Challenges of Load Variation on Anaerobic Digestion of Organic Waste on a Full Scale: An Applied Study

Purpose The work evaluated the functioning and yields of a full-scale anaerobic digestion plant, installed on a university campus, with changes in organic loads and food suspension due to the inconstant waste generation. Methods The substrates were food waste, generated in the university restaurant and cafeteria of the university hospital, and swine manure, with fluctuations in the OLR. Thus, a CSTR reactor with a useful volume of 40 m was operated for 278 days in a semi-continuous manner with mechanical agitation, mesophilic temperature (36 ± 2 °C), and 40 days of HRT. Results The OLR ranged from 0.14 to 2.50 kgVS m d, resulting in the highest specific average methane yield of 0.62 m CH kgVS in HRT 1. The methane content in the biogas ranged from 54.65% at start-up and 66.60% at HRT 4. Overall conversion rates were 67.42% for VS and 63.74% for COD. The load variation did not interfere with the microbiological community, which proved to be adapted to degrade the substrates, ensuring favorable conditions to produce methane. Conclusion The implementation and system conditions were considered positive, aiming for the production of methane for the generation of clean energy that can be consumed on the university campus.