Temporary Carbon Storage and a Case Study for Orchards · Nitrogen kg N 0 22 45 90 135 179 224 224...
Transcript of Temporary Carbon Storage and a Case Study for Orchards · Nitrogen kg N 0 22 45 90 135 179 224 224...
© Alissa Kendall - 2015
Temporary Carbon Storage and a Case Study for Orchards
Alissa Kendall, PhD
Associate Professor
Civil & Environmental Engineering
• Part 1: Life cycle assessment, carbon footprints, global warming potentials and a proposal for warming potential alternatives
• Part 2: A case study for California almond orchards and the effect of including temporary carbon storage
Life Cycle Assessment (LCA)
• A method for characterizing and quantifying environmental sustainability
• Applies a “cradle-to-grave” perspective when analyzing products or systems
W, P
W, PW, P
Life cycle assessment
• Evaluates a product or system throughout its entire life cycle
Raw Material
Acquisition
Material Processing
Manufacturing UseEnd-of-
Life
RecycleRemanufacture Reuse
M,E
W, P
W, P
M,E M,E M,E M,E
M = MaterialsE = EnergyW = WasteP = Pollution
= Transport
Recycle
LCA of Greenhouse Gases (GHGs)
• While traditional LCA considers a whole range of environmental impact categories, a GHG LCA, or carbon footprint, only considers the GHG caused by or emitted from the system
• A full LCA allows us to understand potential trade-offs across environmental impact categories
Standards and protocols for LCA and Carbon Footprints
• The ISO (International Organization for Standardization) has an LCA standard (ISO 14040 series)
• The British Standards Institute (BSI) has a commonly cited Carbon Footprint Standard, PAS2050
• And many others…
GHG Inventory vs Carbon Footprint
• Inventories are typically annual snapshots of GHG emissions that occur at a site or over a region
• Carbon footprints examine the life cycle GHG emissions of a product, process, region, or even policy
• GHG Inventories, Carbon Footprints and LCA use the same indicator – CO2-equivalent (CO2e) emissions – to condense all GHG emissions or credits into a single indicator
What are the rules for carbon sequestration in most of these methods?
• For carbon to be considered ‘stored’ or ‘sequestered’ it has to be removed from the atmosphere for a minimum of 100 years
• The PAS2050 standard, along with most other carbon accounting protocols use this rule
• Though PAS2050 does acknowledge that carbon storage less than 100 years could be accounted for.
Offsets and Carbon Footprinting
Standards
Global Warming Potentials
• Nearly all methods use the Intergovernmental Panel on Climate Change’s (IPCC’s) 100-year GWPs (GWP100) to turn non-CO2 gases into CO2-equivalent (CO2e)
• Typically sum CO2e emissions over the entire life cycle of the product/service/policy evaluated. This is true not just for LCA…
The Global Warming Potential Indicator
• Most current practices use the IPCC’s Global Warming Potentials (GWP), ignore when GHG emissions occur
• Even though the 100 year time horizon is explicitly used/mandated
• Ignoring when emissions (or sequestration) occur can cause bias in comparisons of difference technologies or mitigation strategies
Time Matters
What are GWPs and how are they calculated?
Radiativeforcing (RF)
Cumulative RF (CRF)
Atmosph-eric warming
Tempera-ture
Change
Climate Change
End-point Impacts
Impact Chain for Global Warming
Global Warming Potentials
0
22
0
TH
i
iTH TH
COCO
RFdt
GWP
RF dt
CRFCRF
Integral of Radiative Forcing for some GHG
Integral of RadiativeForcing for CO2
AT
AT
CRF and normalized of 1 kg of CO2, CH4, and N2O
265
28
1
year
year
Observe how normalizing gets us to
GWPs as reported by the IPCC
1 kg of each GHG at Year 0
Timing matters
• Consider three technologies/practices with the same total life cycle GHG emissions and a 40 year life time
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0 50 100
Cu
mu
lati
ve R
adia
tive
Fo
rcin
g
Years
All emissions occur at year zero
Emissions Profile (30% in years 0-1, 70% Operations)
Emissions Profile (5% in years 0-1, 95% Operations)
Using GWP these would have identical
CO2e values
CO
2 E
mis
sio
ns
Time
Time
Time
CO
2 E
mis
sio
ns
CO
2 E
mis
sio
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Indic
ato
r of Clim
ate
Change
Timing Matters
• There are countless scenarios where emissions timing matters in LCA and carbon footprints
• There are at least four that come up frequently1. In LCA emissions are summed over the life cycle of
a product and presented as a single outcome
2. When amortizing upfront emissions
3. When crediting a material or product with recycling (i.e. future avoided emissions)
4. When CO2 is sequestered for less than 100 years(carbon storage is a special case of emissions timing –where you remove atmospheric CO2 and then release at certain point in time.)
