Abstract

Globally, livestock and poultry production leads to total emissions of 7.1 Gigatonnes of Carbon-dioxide (CO2)-equivalent per year, representing 14.5% of all anthropogenic greenhouse gas emissions. Anaerobic digestion (AD) is a sustainable approach to generate methane (CH4) from manure, but the risk of ammonia inhibition and high-solids can limit the AD process. A two-stage (liquid–solid) batch-mode AD biotechnology at a low-temperature (20±1 °C), using an adapted liquid inoculum, was developed to address the limiting factors. This study deals with chicken manure (CM) and dairy cow manure (DM) as feedstock. Furthermore, liquid inoculum recirculation-percolation mode was adopted to replace mechanical mixing. The findings from physio-chemical and biogas analysis showcased the sustainability of this novel biotechnology technique, yielding impressive results at 20±1 °C. Firstly, CM liquid inoculum was adapted to high-ammonia concentrations. Secondly, mono-digestion of CM (TKN: 23-33g/L; TS: 68-72%) was conducted in the aforementioned AD technology. Then, a start-up study on co-digestion of CM+DM (TKN: 13.6 g/L; TS: 48-51%) was conducted for 190 days using same technology. Moreover, to investigate AD process stability, physio-chemical parameters were monitored. The objective of this study was to demonstrate the operational feasibility of the proposed AD biotechnology. Results showed that, although a better SMY (0.52 ± 0.13 L CH4g−1VSfed) was obtained for mono-digestion of CM, co-digesting CM + DM showed a better methane quality and generated comparatively lower FAN. Finally, techno-economic assessment of the aforesaid AD technology, processing 1tonne-CM/day showed that the AD plant obtained revenue after 14 years from the commencement of the project.