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When we talk about carbon removal, we often focus on “direct air capture” facilities — big factories that suck carbon dioxide out of the ambient air.
But a simpler and easier way to remove carbon from the atmosphere may exist. It’s called “enhanced rock weathering” — grinding up rocks, spreading them out, and exposing them to the ambient air — and it works, essentially, by speeding up the Earth’s carbon cycle. Enhanced rock weathering recently got a major vote of confidence from Frontier, a consortium of tech and finance companies who have teamed up to support new and experimental carbon removal technologies.
Frontier’s members include Stripe, Meta, Alphabet, Shopify, and McKinsey & Company. It aims to buy nearly $1 billion of various forms of carbon removal in the next few years — an intervention meant to spur commercial and investor interest in the sector.
In this episode, Jesse Jenkins, an energy systems expert and professor at Princeton University, and I talk with Jane Flegal, a former Biden White House climate adviser and now the market development and policy lead at Frontier, about the promise of enhanced rock weathering and why Frontier just spent $57 million to do it.
Subscribe to “Shift Key” and find this episode on Apple Podcasts, Spotify, Amazon, or wherever you get your podcasts.
You can also add the show’s RSS feed to your podcast app to follow us directly.
Here is an excerpt from our conversation:
Jane Flegal: So enhanced weathering is a carbon removal process that speeds up a natural process which is weathering of alkaline materials. And so weathering happens naturally, it actually drives what makes the earth habitable in the first place. It just happens over very, very long periods. So essentially what happens is that rocks slowly erode when they come into contact with acid rain essentially and —
Robinson Meyer: Naturally acidic rain?
Flegal: Yeah, not like acid rain the way we think of it, rain that is acidic because it has some dissolved CO2. And so that acidic rainwater interacts with rocks and erodes them, and it results in CO2 being stored either as a solid carbonate or as a bicarbonate. So that happens naturally, again, on very long time periods.
Meyer: And I just want to interrupt before we go any further. What then happens, right, is that the CO2 winds up being dissolved as a bicarbonate. It goes into the ocean.
Flegal: Into the ocean.
Meyer: And then what happens? It’s turned into ...
Flegal: It sinks and becomes part of the Earth’s crust.
Meyer: Right. Or it gets turned into a shell, a creature’s shell, and then it sinks again.
Flegal: It is functionally stable. It is thermodynamically pretty much impossible to reverse.
Meyer: And you kind of said this, but I do want to draw it out: This is the carbon cycle. This is a central Earth science process. There’s nothing fancy about this.
Jesse Jenkins: The problem is it takes centuries to play out. It’s just moving on geologic time. But this idea of enhanced weathering means we can potentially speed that up, right?
Meyer: Sorry, I just want to — this is, like, the whole problem of climate change, right? The problem of climate change is that we take fossil fuels and carbon that’s stored in geological storage out of the ground on historic time scales, on decadal ... you know, every year we take millions of tons of it out of the ground, and then it would only be restored back to the ground by this extremely slow process.
Flegal: One way to think about carbon removal is, like, taking stuff out of the fast cycle and putting it into the slow cycle, basically. And essentially, you either inject CO2 underground, where it’s where it’s stable, or you turn it into salt. These are kind of the options.
And so enhanced weathering, to exactly this point, it’s enhanced for a reason, right? There’s regular old weathering, and then there’s the enhanced kind, which aims to speed up this process that typically takes millennia to years or days by either using more reactive materials than the normal rocks that would just weather naturally or increasing the surface area of the material that is exposed to CO2. So grinding up rocks into very, very fine fine powder and exposing that material to more favorable environments.
This episode of Shift Key is sponsored by Advanced Energy United, KORE Power, and Yale …
Advanced Energy United educates, engages, and advocates for policies that allow our member companies to compete to power our economy with 100% clean energy, working with decision makers and energy market regulators to achieve this goal. Together, we are united in our mission to accelerate the transition to 100% clean energy in America. Learn more at advancedenergyunited.org/heatmap
KORE Power provides the commercial, industrial, and utility markets with functional solutions that advance the clean energy transition worldwide. KORE Power's technology and manufacturing capabilities provide direct access to next generation battery cells, energy storage systems that scale to grid+, EV power & infrastructure, and intuitive asset management to unlock energy strategies across a myriad of applications. Explore more at korepower.com — the future of clean energy is here.