Goals for New Methods Development
1. Develop CO2e metrics that include timing
• Keeping the ‘CO2e’ unit to facilitate adoption and to comply with existing policies, standards and protocols
2. Develop an easy way for practitioners and policymakers to calculate/use metrics
Alternative metrics/approaches for carbon dioxide equivalency factors that account for timing
• Time-adjusted warming potentials (TAWPs)• Yields units CO2e equivalent ‘today’ for various
analytical time horizons and GHGs • Kendall (2012) International Journal of LCA
• Time correction factors (TCFs) for amortized CO2 emissions
• Useful for emissions intensity estimates (e.g. gCO2e/MJ, gCO2e/mi, etc.)
• Kendall et al. (2009), and Kendall and Price (2012) Environmental Science & Technology
• Note: There are other proposed metrics, many of which rely on similar underlying principles
Time Adjusted Warming Potential (TAWP)
2
2
0
0
AT
i
i
AT
CO
CO
RFdtCRF
GWPCRF
RF dt
2
0
0
( )
( )
AT y
i
AT
CO
RF t dt
TAWP
RF t dt
Emission occurring yyears in the future
Source: Kendall (2012)
How is this useful?
• If a tree sequesters approximately 40 kg CO2 per year for 50 years, how much sequestration credit should it receive?
• Thus when comparing the value of different sequestration credits, timing may play an important role in determining preferences for one strategy over another.
0
500
1000
1500
2000
2500
No Timing Timing with100-year AT
Timing with50-year AT
kg CO2e Sequestered
Source: Kendall (2012)
User-friendly excel tool for TAWP calculation
NOTES
Greenhouse Gases to be modeled Y/N year CO2 CH4 N2O SF6 PFC-14 PFC-116 HCFC-22
CO2 Y 0 0 20 -2.67E+04 -26684.94
CH4 N 1 -95.5452 30 -2.65E+04 -26536.07
N2O N 2 -9162.89 50 -1.36E+04 -13615.66
SF6 N 3 -5359.95 100 -6.18E+03 -6179.42
PFC-14 N 4 -3802.94 500 -1.14E+03 -1140.43
PFC-116 N 5 -2949.79 No TAWP 0.00E+00
HCFC-22 N 6 -2410.16
7 -2037.76
TCF for amortize emissions? Y 8 -1765.19
If Y, what is the amortization period? 15 9 -1557
Y 10 -1392.79
N 11 -1259.93
12 -1150.23
13 -1058.11
14 -979.653
15 -912.035
16 -853.151
17 -801.413
18 -755.592
19 -714.729
20 -678.059
21 -644.97
22 -614.96
23 -587.619
24 -562.607
25 -539.637
26 42646.7
27
28
29
30
31
This optional step takes approximately 1 minute to run and
will take you to a new page.
Total time-
corrected
CO2e
Time horizon of emissions profile must be less than or
equal to 99 years.
Enter emissions by year below, be sure to use consistent units.
Blanks will be treated as zeros.
