Cleaning Up The Carbon Capture Storage Sustainable Energy Debate

Carbon Capture Storage (CCS) continues to be dirty words in the sustainable energy debate. The costs look too big, the rewards too temporary and for green campaigners, CCS has been branded as a means for energy-intensive industries to carry on with ‘business as usual’.

Meanwhile, with CCS methods limited by lack of tests and piloting at a larger scale, industries like oil and gas, food and beverages, cement, paper and chemicals keep on needing to pump carbon into the atmosphere as part of their operations.

For example, the food manufacturing globally is estimated to contribute around 17.3 billion metric tonnes of CO₂ per year — up to 19 times that of commercial aviation.

None of the criticism of CCS has changed the fact that we need more facilities, and sooner rather than later. It’s a fantasy that the UK, as well as many other nations, can avoid carbon emissions in the near term, because while decommissioning coal-fired power stations has made an instant impact on CO₂ figures, other future emissions reductions will be much more difficult to achieve without CCS.

CCS is critical for the interim period before we solve the issues of energy storage and reach a phase where the use of , and is the most cost-effective way the world will be able to meet COP commitments and avoid the hazardous – if not catastrophic – CO₂ levels in the environment of 450 ppm and above.

With this in mind, the UK´s 2021 net zero strategy has pushed for more CCS projects in order to bring down costs, but the impetus for change is still small-scale. For real change to occur, there will need to be a new environment for industries generally: more immediate penalties and incentives around carbon emissions are needed to change the basis of decision-making: taking into account the real costs of climate change versus practical efforts to slash carbon emissions.

Creating more options for Carbon Capture Storage

The CCS technologies that could be used in industries such as depends on a number of factors including plant size and location, but it is clear that amine scrubbing (a process used to separate CO₂ from flue gas now validated at the commercial scale for the treatment of flue gas from coal fired power stations) could be used effectively with this industry to minimise emissions. The estimated costs for amine scrubbing are in the range of 90–100 euros per tonne of avoided CO₂. 

Another potential technology relates to calcium looping (CaL). This is the continuous temperature swing cycling of a calcium-based CO₂ sorbent between two reactors, a calciner and carbonator, where CO₂ is released and absorbed, respectively.

Like all CCS technologies, one of the major issues for CaL is cost and the likely energy penalty imposed by the technology. In terms of cost, seven studies produced costs ranging from $16 to 38 per tonne CO₂ avoided. In the absence of full-scale demonstration units, calcium looping technology is very cost competitive with amine scrubbing and offers a much lower energy penalty.

In addition, compared to amine scrubbing, most of the industries may benefit from calcium looping by effective integration to their processes where limestone is the waste material and fresh calcium oxide is needed.

More recently, cement manufacture from the wastes from the looping process has been demonstrated at the kilogram level. Research from the teams at Cranfield and Imperial College has demonstrated that for the first time at a pilot-testing level, using near industrial-scale conditions that commercial-grade cement can be manufactured from the process and that the rate at which the sorbent decays can be slowed.

The teams were able to demonstrate this by using limestone simply treated with hydrogen bromide as the sorbent in the CaL process. Using this material, the first demonstration of 100% O₂ firing in the calciner was performed.

These results have been backed up by tests with 80% oxygen firing in the calciner of a 1.7 MWth pilot plant unit. This result suggests that a reduction in capital costs of about 21.7% might be possible; and a 14.3 and 27.4% reduction in the cost of electricity and CO₂ avoided, respectively. 

There remains a clear need to demonstrate the technology at a larger scale, and the real potential for a future of decarbonised industries. Cranfield has been working, for example, with Calix, the firm spearheading the LEILAC (Low Emissions Intensity Lime and Cement) pilot plant facility hosted by Heidelberg Cement in Belgium which is situated immediately next door to the cement plant. LEILAC is a calciner, it takes some of the raw meal from the cement plant and calcines it — producing a pure stream of CO₂ suitable for CCS — before being made into cement.

Incentivising Carbon Capture Storage

As with any technology there needs to be constant cycles of use and testing to finally optimise the potential of the approach, to both find the most effective applications for different industries and extend the use of technologies in ways that radically reduce the capital costs involved.

The total global investment in research and development of CCS technologies has typically been around two orders of magnitude lower than the total investment in development of other renewable energy sources.  

It is a common misconception that CCS and renewables are competing technologies, whereas both are being deployed to achieve the same goal – reduce the anthropogenic CO₂ emissions in a fight to mitigate climate change.

Therefore, we need to develop hybrid technologies that will exploit synergy between renewable energy sources and low-carbon fossil fuel power generation that leads to both reduced curtailment of renewable energy sources and reduced economic penalties of CCS.