Improved utilization of organic waste for fertilizer has significant worldwide economic and ecological potential and the use of plasma can help unlock this potential. Organic waste that are used as fertilizer includes animal waste (manure and urine), human sewage, food waste and biogas digestate. Air plasma treatment of aqueous solutions of organic fertilizer (plasma activated organic fertilizer, or PAOF) has multiple advantages such as reduction or elimination of atmospheric emission of volatile organic carbon (VOC) compounds, CH4 and NH3 . Although the emission of N2O from the fertilized soil may be enhanced by PAOF, we surmise that N2O emission at large is reduced because the losses of reactive nitrogen from the agro-ecosystem (which cause N2O emissions elsewhere) are significantly reduced. In addition, PAOF will improve the commercial value of fertilizer that can be made from organic waste. This includes altering both the quantity and chemical form of N contained in the organic fertilizer, as well as odor reduction. PAOF appears to function using chemical reactivity similar to well-studied natural antimicrobial processes, resulting in significant antibacterial effects in treated waste. The commercial viability of PAOF depends on numerous factors, the most important of which are the energy efficiency and capital costs associated with the plasma process and associated processing equipment; the cost of electricity; and the nature and extent of government regulations regarding pollution from organic waste and all types of fertilizer. We estimate that if the total cost of plasma production of reactive nitrogen is below about €2/kg N–€3/kg N, the process will be economically viable in the absence of penalties or subsidies.
David B. Graves, Lars B. Bakken, Morten B. Jensen, Rune Ingels
Department of Chemical and Biomolecular Engineering, University of California, Berkeley, USA
Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, Ås, Norway
N2 Applied, Oslo, Norway
Plasma Chemistry and Plasma Processing
38, Issue 6