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Can BECCS pull us back from the brink of climate breakdown?

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Released last week, the Intergovernmental Panel on Climate Change’s special report was intended to provide a wake-up call to a civilisation nearing the edge of its runway. Backed by years of research, the report shows that the difference between 1.5 degrees and 2 degrees Celsius of global temperature rise would be more dramatic than scientists had previously suspected.

Unfortunately, it also served as a reminder that the world is not on course to achieve the good-will target of 1.5 degrees set by the Paris agreement. Nor is it on course to achieve the less ambitious target of 2 degrees.

Instead, every country successfully fulfilling its current climate pledges would in all likelihood still result in warming of 3 degrees or more by the year 2100.

The IPCC report underscored another uncomfortable fact - one that climate models have been pointing towards for some time. Barring transformational changes in the way we eat and the amount of energy we consume, the world will need to rely heavily on some combination of negative emissions technologies and afforestation to stay within the crucial 1.5 degrees temperature limit.

Even in the most optimistic pathways, reductions in energy sector emissions will not happen quickly enough to prevent catastrophic global warming on their own. That means that the transition to renewables, as essential as it may be, won't be enough to get the job done.

“Because we have done so little for so long, we now need to do everything,” is how Cameron Hepburn, an expert in energy and climate economics from New College Oxford, puts it. “Negative emissions technologies are required because we have been too slow in curbing emissions.”

On track for overshoot

Although a number of negative emissions technologies are currently being researched – from direct air capture, to enhanced weathering and ocean fertilisation – the one that figures largest in climate modellers’ thinking is bio-energy with carbon capture and sequestration, or BECCS.

The idea behind BECCS is to produce energy through the combustion of biomass from dedicated energy crops and/or residues from food agriculture and forestry. The CO2 released from burning the biomass is captured before it reaches the atmosphere, and is then injected into underground storage reservoirs – typically depleted oil and gas fields.

In this way, BECCS is intended to reverse the process that is leading to climate breakdown. Where fossil fuels cause carbon from long dead biomatter to be released into the atmosphere, BECCS uses living biomatter to fix, capture and sequester that same atmospheric carbon.

BECCS and other negative emissions technologies play a significant role in the majority of the ninety pathways outlined in the IPCC special report consistent with 1.5 degrees of warming by 2100. The remainder envisage dramatic near-term reductions in both land use and energy demand. That’s because the models show that without such reductions, a temperature overshoot – in which global temperature rise temporarily exceeds 1.5 degrees – is all but certain. Negative emissions technologies are needed to bring it back down again.

Even in the non-overshoot pathways, removal of atmospheric carbon is critical. One of the IPCC report’s lead authors, Sabine Fuss, tells me that “all assessed pathways that lead to 1.5°C with little or no overshoot clearly feature full [emissions] mitigation, and carbon removal on top of it.” Where negative emissions technologies play less of a role, afforestation is more widespread – which is why dietary changes that reduce the area devoted to cropland are a must.

These pathways are, however, a tough sell. Whether we can avoid resorting to negative emissions technologies is “an argument about your definition of what’s possible,” says Naomi Vaughan, a Senior Lecturer at the Tyndall Centre for Climate Change Research. The uncomfortable truth is that an overshoot can’t be prevented without public willingness to make lifestyle changes that few are currently prepared for. “We’re running through our carbon budget so fast that 1.5 is just around the corner,” Vaughan says. “An overshoot is all you’ve got left given how much inertia there is in the system, and how small your carbon budget is.”

A problematic solution

But BECCS is far from a widely accepted solution. And there are some good reasons to be wary of it. For instance, using BECCS to bring net emissions down to the levels envisaged by optimistic climate modelling requires a lot of land.

It’s worth repeating that - BECCS requires a lot of land. The lower bound of estimates places the amount needed as equal to the land area of India. The upper bound places it as equivalent to the total land area currently under cultivation. In a world on track to reach 10 billion inhabitants by mid-century, this land may be hard to come by without impacting food availability and biodiversity.

It’s a big problem to solve, because implemented badly, BECCS actually has the potential to increase atmospheric carbon levels, rather than lowering them. That may seem counterintuitive for a negative emissions technology. But if cultivating energy crops for BECCS contributes directly or indirectly to deforestation, doing so will release large quantities of soil carbon into the atmosphere, and destroy some of the world’s biggest natural carbon sinks.

Here’s another issue. Although there are some examples of BECCS projects already underway (such as ADM’s ethanol plant in Decator, Illiois), there is nothing like an established BECCS industry to speak of. Implementing the technology will mean creating a global network of cultivation areas, supply chains and power generation facilities, as well as the regulations and incentive structures needed to support them – all of this effectively from nothing.

Both of these concerns are to some extent valid. But it would be a mistake to see them as immutable – not without further scrutiny, at least. Let’s take a look at each problem in greater detail.

Is there enough land available for BECCS without causing deforestation?

We’ve established that the land use requirements for BECCS are substantial. But it’s worth asking where the huge discrepancies between the low-level and top-level estimates come from.

The short answer is that the land requirements of BECCS are determined chiefly by two things: the type of biomatter used, and the quality of land used. Let’s start with the type of biomatter. The studies that provide the largest estimates, Vaughan tells me, get “all of their bioenergy from just energy crops.”

