Full-Scale Biosolids Drying and Pyrolysis

Polyfluoroalkylated substances (PFAS) and other contaminants of emerging concern (CECs) pose a major threat to the future land application of biosolids. Anaergia has developed a high temperature pyrolysis technology that converts biosolids into a pyrolyzed biosolids fertilizer product with no detectable level of PFAS or CECs. This technology will soon be commissioned at the Rialto Bioenergy Facility (RBF) in Southern California. In developing this technology, Anaergia conducted bench and pilot scale trials to study the conditions required to eliminate PFAS and develop a mass and energy balance for a full-scale pyrolysis system. Trials showed that pyrolyzed biosolids produced at 650oC showed no measurable level of common PFAS or CECs. The pyrolysis system at RBF will be designed to produce about 0.4 metric tons of pyrolyzed biosolids per metric ton of dried solids fed to the system. Perennial ryegrass pot studies showed that grass treated with pyrolyzed biosolids grew faster and developed longer roots than grass treated with dried biosolids and commercial fertilizers. Field studies with commercial food crops in Southern California showed that avocado and lemon crops treated with pyrolyzed biosolids showed no significant difference in leaf tissue and soil analysis than crops treated with conventional synthetic fertilizer products. Further investment in biosolids pyrolysis projects is expected to be driven by government policy limiting the land application of biosolids, demand for sustainable fertilizer products and private sector demand for carbon-removal projects