Carbon Sequestration: The Geological and Biological Potential
To obtain the 2 degrees, and more so the 1.5-degree targets recommended by a recent IPCC report, requires deep decarbonization and significant decrease of anthropogenic emissions. However, it will probably be extremely expensive to decrease anthropogenic emissions once reaching low levels. As noted by a recent National Academies Press report, when deciding of the mitigation strategy, we should ask “which is least expensive and least disruptive in terms of land and other impacts—an emission reduction or an equivalent amount of negative emission? “[Page 4, NAP 2019]
Carbon sequestration can significantly reduce CO₂ emissions to the atmosphere and is essential to any climate mitigation scheme. In geologic carbon sequestration, usually, the CO₂ is pressurized until it becomes a liquid and then injected into porous rock formations in geologic basins. Other forms of carbon sequestration include biological carbon sequestration, which refers to the storage of atmospheric carbon in vegetation, soils, woody products, and aquatic environments.
While both methods have significant potential to reduce atmospheric carbon, each of these methods raises concerns. These include the potential for geological carbon sequestration to be costly and risky and for biological carbon sequestration to be temporary and difficult to quantify.
C-FARE has assembled a panel of experts to discuss the potential of geological and biological carbon sequestration, the need for policy incentives, and project paths to performance at scale.
This event started with Daniel Schrag’s presentation, which focused on geological sequestration. Schrag argued that carbon capture and sequestration (CCS) is an important part of dealing with climate change but that it is not yet widely deployed for a couple of reasons: (1) there is no comprehensive climate legislation in the US, (2) the shale-gas boom led cheap natural gas to dominate the power sector, (3) the cost of renewable energy such as wind and solar witnessed a significant decline, and (4) the collapse in the price of oil for extended periods during the last 15 years.
Quantitative, sector-specific modeling of a low carbon economy shows that CCS is almost certainly essential to achieve an ultra-low carbon economy. The biggest challenge may be dealing with emissions from large biorefineries (or mixed coal-biomass refineries). This is where CCS will be critical.
The presentation closes with policy context for carbon sequestration:
Permeance is critical.
Monitoring requirements and enforceability should be consistent, yet current enforcement is ambiguous.
Increasing carbon storage in forests and soils may be better accomplished by standards and norms, rather than monetization.
When assessing current state of negative emissions technologies with direct costs of less than $100/t CO₂, once scaled up these technologies can capture and store ~1 Gt/y CO₂ in the United States and ~10 Gt/y CO₂ globally. A substantial fraction of total emissions of ~6.5 Gt CO₂e in the United States and more than 50 Gt CO₂e globally. Key, however, to their wide deployment are the unprecedented rates of adoption. To this end, the potential of building on the concepts of the circular economy through biomass waste can lead to approximately 0.5 Gt/y CO₂ in the US and the 5 Gt/y CO₂ globally captured and sequestered through Bio-energy CCS (BECCS) [NAP 2019]. However, fueling exclusively these technologies with biomass waste would require the collection and delivery of all economically available agricultural, forestry, and municipal waste to a BECCS facility able to use the waste. Logistically challenging anywhere, especially in places with limited institutional capacity.
Next, Keith Paustian followed with a presentation titled “Agriculture, Soil carbon and Climate Mitigation – A Quick Overview”. While most people are more familiar with afforestation and reforestation to combat climate change, Paustian’s focus was on soil carbon. Agriculture and land use account for about 24% of global emissions, which is a large emission source. Past land use changes have contributed substantially to CO₂ additions in the atmosphere. There is a big carbon debt, and now the question is how we can manage our eco-systems to gain lost soil carbon.
There are a couple of different methods to do so through regenerative/conservation management practices. These practices have the capacity to ‘drawdown’ atmospheric CO₂, storing it as soil organic matter and substantially reduce non-CO₂ emissions from agriculture. There are a lot of co-benefits of rebuilding soil carbon stocks, including increased soil health, increased water quality and biodiversity, and greater climate resilience to name a few. However, to implement these changes, incentives are needed to help farmers ‘de-risk’ transitioning to more sustainable systems, that may have potential for increased profitability in the long-term. Guidance and extension support is also required, since improper applications can result in more harm (e.g., high levels of above ground harvesting of deep-rooted crops).
Biological carbon sequestration will require significant changes to land use and management practices such as afforestation/reforestation, changes in forest management, or drastic changes in agricultural practices that enhance soil carbon storage (“agricultural soils”). Many past programs to induce landowners to change forest, grazing, and cropland management were not successful.
When thinking of soil carbon sequestration, we achieve carbon dioxide removal and storage through management of terrestrial ecosystems. This method relies on the adoption of improved management practices that increase the amount of carbon stored as soil organic matter, either by increasing the rate of input of plant-derived residues to soils or by reducing rates of existing carbon stock turnover already in the soil. As noted by one of the questions asked by the audience, increasing soil organic matter substantially improves soil health and soil fertility. It is important to focus on the net flow direction of carbon in biological systems, while focusing on the role of carbon in restoring and augmenting our natural systems, including our agricultural ecologies.
However, policy is key, and governments should introduce the social price of carbon into markets. Once incentives are introduced, and the cost of emissions accounted for, the decision process guiding the energy, agricultural, and the production sectors will accommodate and identify of ways to reduce emissions.
Several factors are affecting the deployment of negative emissions technologies. From competition for land needed to feed the world, to environmental constraints and the flow and supply of water. Economics is a key barrier to the deployment of many of these technologies, especially in the absence of a price for carbon. We resist actions that appear to contradict out economic interests. In addition, as discussed above, permanence is a challenge, and monitoring and verifying is a critical component of any wide-scale deployment. Thus, suggesting governance is essential since overly lax oversight would lead to inefficient CO₂ removal. Major hiccups during the transition to decarbonize the economy will then lead to the public loosing confidence.
We should strive to deploy the least expensive and least disruptive technology, both in terms of land and water and in terms of other impacts. And then we will choose emission reduction or an equivalent amount of negative emission that will best fit our goals. Because it is very expensive to decrease anthropogenic emissions once they reach low levels, reducing or employing negative emissions are probably competitors.
This C-FARE’s webinar hosted Daniel Schrag (Sturgis Hooper Professor of Geology, Professor of Environmental Science and Engineering at Harvard University, and director of the Harvard University Center for the Environment) and Keith Paustian (University Distinguished Professor in the Department of Soil and Crop Sciences and Senior Research Scientist at the Natural Resource Ecology Laboratory at Colorado State University), with moderation by Gal Hochman (C-FARE's Board chair and the professor at Rutgers University), and Madhu Khanna (ACES Distinguished Professor at the University of Illinois Urbana-Champaign).
This program is supported in part by the Agricultural and Applied Economics Association and the US Department of Agriculture’s Economic Research Service, and the National Agricultural Statistics Service.
Those who register but cannot attend our webinar can always view a recording of it later at the council’s YouTube channel.