Non-energy Emissions from Industry

This page is about process emissions from industry. These are emissions that are direct byproducts of chemical transformations in industrial processes – not from the use of energy to power industrial processes. (We discuss energy use in industry on a separate page.)

The vast majority of industrial process emissions come from just two processes, hydrogen production and cement production.

Hydrogen

The world produces 90 million metric tons of hydrogen each year. Right now, the large majority of this is “grey” hydrogen, produced from fossil methane gas through steam methane reformation. (The “colors” of hydrogen refer to the way that it is made, not to the product itself. All hydrogen gas is the same.)  In this process, high temperature steam splits the carbon atoms from the hydrogen in methane (CH₄). The carbon atoms combine with oxygen to create carbon dioxide (CO₂), which is released into the atmosphere. Most hydrogen used today is grey because, until the war in Ukraine, methane gas was cheap, and so this has been the cheapest way to produce hydrogen in most parts of the world. (In some places, it is cheaper to produce it from coal or from petroleum, through even more polluting processes.)

The most straightforward way to produce hydrogen without CO₂ emissions is to use an electrolyzer to run an electric current through water (H₂O), splitting the hydrogen from the oxygen, producing pure hydrogen gas and pure oxygen. If zero-carbon electricity is used, then the entire process emits no GHGs. Until recently, this “green” hydrogen was five to six times more expensive than grey. However, that is changing quickly, for three reasons:

1. The main upfront (capital expenditure or “capex”) cost of producing green hydrogen is the cost of electrolyzers. This is a technology on a learning curve, which means that the cost per unit declines at a fixed rate with every doubling of capacity. Until recently, the market for hydrogen electrolyzers was small and growing slowly, so prices were decreasing slowly. But in the last two years, governments and companies around the world have announced massive investments in green hydrogen production – so that the market is now set to grow 6000% by 2031. This will drive the cost of electrolyzers down the learning curve at unprecedented speeds.
2. The main operating expenses (“opex”) for green hydrogen production is the cost of renewable electricity. This, too, is on a learning curve, and so its cost has been plummeting and will continue to do so. Moreover, because hydrogen can be stored, it can be generated with variable renewable energy, like wind and solar, at times when the supply of electricity is greater than demand, so that the electricity is close to free. This is the plan behind the ACES Delta project being built in Utah: green hydrogen will be produced with cheap, excess renewable electricity when it is available, and stored in giant underground salt caverns until it is needed.

⇒ Listen to this discussion of the ACES Delta project with Jigar Shah, director of the Department of Energy Loan Programs Office

3. The Russian invasion of Ukraine increased the price of methane dramatically in many parts of the world – and by a full 700% in Europe. The price has since come back down; but while it was high, hydrogen produced from methane was no longer a bargain. Even now that methane prices have come down, this episode was a powerful reminder that fossil fuel prices are volatile and unpredictable in a way that electricity from renewable sources is not.

Electrolysis is not the only possible way to make hydrogen with lower GHG emissions. One alternative is to produce hydrogen from methane with steam methane reformation, but then to capture most of the resulting CO₂ and pump it into geological formations where it can be permanently stored. (See our discussion of Carbon Capture, Utilization and Storage, or CCUS, in the page on Energy Use in Industry.) This process will never be zero-carbon, because uncombusted methane always leaks when it is extracted, compressed, and transported – and this “fugitive methane” is an extremely powerful greenhouse gas. The oil and gas industry has nonetheless heavily promoted so-called “blue” hydrogen made in this way as a lower-carbon bridge, until green hydrogen becomes affordable. However, when the war in Ukraine drove up the price of methane, it showed that the window of time in which hydrogen from methane is consistently the cheapest option has already begun to close. 

Another pathway, currently being developed by a startup called Monolith Materials, is methane pyrolysis. Renewable electricity is used to heat methane gas to a very high temperature in the absence of oxygen. The high temperature splits the hydrogen in the methane from the carbon. Because there is no oxygen present for the carbon to bond with, no CO₂ is formed; instead, the carbon becomes an inert solid called “carbon black,” which is a crucial component in tires, ink, and other products, and which is currently produced through a dirty, heavily polluting process. While upstream emissions of fugitive methane mean that this process is not as clean as green hydrogen, it is far cleaner than alternative ways of producing the 1.5 million tons of carbon black that the world uses each year. And in principle, the process could be carbon negative if enough biomethane (methane made by decaying organic matter) could be sourced to use as a feedstock, in place of fossil methane gas. In that case, the carbon atoms in the carbon black would come from biomethane that would otherwise have warmed the atmosphere. (There is not enough biomethane to substitute for fossil methane in most applications – but there could be enough to use in a few, hard-to-abate applications, like carbon-black production.)

⇒ Listen to this My Climate Journey podcast interview with Rob Hanson, co-founder of Monolith Materials

Here are some startups working on producing clean hydrogen:

Cement

Cement is the “glue” that holds concrete together. It is made by heating limestone to very high temperatures. This causes the calcium carbonate (CaCO₃) in limestone to split into solid calcium oxide (CaO), which is the main ingredient of cement, and carbon dioxide (CO₂), which is usually released into the atmosphere. Carbon dioxide produced in this way makes up about 60% of the emissions from cement manufacture. The other 40% come from burning fuels to produce heat, which we discuss in the page on Energy Use in Industry.

