With every passing second, vast amounts of human-produced CO2 billows into the atmosphere. Collectively, we generate nearly 40 gigatons (Gt) annually, mainly by burning fossil fuels for energy, electricity and transportation.
Studies show if emissions continue at current levels, the window for avoiding dangerous warming will rapidly diminish. In that sense, countries are in a race against time — and one technology is being touted as indispensable to prevent "runaway" climate change: Carbon Capture and Sequestration (CCS).
"We talk about having no silver bullet on climate change but having silver buckshot," said US Democratic Party lawmaker Sheldon Whitehouse, one of the most dedicated environmental champions in the Senate. "And one of the pellets in the silver buckshot has to be really aggressive work on carbon capture."
Twenty-six utility-scale CCS projects are operating worldwide, with a combined capacity to capture and store some 40 million tons of carbon per year. The CO2 is either piped into deep geologic formations or injected into depleting oil and gas reservoirs. According to the Global CCS Institute, an international organization dedicated to promoting the technology, more than 40 other projects are under construction or in advanced planning stages on nearly every continent.
The International Energy Agency's (IEA's) recent headline-grabbing "Net Zero by 2050" report, designated CCS as one of seven pillars needed to achieve mid-century climate neutrality and limit global heating. Echoing previous analyses, it states that as we rapidly expand emissions-free renewable energy systems, we must construct thousands of CCS plants worldwide with the eventual capacity to bury more than 3 Gt to 7 Gt of CO2 annually — akin to running today's global fossil fuel industry in reverse.
But experts like Michael Mann, director of the Earth System Science Center at Pennsylvania State University and author of the book "The New Climate War," fear that leaning so heavily on CCS will "just prolong our collective dependency on fossil fuels to the advantage of the fossil fuel industry and to our collective detriment."
Using CO2 to produce more oil
For decades, CCS has been the oil and gas industry's favored environmental solution. Emerging out of former US President George W. Bush's "clean coal" initiative in the 2000s, advocates argued that fossil fuels could be cleaned up by retrofitting power plants with capture technologies to grab what's spewing from their stacks and bury it.
However, over 80% of existing CCS facilities use their captured and stored CO2 to produce oil. Instead of threatening the oil major's business model, CCS enables them to "have their cake and eat it too," said Mann in an email exchange with DW.
After decades of development, most oil fields still hold huge petroleum resources. They're just difficult to reach. To get to these challenging deposits, US oil giant Exxon began pioneering CO2 injection techniques in the 70s.
Several things happen when you inject CO2 into oil deposits, explained Manika Prasad, professor of the Geophysics Department and director of the Center for Rock and Fluid Multiphysics at the Colorado School of Mines: "The oil starts to swell, it increases in volume, and it decreases in viscosity."
Storing it in depleted reservoirs "increases the pressure" and drives the oil closer to the surface, enabling more production, said Prasad. At the same time, most of the injected carbon stays trapped, replacing the oil that was there.
The practice, known as CCS and enhanced oil recovery (EOR), is used across the oil and gas industry. ExxonMobil, for example, sequesters over 9 million tons of CO2 into deep saline aquifers and its oil and gas wells each year. Exxon says it has captured more than 120 million tons of CO2 over the last few decades, placing it firmly at the forefront of CCS.
But the origin of the CO2 is key. Lost in the details is that most of the carbon used by oil and gas majors in EOR operations comes from naturally occurring reservoirs and not human-produced sources. In other words, companies are using carbon that was already "sequestered." In the US, more than 70% of CO2 used for EOR is mined, not removed from the atmosphere, according to a 2019 IEA briefing.
"Using natural sources clearly provides no benefit in terms of the emissions intensity of the produced oil," writes the organization.
Though it varies by field, each half-ton of CO2 injected through EOR can squeeze another barrel or more of oil out of the Earth. As carbon is costly, companies usually try using it sparingly and tend to minimize the amount they inject into an oil well, so ultimately the emissions from a barrel of oil recovered in this manner can outweigh what was sequestered.
DW reached out to Exxon for a comment but had not received a response as of the date of publication.
Questionable climate math
Vicki Hollub, CEO of Occidental Petroleum, a global oil, gas and chemicals producer, is among her industry's most vocal CCS proponents. In a March forum hosted by New York's Columbia University, Hollub promised to lead the company to net-zero by 2050 through investing in regional carbon capture hubs piping CO2 directly into their oil reservoirs.
This "will enable us to get more reserves out but at a reduced level of emissions… [helping Occidental] to protect the environment and climate," said Hollub.
Hollub added that recently extended US government tax breaks lowering the cost of carbon that could then be used to increase production of oil, "which adds value to our shareholders."
But as the climate crisis becomes a climate emergency, the industry's embrace of EOR to produce "carbon-negative" oil spotlights some of the long-standing concerns about CCS' deployment.
Even though a portion of injected CO2 does remain trapped in oil reservoirs, the math around net-zero "can be very tricky," said Laura Singer, Program Manager for the Colorado School of Mines Payne Center.
"There's lots of wiggle room throughout these end-of-production scenarios," added Singer. Calculations only focus on the burning of the oil retrieved and do not consider all of the other emissions from production to transport. Once that's added in, "you have a different statement," she said.
Treating the symptoms
In February, ExxonMobil launched its new Low Carbon Solutions strategy, promising to spend 5% of its budget on CCS projects between 2021 and 2025. Still, Domien Vangenechten, a policy advisor at the climate think tank E3G, said there is general skepticism about the oil and gas sectors' seriousness about tackling its emissions.
"In 2019, CCS and renewables together accounted for just 0.9% of total capital expenditure across the oil and gas industry," said Vangenechten.
Vangenechten added CCS could be useful to mitigate emissions from hard-to-decarbonize industries like cement, concrete, chemicals and steel, which are together responsible for about 12% of global CO2 — but only if those emissions are stored geologically.
"We see a very limited role for CCS in the power sector, while it can play a role in heavy industry sectors in particular cement where fewer feasible alternatives exist," said Vangenechten.
In and of itself, carbon capture and storage, particularly when CO2 is used for oil recovery, "is not a solution to climate change," said geophysics professor Manika Prasad.
"We are only treating the symptoms with CCS if we don't address the problem at the source: which is that we shouldn't be producing so much CO2," she said.