Any emissions occuring after the specified analytical time
horizon (see column P) will be treated as zeroAnalytical Time
HorizonCO2 as time-
corrected
CO2e
CH4 as time-
corrected
CO2e
N2O as time-
corrected
CO2e
SF6 as time-
corrected
CO2e
PFC-14 as time-
corrected
CO2e
PFC-116 as
time-
corrected
CO2e
HCFC-22 as
time-
corrected
CO2e
Step 1. Clear Emissions Profiles
Step 2. Run TAWP Calculator
OPTIONAL Step 3. Draw CRF Charts
NOTES
Greenhouse Gases to be modeled Y/N year CO2 CH4 N2O SF6 PFC-14 PFC-116 HCFC-22
CO2 Y 0 0 20 -2.67E+04 -26684.94
CH4 N 1 -95.5452 30 -2.65E+04 -26536.07
N2O N 2 -9162.89 50 -1.36E+04 -13615.66
SF6 N 3 -5359.95 100 -6.18E+03 -6179.42
PFC-14 N 4 -3802.94 500 -1.14E+03 -1140.43
PFC-116 N 5 -2949.79 No TAWP 0.00E+00
HCFC-22 N 6 -2410.16
7 -2037.76
TCF for amortize emissions? Y 8 -1765.19
If Y, what is the amortization period? 15 9 -1557
Y 10 -1392.79
N 11 -1259.93
12 -1150.23
13 -1058.11
14 -979.653
15 -912.035
16 -853.151
17 -801.413
18 -755.592
19 -714.729
20 -678.059
21 -644.97
22 -614.96
23 -587.619
24 -562.607
25 -539.637
26 42646.7
27
28
29
30
31
This optional step takes approximately 1 minute to run and
will take you to a new page.
Total time-
corrected
CO2e
Time horizon of emissions profile must be less than or
equal to 99 years.
Enter emissions by year below, be sure to use consistent units.
Blanks will be treated as zeros.
Any emissions occuring after the specified analytical time
horizon (see column P) will be treated as zeroAnalytical Time
HorizonCO2 as time-
corrected
CO2e
CH4 as time-
corrected
CO2e
N2O as time-
corrected
CO2e
SF6 as time-
corrected
CO2e
PFC-14 as time-
corrected
CO2e
PFC-116 as
time-
corrected
CO2e
HCFC-22 as
time-
corrected
CO2e
Step 1. Clear Emissions Profiles
Step 2. Run TAWP Calculator
OPTIONAL Step 3. Draw CRF Charts
Demonstration of the tool
Part 2: Almond LCA
• UC Davis research team:
Elias MarvinneyDoctoral Student, Horticulture and Agronomy
Alissa KendallDept. of Civil and Environmental Engineering
Sonja BrodtAgricultural Sustainability Institute
Funded by the Almond Board of California
Scope of our study
Key Inputs and Outputs
Flows Unit/haYears
0 1 2 3 4 5 6 7-25 Clearing
Inputs
Fert
ilize
r Nitrogen kg N 0 22 45 90 135 179 224 224 --Potassium kg K2O 0 22 45 90 135 179 224 224 --
Boron g B 0 448 448 448 448 448 448 448 --Zinc kg Z 0 5.6 5.6 5.6 5.6 5.6 5.6 5.6 --
Irri
gati
on
Micro-sprinkler or Sprinkler (45% of area)
m3x103 0 2.8 5.3 8.1 8.3 11.2 11.2 11.2 --
Drip (25% of area) m3x103 0 1.7 2.7 5.8 8.3 8.3 8.3 8.3 --Flood (30% of area) m3x103 0 3.3 6.4 9.7 13.0 13.0 13.0 13.0 --
Oth
er Saplings # 128 1.3 1.3 1.3 1.3 1.3 1.3 1.3 --Pollination hives 0 0 0 4.9 4.9 4.9 4.9 4.9 --
Outputs
Alm
on
d Y
ield
Non-flood irrigated - 70% of total area
kg kernel
0 0 0 203 407 813 1017 2242 --
Flood irrigated - 30% of total area
kg kernel
0 0 0 203 407 712 1017 2466 --
Weighted average yieldkg
kernel0 0 0 203 407 783 1017 2309 --
Co
-P
rod
uct
s Shells kg 0 0 0 448 897 1793 2242 2242 --Hulls kg 0 0 0 897 1793 3587 4483 4483 --
Woody Biomass (at 32% moisture)
kg 0 30 94 147 185 215 239 260 35073
Carbon is accumulated and stored in trees (and soils) over the orchard life cycle. At the end of the orchard life cycle, trees are removed and used for bioenergy production (95%). When combusted all the atmospheric carbon stored in the tree is released.
