Carbon capture, utilisation, and storage (CCUS) so far has not lived up to its promise. Although its relevance for reaching climate goals has long been recognised, deployment has been slow, although as Mark Venables explains, momentum is growing, but there are still some challenges ahead.
Since the beginning of the industrial revolution, carbon dioxide levels in the atmosphere have increased by more than 45 per cent and now exceed a level of 400 µmol mol-1 in the atmosphere. Carbon dioxide is a greenhouse gas and anthropogenic emissions are a substantial driving force of climate change.
Carbon capture, utilisation, and storage (CCUS) is the process of capturing and storing carbon dioxide with the view of reducing carbon dioxide emissions to the atmosphere. This process involves a capture step, whereby carbon dioxide is separated from other gases produced in industrial processes; a transport step, whereby the carbon dioxide is compressed and transported to an industrial facility for utilisation or to a storage site via pipelines, road transport or ships; and a storage step, whereby the carbon dioxide is injected into disused oil and gas reservoirs or other suitable rock formations deep underground for permanent storage.
After considerable debate and discussion within the UK government with regards to an appropriate route forward, CCUS is now well and truly back on the agenda, as highlighted by the Ten Point Plan with investment in CCUS being Point eight of the plan for the UK’s Green Industrial Revolution. The plan has set an ambitious target of capturing 10 Tg (Mt) of carbon dioxide per year by 2030 by investing up to £1 billion to support the establishment of CCUS in two industrial clusters by the mid 2020’s, aiming for four sites by 2030.
These targets seek to build upon the decarbonisation work initiated through R&D projects in the large UK industrial clusters based in the heart of the North East, the Humber, North West, Scotland, and Wales. Most of these industrial decarbonisation projects focus on hydrogen and CCUS as the energy vectors, neither of which are new technologies. Which begs the question why has there not been widespread uptake or commercialisation already? This is what the Ten Point Plan aims to implement. Development of government policies and business plans to provide incentives to industry to include CCUS as well as development of a CCUS infrastructure.
Experience with building and operating CCUS facilities has contributed to progressive improvements in CCUS technologies as well as significant cost reductions. At around $65/t of CO2, the cost of capture at the Petra Nova coal-fired power plant in Houston, commissioned in 2017, is more than 30 per cent lower than the Boundary Dam facility in Canada – the only other commercial coal plant with capture facilities – which started operations in 2014. Detailed engineering studies show that retrofitting a coal-fired power plant today could cost around $45/t. There are now plans to retrofit as many as ten coal power plants with capture equipment (in China, Korea, and the United States). With further research, development, and demonstration (RD&D) and growing practical experience, there is considerable potential to further reduce energy needs and cost.
New technologies and ways for using or recycling CO2 other than enhanced oil recovery, such as to produce synthetic fuels or building materials, are emerging, potentially boosting demand for CO2. The growing interest in these technologies is reflected in increasing support from governments, industry, and investors, with global private funding for CO2 use start-ups reaching nearly $1 billion over the last decade according to the IEA. Several governments and agencies have been supporting innovation related to CO2 conversion technologies. For example, in June 2019, Japan released a Carbon Recycling Roadmap highlighting opportunities to commercialise CO2 use technologies over the next decade. Additionally, several prize initiatives have been held with the aim of promoting the development of CO2 conversion technologies, awarding a prize to the most innovative CO2 use applications. A notable example is the NRG COSIA Carbon XPrize.
Measurement needs for CCUS
There are specific measurement capabilities that need to be developed to support CCUS and the National Physical Laboratory (NPL) recently published the Energy Transition report highlighting measurement needs and challenges as identified by key stakeholders in the CCUS industry for each of the capture, transport, usage, and storage stages. “These key measurement needs include research around gas quality and composition, equations of state, materials integrity and corrosion, flow metering and leak detection,” Sam Bartlett, higher research scientist at the NPL says. “Carbon dioxide gas quality and composition information allows emitters to evaluate the performance and efficiency of the carbon capture technology installed on-site including solvent degradation status.
“This is critically important as monoethanolamine (MEA) is the most commonly used solvent for carbon capture, however it is toxic to humans resulting in a requirement to limit and monitor its emission. Therefore, there is a preference for the use of non-amine-based solvents which is driving research and development into novel solvent technology, as demonstrated by C-Capture who are moving to commercialise their patented solvent.”
Most carbon dioxide storage sites are located offshore at deep sea aquifers, so to deploy CCUS effectively and efficiently a transport and storage (T&S) infrastructure is required. This takes the form of a pipeline network, of which the UK has plenty from the peak of the oil and gas industry, however the pipeline system must be suitable for transporting carbon dioxide. “Therefore, rigorous corrosion and materials integrity testing is required to ensure the T&S system is robust to prevent fugitive emissions,” Bartlett adds. “Additionally, the pipeline operator would not be happy with just any old carbon dioxide being put through their network due to the risk of detrimentally damaging the infrastructure, so quality requirements will need to be agreed and adhered to by emitters or risk the wrath of a financial penalty and exclusion from use of the T&S system.
“To support safety cases and mitigate health and safety (H&S) risks associated with large releases of carbon dioxide and its impurities, accurate and continuous leak detection methods are required allowing for quantification of leaks and robust dispersion models to be developed. This research is important, not only for the H&S implications previously mentioned, but also for emission regulations purposes.
“At the temperatures and pressures proposed for use in CCUS, carbon dioxide can exist as a liquid, gas or a mixture of both. For operational process control to be effectively utilised, it is critical that accurate models are available to understand the phase behaviour of the carbon dioxide fluid at all stages. Equations of state can be used for this purpose, however there is a knowledge gap when it comes to fluids like carbon dioxide that can exist in multiple phases across narrow phase boundaries. These properties also make flow metering of carbon dioxide challenging, which is an essential element of the CCUS infrastructure for process control, custody transfer, emissions trading, and the fundamental method for assessment of storage capacity.”