Chapter 15 - Biochar production and modification for environmental improvement

Abstract

Biochar is a carbon-rich solid produced from biomass (e.g., plant-based residues, manures, and sewage sludge) by means of thermochemical treatment technologies (e.g., pyrolysis, carbonization). Biochar has a high specific surface area and well-developed pore structure, which is favorable for adsorption. Composed of a stable aromatization structure, and with many oxygen-containing surface functional groups, biochar normally has a negatively charged surface, which can adsorb and fix inorganic ions in water, soil, or sediments. With alkaline surface functional groups favorable for acidic gas adsorption (e.g., CO2, SO2, NOx), biochar also has an indirect impact on global climate change through soil environmental behavior. Obtained from biomass thermochemical treatment that can be returned to the field, biochar application alleviates the energy crisis, and fixes carbon in the biomass in the soil, and immobilizes and reduces the greenhouse gas emissions. The character of aromatic-rich structure makes biochar a possible source of highly aromatic structural components in soil humus and it also plays an important role in stabilizing soil organic components, increasing soil carbon capacity, retaining soil nutrients, improving soil fertility, and maintaining soil ecosystem balance. This chapter focuses on the research progress in biochar production, activation, modification, and application. In many studies, biochar has demonstrated its excellent performance from the perspective of wastewater treatment, soil improvement, and contaminated gas treatment. Standardized biochar production and application rules are necessary to make biochar play a full-fledged role in bio-based residues recycling and greenhouse gas emission reduction.