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Solid waste management is an important environmental and public health challenge, particularly in the developing world. This chapter highlights the importance of organic waste recycling using insects, which can subsequently be utilized as an alternative animal feed or even human food ingredient. In addition, biowaste conversion by exploiting insects is found to be environmentally more beneficial (reduced greenhouse gas emissions) than traditional waste handling, such as composting. Thus, organic waste valorization via insects could be a sustainable measure of biowaste treatment as it generates novel nutrient sources while posing a minimum threat to the environment. Characterizing biowaste as an insect rearing substrate, examining the potential role of the insect gut microbiota on waste degradability and insect biomass and quality, and identifying environmentally friendly residue handling approaches are some of the critical aspects for insect-based biowaste recycling in the future.

Biogas upgrading by employment of bioelectrochemical systems (BESs) is an emerging approach for electricity-based production of biomethane. Recent advances within the field have successfully demonstrated BES for biogas upgrading at laboratory scale under different configurations and operating conditions: in situ, ex situ, batch mode, and continuous mode. This chapter summarizes the development and status of bioelectrochemical biogas upgrading, and includes examples of multifunctional systems combining biogas upgrading with resource recovery. Insights are given into proposed electron transfer mechanisms and reported BES designs for CO2 reduction to methane. BES technology for biogas upgrading has primarily been developed to lab-scale and still has to be further developed to evaluate the current economic perspectives of the technology compared to conventional biogas-upgrading technologies.

Anaerobic digestion (AD) has been widely applied bioprocess to produce the biogas for fuels from organic waste degradation. AD has been integrated with other processes for increasing the digestion efficiency and waste valorization. The integration of AD with other bioprocess optimizes the production of targeted product and reduces the waste. Recently, microbial electrosynthesis (MES) was coupled with AD for the biomethane production, chemical synthesis and resource recovery. MES coupling to AD also gives an opportunity for value-added chemical generation and hence provides additional economic gains of integrated system. In MES, the remaining carbon dioxide (CO2) in biogas is reduced to methane by methanogens utilizing in situ produced hydrogen at cathode, thereby enriching methane content. Furthermore, electroactive microbes could directly accept the electron from cathode to reduce the CO2 to methane and chemicals. Therefore, CO2 fraction in the biogas could be utilized for the further chemical synthesis such as acetate, butyrate. In this chapter, advances on AD technology and MES coupling with AD are thoroughly discussed for the production of fuels and chemicals. The outputs of recent laboratory scale experiments are summarized and discussed. Furthermore, mechanism of CO2 reduction is elaborated with methane and chemical production.

Agriculture-based industries generate significant amounts and varieties of agro-industrial wastes (AIW). AIW, if not treated properly, may cause environmental pollution and pose a harmful effect on human and animal health. Although AIW consist of organic compounds that can pose a risk to the environment, however, if used in the right way can potentially produce bioenergy, biofertilizer, and biofuels. Energy generation using agro-wastes not only fulfill the energy demand locally but also contribute to a significant reduction in greenhouse gas emissions. Bioenergy a possible substitute for fossil-fuels can be generated from AIW residues like rice straw, sweet potato, sugarcane bagasse, sawdust, etc. Nutrient-rich and bioactive compounds obtained from AIW can be recycled as raw materials in the agro-based industries, which can reduce the total production costs. Moreover, agricultural wastes, such as animal manures, agricultural effluents, biosolids, etc., can be used as organic fertilizers. This will help to mitigate the scarcity of organic fertilizers and increase the crop yield and productivity. However, the sorption of heavy metals in fertilizers needs to be considered. AIW can be converted to biodegradable plastic or can be used as a feed-in aquaculture industry. Overall, AIW seems to be a potent source of alternative energy and organic fertilizers.