lca almonds

RESEARCH AND ANALYS I S

Life Cyclebased Assessment of EnergyUse and Greenhouse Gas Emissions inAlmond Production, Part IAnalytical Framework and Baseline Results

Alissa Kendall, Elias Marvinney, Sonja Brodt, and Weiyuan Zhu

Summary

This first article of a two-article series describes a framework and life cyclebased modelfor typical almond orchard production systems for California, where more than 80% ofcommercial almonds on the world market are produced. The comprehensive, multiyear,life cyclebased model includes orchard establishment and removal; field operations andinputs; emissions from orchard soils; and transport and utilization of co-products. Theseprocesses are analyzed to yield a life cycle inventory of energy use, greenhouse gas (GHG)emissions, criteria air pollutants, and direct water use from field to factory gate. Resultsshow that 1 kilogram (kg) of raw almonds and associated co-products of hulls, shells, andwoody biomass require 35 megajoules (MJ) of energy and result in 1.6 kg carbon dioxideequivalent (CO2-eq) of GHG emissions. Nitrogen fertilizer and irrigation water are thedominant causes of both energy use and GHG emissions. Co-product credits play animportant role in estimating the life cycle environmental impacts attributable to almondsalone; using displacement methods results in net energy and emissions of 29 MJ and0.9 kg CO2-eq/kg. The largest sources of credits are from orchard biomass and shellsused in electricity generation, which are modeled as displacing average California electricity.Using economic allocation methods produces significantly different results; 1 kg of almondsis responsible for 33 MJ of energy and 1.5 kg CO2-eq emissions. Uncertainty analysis ofimportant parameters and assumptions, as well as temporary carbon storage in orchardtrees and soils, are explored in the second article of this two-part article series.

Keywords:

agricultureagroecosystemsenergy footprintfood productionlife cycle assessment (LCA)orchards

Supporting information is availableon the JIE Web site

Introduction

California-grown almonds dominate the global market. In20122013, California produced 953,000 tonnes of almonds,constituting 83% of the worlds commercial almond production(OGA 2013) and occupying more than 315,000 hectares (ha)of Californias fertile cropland (USDA 2013). As with manycommercially produced crops, almond production demands

Address correspondence to: Alissa Kendall, Department of Civil and Environmental Engineering, University of CaliforniaDavis, One Shields Avenue, Davis, CA 95618,USA. Email: [email protected]

2015 The Authors. Journal of Industrial Ecology, published by Wiley Periodicals, Inc., on behalf of Yale University This is an open access article under the terms of theCreative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.DOI: 10.1111/jiec.12332 Editor managing review: Miguel Brandao

Volume 00, Number 0

significant quantities of agrochemical inputs and fossil fuels formechanized field operations. In addition, commercial almondproduction in California requires irrigation, which accessesgroundwater resources and surface waters by the CaliforniaAqueduct system, entailing significant energy inputs for on-siteand upstream water pumping.

Whereas almond production in California requires fossilenergy inputs and causes greenhouse gas (GHG) and other

www.wileyonlinelibrary.com/journal/jie Journal of Industrial Ecology 1


emissions, the orchard agroecosystems that yield these almondsaccumulate significant quantities of biomass during the 25-yearorchard life span and generate a large amount of biomassin wood, shells, and hulls annually (Kroodsma and Field2006; Oelbermann et al. 2004). A significant fraction oforchard biomass and almond shells are combusted to produceelectricity at power plants, which are widely distributed inalmond-growing regions of California (Wallace and Leland2007). Other co-products from the system, such as hulls, alsofind economic uses, for example, as livestock feed.

This study characterizes a typical almond orchard pro-duction system in California and uses life cycle assessment(LCA)-based methods to inventory GHG emissions, energyuse, direct water use, and other air pollutants. The researchis divided into two parts reflected in this two-article series.The objectives of the current article are to describe modeldevelopment, calculate baseline results, and guide the selectionof parameters for further analysis conducted in the secondarticle (Marvinney et al. 2015). The part II article builds onthe part I article by conducting sensitivity and scenario analysison model parameters, and by testing the effects of includingtemporary carbon storage in orchard agroecosystems on globalwarming potential (GWP) calculations.

Though LCA and carbon footprinting methods havebeen applied to a wide variety of food production systems,orchards have been examined relatively infrequently. Studieshave focused primarily on apple (Mila` i Canals et al. 2006;Mouron et al. 2006; Page et al. 2011), kiwi (Xiloyannis et al.2011), citrus (Coltro et al. 2009; Mordini et al. 2009), andwalnut production, although primarily in the context of timberproduction (Cambria and Pierangeli 2011). Many of thesestudies examine a single year for a production system and do notconsider the entire orchard life cycle. In a comprehensive re-view of perennial cropping system LCAs, Bessou and colleagues(2013) identified this and a number of additional shortcomingsand opportunities for improvement, including modeling allperennial life cycle stages (including nursery production forsaplings) and changes in yield over the orchard life span, as wellas the need for improved measurement and assessment of fieldemissions. The study described in this article addresses theseidentified shortcomings and considers additional processes notincluded in previous orchard LCAs, such as spatially explicitmodeling of irrigation technologies and water sources.

Methods and Materials

Goal and Scope Definition

The goal of this project is to develop a process-basedlife cycle inventory (LCI) for typical commercial Californiaalmond production, with particular emphasis on estimatingthe GHG emissions and energy consumption associated withalmond production activities, though criteria air pollutants(air pollutants regulated under the U.S. National Ambient AirQuality Standards) and direct water use are tracked as well.Criteria air pollutants are only reported in the Supporting

Information available on the Journals website. GHG emissionsare reported in units of carbon dioxide (CO2)-equivalence(CO2-eq) based on the most recent Intergovernmental Panelon Climate Changes (IPCC) GWPs (Myhre et al. 2013).

The profile of a typical almond crop is based on area-weighted averages for the state. The area-weighted averageincludes yield and water-use estimates by irrigation sys-tem type, as well as spatial determinants of energy use inirrigationnamely, groundwater depth and surface watersource. Operations and inputs that contribute the most tototal emissions and energy (i.e., hotspots) over the almondproduction life cycle are identified to assist growers in targetingthe likely highest emitting or highest energy-using processesfor reduction, as well as to guide the selection of parameters forfurther study in the part II article of the series.

