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Scholars, industry leader spell out necessities and challenges of carbon removal

Removing carbon dioxide from the Earth’s atmosphere will be a crucial part of addressing climate change, but we must holistically assess technology and address tradeoffs, according to a recent panel hosted by Stanford University’s Global Energy Dialogues series.

The panel addressed carbon removal from three perspectives: industry, climate solutions and energy demand. The experts also discussed the need to work across sectors to develop optimal carbon removal strategies, while also urgently reducing emissions of greenhouse gases from fossil fuels. Carbon removal must not be seen as a magic bullet for not slashing human-caused emissions to near zero, they agreed.

“We have to continuously be thinking about things in parallel and not in sequence,” said Ajay Mehta, general manager of New Energies Research & Technology at Shell. “When we think about negative emission technologies, this is something that we have to start thinking about here and now, but not as a substitute for the need for deeper decarbonization.”

The world is already receiving a “giant subsidy from nature for our CO2 emissions,” said Chris Field, director of Stanford’s Woods Institute for the Environment. Most carbon emissions are absorbed by ocean and by land, he explained. About 45 percent of emissions stay in the atmosphere.

However, we cannot rely on natural processes alone. Warming from carbon dioxide in the air is essentially permanent, at least on a scale of thousands of years, said Field, who is also a professor of Earth system science and of biology. Because of this, our only option for preventing future emissions from heating the atmosphere, or even cooling the atmosphere, is carbon removal.

Addressing Tradeoffs

Natural climate solutions, which rely on plants absorbing carbon through photosynthesis, are an important part of the carbon removal picture, according to the panel. Natural solutions, like trees, grasses, shrubs and crops are cheap compared to engineered technologies. The downside is that they require a lot of land and nutrients.

Bioenergy with carbon capture and storage (BECCS) combines natural climate solutions with carbon capture storage. In a BECCS system, crops are planted to capture CO2 from the atmosphere before being harvested as biomass and burned for energy. The resulting carbon emissions are captured and stored underground. Such systems produce electricity with negative emissions.

But, for BECCS to have a major impact, we would potentially need to double the amount of land used for agriculture. In order to move forward, we’re going to have to better understand the impact on land use, because we need to avoid the “unintended consequence of greater conversion of wild lands,” said Sally Benson, Precourt Family Professor at Stanford in the Department of Energy Resources Engineering.

As for engineered solutions, removing CO2 from the air is more difficult than capturing it coming out of the smokestack at a power plant burning coal or natural gas, because the CO2 is much more concentrated out of the smokestack. The lower the CO2 concentration the more energy-intensive it is to remove.

“As long as we've got concentrated sources of CO2, I think it's preferable to go after those,” said Benson.

As we move forward with carbon removal, we can’t study solutions in isolation. Instead, “We really need to figure out what are those win-win-win solutions,” said Benson. “Winning for the people, winning for the economy and winning for the environment.”

Working across sectors

Shell is committed to becoming a net-zero carbon emissions business by 2050. Mehta recognizes carbon removal technologies as crucial to meeting this target. He sees a role for oil and gas companies as the carbon sequestration industry develops.

“We are not afraid of the energy transition. We actually want to thrive in it," Mehta said in response to a question from the session’s moderator, Arun Majumdar, who is director of Stanford’s Precourt Institute for Energy and a professor of mechanical engineering.

Public-private partnerships will be crucial to the development of carbon removal solutions, the panel said. Government has a role to play in fostering R&D and implementation, and the public and private sectors will need to “work hand in glove together” on carbon removal investment, said Mehta. He cited hydrogen as an area that needs a nudge from the government to encourage investment and infrastructure development.

On the academic side, Benson said she would like to see public-private partnerships that expedite  carbon removal research. She noted that multiple regulatory jurisdictions frequently oversee direct air capture projects, which can make permits challenging to get.

Climate urgency

A risk of carbon removal technologies, according to Field, is that they may provide a false hope that we can delay addressing climate change. Instead, we need to be reducing emissions directly while developing carbon removal technologies.

"We really need to work very hard to assure that that can-kicking ethic doesn’t take over,” said Field. “Finding the accelerator pedal on our portfolio of actions is super important.”

“We can’t let distant prospects for CO2 removal take away the focus on the urgency for action.”

Breakthrough Energy Venture’s Eric Toone and the Canada Pension Plan Investment Board’s Avik Dey will explore scaling innovations for a sustainable energy future at Global Energy Dialogues next session on Wednesday, October 14, at 9:15 am Pacific. All sessions are online, free and open to the public, with registration required at

The Global Energy Dialogues are funded by the Stanford Global Energy Forum.

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