The need for and limits to

negative emissions

Sabine Fuss & Pete Smith On behalf of 30+ collaborators from many institutes and GCP

Mercator Research Institute on Global Commons and Climate Change, Berlin

&

Institute of Biological & Environmental Sciences, University of Aberdeen

Our Common Future under Climate Change Conference, July 7-10 2015, Paris

The need for negative emissions

• IPCC AR5: Achieving 2C is

still possible, but it entails

huge contributions from

bioenergy - in most scenarios

combined with Carbon

Capture & Storage to go

“negative“.

• BECCS need 2-10 Gt

CO2/yr in 2050 5–25% of

2010 CO2 emissions

• Current global mean removal

of CO2 by ocean and land

sinks is 9.2 ± 1.8 Gt CO2 and

10.3 ± 2.9 Gt CO2, resp.

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Data: CDIAC/GCP/IPCC/Fuss et al 2014

The need for negative emissions cont’d

3

Based on Figure TS.17, IPCC, WG3, AR5, 2014.

How can we go (net) negative?

The technology most widely used in climate stabilization

scenarios of AR5 is Bioenergy combined with CCS (BECCS).

4

Source: Applied Energy Handbook, Wiley.

Other negative emissions options:

• Afforestation (also in AR5, see next slide)

• Increases in soil carbon storage (biochar…)

• Direct air capture (coming up)

• Enhanced weathering (coming up)

Land-use and management changes:

• Saturation of CO2 removal over time

• Sequestration reversible (terrestrial carbon stocks inherently vulnerable to disturbance)

Geo-engineering options:

• Quicker and cheaper to ramp up

• Embody a much larger scale of mostly unknown risks

• Not able to deal with other consequences of increased CO2 concentrations such as ocean acidification

Afforestation / Reforestation (AR)

Humpenöder et al. (2014)

Picture: http://en.wikipedia.org/wiki/File:Forest_ialoveni.jpg

Summary of

the carbon

cycle impacts

of different

NETs

Smith et al. (2015)

Factors potentially enhancing or limiting the global

capacity for NETs

Smith et al. (2015)

Impact of NETs on

land, water,

nutrients, albedo,

energy and cost –

all expressed on a

per-t-C-eq. basis

Smith et al. (2015)

NETs consistent with 2C target at 3.6 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

(km3/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 3.6 310 -170 1910 Variable Variable 138 / 123

DAC 3.6 Very low

(unless solar

PV used for

energy)

170 10-330 None None >> BECCS

EW 0.2 (1.0) 2 (10) 46 0.3 (1.5) None None >BECCS

AR 1.1 (3.3) 320 (970) Very low 370 (1040) 2.2

(16.8)

Negative;

or

reduced

GHG

benefit

where not

negative

<<BECCS

Smith et al. (2015)

Impact / limit summary for NETS

Main limits:

• DAC – cost, energy

• EW – vast areas – logistics

• Afforestation – albedo, water, competition for land

• BE/BECCS – water, competition for land Smith et al. (2015)

Conclusions

• Negative emissions of 3.6 GtC-eq./yr in 2100 are possible with BECCS and DAC

• EW and AR can provide less negative emissions than this in 2100

• All NETs have limits / downsides and none is a magic bullet

• Need more R&D and pilot projects – then to see if technology is scalable Most probably will need to look into other NETs to complement BECCS and AR, e.g. DAC, EW

• Improve governance to ensure sustainable implementation of NETs

• Safe storage needed, in addition to storage from fossil CCS.

• An over-reliance on NETs in the future, if used as a means to allow continued use of fossil fuels in the present, is extremely risky since our ability to stabilise the climate at <2C declines as cumulative emissions increase (Kriegler et al., 2014, Luderer et al., 2012)

• A failure of NETs to deliver expected mitigation in the future, due to any combination of biophysical and economic limits examined here, leaves us with no “Plan B”

• “Plan A” must be to reduce GHG emissions aggressively now

Smith et al. (2015)

Contact

Please also visit http://www.cger.nies.go.jp/gcp/magnet to learn more about GCP‘s research initiative „Managing Global Negative Emissions Technologies“

Sabine Fuss Mercator Research Institute on

Global Commons and Climate Change gGmbH

Torgauer Str. 12–15 | 10829 Berlin | Germany

tel +49 (0) 30 338 55 37 - 101

mail fuss@mcc-berlin.net

web www.mcc-berlin.net

Pete Smith Institute of Biological and Environmental Sciences, University of Aberdeen

23 St Machar Drive, Aberdeen, AB24 3UU, UK

tel +44 (0)1224 272702

mail pete.smith@abdn.ac.uk

web www.abdn.ac.uk/ibes/

people/profiles/pete.smith

Backup Material

Dienstag, 25. August 2015 13

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The Extent of BECCS Use in IPCC AR5

Scenarios

• 101 of the 116 430-480ppm scenarios rely on BECCS.

• About 67% of these have a BECCS share in primary energy exceeding 20% in 2100.

• BUT: many uncertainties remain. Can we really bet on BECCS?

Source: Fuss et al. (2014), Nature Climate

Change.