Why carbon dioxide removal is key to achieving aggressive climate goals
The release of the most recent United Nations Intergovernmental Panel on Climate Change (IPCC) report last August triggered an avalanche of alarming headlines. Many news outlets chose to highlight UN Secretary-General António Guterres’ description of the report’s findings as a “code red for humanity.”
While this study explored potential future climate change, previous IPCC research outlined a range of possible emissions pathways to limit average global warming to well below 2°C above preindustrial levels, the long-term goal articulated by the 2015 Paris Climate Accords. Two common features shared by all the pathways are rapid emissions reduction and carbon dioxide removal from the atmosphere. Put simply, carbon dioxide removal (CDR) approaches, and technologies are likely essential.
“All analyzed pathways limiting warming to 1.5°C with no or limited overshoot use CDR to some extent to neutralize emissions from sources for which no mitigation measures have been identified and, in most cases, also to achieve net negative emissions to return global warming to 1.5°C following a peak,” the report’s authors wrote. “The longer the delay in reducing CO2 emissions towards zero, the larger the likelihood of exceeding 1.5°C, and the heavier the implied reliance on net negative emissions after mid-century to return warming to 1.5°C.”
EPRI has a long track record of research and modeling work to better understand a host of issues related to CDR, including the potential role and risks of individual approaches, their impact on warming, and the attainability of climate goals, as well as how CDR should be considered in utility planning decisions. Recent work has utilized EPRI’s MERGE model, which combines a wide variety of scenarios that include global temperature goals, CDR options, policies, and energy system impacts, to better understand opportunities, risks, and uncertainties associated with carbon dioxide removal.
One of the findings to come out of EPRI’s modeling work underscores the IPCC’s findings regarding the importance of CDR. “Not only does it look like carbon removal technologies are valuable in pursuing goals limiting warming to below 2 degrees Celsius,” said Steven Rose, a senior research economist, and technical executive at EPRI. “Our work shows that it is far more expensive and may be impossible to achieve these goals without CDR.” In fact, many models, including EPRI’s, are unable to produce solutions that limit warming to 1.5°C, or even 2°C, without CDR.
Even with highly successful decarbonization efforts across the economy, it will still be difficult and expensive to abate emissions from some sectors, including aviation, shipping, and certain heavy manufacturing processes. The ability to remove carbon from the atmosphere provides flexibility to transition more easily while new and cost-effective decarbonization approaches for those industries are developed.
Carbon Removal Approaches
Avenues that limit warming to below 1.5°C involve dramatic emissions reductions and likely removal of billions of tons of carbon dioxide each year by 2050. The most prominent CDR technologies include terrestrial strategies, bioenergy with carbon capture and storage (BECCS), and direct air capture (DAC).
Terrestrial strategies. Some of the most effective CDR strategies don’t require advanced technology development. Instead, they involve expanding forestland and improving agriculture and soil management practices to tap the natural world’s power to sequester more carbon. “The terrestrial strategies are available now. We can plant trees and restore deforested areas and change agricultural practices to store more carbon,” said Rose.
A study published in the journal Science pinpointed tree planting as one of the most potent and economical ways to address climate change. In their analysis, the report’s authors identified over 1.7 billion acres where trees would naturally grow without encroaching on existing cropland. The result would be the removal of two-thirds of all emissions related to human activities.
Besides being immediately available, tapping the capacity of trees to store carbon through photosynthesis also has the benefit of being relatively cheap, typically costing less than $50 per metric ton of carbon. Healthy forests also improve air and water quality, and storing carbon in soil can improve crop yields. There are, however, tradeoffs to be considered, particularly in how land-use choices impact other societal priorities. For example, afforestation could reduce the amount of farmland available to grow food.
Bioenergy with carbon capture and storage. Some of the same dynamics that make terrestrial strategies effective at removing carbon from the atmosphere are also at play with BECCS. Just as forests can sequester carbon via photosynthesis, BECCS can capture planet-warming emissions using plants, trees, and waste streams.
However, BECCS is a more complex process that involves producing energy with biomass while also capturing emissions before they can make it into the atmosphere. Those emissions are then stored underground or are used in products such as fuels, chemicals, and concrete. Calculating the carbon impact of BECCS is not easy. That’s because there are many uncertainties about the cost and performance of energy technologies, the supply of bioenergy feedstocks, and logistics. Little is known about these and other factors because there is scant experience with BECCS facilities. Other considerations also need to be weighed, including the effectiveness of the carbon capture technologies and, as with afforestation, replacement of agricultural land with crops grown for BECCS.
As is true of terrestrial CDR approaches, the potential of BECCS is heavily influenced by the policies used to incentivize and implement it. Besides producing power, BECCS can be used to produce hydrogen and liquid biofuels. In all cases, though, BECCS can involve land-use choices that could impact food production, greenhouse gas emissions, and other societal priorities. However, these environmental and social implications vary depending on the type of biomass used. Some biomass can be produced in a way that doesn’t involve much land displacement and leads to a net reduction in emissions; other sources of biomass require a significant amount of land and result in additional emissions. Ongoing research by EPRI is examining and quantifying these impacts.
Direct air capture. Like those for BECCS, technologies to directly remove carbon from the atmosphere are nascent. DAC utilizes a chemical process to remove carbon dioxide and relies on underground infrastructure to store it. “It basically catches the carbon out of the atmosphere, and once you’ve caught it, it goes into a pipeline where you can then inject it into the ground,” said Rose. “It takes those molecules and redirects them below ground for storage purposes or potential utilization.”
A great deal of research is being devoted to DAC today. While early research results indicate that DAC is technically feasible, the larger question about its viability revolves around economics. “There’s still a lot that needs to be understood in terms of the energy use of that technology. It’s very energy intensive, and if you are trying to modify your energy system for decarbonization, how do you ensure that you’re doing it in a compatible way?” said Rose.
Impact on Utility Planning and Investments
The findings of the CDR research and modeling work EPRI has done underscore the importance of removing carbon from the atmosphere as a way to achieve ambitious climate goals. If global emissions continue to rise, the importance of CDR will also increase.
“It’s more expensive to pursue the goals if you wait. And it is also potentially not just more expensive but impossible to get there,” said Rose. “If current upward trends in global emissions continue, it becomes more difficult to achieve the ambitious international goal, and CDR becomes even more important to the viability of that goal.”
One objective of EPRI’s work has been to evaluate how CDR may impact utility investment and planning decisions. For example, EPRI’s modeling work has examined how DAC and BECCS could affect utility revenues. “Those two CDR options represent revenue opportunities for the electric sector,” said Rose. “You can imagine a biopower with CCS plant being used to provide energy for a utility’s customers and receiving payments for carbon dioxide removal services.”
Because DAC is energy-intensive, it can also potentially increase electricity demand. Therefore, it represents an opportunity to harness surplus renewable generation and always-on nuclear power.
CDR could also impact planning if it allows a utility to continue operating a power plant that emits carbon dioxide during the transition to a low-carbon energy system. Continuing to operate such a plant could lower the overall cost of transitioning to a net-zero carbon energy system and provide a utility with more flexibility to move towards non-emitting generation.
Finally, understanding the potential role of CDR is important to fully grasp future utility risks and uncertainties. “It represents a potential revenue stream, but it also represents an uncertainty,” said Rose. “In addition to other uncertainties about load growth, fuel markets, low-carbon technology, and policy, it’s another uncertainty companies would want to evaluate as a potential decarbonization risk.”
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