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					Life cycle assessment of biochar systems

         Kelli G. Roberts, Brent A. Gloy, Stephen Joseph,
               Norman R. Scott, Johannes Lehmann
      Department of Crop and Soil Sciences, Cornell University


                   Northeast Biochar Symposium
                         UMass Amherst
                       November 13, 2009
What is Life Cycle Assessment (LCA)?
   Methodology to evaluate the environmental burdens
    associated with a product, process or activity throughout
    its full life by quantifying energy, resources, and emissions
    and assessing their impact on the global environment.
   LCA has been standardized by the ISO (International
    Organization for Standardization).



materials          manufacture           use          end of life

                    Life cycle of a product
Goals of the LCA
   To conduct a cradle-to-grave analysis of the
    energy, greenhouse gas, and economic inputs
    and outputs of biochar production at a large-scale
    facility in the US.

   To compare feedstocks (corn stover, yard waste,
    switchgrass).
Scope: the functional unit
   The functional unit:
       A measure of the performance or requirement for a
        product system.
       Provides a reference so that alternatives can be
        compared.


   Our functional unit:
       The management of one tonne of dry biomass.
System boundaries
 Fossil fuels
 production

                                      Pyrolysis facility
 Electricity
 production                                                    Heat exhaust
                                                                                             Biochar   T      Soil
                               T                                                                           application
   Biomass collection                Shredding             Drying     Slow pyrolysis
                                                                                             Syngas
       T                                                                                      heat
                                                                                                           T (-)
                                                                                             product
                         T
Farm equipment,                                                                                             Fertilizers
 agrochemicals           (-)         T                                                 (-)
                               Construction                                   Natural gas production
               Compost          materials                                         & combustion




Dashed arrows with (-) indicate avoided processes.
The “T” represents transportation.
Biochar with heat co-product
                            Installation at Frye Poultry Farm,
                            West Virginia

                            capacity of 300 kg dry litter hr-1




    www.coaltecenergy.com
LCA of biochar – industrial scale
   Plant throughput 10 t dry biomass hr-1
       Runs at 80% capacity


   The slow pyrolysis process has four co-
    products:
       Biomass waste management
       Biochar soil amendment
       Bioenergy heat production
       Carbon sequestration
Energy flows: feedstock to products




Sankey diagram, per dry tonne stover
Feedstocks
   Corn stover
       Late and early harvest (15% and 30% mcwb).
       Second pass collection, harvest 50% above ground biomass.

   Yard waste
       45% mcwb
       No environmental burden for production.
       Assumed to be diverted from large-scale composting facility.

   Switchgrass
       12% mcwb
       Scenarios A and B to capture range of GHG flows associated
        with land-use change
  Feedstocks (cont.)
    Switchgrass A
          Lifecycle emissions model (Deluchi), informally models land-
           use change.
          Assumes land conversion predominantly temperate grasses
           and existing croplands, rather than temperate, tropical or
           boreal forests.
          Net GHG of +406.8 kg CO2e t-1 dry switchgrass harvested.

    Switchgrass B
          Searchinger et al (2008) global agricultural model.
          Assumes land conversion in other countries from forest and
           pasture to cropland to replace the crops lost to bioenergy
           crops in the U.S.
          Net GHG of +886.0 kg CO2e t-1 dry switchgrass harvested.

Deluchi, M. “A lifecycle emissions model (LEM)”; UCD-ITS-RR-03-17; UC Davis, CA, 2003.