Reminder - the Life Cycles of Inputs are Modeled too
• Life cycle inventory datasets are required for each material or process included in the LCA
• The inventory datasets reflect the life cycle of each component material or process, for example:• Assuming diesel fuel is part of the life cycle, the diesel LCI
dataset would reflect the following• This means we always examine energy starting at the original
resource…we track all the energy it takes to make the energy we consume
Petroleum Exploration
and Extraction
Crude oil transportation
Crude oil refining
Delivery of Diesel Fuel
M, E
W, P
M, E
W, P
M, E
W, P
M, E
W, P
Co-products from the orchard: Biomass Generation for Electricity
• Each kilogram of green (wet) biomass generates approximately 2.57 MJ of electricity • that means 1 ha of orchard produces more than
25,000 kWh of electricity
• 95% of orchard clearing biomass goes to biopower(remaining 5% are mulched in field or burned), while prunings are either mulched and left in-field or burned. • Thus prunings do not store carbon for significant
time periods.
Co-products and their uses
Two ways to handle co-products
• Displacement methods – where we model co-products as if they are preventing the production of products that are substitutable in the market
• Economic allocation – where we simply allocate all the inputs among the various co-products using economic value
• For almonds (and biofuels) this leads to very different outcomes
Biomass power from orchard waste ‘displaces’ the average kWh of grid electricity used in California
2012 Total System Power in Gigawatt Hours
Fuel Type
CaliforniaIn-State
Generation (GWh)
Percent of CaliforniaIn-State
Generation
Northwest Imports (GWh)
Southwest Imports (GWh)
California Power Mix
(GWh)
Percent California Power Mix
Coal 1,580 0.8% 561 20,545 22,685 7.5%
Large Hydro
23,202 11.7% 12 1,698 24,913 8.3%
Natural Gas
121,716 61.1% 37 9,242 130,995 43.4%
Nuclear 18,491 9.3% - 8,763 27,254 9.0%
Oil 90 0.0% - - 90 0.0%
Other 14 0.0% - - 14 0.0%
Renewables
34,007 17.1% 9,484 3,024 46,515 15.4%
Unspecified Sources of Power
N/A N/A 29,376 20,124 49,500 16.4%
Total 199,101 100.0% 39,470 63,396 301,966 100.0%
Business as Usual
Co-Product Treatment with Displacement• Since co-products have some value to them and
displace some other product in the market, some “credit” to the primary product (almonds) should be assigned
With Co-Product in Market
We give credit
to almonds for
avoiding silage
Hulls
6%
94%
KernelsDairy Feed
BiopowerBedding
Alternative: Economic Allocation
Raw Brown-skin Almond
Shells
Woody BiomassHulls
Per Hectare Shell HullProcessing
Biomass
Orchard Clearing Biomass
Orchard Pruning Biomass
Kernel
Lifetime Production Mass (kg ha-1)
22,221 76,783 1,289 37,024 19,157 49,183
Total Value (2014 $) 166 15,843 2 124 0 269,617
Proportion of Total Value:
0.06% 5.54% 0.00% 0.04% 0.00% 94.35%
Almond Production System (Orchard +
Hulling and Shelling)
Results by life cycle stage
Emission or
Energy Use
Co-Product Credits
(displacement)Net
Economic
allocation
GWP100 (kg CO2eq) 1.63 -1.63 -1.81×10-3 1.53
Total Energy (MJ/10) 3.50 -1.17 2.33 3.30
Scenario Analysis showed large possible ranges for results – some of these are up to grower practice, others are not
5.36
0.68
-2.14
0.64
0.761.04
0.37
0.64
-1.86
0.16
4.30
1.57
-3
-2
-1
0
1
2
3
4
5
6
kg
CO₂e
kg
ker
nel
-1
Mean
BaU
Scenario Results
a.52.67
23.31
32.96
8.13
23.31 20.86
23.31
12.05
35.12
16.02
35.12
0
10
20
30
40
50
60
MJ
kg
ker
nel
-1
Mean
BaU
Scenario Results
b.
