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A Massachusetts-based startup has figured out how to produce zero-carbon cement.
Over the past several months, in the sleepy city of Holyoke, Massachusetts, bulldozers have been tearing down a former paper mill. The newly leveled ground on the western banks of the Connecticut River is on its way to becoming the home of a big, industrial bet. If it pays off, what was once known as the Paper City could soon become the Clean Cement Capital — of the country, at least. Sublime Systems, a startup that has developed a process for producing the ubiquitous building material without releasing any carbon emissions, has chosen the site for its first commercial factory.
“It’s poetic justice,” Sublime’s CEO and co-founder, Leah Ellis, told me. “We’re excited about bringing clean technology to this community which has been damaged by a legacy of pollution from the old industry that used to happen there.”
The word cement is often used interchangeably with concrete, but it’s actually a key ingredient in the stuff that gets mixed and poured and hardened into sidewalks, roads, buildings. It is the glue that binds together sand, water, and gravel to form the fabric of our built environment. It’s also a major source of carbon emissions — 8% of the global total. And these aren’t like other kinds of emissions.
Scientists often split the climate problem into two categories. There’s the carbon that we know how to eliminate, like from power generation, home heating, and cars. And then there’s a group called the “hard to decarbonize” stuff — mostly emissions from industrial activities where clean solutions are still in early stages and not cost competitive. Cement is the poster child.
That’s because more than half of the emissions from cement come from a chemical reaction that’s intrinsic to its production. Cement consists of lime, silica, and water. It’s made by first heating up limestone in a kiln to more than 1,400 degrees Celsius (2,550 degrees Fahrenheit) — a level of heat that can typically be achieved only by burning coal or natural gas — to produce reactive lime. The bigger problem, though, is that limestone contains carbon, and as it heats up, that carbon is released as a gas. So even if you could heat the kiln with clean electricity instead of coal, there would still be carbon emitted by the process.
But Sublime has found another way. Ellis and her cofounder Yet-Ming Chiang — a serial entrepreneur who is also behind the buzzy battery startup Form Energy — developed a new way to make reactive lime that does not require limestone. Instead of heating up rocks in a kiln, they drive the chemical process with electric currents. This enables the company to avoid limestone and use a variety of other raw materials that do not contain carbon to produce lime.
When Ellis described her breakthrough to me, it sounded incredibly simple, like it might be obvious to anyone with a background in electrochemistry. “Why didn’t anyone else think of this?” I wanted to know.
“I believe this way of making cement is going to be obvious in retrospect, in a post-carbon world where you don’t use fossil fuels, where you’re penalized for CO2 emissions,” she told me. But she said there were three factors that led to this innovation in this moment.
First, we’ve reached a tipping point in figuring out how to decarbonize the electric grid. “That is the one key enabler. Once you’ve got a clean grid, that’s the tool to decarbonizing everything else.”
Second, Ellis happened to be in the right place at the right time. She started her career as a battery scientist and founded Sublime while completing a postdoc at the Massachusetts Institute of Technology. The interdisciplinary nature of the school, where she could collaborate with other departments, enabled her to expand the bounds of what she could do with her expertise.
And third, the technology Sublime uses to drive its chemical process — a device called an electrolyzer — has become much cheaper. Though electrolyzers have been around for a long time, they’ve recently benefited from increased economies of scale as interest in using them for applications like clean hydrogen production has grown.
For the past year, Sublime has been honing its process at a small pilot plant in Somerville, Massachusetts, a suburb of Boston. The new plant in Holyoke is designed to be many times larger — producing up to 30,000 tons of cement per year — though still smaller than the million tons per year that an average cement plant produces. The site is about half a mile down the river from a hydroelectric dam — a key consideration for the company, since it needs to power the plant with clean electricity.
The project is not yet fully financed, but Sublime has received $1 million in tax credits from the state of Massachusetts and is holding out hope for a federal grant from the Department of Energy’s Office of Clean Energy Demonstrations.
There are a number of other emerging methods to reduce emissions from cement, including alternative chemical combinations and installing carbon capture equipment on cement plants, but it’s far from being removed from the “hard to decarbonize” club. The question, as always, is whether Sublime and others will be able to produce a high-quality product — one that passes the strength and durability tests required for the construction industry — at scale, and at a competitive price.
Sublime’s product is certainly more expensive than conventional cement today. But its solution is cheaper than using carbon capture, Ellis said. Capturing the carbon from a cement plant generally requires a big increase in energy use. And while the technology has been under development for decades, it’s so far failed to be applied economically outside the natural gas processing industry. In a world where builders are required to use lower-carbon materials, or where there’s a price on carbon, Ellis thinks Sublime will have an advantage. Governments at various levels in the U.S. have already started to implement “buy clean” programs that require the use of lower-carbon cement for state and federal construction projects, so Sublime may have an edge in some markets once its Holyoke plant is up and running.
“Our process is true zero,” she said. “It just doesn’t emit.”
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And more of this week’s top renewable energy fights across the country.
1. Otsego County, Michigan – The Mitten State is proving just how hard it can be to build a solar project in wooded areas. Especially once Fox News gets involved.
