Biogas Production with Beef Cattle Manure and Wastewater from Hydraulic Fracturing

Abstract

HighlightsHydraulic fracking wastewater is evaluated as a possible alternative to freshwater in combination with beef cattle manure for bio-methane generation by anaerobic digestion (AD).Optimum conditions for AD with fracking wastewater remain unknown, but differ from AD with freshwater.Contrary to AD with freshwater, biogas production with fracking wastewater increased with lower MC.Abstract. Wastewater from hydraulic fracturing (HF) and manure from beef cattle production are two of the largest waste streams in the Texas Panhandle. The objective of this study was to evaluate the potential of generating biogas, a renewable natural gas, from the combination of HF wastewater and beef manure through anaerobic digestion (AD) at varying moisture contents. In a laboratory study, substrate combinations of manure mixed with produced and flowback water (PFW), well water (WW), and a 50/50 mixture of PFW and WW were evaluated at four moisture contents (MC; 65%, 70%, 80%, and 90%). Beef manure was harvested from the West Texas A&M University research feedlot. The PFW was collected from a HF operation in the Texas Panhandle. The combinations of manure and WW at 90% MC yielded the greatest amount of biogas and methane (CH4). The greatest amount of biogas and CH4 with the combination of manure and PFW was produced at 65% MC. This combination produced 57% less biogas than the optimum CH4-producing WW treatment. Diluting PFW with WW produced amounts of CH4 comparable to WW at 80% MC. While there is potential to generate biogas and methane with PFW and manure, more research is needed to isolate the CH4-inhibiting constituents in PFW. Keywords: Anaerobic digestion, Manure, Methane, Produced and flowback water.