Location: National Soil Erosion ResearchTitle: Biochar Author
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 3/12/2014
Publication Date: 6/17/2014
Publication URL: http://handle.nal.usda.gov/10113/799516
Citation: Hass, A., Gonzalez, J.M. 2014. Biochar. In: Lopez-Valdez, F. and Fernandez-Luqueno, F. Fertilizers: Components, Uses in Agriculture and Environmental Impacts. Hauppauge, NY: Nova Science Publishers. ebook. p. 95-123. Interpretive Summary: Biochar, a type of charcoal made from plants, waste, and residues, can be used as soil amendment to improve soil properties. Since the carbon in the biochar becomes more resistant to microbial degradation, then the land application of biochar is promoted as a beneficial for carbon capture and one way to reduce gas emissions to the atmosphere. The agronomical effectiveness of biochar and its effects on soil properties is highly dependent on the process and feedstock. The recovery of nutrients in biochar tends to decrease with temperature while the remaining nutrients become more stable but less available for plant uptake. When the feedstock is charred at higher temperatures, the liming potential of biochar increases, which contributes to increase the pH of acidic and infertile soils where biochar addition has shown to be most effective and consistent to improve soil fertility. Biochar showed to improve several soil quality indicators including the capacity to retain nutrients of positive charge, bulk density, and carbon content. When biochar is produced as the main product under slow charring conditions, biochar can be engineered to achieve desired characteristics; conversely, when produced as a byproduct in fast charring, additional steps are needed to improve desired biochar characteristics in order to maximize biochar impact on soil fertility. This research provides information to land managers for the proper use of biochars to achieve their maximum benefits in soil quality and plant nutrition improvement.
Technical Abstract: Biochar, a carbonaceous material produced by pyrolysis, can be used as soil amendment to improve soil properties. As some of the carbon is converted into a recalcitrant form rendering it more resistant to biodegradation, land application of biochar is promoted as a beneficial mean for carbon sequestration and as an offsetting mechanism for carbon emission. The agronomic efficacy of biochar and its effects on improving soil properties is highly process and feedstock dependent. Feedstock nutrient recovery in biochar tends to decrease with temperature while remaining nutrients redistribute into more recalcitrant and less readily available forms for plant uptake. Pyrolysis of biomass at higher temperature increases biochar liming capacity which contributes to increase the pH of dystrophic, acidic and highly weathered soils where biochar improvement of soil fertility has shown to be most pronounced and consistence. Biochar showed to improve several soil quality indicators including CEC, bulk density, and carbon content. When produced as the main product under slow pyrolysis conditions, biochar can be engineered to achieve desired characteristics; conversely, when produced as a byproduct in fast-pyrolysis, post-production augmentation procedures to improve desired biochar characteristics need to be considered in order to maximize biochar impact on soil fertility. Effect of pyrolysis conditions, feedstock source and composition on biochar characteristics and effect of biochar application on soil fertility are discussed.