ENERGY WATCH #4 - October 23, 2018
“Why we can’t reverse climate change with negative emissions technologies”, was the straightforward title of a recent analysis by CCS-specialist Howard J Herzog of MIT on the website The Conversation.
Herzog notes that featured prominently in the recent IPCC 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, compared to pre-industrial levels.
“Negative emission technologies” comprise a wide range of quite different techniques, notes Herzorg, summarized in this table:
(Note that the table only allows for storing CO2, it does not include the possibility of using CO2 in other applications, see below. KB)
What are the possibilities of these techniques?
Herzog refers to a recent academic paper that 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.
- 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 US$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.
Herzog also quotes two “much harsher” studies:
- A study in Nature Climate Change from 2015 which 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.”
But Herzog has an even more fundamental criticism of NETs. He notes that “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”, he notes, “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?”
Mmhh, good point.
He concludes that it’s OK to use NETs as an offset today, but “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.”
Another academic, Paul Behrens, Assistant Professor of Energy and Environmental Change at Leiden University in the Netherlands, wrote an equally critical article on the Conversation focusing just on BECCS.
He notes that “According to models, BECCS is the technology we are banking on to fix our climate disruption and safeguard our future. The models have doubled down on BECCS, but it is an unproven solution on a large scale – and one that has significant and damaging side effects.”
How much are the models, e.g. from the IPCC, relying on BECCS? A lot. “The reliance is so heavy that, on average, current models for meeting 2℃ suggest we will be using BECCS and afforestation to mop up total, annual global emissions by around 2070 (or 2055 for 1.5℃). This results in a massive growth in BECCS power plants through this period, from three today to 700 by 2030, and 16,000 by 2060.”
Yes, 16,000 BECCS power plants … But, Behrens warns, “large-scale BECCS is a monumentally tricky idea. BECCS aims to fix one thing – climate disruption – but makes many other things worse.”
- BECCS on an industrial scale needs many resources. Plants need land, water and fertilisers (sometimes) to grow, and infrastructure to get low-density plant matter from one place to another. We already struggle to do this sustainably.”
- “Related to this, it is reasonable to think that BECCS will increase food prices. We have to produce 70% extra food by 2050 to just keep up with population and food demand increases. Can we do this while using vast tracts of land for BECCS production? Perhaps only if we have a big change in dietary habits which frees up land?”
- “While BECCS will provide some electricity, you don’t get much bang for your buck – it has the lowest power density of any other type of energy.”
- “BECCS make use of thermal power plants so inherit many problems related to running them. Power plants are heat engines and need water for cooling. We already have problems with water cooling, and it is getting worse with climate change.”
- “Finally, BECCS power plants will produce ash, which is a “better” version than the ash from coal plants (it doesn’t take much), but will still need attention.”
Behrens wonders: how did how did we end up in a situation where the large majority of models point to this one problematic solution?
The reason may be the models themselves. “These models are called Integrated Assessment Models, and come in two main varieties: simple and complex”, explains Behrens. “The complex ones are mostly used for investigating technology choices. The simple ones are often used to explore what the cost of carbon could be. This year’s Nobel Prize winner in economics, Bill Nordhaus, works with these simple models.”
“The overall weaknesses of these models have been covered in compelling and entertaining ways. Given the depth of the complex models, it is difficult to be sure why BECCS dominates. Most would agree that there are three likely possibilities.:
- First, these models discount future benefits and costs to a large extent. That is, they assume that future benefits and costs are much less in the future than they are today. The default rate at which models discount is 5% per year, meaning that to avoid $100 of climate damage in 2100 is only worth $3 to us today. Many have argued that this is much too high, ethically inappropriate, and misleading.
- I know of only one study which performs a sensitivity analysis using so-called discount rates. It finds that carbon dioxide removal is significantly reduced with lower discount rates.
- Second, these models are very sensitive to prices and since a very low price for BECCS is assumed, this is the technology that dominates. The problem is that we don’t actually know what these prices might be, especially on a large scale.
- Third, these models have a difficult job estimating the damage from climate change. The risk from emitting now and paying later is fat-tailed – there is a non-negligible increased risk of catastrophe even if we do manage to implement choice two at a large scale.
Are there other carbon removal technologies that are more promising? “If we must hypothesise backstop technologies, then direct air capture is a possibility”, writes Behrens. “As the name implies, it sucks carbon directly from the air.”
“Although it doesn’t generate energy in the process (in fact it uses large amounts of energy), it doesn’t have as many of the problems faced by BECCS. A possible future consists of solar-powered direct air capture in the Middle Eastern desert pulling carbon dioxide from the atmosphere and pumping it underground into reservoirs from which oil was once pumped. This is speculative though, comes with its own big problems, and as yet doesn’t feature much in modelling efforts due to its high cost (though they are coming down quickly).”
Nonetheless, the number of companies working on direct air capture is increasing. The Guardian mentioned four of them in an article recently – Blue Planet, Carbon Engineering, Climeworks and Global Thermostat – noting that they all try not just to capture CO2 directly from the air, they also try to turn the CO2 into a sellable product.
“Carbon Engineering markets a carbon-neutral fuel. Climeworks sends carbon to fertilizers, fuels and soon, the beverage industry. Global Thermostat sells the gas for a wide range of purposes.”
But the Guardian did note that “products made with carbon don’t demand a high enough price to boost capture around the world, so expanding them will require government intervention.”
Louise Charles, a spokeswoman for Climeworks, “said the company has found government support in Europe and has 14 direct-air capture plants built or under construction. But she said there just isn’t enough money in the industry yet. Next year, Climeworks will enter a new market, letting individuals pay to catch and store carbon to account for their own emissions from flying and driving.”
Steve Oldham, the CEO of Carbon Engineering, said interest in his company has increased in the last few weeks in light of the IPCC report, which he said may be good for business but is overall “kind of scary”.
“We think we have a solution that could be part of solving the problem,” Oldham said. “But the missing piece in the middle is policy, and policy requires both need and a solution.”