Build your skills in policy, finance, and clean technology at Yale. Yale’s Financing and Deploying Clean Energy certificate program is a 10-month online certificate program that trains and connects clean energy professionals to catalyze an equitable transition to a clean economy. Connect with Yale’s expertise, grow your professional network, and deepen your impact. Learn more at cbey.yale.edu/certificate.
Music for Shift Key is by Adam Kromelow.
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Building a data center is also quite carbon-intensive.
When I helped start Heatmap News three years ago, I didn’t think I would be writing this much about big tech companies.
I knew that, sure, they were crucial to America’s ability to develop and scale some next-generation emissions-reducing technologies. (By then, Microsoft had already started its huge carbon removal purchasing program.) And, yes, I knew they bought a lot of renewables. But I still understood their clean energy programs chiefly as an employee perk — a way for some of the economy’s richest firms to show their largely urban, college-educated, and liberal employees that they cared.
Perhaps that was true once. It’s not true anymore. Over the past several years, the tech companies have become major electricity consumers and producers in their own right. Artificial intelligence has turned their electricity procurement and development businesses into core operational competencies. (Meta and Microsoft have even considered entering the electricity trading business.) Some of the thorniest questions in climate policy were first encountered by these tech companies.
More importantly, their hunger for electricity has transformed them into quasi-industrial companies — and given them enough heft in the market to sometimes counterbalance (and sometimes collaborate with) the utilities and fossil fuel firms that previously steered the sector. As such, they’re now crucial parts of the U.S. decarbonization story.
Three companies in particular dominate the artificial intelligence cloud business: Google, Amazon, and Microsoft.
The country’s best-known frontier labs, such as OpenAI and Anthropic, rely on these companies to provide their compute power; Amazon Web Services is the backbone of virtually the entire online software industry. Amazon, Google, and Microsoft account for more than half of the country’s data center power capacity, according to the investment firm Jeffries.
So these companies’ emissions are, in a sense, not only their own; they also give us a view into the AI industry’s carbon footprint more broadly.
Over the past two weeks, all three of these cloud providers released their energy and emissions data for the past year, and we’ve looked at the top line findings from these reports in past editions. Today I want to briefly dive into what they could mean together.
Let’s handle the part you already know: Everyone’s emissions are up.
Microsoft’s emissions grew by 25% last year, their largest year-over-year leap since the pandemic. Amazon’s emissions leapt by 16%, its largest one-year increase ever. Google’s emissions increased by 18%, rising above their pre-pandemic level.
This surge will make the companies’ climate goals increasingly difficult to meet — and some of them are coming up fast. Microsoft has pledged to become ‘carbon negative’ by 2030, meaning it must remove more climate pollution from the atmosphere than it emits in that year. Google has pledged to achieve net zero by 2030, a goal that requires — by its own estimate — cutting its emissions in half by that year, as compared to their 2019 level. Amazon, meanwhile, has pledged to achieve net-zero in its operations by 2040.
All three firms’ greenhouse gas emissions are up because of the AI data center boom. Microsoft consumes nearly four times as much electricity as it did before the pandemic; Google’s electricity use has more than doubled.
These companies’ energy use has swelled, too, but at least as of last year, nearly all of their energy demand still took the form of electricity. When we think about “electrification” in the national context, perhaps we should think at least as much about these AI megalodons as we do about heat pump or battery manufacturers.
Amazon, to its shame, does not publish recent electricity usage data, so it doesn’t appear on either of these charts.
But outsiders have estimated its power consumption based on the numbers it does publish. Hendrik Rood, an IT researcher and consultant in the Netherlands, calculates that Amazon’s data center business used 78,000 gigawatt-hours in 2025. That would mean it consumes nearly as much electricity as Microsoft and Google combined.
As I cautioned yesterday, some of these figures are already outdated. Although all three companies just released their 2025 sustainability data, Microsoft brackets its report to the fiscal year, which ended on June 30, 2025. Google and Amazon’s data covers the calendar year.
In what might be a quirk inherent to the genre, all three sustainability reports have a somewhat defensive tone (or at least a writing style that tries to anticipate quibbles). These companies know that their sustainability pledges, embraced in the heady flush of 2020 and 2021, have become much more difficult to fulfill in the AI era. And they want you to know that all of their emissions could be worse — if not for their corporate policies, pollution might be much higher.
I can’t say I find these counterfactuals entirely believable. We don’t know what Google or Microsoft or Amazon would do if, say, computing were more energy intensive or a certain process more environmentally damaging. And Jevon’s paradox suggests that every gain in efficiency — especially for a service as in-demand as AI — will make it cheaper to use AI, therefore raising its energy demand.
But I do think it’s worth sharing these claims to get some perspective. Google, for its part, says that its corporate emissions would be five times higher than they are if not for its total slate of policies:

Microsoft takes a more clinical approach. It selects four of its corporate policies: “carbon-free electricity, sustainable fuels, XBOX console efficiency,” as well as efforts to decarbonize its Surface tablet production. If not for these interventions, it says, it would have emitted 34 million tons of greenhouse gas into the atmosphere last year, not the 21 million tons that it did produce.
For all the focus on the difficulty of powering data centers (including by Heatmap), electricity does not drive most of these companies’ emissions — or it didn’t in the first half of last year, at least. The majority of Microsoft, Google, and Amazon’s greenhouse gas emissions came from what are dubbed “scope 3” emissions, a somewhat nebulous category that includes buildings, employee travel, and the full carbon footprint of their supply chain. This category reflects the AI boom in its own way.
(Skip this if you’re a sustainability nerd: In the classic schema used for corporate emissions accounting, “scope 1” emissions are direct fossil fuel pollution from an asset that the company owns or controls, “scope 2” emissions are pollution associated with the electricity, steam, or chilled water purchased by the company, and “scope 3” emissions are everything else — pollution from the company’s upstream supply chain and its downstream product use. I find this scheme makes somewhat more sense for businesses like airlines and automakers than it does for technology conglomerates. But that’s a different newsletter.)
It makes sense, then, that Amazon should have huge scope 3 emissions. The scope 3 subcategory called “Purchased Goods and Services” drives the largest share of its emissions; these include pollution from goods and services that Amazon buys for its employees to use, as well as all the embodied carbon in its line of Amazon Basics products.
But the biggest driver of scope 3 emissions — and thus for emissions overall — for Microsoft and Google came from “capital goods,” a category that covers new construction, physical assets and other fixed infrastructure used to produce products and services. More than 40% of Microsoft’s total emissions came from capital goods, and they made up more than 9 million metric tons of the company’s greenhouse gases. Google doesn’t fully aggregate out its “capital goods” category, combining it with the “use of sold products” subcategory, but it was responsible for almost 9 million tons as well.
These capital goods include the new data centers themselves: all the cement, steel, server racks, and silicon that actually make up the physical infrastructure supporting the AI boom. Here at Heatmap, we often focus on the electricity sector because it’s where so much change. But it’s good to remember that construction remains enormously carbon-intensive, and the literal buildings that house AI are, in many cases, still driving a disproportionate amount of emissions.
The July 4 heat wave showed just how far the metropolis has to go to reach its decarbonization goals.
New York City’s decarbonization plan has stalled. The events of this year’s Fourth of July weekend all but prove it.
The temperature in the city reached as high as 100 degrees Fahrenheit on Thursday, July 2, the hottest it’s been here in 14 years. As New Yorkers blasted their air conditioners to stay cool, utilities drew on all of New York’s resources to serve the resulting electricity demand for cooling. These included a fleet of dual-fuel power plants, which can burn both oil and natural gas and encompasses many of its peakers, which turn on to deal with spikes of demand.
Those dual-fuel plants pushed over 10 gigawatts of electricity onto the grid on the evening of July 1— about a third of the total load in the state — and hit similar peaks on the 2nd and 3rd. The peaker fleet owned and operated by the New York Power Authority was operational for over two-thirds of the heat wave, which persisted for four consecutive days, while some ran nonstop from 7 a.m. July 2 to 3 a.m. July 4, according to NYPA.
In response to questions about the use of its peakers during the heat wave, a NYPA spokesperson told me, “During times of peak energy demand, like last week’s heat wave, the state’s independent grid operator called upon NYPA’s Small Natural Gas Power Plants to run well beyond their typical usage to meet high energy needs and prevent localized blackouts.”
While specific generator information is a protected trade secret, they said, “capacity suppliers are critical resources to meet system peak loads like those experienced during the recent heatwave.”
And yet still, over 100,000 people lost power during the heat wave. Real-time electricity prices in the area of the New York grid that includes the city got as high as $1,465 per megawatt-hour on the evening of July 3, according to data collected by Grid Status.
At the same time, the latest addition to New York’s non-carbon electricity generation fleet, a transmission line from Quebec that can transmit up to 1,250 megawatts known as the Champlain Hudson Power Express, was struggling. It experienced an unplanned outage on July 1, the first day of the heat wave, followed by a second outage beginning on July 4 that still had not been resolved as of Friday.
