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Most of the power sector’s emissions come from a small minority of plants

Most of the power sector’s emissions come from a small minority of plants

The world seems to be simultaneously on fire and flooding, and the latest expert report indicates that we’ve just about run out of time to avoid even more severe climate change. All of that should leave us in a place where we are looking for ways to cut carbon emissions as quickly and economically as possible.

Some good news in that regard came via the recent release of a paper that looks at how much each individual power plant contributes to global emissions. The study finds that many countries have a significant number of power plants that emit carbon dioxide at rates well above either the national or global average. Shutting down the worst 5 percent of this list would immediately wipe out about 75 percent of the carbon emissions produced by electricity generation.

CARMA revisited

It’s easy to think of power generation in simple terms, like “renewables good, coal bad.” To an extent, that’s accurate. But it also compresses all power generation, from “somewhat bad” to “truly atrocious,” into a single category. And it’s clear from a variety of research that this isn’t entirely accurate. Depending on their vintage, many plants convert fossil fuels to power at different degrees of efficiency. And some of the least efficient plants are only brought online during periods of very high demand; the rest of the time, they’re idle and produce no emissions at all.

The interactions among these factors determine whether a given power plant is a major contributor to emissions or simply part of a country’s background noise of carbon output. If we had a global inventory of emissions and production from every power plant, we could use that to identify the worst offenders and have a target list for efficiently lowering our carbon output.

And, in fact, we did have one—emphasis on the past tense. Using data from 2009, someone had put together the Carbon Monitoring for Action database, or CARMA. Now, nearly a decade later, three researchers from the University of Colorado Boulder (Don Grant, David Zelinka, and Stefania Mitova) have used 2018 data to build an update to CARMA, providing emissions data that’s likely to be far more current.

This is a much larger task than it might seem. Some countries provide detailed emissions data on a per-plant level, meaning that their data could simply be imported straight into CARMA. But many others do not. For those countries, the researchers relied on everything from production data obtained by the International Energy Agency to engineering specifications for individual plants.

When they identify the largest sources of uncertainty in their data, they find it mostly clusters in the smaller plants, which are necessarily going to have the least impact on the overall emissions. For the large facilities that are likely to be major contributors, the data is usually very good.

The worst of the worst

It should surprise nobody that all the worst offenders when it comes to carbon emissions are coal plants. But the distribution of the highest polluting plants might include a bit of the unexpected. For example, despite its reputation as the home of coal, China only places a single plant in the top-10 worst (bottom-10?). By contrast, South Korea has three on that list, and India another two.

In general, China doesn’t have a lot of plants that stand out as exceptionally bad, in part because so many of its plants are similar in vintage, built during a giant boom in industrialization. As such, there’s not a lot of variance from plant to plant when it comes to efficiency. By contrast, countries like Germany, Indonesia, Russia, and the US all see a lot of variance, which means that they’re likely to have some highly inefficient plants that are outliers.

Put a different way, the authors looked at how much of a country’s pollution was produced by the worst 5 percent when all of the country’s power plants were ranked by carbon emissions. In China, the worst 5 percent accounted for roughly a quarter of the country’s total emissions. In the US, the worst 5 percent of plants produced about 75 percent of the power sector’s carbon emissions. South Korea had similar numbers, while Australia, Germany, and Japan all saw their worst 5 percent of plants account for roughly 90 percent of the carbon emissions from their power sector.

Globally, the worst 5 percent of power plants when it comes to carbon emissions account for 73 percent of the total power sector emissions. That worst 5 percent also produce over 14 times as much carbon pollution as they would if the plants were merely average.

All options are good

Obviously, finding ways to shutter those plants and replace them with emissions-free alternatives would cut the power sector’s emissions by 73 percent and total emissions by about 30 percent. But that’s not always possible, so the authors looked at several ways those plants could do better while continuing to produce electricity.

Simply boosting each plant’s efficiency so it was average for the country would drop power sector emissions by a quarter and up to 35 percent in countries like Australia and Germany. Switching them to natural gas, which produces less carbon dioxide per amount of energy released, would drop global emissions by 30 percent, with many countries (including the US) seeing drops of over 40 percent. Again, because China doesn’t see a lot of variance among its plants, these switches would have less of an impact, being in the area of 10 percent drops in emissions.

But the big winner is carbon capture and storage. Outfitting the worst of the plants with a capture system that was 85 percent efficient would cut global power sector emissions in half and total global emissions by 20 percent. Countries like Australia and Germany would see their power sector emissions drop by over 75 percent.

Overall, these are massive gains, considering that it’s not unreasonable to think that the modifications could be done in less than a decade. And they show the clear value of focusing planning on targeting the easiest wins when it comes to lowering emissions. That function could be accomplished by governmental planning. But placing a significant price on carbon could also force the private sector to plan based on emissions efficiency—something they currently have little or no incentive to do in many countries.

Environmental Research Letters, 2021. DOI: 10.1088/1748-9326/ac13f1  (About DOIs).

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