Biochar: low tech gift from past to future

By Martin Grimshaw. First published in Transition Free Press 4 (Winter 2013) for a Transition Towns audience.

Sacred Earth, a social enterprise which manages 40 acres of land in Sussex, is integrating education, mentoring, Community Supported Agriculture and experiments with soil restoration, inspired by ancient Amazonian ‘terra preta’, or black earth.

Despite the abundance of life in tropical forests, soil fertility is very weak, since conditions don’t allow decaying matter to penetrate into the earth. For a long time experts puzzled over the origins of several pockets of terra preta in the Amazon, and have now determined that these areas of extremely productive soil are man-made, created by burying charcoal and food waste.

Biochar is a method of replicating the process: ‘cooking’ woody material at a low temperature in a sealed low oxygen kiln, then returning it into the soil. Since greenhouse gases, such as CO², methane and nitrous oxide, are mostly captured by the pyrolisis process and the carbon stored in the wood, it is carbon negative and has been hailed by scientists such as James Lovelock and James Hansen as part of the effort to combat climate change. Unlike most geo-engineering solutions proposed to mitigate global warming, biochar is low tech and smart. It also provides multiple benefits: increased crop yields, reduced use of irrigation and fertilisers, and it is a tonic for urban, rural and ‘developing’ world economies.

Sacred Earth Land biochar
Picture: Sacred Earth

Philip Greenwood of Sacred Earth speaking at this year’s Transition Camp, explained: “Biochar is alchemy for the soil. Exciting and diverse applications are being conducted with impressive results, but more research is needed. Agricultural and problematic forestry waste such as rhododendron, laurel, privet and yew hedges, and leylandii have been tried.

“We can process sawdust and timber yard offcuts, and biochar can reverse soil acidity following commercial pine forestry. It supports micro-organisims in the way that a coral reef is a platform for ocean diversity, and stabilises minerals for slow release.”

Concern has rightly been raised about rashly displacing arable land for large scale biochar forestry. However, the Transition movement promotes simple, small scale solutions that can be replicated on a large scale , while boosting the ‘Transition Economy’. Approached wisely, biochar is a worthwhile experiment we can all explore.

The Big Biochar Experiment is an Oxford University led research effort enlisting citizen scientists reporting results back from their allotments, with very promising progress.

If you have a garden or allotment, try adding small chunks of charcoal made from your seasonal clearances to your compost, to improve soil richness and structure. You can buy or make your own small biochar oven (there are videos on YouTube). If you are farming or have access to land, you can buy larger kilns and even harness heat, electricity and biogas or oil, as a byproduct. As a local Transition group you could establish a social enterprise, working with your council and other land users.


The Big Biochar Experiment

Critique and debate:
George Monbiot: Woodchips with everything. It’s the Atkins plan of the low-carbon world
James Lovelock on biochar: Let the Earth remove CO2 for us
biofuelwatch report on biochar

Film: BBC Unatural Histories – Amazon: Terra Preta

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