Dreams.  In fact, I am one trip away from it being maxed out which is about 5.5 yards of compost.  Dang sucka.  Of note, I have yet to start my third gallon of  gas.  The Bio-80’s 5hp Briggs is frugal.

I have good reason for my madness.  Shredding weeds and very brushy material makes SYCK compost – and it does so incredibly fast.  The batch of lambsquarter I ran through on July 29?  Yeah – its DONE.  Not “yeah, I can *probably* spread this.” done.  Its DONE.  And its not only the speed on the decomposition end – its on the sourcing end.  One of the problems with home composting is it takes all year to get material to fill a bin, then another 3-4 months to cook it down.  Thats a year or more.  I don’t have time for that given the harvest goals for my place and the resulting soil building needs.  With my Chipper, I now cruise the municipal yard like a crack addict looking for fresh cut shrubs or prunings on an almost weekly basis.   I can take 2 loads from the yard to my house and shred them in less than 3 hours, and 2 loads will get me about 1.75 yards or chips (800#’s) which will cook down to about .8-1 cu yard.  3 hours of work and a fraction of a gallon of fuel for 600#s of humus.  I’ll take it!  Here are some shots of the process in action – the Week 3 shot didn’t turn out, but I will add one tomorrow.

It all starts with shredded material – this is what 350#’s of willow looks like after the Bio-80 has its way:

Small particle size is crucial. LOTS of green material as well. This is soaking in 20 gallons of water overnight to raise water content.

It takes 2 loads of with the trailer to fill a bin, about 8-900#’s of brush.  Here is what it looks like after 2 weeks – remember that this will be 165 degrees with in 24-36 hours and stay over 140 for 14 days.  This system is stunning.

Woody chunks still visible, but greens are all gooey. The woody bits in the middle are well on their way to humus. This will heat again to 150, and fall to 120 over the next 2 weeks. Add water if needed, but if you soaked it well, it should be fine.

Again, Wk 3-4 pic was a flop, but will add one soon.

Here is a shot of the lambsquarter : box elder pile after 5 weeks.  This is the fastest I have ever seen compost created, and on par with the commercial operations with mechanical turners.

Done. The clumping is due to moisture - this pile is sopping wet due to rain. There is virtually no identifiable raw material left other than some box elder twigs. 5 weeks!

Now, the lambsquarter pile is likely going to outperform the other 3 piles in the bins right now due to the fact that it was primarily annuals with much less cellulose and lignin to break down – it also shrank almost 50% for that reason. This pile was also so nitrogen rich that it hit 178 degrees in early August – that is just silly and literally destructive to the microbes in the piles – at that temp you are cooking your hibernating mezophillic bacteria which is NOT a good thing.

I am very curious to see what the pure brush piles look like in 1.5 months, but they aren’t tracking too far behind.  This pile can be recreated with sun choke stalks, cupplant, as well green sweet corn or sunflower stalks – but again – it takes ALOT – 800-1000#’s per pile since green material has so much water in it.

But the results speak for themselves.  With my new setup I can have 2-3 cu yards over winter to be spread in the spring for my early plantings, and start new piles in April.  By June I should be able to spread another 1″ of compost over the beds before the Heavy Feeders go in, and then another 1″ after they come out.  It should be possible to run 3+ batches through the Compost Bins netting up to 15 cu yards of compost – in theory, enough to cover my 1000 sq ft annual bed 5 times to a depth of an inch.  Of course the permaculture beds, insectary plantings  and coppice mini- groves will get their share too.  With this much humus hitting the soils of the system, organic matter will skyrocket along with yields.

And the icing on the cake?  15 cu yards of compost (humus) will sequester about 4 tons of carbon each year as well.  Not bad at all.

Be the Change!


Carbon “Fixing” Plants

Most gardeners are aware of “nitrogen fixing” plants; those plants, typically legumes, that have formed symbiotic relationships with soil bacteria to take airborne nitrogen and fix it into water-soluble form.  As far back as the Romans, humans have fostered this natural occurrence to increase yields and increase fertility.  What we hear about much less is carbon “fixing” plants – in Permaculture speak – biomass or mulching plants.  In the past year, as I have learned more and more about soil ecosystems, I have become far more convinced that these “carbon fixers” are even more important in early successions as we heal our suburban ecosystems.

I have developed a mantra over the summer as I have worked to sloganize what it is that we are doing.  The result has been my oft-repeated imperative to: Heal the Soil, Store the Water, & Plant Useful Plants.  In a nutshell it is a roadmap to maximize the potential of any garden space – if the soil is alive it has more nutrients cycling in it, if the soil has sufficient water stored under mulches and in humus then  the potential increases again.  And once these two are in place, one can maximize the solar potential by filling in the canopy.  Of these, I feel the first is the most important as it makes the others possible.  And to heal the soil, you need carbon (organic matter).

