By Krysta Biniek, Kimberly Henderson, Matt Rogers, and Gregory Santoni
Growing concerns about climate change are intensifying interest in advanced technologies to reduce emissions in hard-to-abate sectors, such as cement, and also to draw down CO2 levels in the atmosphere. High on the list is carbon capture, use, and storage (CCUS), the term for a family of technologies and techniques that do exactly what they say: they capture CO2 and use or store it to prevent its release into the atmosphere. Through direct air capture (DAC) or bioenergy with carbon capture and storage (BECCS), CCUS can actually draw down CO2 concentrations in the atmosphere—“negative emissions,” as this is called. In some cases, that CO2 can be used to create products ranging from cement to synthetic fuels.
To better understand the possible role of CCUS, we looked at current technologies, reviewed current developments that could accelerate CCUS adoption, and assessed the economics of a range of use and storage scenarios. The short- to medium-term technical potential for CCUS is significant (Exhibit 1). CCUS doesn’t diminish the need to continue reducing CO2 emissions in other ways—for instance, by using more renewable energy, such as wind and solar power. But it offers considerable potential for reducing emissions in particularly hard-to-abate sectors, such as cement and steel production. What’s more, CCUS, along with natural carbon capture achieved through reforestation, would be a necessary step on the pathway to limiting warming to 1.5 degrees Celsius above preindustrial levels.
Exhibit 1
However, to reach CCUS’s potential, commercial-scale1 projects must become economically viable. In the short to medium term, CCUS could continue to struggle unless three important conditions are met: (1) capture costs fall, (2) regulatory frameworks provide incentives to account for CCUS costs, and (3) technology and innovation make CO2 a valuable feedstock for existing or new products. This article surveys the state of a portfolio of CCUS technologies, the underlying economics, and the changes needed to accelerate progress.
The value chain of carbon capture, use, and storage
The potential of CCUS can be tracked along an intuitive value chain. Many industrial processes generate CO2, most prominently when hydrocarbons are burned to generate power, but also less obviously—for example, when limestone is heated to produce cement. Driving your car or heating your home also releases CO2. Carbon dioxide can be captured at the source of the emissions, such as power plants or refineries, or even from the air itself.
A range of technologies—some using membranes, others using solvents—can perform the capture step of the process. Once captured, concentrated CO2 can be transported (most economically by pipeline) to places where it can be used as an input—for example, cured in concrete or as a feedstock to make synthetic jet fuel—or simply stored underground.
While these options all help stabilize levels of CO2 in the atmosphere, the challenge is economics. Storage would seem the obvious choice, as the geologic-storage-reservoir potential is vast, and the technology involved is mature. But storing CO2 at scale is a pure cost, and related investments have (understandably) been limited, given the absence of regulatory incentives to defray the installation of capture technology and a storage infrastructure. There are also tricky legal issues, such as liability for potential leaks and the jurisdictional complexities associated with underground property use.
The economics of CCUS
To clarify these dynamics, we modeled the expected alternative CO2 uses in 2030—from the already proven technologies, such as enhanced oil recovery (EOR), to more speculative ones, such as CO2-derived substitutes for carbon fiber. We also included an estimate for CO2 storage.
From now to 2030, our research and modeling suggest, CCUS could expand from 50 million tons of CO2 abatement per year (Mtpa) today, mostly for enhanced oil recovery and beverage carbonation,2 to at least 500 Mtpa (0.5 gigatons a year, or Gtpa)—just over 1 percent of today’s annual emissions (41 Gtpa). Such an expansion would be possible only with a supportive regulatory environment. Exhibit 2 offers a view of where the economic payoff is close and where more incentives would be needed to enable CCUS technologies to scale and reach their full potential. (For additional background on the relationship between CCUS and climate-abatement potential, see sidebar, “For further reading.”)
Exhibit 2
Despite the challenging economics, there is a wave of creative energy gathering around a number of CCUS bets.
