biochar

Biochar is a form of charcoal, sometimes modified, that is intended for organic use, as in soil. It is the lightweight black remnants remaining after the pyrolysis of biomass, consisting of carbon and ashes. Despite its name, biochar is sterile immediately after production and only gains biological life following assisted or incidental exposure to biota. Biochar is defined by the International Biochar Initiative as the "solid material obtained from the thermochemical conversion of biomass in an oxygen-limited environment". Biochar is mainly used in soils to increase soil aeration, reduce soil emissions of greenhouse gases, improve soil fertility, reduce nutrient leaching, reduce soil acidity, and potentially increase the water content of coarse soils. Biochar application may increase soil fertility and agricultural productivity. However, when applied excessively or made from feedstock unsuitable for the soil type, biochar soil amendments also have the potential for negative effects, including harming soil biota, reducing available water content, altering soil pH, and increasing salinity. Beyond soil application, biochar can be used for slash-and-char farming, for water retention in soil, and as an additive for animal fodder. There is an increasing focus on the potential role of biochar application in global climate change mitigation.…

Biochar is a form of charcoal, sometimes modified, that is intended for organic use, as in soil. It is the lightweight black remnants remaining after the pyrolysis of biomass, consisting of carbon and ashes. Despite its name, biochar is sterile immediately after production and only gains biological life following assisted or incidental exposure to biota. Biochar is defined by the International Biochar Initiative as the "solid material obtained from the thermochemical conversion of biomass in an oxygen-limited environment". Biochar is mainly used in soils to increase soil aeration, reduce soil emissions of greenhouse gases, improve soil fertility, reduce nutrient leaching, reduce soil acidity, and potentially increase the water content of coarse soils. Biochar application may increase soil fertility and agricultural productivity. However, when applied excessively or made from feedstock unsuitable for the soil type, biochar soil amendments also have the potential for negative effects, including harming soil biota, reducing available water content, altering soil pH, and increasing salinity. Beyond soil application, biochar can be used for slash-and-char farming, for water retention in soil, and as an additive for animal fodder. There is an increasing focus on the potential role of biochar application in global climate change mitigation. Due to its refractory stability, biochar can stay in soils or other environments for thousands of years. This has given rise to the concept of biochar carbon removal, a process of carbon sequestration in the form of biochar. Carbon removal can be achieved when high-quality biochar is applied to soils, or added as a substitute material to construction materials such as concrete and tar. For crops that are not exclusively for biochar production, the residue-to-product ratio (RPR) and the collection factor (CF), the percent of the residue not used for other things, measure the approximate amount of feedstock that can be obtained. For instance, Brazil harvests approximately 460 million tons (MT) of sugarcane annually, with an RPR of 0.30, and a CF of 0.70 for the sugarcane tops, which normally are burned in the field. This translates into approximately 100 MT of residue annually, which could be pyrolyzed to create energy and soil additives. Adding in the bagasse (sugarcane waste) (RPR=0.29, CF=1.0), which is otherwise burned (inefficiently) in boilers, raises the total to 230 MT of pyrolysis feedstock. Some plant residue, however, must remain on the soil to avoid increased costs and emissions from nitrogen fertilizers.

Properties

The physical and chemical properties of biochars as determined by feedstocks and technologies are crucial. Characterization data explain their performance in a specific use. For example, guidelines published by the International Biochar Initiative provide standardized evaluation methods. Properties can be categorized in several respects, including the proximate and elemental composition, pH value, and porosity. The atomic ratios of biochar, including H/C and O/C, correlate with the properties that are relevant to organic content, such as polarity and aromaticity. A van-Krevelen diagram can show the evolution of biochar atomic ratios in the production process. In the carbonization process, both the H/C and O/C atomic ratios decrease due to the release of functional groups that contain hydrogen and oxygen. Production temperatures influence biochar properties in several ways. The molecular carbon structure of the solid biochar matrix is particularly affected. Initial pyrolysis at 450–550 °C leaves an amorphous carbon structure. Temperatures above this range will result in the progressive thermochemical conversion of amorphous carbon into turbostratic graphene sheets. Biochar conductivity also increases with production temperature. Important to carbon capture, aromaticity and intrinsic recalcitrance increases with temperature. Biochar Production in Namibia (Video) International Biochar Initiative Biochar-us.org

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