Locking up carbon with biochar

Turning crop wastes and other biomass into charcoal and spreading it on tropical soils can sequester carbon and boost crop productivity
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Link to video: Manchester Report: Biochar

Biochar is a type of charcoal produced by heating crop wastes, wood or other biomass in a simple kiln designed to limit the presence of oxygen. This process, known as pyrolysis, creates rather than consumes energy, as more combustible gases are released than are needed to heat up the kiln.

Biochar is made largely of carbon, which the crops or trees previously sucked out of the air in the form of CO2. Unlike crop wastes and wood, it's an extremely stable substance, which if mixed into soil will safely lock up its carbon content for hundreds or even thousands of years – a biological form of carbon capture and storage.

If biochar is mixed with poor-quality tropical soils, it has an important added benefit: it can significantly boost crop productivity, reduce nitrous oxide and methane emissions and improve soil structures. These effects are the result of biochar's structure, which is full of microscopic pores that can harbour useful bacteria and fungi.

Biochar advocate Laurens Rademakers arrived in Manchester directly from Cameroon, where his experiments have demonstrated quite how effectively biochar can increase crop yields. In his photos, wheat grown with biochar-enriched soils is almost twice as tall as the same wheat grown in the adjacent plot without biochar.

Rademakers and others believe that if sufficient amounts of biochar were produced – both on the micro and small industrial scale – the world could reduce atmospheric CO2 concentration to a safe level at the same time as increasing food production. The idea is extremely promising – as long as biochar schemes are managed carefully to ensure that wood from virgin forests is never used as the source material.

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