Environmental applications of non-thermal plasmas

The use of non-thermal plasmas in a wide range of environmental applications covers a very broad and diverse field with a long history of extensive laboratory, bench-scale investigations, in particular during the past two decades. However, only a few research accomplishments and breakthroughs were successfully translated into economically viable technologies for large-scale industrial applications, most notably electrostatic precipitators using corona discharges and ozonizers using dielectric barrier discharges. In this chapter, we describe the current status of electrostatic precipitators and ozonizers. Moreover, we also try to identify some of the bottlenecks that prevent other non-thermal plasma-based environmental technologies from becoming widely applicable. As an example, we look at the use of non-thermal plasmas for the treatment of gaseous and (to a lesser extent) liquid waste streams, with an emphasis on waste streams containing volatile organic compounds (VOCs). Bottlenecks preventing or slowing down the rapid and efficient translation of successful bench-scale studies to widely used industrial technologies include but are not limited to the identification, quantification, and control of by-products produced in the plasma chemical reactions and establishing carbon closure (i.e. the accounting of the ultimate fate of each initial carbon atom that is exposed to the plasma). This chapter will not address any aspects of waste remediation using thermal plasmas such as gasification of solid and liquid waste streams.