Since 2014, the city has had an aspirational goal of reducing emissions by 80% of its 2005 levels by 2050. CHPE was a major part of that plan, which also included offshore wind and utility-scale solar. There has been progress: Of the 1,000 megawatts of solar the city aims to have installed by 2030, about two thirds have been built. Even so, about 90% of New York City’s electricity came from fossil fuels in 2025, according to the city’s comptroller.
Why the difficulty decarbonizing? Blame a mixture of policy and geography. New York City is dense and has a lot of old buildings with old heating systems. Reducing consumption of fossil fuels requires getting cars off the road (congestion pricing) and retrofitting buildings with electric appliances (Local Law 97).
But that’s the demand side — the supply side is far trickier. Utility-scale non-carbon-emitting power on the orders of hundreds of megawatts or a gigawatt will have to be built elsewhere and piped in via transmission lines. That means offshore wind, solar (ideally with battery storage), and maybe one day nuclear power.
To the extent New York City can build solar and storage locally, it means dealing with a thicket of building regulations and local opposition. Efforts to shut down or replace peaker plants in the city have run into a brick wall at the New York Independent System Operator, which has declared that at least some peakers will have to stay online through the end of the decade to maintain system-wide reliability.
The only other new source of carbon-free power currently under construction is the offshore wind project Empire Wind, due to come online in 2027. NYISO said last year that without CHPE, Empire, and two local transmission projects planned to enter service by 2030, New York City would be “deficient in the summer” through 2030.
Of course developers have scrapped several other offshore wind projects over the years, whether due to problems procuring the right size turbine or the Trump administration buying out their lease. And though New York Governor Kathy Hochul pledged last summer to develop at least a gigawatt of new nuclear capacity in the northern region of the state, that is probably a decade away from fruition.
Meanwhile the Clean Path transmission line, which was meant to connect New York City to several gigawatts of new wind, solar and hydropower, saw its contracts canceled in late 2024 as its projected costs continued to rise. Last year, utility regulators shut down an effort by the state-run New York Power Authority to take it over as a “priority transmission project,” questioning whether it was “needed expeditiously” to meet downstate reliability needs and arguing that the project “will not be needed to serve substantial amounts of generation until well after 2033, and possibly not until 2040.”
While the city has some utility-scale battery storage systems, would-be developers have faced intense local opposition. Fullmark Energy, for instance, scrapped a planned 650-megawatt storage project after protests from political figures, including frequent mayoral candidate Curtis Sliwa. A dispute over another battery storage project in Queens has escalated into accusations of assault leveled by Councilmember Phil Wong, who called for a criminal investigation into what he said was an assault by a contractor for a project against his staffer.
So what’s left for New York City to do?
Any near-term progress will likely come from increasing efficiency and adding marginal generation capacity, as opposed to large-scale new projects and decommissioning of power plants.
“We need to max out our energy efficiency gains from Local Law 97,” former New York City Chief Climate Policy Advisor Daniel Zarelli told me, referring to a 2019 law mandating steep reductions in emissions from large buildings in the city, which came into effect two years ago. He also called for a further“push on batteries and behind the meter solar, clean energy, and energy efficiency.”
Already across the state, behind-the-meter solar is shaving off peak power demand. On the afternoon of July 2, behind-the-meter solar accounted served about 4.5 gigawatts to users, according to NYISO and Grid Status data.
Going forward, Zarelli said, the city should use its purchasing and planning power — as it did with CHPE — for projects like resurrecting Clean Path. “We need to be starting now. Maybe it’s not by 2030, but soon after we could be getting the benefit of that.”
“Battery developers started to see interconnection costs that were around 30 or 40 times what is standard,” Patrick Robbins, director of the Utility Customers Association told me. “It just means that new battery projects completely don’t pencil out and so we have a de facto moratorium on new [battery] projects.”
Advocates for solar and storage have blamed Con Edison for the city’s slow progress there, claiming that changes in the interconnection process have made it essentially cost prohibitive for battery storage developers to move forward on new projects.
Some of these fights have landed in front of New York’s Public Service Commission. In a filing, the city cited data from Con Edison showing that “the interconnection costs for some projects … have increased by thousands of percent,” citing one project whose interconnection costs jumped from $640,000 to over $35 million due to changes in how Con Edison attributed grid costs from new projects.
