Bi-level multi-objective programming approach for bioenergy production optimization towards co-digestion of kitchen waste and rice straw

The increase in kitchen waste (KW) generation and irresponsible rice straw (RS) disposal has accentuated problems regarding environmental pollution and resource wasting. Although anaerobic co-digestion has been shown to be a more efficient strategy for bioenergy production than single digestion, there is still significant resistance to its application and diffusion owing to RS collection and many related factors in practice. Therefore, this study proposes a cooperative scheme for the cross-regional problem involving authorities and disposal plants. Subsequently, a bi-level multi-objective programming is developed to express the complexity of conflicts relationship in a multi-hierarchical problem and to achieve economic development, environmental protection and societal satisfaction in the bioenergy optimization process. A practical case study is then investigated to demonstrate the applicability of methodology in co-digestion deployment and resource recovery improvement, whereby scenario analyses are conducted by adjusting associated parameters. The practical application observed that (1) RS purchase was positively correlated with carbon reduction and social satisfaction targets, while excessive pursuit of social satisfaction resulted in a rebounding of carbon emissions; (2) the most popular mix ratios in disposal plants were 4:1 and 3:1, but they favor the latter when RS is readily available in sufficient quantities. Finally, some targeted suggestions are proposed for all stakeholders, which are expected to be a reference for potential users in other areas.