Assessment of transient hydrogen sulfide peak emissions caused by biogas plant operation

Odor nuisance is a major impediment for public acceptance and wider implementation of biogas plants. Knowledge on composition and dynamics of emissions from these plants is highly needed for development of robust mitigation solutions. In this study, odorant emissions were investigated from two biogas plants of different sizes and capacities. Measurements using proton-transfer-reaction mass spectrometer (PTR-MS) revealed that hydrogen sulfide was the main odorant and constituted 82% and 71% of the odor activity sums (SOAV) at the two studied plants, respectively. Long-term time-resolved measurements furthermore revealed that emissions were highly dynamic with distinct short-term emission peaks. By deploying an array of electrochemical sensors, the main sources of hydrogen sulfide emission were subsequently identified and correlated with operational data to identify the major causes for the highly fluctuating emissions. Addition of biomasses in the form of animal slurry to pre-tanks, were shown to be the major cause of periodic hydrogen sulfide emission within the range of 50–1200 ppm. Such hydrogen sulfide peak emissions could challenge odor abatement from biogas plants and should be taken into account when designing odor abatement technologies for biogas plants.