Environmental issues related to bioenergy

Extensive efforts have been made in the conversion of biomass into renewable energy using thermochemical and biochemical approaches. During biomass thermochemical conversion, nitrogen oxides (NOx), particulate matter (PM), and tar are the major environmental emissions generated. NOx and PM generated in thermochemical conversion processes can be effectively removed by existing technologies, and tar can be reduced through end treatment and in situ process control. In bioconversion of biomass, the major environmental emissions are volatile organic compounds (VOCs), sulfur-containing gases (e.g., H2S), wastewater, and biogas slurry. Biogas slurry can be utilized as a value-added resource, and wastewater and VOCs can be treated via physical-chemical or biological methods. From a green engineering perspective, the most effective approach is the source reduction of pollution, which can be achieved through process improvement/control or the development of new conversion processes. Employing emission treatment and source-reduction approaches, bioenergy-related environmental issues can be minimized. Developing new industrial technologies or processes that use biomass as a source of energy or chemicals is the future direction of clean production.