"Battery storage is essential to New York's clean energy future, and Con Edison strongly supports the development of energy storage when projects are deployed at the right locations, at the appropriate scale, and with operating parameters that provide the greatest benefit to customers and the electric grid,” a Con Edison spokesperson told me. “Because grid constraints vary across our system — from neighborhood‑level distribution lines to major transmission corridors — the location of a battery ultimately determines how much benefit it can deliver to the grid and to customers.”
There were 115 megawatts of battery storage operational in New York City at the end of last year, according to Con Edison, and 865 megawatts of projects with interconnection agreements. Peak load in the region is about 10,000 megawatts, meaning that these new projects would meaningfully alter the way the utility serves its customers.
Con Edison has claimed in a regulatory filing that the concentration of projects could lead to “significant impacts from BESS charging on infrastructure upstream of primary feeders,” necessitating the changes to its interconnection process. The city claimed in its filing that the added cost has “understandably chilled ongoing development activity at a time when New York City needs more supply resources capable of serving peak demand.”
When I reached out to the Mayor’s Office of Climate & Environmental Justice about the dispute, I received a statement in return from New York City Chief Climate Officer Louise Yeung: “Expanding battery storage capacity will be critical to New York City’s clean energy future, as extreme climate events continue to strain our grid system,” she said. “The City is working across agencies and communities to ensure battery energy storage projects are deployed safely and can provide reliable power when New Yorkers need it most.”
As for residential solar and storage, it will likely take years for those distributed resources to become a regular part of New York City’s energy landscape. There’s only one fully permitted and approved residential storage system allowed in New York City, which was installed earlier this year by Brooklyn Solar Works. Negotiating approvals with city agencies including the Department of Buildings and the New York City Fire Department took around six years, the company’s vice president of sales, Steve Nelson, told me.
“It’s New York City. We’re expecting there to be some level of bureaucracy and some lift to get that stuff approved,” Nelson said. “But what we also lack is a ready, readily accessible residential battery that meets the criteria that these departments have set.”
All that adds up to both a practical and a political gap for decarbonization, Zarelli told me.
“Batteries are a great way to connect the climate agenda and the affordability agenda, and it’s in the mayor’s control — it’s the regulatory apparatus at FDNY,” he said. “That’s a big near-term play that I think would make a big difference.”
Earlier this year, New York City Councilmember James Gennaro introduced a bill to amend the fire code to relax some battery storage permitting and safety requirements. But that still leaves the city’s decarbonization advocates with many big fish to fry.
“It’s a challenging future that’s still out in front of us, and how to navigate that is really difficult. But it’d be good if we were actually aligned on what our goals were as a society,” Zarelli said.
Rates were up 17% year over year in June, according to the latest Electricity Price Hub update, with another increase on the way.
With higher temperatures come higher electricity bills. Whether through higher seasonal charges or greater usage, Americans across the country were paying more for electricity in June.
In Virginia, the epicenter of the data center boom, the typical household electricity bill was $192 in June, up from $172 in June of last year, according to the latest data from the Heatmap and MIT’s Electricity Price Hub. Rates, meanwhile, were about 18 cents per kilowatt-hour, compared to just over 15 cents in June of last year, a 12% hike. Rates were also up from the end of last year, when they were about 15.5 cents.
The rate increase is largely due to prices set by Virginia’s largest utility, Dominion. Its rates are up 8% so far this year, according to MIT researchers, and 17% over the past 12 months, the result of a base rate increase that took effect at the beginning of the year. The average base rate alone is up 7.5% year over year for the average Dominion customer.
But that’s not all: The fuel portion of the bill is rising $8 a month for the typical customer, Dominion said according to local media reports, as a result of rising costs. The fuel charge went into effect at the beginning of July. Already, Dominion customers are paying about $78 per month for the generation portion of their electricity bill, according to Heatmap-MIT data.
The price hike will likely increase pressure on Dominion as it seeks to sell itself to Florida utility and energy developer NextEra in a $67 billion deal announced in May.
Earlier this week, Virginia's lieutenant governor Ghazala Hashmi sent a detailed letter to the State Corporation Commission, Virginia’s utility regulator, with 64 questions about the proposed merger. She said the deal “carries unprecedented implications for Virginia’s consumers and regulatory landscape.”
Hashmi asked regulators to extend their review of the deal beyond the six-month period mandated by its utility regulations, writing that “forcing this process into the six-month timeline will render an already inadequate period completely unworkable.”
In May, when the deal was announced, NextEra said it would provide over $2 billion of bill credits over two years to Dominion customers in Virginia, North Carolina, and South Carolina, which Dominion executives estimated would add up to $10 per month over the two years.