Scientific studies of climate change have reached a sobering conclusion. It won’t be enough just to make deep reductions in carbon dioxide releases. By the second half of this century, all CO₂ emissions must be removed from the energy system.
This requirement means capturing 90% of the CO₂ emissions from power plants and industrial facilities won’t be sufficient. Virtually all of the CO₂ must be captured and at an affordable cost. Is carbon capture and storage (CCS) up to the tougher job? The short answer- yes.
A 2019 study published by the International Energy Agency (IEA) concludes that 90% capture is not a cap, but “an artificial limit” that is a “historical benchmark, originally based on the economics of capture.” The study concludes that 99.1% CO₂ capture on gas plants and 99.7% on coal plants increases the cost of electricity by only 7% compared to 90% capture. The capture of 99+% of a plants’ CO₂ makes them essentially zero CO₂ emissions. In other words, the concentration of CO₂ found in the flue gas matches that of the ambient air, at current atmospheric CO₂ concentrations of 410 ppm.
Capture technology is making significant progress toward these net neutral capture rates. Three years ago, NRG’s Parish Plant in Texas installed carbon capture on a 240 MW portion of the plant. The project, called Petra Nova, was designed to capture 90% of CO₂ at a design rate of 4776 metric tons of CO₂ per day. The project was built on time and within budget. DOE will publish a report on the plant’s operating performance sometime this year. In the meantime, CATF hired a consultant to review the hourly emission data the plant submitted to EPA during 2017-2018. We found the plant to be quite successful, capturing at the target rate for long periods. The data showed that the cogen plant (which supplies steam to the capture equipment) and the capture equipment could be started up quickly. As might be expected with a first-time application, the data also showed periods where the capture equipment was not available, and future plants will need to reduce the frequency of downtime.
Petra Nova’s success is leading to improvements in future projects:
- Next plants will cost less to build– Mitsubishi Heavy Industries (MHI) supplied the capture equipment used at Petra Nova. MHI states that the next plant will be 30% cheaper than Petra Nova based on what they learned. Part of this cost reduction is a new solvent that has better performance leading to more efficient equipment and improved integration.
- Next Plants will target higher CO₂ capture rates– In September, DOE awarded funding for engineering studies of capture technology from coal and gas plants. One of them, the 816 MW unit of the Prairie State plant in Illinois, will be designed to capture 95% of the CO₂ the plant emits.
Petra Nova illustrates the power of “learning by doing.” More projects mean more advances in performance and cost. With enough new projects, advances like 99+% capture rates will be standard for industrial plants and power stations around the country.
We know from experience how powerful “learning by doing” can be. Two decades of sulfur dioxide federal regulation drove scrubber installations and lowered costs by 50% and increased sulfur removal from just over 70% to well above 95%. The costs of wind power fell in recent years as federal and state incentives drove greater wind project development. More CCS projects, however, will depend on Congress passing more robust policies that make new capture projects economic. The same cost reductions can happen with carbon capture if Congress has the political will.