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Point source capture from power plants

I first became aware of CO2 capture back in about 2007, when I was working as a materials scientist in a semiconductor company. I got interested in gas separation membranes, and this led me on a long journey to trying to build a very high risk technology for CO2 separation. Short story - it was too "out there", and despite seed funding from NASA we didn't get it far. But it led to a project with PNNL on carbon capture from fossil fuel, and ultimately to here.

The power sector is one of the highest-emitting sectors, with power plants inherently emitting large volumes of CO2. Back in 2008, working in the power sector meant working with coal. Retrofitting existing fossil-based power plants with carbon capture technology was back then a bold vision, and mostly a failed one. The cost and complexity of implementing CCS/CCUS in the power sector were high because the CO2 in flue gas is relatively dilute. Worse, it was polluted by trace amounts of heavy metals and sulfur and acids and ash. It was, without question, one of the harshest environments imaginable.

Worse, capturing CO2 consumes a lot of energy, which reduces the amount of electricity delivered to consumers. It is nearly impossible to retrofit a coal plant with CCS, because doing so will require about a third of the plant's energy, meaning that all of the plant's infrastructure is suddenly mis-sized. Worse, the plant probably doesn't have the spare space to re-route all the steam. Even when working in a green-field plant, substantially more fossil fuels are needed to generate the same amount of electricity in a non-CCS power plant. And the capital is not cheap. Famously, the largest attempt at a CCS plant in the US was an unbridled catastrophe.

The idea of making coal "clean" was perhaps too ambitious, and fortunately for the planet the falling price of solar and wind have obviated the need for carbon capture at that sort of scale. Today, capture is more likely to be proposed for a natural gas burning plant, and ideally in the future will only be capturing CO2 from a peaking generator, which operates only when renewables and batteries cannot. Under these circumstances the added costs of achieving net zero emissions make more sense - peaking is already expensive! - and the total burden of CO2 collection infrastructure is maybe 5-10% of what baseload capture would have required.

The push to say that CO2 capture is non-economic references coal plant implementations, which indeed are expensive. As a "successful" example of a retrofit plant, the Boundary Dam Integrated Carbon Capture and Storage project in Saskatchewan, Canada was retrofitted to the lignite-fired Unit 3 of the 50-year-old Boundary Dam power plant. The project failed to meet its pre-specified targets for costs or for sales of the CO2 for enhanced oil recovery. The demonstrated cost of capturing CO2 in Boundary Dam 3 has been calculated at about $100–$120 per tonne, which would not even be economic in the more aggressive CO2 pricing regime in the US after the Inflation Reduction Act..

The struggles of carbon capture in older generation fossil fuel plants speaks to the electricity industry as it was. Going forward, greenfield fossil fuel plants such as reciprocating internal combustion engine (RICE) natural gas plants may become an important part of future plans to mostly decarbonize the grid. Carbon capture in this contexts is expected to be much less expensive, so the cost legacy of past projects should not be considered a limit.

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