Search

Diverting organic waste from landfills provides significant emissions benefits in addition to preserving landfill capacity and creating value-added energy and compost products. Dry anaerobic digestion (AD) is particularly attractive for managing the organic fraction of municipal solid waste because of its high-solids composition and minimal water requirements. This study utilizes empirical data from operational facilities in California in order to explore the key drivers of dry AD facility profitability, impacts of market forces, and the efficacy of policy incentives. The study finds that dry AD facilities can achieve meaningful economies of scale with organic waste intake amounts larger than 75,000 tonnes per year. Materials handling costs, including the disposal of inorganic residuals from contaminated waste streams and post-digester mass (digestate) management, are both the largest and the most uncertain facility costs. Facilities that utilize the biogas for vehicle fueling and earn associated fuel credits collect revenues that are 4-6x greater than those of facilities generating and selling electricity and 10-12x greater than facilities selling natural gas at market prices. The results suggest important facility design elements and enabling policies to support an increased scale of organic waste handling infrastructure.

Separate household food waste collection for anaerobic digestion is one method used in the sustainable management of biodegradable municipal solid waste (MSW). Recycling of food waste contributes to the UK’s reuse, recycling and composting targets and can help local authorities boost plateauing rates whilst encouraging landfill diversion. This study explored the reasons for differences in the provision of food waste collections, using two comparable local authorities, one with a collection in Wales (Cardiff), and the other absent of such service in England (Southampton). A PESTLE analysis investigated the political, economic, social, technological, legal and environmental impacts of separate food waste collections. The greenhouse gas impacts of the collection and treatment systems of MSW in both cities were estimated for 2012/13. Results showed significant policy and legislative differences between devolved governments, that separate food waste collections can save local authorities significant sums of money and substantially reduce greenhouse gas impacts. A survey of one hundred respondents in each city aimed to understand attitudes and behaviours towards recycling, food waste segregation, cooking and purchasing habits. The number of frequent recyclers and levels of satisfaction were higher in the authority which provided a separate food waste collection. In the area which lacked a separate collection service, over three-quarters of respondents would participate in such a scheme if it were available.

When assessing the environmental and human health impact of a municipal food waste (FW) management system waste managers typically rely on the principles of the waste hierarchy; using metrics such as the mass or rate of waste that is 'prepared for recycling,' 'recovered for energy,' or 'sent to landfill.' These metrics measure the collection and sorting efficiency of a waste system but are incapable of determining the efficiency of a system to turn waste into a valuable resource. In this study a life cycle approach was employed using a system boundary that includes the entire waste service provision from collection to safe end-use or disposal. A life cycle inventory of seven waste management systems was calculated, including the first service wide inventory of FW management through kitchen in-sink disposal (food waste disposer). Results describe the mass, energy and water balance of each system along with key emissions profile. It was demonstrated that the energy balance can differ significantly from its' energy generation, exemplified by mechanical biological treatment, which was the best system for generating energy from waste but only 5th best for net-energy generation. Furthermore, the energy balance of kitchen in-sink disposal was shown to be reduced because 31% of volatile solids were lost in pre-treatment. The study also confirmed that higher FW landfill diversion rates were critical for reducing many harmful emissions to air and water. Although, mass-balance analysis showed that the alternative end-use of the FW material may still contain high impact pollutants.