Gambling with Biomass

Gambling with Biomass: Reliance on BECCS undermines National Grid’s net-zero scenarios

National Grid models unlikely to deliver net-zero by 2050 through over-reliance on BECCS

Tom Harrison

Electricity transition analyst

28 October 2020 | 6 min read

  • National Grid ESO’s Future Energy Scenarios (FES) 2020 has modelled the changes in the UK grid required to reach net-zero carbon emissions in the power sector by 2050.
  • The ability to reach all net-zero scenarios is entirely dependent on the generation of negative carbon emissions from bioenergy with carbon capture and storage (BECCS).
  • BECCS is relied upon to abate over 50MTCO2 of residual economy-wide emissions and to provide up to 11% of total UK power by 2050.
  • All net-zero scenarios require conversion of up to 1Mha of UK land – around 7% of total agricultural land – to energy crop production. The highest-ambition scenario requires an additional global conversion of 200Mha – an area the size of Greenland.
  • The scale and effectiveness of BECCS use in FES 2020 relies upon uncritical assumptions and severely undermines the credibility of National Grid’s pathways to reaching net-zero.
  • National Grid’s future models should take the complexity of BECCS into account and include scenarios with more ambitious plans for decarbonisation and alternative methods of generating negative emissions such as additional large scale afforestation.

What is FES?

Each year, National Grid ESO publishes its Future Energy Scenarios (FES) that uses its class-leading energy modelling to set out a number of credible pathways to decarbonising the UK energy sector. Although not predictions or projections based on current policy, the scenarios built and presented in FES provide an essential insight into the trajectory of the UK power sector for utility companies and policy-makers alike. This year’s edition, FES 2020, focuses on achieving net-zero carbon emissions in the power sector by 2050.

What is BECCS?

Bioenergy with carbon capture and storage (BECCS) is the name given to a range of technologies and processes that involve the capture and storage of carbon dioxide emitted from the combustion of biomass. Most commonly BECCS refers to the combustion of biomass in power plants for heat and power generation, and the capture and storage of the resulting emissions in geological deposits such as abandoned oil wells.

There are two major sources of biomass that are widely considered for use in BECCS to generate negative emissions: forestry wastes, such as the offcuts of harvested trees, and crops grown specifically for use in bioenergy.

Theoretically, burning forestry wastes for power can be considered carbon neutral if the same quantity of carbon would be released by the alternative uses of the waste, such as open burning on the roadside. If the combustion of a waste is carbon-neutral then storing carbon from this power generation avoids release of inevitable emissions and results in immediate negative emissions.

In the case of dedicated energy crops, the growth of new biomass generates negative emissions as the plants absorb CO2. When this biomass is harvested, combusted and its emissions are captured and stored, the negative emissions are cached and the process of new growth can begin again. Although biomass starts absorbing CO2 as it grows after planting, it takes time for sufficient biomass to grow and compensate for the initial emissions released through land-use change and pesticide and fertiliser use, after which CO2 absorption results in net negative emissions.

What role does National Grid assume BECCS will play in reaching net zero by 2050?

FES 2020 has used public consultations and research recommendations to generate assumptions of economy-wide CO2 emissions and provide context for its four future power sector scenarios. Of these four scenarios, one does not achieve net zero while the remaining three meet this target by 2050 at the latest with one reaching it by 2048. All three net-zero scenarios assume residual emissions of about 52MtCO2 by 2050, predominantly as a result of difficulties in decarbonising waste, aviation, shipping, and agriculture and land-use. In each of these scenarios it is assumed that all residual emissions will be offset by negative emissions in the power sector entirely as a result of the use of BECCS.

To achieve these emissions reductions, the three net-zero scenarios see 600-1,200MW BECCS capacity introduced between 2027 and 2029, reaching 7,800-9,600MW capacity by 2050. BECCS is projected to absorb 49-61MtCO2 from the atmosphere each year and contribute 8-11% (51-64TWh) of total electricity supply power by 2050.

What is the issue with the amount of BECSS in FES 2020?

Each of FES 2020’s net-zero scenarios sees the immediate generation of negative emissions as BECCS capacity is increased. In doing so National Grid assumes that all of the biomass used in BECCS is inherently carbon neutral. However, biomass feedstocks that can be considered inherently carbon neutral are a very small subsection of commercial forestry wastes and are incidental products of the forestry sector – their availability is determined by economic factors and cannot be generated to meet a demand. Furthermore, the time taken for newly planted forests to mature and produce these inherently carbon neutral supplies of biomass means that the scalability of forest-biomass is limited between now and 2050.

The scalability problem is recognised in FES 2020’s biomass supply scenarios, built on modelling of future domestic and global biomass availability by the Committee on Climate Change (CCC), which see some increases in biomass through improved forest-management, but almost entirely rely upon the conversion of around 1Mha of UK land (equivalent to 7% of total UK agricultural land) to energy crop production to meet net-zero by 2050. Reaching net-zero by 2048 would additionally require the UK to greatly increase imports of biomass, relying on global conversion of 200Mha of land – an area the size of Greenland – to energy crop production if the UK were not to exceed its ‘equal share’[1] of global biomass supply, as defined by the CCC (around 1% of global trade).

