Abstract
Co-digestion of sewage sludge with food waste is a beneficial pathway for sewage plants to enhance their biogas yield. This paper employs hybrid programming with system dynamics simulation to optimize such a co-digestion system from the perspective of demand-oriented biogas supply chain, thus to improve the efficiency of the biogas utilization. The optimum operational parameters of the co-digestion system are derived from the simulation model. It is demonstrated that the demand-oriented biogas supply mechanism can be effectively driven under market-oriented incentive policy. For better compensation of the external cost to assist the operations of the co-digestion supply chain, it is suggested that the substrate collection and transportation subsidy should be combined with the renewables portfolio standard to be implemented as the optimum incentives. The limitations of the study are discussed to lay the foundation for future improvements.
Highlights
With the increase of newly built sewage plants, large amounts of excess sludge have been produced (Prabhu and Mutnuri, 2016)
This paper employs a hybrid programming with system dynamics simulation to investigate the economic feasibility of the demand-oriented biogas supply’ (DO) by co-digestion of sewage sludge and food waste from the supply chain perspective
The optimal electricity production timetable under the DO mechanism is solved by the mixed integer linear programming (MILP) model; on this basis, the system dynamics model is established for simulating the operation of the co-digestion system
Summary
With the increase of newly built sewage plants, large amounts of excess sludge have been produced (Prabhu and Mutnuri, 2016). Some researchers have tried the codigestion of municipal food waste and sewage sludge to increase the organic load rate and stability of the AD system, enhancing the biogas production rate to improve the economic benefits from power generation (Mehariya et al, 2018; Nghiem et al, 2017). The sewage plant can make full use of the digester’s capacity through the co-digestion to treat the self-produced excess sludge and municipal food waste simultaneously, so as to achieve a win–win–win of economic, environmental and social benefits (Glivin et al, 2020; Park et al, 2016). By regulating the biogas utilization scheme from the expanded biogas storage tank, or adjusting the AD reaction process, the biogas can be supplied for electricity generation in real time and in certain amounts in response to the daily electricity demand (Hahn et al, 2014b; Lauer and Thrän, 2018)
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