11.4 Overarching net-zero technological challenges


11.4.1 Compensation of non-energy emissions remaining in 2050

All reports extensively discuss the challenges specific to remaining emissions outside of energy use, that is, industrial processes, agriculture, waste, and forests. In respect of industrial processes, the US and UK discuss the key importance of CCS to reduce process emissions. FR, however, insists on the need for the government to encourage disruptive technologies for process emissions.

Outside of industrial process emissions, each reports pays a very different degree of attention to each sector. In terms of agriculture, the UK is much more detailed on measures to consider for nitrogen use efficiency (loosening soil compaction on cropland, use of precision farming and variable rate fertiliser application, more use of organic residues as in anaerobic digestion, better accounting for nutrients in livestock manures, and increased use of legume crops); livestock measures (improving the feed digestibility of cattle and sheep, improving animal health and fertility, and increasing the feed conversion ratio through the use of genetics can reduce methane emissions); manure management (better storage, management and application of animal wastes on land can reduce manure management emissions, better floor design and use of air scrubbers); and improving the thermal efficiency of agricultural buildings through retrofit or new build. The EU puts forth some of the same measures but the overall list is less detailed. In turn, FR uses a similar list although it insists more on reducing energy demand. The US is much less detailed, merely mentioning increases of annual uptake of carbon stored permanently in forests and agricultural soils 

In relation to forests and land use, the UK insists on planting perennial energy crops and short-rotation forestry to increase soil carbon sequestration. It also diminishes the requirement to apply fertilizer, thus avoiding N2O emissions. The US discusses the need for a concerted effort to deploy agricultural and/or forestry land sink enhancement measures, while the EU focuses mainly on reforestation and better management of all types of vegetative land. France mentions a better management of silviculture to maximize substitution and storage of carbon in wood products (mainly increasing wood harvest and orienting it toward more long-term usage and increasing recycling and valorisation of wood products at end of life).

Finally, as concerns waste management, the UK and FR discuss biogas, although in rather general terms, whereas US makes no mention of it. Only the EU pays significant attention to both biogas consumption and production possibilities.

11.4.2 The role of carbon capture

Carbon capture plays a significant and multifaceted role in all net-zero reports considered here. Even with deep reductions across all sectors, some emissions will remain and must therefore be compensated to reach a carbon neutral economy. As a result, CCS and CCU are used extensively in all four reports. The US sees them in particular in cement production, gas- and biomass-fired power generation, natural gas reforming, and biomass derived fuels production. All the other reports also discuss carbon capture in industrial applications, especially for process emissions and for applications where electrification is not available.

Negative emissions technologies like BECCS are used differently and with varying importance across reports. The EU says they will be negligible, while the UK plans for 6% of power generation and the US sees an important role for BECCS, specifically in hydrogen production.

The use of direct air capture is limited in the UK, FR and the EU but significant in some scenarios from the US, especially if biomass use is constrained. Finally, the US is more explicit on storage and transport infrastructure for CO2, which is discussed in more general terms in the other reports.