
f you have not heard about biochar, you will soon.
It is a new, and also a very old, tool to fight climate change and make our lives better at the same time. Archeologists examining the remains of ancient communities in the Amazon have found that the soil, termed terra preta, is black and fertile, unlike natural Amazonian soils. They deduced that people in these communities had used biochar to increase soil fertility and that the biochar has not broken down over millenia.
Biochar is almost pure carbon, made from organic material such as wood, crop residues, or even dried manure, which have been burned in a low oxygen and high temperature environment, between 450 C and 650 C. In this process, the more volatile compounds are driven off (this is called pyrolysis) leaving behind pure carbon. Wood or crop wastes, instead of being burned and increasing greenhouse gas emissions, as is common practice in farming and in forestry, can be used to produce biochar. This will fix the carbon for the long term in a product which is useful in improving soil fertility and can also be used in construction materials such as asphalt and concrete. Another advantage is the lack of smoke, a frequent complaint in farming and logging communities when residues are burned.
The difference between charcoal and biochar is not obvious. Charcoal is made at a lower temperature (400 C) and is not as stable or long-lived as biochar. Biochar is more porous, less alkaline and with a negative electrical charge, all characteristics which make it capable of housing many more beneficial bacteria and fungi, and holding onto soil nutrients.
The many pores also hold onto water, making a garden or field with biochar more drought-resistant. A simple way of charging biochar with soil nutrients and micro-organisms is to add it to compost when adding kitchen or other wastes, at 10% or less by volume.
There are now many techniques available to make biochar. These include industrial systems with an outside heat source and the gases and biochar collected separately. There are some simple backyard scale systems, as well. In the B.C. interior, the first person to make biochar as far as I know, is Armstrong carpenter, inventor and environmentalist, Dave Derbowka.
Around 2010, Dave was cultivating fast-growing poplar trees to soak up effluent from the municipal sewage ponds in Spallumcheen, near Enderby. He needed to do something with the poplar logs contaminated with the effluent and he settled on biochar.
The main method Dave uses is called a “flame curtain” kiln or “kon-tiki.” In this method, the kiln carbonizes biomass residues in an open fire, which is placed either on the earth surface, in a pit or in an open trough.
The kiln generates enough heat to make the upper layer of fuel emit combustible gases (pyrolysis) which form a flame curtain. Beneath the flame curtain, the fuel itself does not combust. Instead, it carbonizes because the flame gases consume all available oxygen. Wood is added continuously and when enough has been added that the biochar fills half of the kiln, the biochar is cooled with water.
Dave has been selling the biochar to gardeners but is now working on making bricks out of biochar. If you wish to learn more, have a look on-line at “The 55 Uses of Biochar”. There are also a growing number of books on the subject.
I have started making biochar myself this year. My motivation was finding a method of dealing with the growing volume of tree branches on my acreage in the forest. Accumulating branches is an inevitable part of living in a forest. Leaving them on the ground is a fire hazard, and I did not want to burn them as many people do because of the greenhouse gases that would create, as well as the unwanted and polluting smoke.
This seemed like the perfect solution to me. I can then use the biochar for my garden, give it away or sell it. This year, I will produce around 3,000 litres of biochar and hopefully other forest dwellers will start to do the same.
This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.