Today’s leader: Enhanced oil recovery
Among CO2 uses by industry, enhanced oil recovery leads the field. It accounts for around 90 percent of all CO2 usage today (mostly in the United States)3 and benefits from a clear business case with associated revenues. Typical recovery processes leave anywhere from 40 to more than 80 percent of oil unrecovered, depending on factors such as reservoir depth, porosity, and type of oil. In some cases, the additional oil recovered is substantial (5 to more than 15 percent), and, if a nearby industrial source of CO2 can be found (say, a power plant or refinery), the use of emitted CO2 could be economically attractive. Our model estimates that by 2030, CO2 usage for EOR could account for more than 80 Mtpa4 of CO2 annually across conventional reservoirs, residual oil zones (ROZ), and unconventional oil fields5 —an enabling step along the journey to reduced emissions through CCUS.
Cementing in CO2 for the ages
New processes could lock up CO2 permanently in concrete, “storing” CO2 in buildings, sidewalks, or anywhere else concrete is used. This could represent a significant decarbonization opportunity (see “Laying the foundation for zero-carbon cement.”) For example, consider precast structural concrete slabs and blocks. They could potentially be made with new types of cement that, when cured in a CO2-rich environment, produce concrete that is around 25 percent CO2 by weight. There’s a CO2 bonus available here as well: cement used in this curing process has a lower limestone content. That’s significant, since baking limestone (calcination) to make conventional Portland cement releases around 7 percent of all industrial CO2 emissions globally. A second concrete process involves combining the aggregates with cement to make concrete (think cement mixers). Synthetic CO2-absorbing aggregates (combining industrial waste and carbon curing) can be formed to produce this type of concrete, which is 44 percent CO2 by weight. We estimate that by 2030, new concrete formulations could use at least 150 Mtpa of CO2.
Carbon-neutral fuels for jets and more
Technically, CO2 could be used to create virtually any type of fuel. Through a chemical reaction, CO2 captured from industry can be combined with hydrogen to create synthetic gasoline, jet fuel, and diesel. The key would be to produce ample amounts of hydrogen sustainably. One segment keen on seeing synthetics take off is the aviation industry, which consumes a lot of fuel and whose airborne emissions are otherwise hard to abate. By 2030, we estimate, this technology could abate roughly 15 Mtpa of CO2.
Turning the dial negative?
Other interesting applications seem further out. While several are novel enough to be worth keeping an eye on, their abatement potential is often uncertain. Estimating their cost and scalability is also difficult.
Capturing CO2 from ambient air—anywhere
Direct air capture (DAC) could push CO2 emissions into negative territory in a big way. DAC does exactly what it suggests—capture CO2 directly from the atmosphere, where it exists in very small ambient concentrations (400 parts per million, or 0.04 percent by volume). It has been put there in a variety of ways, including both industrial point sources and more diffuse emissions, such as those from vehicles, airplanes, ships, buildings, and agriculture. DAC facilities could be located at storage or industrial-use locations, bypassing the need for an expensive CO2-pipeline infrastructure. The challenge is that it takes a lot of energy—and money—to capture CO2 at very low atmospheric concentrations. Costs are high, running more than $500 per ton of CO2 captured—five to ten times the cost of capturing CO2 from industrial or power-plant sources. There are plans to scale this technology and reduce unit costs substantially, but the pathway to competitive economics remains unclear.
The biomass-energy cycle: CO2 neutral or even negative
Bioenergy with carbon capture and storage relies on nature to remove CO2 from the atmosphere for use elsewhere. Using sustainably harvested wood as a fuel renders the combustion process carbon neutral. (Other CO2-rich biomass sources, such as algae, could be harvested, as well.) Biomass fuel combustion could become carbon negative if the resulting CO2 emissions were then stored underground or used as inputs for industrial products, such as concrete and synthetic fuel. The degree to which BECCS can yield negative emissions, however, depends on a number of intermediate factors across the life cycle. These factors include how the biomass is grown, transported, and processed—all of which may “leak” CO2. (For more on the role of forests in sequestering CO2, see “Climate math, what a 1.5-degree pathway would take.”)
Next horizons
Three other opportunities to capture and use carbon—in carbon fiber, plastics, and agricultural “biochar”—are also worth watching.
