Slashing emissions and transitioning to green energy is no longer enough to meet the world's climate goals.

The UN's Intergovernmental Panel on Climate Change (IPCC) said last year that even if we manage to halve emissions by 2030 — already a major challenge — we would still need to rely on carbon dioxide removal technologies, or CDR, to remove CO2 from our air and oceans.

"The deployment of CDR to counterbalance hard-to-abate residual emissions is unavoidable if net-zero carbon dioxide or greenhouse gas emissions are to be achieved," said the IPCC's report on emission reduction and mitigation efforts.

Another recent study said humans will need CDR technology to extract between 450 billion and 1.1 trillion metric tons of CO2 by 2100, alongside deep emissions cuts.

Some of the options, like planting more trees and maintaining current forest ecosystems, are relatively straightforward, though they have their own challenges. But new technologies being touted, like bioenergy with carbon capture and storage, or BECCS, are still limited and mostly untested on a larger scale.

What is BECCS?

Put simply, BECCS involves burning biomass feedstock — wood, energy crops or solid agricultural and municipal waste — to generate energy. The resulting carbon emissions are then captured and pumped deep underground, permanently stored in natural reservoirs.

Proponents have called it a negative emission technology, pointing out that trees and other plant matter naturally remove CO2 from the air. By planting and processing managed forests and crops, they say, we could sequester even more carbon and eventually reduce the level of carbon dioxide in the atmosphere.

CO2 can also be extracted directly from the air using filters and chemicals, then stored underground, in a process known as direct air capture with carbon storage, or DACCS. However, these facilities need more energy to run, and are also expensive.

BECCS 'holds massive potential'

"The climate change problem is too big to leave a solution like BECCS unexplored to its fullest potential, regardless of early skepticism," said Meron Tesfaye, a senior policy fellow for Carbon180, a US-based NGO focused on carbon removal solutions, in a May 2021 article. "And recently, there has been encouraging research and policies that support the idea that BECCS may be underutilized and holds massive potential."

She did add, however, that it's not a one-size-fits-all solution, and that local realities and environmental concerns must be considered.

Backers, among them trade association Bioenergy Europe, have said BECCS could help decarbonize industries where emissions will be hard to abate, including iron and steel, aviation, shipping and cement.

"The vital interest of the EU is to release the full potential of BECCS," said the association in a May 2020 position paper. "This technology facilitates deep decarbonization of the EU's economy, while at the same time opening the opportunity for green growth."

A 'tempting chimera?'

Critics, however, have pointed out that BECCS has a number of drawbacks, including substantial social and environmental costs, not to mention the expense.

"Its false promise of a quick technical fix is heavily promoted by fossil fuel interests, and it must not be allowed to distract from the urgent need to stop burning fossil fuels and to protect and restore forests, soils and other ecosystems," said European forestry NGO Fern in a recent paper.

Fern, which calls BECCS a "tempting chimera," said the process is unreliable, as it depends on too many variables to be a real option.

"The whole BECCS processing chain is energy intensive and leaks so much carbon dioxide that it might not even achieve zero emissions in some cases," said Fern, adding that emissions reductions using BECCS would depend on several factors, including the choice of biomass and land-use changes required to grow the necessary crops. It could also lead to indirect emissions from transport, growing and harvesting biomass and the CO2 capturing and storing process itself, wrote the NGO. 

Impact on food production, water, biodiversity

The biomass needed to fuel the BECCS facilities would also have to come from somewhere. Analysts have said the land needed to grow enough crops or trees would also compete with agricultural land needed for food.

Fern, citing a 2015 study in the scientific journal Nature Climate Change, said keeping warming to below 2 degrees Celsius (3.6 Fahrenheit) using BECCS technology would require a growing area between one to two times the size of India to provide sufficient biomass.

"Such huge land-use change could also cause serious deterioration of soil, making it harder to grow food, and having dramatic impacts on water and biodiversity," it said.

In a report for UK policy institute Chatham House, senior research fellow Daniel Quiggin found that wheat straw would have the optimal carbon efficiency for BECCS facilities in the United Kingdom, storing up to 74% of CO2 compared with other feedstocks.

But, he said, if 100% of the BECCS feedstock consisted of domestically grown wheat straw, it would take up almost a third of the UK's current agricultural land area, "a substantial proportion that could have implications for food prices."

The European Academies' Science Advisory Council (EASAC) said in a February commentary that many of the BECCS scenarios included in net-zero targets are unrealistic.

"If we look at the science, there is a significant gap between the assumed biomass use and the quantities available that are sustainable and do not conflict with higher value uses such as food production, ecosystem retention, environmental and social constraints as well as increased demands for other uses," said Lars Walloe, chair of EASAC's Environment Steering Panel.

He added that the difference between the amount of biomass needed, and what would actually be available, could be as high as 60%.

BECCS places 'significant risks on future generations'

Chatham House expert Quiggin, and others, have cautioned that nearly all the current net-zero targets rely too heavily on carbon removal options such as BECCS, with many policymakers overestimating its capacity and overlooking technical and economic limitations.

"While scientists treat models as 'experimental sandpits,' policymakers tend to see them as 'truth machines,'" he said. "A worst-case scenario of over reliance on BECCS policies and their poor implementation could delay or deter emissions reductions, and result in 'imagined offsets.'" One analysis indicates that such an over reliance could cause an "additional temperature rise of up to 1.4 degrees C."

EASAC said part of the heavy emphasis on carbon removal technologies could be attributed to climate modelling tools that seek to avoid devoting large sums to emissions reductions today, postponing that investment into the future.

"Banking on future technologies such as BECCS to compensate later for inadequate emission reductions today places significant risks on future generations," said Michael Norton, director of EASAC's environment program. He recommended that BECCS projects remain limited in scale, using local feedstocks, and that climate strategies consider carbon removal technology as an additional mitigation strategy, and not an integral part of the plan.

"The danger remains that BECCS will be offered to policymakers as a climate solution to avoid the more politically challenging mitigation options," he said.

Edited by: Tamsin Walker