oa CO2 and renewable electricity as feedstock for fuels production: New pathways using existing technologies

The case for CO2-based fuels Coal and natural gas are still the main fuels for electricity generation. Traditional power plants have many advantages: they are very reliable and can relatively easily be ramped up and down to follow the electricity demand. However, their one disadvantage, their huge CO2 emission, is so big that they are replaced by alternatives. These alternative electricity generation sources, like solar and wind power, do not emit CO2. However, they are intermittent and cannot be used to follow the electricity demand. With the growth of renewable electricity production, the demand for storage of renewable electricity also increase. Oil-based transportation fuels also have many advantages: they can be stored and transported easily and they can be used to propel any transportation device, from mopeds to ocean liners and from passenger cars to airplanes. However, their high CO2 emission makes an alternative necessary. In many cases electric transport is an excellent alternative, but for long-distance heavy transport, shipping and aviation, hydrocarbon-based fuels will still be in demand. All these pressing problems can in principle be solved by using CO2 and renewable electricity to produce hydrocarbon-based transportation fuels. Costs of CO2-based fuels An inventory of CO2 utilization options shows that commercial options do exist and are ready to be deployed at commercial large scale. The major unit operations in the chain from renewable power and CO2 to fuels are PV-panels, CSP-plants, wind turbines, water electrolysis, CO2 capture, syngas conditioning, and Fischer-Tropsch synthesis (see Figure below). Source: Haije & Geerlings dx.doi.org/10.1021/es203160k. Environ. Sci. Technol, 2011 In this paper we present results of a study in which we have compared the costs of the production of certain CO2 based fuels (hydrogen, methanol, methane, and petrol) with the current market prices of the fossil counterparts of these fuels. As expected, the costs of the CO2-based fuels is in general higher, but the gap seems bridgeable. For example, for producing methanol from CO2 from renewable electricity costs 800 to 1500 USD per ton, while methanol from natural gas costs around 500 USD per ton. A major factor determining the costs, are the investments in electrolyzers to convert the renewable power into hydrogen. Especially, at low availabilities of renewable power, the electrolyzer costs drives up the costs of the CO2-based fuels. Development needs Adaptation of existing technology or development of novel technology is necessary to reduce costs and to cope with the intermittent nature of renewables (e.g., rapid ramp-up and ramp-down). The development of improved electrolyzers at lower costs and high efficiency is important. ECN is developing technology for the conversion of CO2 and hydrogen (a separation-enhanced reversed water-gas-shift process), that is especially suited for the CO2-based fuel applications. Conclusion The production of CO2-based fuels using commercially available technologies is possible. These fuels not only re-cycle CO2, but also store renewable electricity and replace fossil-based transportation fuels. The costs are still higher than fossil-based fuels, but by developing novel technologies, this gap can be reduced.