DURHAM, N.C. – Geoengineering, the intentional manipulation of Earth’s climate to offset the warming from greenhouse gas emissions, is fraught with risks.
But research in three areas could lead to the greatest climate benefits with the smallest risk of unintentional environmental harm, according to an article by a pair of 91 researchers in the current issue of the journal Issues in Science and Technology.
“Our approach involves extending the concept of ecological restoration to the atmosphere, with the goal of returning it to its preindustrial condition,” Robert B. Jackson and James Salzman write. “Based on this idea, which we call atmospheric restoration, we recommend three types of geoengineering for fast-track research support.”
The three types are: forest preservation and restoration, industrial carbon removal, and bioenergy with carbon capture and storage.
Forest preservation and restoration provides the most immediate opportunity, Jackson and Salzman note. Plants provide one of the oldest and most efficient ways to remove carbon dioxide from Earth’s atmosphere.
An important policy incentive to promote this approach is Reduced Emissions from Deforestation and Forest Degradation (REDD), which was featured prominently in the 2009 Copenhagen climate talks. Tropical deforestation releases about 5 billion tons of carbon dioxide into the atmosphere each year, or roughly one-sixth the amount from fossil fuel emissions. REDD creates a financial value for the carbon stored in forests, offering incentives for developing countries to reduce emissions from forested lands and invest in low-carbon paths to sustainable development.
The benefits of providing financial incentives such as REDD to stem carbon loss from forests would extend far beyond climate, Jackson and Salzman note. It would also help slow erosion, improve water quality and flow, and preserve biodiversity. Accounting and monitoring protocols to measure the effectiveness of REDD still need work, however.
While forest preservation and restoration uses existing technologies and presents an immediate opportunity, the other two approaches – industrial carbon removal, and bioenergy with carbon capture and storage – still need extensive research to make them effective and to reduce their costs, the Duke duo write. Because these approaches require technological advances and a distributed network of facilities, they may take decades to scale up to a level that lowers atmospheric carbon dioxide concentrations substantially.
“Imagine a series of power plants run in reverse,” Jackson and Salzman write, to describe the benefits of industrial carbon removal. “The facilities use renewable energy to drive a chemical reaction that removes carbon dioxide from the atmosphere and regenerates the chemical used in the reaction. It’s as simple as that.”
What isn’t simple about the process, however, is its cost. Current amine-based technologies or next-generation chilled-ammonia chemistry for capturing carbon dioxide from power plant smoke stacks are too expensive to be widely used today. Costs for piping the captured carbon dioxide into underground storage sites also remain prohibitive. “We need immediate research incentives to reduce these costs, ideally by at least two-thirds,” Jackson and Salzman write.
The third technology – bioenergy with carbon capture and storage – fuses aspects of the first two. It uses plants as a cheap way to capture atmospheric carbon dioxide, which is then stored underground. The trees, grasses and other plants used to capture the carbon dioxide are harvested to supply the biomass energy needed to fuel the entire process. The sticking point, Jackson and Salzman note, is that harvesting enough biomass to fuel this approach on a broad scale would affect millions of acres of land – possibly putting it at odds with other critical needs, such as food production, or forest preservation and restoration.
“The scale of the problem…(and) the enormous potential footprint of bioenergy is what makes our third option the riskiest in terms of environmental effects,” the researchers acknowledge. “What (this approach) provides is an extensive, likely cheaper complement to industrial carbon removal. Neither approach is perfect. Both will eventually be needed to drawn down the concentration of carbon dioxide in the atmosphere, because energy efficiency and renewable alone can’t get us to a carbon-negative economy.”
“What these approaches have in common,” Jackson says, “is the ability to move greenhouse gas budgets in the atmosphere back towards their pre-industrial levels. Long term, restoring the atmosphere should be our ultimate goal.”
Jackson is Nicholas Professor of Global Environmental Change and professor of biology at Duke. He is widely cited for his research on feedbacks between people and the biosphere, including studies of the global carbon and water cycles, biosphere/atmosphere interactions, and global change.
Salzman is Duke’s Samuel F. Mordecai Professor of Law and Nicholas Institute Professor of Environmental Policy. He is an expert on U.S. and international environmental law, with strong interest in legal and institutional issues surrounding provision of ecosystem services.
Issues in Science and Technology is published by the National Academy of Sciences, National Academy of Engineering, Institute of Medicine and the University of Texas at Dallas.
