Dave Elliott: There was a time when carbon capture and storage (CCS) was seen as a major way ahead, allowing fossil fuels to be burnt with impunity – just add a CCS unit to the power plant. So the UK government had scenarios heavy on gas and even coal use, with CCS taking care of the emissions. Renewables were relegated to being “also rans”, alongside nuclear. However, while nuclear is still in the mix in a recent UK government Department for Business, Energy and Industrial Strategy (BEIS) scenario, at 13 GW by 2035, renewables now dominate with 45 GW by 2035, and CCS is all but forgotten – 1 GW by 2035 at most, with gas use declining rapidly and coal gone entirely. CCS has increasingly been seen as expensive and uncertain – the UK abandoned its £1bn CCS power plant competition in 2015. It’s the same elsewhere. The flagship US Kemper coal CCS project has been halted. Norway, a CCS pioneer with its enhanced oil recovery technology, has now cut its CCS funding. Some work on CCS is still continuing, and there are around 17 projects running worldwide, although all but two of them are industrial gas processing or chemical plants, not power plants, and only four have dedicated geological CO2 storage. While CCS may have some important industrial applications, as far as the power sector is concerned the overall message seems to be that for the moment it is “game over” for CCS, in the EU especially, with renewables offering a cheaper option. While CCS and BECCS now look like long shots, there is a bit more interest in a linked idea – carbon capture and utilization (CCU), which could also be used with biomass (BECCU). This approach avoids the need to store captured CO2, which would reduce some costs and risks. Instead, the CO2 is used as a feedstock for chemical conversion, using hydrogen, to synfuels or other products. If these products are valuable, that can offset the cost of CCU and the subsequent conversion process. However, it needs hydrogen. Hydrogen is mostly produced at present from the high-temperature “steam reformation” of fossil gas so, as well as an energy cost, there is a CO2 output to deal with. To reduce that, we would have to go back to CCS again; we would be no further forward. But, even though it is currently more expensive, the availability of non-fossil hydrogen from the electrolysis of water, using surplus renewable electricity, might give CCU a boost at some point, enabling conversion of CO2 to methane, methanol or whatever without more CO2 resulting from the hydrogen production. Although costs are still high, that is already being done with renewable hydrogen in some power-to-gas projects in Germany and elsewhere, with the methane being used for power generation, heating or in vehicles. Of course, burning the methane creates CO2, but since that was initially captured from a power plant exhaust, the overall process can be roughly carbon neutral.
Physics World 5th Sept 2018 read more »