Agro-wastes as precursors of biochar, a cleaner adsorbent to remove pollutants from aqueous solutions

There are several types of agricultural wastes and agro-industrial wastes, which are widely available. According to global statistics, the worldwide production and the harvested area to produce rice, soybean, barley, coffee, and other grains have increased in recent years. The chemical composition of these materials is mainly lining, hemicellulose, and cellulose. Due to their chemical composition and carbon content, these materials are helpful to produce biochar and activated carbon, as well as produce biofuel and alcohol, as an additive, and other uses. Biochar can be produced by pyrolysis, gasification, and torrefaction and can be physically or chemically activated to enhance its properties as adsorbent material of heavy metals, dyes, and pharmaceutical pollutants. However, despite its properties as an adsorbent or useful feedstock to produce valuable products, the use of biochar could imply some risks for human health and ecosystems, besides the production, and activation of biochar implies environmental impacts.