The 'system expansion' strategy is particularly useful for LCA of a system with multiple functions. The CCU system achieves multiple functions, i.e. the co-productions of several fuels and the generation of low-carbon electricity. For a proper comparison, the 'system expansion' strategy expands a reference process to include all the functions as the original process. As shown in Figure , the reference system can generate the electricity (no capture technology) and fuels by conventional process. Meanwhile, the amount of electricity generation and the production of fuels are equivalent in the two systems for a fair comparison.