Whole-Systems CO2 Value Chain Modelling: A Closer Look at the Pathways through Syngas

There are vast sources of renewable energy in Great Britain but only a small fraction is being used because of the inability of the existing energy infrastructure to deal with the intermittency of supply. An alternative to storing the excess renewable energy in physical devices (e.g. batteries, pumped hydro) is to use the excess energy to power processes that convert CO2 to valuable products. As CCS technologies start to be adopted by energy producers and become more widespread, a large quantity of CO2 will be captured and stored underground. Instead of treating this CO2 as a waste gas, some of it can be used as a raw material to produce alternative fuels and valuable chemicals using excess renewable energy generated when the demands for energy are low. There are many different pathways from CO2 + “excess” renewable energy to valuable products. The aim of this work is to develop a comprehensive MILP model for CO2 value chains that will include all of the pathways from primary resources to end-products (e.g. fuels and chemicals) considering the different technologies for conversion, storage and transport of resources. In this conference, we will present the results of the modelling work that we conducted for syngas value chains, which are important subsets of the entire CO2 value chain landscape. Different technologies for the production of syngas (including fossil fuel-based technologies for comparison) and its conversion to different products are considered. The former includes natural gas reforming, biomass gasification and catalytic reverse water gas shift reaction between captured CO2 and H2 produced by electrolysis using excess renewable electricity. The latter includes Fischer Tropsch and alcohol syntheses to produce C2-C3 olefins, >C1 hydrocarbons and >C1 alcohols, as well as different energy conversion technologies that can utilise syngas to meet different demands for energy services. Different storage technologies (e.g. pressurised vessels, salt caverns) and transport infrastructures (e.g. road transport of biomass, syngas pipelines) are also considered in the model. The model determines how to make best use of primary resources by optimising the combinations of technologies to use, where to locate them, when to invest in them, how to transport and store resources and so on. The model accounts for operational issues at different time scales, e.g. hourly time scales to capture intermittency of renewables and dynamics of energy storage, seasons to capture availability of biomass. Spatial dependencies are also modelled by representing Great Britain into different zones based on the National Grid’s study zones.