Alternative sources of fossil carbon : Ex-ante assessment of novel technologies using waste as a source

Abstract

Industrial production is driven by society’s demand of fuels, chemicals and materials, which has resulted in unsustainable levels of consumption and emissions. Fossil fuels are still the most common sources of carbon used in production processes. Besides long-term availability issues of fossil fuels, the chemical, petrochemical and road transport sectors contributed to circa 20% of the global greenhouse gas (GHG) emissions in 2012. Therefore, identifying alternative carbon resources can be crucial to address these concerns derived from the large-scale use of fossil fuels. This thesis investigates the use of industrial waste streams (including industrial wastewater and CO2 emitted in industrial processes) as alternative resources for the production of chemicals and fuels. Through waste valorisation, waste streams are converted into valuable products to provide an additional service. There is a need to improve our current understanding on to what extent waste-to-product approaches can contribute to reduce fossil feedstock demand and climate change while providing a business case. Thus, the focus of this dissertation is on the investigation of novel waste-to-product technologies at early development stages. In particular, three knowledge gaps are explored: the environmental performance and economic viability of novel waste-to-product technologies; the suitability of early assessments to evaluate the performance of novel waste-to-product technologies; and whether the increase in operational complexity in waste-to-product technologies pays-off. Careful assessments of different novel waste-to-product technologies and configurations, quantifying costs and environmental impacts prior to commercial-scale implementation can provide insights of their potential and limitations, which are needed to foster the use of waste as an alternative carbon resource. Eventually, this might enable minimising possible downsides and identify the most promising strategies. The overall goal of this thesis is to gain insights into the performance of novel waste-to-product technologies by assessing their environmental and economic performance at the early development stage. To achieve this goal, several case studies were developed. In these case studies, novel waste-to-product technologies with different type of waste used as resource (i.e. wastewater or CO2), diverse final products (i.e. polymers, fine chemicals or transportation fuels) and various levels of configuration complexity (i.e. integrated systems, multi-output processes or cascading in consecutive series) were explored. Comprehensive ex-ante assessments were performed including process design, modelling, ex-ante techno-economic and environmental life-cycle assessments of waste-to-product technologies at their early development stages. Based on the ex-ante technology assessments performed in this thesis, promising opportunities for novel waste-to-product technologies were found. According to the analyses carried out, there is potential in novel waste-to-product technologies to lower fossil feedstock demand and contribute to climate change mitigation. However, environmental and economic gains are not guaranteed in all novel waste-to-product technologies. Therefore, performing ex-ante technology assessments integrating economic and environmental aspects before introducing any novel waste-to-product technology is recommended. Ex-ante assessments allow identifying trade-offs and the most promising alternatives at an early-stage, thereby supporting technology development. Moreover, ex-ante assessments allow effectively implementing measures to minimize future downsides