Biochar


“Soils with biochar additions are typically more fertile, produce more and better crops for a longer period of time.”

Biochar is the carbon-rich product when biomass (such as wood, manure or crop residues) is heated in a closed container with little or no available air. It can be used to improve agriculture and the environment in several ways, and its stability in soil and superior nutrient-retention properties make it an ideal soil amendment to increase crop yields. In addition to this, biochar sequestration, in combination with sustainable biomass production, can be carbon-negative and therefore used to actively remove carbon dioxide from the atmosphere, with major implications for mitigation of climate change. Biochar production can also be combined with bioenergy production through the use of the gases that are given off in the pyrolysis process.

Nutrient Affinity
All organic matter added to soil significantly improves various soil functions, not the least the retention of several nutrients that are essential to plant growth. What is special about biochar is that it is much more effective in retaining most nutrients and keeping them available to plants than other organic matter such as for example common leaf litter, compost or manures. Interestingly, this is also true for phosphorus which is not at all retained by ‘normal’ soil organic matter (Lehmann, 2007).

Reading:

  1. Lehmann J 2007 Bio-energy in the black. Frontiers in Ecology and the Environment 5, 381-387.
  2. Lehmann, J., da Silva Jr., J.P., Steiner, C., Nehls, T., Zech, W. and Glaser, B.: 2003a, ‘Nutrient availability and leaching in an archaeological Anthrosol and a Ferralsol of the Central Amazon basin: fertilizer, manure and charcoal amendments’, Plant and Soil 249 , 343-357.
  3. Liang, B. , Lehmann, J., Solomon, D., Kinyangi, J., Grossman, J., O’Neill, B., Skjemstad, J.O., Thies, J., Luizão, F.J., Petersen, J. and Neves, E.G.: 2006, ‘Black carbon increases cation exchange capacity in soils’, Soil Science Society of America Journal 70: 1719-1730.
  4. Mikan, C.J. and Abrams, M.D.: 1995, ‘Altered forest composition and soil properties of historic charcoal hearths in southeastern Pennsylvania’, Canadian Journal of Forestry Research 25, 687-696.
  5. Sombroek, W., Nachtergaele, F.O. and Hebel, A.: 1993, ‘Amounts, dynamics and sequestering of carbon in tropical and subtropical soils’, Ambio 22, 417-426.

Persistence
It is undisputed that biochar is much more persistent in soil than any other form of organic matter that is commonly applied to soil. Therefore, all associated benefits with respect to nutrient retention and soil fertility are longer lasting than with alternative management. The long persistence of biochar in soil also makes it a prime candidate for the mitigation of climate change as a potential sink for atmospheric carbon dioxide. The success of effective reduction of greenhouse gases depends on the associated net emission reductions through biochar sequestration. A net emission reduction can only be achieved in conjunction with sustainable management of biomass production. During the conversion of biomass to biochar about 50% of the original carbon is retained in the biochar, which offers a significant opportunity for creating such a carbon sink (Lehmann, 2007). This promises biochar to become an appropriate tool to contribute a significant wedge in a wider strategy for the mitigation of the anthropogenic greenhouse effect.

Reading:

  1. Baldock JA and Smernik RJ. 2002, ‘Chemical composition and bioavailability of thermally altered Pinus resinosa (Red pine) wood’, Organic Geochemistry 33: 1093-109.
  2. Cheng CH, Lehmann J, Thies JE and Burton S 2008 Stability of black carbon in soils across a climatic gradient. Journal of Geophysical Research (Biogeosciences) 113, G02027.
  3. Lehmann, J.: 2007, ‘A handful of carbon’, Nature 447, 143-144.
  4. 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.
  5. Pessenda, L.C.R., Gouveia, S.E.M. and Aravena, R.: 2001, ‘Radiocarbon dating of total soil organic matter and humin fraction and its comparison with 14 C ages of fossil charcoal’, Radiocarbon 43, 595-601.
  6. Schmidt, M.W.I. and Noack, A.G.: 2000, ‘Black carbon in soils and sediments: analysis, distribution, implications, and current challenges’, Global Biogeochemical Cycles 14, 777-794
  7. Seifritz, W.: 1993, ‘Should we store carbon in charcoal?’, International Journal of Hydrogen Energy 18, 405-407.
  8. Shindo, H.: 1991, ‘Elementary composition, humus composition, and decomposition in soil of charred grassland plants’, Soil Science and Plant Nutrition 37, 651-657.

More:

  1. Lehmann (Cornell University)
  2. Biochar (wiki)
  3. IBI

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