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:
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!
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:
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!