Achieving an energy economy based entirely on renewables quickly enough to meet the Paris goal of 2ºC is a high-risk strategy. Removing carbon dioxide from emissions waste streams and burying it is necessary — as may be extraction of the gas from the atmosphere.

Alan Miller retired from the Climate Business Department at the International Finance Corporation in December 2013 and is now an independent consultant on climate finance and policy

An evaluation of current trends and country commitments by the United Nations Environment Program, the “Emissions Gap Report 2017” estimates that only about a third of the necessary reductions to realize the Paris Agreement’s temperature goals have been pledged. “The gap between the reductions needed and the national pledges made in Paris is alarmingly high,” the report concludes. Reductions must be achieved quickly due to the long atmospheric lifetime of carbon dioxide. Thus, “If the emissions gap is not closed by 2030, it is extremely unlikely that the goal of holding global warming to well below 2°C can still be reached.”

In response to this intimidating challenge, experts have devised many scenarios showing how the Paris goals might be achieved. While continued rapid growth in use of clean energy is central to all such analyses, it is insufficient without a concomitant, radical transition away from current technologies for burning of fossil fuels and particularly coal — which amount to about 40 percent of the world’s electricity and is a key source of energy for cement manufacturing, steel making, and other industrial processes. Yet dozens of new coal plants are currently under construction or planned around the world, and new coal mines have opened even in Germany. Enormous economic and political costs will be incurred if these plants are to be closed in the near future. So any realistic policy scenario must allow for the role of fossil fuels.

To offset this trend and ensure the Paris goals can be met, carbon removal and sequestration (or storage) will be essential. As the International Energy Agency stated in 2016, “There is no other technology solution that can significantly reduce emissions from the coal and gas power generation capacity that will remain a feature of the electricity mix for the foreseeable future.” Indeed, as you shall see we may need to go even beyond that.

A discussion of carbon dioxide removal encompasses a wide range of methods, some natural, some sophisticated, expensive technologies. A National Academy of Sciences review of the subject in 2015 provides several helpful definitions and associated acronyms: “Carbon Dioxide Removal (CDR) refers broadly to efforts to remove carbon dioxide from the atmosphere, including land management strategies . . . and direct air capture and sequestration (DACS). CDR techniques complement carbon capture and sequestration (CCS) methods that primarily focus on reducing CO2 emissions from point sources such as fossil fuel power plants.” Where combined with the use of the captured gas, systems are referred to as CCUS.

Thus, carbon removal can refer to natural, biological processes such as afforestation (planting trees) as well as engineering methods for removing carbon from flue gas or even directly from the air. However, only CCS (as defined by the NAS) attempts to reduce emissions from power plants and thus to address the problem created by the widespread use of coal at its source. While CDR and DACS may prove necessary in the long run, the near term policy focus needs to be on CCS.

Effective CCS requires effective storage as well as carbon capture; leakage into the atmosphere negates the benefits of reduced emissions and could create liability issues deterring investment. Currently, there is substantial opportunity for storage in depleted oil and gas fields. CO2 can also be used for enhanced coal bed methane, the generation of natural gas from deep, unminable coal seams. The effective reduction of CO2 emissions from such methods depends on site conditions and appropriate engineering but provides both some reduction in emissions as well as an economic incentive for the further development of carbon removal. How effective is this technology? An IEA assessment concluded that “the volume of the CO2 injected and stored can significantly outweigh the emissions from combusting the oil that is subsequently produced.” In countries like India and China with low quality coal but very little natural gas, the combination may even be marginally economical without carbon taxes or other incentives.

In the longer term, however, the quantities of carbon dioxide captured will require storage in much larger amounts. According to an IPCC review, “Captured CO2 could be deliberately injected into the ocean at great depth, where most of it would remain isolated from the atmosphere for centuries.” The first real test of such storage was put into operation in Norway more than 20 years ago, but the environmental implications of doing so on a large scale require much more study. As the IPCC review states, “CO2 effects on marine organisms will have ecosystem consequences; however, no controlled ecosystem experiments have been performed in the deep ocean. . . . It is expected that ecosystem consequences will increase with increasing CO2 concentration, but no environmental thresholds have been identified. It is also presently unclear, how species and ecosystems would adapt to sustained, elevated CO2 levels.”

There are several flavors of carbon capture and storage. The three most advanced and demonstrated technologies for power plants are post-combustion CO2 capture, currently used at NRG Energy’s Petra Nova plant in Texas; oxy-combustion, demonstrated at some large pilot plants; and pre-combustion CO2 capture in combination with coal gasification. The third category has received the bulk of support to date, with mixed results as discussed below.

Despite it’s potential for reducing the largest source of carbon dioxide emissions, CCS of any stripe has to date received limited support from Washington or other national capitals. Only 17 projects are in operation worldwide (nine in the United States) with four more under construction. Most of these are linked to industrial facilities with separation of the CO2 part of their process. The current global CO2-capture capacity is only about one tenth of one percent of emissions. Rather than growing, the pipeline of new CCS projects has been shrinking, from 77 in 2010 to around 38 today, and as of a November 2016, IEA report no projects have progressed to construction since 2014.

T he lack of enthusiasm for CCS despite growing evidence of the need is due to several factors. The coal industry has generally preferred to question climate science and the need to do anything. In the absence of carbon taxes or other climate policies, commercial interest in emissions capture has been largely limited to enhanced oil and gas production, in which CO2 is injected into rock formations to force out the fossil fuel. While coal-burning utilities are arguably second only to coal-mining companies in the need for technologies that could allow continued use of coal in energy production, they have had limited incentive to finance the costs of research and demonstration.

A few utilities have shown interest in the potential for combining CO2 capture with coal gasification, the third category above. The Kemper Project in Mississippi, undertaken by one of the country’s largest utilities, the Southern Company, was planned as a commercial-scale demonstration of the technology based on a very small pilot project. Construction was initiated in 2010, and after expenditures of over $7 billion (including a $133 million federal tax credit) the CCS features were abandoned, leaving only the possibility of operating as a natural gas plant. The project was effectively canceled last June by order of the state Public Service Commission, with assignment of financial responsibility still to be resolved.

Some environmentalists were quick to argue that Kemper’s failure illustrates why CCS “is a waste of our tax dollars and a false solution to the climate crisis,” as one put it. However, others pointed to mismanagement unrelated to the technology. This included equipment never tested at commercial scale; inadequate time spent on engineering; a rush to completion to avoid loss of tax credits; and the failure to learn from another gasification facility operating in Indiana. “The Kemper Project failure is not due to any problem with the equipment required to capture CO2,” argue NRDC lawyer David Hawkins and scientist George Peridas. “All of the problems are due to the system components upstream of the capture stage. . . . . The conclusion is not that CCS is a flop.”

Indeed, the case for CCS rests on a combination of arguments from different vantage points. The “Emissions Gap Report” points to the availability of clean energy and land use strategies for emissions reductions but also recognizes the reality that coal use is not going away soon. A headline in the New York Times last July makes the point: “As Beijing Joins Climate Fight, Chinese Companies Build Coal Plants.” Even in relatively green Germany, political and economic realities dictated the opening of new coal mines, partly to compensate for the closing of nuclear power plants. Consequently, the UNEP report acknowledges the potential need for carbon capture technologies of any and all flavors despite their limited development to date.

As the Kemper Project illustrates, much of the current image of CCS is associated with capital-intensive systems with large land requirements and long time requirements for construction. There has also been recent media focus on what might be termed “moon shot” ideas for removing CO2 directly from the atmosphere. A company owned in part by Bill Gates and based in Canada, Carbon Engineering, is attempting to commercialize a process for this feat, described as falling “somewhere between toxic-waste cleanup and alchemy” by the New Yorker writer Elizabeth Kolbert.

Much more attention needs to be given to the existence of the many other promising approaches for CCS, some in development for more than a decade by relatively small companies and entrepreneurs. These innovators are working on ways to capture and store carbon with the potential for low costs, a small footprint, and often additional economic and environmental benefits.

One example is Jupiter Oxygen, a company with more than a decade of experience with carbon capture and a process with multiple environmental benefits. The firm uses oxy-combustion (injecting oxygen in the combustion process to achieve high flame temperatures) in a process that allows very effective removal of CO2 and nitrogen as well as improving energy efficiency and incineration of most conventional pollutants. The company had technical support from the DOE National Energy Technology Laboratory a decade ago, has substantial operating experience, and is currently pursuing partnerships in China and India based on CCUS — enhanced coalbed methane and industrial applications of CO2.

Blue Planet, a company based on pioneering materials science by Stanford doctor and scientist Bret Costanza, uses water-based methods to capture CO2 from flue gas and makes cementitious building materials. The company has attracted impressive support, with an advisory board that includes former FDA Commissioner Donald Kennedy, former National Renewable Energy Lab Director Denis Hayes, and actor Leonardo di Caprio.

The Carbon X-Prize, a competition with a $20 million award for “breakthrough technologies that convert the most carbon dioxide emissions from natural gas and power plant facilities into products with the highest net value,” announced 27 semi-finalists in 2016. One of the most intriguing was originally conceived in a high school chemistry lab by a teenager. The young inventor is now working with a Yale professor and has secured funding to build a pilot plant that will use waste gas from a power plant or chemical factory and capture one metric ton of carbon emissions per day.

Given the magnitude of the effort required and the complexity of the technical challenges, continued support for these and other innovative smaller companies with CCS concepts should be a priority. As a recent “Economist Briefing” observed, “Progress will be needed on many fronts. All the more reason to test lots of technologies. For the time being even researchers with a horse in the race are unwilling to bet on a winner.”

Yet even as current research shows that climate change may be increasingly dangerous and unavoidable, support for CCS remains slow to develop. Perhaps the greatest source of resistance is the belief that alternative approaches are better — and achievable. The proposition that renewable energy can be the solution to climate change has been aggressively advocated and is credible as a mathematical proposition. The rapid rate of advancement in solar, wind, and battery and other energy storage technologies has indeed been, and continues to be, impressive. A recent end of year review by Bloomberg New Energy Finance cites plummeting emissions auction prices, the entry of significant new markets, and record corporate renewable power purchase agreements. On the other hand, the same source points to negative policy developments in several markets including the United States and South Africa — e.g., the recent decision by President Trump to increase tariffs on solar imports — as well as the risk of rising interest rates for renewable technologies with high capital costs.

Assuming the political support could be found for an all-out clean energy strategy and implemented in every large energy-consuming country, there are significant technical issues to be resolved before this could be done consistent with the existing electricity grid. Power from wind and solar energy are variable and not dispatchable consistent with the management and operation of centralized power grids. Reliance on natural gas plants as a backup is not consistent with the aggressive decarbonization required to stay below 2°C. Unless some other alternatives emerge, as clean energy advocate Dave Roberts has noted, CCS will be essential; without it “other dispatchable resources [would] have to dramatically scale up to compensate — we’d need a lot of new transmission, a lot of new storage, a lot of demand management, and a lot of new hydro, biogas, geothermal, and whatever else we can think of.” Thus, while it is theoretically possible the Paris goals can be met based almost entirely on clean energy, the majority of analyses advocate a combination including clean energy and CCS.

Many environmentalists advocate for carbon sequestration through natural means, primarily by planting trees. The CO2 uptake of existing forests is substantial — in the United States offsetting fossil fuel emissions by about 15 percent. Studies suggest about a third of current carbon emissions could be captured this way, potentially even more if conflicts with food production could be managed, with further reductions through environmentally beneficial measures to increase CO2 absorption and retention in soils. Using trees as fuel for power plants could even generate “negative emissions” if combined with CCS technologies — an approach the last IPCC report stated will be “critical in the context of the timing of emissions reductions,” and also dependent on effective technologies for CCS.

Unfortunately, the trend in forestry has been toward more deforestation and forest degradation, collectively estimated to account for 8 to 15 percent of the rise in global CO2 concentrations. While desirable for many environmental and social reasons, reversing this trend has so far proven to be a major challenge. And climate change may make this still more difficult, as reflected in the recent California wildfires, forest dieback due to pests in Colorado, and expectations of more severe drought in some currently forested regions. A recent article in Nature notes that efforts to raise biomass stocks have only been verifiable in temperate forests, where their potential is limited, whereas large uncertainties hinder verification in the tropical forest, where the largest potential is located. California is working on a Forest Carbon Plan, expected to be finalized this year, which could serve as a model.

Given the magnitude of the climate challenge, there is an increasing consensus that all options for mitigating emissions need to be deployed as soon as possible. For some, the situation is so bad that it is now necessary to consider options much more worrisome from an environmental perspective — climate intervention (also called geoengineering). This includes measures such as injection of sulfates in the atmosphere to reflect sunlight and cool the earth’s surface. An initial review by a committee of the National Academy of Sciences concluded in 2016 that such measures merit further research given they could be implemented at a relatively low cost despite “an array of environmental, social, legal, economic, ethical, and political risks.”

Given the seriousness of climate risks and the absence of any single fully effective solution, increasing support for CCS thus seems fully justified and increasingly urgent. In the United States, CCS may also have one additional benefit going for it: a surprising measure of bipartisan political support. Proposals for CCS have attracted backing from both coal state Republicans and liberal Democrats. The Western Governors Association, under the leadership of Wyoming’s Republican governor, Matt Mead, and Montana’s Democratic governor, Steve Bullock, convened a working group composed of 14 states to advocate policies that encourage CCS technologies. A broader coalition with similar interests, the National Enhanced Oil Recovery Initiative, includes fossil fuel companies, labor unions, and national environmental organizations.

Reflecting this diverse political support, last July a bipartisan group of 25 senators introduced the Future Act (for Furthering carbon capture, Utilization, Technology, Underground storage, and Reduced Emissions) to extend and expand a federal tax credit, known as Section 45Q, which incentivizes capturing carbon dioxide from power and industrial sources for enhanced oil recovery and other uses. Another bill with bipartisan support, the Carbon Capture Improvement Act, would authorize states to use tax-exempt private activity bonds to help finance carbon capture equipment. Allowance for such bonds was retained in the recent changes in tax law, a change originally contemplated in the version first passed by the House.

The two bills would be a substantial step toward encouraging increased interest and investment in CCS projects, although limited in key respects. First, insofar as the captured carbon is to be used primarily for enhanced oil recovery or enhanced methane production, fossil fuels are still being burned. Another concern is that the bill would provide limited support for innovative ideas from high-risk companies. Such early stage research support should be a federal responsibility and would seem to be consistent with administration support for coal. At a recent IEA summit, DOE Secretary Rick Perry stated, “While we come from different corners of the world, we can all agree that innovation, research, and development for [carbon capture and underground storage] technologies can help us achieve our common economic and environmental goals.” However, the administration has so far given little indication of formal support for CCS and even proposed significant cuts to the fossil fuel program.

Expanded tax credits for CCS for enhanced oil recovery in the United States also do not promote carbon capture where it is most needed, in China, India, and other rapidly growing developing nations with coal-dependent energy systems. China alone currently produces about four times as much coal as does the United States, and because of their populations and coal reserves the IEA projects that China and India will account for the lion’s share of global growth in coal consumption in coming decades. Whereas in the United States most CCS would be retrofits to existing coal plants, in China and India there will be opportunities for integrating systems with new plants and industrial facilities — particularly if combined with desperately needed control strategies for conventional pollutants like smog precursors, acid rain, and particulates.

There is an established international initiative with the relevant focus, the Carbon Sequestration Leadership Forum, founded in 2003, which now includes ministerial-level participation from 25 countries. There was also some hope for support with the establishment of Mission Innovation, a global initiative announced during the Paris COP21 climate negotiations to encourage clean energy innovation. Seven of the initial 20 sponsors included reference to CCS when the initiative was announced, but U.S. support is now uncertain. A more ambitious, coordinated, and well financed international effort to include all the world’s largest coal producers and consumers is needed. There are multiple institutions and international initiatives for clean energy, including the International Renewable Energy Agency, the Clean Energy Ministerial, and the Climate Technology Centers organized under the UN climate convention. Given the importance of financing, there also needs to be more of a role for the World Bank and other international financial institutions in a position to provide risk capital as well as technical assistance.

Bipartisan political support may be growing in the United States, but it still faces numerous challenges. In recent congressional testimony, a spokesman for the governor of Wyoming focused on the time required to do environmental reviews and permitting of pipelines as equal if not greater obstacles. Broader leadership for long-term CCS development in the United States also remains an issue, as the future of the DOE fossil energy program is in question and the states with the most progressive climate policies have not made it a priority.

Carbon capture and sequestration remains a necessary if less than ideal solution to the challenge of climate change. As time passes and other solutions appear to be inadequate, a growing body of analysis points to CCS as among the only remaining sources of hope for avoiding catastrophic climate change. As the IEA concluded in its 2016 report, “CCS is the potential ‘sleeping giant’ that needs to be awakened to respond to the increased ambition of the Paris Agreement.” TEF