Imagine you’re a corporate sustainability exec and your company is planning to build a new data center. You’ve managed to convince the higher-ups to pay extra to use low-carbon building materials, lest the project blow up your brand’s emissions goals. But when you meet with the general contractor hired for the job, they don’t actually know of any low-carbon concrete purveyors in the area. Concrete is a hyper-local industry by necessity — you can’t hold the stuff for more than 90 minutes or so before it hardens and becomes unusable.
So here you are, one of the few people with the power and budget to pay a premium for zero-emissions concrete — a product that must become the standard if we are to stop climate change — and you can’t even get your hands on it.
This is, more or less, the situation Microsoft has found itself in. Last year, the company’s indirect emissions rose 31%, primarily due to the construction of new data centers. Cement, the main ingredient in concrete, is one of the most carbon-intensive materials on the planet, responsible for 6% of global emissions, according to Rhodium Group’s estimate. Low-carbon cement exists and is starting to be manufactured at a small scale, but first movers with deep pockets like Microsoft can’t necessarily access it.
To solve this and help clean cement startups access a bigger pool of buyers, Microsoft is leading the development of a new market for low-carbon cement — what climate finance experts call a “book and claim” market.
The tech giant has signed a memorandum of understanding with Sublime Systems, a Massachusetts-based cement startup, saying that it will buy “environmental attribute certificates” from Sublime’s first commercial cement plants. Microsoft will “book” the environmental attributes — the greenness, for lack of a better word — of Sublime’s cement, and “claim” those attributes in its own emissions accounting.
Let’s get a collective groan out of the way. Yes, once again, the business community is proposing a sort of carbon credit system as the best way — possibly the only way — to scale climate solutions. These certificates, however, have at least one notable difference from the beleaguered carbon offsets you’ve likely heard so much about: They are tied to a physical product. Microsoft won’t be buying one ton of CO2 avoided or removed from the atmosphere and then subtracting that from its overall emissions ledger. It will be buying the rights to say that it used one ton of cement with a carbon intensity of zero (or whatever the carbon intensity of Sublime’s product ends up being). Instead of neutralizing its cement-related emissions by paying someone to plant trees, it’s doing so by enabling Sublime to sell its clean cement to local buyers at a competitive price.
“It tremendously simplifies our logistics,” Leah Ellis, the CEO and founder of Sublime Systems told me, by solving the unavoidable problem that at this early point in the company’s development, it would be impossible to deliver its cement to all the early adopters willing to pay extra for it. “We end up doing death by 1,000 pilots if we have to pilot here, there, everywhere. Being able to use the cement locally and have the carbon attribute be counted against Microsoft's Scope 3 emissions is a really innovative way to unstick this whole problem.”
That’s key. Scope 3 is a category of emissions that encompasses all the carbon that is related to a business but not directly produced by it. When Microsoft builds a data center, it has no direct control over the process used to make the cement that goes into the building. In theory, it does have the ability to say, “We want to use clean stuff, not dirty stuff.” But in reality, companies are struggling to effect change within their supply chains.
“The thing to understand right out the gate is that basically no major consumer-facing company that uses things like steel or aluminum or cement knows where their stuff actually comes from,” Stephen Lezak, a researcher focused on carbon markets at the University of California, Berkeley, as well as at Oxford University, told me. He thinks that’s going to change, and hopes that in 15 years we all look back on this fact in horror. But in the meantime, “the urgency of the climate crisis requires using high integrity tools that aren't ideal, but still preserve fundamental integrity from a carbon accounting perspective,” he said.
Microsoft, for its part, told me it sees this transaction as a near-term solution and “prioritizes buying and installing physical product first” i.e., before buying certificates, “where technical, geographical, and supply chain considerations align.”
Sublime is currently building its first commercial plant in Holyoke, Massachusetts, which will use its unique zero-emissions process to produce 30,000 tons of cement per year. The Department of Energy awarded the company an $87 million grant to fund the project earlier this year. Holcim and CRH, two of the largest building materials companies in the world, have also invested in Sublime and agreed to purchase a large portion of the volume produced by the first plant.
Ellis hopes the deal with Microsoft will help attract additional investment and get the company through its “awkward teenage years.” Sublime needs to show investors that “people want this material, people will pay that green premium so that we can drive up the volume so that that premium goes away,” she said.
As with carbon offsets, there are still ways to game the system. Microsoft recently co-authored a report with the clean energy think tank RMI describing what a larger book and claim market for clean cement might look like and what questions need to be answered to ensure the market is credible. Until clean cement is just as cheap or cheaper than conventional cement, it’s pretty clear this kind of market will help reduce emissions. But should the environmental attributes be tied to cement, or to concrete? How should the carbon intensity be calculated? How will emissions be tracked and traced from the producer to the contractor to the building itself?
Perhaps the most critical question is how to avoid double-counting. If Microsoft is buying the right to say it used clean cement, what can the company that bought the actual cement say? Will it be able to brag that its building is green?
When I posed this question to Ellis, and Ben Skinner, a manager at RMI and one of the authors of the report, each gave me a version of the same answer: Yes and no.
Ellis launched into a passionate monologue about the concrete companies and contractors and structural engineers who should be celebrated for taking the risk of using a new material. “This problem of cement emissions is so intractable,” she said. “We need to make cement more visible. We need to talk about this more. We need more people to care. And so that physical embodiment, having it stamped ‘Sublime cement,’ and having a plaque that shows the public, hey, these are the emissions reduced by this thing you see here, you want to celebrate that physical embodiment.” At the end of all this, she added, “And by no means am I saying that you should double count.”
The suggestion is that it should be possible to separate carbon accounting and green marketing. If Microsoft has booked the green attributes of a delivery of cement, the contractors or building owners who used the physical stuff should not be able to claim they used clean cement on their emissions balance sheets, Skinner said. (What number they should use is a tricky question that will have to be solved.) But perhaps they still deserve some kind of recognition.
What kind of recognition, Lezak told me, is a gray area. “There's a really difficult part of this whole conversation, where you start anchored in material science and climate science and everything is really rigorous,” he said. “And at some point, the train sort of moves on to the political economy track, and it's really tough because you look for the same sort of black and white answers to these questions and they just don't show up.”
The details of the Microsoft deal and who can claim what are still being negotiated. At the same time, RMI and a new nonprofit called the Center for Green Market Activation have started work to stand up a larger book and claim market for cement. Their goal is to develop standards for how these certificates should be created, traded, and used so that companies that do not have the expertise or budget or resources that Microsoft has can access them. “We do think that it's possible to create a really high integrity system,” Skinner, told me.
Whether you like this idea or hate it, get ready to hear a lot more about it. The Center for Green Market Activation, which launched in June, is working to develop book and claim markets across a range of carbon intensive industries, including aviation, trucking, maritime shipping, and chemicals. There is one clear alternative to these paper-trading schemes — regulations that require companies to use more green materials over time. But proponents don’t see that happening anytime soon.
Lezak, though initially skeptical of these markets, has grown to support the idea. “There are people out there arguing that if you want to claim the emissions reduction in green steel, you need to make sure that the green steel actually shows up on your factory floor,” he said. “That's a beautiful idea, but you're talking about potentially pulling out the rug from billions of dollars of high integrity carbon finance.”
Editor’s note: This article has been updated to reflect the correct portion of the output from Sublime’s first plant Holcim and CRH have agreed to purchase.
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