Best case –Gasification and stable C in biochar
Pump type is a key factor here…a
Carbon Accounting Rules and New Ideas
• Carbon accounting rules state that carbon must be stored for 100 years to be counted as sequestration – so previous figure did not include carbon storage
• What happens when we include carbon storage using TAWP?
• Remember this is CO2e today
Water Almond Orchard Cropping System
Atmospheric CO2
Stored C
Time
Agro-chemicals
Diesel / Equipment
Biomass for
power
Edible Food Supply
Transport
Electricity
Crude oil
Natural Gas
Co
mb
ustio
n
Emissio
ns
Bio
geoch
emical
Emissio
ns
Carbon Flows over an Orchard Life Cycle
Biogenic carbon in above ground orchard biomass
Carbon in trees is
lost at the end of the
orchard lifespan
when removed trees
are used in biomass
power plants.
Though carbon is
also stored in below
ground biomass (not
burned for power),
no sequestration is
included because of
high uncertainty in
values.
*Note that this method includes accounting for biogenic carbon emissions
CRF of Carbon in above ground biomass
-1E-09
-8E-10
-6E-10
-4E-10
-2E-10
0
2E-10
0 100 200 300 400 500
W-y
r/m
2
years
CRF of CO2 temporarily stored in above-ground orchard biomass
Q: What happens when we account for temporary carbon storage in orchard trees and soils?A: It reduces CO2-equivalancy by 1/5
*Note, this reflects field-to-farm gate
Conclusions
• Almond orchards are relatively short-lived compared to other orchard crops• C-storage credits might be even more significant
• Interesting trade-offs when displacement calculations are used for electricity co-products (near-term displacement will displace more fossil CO2 than future displacement)
• Temporary carbon storage is an issue that the forestry industry has also been confronting
• We are working on adding short-lived climate forcing pollutants to the calculation tool
Questions?
My contact info, in case you have questions later:
Alissa Kendall
References
• Kendall, A., Marvinney, E., Brodt, S.B., Zhu, W. (under review) Life cycle-based assessment of energy use and greenhouse gas emissions in almond production - Part 1: Analytical framework and baseline results Journal of Industrial Ecology
• Marvinney, E., Kendall, A., Brodt, S.B. (under review) Life cycle-based assessments of energy use and greenhouse gas emissions in almond production - Part 2: Uncertainty analysis through sensitivity analysis and scenario testing Journal of Industrial Ecology
• Kendall, A. 2012. Time-adjusted global warming potentials for LCA and carbon footprints. The International Journal of Life Cycle Assessment 17(8): 1042-1049.
• Kendall, A. and L. Price. 2012. Incorporating Time-Corrected Life Cycle Greenhouse Gas Emissions in Vehicle Regulations. Environmental Science & Technology 46(5): 2557-2563.
• Kendall, A., B. Chang, and B. Sharpe. 2009. Accounting for Time-Dependent Effects in Biofuel Life Cycle Greenhouse Gas Emissions Calculations. Environmental Science & Technology 43(18): 7142-7147.
Suggested additional reading for temporary carbon storage
-Brandão, M., A. Levasseur, M. F. Kirschbaum, B. Weidema, A. Cowie, S. Jørgensen, M. Hauschild, D. Pennington, and K. Chomkhamsri. 2013. Key issues and options in accounting for carbon sequestration and temporary storage in life cycle assessment and carbon footprinting. The International Journal of Life Cycle Assessment 18(1): 230-240.
-Levasseur, A., P. Lesage, M. Margni, L. Deschênes, and R. Samson. 2010. Considering Time in LCA: Dynamic LCA and Its Application to Global Warming Impact Assessments. Environmental Science & Technology 44(8): 3169-3174.