Searchinger, T.; et al. Science 2008, 319 (5867), 1238-1240.
Pyrolysis and biochar parameters
  Feedstock properties, pyrolysis process yields, and biochar properties for various
  biomass sources
                                          Late         Early           Switch     Yard
  Property                               stover        stover          grass      waste
  Moisture content, wet basis             15%          30%             12%         45%
  Ash content (wt.% DM)                    5.6          5.6             4.6        4.5
  C content of feedstock
                                           45           45              48             47
  (wt.% DM)
  Lower heating value
                                         16000        16000            17000      18000
  (MJ t-1 DM)
  Feedstock to heat energy
                                                                37%
  efficiency
  Yield of biochar (wt. %)               29.60         29.60           28.80      29.63
  C content of biochar (wt.%)            67.68         67.68           63.09      65.89
  Stable portion of total C in
                                                                80%
  biochar
  Improved fertilizer use efficiency
                                                                7.2%
  (for N, P, K)
  Reduced soil N2O emissions
                                                                50%
  from applied N fertilizer
Energy balance
                             Energy (MJ t -1 dry feedstock)
                         0        2000          4000          6000

        stover   cons.                   Net = + 4116
         Late

                                                                     agrochems
                 gen.                                                field ops
                                              Net = + 3044           drying
                 cons.
        stover
        Early




                                                                     chipping
                 gen.
                                                                     biomass trans
        Switch




                                          Net = + 4899               plant constr
        grass




                 cons.
                                                                     other
                 gen.
                                                                     syngas heat
                                               Net = + 4043
        waste




                 cons.
        Yard




                                                                     avoid fos fuel
                 gen.                                                avoid compost


    All feedstocks are net energy positive.
    Switchgrass has the highest net energy.
    Agrochemical production and drying consume largest proportion of energy.
    Biomass and biochar transport (15 km) consume < 3%.
    “Other” category includes biochar transport, plant dismantling, avoided fertilizer
     production, farm equipment, and biochar application.
GHG emissions balance
                                                                    -1
                                       Greenhouse gases (kg CO 2e t dry feedstock)
                                               0   300       600            900




             stover
                                       emit.                  Net = - 864         LUC & field
              Late                                                                emiss.
             stover                  reduct.                                      agrochems
                                                               Net = - 793
             Early


                                       emit.                                      field ops
                                     reduct.                                      other
             waste grass B grass A




                                                              Net = - 442
             Yard Switch Switch




                                       emit.                                      stable C
                                     reduct.                                      avoid foss fuel
                                       emit.                                      gen. & comb.
                                                                    Net = + 36    land-use seq.
                                     reduct.
                                                                                  reduced soil
                                       emit.                                      N2O emiss.
                                                              Net = - 885         avoid compost
                                     reduct.



   Stover and yard waste have net (-) emissions (greater than -800 kg CO2e).
   However, switchgrass A has -442 kg CO2e of emissions reductions, while B actually has
    net emissions of +36 kg CO2e.
   “Other” category includes biomass transport, biochar transport, chipping, plant
    construction and dismantling, farm equipment, biochar application and avoided
    fertilizer production.
                                                                                               -1
                                                                  Greenhouse gases (kg CO 2e t dry feedstock)


GHG emissions
                                                                          0   300       600            900




                                       stover
                                                                  emit.                  Net = - 864         LUC & field




                                        Late
                                                                                                             emiss.


(cont.)
                                                                reduct.                                      agrochems




                                       stover
                                                                                          Net = - 793




                                       Early
                                                                  emit.                                      field ops
                                                                reduct.                                      other




                                        waste grass B grass A
                                                                                         Net = - 442




                                        Yard Switch Switch
                                                                  emit.                                      stable C
                                                                reduct.                                      avoid foss fuel
                                                                  emit.                                      gen. & comb.
                                                                                               Net = + 36    land-use seq.
                                                                reduct.
                                                                                                             reduced soil
                                                                  emit.                                      N2O emiss.
                                                                                         Net = - 885         avoid compost
                                                                reduct.




