Acid drainage remains the largest source of environmental pollution from mining in the Western states. Semi-passive bioreactors have been successfully used to treat this drainage, but require small-carbon groups such as lactate or methanol as feed for sulfate-reducing bacteria (SRB), and this can be a significant operational cost.

Industrial waste from biodiesel production may provide needed carbons. With the rapidly increasing manufacture of biodiesel fuel, disposal of the waste from fuel manufacturing is becoming an issue. Biodiesel waste (BDW) consists primarily of glycerol and methanol, which are carbons that SRBs readily utilize. A laboratory column project was designed to examine locally-produced BDW, available at little or no cost, as a carbon feed for SRBs. Columns were fed either BDW or reagent-grade glycerol in quantity to reduce 50% of the influent sulfate water provided. Addition of 246 mg/L of reagent-grade glycerol resulted in 50% reduction of the 900 mg/L sulfate provided, while the equivalent of 246 mg/L of glycerol provided as BDW resulted in 55% sulfate reduction. During the initial stages of acclimation, propionic, acetic, formic, and lactic acids were observed. Acid concentrations were reduced over time in the effluent, and organic carbon in the BDW was nearly completely converted to carbon dioxide. Thus there are very good indications that BDW can be used in reactors, representing potential cost-savings to both the mine water treatment and the biodiesel industry.