The modeling unit of analysis is 1 ha of almond orchardassessed over a 26-year time period (year zero through 25) forall inputs and outputs; however, the functional unit of analysisis 1 kilogram (kg) of raw brown-skin almond (almond kernel)at the postharvest processing facility gate. Emissions and energyper kg yield are not constant year to year, so averaging overthe orchard life span is required to report the emissions of atypical California almond.

The environmental flows captured in the analysis includerenewable and nonrenewable primary energy, biogenic carbonassimilated during biomass growth and emitted during biomassutilization (which is only used in the part II article of theseries for temporary carbon storage calculations), directwater use, GHG emissions (fossil CO2, methane [CH4],nitrous oxide [N2O], and sulfur hexafluoride), and criteria airpollutants.

System Definition and Boundaries

The Orchard Life Cycle and Orchard OperationsThe following processes are quantified over the productive

life span of an almond orchard in this study (figure 1): nurseryproduction of almond saplings; orchard establishment; fieldoperations; production and transport of chemical and materialinputs to the orchard; pollination services; biogeochemical fieldemissions; and transport and utilization of co-products, namely,biomass removed during pruning and orchard clearing andshells used in electricity generation, and hulls used as dairy feed.

The orchard life cycle produces a total of 181 tonnes ofalmond kernel, along with co-products of nearly 400 tonnesof shells and hulls, and 41 tonnes of woody biomass. Year zeroof the life cycle requires land preparation and orchard establish-ment (planting); years 1 and 2 are dedicated to tree growth andhave no yield and relatively low inputs of water and fertilizer;years 3 to 6 have increasing yields of almonds and prunings,as well as increasing inputs of water and fertilizer; years 7through 25 mark tree maturity when maximum steady-stateyields of almonds and co-products are achieved, and whichrequire maximum inputs of water and agrochemicals. Afterharvest in year 25, the orchard is removed, to be re-establishedthe following year. Orchard removal yields 86% of all the

2 Journal of Industrial Ecology


Biomass Co-product Fate & Utilization Model

Orchard Establishment Orchard Production & Harvest

Orchard Removal

Nursery Model

Biomass Power Plants

Solid Fuel

Gasif-ication

BiocharModel

In-Field Mulch

In-field Burning

Air Pollution

Model

Agro-chemical

Inputs

Transport Modeling

Farm Equipment Modeling

California Aqueduct

Model

Irrigation systems

Groundwater Pumping

Hulling and Shelling

In-shell A

lmonds

Orchard

Biom

ass

Hulls, Shells & Hash

AlmondKernel

Field N2O Models

Legend

(Sub)Processes

(Co-)Product Flows

Co-Products for Livestock

Operation

Orchard

Biom

ass

In-Field

Figure 1 Model framework.

woody biomass generated by the orchard. Figure 1 illustratesthe almond life cycle and the processes modeled.

Table 1 describes, in detail, the key inputs and outputsfrom the orchard over the 26-year life span. Annual yield isa critical parameter given that orchard production processesand consequent environmental flows are divided by yield whencalculating the life cycle impacts of a mass of almonds. Thoughyield varies within and across orchards, the two primaryinfluences on yield are the age of the orchard and the irrigationsystem type. There are two primary categories of irrigation thatinfluence yield: nonflood system types, which include micro-sprinkler (45% of almond orchards), drip (25% of almondorchards), and sprinkler (18% of almond orchards); and floodsystems (12%of almondorchards). Each irrigation system type ismodeled separately, but the composite (area-weighted average)value is used to represent typical California almond production.

Different irrigation system types use different materials,water pressures, and quantities of water (different on a perha basis and per mass of almond basis) and require differentmaintenance and replacement rates. These are all included inthe analysis. Section S.3.3 in the supporting information onthe Web provides additional details on the irrigation systemassumption and data that underlie irrigation system modeling.

Further assumptions for the orchard system include:

One percent of the trees die and are replaced each year.Replanting and biomass removal are accounted for ona yearly basis until year 20, after which no replantingoccurs.

The modeled orchard is established on land previouslyoccupied by almond orchard and will be replaced with

almond orchard at the end of its productive life span,leading to no net change in soil carbon levels at end oflife (EOL). Although Kroodsma and Field (2006) deter-mined that a net CO2 sequestration occurs in orchardsoils when farmland is converted from annual produc-tion systems, the net sequestration in orchard floor soilis assumed negligible, based on the assumption that theprevious system was also almond orchard and the factthat orchard soils are severely disturbed during clearing,releasing CO2, and eliminating sequestration at the endof the orchard life span (Six et al. 2004). However, thesecond article in this series considers temporary carbonstorage in standing biomass, as well as estimates of carbonaccumulated in soils during the life span, to determinethe potential contribution of temporary carbon storage inGWP characterizations.

Each irrigation system is modeled separately to accountfor differences in yield, water use (including pumpingrequirements), and differences in direct and indirect N2Oemissions from the field using IPCC Tier 2 methods.

Agricultural equipment lasts a relatively long time andmay have multiple uses, and many key operations areconducted by contractors who use equipment year roundonmany orchards and farms. For these reasons, equipmentproduction is unlikely to have a major impact on theresults of this analysis and is excluded, consistent withthe treatment of long-term capital investments in otherLCA studies (BSI 2011).

Kendall et al., Life Cycle Energy and GHG Emissions for Almonds, Par t I 3


Table 1 Key inputs and outputs from 1 ha of almond orchard

YearFlows Unit 0 1 2 3 4 5 6 7 to 25 Clearing

Inputs*

Fertilizer Nitrogen kg N ha1 0 22 45 90 135 179 224 224 Potassium kg K2O ha1 0 22 45 90 135 179 224 224 Boron g B ha1 0 448 448 448 448 448 448 448 Zinc kg Z ha1 0 5.6 5.6 5.6 5.6 5.6 5.6 5.6

Irrigation Micro-sprinkler orsprinkler

m3 ha1 0 2,794 5,334 8,128 8,280 11,176 11,176 11,176

Drip m3 ha1 0 1,676 2,743 5,791 8,280 8,280 8,280 8,280 Flood m3 ha1 0 3,302 6,350 9,652 12,954 12,954 12,954 12,954

Other Saplings # ha1 128 1.3 1.3 1.3 1.3 1.3 1.3 1.3 Pollination hives ha1 0 0 0 4.9 4.9 4.9 4.9 4.9

OutputsAlmond yield Nonflood irrigated kg kernel ha1 0 0 0 203 407 813 1,017 2,242

Flood irrigated kg kernel ha1 0 0 0 203 407 712 1,017 2,466 Weighted average yield kg kernel ha1 0 0 0 203 407 783 1,017 2,309

Co-Products Shells kg ha1 0 0 0 448 897 1,793 2,242 2,242 Hulls kg ha1 0 0 0 897 1,793 3,587 4,483 4,483 Woody biomass (at 32%

moisture)kg ha1 0 30 94 147 185 215 239 260 35,073

Sources: Freeman and colleagues (2003a, 2003b); Duncan and colleagues (2006); Connell and colleagues (2006); Freeman and colleagues (2008); Duncanand colleagues (2011a, 2011b); and Connell and colleagues 2012).*Pesticides used are listed in table S3 in the supporting information on the Web.kg = kilograms; N = nitrogen; ha = hectare; K2O = potassium oxide; g =grams; B = boron; Z = zinc; m3 = cubic meters; # = number.

Postharvest Processes: Hulling and Shelling OperationsAfter harvest, in-shell almonds are transported to hulling

and shelling facilities, where hulls and then shells are removed.After this stage, almonds can be processed for retail or storedfor further processing at a later date. Surveys were obtainedfrom five hulling and shelling facilities that, together, processedapproximately 15% of the states almonds in the survey year.These facilities provided information on energy consumptionduring operations, their annual production, and the massand fates of co-products. These data were used to generate aweighted mean value for energy, fuel use, and co-products perkg almond kernel produced.

The weighted average direct energy consumption for hullingand shelling activities per kg of kernel produced is 0.59 mega-joules (MJ) and breaks down by energy carrier as follows:0.55 MJ of electricity; 0.023 MJ of propane; 0.011 MJ of diesel;and 0.0086MJ of gasoline. This is total facility energy, meaningthat energy has not yet been allocated among almond kernel andother co-products. Table 2 shows the four possible fates of thesesix co-products, which include handlers, feed, livestock bed-ding, and energy uses. Handlers transport almonds for furtherprocessing, further packaging for retail, or directly to wholesaleor retail locations. Feed uses for hulls and hash are assumed to befor dairy cattle, as is livestock bedding use for shells. Energy usesare for combustion in biomass power plants to generate electric-ity. One hundred percent of each co-product is assumed to bedirected to its indicated fate (though losses could occur during

transport, handling, and processing), except for shells, whichare split evenly among energy and bedding. Note that some al-monds (2.5% of the processed mass) are hulled but not shelled;these will be transported from the facility as in-shell almonds.

Co-product Treatment

Co-products are generated from the orchard stage andfrom the hulling and shelling stage of production. For theorchard stage, the primary co-products are in-shell almondsand orchard biomass exported from the site for electricityproduction. Co-products generated at hulling and shellingfacilities include (1) raw brown-skin almonds, (2) in-shellalmonds, (3) hulls, (4) shells, (5) hash (a mix of hulling andshelling fines that might include all parts), and (6) woodybiomass (sticks and twigs that are unintentionally harvestedwith the almonds). The quantity of co-products from hullingand shelling and their uses are reported in table 2.

The International Organization for Standardization (ISO)14040 LCA standards favor avoiding allocation calculationsby either subdivision of the system into separately analyzedprocesses, or expanding the system boundaries to include allprocesses associated with co-products, and also recommendsthat multiple methods be tested when allocation cannot beavoided (ISO 2006). Subdivision may not be possible whereprocesses cannot be disaggregated, as in the case of orchardproduction systems. Thus, the baseline approach used in this



Table 2 Annual co-product mass and fate based on a weighted average for five surveyed shelling and hulling operations

Co-products Fate Mass (kg) % total output by mass*

Brown-skin almonds Handler 24,330,652 31.6In-shell almonds Handler 1,902,324 2.5Hulls Dairy feed 37,984,437 49.3Hash Dairy feed 385,006 0.5Shell Energy (50%) and livestock bedding (50%) 10,992,532 14.3Woody biomass Bioenergy 637,894 0.8

*May not sum to 100% owing to rounding.kg = kilograms.

analysis is displacement (i.e., system expansion), but economicallocation is also tested to illustrate the effect of co-producttreatment on analysis outcomes.

System ExpansionWhen system expansion is used to develop co-product

displacement credits, co-products used in electricity generation(woody biomass and shells) are assumed to displace theaverage electricity fuel mix for the state. This approach waschosen based on Marland and Schlamadinger (1995). Notall almond orchard biomass is destined for electric powergeneration, however. Alternative uses include use on-farm asmulch and groundcover, which receive no co-product creditor carbon sequestration in this analysis under the assumptionthat biogenic CO2 stored in mulched biomass is releasedover relatively short time scales to the atmosphere duringdecomposition. Displacement calculations for hulls and hashassume that these products displace silage corn in cattle diets.

Biomass is generated during orchard pruning and duringorchard removal at EOL. Values from Wallace and Leland(2007) were used to estimate the average mass of pruningsremoved. Based on personal communication and publishedliterature, we assume that 50% of these prunings are burnedin-field and 50% are used as mulch (Wallace and Leland 2007).When prunings are burned, CH4, N2O emissions, and criteriaair pollutants are generated and tracked in the modeling,whereas biogenic CO2 released during burning is not.

No existing data were found on the quantity and fate ofbiomass generated during orchard removal. Thus, primary datawere collected from a sample of orchard-clearing operationsrepresenting 62 different locations, and a total of more than800 ha within the San Joaquin Valley. These data were usedto estimate the average biomass removed per ha at the endof an orchards 25-year productive life. Surveyed operatorsreported that approximately 95% of cleared biomass is used forelectricity generation, with the remainder used as mulch andground cover. Table 1 shows the annual quantity of biomassremoved from a typical orchard over its life span.

