The potential role of negative CO2 emissions in solving climate

problem

A.Revokatova and A.Ryaboshapko, Institute of Global Climate and Ecology,

Moscow, Russia

Approaches to solving climate problem:

1. Reduction of CO2 emission

2. Removing of CO2 from the atmosphere - negative CO2 emission by CDR technologies (passive influence on Earth climate system)

3. Solar radiation management - SRM (active influence on Earth climate system)

Introduction• It is very likely that only emissions reduction techniques

can not solve the climate problem • SRM methods cause a priori rejection of society, based on

the idea of undue influence on the nature and uncertainty about who will manage the process

Goal: to estimate the potential of different CDR methods.Question: Is it possible to solve climatic problem by a combination of “emission reduction” methods and methods of negative emissions without application of SRM?

18501868188619041922194019581976199420120

2

4

6

8

10 Coal GasOil Sum

Emis

sion

, GtС

/yea

r

20002032206420962128216021922224225622880

500

1000

1500

2000

RCP8.5RCP6.0RCP4.5RCP2.6550 ppm(v) ~ (+2°С)

СО

2,

pp

m(v

)

RCP8.5 – radiative forcing=8.5 W/m2 in 2100

RCP6.0 – radiative forcing=6 W/m2 in 2100

550 ppm ~ Δ2ᵒC

Δ2ᵒC – acceptable increment

During the industrial period in the Earth's atmosphere has received about 1,400 Gt CO2.

• For climate projections it is important to calculate cumulative emission to the atmosphere - the accumulated amount of CO2 over a long period.

• Cumulative negative emission - accumulated amount of removed CO2 from the atmosphere.

• Humankind can archive negative emission by using CDR. But for visible result CDR methods must be applied during decades.

• Global task - removal 1200 GtCO2 (24 GtCO2 / year for 50 years) from the atmosphere, to end up with a CO2 concentration of 350 ppm (McLaren, 2012)

Potentials of CO2 conservation

Reservoir of conservation Capacity, Gt

СО2

Conservation time, years

Exhausted oil-gas reservoirs 700 – 900 > 1000

Geological structure 2*102 -1,1*104 > 1000

Deep alkaline solutions 103 - 105 Not limited

Ocean 103 – 4*104 300 - 1500

Solid inert substances 200 - 1500 500

Categories of negative emissions methods

I – Terrestrial or oceanic methods that have a high potential and are not limited by the presence of the used components (CO2

conservation in coal; BECCS; Direct Air Capture; Electrolytic capture of СО2 ; Soil mineralization; Ocean mineralization; Cultivation of algae in the ocean; Intensification of vertical transport in

the ocean).

II – Methods are limited by the presence of the used components (Afforestation and reforestation; Biomass conservation in the deep ocean; Biomass

conservation in the mires and land; Landuse adaptation and improving restoration of peatlands).

III – Others methods with low CO2 capture potential (less then 1 Gt СО2/year) (Increasing of wood used in construction

CO2 capture from seawater Production of magnesium-silicate cement).

Scenarios of “negative emissions” methods application

• Potential of CO2 capture• Readiness to application

• Technological inertia• Absence of experience

• Transport infrastructure for delivery of CO2 to the storage place

Changing of negative emission speed and cumulative negative emission values were traced up to 2300. Start-time and duration of the deployment were evaluated with dependence of the complexity of technology and the degree of readiness for widespread use.

Scenarios for 13 the most potential CDR methods

General scheme of negative emission technology

Air without CO2

Air+ CO2 Re - emission of CO2

Резервуар захоронения СО2

ВоздухReservoir of СО2conservation

CDR

CO2

conservation

Calculation of cumulative negative emission (CNE)

• S – current speed of CO2 capture, Gt CO2 /year

• CNE – CO2 mass in the reservoir, Gt CO2

• Re-emission -reverse flux from reservoir is proportional to CO2 mass in reservoir

The exponential growth of the NE speed from the beginning of the deployment (S0 = 0) up to achievement of the estimated maximum value (Smax) was set for most of the methods. An exception is the aforestation, for which linear growth of NE speed was set in the deployment phase.

Резервуар захоронения СО2

ВоздухCNE

CDR

Si

Amount of current annual NE = Si = exp (k1 * Ni) – 1Smax = exp (k1 * Nmax) – 1 (Nmax – number of years for S= Smax )

k1 = ln (Smax +1) / Nmax

linear growth: Si = Smax / Nmax

Re-emission

CNE (cumulative negative emission) = CS(i)

CS(i+1) at each time step is calculated as:

CS(i+1) = CSi + Si – (CSi + Si) * k2

re-emissionk2 - describe the process of re-emission;

K2=1/, where - the average lifetime of CO2 in the reservoir

Si = Smax

The second phase of NE emission method deployment:CS(i+1) = CSi + Smax – (CSi + Smax) * k2.

CO2 conservation in charcoal

Scenario of deployment:- Maximum annual NE - 10 Gt CO2/ year (*)- Start of the application - 2030 - The exponential growth until 2120 - Sustainable use of the method to 2300 - The lifetime of coal in soils - 450 years (**)

(*)• IPCC, IPCC Expert Meeting on Geoengineering. 2012• Lenton T.M. and Vaughan N.E., The radiative forcing potential of different climate geoengineering options. 2009• McGlashan N.R., Workman M.H.W., Caldecott B., Shah N., Negative Emission Technologies, 2012• McLaren D., A comparative global assessment of potential negative emissions technologies. 2012• Meadowcroft J., Exploring negative territory carbon dioxide removal and climate policy initiatives. 2013• Woolf D., Amonette J. E., Street-Perrott F. A., et al., Sustainable biochar to mitigate global climate change. 2010

(**)Jaffé R., Yan Ding, Niggemann J. et al., Global Charcoal Mobilization from Soils via Dissolution and Riverine Transport to the Oceans. 2013Lehmann J., Gaunt J. and Rondon M., Bio-char sequestration in terrestrial ecosystems – a review. 2006

200020382076211421522190222822660

2

4

6

8

10

Flu

x С

О2,

Gt/

year

200020382076211421522190222822660

300

600

900

1200

1500

1800 Chart Title

CN

E, G

t С

О2

Annual NE flux Cumulative negative emission

CO2 conservation in charcoal

Afforestation and reforestationLimited factor – free areasScenario of deployment:- Maximum NE of 1.5 Gt CO2 (*)- Afforestation from 2030 to 2050. - Annual uptake of 1.5 Gt of CO2 from 2050 to 2150 years. - After 2150 emission flux is equal to absorption

Afforestation 2030 - 2050

Trees growth2050 - 2150

Mature and dead woodafter 2150

(*)• Canadell J.P. and Raupach M.R., Managing Forests for Climate Change Mitigation. 2008• McLaren D., A comparative global assessment of potential negative emissions technologies. 2012• Ning Zeng, King A.W., Zaitchik B., Wullschleger S.D., et al., Carbon sequestration via wood harvest and storage: An assessment of its

harvest potential. 2012• Smith L.J. and Torn M.S., Ecological limits to terrestrial biological carbon dioxide removal. 2013• Sitch S., Brovkin V., von Bloh W., et al., Impacts of future land cover changes on atmospheric CO2 and climate. 2005

200020392078211721562195223422730

0.4

0.8

1.2

1.6 Chart Title

Flu

x, G

t С

О2/

год

Annual NE flux Cumulative negative emission

200020402080212021602200224022800

20

40

60

80

100

120 Chart Title

CN

E, Г

т С

О2

Afforestation and reforestation

Total negative emission of the all considered NE methods

200020412082212321642205224622870

20

40

60

80Chart Title

Flu

x, G

t С

О2/

year

200020392078211721562195223422730

3000

6000

9000

12000

15000 Chart Title

CN

E, G

t С

О2

Max 60 Gt СО2/year

Annual NE flux Cumulative negative emission

2300 KNE 13000 Gt СО2

Contribution of each method to total negative emission

Method Years2050 2100 2200 2300

CO2 conservation in charcoal 9 21 15 14BECCS 2 14 15 15Direct Air Capture 0 12 44 45Soil mineralization 12 15 9 9Electrolytic capture of СО2 0 1 1 1Ocean mineralization 0 2 3 3Ocean firtilization 27 15 4 3Cultivation of algae in the ocean 0 0 2 2Intensification of vertical transport in the ocean 0 1 3 4Afforestation and reforestation 17 10 2 1Landuse adaptation and improving 20 3 0 0Increasing of wood used in construction 8 4 1 1Production of magnesium-silicate cement 3 3 1 1 Decreasing of СО2, ppmv 11 84 790 1530

RCP8.5 combined with all methods of negative emission

Blue line - CO2 concentration pathway (ppm(v)) according to RCP8.5 scenario. When all possible CDR techniques are applied, CO2 concentration in the atmosphere rises more slowly and begins to decline in about 2180 (red line). Yellow line - CO2 concentration level which corresponds to acceptable global temperature rise (+2C at 550 ppm(v)). Colored area indicates “dangerous” period, when global temperature will exceed the acceptable level.

1 24 47 70 93 1161391621852082312542770

500

1000

1500

2000

2500RCP8.5RCP8.5-NECritical level

СО

2 co

ncen

trat

ion

, ppm

(v)

RCP6.0 combined with all methods of negative emission

1 19 37 55 73 91 1091271450

500

1000

1500

2000

2500

RCP6.0 RCP6.0-NE

Critical level

СО

2 co

nce

ntr

atio

n, p

pm

(v)

Results are too optimistic…

• It is very unlikely that all methods will be deployed simultaneously

• The thermal inertia of the ocean "stretchs" zone of dangerous excess CO2

• Imbalance between the reservoir and source-reservoir runoff ("recoil" effect)

• It is necessary to consider the totality of greenhouse gases

Conclusions• According to our simulations since 2050 and up to 2280 even the

totality of CDR methods (or "negative emissions") cannot provide the stabilization of global temperature at an acceptable level while the most dangerous scenario of CO2 concentration increase is considered (RCP8.5).

• Similar results were obtained when RCP6.0 scenario is used, but duration of “dangerous” period would be much less – about 50 years.

• Only SRM techniques will be able to solve the problem during this period. Thus mankind will have to be ready to use all three approaches (emission reduction, CDR and SRM) to prevent the risk of inadmissible global temperature rise since the middle of this century.

Thank you for your attention!