Evaluation of biogas generation from turkey waste

This project investigates local industrial biomass streams as feedstocks for the generation of low-cost sustainable energy for The University of Iowa. Methane gas produced during anaerobic digestion would fuel an engine to generate electricity at the University of Iowa Research Park (Oakdale Campus). A current local industry identified for this project is West Liberty Foods (WLF), a turkey processing facility located in West Liberty, Iowa, USA. WLF generates about 6,000 gal/day of blood, 40,000 lb/day of offal (guts), 6,000 lb/day of sludge (process waste water) and 2-4 truckloads/day of feathers as waste streams. To investigate biochemical methane potential, mixed streams and individual streams of WLF were processed anaerobically and incubated at 35°C. Mixed streams contained blood, offal, and sludge, and individual streams contained offal and sludge. Mixed streams and individual streams generated methane gas. The methane production from mixed streams was achieved on the 11th day of processing, and it was achieved on the 9th day from individual streams. Sludge was the only stream that did not require the addition of acetate for the production of methane gas. Methane production was analyzed using gas chromatography. Methane production was achieved without addition of microbial seed cultures. Cumulative methane and energy produced by the 36th day of processing 6 grams of offal with the addition of acetate are 110 +/- 50 mmol/lb and 0.09 +/- 0.04 kJ/lb respectively, and without the addition of acetate are 62 +/- 2 mmol/lb and 0.054 +/- 0.002 kJ/lb respectively. Cumulative methane and energy produced by the 36 th day of processing 6 grams of sludge with the addition of acetate are 200 +/- 20 mmol/lb and 0.18 +/- 0.02 kJ/lb respectively, and without the addition of acetate are 220 +/- 60 mmol/lb and 0.19 +/- 0.04 kJ/lb respectively. Each average was calculated from three data points with their errors. Reported values are calculated at 95% confidence intervals. The Oakdale Campus is estimating to produce 5.5 MW energy from renewable sources of energy. The methane production capacity from processing turkey waste based on COD analysis was approximately 1% of the renewable energy target. However, the system is still producing methane gas and the process is not complete yet nor has it been optimized. Benchmarking methane productivity through improved quantitative measures should continue to establish the utility of the process.