Although it is technically possible to achieve these various supply scenarios, given the enormous scale of land they require for energy crop production, they are littered with very significant implications around food competition, water consumption, pesticide use, and biodiversity impacts. To achieve a genuinely sustainable supply of biomass, all of these considerations need to be addressed and satisfied – a task that would require significant research into and monitoring of best-practice in biomass consumption, as well as comprehensive multilateral policy and legislation to ensure its enforcement.

Furthermore, the production of bioenergy crops may not always be the best use of land to generate negative emissions. Once the carbon costs of pesticide and fertiliser use, as well as those of harvesting and transportation have been factored in, the realised negative emissions of bioenergy crops in BECCS may be lower than if the same land was used for another carbon-absorbing activity such as planting natural forests, especially across the short time between now and 2050.

Ember has explored the assumptions behind biomass ‘carbon neutrality’ in our recent report The Burning Question – and recommended the inclusion of biomass into UK carbon pricing.

The policy risks associated with FES

The timeline of BECCS deployment and achieving net-zero are based on the assumption that BECCS delivers instant negative emissions. However, given the limited supply of ‘inherently’ carbon neutral forestry wastes and the unavoidable time delay in generating large-scale negative emissions through the growth of bioenergy crops, achieving instant negative emissions is very unlikely. As a result, there is a high risk that the FES 2020 scenarios will not, in reality, deliver net-zero emissions by 2050.

According to FES 2020, BECCS must come online in the coming decade, meaning that the conversion of land to energy crop production and establishment of supply chains of these crops, both domestically and internationally, must begin imminently if not today. However, the significant sustainability and governance challenges of building such supply chains puts the deliverability of this time-line at risk.

By 2050, not only is BECCS projected to provide 8-11% of total power supply, but also to provide a significant share of dispatchable power to the UK grid. Given the serious issues with National Grid’s assumptions of the scale and feasibility of BECCS capacity, relying on BECCS to play such a vital role in the energy mix is a high risk and ‘high-regrets’ strategy.

The scale of carbon emissions BECCS is assumed to mitigate, and the climate impact of slow decarbonisation for which it supposedly compensates, may set a dangerous precedent – that lower ambitions for decarbonising societies can be permitted on the basis that BECCS can make up for any carbon shortfall. FES 2020 does not provide a detailed breakdown of the origins of the 52MtCO2 residual emissions that must be abated by BECCS in 2050, however recent modelling by the CCC suggests that the main contributors will be agriculture and aviation. Although these sectors are difficult to decarbonise due to technological and efficiency constraints, some further degree of abatement is possible through behavioural and consumer change. Therein lies the moral hazard of BECCS, there is a risk that the assumed availability of negative emissions will permit policy-makers to avoid serious consideration of more ambitious and far-reaching policies of societal decarbonisation and defer proper confrontation of climate risks.

National Grid does not provide an explanation for the timeline of BECCS deployment in FES 2020 and why BECCS capacity has to be scaled up at such pace. Given that the initial deployment of BECCS in all FES 2020 net-zero scenarios closely coincides with the end of biomass subsidies for Drax (the UK’s largest biomass electricity generator), it is worth considering whether National Grid’s timelines for BECCS deployment are overly influenced by the availability of biomass infrastructure looking for a new business model, rather than being guided by selection of the most effective and timely carbon mitigation strategy.

What are the learnings?

Recently BECCS has become one of the most popular methods of generating negative emissions among policy-makers in the climate community. However, as in the case of FES 2020, this status has been acquired through a number of flawed assumptions about the effectiveness and deployability of BECCS. It is essential to understand that BECCS is not a single scalable technology – it is a highly nuanced process that can only achieve negative emissions in specific circumstances and should be treated as such in climate-modelling and policy work. It would be useful for National Grid to clarify the justifications of all of its assumptions around biomass use and BECCS deployment in future editions of FES to provide readers with a better appreciation of the risks associated with its net-zero scenarios.

The CCC have calculated that expanding UK forests by 30,000ha each year from today would contribute 14 MtCO2 of removals per year by 2050. Conversion of the 1Mha of land set aside for BECCS in FES 2020 to forests would see a doubling of these removals by 2050. Although on paper BECCS generates greater negative emissions from the same land, to sacrifice 14 MtCO2 of risk-free removals by growing energy crops for BECCS instead of planting forests, would require a degree of confidence that a nuanced and immature technology such as BECCS simply cannot yet provide.

BECCS may well have a role in future climate strategies but it is very unlikely to make meaningful contributions at the levels envisaged by FES 2020. Given the complexity surrounding BECCS, its deployment and scale-up should be treated with great caution. However, even with the addition of 1Mha of forests, without the use of BECCS all FES 2020 net-zero scenarios see significant residual carbon emissions  by 2050.

It is important then, that National Grid develop net-zero scenarios that achieve significantly lower residual emissions and require minimal abatement from bioenergy in order to highlight to policy-makers the limits of techno-fixes and the scale of societal change that may be required to decarbonise the economy and deliver a balanced power sector by 2050.

[1] CCC scenarios assume the UK accesses a share of the global tradable biomass resource equivalent to its share of global primary energy consumption. This ‘equal’ share is estimated to be around 1.1% in 2050. The scenarios assume the UK utilises its own domestic tradable sources of biomass and then imports additional resources until this equal share has been achieved.