Biochar
Biochar (also known as agrichar, black carbon or BC) is a carbon-rich material produced by heating plant-derived organic matter in an environment with restricted oxygen. Biochar production from sustainable sources of organic waste is currently being advocated as a way to reduce greenhouse warming. Advocates say the biochar process is carbon-negative, removing more carbon dioxide from the atmosphere than it produces.[1][2] They also say charcoal is a sustainable method of soil enrichment and has the potential to help clean up environmental pollution.
The technology is strongly advocated by some scientists, notably Johannes Lehmann, associate professor of soil fertility management and soil biogeochemistry at Cornell University. Biofuel and energy companies are lobbying governments to subsidise biochar production and to allow it into the carbon trading program, as part of measures to counter greenhouse warming.
Biochar has, however, come under criticism from environmental groups, who warn that its claimed benefits are largely unproven and that it could lead to huge destruction of biodiversity.[3]
Claimed benefits
Biochar advocates say charcoal can be used as a soil conditioner which provides a stable carbon storage (sequestration) system, enhances soil fertility, and filters out pollutants.
These properties are said by biochar advocates to be able to address some of the most urgent environmental problems of our time:
- Soil degradation and food insecurity
- Water pollution by agrochemicals and other toxins
- Climate change due to an excess of carbon dioxide in the atmosphere.
Terra preta
Charcoal has been deliberately incorporated into cultivated soils for thousands of years. The best known charcoal-improved soil is the terra preta of the Brazilian Amazon. Its high level of fertility makes it popular for growing cash crops such as papaya and mango. These crops are said to grow three times faster than on surrounding unimproved land.[4] Similar soils have been identified in Ecuador, Peru, West Africa (Benin, Liberia), and the savannas of South Africa.
Terra preta contains high levels of soil organic matter and nutrients such as nitrogen, phosphorus, potassium and calcium. This is attributed in part to a high charcoal content.[5]
Resources
Notes
- ↑ Lehmann, J., 2007, A handful of carbon, Nature 447: 143-144 doi:10.1038/447143a
- ↑ Lehmann, J., Gaunt, J. and Rondon, M., 2006, Bio-char sequestration in terrestrial ecosystems – a review, Mitigation and Adaptation Strategies for Global Change, 11:403-427
- ↑ Almuth Ernsting and Rachel Smolker, “Biochar for Climate Change Mitigation: Fact or Fiction?”, Biofuelwatch, February 2009, p. 5
- ↑ Saran Sohi, Elisa Lopez-Capel, Evelyn Krull and Roland Bol, “Biochar, climate change and soil: A review to guide future research,” CSIRO Land and Water Science Report 05/09, February 2009
- ↑ Glaser, B., Haumaier, L., Guggenberger, G., Zech, W., 2001. The 'Terra Preta' phenomenon: A model for sustainable agriculture in the humid tropics. Naturwissenschaften, 37-41.
