Anaerobic digestion of secondary residuals from an anaerobic bioreactor at a brewery to enhance bioenergy generation
- 434 Downloads
Many beer breweries use high-rate anaerobic digestion (AD) systems to treat their soluble high-strength wastewater. Biogas from these AD systems is used to offset nonrenewable energy utilization in the brewery. With increasing nonrenewable energy costs, interest has mounted to also digest secondary residuals from the high-rate digester effluent, which consists of yeast cells, bacteria, methanogens, and small (hemi)cellulosic particles. Mesophilic (37 °C) and thermophilic (55 °C) lab-scale, low-rate continuously-stirred anaerobic digestion (CSAD) bioreactors were operated for 258 days by feeding secondary residuals at a volatile solids (VS) concentration of ∼40 g l−1. At a hydraulic retention time (HRT) of 15 days and a VS loading rate of 2.7 g VS l−1 day−1, the mesophilic bioreactor showed an average specific volumetric biogas production rate of 0.88 l CH4 l−1 day−1 and an effluent VS concentration of 22.2 g VS l−1 (43.0% VS removal efficiency) while the thermophilic bioreactor displayed similar performances. The overall methane yield for both systems was 0.21 l CH4 g−1 VS fed and 0.47–0.48 l CH4 g−1 VS removed. A primary limitation of thermophilic digestion of this protein-rich waste is the inhibition of methanogens due to higher nondissociated (free) ammonia (NH3) concentrations under similar total ammonium (NH4+) concentrations at equilibrium. Since thermophilic AD did not result in advantageous methane production rates or yields, mesophilic AD was, therefore, superior in treating secondary residuals from high-rate AD effluent. An additional digester to convert secondary residuals to methane may increase the total biogas generation at the brewery by 8% compared to just conventional high-rate digestion of brewery wastewater alone.
KeywordsAnaerobic digestion Methane yield Secondary residuals Continuously-stirred anaerobic digestion Bioenergy
We would like to acknowledge the financial support of Anheuser-Busch Inc., St. Louis, MO and thank Thea Cummings for her support in feeding the bioreactors and Jelte Lanting (Biothane Corporation, Camden, NJ) for consulting on the operating conditions.
- 6.Clesceri LS, Greenberg AE, Eaton AD (1998) Standard methods for the examination of water and wastewater. APHA, AWWA, WEF, WashingtonGoogle Scholar
- 9.El-Hadj TB, Dosta J, Mata-Alvarez J (2007) Start-up and HRT influence in thermophilic and mesophilic anaerobic digesters seeded with waste activated sludge. Chem Biochem Eng Q 21:145–150Google Scholar
- 11.Fogler HS (1999) Elements of chemical reaction engineering. Prentice Hall Inc, Upper Saddle River, NJGoogle Scholar
- 13.Gujer W, Zehnder AJB (1983) Conversion processes in anaerobic digestion. Water Sci Technol 15:127–167Google Scholar
- 15.Hoffmann R, Garcia ML, Veskivar M, Karim K, Al-Dahhan MH, Angenent LT (2007) Effect of shear on performance and microbial ecology of completely-stirred anaerobic digesters treating animal manure. Biotechnol Bioeng, vol. 19 (Epub ahead of print)Google Scholar
- 18.Kleerebezem R, Macarie H (2003) Treating industrial wastewater: anaerobic digestion comes of age. Chem Eng 110:56–64Google Scholar
- 23.Massart N, Bates R, Corning B, Neun G (2006) When it bubbles over. Water Environ Technol 18:50–55Google Scholar
- 28.Soto M, Mendez R, Lema JM (1992) Characterization and comparison of biomass from mesophilic and thermophilic fixed-bed anaerobic digesters. Water Sci Technol 25:203–212Google Scholar
- 29.Stafford DA, Hawkes DL, Horton R (1980) Methane production from waste organic matter. CRC Press, Boca RatonGoogle Scholar
- 33.Trnovec W, Britz TJ (1998) Influence of organic loading rate and hydraulic retention time on the efficiency of a UASB bioreactor treating a canning factory effluent. Water SA 24:1147–1152Google Scholar