Biochar is defined as a carbon-rich solid obtained by the thermal decomposition of organic matter under a limited supply of oxygen and at relatively low temperatures Due to its molecular structure, the carbon in the resulting biochar is chemically and biologically in a much more stable form than that in the original raw material, and therefore can be stored in soils for much longer. Scientific evidence shows that turnover time of carbon in biochar ranges from centuries to millennia, depending on feedstock and process conditions. Also, the biochar application to soil can reduce the emissions of other green house gases such as methane and nitrous oxide emissions.

Biochar can be prepared from the thermal treatment of different organic feedstocks such as wood, biomass crops, agricultural by-products such as cereal straw and hazelnuts, which have been used for the production of biochar as well as from sewage sludge or urban waste. The application of biochar in soil has several benefits in soil quality and therefore in crop yields. For example, biochar can increase soil-water-holding capacity and improve the structure of soil, improve soil biological properties, increase cation exchange capacity and pH increasing agricultural yield and at the same time contribute to carbon sequestration due to carbon stability of biochar materials. Recently, biochar has been used in multiple ways in soil remediation due to its adsorption of pesticides or metals, both in laboratory and field. Indeed, biochar can reduce plant-available heavy metals. Another use of biochar is as growing media to crop production in greenhouses reducing the environmental impact of peat excavation. It must be taken into account that more than 100 years is necessary for the formation of 6cm of peat.