    Biomass and biochar transport (15 km) each contribute < 3%.
    The stable C sequestered in the biochar contributes the largest
     percentage (~ 56-66%) of emission reductions.
    Avoided natural gas also accounts for a significant portion of reductions
     (~26-40%).
    Reduced soil N2O emissions upon biochar application to the soil
     contributes only 2-4% of the total emission reductions.
                                                                                                             +$35




                                      stover
                                       Late
    Economic                                                                                    -$17




                                      grass A
    analysis
                                                                                                     +$8




                                      Switch
                                                                                            -$18




                                      grass B
                                                                                            -$28




                                       Switch
   High revenue scenario
           $80 t-1 CO2e                                                                   -$30

   Low revenue scenario



                                      waste
                                      Yard
           $20 t-1 CO2e                                                                                          +$69
                                                                                                        +$16

                                            -120       -80      -40        0     40        80        120       160       200
                                                                  cost ($ t-1 dry feedstock)
                                                   biomass collection                 biomass transport
                                                   pyrolysis                          biochar transport
                                                   biochar application                lost compost revenue
                                                   tipping fee                        avoided compost cost
                                                   biochar P & K content              biochar improved fertilizer use
                                                   carbon value                       syngas heat


            The high revenue of late stover (+$35 t-1 stover).
            Late stover breakeven price is $40 t-1 CO2e.
            Switchgrass A is marginally profitable.
            Yard waste biochar is most economically viable.
            Highest revenues for waste stream feedstocks with a cost associated with current
             management.
Stable C vs. life cycle emissions
        Net profits valuing stable C only ($ t-1 DM)

              ($ t-1 DM)          Late stover   Switchgrass A & B   Yard waste

          High revenue scenario      $13               $17             $44

          Low revenue scenario       -$23              $8              $10




   Yard waste still most profitable
   Stover and switchgrass have switched
Transportation sensitivity analysis
                                             0                                                      6000                                    60



        Net GHG (kg CO2e t-1 dry stover)                                                            5000                                    30




                                                                                                           Net energy (MJ t-1 dry stover)
                                           -200             Net revenue




                                                                                                                                                  Revenue ($ t-1 dry stover)
                                                                                                    4000                                    0
                                           -400
                                                      Net energy                                    3000
                                                                                                                                            -30
                                           -600
                                                                                                    2000
                                                         Net GHG                                                                            -60

                                           -800
                                                                                                    1000
                                                                                                                                            -90


                                  -1000                                                             0
                                                  0          200          400        600   800   1000
                                                                           Distance (km)


    The net revenue is most sensitive to the transport distance, where costs
     increase by $0.80 t-1 for every 10 km.
    The net GHG emissions are less sensitive to distance than the net
     energy.
    Transporting the feedstock and biochar each 200 km, the net CO2
     emission reductions decrease by only 5% of the baseline (15 km).
    Biochar systems are most economically viable as distributed systems
     with low transportation requirements.
Biochar-to-soil vs. biochar-as-fuel
Net GHG
   Biochar-as-fuel: biochar production with biochar
    combustion in replacement of coal are -617 kg
    CO2e t-1 stover
   Biochar-to-soil: -864 kg CO2e t-1 stover
   29% more GHG offsets with biochar-to-soil
    rather than biochar-as-fuel
Biomass direct combustion vs. biochar-to-soil
Net GHG
   Not including avoided fossil fuels:
       Biomass direct combustion: +74 kg CO2e t-1 stover
       Biochar-to-soil: -542 kg CO2e t-1 stover
       Emission reductions are greater for a biochar system than for
        direct combustion

   With avoided natural gas:
       Biomass direct combustion: -987 kg CO2e t-1 stover
       Biochar-to-soil: -864 kg CO2e t-1 stover
       Net GHG look comparable
       However, for biochar-to-soil, 589 kg of CO2 are actually
        removed from the atmosphere and sequestered in soil,
        whereas the biomass combustion benefits from the avoidance
        of future fossil fuel emissions only
       Transparent system boundaries
Conclusions
   Careful feedstock selection is required to avoid unintended consequences
    such as net GHG emissions or consuming more energy than is generated.

   Waste biomass streams have the most potential to be economically viable
    while still being net energy positive and reducing GHG emissions (~ 800
    kg CO2e per tonne feedstock).

