Evaluation of Solid‐State Fermentation Techniques to Dispose of Atrazine and Carbofuran

Abstract

AbstractMethods to dispose of unused concentrated and dilute formulated pesticide suspensions or solutions such as rinsate are urgently needed by small‐scale farm operators and applicators. The suitability of solid‐state fermentation (SSF) techniques to dispose of atrazine (2‐chloro‐4‐[ethylamino]‐6‐[isopropylamino]‐1,3,5‐triazine, purity 99.0%) and carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate, purity 99.0%) formulations was evaluated. Pesticides were added to bioreactors containing either sphagnum peat moss or steam‐exploded wood (SEW) and monitored periodically for disappearance. Soil column leaching studies and the USEPA standard toxicity characteristic leaching procedure were used to assess the potential environmental hazard of land application of spent lignocellulosic matrix materials. Pesticide bioavailability was determined with plant or animal bioassay indicators. In peat‐filled bioreactors containing atrazine at loading rates of 1.4, 2.0, and 7.2 g kg−1 (dry wt. basis), solvent extractable atrazine decreased to less than 0.2% of starting levels within 480 d. For the SEW‐filled bioreactors containing atrazine at a loading rate of 2.0 g kg−1, solvent extractability decreased to 20% of starting levels within 320 d. Extractable carbofuran in peat‐filled (initial loading rates 0.7, 1.8, and 5.0 g kg−1) and SEW‐filled (initial loading rate 5.0 g kg−1) bioreactors decreased to less than 0.05% of starting levels within 480 d. Both leachability and bioavailability of pesticides were dramatically reduced during the process of SSF. The amount of leachable pesticide remaining in peat sorbent following bioreactor start‐up was dependent on the initial pesticide loading rate and the length of bioreactor operation time. The use of SSF techniques to dispose of pesticide waste may prove a viable alternative to other disposal methods that are either too expensive or technically sophisticated.