Biochar
[8] 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)[9] in pits or trenches.
[11] 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.
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.
[16] 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.
[citation needed] Smallholder farmers in developing countries easily produce their own biochar without special equipment.
Factors that influence the choice of system type include the cost of transportation of the liquid and solid byproducts, the amount of material to be processed, and the ability to supply the power grid.
[30] At the 2009 International Biochar Conference, a mobile pyrolysis unit with a specified intake of 1,000 pounds (450 kg) was introduced for agricultural applications.
[32] 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.
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.
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.
[48][49][50] Biomass burning and natural decomposition releases large amounts of carbon dioxide and methane to the Earth's atmosphere.
[50] Biochar carbon remains in the ground for centuries, slowing the growth in atmospheric greenhouse gas levels.
Simultaneously, its presence in the earth can improve water quality, increase soil fertility, raise agricultural productivity, and reduce pressure on old-growth forests.
[62] A 2010 report estimated that sustainable use of biochar could reduce the global net emissions of carbon dioxide (CO2), methane, and nitrous oxide by up to 1.8 billion tonnes carbon dioxide equivalent (CO2e) per year (compared to the about 50 billion tonnes emitted in 2021), without endangering food security, habitats, or soil conservation.
[63] A 2021 review estimated potential CO2 removal from 1.6 to 3.2 billion tonnes per year,[64] and by 2023 it had become a lucrative business renovated by carbon credits.
[66] In 2021 the cost of biochar ranged around European carbon prices,[67] but was not yet included in the EU or UK Emissions Trading Scheme.
[80][81] Due to its porosity, the small holes in biochar can keep water and dissolved minerals in the upper layers of soil, assisting plant growth and reducing the need for and expense of fertilizer.
[91] The application of compost and biochar under FP7 project FERTIPLUS had positive effects on soil humidity, crop productivity and quality in multiple countries.
[92] Gardeners taking individual action on climate change add biochar to soil,[99] increasing plant yield and thereby drawing down more carbon.
Biochar costs in developed countries vary from $300–$7,000/tonne, which is generally impractical for the farmer/horticulturalist and prohibitive for low-input field crops.
[6] Switching from slash-and-burn to slash-and-char farming techniques in Brazil can decrease both deforestation of the Amazon basin and carbon dioxide emission, as well as increase crop yields.
[111][110] Pow's work led to two further trials on dairy cattle, yielding reduced odour and increased milk production.
[114] Biochar has been shown to be an effective SCM, reducing concrete production emissions while maintaining required strength and ductility properties.
[118] Compared to other SCMs from industrial waste streams (such as fly ash and silica fume), biochar also showed decreased toxicity.
[119] Adapting slow pyrolysis in large biomass fields and installations enables the generation of biochar slurries with unique characteristics.
These slurries are becoming promising fuels in countries with regional areas where biomass is abundant, and power supply relies heavily on diesel generators.
[139][140] Long-term effects of biochar on carbon sequestration have been examined using soil from arable fields in Belgium with charcoal-enriched black spots dating from before 1870 from charcoal production mound kilns.
This study showed that soil treated over a long period with charcoal showed a higher proportion of maize-derived carbon and decreased respiration, attributed to physical protection, carbon saturation of microbial communities, and, potentially, slightly higher annual primary production.
The combined spectroscopy-microscopy approach revealed the accumulation of aromatic carbon in discrete spots in the solid phase of microaggregates and its co-localization with clay minerals for soil amended with raw residue or biochar.