But focusing solely on energy crops is needlessly land intensive. “In the model that I work most closely with, about half of the bioenergy comes from energy crops, and about half of it comes from forestry and agricultural residues… even if you’re trying to get the same amount of bioenergy, you have a size doubling dependent on whether you use residues or not.”

Nevertheless, questions remain about the level of contribution agricultural residues can make. Taking too much of the material that remains in the field after harvesting leads to degradation of the soil, with adverse implications for future yields. Vaughan says that the scenarios covered by her research “assume a certain amount of the residue is left in situ” to prevent soil carbon loss. Further analysis may still be required to establish sustainable levels for different crops, however.

The quality of the land used is the flip side of the coin. Fuss says that land use estimates in the IPCC pathways depend “on which bioenergy technologies are used and which land is available for cultivating the biomass - highly productive land vs marginal land.” Unfortunately, the most productive land is also the land that faces the most competition for food production, and potentially for afforestation too.

To overcome this limitation, Vaughan’s research focuses on cellulosic energy crops that can be grown plentifully on marginal land or virgin grasslands – namely miscanthus, switchgrass, and short rotation coppices like poplar or willow. We’ve written previously on this blog about how miscanthus and switchgrass are both hardy plants that can be cultivated economically on poor quality land without having to compete with food crops.

By making the right decisions about which energy crops we grow, how we use different types of land, and how we maximise our utilisation of residues within sustainable limits, Vaughan believes that it is possible to build a system in which pursuing BECCS doesn’t result in unacceptable trade-offs for food production and biodiversity.

But “there is a difference between what you can do in a model which follows your rules, and what happens on the ground in the real world,” she says. “Doing bioenergy well is about your governance structures in the places that you are going to do it. The governance, the incentives, and the regulations.” Fuss is in agreement. “It is important to accompany incentives for bioenergy - whether with or without CCS doesn’t matter - with strong sustainability criteria for the sourcing of the biomass,” she tells me. “Certification could be one tool.”

A final point to make on land use is that steering clear of BECCS doesn’t necessarily solve the problem. The IPCC “pathways that limit BECCS often have even more bioenergy leading to an even larger land footprint,” Fuss says. “You see these issues reflected in the huge ranges we report for land use change in the 1.5°C pathways - e.g. a loss of 1 million km² forest area versus a gain of 10 million km².”

Even without BECCS, a dramatic increase in the contribution of bioenergy is a fairly consistent feature of low emissions scenarios. “Bioenergy is envisaged to grow massively,” Vaughan says. “From 10 exajoules at the moment globally to 100 exajoules or higher, accounting for up to a third of the global energy system.”

Can we build a BECCS industry from the ground up?

The challenge of building a BECCS industry should not be made light of. But whether or not we have the technological capacity to do so is beyond contention. The technologies underlying biomass electricity generation and carbon capture and storage are both here now, and they have been for some time. Biomass accounted for 196 TWh of European power generation last year, or 6% of the total.

As to CCS, the Sleipner CO2 storage facility in the North Sea has been sequestering 0.85 million tonnes of CO2 every year for over two decades. Taken as a proportion of global emissions, that’s not a great deal. But it shows that the technology is both workable and profitable to operate with the necessary incentives in place.

BECCS is more a combination of two existing technologies, than a new technology in its own right. As such, the problems posed by bringing bioenergy and CCS together are more geographical than technical. “There is a disparity between regions where you might grow bioenergy crops, versus regions where you might have the right geology for storage,” Vaughan says. “Only a handful of countries that have their own domestic biomass resource on a sufficient scale, combined with an easily accessible storage site on a sufficient scale.”

Overcoming this problem means developing trade between the regions that are able to produce biomass and the regions that are able to sequester carbon. “The implication,” says Fuss, “is that either the biomass needs to be transported or the captured CO2 - indicating the need for a careful analysis of life cycle emissions and costs.”

To the extent that growing regions need biomass to meet their own energy needs, CO2 transportation may prove to be the better option. Even so, developing a system of incentives that fairly rewards the various players in the BECCS supply chain will not be simple. “In an ideal world, all mitigation and carbon removal would be triggered by a global carbon price,” Fuss says. “A difficulty specifically with BECCS is who gets the credit: the one who grows the biomass? The one who captures the CO2? Or the one who stores it?”

What next?

As a solution to climate breakdown, BECCS is clearly not without problems. Much better, some will say, to prevent emissions rising high enough to ever need it.

They are right: every effort should be made to prevent global temperature rise climbing above 1.5 degrees. But as the clock ticks on and our options narrow, the likelihood of avoiding temperature overshoot diminishes – and with it, the likelihood of avoiding negative emissions technologies. “There is no scope for not reducing emissions”, says Hepburn. “I think it is just harsh reality that we need to put overshoot scenarios on the table.”

Irrespective of where you stand on BECCS, you should bear something in mind. Many of the steps we need to take to prepare the ground for the technology are steps that we should be taking anyway.

Improving international cooperation on carbon pricing; establishing consistent sustainability criteria for energy crops; equipping power plants and industrial sites with carbon capture technology; developing a land use strategy that optimises food production, bioenergy potential and biodiversity across national boundaries: none of these are controversial propositions. But each of them needs to be done to limit warming to 1.5 degrees.

And each of them will make the challenges posed by BECCS less severe, should the technology prove necessary.

Find out more about the future of energy at the Energy Transition World Forum, taking place in Amsterdam this coming May. 

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