The Natural Fix?

veloped world is already declining and may continue to decline in the future (Balmford et al. 2005), potentially freeing up land area that may be used to sequester carbon. Recent evidence shows that carbon gains have occurred in agricultural land abandoned after the collapse of the Soviet Union (soil gains of 0.47 t C per hectare per year, Vuichard et al. 2009). This is also known to be true of abandoned lands in Europe and North America as it is in the early stages of succession and forest de- velopment that carbon sink strength is strongest. Biochar is a new and poorly understood technology and it is likely that its effectiveness as a carbon storing strategy will depend heavily upon economic and environmental fac- tors. Research is still at a preliminary stage and large-scale biochar deployment is inadvisable until these uncertainties are resolved. Biochar is an emerging technology in which organic materi- als are reduced by pyrolosis at temperatures of 350–500ºC, producing energy and a carbon rich charcoal that is returned to the soil as a stable form of soil carbon. Research to date has indicated that biochar may have the potential to seques- ter significant amounts of carbon, while providing benefits to soil fertility and nutrient retention (Lehmann et al. 2006) Nevertheless, the creation of biochar plantations should be approached with great caution. While the use of biochar could be realised in a number of ways including shifting cul- tivation, charcoal production and the recycling of agricultural wastes (Lehmann et al. 2006) the most likely large-scale source of biochar production is from the burning of biofuels. To be justified as a carbon storage strategy, the amount se- questered must exceed that produced in moving it between its site of production, burning and application. In the case of crop residues it must be ensured that biochar addition provides a similar carbon gain to the simple return of these materials at the site of production. The impacts of large-scale biochar production on biodiversity and long-term agricultural sustainability (e.g. nutrient depletion) are unknown. Biochar: A Panacea?

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