Techno-economic assessment of digestate management for full-scale continuous dry anaerobic digestion plant

This study investigated techno-economic analysis of digestate management systems for a full-scale continuous dry anaerobic digestion plant treating organic fraction of municipal solid waste (OFMSW). A three-stage dewatering system was considered as the baseline scenario (Sc-1) whereas nitrogen removal unit (Sc-2), the incorporation of membrane bioreactor with nitrification downstream (Sc-3) and direct thermal drying of the digestate (Sc-4) were evaluated. The capital cost for the dewatering system with a cake dryer was $4.2 million. For Sc-2, NH₄-N load could be reduced by 60% and Sc-3 would allow for further reduction in COD and NH₄-N loads with capital cost of $5.2 and $9.1 million, respectively. To achieve an additional reduction in TN load, an investment of $9.8 million was required in Sc-4. Sc-1 had the lowest operation cost, consequently resulting in the highest income of $22.6/ton, whereas Sc-4 had the highest operation cost, resulting in the lowest income of $16.6/ton OFMSW.