The energy content of wood was obtained fromWallace andLeland (2007), and a reasonably low estimate for power plantconversion efficiency of 0.25 was used to determine electricitygeneration offsets to avoid potentially overestimating credits(Bain 1993). The equivalent emissions from the average

California grid electricity generation mix were considered tobe displaced by the electricity produced from orchard biomass.Each kg of green (wet) biomass generates approximately2.57 MJ of electricity after being dried in-field and at thepower plant. When hulls and hash are fed to cattle, they areassumed to displace silage on a one-to-one mass basis. DetailedLCI information is available in table S3 in the supportinginformation on the Web.

Economic AllocationEconomic allocation is tested as an alternative to system

expansion. Economic allocation was favored over othervalue-based allocation methods because allocation based onmass or energy content would attribute a very large portion ofenvironmental flows to almond co-products, rather than thealmond kernel. For example, a mass-based allocation wouldlead to partitioning that assigns less than one quarter of theenvironmental flows to almonds. This allocation would notreflect the primary economic driver of almond orchard systems,which is the production of almonds for human consumption.

Economic allocation data were drawn from a variety ofsources for wholesale price information for the co-productsgenerated: almonds; hulls for dairy feed; electric power; andshells used as livestock bedding. The methods and data used forthese calculations are described in section S5 in the supportinginformation on the Web.

Data Sources

University of CaliforniaDavis (UCD) cost and returnstudies were used as the basis for the orchard LCA model. Costand return studies document annual crop production costs forvarious California crops, including almonds, by inventoryingtypical inputs and cultural practices on a regional basis up tothe farm gate (Freeman et al. 2003a, 2003b; Duncan et al. 2006;Connell et al. 2006; Freeman et al. 2008; Duncan et al. 2011a,2011b; Connell et al. 2012). The studies are developed based ondata collected from growers, orchard managers, and UCD co-operative extension farm advisors through surveys, interviews,and focus groups. They provide a picture of the typical nutrient,pesticide, fuel, and water use, equipment use patterns (includ-ing equipment type and hours of operation), and annual yieldsfor an orchard system under a particular irrigation system type



in a particular growing region (Sacramento Valley, San JoaquinValley North, and San Joaquin Valley South). In this LCA, themost conservative available regional data from the studies areused. In this context, conservative refers to the highest typicalinput values, to reduce the risk of underestimating inputs.

Primary data, secondary data, and emissions models arecoupled with the cost and return studies to develop the LCImodel. In addition, because the cost and return studies do notinclude postharvest processing, primary data are used to modelthese processes.

Primary Data Collection for Orchard and PostharvestProcessesOne shortcoming of using the cost and return studies to in-

ventory inputs and operations is that custom operations, thoseoperations conducted by contractors rather than the orchardowners and managers, are tracked only as a cost, omitting infor-mation such as the hours of equipment operation and chemicalor fuel inputs associated with these operations. To fill theseand other data gaps in the model, additional data were ob-tained through surveys of businesses and individuals involvedin almond production. Surveys were administered to nurseryoperators, almond growers and their orchard managers, customharvest operators, and orchard-clearing operators. These sur-veys were conducted by both online survey and in-person inter-views. In-person interviews were conducted to collect data forspecific aspects of an operation, particularly equipment use andtime needed for various tasks. No survey data for individual re-spondents are reported in this article, to protect the anonymityof cooperating individuals and businesses, but, wherever possi-ble, aggregated or composite results from surveys are provided.

Data for hulling and shelling were collected throughsurveys and interviews of facility operators, as described in thePostharvest Processes: Hulling and Shelling Operations section. Aswith other survey and interview data collected in this research,data are published as a composite (weighted average) of surveyresults to ensure the anonymity of participating businesses.

Orchards are irrigated either using groundwater or throughthe extensive network of aqueducts in the state. Irrigationtype (flood, micro-sprinkler, sprinkler, or drip) and the regionof irrigation are critical factors in determining inputs (bothwater quantity and the energy use for water delivery andapplication) and yield. Regional distribution information onirrigation methods and the proportion of groundwater versussurface water used by growers was obtained from survey datacommissioned by the Almond Board of California to develop asustainability program for the states almond growers (AlmondBoard of California 2012).

Where groundwater is used, direct pumping energy isaccounted for in on-farm electricity and diesel use basedon groundwater depth; however, water delivered from theCalifornia aqueduct system required the development of a newLCI. The LCI was developed using geographical informationsystems (GIS) modeling and aqueduct water pumping energyrequirements (Burt et al. 2003; Klein and Krebs 2005). Onaverage, the energy and CO2-eq emissions for pumping 1 cubic

meter (m3) of water to California almond orchards are 0.59 MJand 94.7 grams (g) CO2-eq, respectively.

A few entirely original LCIs had to be created for thismodel, because no previous LCIs or studies were identified.The original LCIs created as part of this research include:nursery production of orchard saplings; orchard pollination bycommercial beekeepers; irrigation water from the Californiaaqueduct system; and LCIs for a number of custom operations,most important, orchard removal.

An LCI model for nursery production of almond saplingswas developed with the cooperation of one major supplierin the state of California. This LCI is described in detail insection S.3.1 in the supporting information on the Web. TheLCI for nursery production shows that each almond saplingis responsible for 2.53 kg CO2-eq emissions and 18.1 MJ ofenergy use. Nursery tree production systems generate multipleproducts. Economic allocation methods were used to allocateamong co-products. Nurseries produce a variety of orchardtree saplings, and thus the LCI was allocated to almondsaplings based on the percentage of total gross nursery incomefrom almond sapling sales. Previous LCA studies of nurseriesindicate that the price of trees tend to reflect time spent ingreenhouses and the quantity of agrochemical inputs used inproduction (Kendall and McPherson 2012).

