Characterization of an enriched biochar

• Enriched biochar (EB) was synthesized by mixing biochar with clay and minerals.
• Microstructure of EB was studied with SEM and TEM.
• Interactions between the organic and mineral phase were observed.
• The half-life of enriched biochar-C was estimated to be 104 years.
• The cumulative mineralization rate of EB is lower compared to high ash biochars.

Carbonized materials are responsible for maintaining a high level of fertility and soil organic matter in soils such as the Amazonian Dark Earths, also known as Terra Preta. It is hypothesized that an enriched biochar, which will have long term stability similar to Terra Preta, can be synthesized by mixing biochars with manures, minerals and clays and heating the mixture at low temperatures. This treatment will promote bonding between the mineral and the organic phases, which may occur naturally after several years of aging in soil. This paper describes the characterization of an enriched biochar by a range of analytical methods. Examination of the enriched biochar showed that it has high concentrations of exchangeable cations, available phosphorus and high acid neutralizing capacity. Structural analysis of the enriched biochar reveals a microstructure that suggests that bonding has indeed occurred between the biochar and mineral phases. Using natural 13C abundance and a two-pool exponential model, the half-life of enriched biochar-C was estimated to be 104 years in a clayey soil.