The Weekend Wonk: Carbon Capture Gas Plants Planned: Are they Ready for Prime Time?

April 16, 2021

NET Power

Are gas turbines with carbon capture part of the answer?
There are reasons to be skeptical.
But, If they can build two new planned facilities, we’ll have a test case.


A new kind of power plant that doesn’t add greenhouse gases to the atmosphere is being built in the U.S., potentially providing a way for utilities to keep burning natural gas without contributing to global warming.

Net Power intends to build two natural-gas power plants in the U.S. that will have all its emissions captured and buried deep underground. The startup licensed its technology to developer 8 Rivers Capital LLC, which will work with agriculture giant Archer-Daniels-Midlands Co. to replace some emissions from a coal power plant in Illinois.

For the other plant, 8 Rivers is working with the Southern Ute Indian Tribe Growth Fund in Colorado. Both projects will be designed and developed this year, which 8 Rivers says requires spending tens of millions of dollars. A final decision on whether to go ahead with the facilities is due in 2022.

Net Power’s technology uses a new kind of turbine to burn natural gas in oxygen, rather than the air. As a result, the plant only produces carbon dioxide and water as a byproduct. The water can be frozen out of the mixture and the pure stream of CO₂ can be buried in depleted oil and gas wells or similar geological structures.

The required oxygen is secured by separating it from the air, which needs energy. But Net Power says its turbine is more efficient so that, on balance, the overall efficiency of the system matches that of an advanced natural-gas power plant that pumps its emissions into the atmosphere. Another upside of using oxygen is that Net Power plants do not produce any nitrogen emissions, which would cause local air pollution.

The startup built a functioning pilot plant in Texas in 2018 that can generate about 25 megawatts of power. The Illinois and Colorado plants will be Net Power’s first commercial-scale units. Each plant will be capable of generating 280 MW of electricity. The Colorado plant is also expected to use air cooling, which Net Power says will cut the amount of water required to zero. 

“Big projects take time,” said Cam Hosie, chief executive officer of 8 Rivers. “The most important thing for the rapid adoption of this technology is going to be that the first projects are successful.” Hosie said that about a dozen other Net Power plants are in various phases of development, with some planned to be built outside the U.S.

The Illinois power plant will inject its emissions into an already existing CO₂ well, which currently buries emissions from an ethanol production facility. The Colorado plant hasn’t decided where to bury its emissions, but 8 Rivers says that the site of the power plant is close to a CO₂ pipeline which extends the area available for storing the carbon.

Though the power plant won’t produce any pollution, environmentalists are concerned about the continued use of natural gas. The production and transportation of the fossil fuel does lead to emissions, which companies that rely on natural gas will have to mitigate.

Both plants will have access to a U.S. tax credit that amounts to about $50 for each ton of CO₂ injected into the ground. As in the case of solar and wind power, the credit seeks to subsidize early-stage climate technologies until they can compete with the existing fossil-fuel based incumbents.

There is some debate, as these twitter examples show, first a thread from Princeton’s Jesse Jenkins:

  • You can not like CCS (I’m not here to fight about that), but we can get the facts right. Million ton/year scale projects have been operating in a variety of applications across the world, many for several years. Carbon capture is not uniform. It is a diverse set of techs & uses.
  • Important: Read the costs section in this report with a grain of salt/skepticism. Figures there much less concrete. I was focused on the technology readiness section, which is the kind of thing I was searching for when I found this report. It’s solid.

Very well informed US Rep Sean Casten jumped in..

Sean Casten is U.S. Representative for Illinois’s 6th congressional district, an engineer, and a former executive in the clean energy industry:

For the uninitiated: carbon capture & sequestration (CCS) is the technology to capture CO2 from combustion tailgases, purify it then store it permanently (typically underground), enabling fossil-fueled sources to be CO2 free.

It is distinct from direct air capture (DAC) that pulls CO2 out of the air and while it can be used in non-power applications (e.g., in cement plants) the useless boondoggle is in power generation applications.

State and federal governments have thrown billions of dollars at CCS over the years. Google “FutureGen” in IL for an example of the scale of waste. Or the 45Q tax incentive to see where we still throw way too much money away on this dead end technology.