Almond production in California relies on paid pollinationservices provided by commercial beekeepers. Pollinationservices and honey are the only major co-products fromcommercial beekeeping operations. A previous study examinedlife cycle air emissions for several commercial beekeepingoperations in the continental United States to model U.S.honey production (Kendall et al. 2012). This honey LCA wasused to develop a pollination service LCI based on economicallocation between the two products. Inputs and emissionswere attributed to pollination services on a per hive basis,and 4.9 hives are typically required per ha of almond orchardin each productive year. The inventory on a per ha basis isprovided in table S5 in the supporting information on theWeb. Section S.3.2 in the supporting information on the Webdiscusses the development of this inventory in greater detail.

LCIs for custom operations, such as orchard removal, weredeveloped by linking data on equipment use rates provided byoperators to the OFFROAD emissions model for calculatingemissions and fuel use, and fuel production was characterizedusing a diesel production LCI, as documented in table S3 inthe supporting information on the Web.

Transportation Modeling for Inputs and Outputsfrom the OrchardA number of transportation stages are modeled in the

almond life cycle. In the orchard stage of production (field tofarm gate), transport modeling includes delivery of inputs tothe orchard, namely, agrochemicals. In some cases, such as fornitrogen fertilizer, multiple stages of transport were modeled,including the transport of precursor chemicals, followed bytransport of the final compounds to local warehouses, and then



final delivery to orchards. Transport distances were obtainedthrough personal communications with chemical manufactur-ing company representatives, material safety data sheets, and agray literature search to determine where active ingredients andfinal formulations are manufactured. Shipping route distanceswere calculated using previously published data (Kaluza et al.2010). Section S1 and table S1 in the supporting informationon the Web provide additional detail on transportationmodeling.

Accounting for transportation distances for woody biomassfrom orchards is important for understanding the energy useand emissions of utilizing co-products. Emissions from biomasstransport from orchard to power plant were calculated basedon location data for biomass-fed power plants obtained fromthe California Biomass Collaborative (2014). Plant locationdata were overlaid on a map of almond production (USDA2013) and modeled as described above for material transport.Almond production areas within a given radius of each powerplant were identified, and the results were used to determinethe average distance between an acre of almond orchard andthe nearest biomass-fed power plant. The weighted-averageone-way distance was calculated at 33.6 kilometers (km).Biomass is assumed to be transported in trucks with 22.7 tonnes(25 short tons) of capacity.

Transportation modeling was also required for outputs fromthe orchard. Harvested almonds were transported an averageone-way distance of 26.7 km in trucks with 22.7 tonnes (25short tons) of capacity.

Secondary Data for Background ProcessesLCI data quantify energy and material inputs as well as

emissions for a variety of background processes, includingdiesel and gasoline production, agricultural chemicals, plastics,and other agricultural inputs, such as manure. U.S. data wereused where available and supplemented with European datasets where necessary, most notably for pesticide production.The use of European data sets is unlikely to distort results fromthis study, given that pesticides proved to be small contributorsto the impact categories included in this assessment.

Most LCI data come from published academic literature,the ecoinvent Database (last updated in 2011), the GaBiProfessional database (last updated in 2009, 2011, and 2012),and the U.S. LCI database (last updated in 2011) accessedthrough the GaBi 4 and GaBi 6 software (ecoinvent Center2008; PE International 2009, 2012). Table S3 in the supportinginformation on the Web provides a list of all the LCI data setsused in the almond LCA model.

Emission Models for Nitrous Oxide Field Emissionsand Fuel Combustion EmissionsThe IPCC Tier 2 methodology is used to quantify the N2O

emissions from almond orchards, which requires the use ofspecific regional environmental and management data (DeKlein et al. 2006). In California almond orchards, the processesof nitrification and denitrification that produce N2O arelargely driven by nitrogen (N) availability, as determined by

fertilization practices, and soil moisture content, as determinedby irrigation practices (Smart et al. 2011).

The IPCC methods divide N2O emission from managedsoils into two parts: direct and indirect emissions. Both sourcesof N2O are included in the modeling. A detailed descriptionof these pathways and the underlying data used to calculateemissions factors are included in section S2 in the supportinginformation on the Web. Table 3 shows the Tier 2 emissionfactors developed for this study. Because many life cycle studiesrely on IPCC Tier 1 methods, and because N2O emissionssampling has high uncertainty, a comparison of Tier 1 and 2approaches is provided in the part II article of this series.

Fuel combustion emissions for orchard equipment andtrucks were modeled using the OFFROAD software developedby the California Air Resources Board (CARB) (2007). Thissoftware models fleet emissions by geographical region and byequipment age and type within the state of California. CO2,carbon monoxide, CH4, sulfur dioxide, N2O, nitrogen oxides(NOX), nonmethane volatile organic carbons, and particulatematter less than 10 microns emissions were predicted based onhours of use for the mobile equipment used in orchards.

Results and Discussion

Results without Co-Product Allocation

Results show that 35.0 MJ of energy is consumed and1.63 kg CO2-eq emissions (based on global warming potentialfor time horizon of 100 years [GWP100]) are released per kgof brown-skin almond at the hulling and shelling facility gate(with no co-product allocation). Nutrient management alonecontributes 26% of energy consumption and 51% of GWP100,making it the largest contributor to GWP100. Irrigation is thelargest consumer of energy, responsible for 29% of total energyconsumption, and the second-highest source of GWP100 at 24%of CO2-eq emissions. Table S9 in the supporting informationon the Web reports detailed results for air emissions, energyuse, GWP100, and global warming potential for time horizon of20 years (GWP20) for each process.

Results with Co-Product Allocation

The calculated credit for co-products used for electric-ity generation and in feed rations is 6.08 MJ kg1 and0.71 kg CO2-eq kg1 almond kernel at the hulling and shellingfacility gate. This results in net energy use of 28.9 MJ kg1 andnet GWP100 emissions of 0.92 kg CO2-eq kg1 almond kernelat the facility gate, as illustrated in figure 2. Detailed results(including criteria air pollutants and GWP20) are shown intable S10 in the supporting information on the Web.

