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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, 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.
The word "biochar" is a late-20th century English neologism derived from the Greek word 'βίος' (bios, 'life') and 'char' (charcoal produced by carbonization of biomass). It is recognized as charcoal that participates in biological processes found in soil, aquatic habitats, and animal digestive systems.[citation needed]
Pre-Columbian Amazonians produced biochar by smoldering agricultural waste (i.e., covering burning biomass with soil) in pits or trenches. It is not known if they intentionally used biochar to enhance soil productivity. European settlers called it terra preta de Indio. Following observations and experiments, one research team working in French Guiana hypothesized that the Amazonian earthworm Pontoscolex corethrurus was the main agent of fine powdering and incorporation of charcoal debris in the mineral soil.
Biochar is a high-carbon, fine-grained residue that is produced via pyrolysis. It is the direct thermal decomposition of biomass in the absence of oxygen, which prevents combustion, and produces a mixture of solids (biochar), liquid (bio-oil), and gas (syngas) products.
Gasifiers produce most of the biochar sold in the United States. The gasification process consists of four main stages: oxidation, drying, pyrolysis, and reduction. Temperature during pyrolysis in gasifiers is 250–550 °C (523–823 K), 600–800 °C (873–1,073 K) in the reduction zone, and 800–1,000 °C (1,070–1,270 K) in the combustion zone.
The specific yield from pyrolysis (the step of gasification that produces biochar) is dependent on process conditions such as temperature, heating rate, and residence time. These parameters can be tuned to produce either more energy or more biochar. Temperatures of 400–500 °C (673–773 K) produce more char, whereas temperatures above 700 °C (973 K) favor the yield of liquid and gas fuel components. Pyrolysis occurs more quickly at higher temperatures, typically requiring seconds rather than hours. The increasing heating rate leads to a decrease in biochar yield, while the temperature is in the range of 350–600 °C (623–873 K). Typical yields are 60% bio-oil, 20% biochar, and 20% syngas. By comparison, slow pyrolysis can produce substantially more char (≈35%); this contributes to soil fertility. Once initialized, both processes produce net energy. For typical inputs, the energy required to run a "fast" pyrolyzer is approximately 15% of the energy that it outputs. Pyrolysis plants can use the syngas output and yield 3–9 times the amount of energy required to run.
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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, 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.
The word "biochar" is a late-20th century English neologism derived from the Greek word 'βίος' (bios, 'life') and 'char' (charcoal produced by carbonization of biomass). It is recognized as charcoal that participates in biological processes found in soil, aquatic habitats, and animal digestive systems.[citation needed]
Pre-Columbian Amazonians produced biochar by smoldering agricultural waste (i.e., covering burning biomass with soil) in pits or trenches. It is not known if they intentionally used biochar to enhance soil productivity. European settlers called it terra preta de Indio. Following observations and experiments, one research team working in French Guiana hypothesized that the Amazonian earthworm Pontoscolex corethrurus was the main agent of fine powdering and incorporation of charcoal debris in the mineral soil.
Biochar is a high-carbon, fine-grained residue that is produced via pyrolysis. It is the direct thermal decomposition of biomass in the absence of oxygen, which prevents combustion, and produces a mixture of solids (biochar), liquid (bio-oil), and gas (syngas) products.
Gasifiers produce most of the biochar sold in the United States. The gasification process consists of four main stages: oxidation, drying, pyrolysis, and reduction. Temperature during pyrolysis in gasifiers is 250–550 °C (523–823 K), 600–800 °C (873–1,073 K) in the reduction zone, and 800–1,000 °C (1,070–1,270 K) in the combustion zone.
The specific yield from pyrolysis (the step of gasification that produces biochar) is dependent on process conditions such as temperature, heating rate, and residence time. These parameters can be tuned to produce either more energy or more biochar. Temperatures of 400–500 °C (673–773 K) produce more char, whereas temperatures above 700 °C (973 K) favor the yield of liquid and gas fuel components. Pyrolysis occurs more quickly at higher temperatures, typically requiring seconds rather than hours. The increasing heating rate leads to a decrease in biochar yield, while the temperature is in the range of 350–600 °C (623–873 K). Typical yields are 60% bio-oil, 20% biochar, and 20% syngas. By comparison, slow pyrolysis can produce substantially more char (≈35%); this contributes to soil fertility. Once initialized, both processes produce net energy. For typical inputs, the energy required to run a "fast" pyrolyzer is approximately 15% of the energy that it outputs. Pyrolysis plants can use the syngas output and yield 3–9 times the amount of energy required to run.
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