The U.S. Department of Energy has assessed potential research and development activities that could improve the economic viability of municipal solid waste-to-energy facilities.
DOE recognizes that sorted municipal solid waste (MSW) and related feedstocks constitute a present disposal problem for municipalities and similar entities. Improving waste-to-energy conversion in existing facilities and developing technologies for next generation facilities is important to localities across the country as they explore more cost-effective solutions to waste disposal.
MSW starts out as a complex mixture of food waste, glass, metals, yard trimmings, woody waste materials, non-recyclable paper and plastic, construction and demolition waste, rags, and sludge from wastewater treatment. MSW presents numerous challenges when used as a feedstock for energy production: it has low energy content, high moisture, heterogeneous composition, and despite its abundance—the average American produces 4.4 pounds per day—it is highly distributed across the United States making it difficult for traditional approaches to reach economies of scale in many parts of the country.
Incineration and anaerobic digestion represent two existing types of MSW waste-to-energy facilities in the United States. Both require prior separation of recyclables to achieve optimal resource recovery and can produce electricity, heat, or both. However, high operating costs and high-level of competition from alternative sources make the production of heat and power from MSW economically challenging. DOE identified several R&D opportunities to improve the economic viability of existing MSW waste-to-energy facilities:
- Develop waste preprocessing and handling strategies to reduce feedstock variability of MSW streams. This allows for the most economical optimization of specific streams toward recycling, heat, power, fuels, and products. Research opportunities include characterization methods for high-precision sorting, development of quality control parameters, and pretreatment processes to remove contaminants.
- Reduce operating costs and increase revenues in existing incinerator facilities. These opportunities include advanced emissions control strategies to lower costs associated with environmental compliance,development of novel corrosion-resistant materials to reduce maintenance costs, and advanced separations to recover valuable materials from ash.
- Enhance economic viability of existing anaerobic digestion facilities. These opportunities include research of co-digestion strategies to enhance methane production and extend steady-state operation, low cost strategies for biogas cleanup to result in pipeline quality natural gas, novel thermocatalytic processes for the conversion of biogas and landfill gas to fuels and high-value co-products, and advanced reactor design and optimization of organisms to enhance biological conversion of gases to fuels and co-products.
DOE also identified several R&D strategies that might inform next generation waste-to-energy facilities in the United States. These technologies, while at an earlier stage of technology readiness, may provide cost-competitive alternatives that are better suited to the heterogeneous composition and distributed availability of MSW feedstocks. Many of these approaches enable the waste-to-energy facility to produce biofuels and co-products, which may provide enhanced revenues compared with existing facilities focused only on heat and power. DOE identified several R&D opportunities for cost-competitive waste-to-energy facilities:
- Apply gasification technologies to sorted MSW to produce a syngas intermediate. This includes developing biological conversion processes, which includes genetic engineering of more robust organisms to reduce separations costs, and advanced reactor designs to enable continuous operation. Thermochemical conversion research opportunities include the development of advanced catalysts with greater longevity and tolerance to impurities, as well as high-temperature, high-pressure gas clean-up strategies.
- Lower capital costs of next generation anaerobic digestion systems that make high-value products.These opportunities include developing anaerobic membrane bioreactors and transforming the chemistry of anaerobic digestion to produce short-chain organic acid intermediates that can be used to make higher-value fuels and commodity chemicals like acetone and naphtha.
- Conversion of sorted-MSW to biocrude and derivative fuels. These opportunities include modular hydrothermal liquefaction reactor designs to simultaneously process multiple waste streams and developing novel catalysis for sorted-MSW pyrolysis. Research opportunities also exist for the co-processing of biocrudes in existing petroleum refineries.
- Enhance techno-economic viability of processes for currently unrecycled plastics. More efficient transformation of existing polymers into high-value products could reduce the amount of plastics that go to landfills.
Production of biofuels and co-produced bioproducts from MSW feedstocks is at a much earlier stage of technological development than biopower. However, existing basic and applied research on producing biofuels and co-produced bioproducts from cellulosic materials, algae and other feedstocks can be leveraged to make MSW processes more cost effective.
The entire 29-page report with additional information and resources is now available for download.