The results using economic allocation show a significantlydifferent outcome, with almond kernel responsible for 94% ofenvironmental flows, hulls just over 5%, and orchard biomassand shells used as energy resources for power generation ap-proximately 1%. Based on economic allocation, 1 kg of almondkernel is responsible for approximately 1.54 kg CO2-eq and



Table 3 Estimation of N2O emission factors (EFs) of flood, micro-sprinkler and sprinkler, and drip-irrigated almond orchards in California

EF of direct N2O EF of indirect N2O EF of indirect N2OIrrigation emission (g N2O-N through NH3 (g N2O- through NOx (g N2O-system type g1 N applied) N g1 N applied) N g1 N applied)

Flood 3.48 103 6.6 104 1.16 103Micro-sprinkler and Sprinkler 3.30 103 4.3 104 1.10 103Drip 3.12 103 4.7 104 1.04 103

Note: N2O = nitrous oxide; g = grams; N = nitrogen; NOx = nitrogen oxides.

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

GWP (kg CO Total Energy(MJ/10)

Other Operations

Hulling & Shelling

Harvest

Irrigation

Biomass Management

Nutrient Management

Pest Management

Co-Product Credit

Net Results from Displacement

Economic Allocation Results-eq)

Figure 2 GWP100 and total energy results by life cycle stage for 1 kg of almonds and final results using displacement and economicallocation methods (assuming mean annual yield of 1.892 kg ha1). The y-axis values for the total energy bar represent the actual values inMJ divided by 10; so, the total energy for 1 kg of almonds is 35 MJ and the net results after the co-product credit are 29 MJ. GWP100 =global warming potential for time horizon of 100 years; kg = kilograms; ha = hectare; MJ = megajoules.

33 MJ. Complete results for economic allocation are providedin table S13 in the supporting information on the Web.

Discussion

There are a few notable outcomes from this study. The firstis the importance of irrigation energy use and its contributionto GHG emissions and total energy consumption, and thesecond is the influence of co-product treatment on the burdensattributable to almonds. As for the importance of irrigation,the United States spans many agroecological regions, whichinclude large areas that depend only on rain-fed agriculture,others that depend on rain and irrigation waters (both surfaceand ground, but largely local water resources), and thenCalifornia, which depends on a unique, extensive, energy-intensive system to store and deliver water from water-richregions to arid regions. Dependency on this system meansthat some agricultural regions in California depend onextremely energy-intense water resources for irrigation.Thus, assessments of agricultural production systems requiregeographically explicit modeling to properly estimate en-ergy and emissions associated with production. The issueof water consumption, and its impact on energy use and

GHG emissions in water-scarce regions, such as Califor-nias southern San Joaquin Valley, is a topic of futureresearch.

Co-product treatment methods have a strong effect onthe outcomes of this analysis, in particular, for co-productsused in power generation. Though, in economic terms, powergeneration is a very low-value use of co-products, when dis-placement calculations are used that assume biopower displacesthe average electricity fuel mix in California, large energy,emission, and GHG credits are generated. This can be viewedas a methodological source of large variability, but might alsobe viewed as a philosophical issue. Displacement calculationsimplicitly assume that, in the absence of electricity generatedfrom almond co-products, the average fuel mix currently usedwould replace it. This may be a reasonable assumption in theshort term, but, actually, as Renewable Portfolio Standards forelectricity become more stringent (CPUC 2013), it might bemore appropriate to assume that other renewable power sourcesare displaced. Such an assumption would significantly changedisplacement calculations and lower the credits attributable toco-products used in power generation.

In addition, the potentially higher economic value forrenewable fuels used in California electricity are not reflected



Figure 3 GWP100 comparison of in-hull almond kernel to the edible fraction of other unprocessed food products.(Note: Co-products are not accounted for in the reported values, and results are drawn from multiple sources, which may use differentmethods and system boundaries.) GWP100 = global warming potential for time horizon of 100 years.

in the calculation because each negotiated rate for a powerproduction facility is confidential (see section S5 in thesupporting information on the Web for additional discussionof economic allocation calculations and data sources). Instead,average wholesale electricity prices are used to estimate thevalue of biomass used in power generation. The potentiallyhigher wholesale electricity price for bio-based power inCalifornia could increase the economic value of biomass usedfor electricity generation.

Figure 3 compares the GWP100 of unprocessed almonds toother unprocessed foods on the basis of mass and caloric con-tent. Because these are unprocessed food products, co-productsthat are generated during processing are not accounted for. Thecaloric content of these products, including almonds, is adjustedto account for the inedible portion of the product. The inedibleportions include materials removed postharvest, such as hullsand shells in almonds or bone, gristle, and offal inmeat products(CCE 2012; Faria et al. 2010; Akhan et al. 2010). The caloricvalues of the edible portion of unprocessed products are assignedall of the environmental impacts measured at the farm gate.

This comparison is imperfect not only because co-productsare not accounted for, but also because mass and caloriccontent do not represent the complete role or value of aparticular food within the human diet. Further, the GWP ofthe other foods shown in figure 2 were calculated in differentLCA studies (using different system boundaries, assumptions,and methods), leading to some uncertainty in the comparison.Nevertheless, a comparison on caloric and mass bases providecontext for the almond LCA results. On a caloric basis, almondperforms better than the animal products included in figure 2and has similar CO2-eq emissions to the field crops included inthe comparison (Nielsen et al. 2003). The only other orchardcrop in figure 3, Spanish and Italian oranges (Mordini et al.2009), show a smaller carbon footprint than almond on a perkg basis, but not on a kilocalorie (kcal) basis. The per kcal basisaccounts for differences in water content and energy density

between oranges and almonds and illustrates one reason whya mass-based comparison can be misleading.

Conclusion

This article examined typical almond production in Cal-ifornia using weighted-average data and consensus values foralmond production inputs. As with all agricultural products,almonds are subject to the inherent variability of region andclimate, which affects yields, biogeochemical emissions fromorchard soils, and cultural practices of growers. This analysisalso shows the critical importance of understanding the fateof co-products from orchard production, their utilization forenergy production, and the use of displacement calculationsfor allocation. The second article in this series explores thesekey questions of variability, uncertainty, and scenarios thatrepresent the heterogeneity of existing practices and exploresthe potential for changes over time that may significantly affectthe environmental performance of almonds, such as changesto energy recovery technologies and irrigation technology.

