Global potential and impacts of terrestrial carbon sequestration measures

Transcription

1 Global potential and impacts of terrestrial carbon sequestration measures Pete Smith Professor of Soils & Global Change, FRS, FRSE, FRSB Institute of Biological & Environmental Sciences University of Aberdeen, Scotland, UK NAS Terrestrial Carbon Sequestration Webinar, 14 th September

2 Need for negative emissions post-paris 87% of all IPCC scenarios consistent with 2ᵒC use Greenhouse Gas Removal Fuss et al. (2014); Smith et al. (2016a) 2

3 Summary of the carbon cycle impacts of different NETs I J K Smith et al. (2016b) 3

4 4 Smith (2016); Smith et al. (2016a)

5 Soil C & biochar mitigation potentials Biochar (Woolf et al., 2010) Technical potential = 1.8 Gt Ceq/yr Potential accounting for competition for non-waste biomass = 0.7 Gt Ceq/yr Soil C sequestration (Smith et al., 2008; Smith, 2012) Technical potential = 1.3 Gt Ceq/yr Economic potential at US$/tCO 2 eq = Gt Ceq/yr Smith (2016) 5

6 Impact / limit summary for SCS and biochar NET Realistic (max) global C removal (GtCeq./yr) Additional land requirement (Mha) Additional water requirement (km 3 /yr) Mean (max) nutrient impact (Mt N, P, K/yr) SCS 0.7 (1.3) 0 0 N:56, P:14, K:10.5 (N:104, P:26, K:19.5) Biochar 0.7 (1.3) N:21, P:7, K:49 (N:31, P:13, K:91) Albedo impact (unitless) Energy requirement (max) (EJ/yr) Estimat ed cost (B$) to -35 (-65) 130 Main limits: SCS lower potential than some NETs, low impacts on land, water, albedo and energy positive impact on nutrient retention. Low cost potential cost benefits. Biochar Some additional land requirements and albedo impacts; positive impact on nutrient retention and energy generation. Relatively high cost. Smith (2016) 6

7 NETs consistent with 2 C target at 3.3 GtC-eq./yr in 2100 or mean (max) implementation NET Global C removal (GtCeq./yr in 2100) Mean (max), land requirement (Mha in 2100) Estimated energy requirement (EJ/yr in 2100) Mean (max), water requirement (km 3 /yr in 2100) Nutrient impact (ktn/yr in 2100) Albedo impact in 2100 Investment needs (BECCS for electricity / BECCS for biofuel; B$/yr in 2050) BECCS Variable Variable 138 / 123 DAC 3.3 Very low (unless solar PV used for energy) None None >> BECCS EW 0.2 (1.0) 2 (10) (1.5) None None >BECCS AR 1.1 (3.3) 320 (970) Very low 370 (1040) 2.2 <<BECCS (16.8) Negative; or reduced GHG benefit where not negative Smith et al. (2016a) 7

8 Natural C sequestration Griscom et al. (2017) PNAS (in final revision) 8

9 Impact / limit summary for NETS Biochar SCS Smith et al. (2016a); Smith (2016) 9

10 How do land based NETs compare to engineered NETs? Smith, Friedmann et al. ( forthcoming) UNEP EGR 10

11 The data upon which global assessments are based is surprisingly thin!... green = relatively high confidence / low uncertainty in the estimated range, red = relatively low confidence / high uncertainty in the estimated range, and orange = medium confidence / uncertainty in estimated range Smith et al. (2016a) 11

12 Conclusions Soils have a moderate potential for delivering negative emissions ( Gt C yr -1 for soils; 0.7 Gt C yr -1 for biochar) Afforestation / Reforestation have a similar potential depending on scale of deployment Fewer negative externalities for soil sequestration compared to some other land-based NETs. Some potential for additional sequestration through natural carbon sequestration (particularly through wetland / coastal margin and degraded land restoration) There are many co-benefits (helping meet SDGs, food security etc.) of soil-based NETs The 4 0 / 00 Initiative could be a vehicle to allow soil NETs to be delivered 12

13 References Fuss, S., Canadell, J.G., Peters, G.P. et al Betting on negative emissions. Nature Climate Change 4, doi: /nclimate2392. Griscom, B.W., Adams, J., Ellis, P. et al Natural pathways to climate mitigation. Proceedings of the National Academy of Sciences, USA (in revision). Smith, P Soil carbon sequestration and biochar as negative emission technologies. Global Change Biology 22, doi: /gcb Smith, P., Davis, S.J., Creutzig, F. et al. 2016a. Biophysical and economic limits to negative CO 2 emissions. Nature Climate Change 6, doi: /nclimate2870. Smith, P., Haszeldine, R.S. & Smith, S.M. 2016b. Preliminary assessment of the potential for, and limitations to, terrestrial negative emission technologies in the UK. Environmental Science: Processes & Impacts 18, doi: /C6EM00386A. 13

14 Thank you for your attention 14