⇒ Here’s a great, general explainer on the problem of decarbonizing cement from CarbonBrief. It’s from 2018, so it doesn’t discuss some of the solutions that recent start-ups are trying

The most straightforward path to decarbonizing cement is to capture carbon dioxide emissions from the exhaust stream. One startup, Carbon Cure, aims to recycle these captured emissions and use them to harden or “cure” the concrete that is made from the cement. Alternatively, the captured carbon dioxide might be pumped into geological formations, where it can be permanently sequestered underground. As we discuss in the page on Energy Use in Industry, because carbon dioxide in heavily concentrated in the exhaust stream from cement manufacture, it lends itself more than many other industrial processes to such Carbon Capture, Utilization and Storage (CCUS).

Several startups are pursuing approaches that reimagine cement-making more radically. Canary Media profiles six of them in this article. Two of the most exciting approaches eliminate process emissions entirely, by substituting silicate rocks, which do not contain carbon, for the limestone used in conventional cement-making. One of these is Brimstone Energy

⇒Listen to this podcast interview with Cody Fink, co-founder of Brimstone Energy.

Sublime Systems goes even further. Like Brimstone, Sublime starts with silicate rocks, rather than limestone. But rather than cooking them at high temperatures, Sublime uses a low-temperature electrochemical process to separate calcium oxide from the rocks. (This is one example of an “electrify everything” approach – replacing high-temperature heat-based processes with electrochemical process – that startups are taking across a wide range of industrial sectors, from steel-making to fertilizer production. In each case, low-cost renewable electricity is unlocking possibilities that seemed entirely impractical a decade ago.)

⇒ Listen to this podcast interview with Leah Ellis, CEO of Sublime systems.

In March, 2024, the US Department of Energy awarded large grants to six startups pursuing different ways of decarbonizing cement – along with other grants, totaling $6 billion, to startups decarbonizing other parts of heavy industry.

The grants included $87 million to Sublime Systems and $189 million to Brimstone Energy, to help them finance the construction of factories to demonstrate their technologies at commercial scale. This is a huge boost to these technologies. Startups with promising new technologies often languish in a “valley of death,” because banks will not loan money to build first-of-a-kind factories.

⇒To get a sense of just how big a deal these grants are for industrial decarbonization, listen to or read the transcript of this Volts podcast with Rebecca Dell and Evan Gillespie.

The Biden-Harris administration, and some US states, are also supporting these technologies in another way. Governments use far more concrete than any anyone else. By instituting Buy Clean policies requiring low-carbon concrete for their own purchases, they are creating a market, so that when investors put money into building factories to make clean concrete, they can be sure in advance that they will have buyers. 

In this illuminating podcast from 2021, Rebecca Dell makes an important point about the cost of such policies. Depending on how it is made, low-carbon or zero-carbon cement might be twice as expensive as standard cement – and so concrete made with low-carbon cement might be twice as expensive as other concrete . That sounds like a lot — and for individual concrete makers, it is. But concrete cheap: the cost of concrete is typically less than 0.5% of the cost of a construction project. So, regulations that require low-carbon concrete (either for government purchases, or more broadly) add almost nothing to the cost of projects, even if they double the price of concrete used.

Here are some startups working on decarbonizing cement:

This is interesting and all… but I’m not going to work in the cement industry.
What other work needs to be done?

We need people to push for governments at all levels, and also businesses, and institutions like colleges and universities, to adopt Buy Clean policies – or to push for regulations simply requiring that all cement be low-carbon. These girls show how it’s done:

General

• Industrious Labs provides data, analysis, and policies to transform and decarbonize heavy industry across a wide variety of sub-sectors.
• Industry Decarbonization Newsletter provides useful coverage of the industrial sector (both energy and non-energy emissions).

Hydrogen

• Michael Liebreich, Keynote address, 2022 World Hydrogen Congress.
• International Energy Agency, Global Hydrogen Review 2023
• Michael Liebreich, “Separating Hype from Hydrogen – Part One: The Supply Side“
• Michael Liebreich, “Separating Hype from Hydrogen – Part Two: The Demand Side“
• Carbon Brief, “Does the World Need Hydrogen to Solve Climate Change?”
• Bloomberg, “A Green Energy Economy Depends on this Little-Known Machine”
• International Renewable Energy Agency, “Green Energy Cost Reduction: Scaling Up Hydrogen to meet the 1.5^oC Climate Goal”
• US Department of Energy, Clean Hydrogen Commercial Liftoff Report

Cement

• ClimateWorks report, Decarbonizing Concrete: Deep decarbonization pathways for the cement and concrete cycle in the United States, India, and China
• US Department of Energy, Industrial Decarbonization Commercial Liftoff Report
• IEA Cement
• Global Efficiency Intelligence Report, Deep Decarbonization Roadmap for the Cement and Concrete Industries in California
• Watari, Sao, Hata, and Nansai, “Efficient use of cement and concrete to reduce reliance on supply-side technologies for net-zero emissions”
• Adam Duckett, “Engineers push to make zero emissions steel and cement from a single process”