Acknowledgments

This research was supported by a grant from the AlmondBoard of California (Project No.: 10-AIR8-Kendall), entitledGreenhouse Gas and Energy Footprint of California AlmondProduction, Principle Investigator Dr. Alissa Kendall. Thisresearch was also supported, in part, by the Specialty CropBlock Grant Program at the U.S. Department of Agriculture(USDA) through Grant 14-SCBGP-CA-0006, PrincipleInvestigator Dr. Sonja Brodt. Its contents are solely theresponsibility of the authors and do not necessarily representthe official views of the USDA.

The authors thank all of the growers, nursery owners, or-chard management companies, and colleagues who generouslygave their time and provided data and assistance to this project,



and particularly to Dr. Johan Six and Dr. David Smart, andtheir respective research teams, for assistance in provision ofdata and guidance on field N2O emissions.

References

Akhan, S., I. Okumus, N. Kocak, and F. D. Sonay. 2010. Growth,slaughter, yield and proximate composition of rainbow trout (On-corhynchus mykiss) raised under commercial farming condition inBlack Sea. Journal of the Faculty of Veterinary Medicine, Universityof Kafkas 16(Suppl B): S291S296.

Almond Board of California. 2012. Irrigation management. In Almondsustainability modules, edited by D. Sonke et al. Modesto, CA,USA: Almond Board of California.

Bain, R. L. 1993. Electricity from biomass in the United States: Statusand future direction. Bioresource Technology 46(12): 8693.

Bessou, C., C. Basset-Mens, T. Tran, and A. Benoist. 2013. LCAapplied to perennial cropping systems: A review focused on thefarm stage.The International Journal of Life Cycle Assessment 18(2):340361.

BSI (British Standards Institution). 2011. PAS 2050: 2011 specificationfor the assessment of the life cycle greenhouse gas emissions of goodsand services. London: BSI.

Burt, C., D. Howes, and G. Wilson. 2003. California agricultural wa-ter electrical energy requirements. Sacramento, CA, USA: Cali-fornia Energy Commission. www.itrc.org/reports/energyreq.htm.Accessed 6 June 2011.

CARB (California Air Resources Board). 2007. OFFROAD2007.Sacramento, CA, USA: Mobile Source Emissions InventoryProgram.

California Biomass Collaborative. 2014. California biomass powerplantsWoody biomass utilization: California biomass powermap. Davis, CA, USA: University of California CooperativeExtension.

Cambria, D. and D. Pierangeli. 2011. A life cycle assessment casestudy for walnut tree (Juglans regia L.) seedlings production.The International Journal of Life Cycle Assessment 16(9): 859868.

CCE (Cornell Cooperative Extension). 2012. Yields and dressing per-centages. Cornell, NY , USA: Cornell Small Farms Program,Cornell University. smallfarms.cornell.edu/2012/07/10/yields-and-dressing-percentages/. Accessed 19 June 2014.

Coltro, L., A. L. Mourad, R. M. Kletecke, T. A. Mendonca, and S.P. M. Germer. 2009. Assessing the environmental profile of or-ange production in Brazil. The International Journal of Life CycleAssessment 14(7): 656664.

Connell, J. H., J. P. Edstrom, W. H. Krueger, R. P. Buchner, K.M. Klonsky, and R. L. DeMoura. 2006. Sample costs to estab-lish an orchard and produce almonds: Sacramento Valley low-volumesprinkler. Davis, CA, USA: University of California CooperativeExtension.

Connell, J. H., W. H. Krueger, R. P. Buchner, C. J. Debuse, K. M.Klonsky, and R. L. De Moura. 2012. Sample costs to establishan almond orchard and produce almonds: San Joaquin Valley Northsprinkler irrigation. Davis, CA, USA: University of California Co-operative Extension.

CPUC (California Public Utilities Commission). 2013. RPS pro-gram overview. San Francisco, CA, USA: CPUC. www.cpuc.ca.gov/PUC/energy/Renewables/overview.htm. Accessed 1 Jan-uary 2015.

De Klein, C., R. S. Novoa, S. Ogle, K. A. Smith, P. Rochette, andT. C. Wirth. 2006. N2O emissions from managed soils, and CO2emissions from lime and urea application. In IPCC Guidelinesfor National Greenhouse Gas Inventories, edited by S. Egglestonet al. Vol. 4, Agriculture, forestry and other land use. Geneva,Switzerland: Intergovernmental Panel on Climate Change.

Duncan, R. A., P. S. Verdegaal, B. A. Holtz, D. A. Doll, K. A.Klonsky, and R. L. De Moura. 2011a. Sample costs to establishan orchard and produce almonds: San Joaquin Valley North microsprinkler irrigation. Davis, CA, USA: University of California Co-operative Extension.

Duncan, R. A., P. S. Verdegaal, B. A. Holtz, D. A. Doll, K. M. Klonsky,and R. L. De Moura. 2011b. Sample costs to establish an orchard andproduce almonds: San Joaquin Valley North flood irrigation. Davis,CA, USA: University of California Cooperative Extension.

Duncan, R. A., P. S. Verdegaal, B. A. Holtz, K. A. Klonsky, and R. L.De Moura. 2006. Sample costs to establish an orchard and producealmonds: San Joaquin ValleyNorth flood irrigation. Davis, CA,USA:University of California Cooperative Extension.

ecoinvent Center. 2008.Ecoinvent data v2.0.D u bendorf , Switzerland:Swiss Center for Life Cycle Assessment.

Faria, P., M. Bressan, X. de Souza, L. Rossato, L. Botega, and L. daGama. 2010. Carcass and parts yield of broilers reared under asemi-extensive system. Brazilian Journal of Poultry Science 12(3):153159.

Freeman, M. A., K. A. Klonsky, and R. L. De Moura. 2003a. Sam-ple costs to establish an almond orchard and produce almonds: SanJoaquin Valley South flood irrigation. Davis, CA, USA: Universityof California Cooperative Extension.

Freeman, M. W., M. A. Viveros, K. M. Klonsky, and R. L. De Moura.2003b. Sample costs to establish an almond orchard and produce al-monds: San Joaquin Valley South micro-sprinkler irrigation. Davis,CA, USA: University of California Cooperative Extension.

