Technoeconomic feasibility of integrated organics processing facilities with anaerobic digestion and composting for regional Australia

Technoeconomic feasibility of integrated organics processing facilities with anaerobic digestion and composting for regional Australia

Internationally, municipal food and garden organics have long been diverted from landfill to beneficial use to harness their inherent nutrient and energy value. In contrast, diversion of food waste from landfill has only recently become a focus in Australia. To facilitate the development of a sustainable municipal organic processing sector in Australia, this research aimed to assess feasibility and benefits of integrated composting and anaerobic digestion (AD) processing facilities. The study reviewed key chemical and physical characteristics of food organics and garden organics (FOGO) as a prospective feedstock. Several foreseeable integrated facility scenarios were formulated and critically evaluated with reference to learnings from five inspected operational European facilities. Basic process flows were developed to determine throughputs and saleable products and these were compared with capital and operating costs of the integrated facilities.
Results suggested an integrated approach using complementary processing such as composting and AD has positive returns, but the processing options need to consider external factors to determine which products create the optimum economic returns. Having a high electrical user co-located with the integrated organics processor is a readily achievable arrangement for a municipal authority and the results show that a 40% improvement in financial returns could be expected over the single technology composting facility. A similarly positive result is also obtained for a facility which produces compressed natural gas (CNG) as a fuel but would require a vehicle fleet being available to realise the benefits. A facility which produces biomethane for export has potential for an 85% improvement over a compost facility, but the biomethane must be valued at retail values and will be more difficult to achieve in practice. The inclusion of food waste in the organic feedstock contributed significantly to the energy available in the end products and was a strong driver for the economic viability of an integrated processing facility. This study also provided details of similar integrated facilities in Europe and outlined the benefits of upgraded products such as biomethane and electricity which are valued at near retail prices. The techno-economic decision support framework developed in this study provides guidance on preferred facility types suited to particular external economic factors. Existing composting sites may also benefit from integrating AD when combined FOGO is introduced.

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