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| Special Projects – Biochar The origins of biochar are to be found in the Amazon rain forest. When the Spanish conquistador Francisco del Orellana became the first European to travel down the Amazon in 1542, he returned with stories of settlements and agriculture along the river. Later visits by Europeans found only jungle and with the forest soils too poor to support agriculture, it was assumed thathe had made it up But recently, soil scientists have discovered widespread deposits of man-made char (terra preta de indio) throughout the Amazon basin, which considerably improves the soil fertility over a prolonged period of time. It has also been found that charcoal remains in the soil without decomposing for hundreds- perhaps even thousands – of years. This has two critically important features: 1. It could provide
a vital tool for the improvement of marginal and degraded soils throughout
the developing world. Improving soil fertility Shifting cultivation is a common land use system in many developing countries. Natural vegetation – including primary forest – is removed to produce land for cultivation. Typically the land deteriorates rapidly and after just 1-3 years, needs to be left fallow for 5-25 years. As well as releasing large amounts of CO2 during the clearance process, slash and burn is responsible for the destruction of huge areas of forest in the developing world. |
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Maize crop trials at BEST Energies, Somersby, NSW. The plants on the right have been grown on soil, those on the left with soil and biochar |
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| If slash & burn techniques can be replaced by slash & char and the biochar incorporated in the soil, improved fertility will allow land to be kept under cultivation for much longer periods and reduce the pressure for deforestation. | ||||||||||||||||||||
Carbon Sequestration In a recent paper, Professor Johannes Lehmann of Cornell University states that whereas biomass added to soil as compost would initially store 100% of the carbon content, over 5-10 years this is reduced to 10-20%. Burning retains only 3%. Biochar, on the other hand, releases 50% of its carbon content during pyrolysis but most of the remaining 50% will remain stable for very prolonged periods. It could also be possible to reuse the CO2 produced as a feedstock for other industrial processes. A possible spin-off from this is the production of bio fuels as a by-product of the process. Lehmann has estimated that 30.6kg of carbon can be sequestered for each GJ of energy produced. By replacing slash & burn with slash & char, converting agricultural waste to biochar and by replacing some fossil fuels with biofuels, Lehmann estimates that sequestration could exceed the level of anthropogenic CO2 emissions by 2100. How biochar works Modern biochar
production involves low temperature pyrolysis
(the chemical decomposition of organic materials by heating in the absence
of oxygen) of biomass – typically agricultural waste including
forestry arisings, chicken litter, cattle slurry, rice husks and paper
mill waste. |
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BEST Energies pyrolysis plant at Somersby, New South Wales |
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Current activities in biochar From its rediscovery
in the past 15 years, biochar has already moved from a fascinating area
of academic research to a number of early stage commercial ventures,
aimed at unlocking its potential for both carbon sequestration and soil
improvement. In common with most young disciplines, a number of issues remain to be solved before major commercialisation can be achieved:
Psi-ense involvement in biochar Psi-ense’s Director Chris Budleigh has been interested in this area for several years. He attended the conference in Australia in 2007 and is in touch with several of the key players in biochar R&D in the UK and worldwide. Chris is particularly interested in exploring the economic issues facing biochar commercialisation and future Psi-ense articles will explore various aspects of the subject. To discuss any of the issues raised, please contact Chris on +44(0)1306 876505 or email chris@psi-ense.co.uk
More articles on Biochar |
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