Abstract
Abstract Carbon emissions from the aviation industry are a significant concern and the adoption of sustainable aviation fuel has the potential of mitigating the environmental impacts. Hydrothermal liquefaction (HTL) has great potential to produce sustainable aviation fuel employing organic waste feedstock but requires further development to reduces costs and the environmental impact. This study focuses on examining the feasibility of an integrated HTL plant in the UK whilst investigating the potential to improve the energy efficiency of the process through heat integration and resource recovery from waste streams. The methodology adopted includes modelling an integrated HTL plant with a feed throughput of 10 t h−1 using Aspen Plus simulation approach. Techno-economic, regional resource and carbon footprint assessment are conducted on three different HTL configurations, i.e. a base case without energy and resource recovery; an HTL with heat integration; and an HTL with energy and resource recovery. Three different feedstocks (algae, food waste and sewage sludge) are investigated with sewage sludge feedstock found to have the lowest minimum fuel selling price of 0.50 £ l−1. Heat integration results in a 96.4% and 77.8% decrease in heating and cooling utilities and the economic assessment indicates that heat integration and resource recovery can reduce the minimum fuel selling price by 10.5% compared to the base case. The regional resource assessment reveals that 22.8% of UK jet fuel demand can be met with the technology. The carbon footprint assessment demonstrates that with maximum production, the technology can result in a 18.3% reduction of CO2 emissions relative to current aviation emissions. This study signifies that the integrated HTL process could play a pivotal role in mitigating carbon emissions in the aviation industry.
Highlights
Aviation provides a rapid global transportation network and is pivotal for many industries from trade to tourism
For the use of sewage sludge, additional dewatering of the feedstock is required on site to eliminate challenges in transporting wet sludge to external facilities, and the total capital costs are estimated to be to 12.7 million £
This study investigated how an integrated hydrothermal liquefaction (HTL) plant incorporating heat integration and resource recovery from waste could potentially improve the economic performance and reduce greenhouse gas (GHG) emissions for jet fuel production in the UK
Summary
Aviation provides a rapid global transportation network and is pivotal for many industries from trade to tourism. The industry currently transports approximately 3.8 billion passengers annually and 35% of world trade calculated by the value of goods shipped (ATAG, 2017). There are currently a number of ASTM certified technologies that can be adopted to produce SAF, including Fischer-Tropsch, Hydroprocessed esters and fatty acids and alcohol-to-jet (IRENA, 2017). There are approximately four emerging production pathways awaiting ASTM certification including pyrolysis, hydrothermal liquefaction (HTL), aqueous phase reforming, and aerobic fermentation of sugars (IRENA, 2017). HTL is chosen as the focus of this study, as an emerging production pathway that has shown promising potential to produce SAF using wet biomass such as municipal solid waste and sewage sludge, so reducing the need for dewatering (Katakojwala et al, 2020). The major advantage of HTL is its versatility to process a wide range of feedstock whilst producing a bio-oil intermediate with low oxygen and high energy content (37 MJ kgÀ1) (Snowden-Swan et al, 2017)
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