9.4 Carbon capture


Achieving net-zero society-wide emissions is the result of both deep reductions across all sectors and the application of techniques to capture the equivalent of remaining emissions. The use of carbon capture in net-zero scenarios is largely unavoidable without reducing the provision of some services, mainly in agriculture and for industrial processes, as explained in Chapter 8. 

Carbon capture can take different forms and be completed with various technologies and processes. A more detailed description of these technologies and processes is provided in Chapter 12. However, for the current discussion, three categories of applications are distinguished: the capture of emissions in industrial combustion and processes; capture in negative-emissions operations, which in the model means BECCS, hydrogen production or electricity generation; and direct-air capture, which is meant to refer to the capture of emissions from the atmosphere with technologies other than natural processes like biomass photosynthesis. Each of these is addressed below.

Figure 9.7 – Captured emissions #

While the total quantity of emissions captured in each scenario and at different points in time for each of the three categories varies according to the pace of emission reductions, all scenarios converge around the net-zero point between 155 and 167 MtCO2e captured (Figure 9.7). For capture in the industrial sector, the overwhelming share of captured emissions comes from combustion (around 77% for the sector), which highlights the difficulties of competitively transforming heat production with current technologies. 

The importance of production facilities equipped with carbon capture varies across industrial sectors. Cement production makes up the largest share of the total, with 62% deriving from CCS-equipped plants by 2050 in NZ50. In contrast, only 30% of production from the pulp and paper sector comes from such plants and a similar share of chemical industries uses them. For the latter two industrial sectors, this means that, compared with cement, a much larger share of the emissions must be reduced through fuel switching.

The next category of carbon capture application is bioenergy with carbon capture and storage (BECCS). More than 95% of capture in power and energy production comes from BECCS applications in electricity generation and hydrogen production (Figure 9.8), with the rest provided by natural gas powerplants with CCS installations. BECCS electricity generation already rapidly increases in NZ50 (11 MtCO2e) and NZ45 (22 MtCO2e) in 2030, but BECCS hydrogen production quickly catches up before constituting a roughly equal share by 2040 in these scenarios (around 57 MtCO2e, similar to BECCS electricity). Part of this is the result of low hydrogen demand in the first decade due to the novelty of this vector, but once demand takes off, the possibility of achieving negative emissions makes it, along with BECCS electricity production, an important source to compensate remaining emissions elsewhere.

Figure 9.8 – Bioenergy with carbon capture and storage (BECCS) #

Therefore, although very little biomass is used for electricity production as a proportion of the total, significant negative emissions are obtained from biomass-fired plants with CCS. In fact, electricity production with carbon capture becomes the main use of biomass (827 TJ in NZ50 for 2050), a share roughly equal to that of the biomass used for hydrogen production (750 TJ), as noted in the previous sections. 

Finally, the results show that reaching net-zero requires direct-air capture. In reality, between 15 and 33 MtCO2e needs to be directly removed from the atmosphere to accommodate residual emissions in net-zero scenarios. While this is a small part of all emissions captured, the very limited experience with concrete DAC applications means that this result should be treated with care since considerable uncertainties remain given the cost of operating this technology. In fact, capture with DAC appears only in 2050 in the model, reflecting the associated high cost. It should be noted that for 2060, more DAC is used for NZ45 compared with NZ50, suggesting that technological innovation in carbon capture technology—for low-carbon technologies more generally—continues to evolve past the net-zero point, bringing more innovative solutions for emission control.

Figure 9.7 also shows that between storage and utilization in the industrial and energy production sectors, the main route for captured emissions (over 99%) is storage. DAC and BECCS electricity, shown on the chart, also result in a similar share of storage. On the one hand, this shows the limited reutilization potential of CO2 in terms of cost, with storage being the cheaper option. On the other, it also illustrates the main constraint on reutilization, which more often than not results in the release of the captured emissions at some point downstream after the utilization of the captured CO2. 

General observations:

  • The large quantity of carbon capture required to reach net-zero can be achieved in various ways and its use to capture industry emissions is uneven across sectors.
  • DAC is essential in all net-zero scenarios, and the need to use it largely depends on the amount of residual emissions, as well as BECCS electricity generation and hydrogen production.