2. Atlantic County, New Jersey – Opponents of offshore wind in Atlantic City are trying to undo an ordinance allowing construction of transmission cables that would connect the Atlantic Shores offshore wind project to the grid.
3. Benton County, Washington – Sorry Scout Clean Energy, but the Yakima Nation is coming for Horse Heaven.
Here’s what else we’re watching right now…
In Connecticut, officials have withdrawn from Vineyard Wind 2 — leading to the project being indefinitely shelved.
In Indiana, Invenergy just got a rejection from Marshall County for special use of agricultural lands.
In Kansas, residents in Dickinson County are filing legal action against county commissioners who approved Enel’s Hope Ridge wind project.
In Kentucky, a solar project was actually approved for once – this time for the East Kentucky Power Cooperative.
In North Carolina, Davidson County is getting a solar moratorium.
In Pennsylvania, the town of Unity rejected a solar project. Elsewhere in the state, the developer of the Newton 1 solar project is appealing their denial.
In South Carolina, a state appeals court has upheld the rejection of a 2,300 acre solar project proposed by Coastal Pine Solar.
In Washington State, Yakima County looks like it’ll keep its solar moratorium in place.
And more of this week’s top policy news around renewables.
1. Trump’s Big Promise – Our nation’s incoming president is now saying he’ll ban all wind projects on Day 1, an expansion of his previous promise to stop only offshore wind.
2. The Big Nuclear Lawsuit – Texas and Utah are suing to kill the Nuclear Regulatory Commission’s authority to license small modular reactors.
3. Biden’s parting words – The Biden administration has finished its long-awaited guidance for the IRA’s tech-neutral electricity credit (which barely changed) and hydrogen production credit.
A conversation with J. Timmons Roberts, executive director of Brown University’s Climate Social Science Network
This week’s interview is with Brown University professor J. Timmons Roberts. Those of you familiar with the fight over offshore wind may not know Roberts by name, but you’re definitely familiar with his work: He and his students have spearheaded some of the most impactful research conducted on anti-offshore wind opposition networks. This work is a must-read for anyone who wants to best understand how the anti-renewables movement functions and why it may be difficult to stop it from winning out.
So with Trump 2.0 on the verge of banning offshore wind outright, I decided to ask Roberts what he thinks developers should be paying attention to at this moment. The following interview has been lightly edited for clarity.
Is the anti-renewables movement a political force the country needs to reckon with?
Absolutely. In my opinion it’s been unfortunate for the environmental groups, the wind development, the government officials, climate scientists – they’ve been unwilling to engage directly with those groups. They want to keep a very positive message talking about the great things that come with wind and solar. And they’ve really left the field open as a result.
I think that as these claims sit there unrefuted and naive people – I don’t mean naive in a negative sense but people who don’t know much about this issue – are only hearing the negative spin about renewables. It’s a big problem.
When you say renewables developers aren’t interacting here – are you telling me the wind industry is just letting these people run roughshod?
I’ve seen no direct refutation in those anti-wind Facebook groups, and there’s very few environmentalists or others. People are quite afraid to go in there.
But even just generally. This vast network you’ve tracked – have you seen a similar kind of counter mobilization on the part of those who want to build these wind farms offshore?
There’s some mobilization. There’s something called the New England for Offshore Wind coalition. There’s some university programs. There’s some other oceanographic groups, things like that.
My observation is that they’re mostly staff organizations and they’re very cautious. They’re trying to work as a coalition. And they’re going as slow as their most cautious member.
As someone who has researched these networks, what are you watching for in the coming year? Under the first year of Trump 2.0?
Yeah I mean, channeling my optimistic and Midwestern dad, my thought is that there may be an overstepping by the Trump administration and by some of these activists. The lack of viable alternative pathways forward and almost anti-climate approaches these groups are now a part of can backfire for them. Folks may say, why would I want to be supportive of your group if you’re basically undermining everything I believe in?
What do you think developers should know about the research you have done into these networks?
I think it's important for deciding bodies and the public, the media and so on, to know who they’re hearing when they hear voices at a public hearing or in a congressional field hearing. Who are the people representing? Whose voice are they advancing?
It’s important for these actors that want to advance action on climate change and renewables to know what strategies and the tactics are being used and also know about the connections.
One of the things you pointed out in your research is that, yes, there are dark money groups involved in this movement and there are outside figures involved, but a lot of this sometimes is just one person posts something to the internet and then another person posts something to the internet.
Does that make things harder when it comes to addressing the anti-renewables movement?
Absolutely. Social media’s really been devastating for developing science and informed, rational public policymaking. It’s so easy to create a conspiracy and false information and very slanted, partial information to shoot holes at something as big as getting us off of fossil fuels.
Our position has developed as we understand that indeed these are not just astro-turf groups created by some far away corporation but there are legitimate concerns – like fishing, where most of it is based on certainty – and then there are these sensationalized claims that drive fears. That fear is real. And it’s unfortunate.
Anything else you’d really like to tell our readers?
I didn’t really choose this topic. I feel like it really got me. It was me and four students sitting in my conference room down the hall and I said, have you heard about this group that just started here in Rhode Island that’s making these claims we should investigate? And students were super excited about it and have really been the leaders.