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)

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.

Benefits include:

• 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.

Source: Biochar use in soils (International Biochar Initiative) and Biochar – a key technology for the planet

Please click here to access the Soil Association information sheet which gives you an overview of the potential of biochar.

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.

Source: Biochar – A key technology for the planet

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.

Sources: Biochar technology (International Biochar Initiative) and What is Biochar? (UK Biochar Research Centre)