1. No category

Temporary Carbon Storage and a Case
Study for Orchards
Alissa Kendall, PhD
Associate Professor
Civil & Environmental Engineering
© Alissa Kendall - 2015
• 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
Life cycle assessment
• Evaluates a product or system throughout
its entire life cycle
M,E
M,E
M,E
M,E
M,E
Raw
Material
Acquisition
Material
Processing
Manufacturing
Use
End-ofLife
W, P
W, P
M = Materials
E = Energy
W = Waste
P = Pollution
= Transport
Recycle
W, P
Remanufacture
W, P
Reuse
W, P 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?
Impact Chain for Global Warming
Radiative
forcing
(RF)
Cumulative
RF (CRF)
Temperature
Change
Atmospheric warming
Global
Warming
Potentials
Climate
Change
End-point
Impacts
Integral of Radiative
Forcing for some GHG
AT
TH
 RF dt
i
GWP
Integral of Radiative
Forcing for CO2
TH  TH
AT

0
0
RFCO 2
CRF

dt CRF
i
CO 2
CRF and normalized of 1 kg of CO2, CH4,
and N2O
Observe how
normalizing gets us to
GWPs as reported by the
IPCC
265
year
1 kg of each
GHG at Year 0
28
1
year
Timing matters
Cumulative Radiative Forcing
0.06
All emissions occur at
year zero
0.05
Emissions Profile (30%
in years 0-1, 70%
Operations)
0.04
0.03
Emissions Profile (5%
in years 0-1, 95%
Operations)
0.02
0.01
0
0
50
Years
100
CO2 Emissions
Indicator of Climate Change
0.07
CO2 Emissions
Using GWP these
would have identical
CO2e values
0.08
CO2 Emissions
• Consider three technologies/practices with the same
total life cycle GHG emissions and a 40 year life time
Time
Time
Time
Timing Matters
• There are countless scenarios where emissions
timing matters in LCA and carbon footprints
• There are at least four that come up frequently
1. 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)
AT
 RF dt
i
GWP 
0
AT
 RF
CO2
0
dt
CRFi

