© 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

ns

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

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.