Biochar is the solid remains of any organic material that has been heated to at least 250°C in a zero-oxygen or oxygen-limited environment, which is intended to be mixed with soils. If the solid remains are not suitable for addition to soils or will be burned as a fuel, the material is char, not biochar. Biochar reduces atmospheric greenhouse gas concentrations, improves many soils, potentially enhances crop productivity, provides some energy for human use and can be used to safely dispose of certain waste materials. Most commonly, biochar is produced using a process called pyrolysis.

Historical Pedigree

Biochar, or more accurately other forms of plant and animal char, have been used to enhance soils for millennia. The strongest evidence of the beneficial effects of char additions to soils are in the terra preta soils of the northern Amazon, where - through native land management - dark, highly fertile soils with very high levels of both stable (char) carbon and organic carbon were established and remain today. Char was also added historically to soils in parts of northern Europe (including Netherlands, NW Germany and Belgium). Chars have been, and still are being, used today as soil amendments, for example in Japan and West Africa.

Biochar Images

Scanning electron microscopy (SEM) can be used to examine the microscopic structure of biochar. Below are some images of different biochar types that have been examined at Edinburgh.Please do not use any of the photographs without obtaining prior permission.