Freeman, M. W., M. A. Viveros, K. M. Klonsky, and R. L. De Moura.2008. Sample costs to establish an almond orchard and produce al-monds: San Joaquin Valley South micro-sprinkler irrigation. Davis,CA, USA: University of California Cooperative Extension.

ISO (International Organization for Standardization). 2006. ISO14040: Environmental managementLife cycle assessmentPrinciples and framework. ISO/TC 207/SC 5. Geneva , Switzer-land: International Organization for Standardization.

Kaluza, P., A. Kolzsch, M. T. Gastner, and B. Blasius. 2010. The com-plex network of global cargo ship movements. Journal of the RoyalSociety, Interface 7(48): 10931103.

Kendall, A. and E. G. McPherson. 2012. A life cycle greenhouse gasinventory of a tree production system. The International Journal ofLife Cycle Assessment 17(14): 444452.

Kendall, A., J. Yuan, and S. B. Brodt. 2012. Carbon footprint and airemissions inventories for US honey production: case studies. TheInternational Journal of Life Cycle Assessment 18(2): 392400.

Klein, G. and M. Krebs. 2005. Californias water-energy relationship.CEC-700-2005-011-SF. Sacramento, CA, USA: California En-ergy Commission.

Kroodsma, D. A. and C. B. Field. 2006. Carbon sequestration inCalifornia agriculture, 19802000. Ecological Applications 16(5):19751985.

Marland, G. and B. Schlamadinger. 1995. Biomass fuels and forest-management strategies: How do we calculate the greenhouse gasemissions benefits? Energy 20(11): 11311140.

Marvinney, E., A. Kendall, and S. Brodt. 2015. Life cycle-based as-sessment of energy use and greenhouse gas emissions in almond



production, part II: Uncertainty analysis through sensitivityanalysis and scenario testing. Journal of Industrial Ecology DOI:10.1111/jiec.12333.

Mila` i Canals, L., G. M. Burnip, and S. J. Cowell. 2006. Evaluationof the environmental impacts of apple production using life cy-cle assessment (LCA): Case study in New Zealand. Agriculture,Ecosystems & Environment 114(24): 226238.

Mordini, M., T. Nemecek, and G. Gaillard. 2009. Carbon & waterfootprint of oranges and strawberries: A literature review. Zurich,Switzerland: Federal Department of Economic Affairs.

Mouron, P., R. W. Scholz, T. Nemecek, and O. Weber. 2006. Lifecycle management on Swiss fruit farms: Relating environmentaland income indicators for apple-growing. Ecological Economics58(3): 561578.

Myhre, G., D. Shindell, F.-M. Breon, W. Collins, J. Fuglestvedt,J. Huang, D. Koch, et al. 2013. Anthropogenic and natural radia-tive forcing. InContribution of working group I to the fifth assessmentreport of the Intergovernmental Panel on Climate Change, edited byT. F. Stocker et al. New York: Cambridge University Press.

Nielsen, P. H., A. Nielsen, B. Weidema, R. Dalgaard, and N. Halberg.2003. LCA food database. Tjele, D enmark: Faculty of AgriculturalSciences Aarhus Universitet. www.lcafood.dk/. Accessed 19 June2014.

Oelbermann, M., R. P. Voroney, and A. M. Gordon. 2004. Carbonsequestration in tropical and temperate agroforestry systems: Areview with examples from Costa Rica and southern Canada.Agriculture, Ecosystems & Environment 104(3): 359377.

OGA (Office of Global Analysis). 2013. Tree nuts: World mar-kets and trade. Washington, DC: United States Department ofAgriculture.

Page, G., T. Kelly, M. Minor, and E. Cameron. 2011. Modeling carbonfootprints of organic orchard production systems to address carbontrading: An approach based on life cycle assessment. HortScience46(2): 324327.

PE International. 2009. GaBi 4: System software and databases forlife cycle engineering. Leinfelden-Echterdingen, Germany: PEInternational.

PE International. 2012. GaBi 6: System software and databases forlife cycle engineering. Leinfelden-Echterdingen, Germany: PEInternational.

Six, J., S. M. Ogle, J. F. Breidt, R. T. Conant, A. R. Mosier,and K. Paustian. 2004. The potential to mitigate global warm-ing with no-tillage management is only realized when prac-tised in the long term. Global Change Biology 10(2): 155160.

Smart, D. R., M. M. Alsina, M. W. Wolff, G. Michael, D. L.Schellenberg, J. P. Edstrom, H. Patrick, and K. M. Scow. 2011.N2O emissions and water management in California perennialcrops. In Understanding greenhouse gas emissions from agriculturalmanagement, edited by L. Guo. Washington, DC: AmericanChemical Society.

USDA (United States Department of Agriculture). 2013. Crop-Scape cropland data layer. Washington, DC: National AgriculturalStatistics Service.

Wallace, H. N. and R. Leland. 2007. Feasibility of a Californiaenergy feedstock supply cooperative. USDA RCGG-2006-CA-02.Davis, CA, USA: Center for Cooperative Development. www.cccd.coop/files/Publications/CA%20Energy%20Feedstock-version6.pdf. Accessed 7 July 2015.

Xiloyannis, C., G. Montanaro, and B. Dichio. 2011. Sustainable or-chard management, fruit quality and carbon footprint. In Proceed-ings VIIth IS on Kiwifruit 913: 269274.

About the Authors

Alissa Kendall is an associate professor in the Departmentof Civil and Environmental Engineering, Elias Marvinney is adoctoral candidate in the Department of Plant Science, SonjaBrodt is the academic coordinator of agriculture, resources, andthe environment at the Agricultural Sustainability Institute,and Weiyuan Zhu is a graduate student in plant sciences, allat University of CaliforniaDavis, Davis, CA, USA.

Supporting Information

Additional Supporting Information may be found in the online version of this article at the publishers web site:

Supporting Information S1: This supporting information includes detailed data on transport distances for orchard inputs,the modeling of N2O emissions, life cycle inventory development, the results for assessed flows, and economic allocationcalculations.


lca almonds

Documents