IEA Greenhouse Gas R&D Programme



GHGT-14 Session 1D – Negative Emissions (1) & IPCC 1.5

GHGT-14 kicked off this morning with one of the keynotes giving the delegates an overview of the recently published IPCC Special Report on Global Warming of 1.5°C (SR1.5). The presentation was delivered by none other than the IPCC's Vice Chair, Dr Thelma Krug. Dr Krug first presented the statistics of the report, which was prepared by 91 authors and review editors from 40 different countries. More than 6,000 scientific references have been cited and a total of 42,001 expert and government review comments have been received and addressed. Dr Krug then presented the 4 illustrative model pathways, which all use carbon dioxide removal (CDR) to a larger or lesser extent. In addition, the relative contribution of different CDR options, such as e.g. bioenergy with carbon capture and storage (BECCS) and afforestation/reforestation (AR), can vary greatly.Some pathways, like P1 and P2 (see figure below) can do with very small amounts or no BECCS at all. However, they rely heavily on other technology innovations and demand side changes, which will likely be as uncertain or hard to achieve as a fast ramp up of large-scale BECCS deployment

Dr Krug's keynote presentation provided an excellent introduction for one of the sessions that were to follow in the technical programme: session 1D on negative emissions. In this session, strategies on how to achieve the negative emissions required for stringent emissions reductions targets were discussed in more detail.

The first presentation by Kristin Onarheim discussed ways to help the forest industry turn carbon negative, via application of carbon capture and storage (CCS) and/or carbon capture and utilisation (CCU) in pulp and paper mills. CCS cases were investigated for 4 different capture rates, varying from 5-90%. General observations were that only sustainable biomass feedstocks will lead to truly negative emissions and that the CCU cases will not achieve negative emissions. Among the CCU cases, formic acid production proved to be the most feasible option, or the only option with a business case. In case of CCU methanol production, it is cheaper to do CCS with 90% capture rate, rather than capturing only 5% and converting it to methanol. This is mainly due to the high sensitivity of power-to-x concepts towards electricity prices. In conclusion, a shift from a carbon positive to a carbon negative mill is possible at fairly low cost.

In the next talk, Anders Lyngfelt elaborated what the effects of leakage rates for different CDRs are. Even if all stored CO2 would leak, CO2 storage would still provide a significant reduction of atmospheric CO2 concentration and a delay of peak emissions.

Habiba Daggash's modelling results show that BECCS can provide up to 3x greater system value in the UK energy system than direct air capture and storage (DACCS). In addition, both BECCS and DACCS act as a direct offset for unabated emissions from combined cycle gas turbine (CCGT) power plants, thus providing a direct value transfer. If both BECCS and DACCS are available, then usually BECCS deployment has preference, due to its higher system value.

Jia Li introduced the attendees of the session to the current situation of BECCS in China. There are currently 83 projects on biomass co-firing shortlisted for approval, from a total of about 200 initial submissions. An important condition for those projects is that the biomass used should be sourced within 50km of the related power plant and that only residues that do not compete with food production are used. A current challenge in China is to match the CO2 sources and sinks for BECCS, as emission sources are mainly in the east whereas the storage opportunities are mainly in the west.

The last presentation in the session was delivered by Etsushi Kato, who presented results from the integrated assessment model GRAPE with regards to BECCS. GRAPE includes both BECCS and AR and covers 15 different regions. Several BECCS scenarios were considered: full, fuel-only, power-only and no BECCS, each for 2 different supply levels of biomass. Wood and other residues dominate biomass supply in the power sector. For fuel-only BECCS, sequestration effectiveness is reduced, to the point that stringent emissions reduction targets become infeasible at limited supply levels. Another finding of the modelling work is that for the default supply scenario, global cropland extension can be limited to <0.4Gha, even for stringent emissions targets. Less stringent targets can be achieved without BECCS but would still require high bioenergy use, large-scale AR and H2 deployment. 

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