
A pilot study for bioenergy carbon capture and sequestration is taking place at a Drax power station in the UK. Photo: michaeljoakes
Most models for meeting 1.5â or 2â climate change targets suggest we will be using bioenergy carbon capture and sequestration (BECCS) to mop up the worldâs total annual CO2 emissions by around 2070 (for 2â). This means moving from todayâs three BECCS power plants to 16,000 by 2060. But, explains Paul Behrens of Leiden University, large-scale BECCS is a âmonumentally tricky idea,â and, while aiming to fix climate disruption, it makes many things worse.
With the release of the latest special report by the Intergovernmental Panel on Climate Change, itâs time we talk frankly about Bioenergy Carbon Capture and Sequestration, known as BECCS. It is one of the key technologies many models say we will need to limit warming to 1.5â.
BECCS involves growing plants which remove carbon dioxide as they grow and are then burned in power stations to produce electricity. The resulting carbon dioxide from this combustion is captured and stored underground. The result is carbon dioxide removal from the atmosphere.
It is the not-so-high-tech wonder many are waiting for, but it comes at a high price. It also risks delaying policies that actually reduce emissions in the first place.
Mapping the future, now
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 â and one that has significant and damaging side effects.
There are three choices on the table (we will likely see a mix of at least two):
- Equitable sustainability Massive amounts of low-carbon energy (solar, wind, batteries, electric vehicles), huge improvements in energy efficiency, a revolution of the food systems and a transition of society towards lower growth, both in population and economy.
- Hypothetical backstop Continue down the road we are on, and hope to âovercorrectâ the problem in the future by sucking carbon dioxide out of the atmosphere. A lack of political will and intense lobbying has meant what was once a fairly manageable problem has become an exercise in inventing heroic backstops.
- Cowboy optimism Engineer the planet (even further) to ease the impacts of climate disruption, but not the underlying causes themselves.
The first choice means we change ourselves and alter the way we do things. The second means we continue polluting as we do now, and hope to clean up later. This option is a bit like the plastic clean-up trial currently underway in the Pacific.
Choice three means we simply paper over the cracks, perhaps saving some aspects of human civilisation but pushing large parts of nature to extinction.
The models have doubled down on BECCS, but it is an unproven solution on a large scale â and one that has significant and damaging side effects
Itâs worth noting that in any scenario, massive investment by richer countries on behalf of poorer countries will be necessary. This is already a significant problem.
Given the delay, the majority of 1.5â and 2â scenarios run by models have doubled down on the second choice. But this lessens the need for unprecedented changes today.
The reliance is so heavy that, on average, current models for meeting 2â suggest we will be using BECCS and afforestation to mop up total annual global emissions by around 2070 (or 2055 for 1.5â). 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.
Bonfire of the BECCS
But large-scale BECCS is a monumentally tricky idea. BECCS aims to fix one thing â climate disruption â 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 donât get much bang for your buck â it has the lowest power density of any other type of energy.
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?
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 âbetterâ version than the ash from coal plants (it doesnât take much), but will still need attention.
The role of Integrated Assessment Models
The origin story for BECCS has been told elsewhere, but how did we end up in a situation where the large majority of models point to this one problematic solution? These models are called Integrated Assessment Models, and come in two main varieties: simple and complex.
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 yearâs 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 donât 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 â there is a non-negligible increased risk of catastrophe even if we do manage to implement choice two at a large scale.
Taking off the BECCS blinders
Are there technologies other than BECCS? If we must hypothesise backstop technologies, then direct air capture is a possibility. As the name implies, it sucks carbon directly from the air.
Although it doesnât generate energy in the process (in fact it uses large amounts of energy), it doesnât 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 itâs own big problems, and as yet doesnât feature much in modelling efforts due to its high cost (though they are coming down quickly though).
Fortunately, there are an increasing number of studies which take a non-backstop approach. These still use integrated assessment modelling, but investigate other options, like very low-energy demand scenarios and large-scale behaviour change (for example to plant-based diets), which reduce other, non-COâ gases quickly.
There is nothing to be lost by committing to the first choice as fast as possible. In fact, many of the important solutions are better for our health too (such as using bikes instead of cars, plant-based diets and insulating houses). And if we end up needing BECCS, then so be it, but the earlier we start moving to low-carbon economies, the more potential catastrophes we avoid.
Editor’s note
Paul Behrens is Assistant Professor of Energy and Environmental Change, Leiden University in the Netherlands. This article first appeared on The Conversation and is republished here under a Creative Commons licence.
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With regard to Direct Air Capture, Global Thermostat states âa price of $50 per ton is achievable:âÂ
https://grist.org/article/direct-air-carbon-capture-global-thermostat/
So, adding $10/ton for sequestration, 50 gigatons @ $60/ton would be $3 trillion/year, and global GDP is over $75 trillion/year.
As for BECCS, in the US, the DOE estimates a billion dry tons of biomass can be grown each year w/out adverse environmental impact, and would not negatively affect the production of food or other agricultural products:
https://www.energy.gov/sites/prod/files/2016/12/f34/2016_billion_ton_report_12.2.16_0.pdf
If the carbon in this biomass were fully sequestered that could draw down up to 1.75 gigatons of atmospheric CO2/year.
Gasifying the biomass to fuel Allam cycle turbines would capture the carbon. Allam cycle turbines can burn methane while capturing all CO2, at the same cost as existing combined cycle plants. The cost to transport and sequester that CO2 is around $10/ton, so wouldn’t add much to that cost. Sequestration makes the process carbon negative.
The good news is the cost of wind, solar, and storage is down and expected to keep dropping. And according to Berkeley Lab, EVs with smart chargers can serve as much of the storage required, so together those address much of the electric power and transportation emissions. If we estimate 90% electricity from solar & wind with storage at $.03/kWh, and the other 10% from dispatchable carbon negative BECCS at $.15/kWh, the cost would average out to $.042/kWh.
biomass poer generation without burning it in traditional power stations, but using anerobic digestion and gas motors needs quite little water for plant cooling, and delivers around 325-55% CO2 if I remember right in the biogas . Which is a quite high concentration, and it is useful anyway to remove the CO2 before stroing or transporting the CH4 in pipelines or gas storages. Starting with a high concentration of CO2 makes it easy to collect and sequester it. In the best case by using all kinds of wastes from food production.
I’ve just heard of a collaboration between Drax and C-Capture which it’s claimed could enable Drax Power Station to become carbon negative. Good if it work out:
https://www.drax.com/press_release/leeds-mp-visits-ground-breaking-carbon-capture-company/