Enhancing resource effectiveness: An environmental and economic analysis of thermal and biological treatment of discarded material

Abstract

Waste-to-energy technology addresses several societal concerns. It protects human health and the environment, treats waste and recovers material. It mitigates climate change by reducing the carbon intensity of energy generation whilst increasing energy security. Often, these multiple services are not sufficiently recognised. This thesis informs energy and waste management policy by characterising the benefits that can justify appropriate support to address the currently limited awareness. To investigate the greenhouse gas emissions, economic viability and energy efficiency potential, a model was created using performance metrics and, where possible, real plant data. Gasification, as a novel technology, was compared with incineration in combined thermal treatment scenarios. Anaerobic digestion was analysed independently. Gasification can achieve higher energy efficiency with lower carbon intensity and higher flexibility of location. At low levels of support gasification is less attractive than incineration; but more competitive with increased support similar to current levels. Without incentives for its electricity output, relying only on the price for carbon and high landfill tax, small-scale gasification would be ruled out. Commercial viability of anaerobic digestion is significantly influenced by support for its heat and electricity outputs. Particularly small-scale plants would not be viable without support or appropriate valuation of the multiple objectives they fulfil. Established waste management companies are necessary partners for new technology providers to access finance. Industrial interest in new technologies, however, is driven by their qualifying for support. Analysis shows that an efficiency-linked escalating reward could incentivise development and use of gasification (with combined-cycle gas turbine) instead of deployment of less risky but less efficient configurations. An extended assessment framework was developed to recognise the contribution to resource effectiveness of waste-to-energy technology by characterising energy security (in size of the contribution and through abundant, negative-cost national feedstock); the contribution to renewable energy targets; the higher energy system resilience (through increased predictability, variety, disparity and balance); and lower carbon intensity of the economy.