Carbon fiber
Superstrong, superlight carbon fiber is used to make products from airplane wings to wind-turbine blades, and its market is booming. The price of the component carbon is high ($20,000 a ton), so manufacturers would love to have a cheaper, CO2-derived substitute. Moreover, the volume of CO2 used could become significant if cost-effective carbon fiber could be used widely to reinforce building materials. A number of pilot projects in the works focus on cracking the tough chemistry involved, but a commercially viable process appears to be perhaps a decade or more away. By 2030, we believe, the contribution to CO2 abatement would be 0.1 Mtpa of CO2.
Storing carbon in your mattress?
CO2 could substitute for fossil fuel–based inputs in plastics production. The combination of technical feasibility and high interest from environmentally aware consumers has attracted the attention of major chemical companies, which are testing a range of CO2-based plastics for widespread use. Green polyurethane—used in products such as textiles, flooring for sports centers, and, yes, mattresses—is in the early stages of commercial rollout. Storing carbon in green plastics would sequester it indefinitely. By 2030, we estimate, plastics could abate a modest but growing 10 Mtpa of CO2.
Biochar, anyone?
Farms produce enormous amounts of biomass waste. When this is heated in an oxygen-poor environment, it creates what’s called “biochar”—a charcoal-like soil amendment that today is used by a modest number of small farmers and gardeners, mostly in the United States. Producing biochar captures 50 percent of the CO2 that would otherwise escape during waste decomposition—and retains most of it for up to 100 years. We estimate that biochar technology is more than a decade away from the point when it could start having a real impact: by 2030, it could sequester roughly 2 Mtpa of CO2.
The road ahead: Obstacles and enablers
Moving toward an economy where CCUS plays a meaningful role would require overcoming challenges across three areas of the value chain, as well as changes in the regulatory environment to expand incentives.
Capture
About half of CO2 emissions are generated by factories, refineries, power plants, and the like. Some emissions, such as those from ethanol plants, are purer than others and can be captured relatively cheaply, for around $25 to $30 a ton. For less pure sources (such as emissions from cement and steel-making facilities or coal and natural-gas power plants), the costs get steeper, ranging from $60 to more than $150 a ton.6 What remains, of course, is the other half of CO2 emissions—widely dispersed or mobile. A look at four tiers of CO2 sources in the United States offers a perspective on the challenges of scaling CO2 capture (Exhibit 3).
Exhibit 3
CO2 transportation
Today, CO2 transportation—a necessity for CCUS to scale—is a weak link in the value chain. In the United States, some 5,000 miles of pipeline transport CO2, compared with 300,000 miles of natural-gas pipelines. Outside the United States, pipelines for moving CO2 are rare.
Storage
The challenges for CO2 storage are primarily nontechnical—a function of economic, legal, and regulatory challenges. By some estimates, the United States could geologically store 500 years of its current rate of CO2 emissions; globally, the number is around 300 years. This potential is constrained by the fact that carbon storage (without use) is largely a cost, as we have noted, and thus attracts relatively little project investment and innovation, particularly in the absence of regulatory support or incentives. Moreover, there are also complex legal issues that must be resolved, such as liability for potential leaks, as well as the jurisdictional complexities associated with underground property ownership and use. Still, by 2030 we estimate that storage could account for 200 Mtpa of CO2 abatement—a small but meaningful slice of the full potential for storage.
Regulation
Anywhere you look in the CCUS value chain, projects to jump-start progress are costly. One avenue of government support is tax credits. In the United States, a tax credit (Internal Revenue Code, Section 45Q) offers $35 a ton for CO2 use and $50 a ton for geologic storage (the higher incentive accounts for the lack of revenue potential). An alternative would be a market price for carbon.
In some sense, the CCUS opportunity is a natural extension of something that occurs every day in the global economy: the collection and disposal of waste and the transformation of some of it into higher-value products and materials. For a wide variety of players in the oil, gas, and chemical industries, this also represents a natural extension of core capabilities—such as operating pipelines, managing reservoirs, and synthesizing new materials—and could therefore be a major opportunity. To make the economics work and to encourage further technological innovation, incentives and supportive regulatory frameworks will be necessary. If they come, CCUS can help support the transition to a low-carbon economy. Without CCUS, the transition would become much more challenging—because every scenario to stabilize the climate depends on investment in negative-emissions technologies.
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