CRFCO2
Emission occurring y
years in the future
AT  y
TAWP 

RFi (t )dt
0
AT
 RF
CO2
0
Source: Kendall (2012)
(t )dt
How is this useful?
• If a tree sequesters approximately 40 kg CO2 per year for 50
years, how much sequestration credit should it receive?
kg CO2e Sequestered
2500
2000
1500
1000
500
0
No Timing
Timing with
100-year AT
Timing with
50-year AT
• Thus when comparing the value of different sequestration
credits, timing may play an important role in determining
preferences for one strategy over another.
Source: Kendall (2012)
User-friendly excel tool for TAWP
calculation
NOTES
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.
Step 2. Run TAWP Calculator
Step 2. Run TAWP Calculator
Step 1. Clear Emissions Profiles
Any emissions occuring after the specified analytical time
horizon (see column P) will be treated as zero
Analytical Time
Horizon
Greenhouse Gases to be modeled
Analytical Time
CO
CH
Horizon
2
4
N2O
SF6
PFC-14
PFC-116
HCFC-22
20
TCF for amortize emissions?
30
If Y, what is the amortization period?
Y
50
N
100
500
No TAWP
Y/N
Y
N
N
N
N
N
N
Y
15
year
0
CO2 as time1
corrected2
3
CO2e 4
5
-2.67E+0467
-2.65E+0489
-1.36E+041011
-6.18E+031213
-1.14E+031415
0.00E+001617
18
19
20
21
22
23
24
25
26
27
28
29
30
31
CO2
CH4
N2O
CH as timecorrected
CO2e
0
4
-95.5452
-9162.89
-5359.95
-3802.94
-2949.79
-2410.16
-2037.76
-1765.19
-1557
-1392.79
-1259.93
-1150.23
-1058.11
-979.653
-912.035
-853.151
-801.413
-755.592
-714.729
-678.059
-644.97
-614.96
-587.619
-562.607
-539.637
42646.7
SF6
PFC-14
PFC-116 HCFC-22
N2O as timecorrected
CO2e
20
SF6 as time30
corrected50
100
CO2e 500
No TAWP
OPTIONAL Step 3. Draw CRF Charts
This optional step takes approximately 1 minute to run and
will take you to a new page.
CO2 as timecorrected
CO2e
-2.67E+04
-2.65E+04
-1.36E+04
-6.18E+03
-1.14E+03
0.00E+00
CH4 as timecorrected
CO2e
N2O as timecorrected
CO2e
SF6 as time- PFC-14 as timecorrected
corrected
CO2e
CO2e
PFC-116 as
PFC-14 as timetimecorrected
corrected
CO2e
CO2e
OPTIONAL Step 3. Draw CRF Charts
This optional step takes approximately 1 minute to run and
will take you to a new page.
PFC-116 as
timecorrected
CO2e
HCFC-22 as
timecorrected
CO2e
HCFC-22 as
timecorrected
CO2e
Total timecorrected
CO2e
Total time-26684.94
corrected
-26536.07
CO
-13615.66
2e
-6179.42
-1140.43
-26684.94
-26536.07
-13615.66
-6179.42
-1140.43
Demonstration of the tool
Part 2: Almond LCA
• UC Davis research team:
Elias Marvinney
Doctoral Student, Horticulture and Agronomy
Alissa Kendall
Dept. of Civil and Environmental Engineering
Sonja Brodt
Agricultural Sustainability Institute
Funded by the Almond Board of California
Scope of our study
Key Inputs and Outputs
CoProducts
Almond Yield
Other Irrigation
Fertilizer
Flows
Nitrogen
Potassium
Boron
Zinc
Micro-sprinkler or Sprinkler
(45% of area)
Drip (25% of area)
Flood (30% of area)
Saplings
Pollination
Unit/ha
0
kg N
kg K2O
gB
kg Z
0
0
0
0
1
Inputs
22
22
448
5.6
m3x103
0
2.8
2
3
Years
4
5
6
7-25
Clearing
45 90 135
45 90 135
448 448 448
5.6 5.6 5.6
179
179
448
5.6
224
224
448
5.6
224
224
448
5.6
-----
5.3
11.2
11.2
11.2
--
m3x103 0
1.7 2.7 5.8 8.3 8.3
8.3
8.3
3
3
m x10
0
3.3 6.4 9.7 13.0 13.0 13.0
13.0
accumulated
#
128Carbon
1.3 is1.3
1.3 1.3 and
1.3 stored
1.3 in 1.3
hives
0 trees
0 (and0 soils)
4.9 over
4.9the4.9
4.9life 4.9
orchard
OutputsAt the end of the orchard life
cycle.
Non-flood irrigated - 70% of
kg
and used
0 cycle,
0 trees
0 are
203removed
407 813
1017 for 2242
total area
kernel
bioenergy production (95%). When
Flood irrigated - 30% of total
kg
the 407
atmospheric
carbon2466
0 combusted
0
0 all203
712 1017
area
kernel
stored in the tree is released.
kg
Weighted average yield
0
0
0 203 407 783 1017
2309
kernel
Shells
kg
0
0
0 448 897 1793 2242
2242
Hulls
kg
0
0
0 897 1793 3587 4483
4483
Woody Biomass (at 32%
kg
0
30 94 147 185 215
239
260
moisture)
-----
8.1
8.3
---
---35073
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
M, E
Petroleum
Exploration
and Extraction
W, P
M, E
Crude oil
transportation
W, P
M, E
Crude oil
refining
W, P
M, E
Delivery of
Diesel Fuel
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 coproducts 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
Coal
Large
Hydro
California
In-State
Generation
(GWh)
Percent of
California
In-State
Generation
Northwest
Imports
(GWh)
Southwest
Imports (GWh)
California
Power Mix
(GWh)
Percent
California
Power Mix
1,580
0.8%
561
20,545
22,685
7.5%
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
Other
14
0.0%
-
-
14
0.0%
0.0%
34,007
17.1%
9,484
3,024
46,515
15.4%
N/A
N/A
29,376
20,124
49,500
16.4%
199,101
100.0%
39,470
63,396
301,966
100.0%
Renewable
s
Unspecified
Sources of
Power
Total
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
Business as Usual
With Co-Product in Market
We give credit
to almonds for
avoiding silage
Alternative: Economic Allocation
Almond Production
System (Orchard +
Hulling and
Shelling)
Per Hectare
Shells
Woody
Biomass
Hulls
Shell
Lifetime Production
22,221
Mass (kg ha-1)
Total Value (2014 $)
166
Proportion of Total
0.06%
Value:
Bedding
Biopower
Dairy Feed
Hulls
6%
Kernels
94%
Raw Brown-skin Almond
Hull
Processing
Biomass
Orchard
Clearing
Biomass
Orchard
Pruning
Biomass
Kernel
76,783
1,289
37,024
19,157
49,183
15,843
2
124
0
269,617
5.54%
0.00%
0.04%
0.00%
94.35%
Results by life cycle stage
GWP100 (kg CO2eq)
Total Energy (MJ/10)
Emission or
Energy Use
1.63
3.50
Co-Product Credits
(displacement)
-1.63
-1.17
Net
-1.81×10-3
2.33
Economic
allocation
1.53
3.30
Scenario Analysis showed large possible
ranges for results – some of these are up
to grower practice, others are not
5.36
5
type is a key
BaU
factor here…a 50
4.30
4
kg CO₂e kg kernel -1
b. 60
Mean
Pump
3
1.57
2
1
0
0.16
-1
BaU
Scenario Results
1.04
0.68
0.64
0.64
0.76
0.37
40
35.12
-2.14
35.12
30
20
Best case –
Gasification and
stable C in biochar
0
23.31
23.31 20.86
16.02
12.05
8.13
-1.86
32.96
23.31
10
-2
-3
Mean
52.67
Scenario Results
MJ kg kernel -1
a. 6
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
Carbon Flows over an Orchard Life
Cycle
Natural
Gas
Crude
oil
Electricity
Atmospheric
CO2
Water
Agrochemicals
Diesel /
Equipment
Almond Orchard Cropping
System
Stored C
Transport
Biomass
for
power
Edible Food Supply
Time
Biogeochemical
Emissions
Combustion
Emissions
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
CRF of CO2 temporarily stored in above-ground
orchard biomass
2E-10
W-yr/m2
0
-2E-10
-4E-10
-6E-10
-8E-10
-1E-09
0
100
200 years 300
400
500
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
amkendall@ucdavis.edu
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.