Towards sustainable methanol from industrial CO2 sources

Mitigation of carbon dioxide emissions from industrial facilities has received less attention than the energy sector in the path towards decarbonisation up to now. Therefore, this chapter presents potential measures to reduce CO2 emissions through the conversion of CO2 from industrial sources into methanol in order to achieve the targets set by the European Commission. Methanol is easy to synthesise from CO2 and hydrogen and a stable liquid fuel at ambient conditions, which makes it an ideal candidate for long-term storage of electricity from variable renewable sources. If methanol is stored, it could be used to generate electricity when necessary or as transport fuel due to its high octane rating. While Europe’s contribution in the worldwide production is rather modest, Northeast Asia is the largest methanol consumer. In this work, an integrated system is proposed to re-use CO2 emitted from an ammonia plant is converted into methanol. An Aspen Plus model was developed for the three sub-processes; i) CO2 capture of an ammonia plant, that already captures CO2 as part of the hydrogen production stage, ii) water/CO2 co-electrolysis, and iii) methanol synthesis and purification. Heat integration strategies are carried out to improve the process efficiency of the integrated system. This work also discusses current and potential use of CO2 emitted from other industrial sources such as steel mills, ethanol plants and power industry. The future of CO2 conversion into methanol greatly depends on its economics compared to traditional methanol production from fossil fuels. A review of the costs for the CO2-to-methanol process is presented, where it is recognised that projects require a carbon tax to make them financially attractive. The installation of CO2-to-methanol plants could fully replace current importations in Europe, for which only about 11 plants producing each 440 t/year would be needed. A key for the growth of CO2-to-methanol facilities is that the energy required is supplied by renewable energy to truly contribute to the industry decarbonisation. As such, even higher potential is anticipated if methanol is used as a sustainable energy carrier to fulfil the so-called methanol economy.