FAQ's
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We aim to answer any questions that farmers and other agricultural professionals or just visitors may have about working with biochar.
What is biochar?
Biochar is a carbon-rich substance produced by a thermochemical process called pyrolysis. Pyrolysis is the thermal decomposition of biomass which occurs at a very high temperature and under oxygen-deprived conditions. Three by-products are produced: biochar (solid), bio-oil (liquid) and syngas (gas)
What are the claimed for benefits of biochar?
Biochar, derived from agricultural and forestry residues, can be added to soils as a potential long-term carbon sequestration method, effectively capturing carbon dioxide from the atmosphere for thousands of years. Additionally, it serves as a soil conditioner by raising the pH of acidic soils, enhancing water retention, regulating nutrient exchange between plants and soil, and improving aeration and structure, particularly in heavy soils. These benefits contribute to better plant health, increased yields, and reduced fertilizer losses.
What can biochar be produced from?
Biochar is a material that can be made from various organic sources, including organic waste with no alternative use. It can be produced from virgin wood, domestic green waste, agricultural residues (such as crop waste and livestock manure), and forestry byproducts. However, waste wood is unsuitable for biochar production due to potential contaminants, which could harm plant growth and pose risks to groundwater and the food chain if applied to soil.
Companies like Oxford Biochar, based in Oxford, manufacture biochar on a commercial scale. To maintain quality, the production process requires careful monitoring and control of temperature and pressure.
In Europe, biochar producers can apply for a European Biochar Certificate (EBC), which ensures sustainable production, processing, and sales while providing customers with recognised quality standards.
How widely used is biochar and by whom?
Gardeners are already using biochar to enhance water and nutrient retention, improve soil drainage and aeration, and promote plant health. The Royal Horticultural Society (RHS) offers guidance on its use.
In UK agriculture, biochar has been tested in trials, including one conducted by Innovative Farmers, where it was fed to beef cattle to assess its impact on manure ammonium and nitrate content, ammonia emissions, worm burden, pH, and its effect on grass growth. However, the trial found no detectable improvements in cattle health or grass growth. Similarly, a three-year field study in Wales examined the effects of biochar on soil quality and crop performance, finding no negative impacts on crop growth, nutrition, or soil quality.
Research has also been conducted with farmers in Norway and Poland to explore their knowledge and perceptions of biochar. Farmers in these studies expressed interest in its potential to enhance soil quality and boost crop yields.
How much biochar needs to be applied to see benefits to soil and crops?
Farmers typically apply between 10 to 20 tonnes of biochar per hectare, though trials have demonstrated that up to 100 tonnes per hectare can be added gradually over several years without negatively affecting plant growth or soil health. However, the Environment Agency currently permits only 1 tonne per hectare to be applied within a 12-month period. Following discussions with the agency, it is expected that approximately 10 tonnes per hectare will be used in these trials.
How long will it take to see any benefits of biochar to my soil and crops?
Effects on plant growth can be seen within 1 year due to the addition of nutrients from the biochar (e.g. phosphorus, P, and potassium, K). Generally, most beneficial effects are seen in the first few years. In some cases, benefit to crop growth is also seen, but benefits are seen in the soil (e.g. in terms of increasing soil C content).
What is the evidence that biochar contributes to carbon sequestration?
Biochar helps combat climate change by capturing and storing atmospheric carbon while also increasing soil carbon levels in agroecosystems. Additionally, it has the potential to reduce nitrous oxide emissions from nitrogen fertilizer applications.
A typical UK soil contains around 70 tonnes of carbon per hectare in organic matter. Applying biochar at a rate of 10 tonnes per hectare can increase soil carbon content by approximately 10%, as biochar consists of around 70% carbon.
How will biochar be applied to a field?
Biochar can be applied using a conventional Farm Yard Manure (FYM) spreader if it is mixed with FYM beforehand. However, it is advisable to consult the local environment agency to justify the co-application for operational purposes.
Alternatively, biochar can be applied directly to land using specialized equipment, such as a lime spreader. The Biochar Demonstrator has successfully used a gritter for small plots and plans to scale up to larger plots using lime spreading equipment.
The ideal time to apply biochar to arable fields is before cultivation or crop establishment. For crops harvested in 2023, such as winter wheat, this would mean applying biochar in autumn 2022.