Biochar can and should be made from biomass waste materials. Making biochar from biomass waste materials should create no competition for land with any other land use option—such as food production or leaving the land in its pristine state.
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.
Large amounts of agricultural, municipal, and forestry biomass are currently burned or left to decompose and release CO2 and methane back into the atmosphere. They also can pollute local ground and surface waters—a large issue for livestock wastes. Using these materials to make biochar not only removes them from a pollution cycle, but biochar can be obtained as a by-product of producing energy from this biomass. Feedstocks must not contain unacceptable levels of toxins such as heavy metals which can be found in sewage sludge and industrial or landfill waste.
It is important to study all the aspects of feedstock supply on a local community/business before setting up a biochar operation. Feedstock availability can vary year to year and within years. In developing country areas where feedstocks are often used as heating and/or cooking fuel, biochar production can be an important side benefit if done sustainably. The biochar can then be used on fields to potentially increase food production by improving soil fertility (See Chapter 9 Biochar Systems in Biochar for Environmental Management for a series of case studies on biochar production and sustainable feedstock models in developing countries).
The composition of biochar (the amount of carbon, nitrogen, potassium, calcium, etc) depends on the feedstock used and the duration and temperature of pyrolysis. As an example, biochar produced from feedstocks which have greater contents of potassium (such as animal litters) often have higher potassium contents than biochar made entirely from wood (which often have higher carbon contents). However, pyrolysis conditions greatly affect nutrient properties contents and so biochar should be tested on a batch by batch basis to determine specific properties.
The choice of feedstock will be affected by the biomass resources in the immediate area and availability. Due to collection, and transport and storage costs, it often makes the most economic sense to use local feedstocks (if they are also an environmentally sustainable option). The most basic costs and benefits to consider with feedstock choices are highlighted below:
See Chapters in Biochar for Environmental Management: Chapter 1: Biochar for Environmental Management; Chapter 5: Nutrient Properties and their Enhancement; Chapter 9 Biochar Systems; and Chapter 19: Economics of Biochar Production, Utilization, and Greenhouse Gas Offsets.