Generation of biogas and thermal energy at the Bolo das Oliveiras Agroindustry, Pombal, Paraíba, Brazil

Abstract

This study aimed to assess the potential for generation of thermal energy from biogas produced by a rural biodigester in the Bolo das Oliveiras Agroindustry, Pombal/PB, Brazil. The biodigester was fed every two days with 0.30 m3 of biomass (mixture of water and bovine manure), retention time of 45 days. Affluent and effluent samples were collected every 15 days for 75 days. The affluent had a higher (p < 0.05) solids contents than the effluent. The highest dissolved oxygen concentration (6.67 mg L−1) was observed in the affluent. The effluent had lower (p < 0.05) total alkalinity than the affluent at all sampling times. CH4 values were higher than CO2 values throughout the experiment. Biogas also contained trace proportions of H2S and NH3 (2/3 and 1/3 ppMV, respectively). CH4 emissions were estimated at 10.58 m3 day−1. CH4 was the major constituent of biogas, as indicated by flame combustion behavior. Generation of biogas and thermal energy at the Bolo das Oliveiras Agroindustry may be economically feasible, providing a minimum monthly savings of R$ 1,582.00.