With the release of the latest special report by the Intergovernmental Panel on Climate Change, it’s 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 1.5℃.

Read more: The UN's 1.5°C special climate report at a glance

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 - 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 “overcorrect” 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.

It’s 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 1.5℃ and 2℃ scenarios run by models have doubled down on the second choice. But this lessens the need for unprecedented changes today.

Read more: New UN report outlines 'urgent, transformational' change needed to hold global warming to 1.5°C

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.

Bonfire of the BECCS

But 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.

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 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.

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 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 it’s own big problems, and as yet doesn’t feature much in modelling efforts due to its high cost (though they are coming down quickly though).

Read more: The science is clear: we have to start creating our low-carbon future today

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-CO₂ 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.