   Valuing greenhouse gas offsets at a minimum of $40 t-1 CO2e and further
    development of pyrolysis-biochar systems will encourage sustainable
    strategies for renewable energy generation and climate change mitigation.
                                   Preliminary results:
                                   Mobile unit for stover biochar
                                   Without energy capture
Next steps                         Net GHG = -550 kg CO2e t-1 stover
                                   Net energy = -1000 MJ t-1 stover

   Different biochar-pyrolysis sytems
       Mobile unit
       Small-scale non-mobile, batch units
       With and without energy capture




www.biocharengineering.com            Brazilian type metal kiln, Nicolas Foidl
Next steps
   Developing country scenarios
       Household cook stoves
       Village scale units
       Central plant at biomass source   Pro-Natura in Senegal

   Different feedstocks
       Manures
       Native grasses on
        marginal lands



                                          Cook stoves in Kenya
Acknowledgements
   Cornell Center for a Sustainable Future (CCSF)

   John Gaunt (Carbon Consulting)
    Jim Fournier (Biochar Engineering)
    Mike McGolden (Coaltec Energy)

   Lehmann Biochar Research Group, especially Kelly Hanley,
    Thea Whitman, Dorisel Torres, David Guerena, Akio Enders




                      Thank you!
Feedstock properties, pyrolysis process yields, and biochar properties for various
biomass sources
                                        Late        Early       Switchgra      Yard
Property                               stover       stover         ss          waste
Moisture content, wet basis            15%           30%            12%         45%
Ash content (wt.% DM)                   5.6           5.6            4.6         4.5
C content of feedstock
                                         45           45             48          47
(wt.% DM)
Lower heating value (MJ t-1 DM)        16000        16000           17000      18000
Yield of biochar (wt. %)               29.60        29.60           28.80      29.63
C content of biochar (wt.%)            67.68        67.68           63.09      65.89
Stable portion of total C in
                                                             80%
biochar
Improved fertilizer use efficiency
                                                             7.2%
(for N, P, K)
Reduced soil N2O emissions
                                                             50%
from applied N fertilizer

DM = dry matter
Pyrolysis facility costs
Costs (2007 USD)


Pretreatment
Operating ($ t-1 DM)         $4.77
Capital ($ t-1 DM)           $4.12    $3.6 M Total


Pyrolysis
Operating ($ t-1 DM)         $26.81
Capital ($ t-1 DM)           $12.14   $10.6 M Total
Iron


Total Operating ($ t-1 DM)   $31.58
Total Capital ($ t-1 DM)     $16.26
Total ($ t-1 DM)             $47.84
Costs and revenues per dry tonne of feedstock. Each feedstock has a low and high revenue scenario,
representing $20 and $80 per tonne CO2e sequestered, respectively
                              Late stover              Switchgrass A              Switchgrass B              Yard waste
                           Low              high      Low              High      low              High      low            high
Biochar
P & K content                      18.39                      9.68                        9.68                     10.01
Improved fertilizer use             1.22                      1.18                        1.18                     1.22
C value                     17.28            69.12     8.84             35.36     -0.72            -2.88   17.70           70.80
Energy                             42.81                      55.05                      55.05                     35.20
Tipping fee                         NA                         NA                         NA                       49.09
Avoided compost cost                NA                         NA                         NA                       10.98
Lost compost revenue                NA                         NA                         NA                      -56.03
Feedstock                          -43.46                     -36.89                     -36.89                     NA
Transport
Biomass                             -6.24                     -6.02                      -6.02                      NA
Biochar                             -1.57                     -1.53                      -1.53                     -1.57
Biochar application                 -1.07                     -1.04                      -1.04                     -1.07
Pyrolysis
Operating                          -31.58                     -31.58                     -31.58                   -31.58
Capital                            -16.26                     -16.26                     -16.26                   -16.26


Net value ($)             -17.07            34.77    -18.57            7.95     -30.29           -28.13    15.87           68.97

				
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