Biochar at the Centre for Alternative Technology: business opportunity for small woodland owners or climate change solution
Biochar may be used to mitigate climate change brought on by global warming, by removing carbon dioxide from the atmosphere and locking the carbon into the soil, if James Lovelock (originator of the seductive Gaia hypothesis) is to be believed. Others say the numbers just don’t work. Biochar is also put forward as a very effective soil improver, which can reduce fertiliser use, reduce pollution, increase crop yields, and as an approach to agriculture may be traced back to the terras preta (black soils) of the Amazonian rainforest.
Woodlands’ Welsh team recently held its annual conference at the Centre for Alternative Technology (CAT), near Machynlleth (a fascinating and excellent location for a meeting) and were given an overview of how the method works, and the research being carried out at CAT. Grace Crabb is the resident biochar expert, who also manages and helps to lead the woodland management and green woodworking courses run by CAT. She is also the resident expert on water supply and sewage, and in her spare time looks after the geese!
Biochar is charcoal created by pyrolysis of biomass. It differs from charcoal only in the sense that its normal use is not for fuel, but for capture (sequestration) and storage of atmospheric carbon capture. Charcoal is a stable solid rich in carbon content, and can be used to lock carbon in the soil. Biochar is of increasing interest because of concerns about climate change caused by emissions of carbon dioxide (CO2) and other greenhouse gases. Other approaches to carbon dioxide capture would tie up large amounts of oxygen and requires energy; biochar on the other hand, locks in the carbon captured by crops and trees, and releases the oxygen back into the atmosphere.
As a way of creating charcoal, the biochar process seems to be very efficient, and much quicker than traditional methods of creating charcoal. Although there isn’t a proven market, it may also be a business opportunity for small woodland owners to produce biochar for sale through local outlets as a soil improver.
The retort used to produce biochar at CAT reuses three basic components: a metal shell to contain the fire (looks like an old oil tank), oil drums to contain the charcoal, and old railway track to support the oil drums over the fire. Pretty it isn’t, but looks simple and cheap to construct, and is very effective. Charcoal produced is about 70% of the volume of material loaded at the start, and unlike the traditional kiln method of charcoal production, the fire to drive the process is separate from the wood that is being converted to charcoal.
We gathered around the tank first thing in the morning (just after those geese were let out) and put the ends on the oil drums, the fire was lit underneath, and the process initiated. Water is driven off by the heat from the fire first, and then smoke colour changes as different by products are produced. Gases are produced by the process, including methane that feeds the fire that drives the process. By 3.00 in the afternoon, the fire was out, the retort had cooled enough for us to remove the ends, and remove the charcoal.
CAT will be carrying out tests on crop yields and tree growth resulting from applying biochar as a soil improver.
There are many sources of further information, but
- CAT produced a video about 18 months ago and
- Biochar Solution: Carbon Farming & Climate Change, by Albert Bates, seems to be well regarded.