Techno-economic evaluation of integrating torrefaction with anaerobic digestion

Abstract In recent days, the interest on torrefactionis increasing owing to its ability to improve biomass properties to a level of competing with coal. However, its techno-economic feasibility still need to be optimized. Integrating torrefactionwith other thermochemical and biochemical processes could be a feasible option to improve the performance of the torrefactionprocess. In that regard, this study evaluates the techno-economic feasibility of integrating the torrefactionwith anaerobic digestion (AD). In addition, new process configurations were studied to identify the possible heat energy recoveryoptions. Technical feasibility was tested through mass and energy balance at each process unit. The economic indicatorssuch as net present value(€), minimum selling price and internal rateon return(%) were used to evaluate the economic performance. At 10 t/h of torrefied biomass pellets production capacity, the estimated bio-methane production from AD was 369 m 3 /h. The economic evaluation shows that the minimum selling price of the torrefied biomass to reach the breakeven could be reduced from 199 €/t for standalone torrefactionto 185 €/t in case of torrefactionintegrated with AD. The sensitivity analysis shows that feedstock and total capital investment were the most sensitive input parameters. This study shows that integrating the torrefactionwith AD has better technical and economic feasibility than standalone torrefaction.