Technoeconomic analysis of continuous biodrying process in conjunction with gasification process at pulp and paper mills

In the biorefinery context, thermochemical processes have attracted a significant attention in recent years. Such processes generally consist of three main steps: pretreatment, thermochemical treatment, and post-treatment. In these developing processes, drying and feeding of biomass feedstock remain a significant and costly challenge. The moisture content of biomass feedstock must be decreased to an economic level at pretreatment step otherwise it has to have a detrimental effect on the process efficiency and quality of products. This work addresses the drying of biomass feedstock using novel but practical technology, called biodrying. It is a green technology that offers an opportunity for biomass drying without using an external heat source or fossil fuels, since drying energy is generated through exothermic microbial activity in the biomass that enhances the drying rate. This paper focuses on technoeconomic assessment of continuous biodrying technology integrated to gasification-based biorefinery and investigates the conditions that make such novel technology viable in conjunction with gasification process. Fixed capital investment and operating cost of different biodrying scenarios were estimated as M$4.3–21 and M$0.85/y–3.6/y, respectively, and potential benefits (sludge landfilling cost, energy savings, and carbon credit) from integration of the continuous biodrying system in gasification process implemented in pulp and paper mill were calculated, and ultimately economic performances of the scenarios were assessed. Furthermore, the viable biodrying conditions were specified as 4-day residence time and the major viability risk was found to be bound moisture of biomass.