Biochar can be used to help improve soils, enhance crop productivity, reduce atmospheric greenhouse gas concentrations, provide energy for human use, and to safely dispose of certain waste materials
What is biochar?
Biochar is the solid remains of organic material (such as forestry waste) that has been heated to at least 250°C in a zero-oxygen or oxygen-limited environment (a process known as pyrolysis) and is intended to be mixed with soils. If the solid remains is intended to be burnt as a fuel or is not suitable for addition to soils, the material is classified as being char rather than biochar.
Adapted from: What is Biochar (UK Biochar Research Centre)
Potential benefits from biochar
The main use of biochar is as a carrier and binder for organic nutrients.The successful use of biochar is dependent on it being strategically integrated into organic material cycles.
Research is confirming benefits that could be of use to farmers and growers, particularly in areas with low rainfall or nutrient-poor soils.
- Reduced leaching of nitrogen in to ground water;
- possible reduced emissions of nitrous oxide;
- increased cation-exchange capacity resulting in improved soil fertility;
- moderation of soil acidity;
- increased water retention;
- increased number of beneficial soil microbes.
Please click here to access the Soil Association information sheet which gives you an overview of the potential of biochar.
Livestock farming and fertiliser management
Similar to the natural carbon cycle, biochar in agriculture can be used as a carrier and groundmass for making more efficient use of natural nutrient cycles, particularly in livestock farming and fertiliser management.
It has been found that mixing 1% volume biochar to silage can prevent the formation of mycotoxins, help to bind pesticides and suppress the formation of butyric acid, meaning that fermentation can take place in a perfectly clean manner, thereby improving feed quality.
Research has also found that:
- Incorporating biochar into animal feed can improve animal digestion, increasing the roughage and reducing GHG production.
- Mixing biochar at 10% by volume into litter can help bind liquid nutrients and reduce ammonia emissions. It also helps prevent putrefaction.
- Biochar has been found to bind volatile nutrients and improve the microbial environment when regularly mixed into slurry at 1 – 5% by volume. This can lead to less nutrients being lost, thereby improving the slurry’s fertilising effect and reducing phytotoxicity and GHG emissions.
- After filtering out the liquids, the solids in slurry can be composted together with stable litter, ultimately yielding valuable black earth due to the high biochar content. Through working the black earth and stabilised liquid slurry into the soil, the soil’s propensity to retain water is heightened and infiltration and aeration improved, resulting in increased microbial activity and thus higher yields. Soil acidification is prevented, and fertilisers and pesticides leach into groundwater at a much lower rate.
How is biochar produced?
It is recommended that biochar is made from biomass waste materials and therefore does not create any competition for land with any other land use option such as food production. Biomass waste materials appropriate for biochar production include crop residues (both field residues and processing residues such as nut shells, fruit pits, bagasse, etc), as well as yard, food and forestry wastes, and animal manures.
There are many different ways to make biochar but it is most commonly produced using a process called pyrolysis (which involves heating biomass with little or no oxygen to drive off volatile gasses, leaving carbon behind). Clean energy can be produced in the form of gas or oil along with the biochar. This energy can be recoverable for another use or be burned and released as heat.
What is in biochar?
The composition of biochar (the amount of carbon, nitrogen, potassium, calcium, etc.) depends on the feedstock used and the duration and temperature of pyrolysis. Using pyrolysis, 65% of the carbon originally contained in the biomass can be concentrated and stabilised in the form of biochar. Dependent on the type of biomass used, biochar is composed of 50 – 90% carbon.
To read more, click here.
Want to know more about biochar?
The International Biochar Initiative supports researchers, policy makers, farmers and gardeners committed to sustainable biochar production and use. It provides a host of information that includes background behind the technology involved and how biochar is produced, the application of biochar and potential benefits, and key research being undertaken on a worldwide basis.
The UK Biochar Research Centre (UKBRC) undertakes research on the role of biochar as a carbon storage and sustainable energy technology, and aims to provide an understanding of the agronomic, environmental and socio-economic impacts of biochar. Through their website, in addition to information on the science and history behind the use of biochar, it is possible to access key publications, and information on research and projects being carried out and talks and conferences in the UK.
The UKBRC are conducting field trials to help develop and improve the evidence-base for the agronomic impacts of biochar in different types of agricultural systems. They have been working with four farms in Scotland and England (arable and horticultural); applying differential rates of charcoal fines under different application conditions.
They are also involved in a variety of field experiments over a range of land uses and farming systems within the UK and the USA. These experiments look at the effects of biochar treatments (manipulated biochar), application rates, and biochar combined with additions of lime, manures or crop residues, and their impact on soil carbon sequestration and greenhouse gas production, as well as crop yields, resistance to plant disease, and soil processes.
There are some major uncertainties surrounding the role of biochar, its impacts upon soils and crops, its overall performance and its costs compared to other carbon mitigation options. To read about this, and suggestions on key research questions that need to be addressed before biochar can be widely deployed, click here.
Some useful resources
A Guide to Conducting Biochar Trials (International Biochar Initiative)
Biochar Bibliography (International Biochar Initiative)
Biochar Farm; resources for sustainable use of biochar in agriculture
Get involved! If you would like to take part in trials using biochar, there are opportunities as part of the Big Biochar Experiment. The British Biochar Foundation is a free membership-led organisation that encourages and facilitates sustainable use of biochar in the UK and welcomes partipation from all sectors.