CCU or CCS? CCUS may be the answer

• Guest blogger: Juliana Monteiro, TNO

CO₂ Capture and utilization (CCU) is of often presented as an alternative to CO₂ Capture and storage (CCS). In general lines, the concept of CCU is indeed more appealing: instead of burying CO₂ underground –, CO₂ can be used as a raw material. Valuable products such as plastics and fuels can be derived from CO₂, in a circular manner, as a replacement for fossil fuels. Following this line of thinking, CCU appears to be the silver lining in the climate change cloud.

The stable CO₂ molecule and the climate challenge

To make an impact on the climate, the amounts of CO₂ to be avoided are massive. In the cement industry alone, a target of capturing and storing 552 MtCO₂ per year by 2050 was recently proposed by IEA and CSI.

Additionally, CO₂ is a rather stable molecule. This means that for CO₂ to react and be transformed into high energy products such as fuels, a lot of energy must be provided. Therefore the CO₂ utilization reactions normally take place at elevated pressures and temperatures, and using high energy reactants such as hydrogen.

Large quantities of CO₂-free renewable hydrogen will need large quantities of renewable power

CO₂-free renewable hydrogen may be produced from water, using wind electricity to power electrolysers. Safely storing and distributing hydrogen is a challenging task. By reacting CO₂ and hydrogen, drop-in fuels like ethanol or gasoline can be manufactured. However, about 1GW would be needed to produce the hydrogen required to convert 90% of the CO₂ emitted from an average cement plant to ethanol. For the sake of comparison: this is the nameplate capacity of the Fosen Vind complex in Norway, comprising 278 wind turbines – a project with expected cost of 1.1 billion euros.

Of course, building a dedicated Fosen Vind per cement plant is out of question. However, in a scenario with multiple renewable energy sources (e.g. solar and wave power) integrated in the grid, excess power is expected to be available periodically, not at the 1 GW scale, but a scenario in which dozens of MW become available is likely. This power can be used to generate relatively low cost renewable hydrogen, which can be reacted with CO₂ to generate fuels.

CCUS – a viable compromise for CCU and CCS

Therefore, the extent to which CO₂ may or should be utilized will depend on multiple factors such as the market size of the final product, the availability of renewable feedstock, and of course on the economic and environmental impacts of the technology chosen. Taking these factors into consideration, it is unlikely that CCU could ever completely replace CCS. Instead, the combination between the two approaches – CCUS – may be the optimal solution. For large scale applications such as cement plants, most of the CO₂ will need to be sequestrated, but utilization of a fraction up to 10% of the CO₂ may be beneficial.

In deliverable 5.1 of the Horizon2020 CEMCAP project we have evaluated how the addition of a CO₂ utilization component to the CCS chain –thus making it a CCUS chain – affects the CO₂ avoidance costs. The report shows that the outcome can be either positive (lowering the cost of CO₂ and even turning the full CCUS chain into a profitable business) or negative, depending on the final product characteristics.

Amongst the main characteristics affecting the CCUS chain performance are the product price, the market size, and the CO₂ avoidance of the technological route. While this performance evaluation has to be made case by case, the routes described in D5.1 may serve as guidance for the evaluation of similar products.

CO₂ product fact sheets

Given the large number of alternatives of CO₂-based products, we have collected some key information on each product in “CO₂ product fact sheets” (Links below), intended to serve as a guiding instrument when evaluating a utilization route. By presenting key factors such as market size, energy demand, technology maturity level and price of various CO₂ derived products, the fact sheets give a quick overview of the possible products and how they are related to the alternatives.

The collection of CO₂ fact sheets published in the CEMCAP website is extensive, but not exhaustive. Beyond CEMCAP, it is TNO’s intention to update the fact sheets on a regular basis, to provide as complete as possible figures in supporting the evaluation of CCUS routes.

 CCU FACT SHEETS (pdf):

• Aggregates
• Carbonated Concrete
• CO₂ food
• CO₂ greenhouse
• Cyclic carbonates
• DME
• Ethanol
• Formic Acid
• IPA
• Methane
• Methanol
• Polyols
• PPC