U.S.-FocUSed Biochar report - BioEnergy Lists

tion of N and S) get enriched in the biochar with increasing losses of oxygen, hydrogen and carbon (Gaskinet al. 2008). The nutrient contents of biochars may be enriched by co-composting with nutrient rich materials.Such applications were already recommended by Allen (1847). The production of biochar does not compete withcomposing but could be a supplementary approach. In general nutrient rich materials or materials with a lowcarbon-to-nitrogen ratio (C:N) and high moisture content make a good compost whereas materials with a highC:N ratio (>30) are less suitable for composting. Woody materials are rather resistant to decomposition, requirelong composting times and additional nitrogen fertilization. Available carbon (wood waste) may also negativelyinfluence compost stability and quality (N-immobilization). Therefore such biomass waste is frequently burnedor is deposited in landfills. These biomass sources are ideally suited for biochar production and can either bemixed with compost or used as a bulking agent during composting. Due to its recalcitrance, the use of biochar asa bulking agent does not result in the addition of readily available carbon, and thus its use does not increase theeffective C:N ratio. Recent research has shown that co-composting of biochar with nitrogen rich manures reducesnitrogen losses due to ammonia (NH3) volatilization by up to 50% (Steiner et al. 2010).Asai et al. (2009) found improved soil water permeability and soil water holding capacity and thereby plant wateravailability in rice plantations after biochar amendments. This was also found in temperate soils (Briggs 2005)but might depend on soil properties such as clay content (Glaser, Lehmann, and Zech 2002). A 2% switchgrassbiochar addition to a sandy Norfolk soil in the southeastern U.S. could significantly improve soil water retention(Novak, Lima et al. 2009) and was also found in the Midwestern soil by Laird et al. (2010).As other organic matter, biochar additions may influence the environmental fate and performance of pesticides.Sheng et al. (2005) found that wheat char was highly effective sorbent for the pesticides, and its presence (1% byweight) in soil contributed 70% to the pesticide sorption. It is advantageous if adsorbed pesticides are not carrieddownward through the soil profile with percolating water. Thus application of biochar, may offer an importantstrategy for reducing pesticide leaching. The nature of organic matter in soil plays a key role in the performanceof applied pesticides (Gevao, Semple, and Jones 2000). However, if biochar affects herbicide sorption in soil, itmay in turn affect herbicide persistence (Spokas et al. 2009; Yu, Ying, and Kookana 2009). Despite greater persistenceof the pesticide residues in biochar-amended soils, the plant uptake of pesticides decreased markedly withincreasing biochar content of the soil in a study by Yu, Ying, and Kookana (2009). Yet charcoal was reported toprevent fungus disease (rust in wheat, and mildew in other crops) (Allen 1847) and thus might reduce pesticiderequirements. Recent research showed that relatively small (1% by weight) biochar additions to soil and pottingmedium induced a systemic resistance against two foliar fungal pathogens (B. cinerea and L. taurica) in bothpepper and tomato plants, and to a pest (P. latus) in pepper plants (Elad et al. 2010).Carbon SequestrationCarbon dioxide is removed from the atmosphere through photosynthesis and stored in organic matter. Whenplants grow they utilize sunlight, CO 2 and water (H 2 O) to synthesize organic matter and release oxygen (O 2 ).This accumulated carbon is returned to the atmosphere by decomposition of dead plant tissue or disturbances,such as fire, in which large amounts of organic matter are oxidized and rapidly transferred into CO 2 . Eighty toninety percent of the carbon from crop residues in the field is lost due to decomposition in the first 5 to 10 years(Lehmann, Gaunt, and Rondon 2006). Humus enrichment follows a saturation curve, approaching a new equilibriumlevel after some 50 to 100 years. The new SOC level drops rapidly again, as soon as the required carefulmanagement is no longer sustained (Sauerbeck 2001). Baker et al. (2007) reviewed literature on conventionalplowing and conservation tillage and did not find consistent accrual of SOC due to conservation tillage. Heassumes that root growth and distribution might be affected by conservation tillage leading to increased SOCin surface horizons but SOC depletion in subsoil horizons. Furthermore the addition of degradable crop residuesand reduced tillage systems is not always beneficial. Increases in nitrous oxide (N 2 O) and methane (CH 4 )emissions, increased susceptibility for pests and diseases, and nitrogen immobilization are among the observednegative effects. These adverse ramifications of accumulating crop residues are one reason why many farmersBiochar in agricultural and forestry applications in:Biochar from Agricultural and Forestry Residues – A Complimentary Use of “Waste” Biomass5