For a finite land area, wheat straw based BECCS would remove more CO₂ from the atmosphere. Risks need to be mitigated by, in part, prioritizing emission reductions.
The CCC plays an integral role in shaping UK government climate policy. While the UK government itself is yet to set a definitive target for BECCS or GGRs, the net zero scenarios published by the CCC offer the clearest indication of the scale of BECCS that the UK government is likely to pursue. It is important to note that the CCC scenarios provide no detail as to the type of feedstock, land requirement, efficiency of the BECCS power plants, or CAPEX required. Without a clear understanding of these crucial parameters it remains challenging to conduct a robust assessment of the cost and benefits of pursuing, and indeed relying upon, BECCS. This chapter defines these missing key characteristics, based on wheat straw being the optimal feedstock choice due to its carbon efficiency presented in section 4.3.
In compiling the scenarios, the CCC drew on the IPCC IAM pathways, and the UK Energy Research Centre (UKERC) conducted an evidence review in order to inform the CCC’s BECCS projections.
The CCC’s ‘Further Ambition’ scenario has BECCS providing around 51 MtCO₂/yr of removals in 2050, of which the largest share – 35.4 MtCO₂/yr – is provided by BECCS-to-power, rather than BECCS to hydrogen or biofuels. This target is the starting point illustrated in Figure 8, which populates the system dynamics diagram of Figure 3 with CCC values, as well as those calculated here. The values in blue within Figure 8 are taken directly from the CCC report, namely: 112 TWh of resource would be required to deliver the target, from a fleet size of 5 GW generating 41 TWh of electricity, at a cost of £158/tCO₂.
5.1 Implications of a highly efficient BECCS fleet
As discussed in Chapter 3, the efficiency of BECCS power plants has a significant impact on the required CO₂ capture and storage subsidy, the fleet CAPEX and land requirement. The fleet average efficiency is simple to infer: dividing the power production (41 TWh) by the embodied energy of the feedstock (112 TWh). As can be seen in Figure 8, the implied efficiency is therefore 36.6 per cent. As discussed in section 3.1, the Drax wood pellet plant has an efficiency of around 36.2 per cent, which if converted to a BECCS power plant would likely fall to around 20.9 per cent due to the energy penalty of the CCS equipment. This implied efficiency indicates a future BECCS fleet that is significantly more advanced than a Drax-like BECCS power plant – requiring an energy efficiency increase of 15.7 percentage points. This should be compared to the historical efficiency improvement of thermal power plants in Europe, which increased by 6.9 per cent over the 20 years between 1990 and 2010. Furthermore, examining the UKERC evidence review, the range of BECCS efficiency provided to the CCC was between 20 per cent to 38 per cent, based on the range within the literature, again indicating the CCC is implicitly planning for a highly advanced future BECCS fleet by 2050, which historical efficiency improvements indicate may be challenging to achieve.
The relatively high efficiency of 36.6 per cent has wider system implications. As discussed in section 3.1, higher efficiencies result in less feedstock being combusted in each BECCS power plant (assuming baseload operation). As such, the fleet size (5 GW) required to achieve the 35.4 MtCO₂/yr target would be larger than if the facilities were less efficient but generate more power (41 TWh), and hence derive greater power revenues. This has two subsequent consequences. Firstly, the CAPEX to build the BECCS fleet would be greater. Based on a BEIS 2020 publication that defines an nth of a kind BECCS power plant costing £2,793/kW, which implies a CAPEX of £14 billion for the fleet. Secondly, assuming a wholesale electricity price of £40/MWh, the power revenues of the BECCS fleet would be around £1.6 billion/yr. It is presumably due to these relatively high power revenues (due to the higher power efficiency) that the CCC defined a relatively low cost of removals (£158/tCO₂), which would likely take the form of a carbon price type subsidy.
