Morphology and environmentally persistent free radicals on biochars: A review

Abstract

This paper examines the morphology and environmentally persistent free radicals on biochars. It is true that the increase in population has led to exponential increase in demand for energy leading to gradual depletion of fossil fuel reserves. Therefore arises the need to search for alternative renewable clean and sustainable energy resource. Biomass derived fuels offers the best alternative to fossil fuel. Pyrolysis is one of the techniques used to produce biofuel from biomass. Thermal decomposition of biomass in limited supply of oxygen leads to emissions of complex matrices that affect biofuel utilization and stability. The major by-products from biomass pyrolysis include liquid oil, biochar and gases depending on operating conditions such as temperature, particle size, heating rate and reactor configuration. Biochars generated tend to find its use majorly in industry, agriculture and cleaning of industrial waste. Nonetheless biochars may contain organic compounds such as furans, aldehydes, polyaromatic hydrocarbons (PAHS) and environmentally persistent free radicals which are of toxic, carcinogenic, cause oxidative stress and mutagenic. This review therefore focuses on the characteristics of biochar in terms of morphology and the nature of persistent free radicals embedded on the surface of the biochar. It is notable that the information on optimum conditions for production of biochars free of persistent free radicals is scanty if any.