The problems with the technology though have nothing to do with technology, but are simply about basic economics and thermodynamics.

First economics: thanks to the power sector reforms created by the 1992 EPACT and FERC order 888, US power markets now dispatch on marginal price.6/ That means that every power plant in the country looks at the revenue per MWh they can earn the next hour, compares that to their marginal cost of generating a MWh and decides whether to run or not. (Yes, I am simplifying a bit and don’t mean to gloss over must-run dynamics or other complexities, but it’s close enough for a twitter thread!)

On balance, those market reforms have been an enormous boon to our economy and markets, for the simple reason that low-carbon power plants (nuclear, wind, solar, combined cycle gas turbines, etc.) also have lower marginal operating costs.

Since those reforms were passed, the nuclear fleet has gone from operating 60% of the time to 90%+. 200 GW (roughly 20% of the entire power grid) of high-efficiency combined cycle gas turbines were built. 40 GW+ of renewables were built.

Net result is that US CO2 emissions from power generation have fallen from 1300 lb/MWh to ~925 lb/MWh, all while power prices have come down. This is really important: favoring lower cost power plants drives down CO2 emissions.

But in the meantime, the coal fleet has collapsed, and for the exact same reasons. 15 years ago, coal accounted for ~50% of all MWh consumed in the country. Today it’s less than 25% and falling.

And that’s not because of economics. Once we decided to preferentially run our lowest marginal cost assets, the plants with lots of fuel and ash handling costs, inefficient power cycles, etc. couldn’t justify operation. Consumers (and the environment) won.

To be sure, the reforms from the 92 EPACT and FERC 888 weren’t perfect. In particular, they really don’t provide sufficient long-term certainty to drive capital investment. The increase in renewable construction owes more to long-term tax policy than short term spot mkts.

That means that while we now preferentially operate the low cost (and low CO2) power plants that are already built, it’s still really hard to attract the capital to build new power plants.

Ergo, operators have a bias towards least-marginal cost power plants and investors have a bias towards REALLY cheap construction costs. Nuclear benefits primarily from the former. CCGT benefits primarily from the latter.

Now let’s look at CCS. Adding gas separation, purification and storage will increase the capital cost of your power plant. That makes it harder to finance.17/ Meanwhile, all the ancillary electric loads and fuel expense to separate, purify, compress and store that CO2 significantly increase the operating costs of a plant with a CCS addition.

That means that all else equal, a power plant with CCS is going to run a lot less often than one without for purely economic reasons. Which makes the investment thesis even worse!

In the power sector, CCS is literally the ONLY low-CO2 technology that costs more to build AND costs more to operate. (e.g., Solar: expensive to build, but effectively free to operate. CCGT: cheap to build, but depends on low gas prices to economically operate.)

So while it is possible to waste a lot of money building those plants (see: FutureGen, 45Q), they are never going to operate in a carbon-constrained world that preferentially uses lowest cost power sources. All you can do is waste your investment $.

So why the heck do we still talk about CCS? Partly because the coal industry still believes in magic unicorns and has convinced a lot of legislators to do the same. Partly because we want to believe that maybe there is some tech solution we’ve yet to figure out.

But as Homer Simpson says, “In this house, we obey the laws of thermodynamics.” I’d add economics too. You can’t separate gases without spending capital dollars and burning more fuel. (As a separate but important point, it’s worth noting that even with CCS, coal is still dirty. You still have acid rain-forming compounds, asthma-causing particulate. “Clean cheap coal” is, and will always be a fiction.)

Bottom line is we have to get CO2 down as quickly as possible. And we have the opportunity to do so in a way that will save a lot of money. But not if we include CCS in the power sector. 

One Response to “The Weekend Wonk: Carbon Capture Gas Plants Planned: Are they Ready for Prime Time?”

  1. Keith McClary Says:

    CCGT = “Combined cycle gas turbine”.

    The Alberta Tar Sands promoters are big on CCS. Since it is expensive, they are advocating a boycott on “dictator oil”, so consumers will be forced to buy their bitumen.

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: