The best of EcoWatch, right in your inbox. Sign up for our email newsletter!
Why We Can’t Reverse Climate Change With ‘Negative Emissions’ Technologies
By Howard J. Herzog
Featured prominently in the report is a discussion of a range of techniques for removing carbon dioxide from the air, called Carbon Dioxide Removal (CDR) technologies or negative emissions technologies (NETs). The IPCC said the world would need to rely significantly on these techniques to avoid increasing Earth's temperatures above 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, compared to pre-industrial levels.
Given that the level of greenhouse gases continues to rise and the world's efforts at lowering emissions are falling way short of targets climate scientists recommend, what contribution we can expect from NETs is becoming a critical question. Can they actually work at a big enough scale?
What Are Negative Emissions Technologies?
There is a wide range of opinion on how big an impact these techniques can have in addressing climate change. I became involved in the debate because two of the most prominent negative emissions technologies involve CO2 capture and storage (CCS), a technology that I have been researching for almost 30 years.
Many NETs remove the CO2 from the atmosphere biologically through photosynthesis—the simplest example being afforestation, or planting more trees. Depending on the specific technique, the carbon removed from the atmosphere may end up in soils, vegetation, the ocean, deep geological formations, or even in rocks.
NETs vary on their cost, scale (how many tons they can potentially remove from the atmosphere), technological readiness, environmental impacts and effectiveness. Afforestation/reforestation is the only NET to have been deployed commercially though others have been tested at smaller scales. For example, there are a number of efforts to produce biochar, a charcoal made with plant matter that has a net negative carbon balance.
A recent academic paper discusses the "costs, potentials, and side-effects" of the various NETs. Afforestation/reforestation is one of the least expensive options, with a cost on the order of tens of dollars per ton of CO2, but the scope for carbon removal is small compared to other NETs.
On the other extreme is direct air capture, which covers a range of engineered systems meant to remove CO2 from the air. The costs of direct air capture, which has been tested at small scales, are on the order of hundreds of dollars or more per ton of CO2, but is on the high end in terms of the potential amount of CO2 that can be removed.
A handful of commercial companies are testing direct air capture technology,, which takes carbon dioxide out of the air. This project in Italy will use the CO2 to ultimately produce natural gas to power vehicles. Climeworks
In a 2014 IPCC report, a technology called bio-energy with carbon capture and storage (BECCS) received the most attention. This entails burning plant matter, or biomass, for energy and then collecting the CO2 emissions and pumping the gases underground. Its cost is high, but not excessive, in the range of $100-200 per ton of CO2 removed.
The biggest constraint on the size of its deployment relates to the availability of "low-carbon" biomass. There are carbon emissions associated with the growing, harvesting and transporting of biomass, as well as potential carbon emissions due to land-use changes—for example, if forests are cut down in favor of other forms of biomass. These emissions must all be kept to a minimum for biomass to be "low-carbon" and for the overall scheme to result in negative emissions. Potential "low-carbon" biomass includes switchgrass or loblolly pine, as opposed to say corn, which is currently turned into liquid fuels and acknowledged to have a high carbon footprint.
Some of the proposed NETs are highly speculative. For example, ocean fertilization is generally not considered a realistic option because its environmental impact on the ocean is probably unacceptable. Also, there are questions about how effective it would be in removing CO2.
A 2017 study at the University of Michigan did a literature review of NETs. One the one hand, they showed that the literature was very bullish on NETs. It concluded these techniques could capture the equivalent of 37 gigatons (billion tons) of CO2 per year at a cost of below $70 per metric ton. For comparison, the world currently emits about 38 gigatons of CO2 a year.
However, I think this result should be taken with a large grain of salt, as they rated only one NET as established (afforestation/reforestation), three others as demonstrated (BECCS, biochar and modified agricultural practices), and the rest as speculative. In other words, these technologies have potential, but they have yet to be proven effective.
Other studies have a much harsher view of NETs. A study in Nature Climate Change from 2015 states, "There is no NET (or combination of NETs) currently available that could be implemented to meet the <2°C target without significant impact on either land, energy, water, nutrient, albedo or cost, and so 'plan A' must be to immediately and aggressively reduce GHG emissions." In another study from 2016, researchers Kevin Anderson and Glen Peters concluded, "Negative-emission technologies are not an insurance policy, but rather an unjust and high-stakes gamble. There is a real risk they will be unable to deliver on the scale of their promise."
The bottom line is that NETs must be shown to work on a gigaton scale, at an affordable cost, and without serious environmental impacts. That has not happened yet. As seen from above, there is a wide range of opinion on whether this will ever happen.
A critical question is what role NETs can play, both from a policy and economic point of view, as we struggle to stabilize the mean global temperature at an acceptable level.
One potential role for NETs is as an offset. This means that the amount of CO2 removed from the atmosphere generates credits that offset emissions elsewhere. Using negative emissions this way can be a powerful policy or economic lever.
For example, with airline travel the best approach to net zero emissions may be to let that industry to continue to emit CO2, but offset those emissions using credits from NETs. Essentially those negative emissions are a way to compensate for the emissions from flying, which is expected to rely on fossil fuels for many years.
About 25 percent of our current carbon emissions can be classified as hard to mitigate. This offset model makes economic sense when the cost of negative emissions is less than the cost to cut emissions from the source itself. So if we can produce negative emissions from say BECCS at about $150 per ton of CO2, they can economically be used to offset emissions from aircraft that would cost several hundred dollars per ton CO2 to mitigate by changing how planes are fueled.
The economics of using NETs to correct an "overshoot" are very different.
We as a society seem unwilling to undertake sufficient efforts to reduce carbon emissions today at costs of tens of dollars per ton CO2 in order to keep enough CO2 out of the atmosphere to meet stabilization targets of 1.5 or 2 degrees Celsius. However, correcting an "overshoot" means we expect future generations to clean up our mess by removing CO2 from the atmosphere at costs of hundreds of dollars or more per ton CO2, which is what the future deployment of NETs may cost.
This makes no sense, economic or otherwise. If we are unwilling to use the relatively cheap mitigation technologies to lower carbon emissions available today, such as improved efficiency, increased renewables, or switching from coal to natural gas, what makes anyone think that future generations will use NETs, which are much, much more expensive?
That's why I see the role of NETs as an offset being very sound, with some deployment already happening today and increased deployment expected in the future. By contrast, treating NETs as a way to compensate for breaking the carbon budget and overshooting stabilization targets is more hope than reality. The technical, economic and environmental barriers of NETs are very real. In formulating climate policy, I believe we cannot count on the future use of NETs to compensate for our failure to do enough mitigation today.
Howard J. Herzog is a senior research engineer at the Massachusetts Institute of Technology.
Disclosure statement: Howard J. Herzog receives funding from Energy Futures Initiative, Exxon-Mobil, QRI, Total.
Reposted with permission from our media associate The Conversation.
- The ultimate guide to negative-emissions technologies — Quartz ›
- What they don't tell you about climate change - Negative-emissions ... ›
EcoWatch Daily Newsletter
‘Companies Should Not Be Allowed to Use Hazardous Ingredients in Products People Use’: Michelle Pfeiffer Speaks Up for Safer Cosmetics
The beauty products we put on our skin can have important consequences for our health. Just this March, the U.S. Food and Drug Administration (FDA) warned that some Claire's cosmetics had tested positive for asbestos. But the FDA could only issue a warning, not a recall, because current law does not empower the agency to do so.
Michelle Pfeiffer wants to change that.
The actress and Environmental Working Group (EWG) board member was spotted on Capitol Hill Thursday lobbying lawmakers on behalf of a bill that would increase oversight of the cosmetics industry, The Washington Post reported.
By Julia Conley
Scientists at the United Nations' intergovernmental body focusing on biodiversity sounded alarms earlier this month with its report on the looming potential extinction of one million species — but few heard their calls, according to a German newspaper report.
The climate crisis is a major concern for American voters with nearly 40 percent reporting the issue will help determine how they cast their ballots in the upcoming 2020 presidential election, according to a report compiled by the Yale Program on Climate Change Communication.
Of more than 1,000 registered voters surveyed on global warming, climate and energy policies, as well as personal and collective action, 38 percent said that a candidate's position on climate change is "very important" when it comes to determining who will win their vote. Overall, democratic candidates are under more pressure to provide green solutions as part of their campaign promises with 64 percent of Democrat voters saying they prioritize the issue compared with just 34 percent of Independents and 12 percent of Republicans.
President Donald Trump has agreed to sign a $19.1 billion disaster relief bill that will help Americans still recovering from the flooding, hurricanes and wildfires that have devastated parts of the country in the past two years. Senate Republicans said they struck a deal with the president to approve the measure, despite the fact that it did not include the funding he wanted for the U.S.-Mexican border, CNN reported.
"The U.S. Senate has just approved a 19 Billion Dollar Disaster Relief Bill, with my total approval. Great!" the president tweeted Thursday.
"There was a lot of devastation throughout the state," Governor Mike Parson said at a Thursday morning press conference, as NPR reported. "We were very fortunate last night that we didn't have more injuries than what we had, and we didn't have more fatalities across the state. But three is too many."