ena-STUDY-AARHUS UNIVERSITY, DENMARK-12-09-2018-10:10:39:491-465
Biological power to gas: the ratio of hydrogen uptake rate to biogas production rate determines volatile fatty acid kinetics during hydrogen injection
Low-price, renewable electricity can power the biological conversion of carbon dioxide to methane, called biomethanation, by means of hydrogen injections to a biogas reactor. The injected hydrogen may however affect volatile fatty acids kinetics in the biogas reactor and thereby compromise reactor and biomethanation performance. The organic loading rate and biogas production varies amongst full-scale biogas reactors, but the effect of these differences on reactor performance during biomethanation has not been addressed previously. Biomethanation and specifically volatile fatty acids kinetics were therefore evaluated during hydrogen injections to biogas reactors operated at a range of low to high organic loading rates. The ratio of hydrogen uptake rate to biogas production rate described the degree of acetate accumulation during hydrogen injections. High acetate, but not high hydrogen concentrations inhibited propionate degradation. Concurrently, butyrate levels remained stable during hydrogen injections, reflecting the protection of the hydrogen-sensitive syntrophic acetogenesis by the rapid H2 consumption. Biogas reactors operators can use the ratio of hydrogen consumption to biogas production to increase methane production and control volatile fatty acid concentrations during hydrogen injections.
Low-price, renewable electricity can power the biological conversion of carbon dioxide to methane, called biomethanation, by means of hydrogen injections to a biogas reactor. The injected hydrogen may however affect volatile fatty acids kinetics in the biogas reactor and thereby compromise reactor and biomethanation performance. The organic loading rate and biogas production varies amongst full-scale biogas reactors, but the effect of these differences on reactor performance during biomethanation has not been addressed previously. Biomethanation and specifically volatile fatty acids kinetics were therefore evaluated during hydrogen injections to biogas reactors operated at a range of low to high organic loading rates. The ratio of hydrogen uptake rate to biogas production rate described the degree of acetate accumulation during hydrogen injections. High acetate, but not high hydrogen concentrations inhibited propionate degradation. Concurrently, butyrate levels remained stable during hydrogen injections, reflecting the protection of the hydrogen-sensitive syntrophic acetogenesis by the rapid H2 consumption. Biogas reactors operators can use the ratio of hydrogen consumption to biogas production to increase methane production and control volatile fatty acid concentrations during hydrogen injections.