Can Trees, Oceans and Giant Carbon Sucking Machines Save Us from Climate Catastrophe?

July 8, 2019
Jason Leem/Unsplash
Angela Anderson
Director, Climate and Energy Program

The world needs leadership on climate change–as witnessed by the limited progress made by nearly 200 country delegates to the climate conference last week who failed to overcome Saudi Arabia’s block on formal discussion of the latest climate science produced by The Intergovernmental Panel on Climate Change (IPCC).  As we confront ever more obvious impacts of a warming world, we must immediately tackle the political and technical challenges of reducing the pollution causing climate change. And, just as actively, seek ways to remove, store and manage carbon to bring our climate back into balance.

Florida is perhaps the US state facing the most obvious evidence of a warming world. Sea level rise has already cost Florida taxpayers billions of dollars to keep the ocean at bay. And they are fighting a losing battle if we don’t act fast to move our economy off fossil fuels.

Democratic presidential hopefuls in the Miami debate spent more time than ever before addressing climate change, and many candidates indicate it will be a high priority. But without truly transformational change, Florida and the rest of this country are destined for a world of more dangerous storms, longer and hotter heat waves, wildfires, and floods threatening the health, homes, and economies of thousands of communities.

While moving to a clean energy economy and adaptation must be our first-line solutions to climate change, scientists are signaling that carbon dioxide removal will also need to be a part of our strategy.  Carbon dioxide removal (CDR), also known as negative emissions technologies (NETs), is a term used to describe a range of options to actively remove carbon dioxide (CO2) from the atmosphere.

The host nation for the next world climate conference, Chile, is planning to feature natural ways for trees and oceans to store carbon.  Meanwhile, Exxon and other oil companies, along with Bill Gates, are making news with investments in new technologies to draw CO2 out of the air.  It may well be that both types of approaches are needed to grapple with the climate crisis that is upon us.

What is carbon dioxide removal and why consider it?

A crucial insight from the recent IPCC 1.5° C report is that meeting the long-term goals of the Paris Agreement on climate change will require not just getting to zero emissions, but getting to “net negative” global CO2 emissions by mid-century.  Unfortunately, we are rapidly running out of time to avoid severe climate risks through deep cuts in emissions alone, and some sectors of our economy may find it difficult to stop using fossil fuels.

The report highlighted, in a more pointed way than had been done before, the need to invest in measures to protect communities from the impacts that are already unfolding and/or are unavoidable by helping them adapt.  At the same time, there are limits to adaptation, especially as we get closer to high-risk or irreversible climate impacts, like sea level rise.

In this daunting context, understanding the risks and potential of CDR will be essential for climate activists, scientists, the media, and lawmakers.

CO2 removal occurs naturally on land (e.g. forests, soils and wetlands) and the ocean (e.g. seagrasses, microalgae), and we can enhance that natural process to increase the amount of carbon stored.  More attention has been given lately to engineered, technological approaches, include capturing carbon from the air directly (Direct Air Capture or DAC) and storing it in secure geologic formations or converting it into fuel, cement, minerals, and plastics, or used as a feedstock for chemicals – all of which are at various stages of research and development.

The National Academy of Sciences released last year its analysis of the major CDR options, titled Negative Emissions Technologies and Reliable Sequestration: A Research Agenda.  Specifically, they looked at a number of natural and engineered approaches including:

  • Coastal blue carbon (Chapter 2)—Land use and management practices that increase the carbon stored in living plants or sediments in mangroves, tidal marshlands, seagrass beds, and other tidal or salt-water wetlands.
  • Terrestrial carbon removal and sequestration (Chapter 3)—Land use and management practices such as afforestation/reforestation, changes in forest management, or changes in agricultural practices that enhance soil carbon storage (“agricultural soils”).
  • Bioenergy with carbon capture and sequestration (Chapter 4)—Energy production using plant biomass to produce electricity, liquid fuels, and/or heat combined with capture and sequestration of any CO2 produced when using the bioenergy and any remaining biomass carbon that is not in the liquid fuels.
  • Direct air capture (Chapter 5)—Chemical processes that capture CO2 from ambient air and concentrate it, so that it can be injected into a storage reservoir.

A broad portfolio of negative emissions technologies are needed if we are to reach a goal of limiting global average temperature to well under 2°C. Coastal blue carbon, afforestation/reforestation and soil carbon are among the best options we have available today. Bioenergy with CCS, Direct Air Capture and Accelerated Weather are technologically based approaches that need varying levels of research to determine whether they can be safely and affordably deployed. Source: National Academies of Science

 Important considerations to help evaluate CDR options

CDR options must be evaluated on an individual basis as well as how they interact with each other (e.g. competition for the same land). Some are an enhancement of natural processes and others are more heavily reliant on technological solutions. While some of these options are well-understood and already being implemented, others are still at early stages of research and development. In addition to climate benefits, some of these options also have the potential to provide other valuable co-benefits—such as ecosystem benefits, flood protection, and more productive soils and forests—and might make sense to deploy for those reasons.

Many CDR options may, though, pose significant risks, costs and uncertainties. These include trade-offs in terms of use of scarce resources like land and water and the risks of a sudden release of CO2 from a failed repository. There are many challenges and issues raised by the different CDR approaches, including important questions of sustainability and equity (Dooley and Kartha 2018, Creutzig et al. 2013), that can be addressed broadly by asking three questions:

  • How much land does the approach require, and what kind of land is it? How permanent is land storage, in different ecosystems and at different depths, likely to be?
  • How much (external, non-photosynthetic) energy does the approach require?
  • How much matter (e.g. biomass, rock, or CO2) does the approach require to be transported, pyrolyzed, crushed, buried or otherwise processed, and what kind of processing, transportation and infrastructure are required?

Scenario of the role of negative emissions technologies in reaching net zero emissions. NOTE: For any concentration and type of greenhouse gas (e.g. methane, perfluorocarbons, and nitrous oxide) CO2e signifies the concentration of CO2 which would have the same amount of radiative forcing. Source: UNEP, 2017

It is very important to consider the equity and environmental justice impacts of CDR approaches, with particular attention to competition for land and pollution when evaluating CDR options.  Community groups are already overburdened with pollution from facilities like power plants, whether they are coal, natural gas or bioenergy.

While adding carbon capture technology to a bioenergy facility would reduce CO2 emissions, other pollution control technologies will be necessary to reduce other harmful air pollutants. And there are concerns about the demand these plants present for water and land and how their needs for those natural resources would affect the community that also relies on them.

In addition, the network of pipelines required to transport carbon to safe storage sites could encroach on indigenous people’s lands.  Similarly, even the natural solutions, like reforestation, can pose threats to the rights of indigenous peoples by commoditizing their homes and property.

A less technical and more common risk cited by many is the potential “moral hazard.” Could a focus on CDR give politicians and polluters yet another excuse for delaying action to rapidly reduce fossil fuel emissions and fund adaptation, in the hopes that we could engineer our way out of the climate crisis?

Some argue that CDR could endanger our transition to carbon-free energy options, possibly with drastic consequences, by diminishing both the investments for and the political pressure to eliminate high-carbon energy sources.  Or it could make the transition dependent on negative emissions from CDR approaches that may not pan out or that may have unforeseen risks for ecosystems or environmental justice.  Or it might lock the world in to overshoot scenarios (temporary increases of global average temperature over 1.5 or even 2 degrees) with potentially irreversible climate consequences.

What could a path forward for CDR entail?

The National Academy of Sciences report on carbon removal recommended that the US “launch a substantial research initiative to advance negative emissions technologies (NETs) as soon as practicable:”

A substantial investment would (1) improve existing NETs (i.e., coastal blue carbon, afforestation/reforestation, changes in forest management, uptake and storage by agricultural soils, and biomass energy with carbon capture and sequestration) to increase the capacity and to reduce their negative impacts and costs; (2) make rapid progress on direct air capture and carbon mineralization technologies, which are underexplored but would have essentially unlimited capacity if the high costs and many unknowns could be overcome; and (3) advance NET enabling research on biofuels and carbon sequestration that should be undertaken anyway as part of an emissions mitigation research portfolio.

If the US is to embark on such an initiative, it needs to be paired with significant stakeholder engagement to develop a framework for governance that will minimize the moral hazard threat and ensure equity concerns are addressed in any research and development project.

Policymakers, scientists, private companies and civil society will need a thorough understanding of the costs, benefits, uncertainties, and potential harms associated with various CDR options. Engagement with a diverse set of stakeholders who would be affected by their use should occur ahead of making any major decisions or large investments. And more public education about CDR options is an essential step to help foster an informed stakeholder process.

Robust and inclusive systems of governance that are mindful of relevant societal, environmental, ethical, and political considerations can lead to wiser decisions about all technologies and practices that have potentially far-reaching consequences.