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Growing biofuels over abandoned croplands in the former USSR. Trade-offs between sequestration and bioenergy benefits. Nicolas VUICHARD (1,2) Philippe CIAIS (2) Luca BELELLI (3) Riccardo VALENTINI (3) (1) CIRED – Nogent (France) LSCE/IPSL – Saclay (France)

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trade offs between sequestration and bioenergy benefits

Growing biofuels over abandoned croplands in the former USSR

Trade-offs between sequestration and bioenergy benefits

Nicolas VUICHARD (1,2) Philippe CIAIS (2)

Luca BELELLI (3) Riccardo VALENTINI (3)

(1) CIRED – Nogent (France)

LSCE/IPSL – Saclay (France)

University of Tuscia – Viterbo (Italy)

slide2
Abandoned cultivatedlands are suitable candidates for bioenergy production (Field, 2008)
    • Do not compete with food security
    • Dot not induce a carbon debt
  • Bioenergy competes with soil C sequestration but has a higher environmental impact
  • Is there an optimal onset time to startbiofuel cultivation, given future climate change and management practices?
slide3
The end of the USSR resulted into one of the largest crop abandonment of the 20th century

- 20 Mha

20 Mha

Hurtt et al., 2006

slide4
Soil carbon changes are impacted by

+ Climate

+ Climate

++ Management

+ Climate

++ Land-use legacy

Soil carbon

Natural grassland

Crops

Recovering grassland

1950’s

1990’s

slide5
A potential of 0.5 GtC could be sequestered

into the abandonned 20 Mha of croplands

New soil C data from abandonned crop fields in Russia

goals
Goals
  • Carbon benefit of sequestration by natural steppe recovery
  • Carbon benefit of biofuel due to both:

- biofuel can also sequester below ground C

- biofuel harvest substitutes to Fossil Fuel

  • Compare recovery vs. biofuel option

-> Use a spatially explicit process-based

model to address these questions

the orchidee global carbon water energy model
The ORCHIDEE global carbon-water-energy model

meteorological forcing

output variables

sensible & latent heat fluxes, CO2 flux, net radiation

rain, température, humidity,

incoming radiation, wind, CO2

ORCHIDEE

SECHIBA

energy & water cycle

photosynthesis

Dt = 1 hour

LAI,

roughness,

albedo

soil water,

surface temperature,

GPP

STOMATE

vegetation & soil carbon cycle

(phénologie, allocation,…)

LPJ

spatial distribution

of vegetation

(competition, fire,…)

vegetation

types

Dt = 1 day

Dt = 1 year

prescribed vegetation

NPP, biomass,

litterfall

vegetation

types

including crops in orchidee
Including crops in ORCHIDEE

Daily data assimilation of crop parameters into ORCHIDEE

ORCHIDEE global model

Generic ecosystem C dynamics

withland-use disturbances

scale : local => regional => global

1 year => 1000 years

Same Gridded climate and soil data

Brisson et al. (2002)

STICS agronomic Model

Library of ≠ crop varieties

LUE growth

Biomass allocation and yield

Water and Nitrogen demand

No soil C balance

scale : field , months

LAI

Root profile

Irrigation needs

including land use change land management
Including land-use change & land management
  • Input (spatially explicit) land-use statistics FAO

Orchidee

Orchidee-Stics

time

Recovery period

Cultivation period

1951

1993

2000

  • Input N-fertilizer addition statistics USDA

on arable land of former USSR

  • Simple agricultural parameterization

Harvest -> grains + straw exported

Tillage -> Mean Residence Time of soil C pools faster by 30%

sink regional mean
Sink regional mean

Croplands

100% instant. aband.

Net Carbon Balance changes

Orchidee-Stics

Orchidee

agriculture

recovering grassland

1951

1993

2000

If croplands all maintained after 1993

If croplands all abandoned in 1993

Realistic abandonment scenario

gC m-2 yr-1

sink spatial patterns
Sink spatial patterns

Regional C gain from 1993 to 2000 373 gC per m2

Some grid points in the south are net sources, because NPP of steppes is lower than soil carbon input from former crop fields

-> we really need spatially explicit modelling

towards realistic estimates
Towards realistic estimates

64 TgCin 8 years over 17 Mha

C gain from 1993 to 2000 per m2

Map of the C storage from 1993 to 2000

Abandoned cropland area from 1993 to 2000

sensitivity tests
Sensitivity tests
  • No fertilization during cultivation period

=> +37%

  • No tillage during cultivation period (no impact on soil decomposition)

=> -25%

  • 10% of straw remained on plot

=> -15%

modelling biofuel on the steppe
Modelling Biofuel on the steppe
  • Ethanol production from natural grassland biomass as in Tilman et al. (2006)
    • 1 gC substitutes 0.42 gC
  • Scenario: an abrupt switch to biofuels in 1990
  • Compare scenario with sequestration by calculating the crossing timetcross
  • tcross = time at wich biofuels deliver more C benefits than sequestration
biofuel production vs steppe recovery sequestration
Biofuel production vs steppe recovery sequestration

tcross

Total Bioenergy production

Soil C sequestration in natural steppe

Soil C sequestered with Bioenergy production

timing of bioenergy implementation
Timing of bioenergy implementation
  • If we wait 60-years after abandonment to install biofuels ?
  • Trajectories change... but same tcross

tcross

Bioenergy production

Soil C sequestration

Soil C released with bioenergy production

sensitivity to c initial stocks
Sensitivity to C initial stocks
  • Condition: MRT must remain constant over time
  • This condition could be challenged if

Warming accelerates decomposition

Tillage must be increased for cultivating biofuels

Never tilled

Tilling t0=just after abandonment

Tilling t0=60 years after abandonment

tcross

tcross

tcross

conclusions
Conclusions
  • Biofuel production looks suitable on abandoned croplands of former USSR
  • Energy = 0.23 EJ per year (0.05% of world demand)
  • Net Carbon balance of biofuels

sink of 0.56 Gt C over 60 years

- Carbon storage in biofuel soils = 0.08 GtC

- Fossil carbon substituted = 0.48 Gt C

  • Net Carbon Storage if steppe recovery

sink of0.3 Gt C over 60 years

slide23

Crossing date = 11 years, at which biofuels have a better carbon balance than steppe recovery

Crossing date is relatively insensitive to timing of implementation under some conditions (no soil warming)

Quick benefits

perspectives
Perspectives
  • Generalize to other ecosystems
  • Priority = sugarcane in Brazil
  • Calculate maps of carbon debt in the eventuality of forest clearing
  • Welcome collaborations with real experts !