Plants are truly the conduits of energy into the earth – by capturing solar energy and turning it into simple sugar they supply the foundation for 99.99% of all life on the planet, whether it is through root exudates in the rhizosphere or nectar through their flowers, plants make life possible.  But life also needs carbon, and most life on the planet gets its carbon from plants in the form of organic matter – the main food source of the bacteria and fungus in the soil.  But some plants do this better than others.

There are the grasses with their dense root systems that build soil visibly every year, and there are trees that cover the ground in a thick blanket of leaves every year.  Finally there are other plants that form stalks and stems that form significant amounts of soil as well – the tall grass prairies, corn/sunflower stalks, and windblown branches from softwoods such as willows, sycamores, and poplar.  What these have in common is tough, long carbon chains in their cell structure that resists decomposition.  This resistance to decomposition -in lignin, cellulose, etc-  is what forms humus.  And it is humus that forms rich soils.   This is something to be very mindful of as we mulch our gardens.

If you were to build a compost pile of nothing but greens, with only the barest amounts of “browns”, the pile would heat up very quickly, but would decompose down to almost nothing – 75-90% of the bulk would be gone.  That is because greens lack cellulose and lignin and are mostly water and nutrients – vital to soil life, but almost completely consumed in the decomposition process.  Compare this to a similar sized pile of shredded leaves.  It will take 4x as long to decompose, but the result will be 400% more humus with only a 25% reduction in size.

In most of my permaculture guilds I have stressed the green mulches of comfrey, sorrels, chives, etc to pull and cycle nutrients, and for several years I have imported my cellulose and lignin in the form of dozens of yards of wood chips.  Now that my gardens are maturing, I am starting to pay more attention to including plants specifically to “fix” carbon to maintain soil humus levels.  In the 6 years I have lived here I have lost about 1-2″ of total height in our 3 oldest perennial beds compared to the sod.  That is because the humus in the perennial beds is degrading over time, while the roots of the fescues in the lawn are forming .25″ of humus a year.  I had not been mulching these beds much as they have almost completely closed “canopies” of thyme ground cover that I didn’t want to smother.  I will try mulching more aggressively this year.

While all my guilds include nitrogen fixers such as leadplant, false indigos, New Jersey Tea, Serviceberry, etc and green “mulch” plants such as Russian Comfrey, I am beginning to either add in “carbon fixers” and am planting guilds specifically to grow brown mulches.  Some of this I am accomplishing by letting box elder seedling mature in my guilds as they sprout in the wood chip mulch.  In one spot, I have planted a 20 tree “short rotation coppice guild” of willows, poplar, and box elders.  In my annual gardens I am taking much inspiration from John Jeavons and planting “stalky” plants such as corn, sorghum, and sunflowers specifically to produce compost carbon in addition to edibles.  Once you change your mindset it isn’t overly hard.  Of course, having a chipper to use can become important as well – though many plants such as sunchokes, and weeping willows produce stalks and “leaf” mulches that are laid down without chipping and fast growing trees such as Empress and Sycamore have HUGE leaves that really add up.

As my gardens have matured, and I seek to support the soils I have built using primarily the inputs of my site, I find myself planting more and more of these carbon trees to grow my soil.  In doing so I help to maximize the potential of my site by using these fast growing plants to sequester carbon to build the soils beneath my edibles, while also pulling carbon from the air to heal our climate.

Prime Short Rotation Coppice Trees:

Willow, Hybrid Poplar, Black Locust, Box Elder, Empress, Sycamore, Ash, Hazelnut, most Standard fruit trees (annually pruned)

Prime “Carbon Fixing” Annuals/perennials:

Sunflower, Corn, Sorghum, Cupplant, Sunchoke, Small Grains, Amaranth, Quinoa, etc.

Many of these trees are useful in many other regards – Black Locust is a nitrogen fixer, provides rot resistant wood, and its flowers are a great early nectar source.  Black Maul willow is one of the most striking plants I have ever seen and the new growth makes incredible baskets.  Hazelnuts and Sunflowers are some of the best ways to grow healthy fats in the northern hemisphere.  Carbon gardening is by no means boring or a wasted effort!

Productive soils need to have all their nutrients cycled, not only the water soluble ones, but also carbon to replenish that which is lost due during the respiration of the soil organisms.  If we are to truly garden in the spirit of nature, we need to make sure that the carbon is replaced with the same diligence that we give nitrogen, phosphorus, potassium, calcium, and the 96 other macro and micro nutrients.


%d bloggers like this: