recent studies have shown that food production 
 and consumption 
 are responsible for 1030% of an individual s total 
 environmental impact .
a considerable amount of the total food intake by 
 mass ( 30% ) is represented by fruits and vegetables , which constitute 
 the largest food group consumed worldwide .
the effects of their production are revealed in different categories 
 of environmental impacts , like climate change , impacts of land and 
 water use , human- and eco - toxicological effects , eutrophication , acidification , 
 soil fertility degradation , and landscape changes .
policy makers and 
 private companies in various countries have recognized the need to 
 quantify these environmental impacts and , on this basis , to identify 
 measures for impact reduction .
for instance , a new law in france and a recommendation of the swiss federal office 
 for the environment encourage the labeling 
 of food products with their carbon / environmental footprints .
private 
 companies , such as tesco and walmart , calculate the carbon footprint 
 of some of their products and communicate these to their customers , while others use such environmental information 
 for internal decision making regarding products and supply chain management .
finally , water footprint studies have gained 
 high interest in the area of food production , revealing 
 the amounts of water consumption and the related impacts .
the international 
 organization for standardization ( iso ) is therefore currently considering 
 a standard on water footprint to allow consistent analysis and reporting 
 for product labeling . despite these initiatives 

for instance , while several life cycle assessment 
 ( lca ) studies on a variety of fruits and vegetables have been published , the comparability of these studies is compromised by differences 
 in system boundaries and background data . in contrast to process - based 
 lca studies ,
input - output lca studies provide data 
 on total food consumption without having cut - offs in the supply chain , 
 leading to a large gap in the overall impacts .
such studies help to 
 identify relevant food groups , but the data are given on an industrial - sector 
 resolution and hence do not allow for identifying improvement potentials 
 within sectors .
moreover , international trade is not well captured 
 due to inconsistencies in the underlying statistical data .
thus , in 
 addition to these studies , detailed , process - based lca data are needed 
 to support decisions regarding adequate sourcing of food products , 
 means of transportation , agricultural management , and , finally , choices 
 between different food commodities . the goals of the present study 
 were ( a ) to elaborate a consistent and up - to - date life cycle inventory 
 ( lci ) of a large range of fruits and vegetables from different origins , 
 ( b ) to show selected life cycle impact assessment ( lcia ) results and 
 derive general decision guidelines for producers , retailers , policy 
 makers and consumers on how to improve the environmental impacts of 
 fruit and vegetable consumption , and ( c ) to illustrate and discuss 
 the implementation of these guidelines for a specific case of purchasing 
 decision and environmental supply chain management of a main swiss 
 retailer .
the functional unit ( fu ) was defined 
 as 1 kg of product at the point of sale .
the lca study includes the 
 following fruits and vegetables : apple , avocado , banana , broccoli , 
 cabbage for conserves , carrots , cauliflower , celery root , citrus fruits , 
 cucumbers , eggplant , fennel , grape , green asparagus , bell pepper , 
 iceberg lettuce , kiwi , lettuce , melon , onion , vine tomatoes , papaya , 
 pear , pineapple , potatoes ( lci adapted from ecoinvent ) , radish , red cabbage , round carrots , spinach , strawberries , 
 tomatoes , white asparagus , white cabbage , and zucchini .
these products 
 cover more than 80% of the fruits and vegetables sold by one of the 
 two major retailers in switzerland in 2007 , for which the study was 
 originally undertaken .
the products were either produced locally or 
 transported to switzerland from 29 different countries .
the lci were 
 compiled by extrapolating from a basic set of data for one product 
 to the same product from other origins by varying parameters , such 
 as transport means and distances , irrigation , heating energy for greenhouse 
 production , and cooling energy for storage . inputs and outputs from 
 packaging and the operation of the store were excluded from the analysis 
 as these were shown to be relatively low compared to the overall impact 
 ( supporting information ( si ) , section 1 ) 
 and equal for all fruits and vegetables .
vegetables , apples , pears 
 and strawberries were modeled using the swiss agricultural standard 
 production scheme called  integrated production  as 
 described elsewhere .
the other fruits 
 were produced according to the so - called  conventional production  . 

tables 
 with agricultural production means for cost calculations were used 
 to set up the inventory of vegetables , apples and pears , whereas for tropical 
 fruit production additional data were obtained from literature and 
 leaflets of agricultural extension services ( si , section 2 ) . good agricultural practice ( gap ) was assumed for all 
 agricultural activities , irrespective of the production site , assuming 
 common global standards throughout the supply chain .
this assumption 
 was in accordance with the commissioner of the study , but may need 
 to be revised in cases in which retailers do not make sure that gap 
 is applied .
next , a short 
 outline of every parameter considered in the lci is given ; detailed 
 information can be found in the si , section 
 2 .
it was assumed that the land occupied 
 is arable and that it had been used for agriculture for a long time . 

land occupation was calculated based on yield and cultivation 
 time per kg of product ( si , section 3 ) .
one of the upstream processes of 
 vegetable growing is the production of seedlings , which are young 
 plants to be bedded out .
we assumed an average size of 20 cm per pot with an estimated weight of 
 20 g. based on the yield and number of seedlings planted per ha , the 
 amount of peat and the transported weight per kg of product from the 
 mining site were calculated .
seedling production in switzerland 
 or further north is generally assumed to take place in heated greenhouses 
 over five weeks . for heating oil consumption ,
the data for eggplants 
 were assumed for all vegetable seedlings because of similar temperature 
 requirements .
the nutrients , extracted by the plants , 
 eroded and leached to water , have to be replaced by soil fertilization . 
 here
we considered effective fertilization with macronutrients using 
 the ecoinvent processes  ammonium nitrate  , 
single 
 superphosphate as p2o5  and  potassium 
 sulphate  ( si , section 5 ) .
individual pesticide production data were 
 not available . in such cases , the generic pesticide process
field emissions of pesticides are often farm - specific and models like 
 in can be used to estimate such emissions accurately .
the ecoinvent data set  fertilizing by broadcaster  
 with middle intensive fuel consumption was used as a proxy for horticultural 
 machinery .
data on the number of machinery operations and the working 
 hours for running the machines were used to quantify the amount of 
 machinery input per kg of crop ( si , section 
 8) .
greenhouse production 
 implies electricity use , for example , for lighting and irrigation pumps . 

the electricity demand was estimated using information from swiss 
 cost calculation sheets assuming a price 
 of 0.15 chf / kwh for industrial companies .
the average european electricity 
 mix ( entso - e , former ucte ) of low voltage was used for all crops except 
 those originating from the americas , to which the u.s .- mix was applied .
to be independent from outdoor temperature , 
 greenhouses are built to provide the appropriate climate .
to show 
 the variability of fuel consumption related to seasonality , a time - dependent 
 heating energy model for greenhouse production was developed and applied . 

this model considers the type of greenhouse ( heat transmission properties ) , 
 the building dimensions , the difference in outside and inside temperature 
 required by the specific crop , solar irradiation and the yield . for 
 details
if the sourcing season was unknown , an annual average 
 amount of heating oil ( fossil fuel ) per 
 crop was used for one growing period .
all productions in switzerland 
 and further north were modeled as heated and nonheated to approximate 
 a winter and a summer production respectively .
irrigation is needed in regions where rainfall 
 is less than the amount of water required to grow a specific crop , 
 where rainfall is seasonally unevenly distributed or if crops are 
 cultivated in greenhouses .
the amount of water irrigated depends on 
 the culture as well as on soil and different climate parameters like 
 temperature , wind and rainfall .
the different amounts of irrigation 
 water for all the crops grown in switzerland are available from elsewhere .
short - term crops ( like lettuce and radish ) and 
 open field crops use 400800 m / ha / growing cycle , 
 long - term greenhouse crops use 30006000 m / ha / growing 
 cycle . the irrigation inventory for imported 
 crops was calculated according to pfister et al . as only the country of origin was known , a production weighted 
 average amount was used , taking into account the geographical distribution 
 of each crop within a country .
domestic production covers 40% and 49% 
 of the fruit and vegetable consumption respectively , whereas the rest is imported .
the most important production 
 sites in a country were identified for each product and the most evident 
 transportation routes and means were chosen according to the scheme 
 in table s4 ( si , section 11 ) .
it was assumed 
 that trucks from industrial countries are euro 4 or 5 standard with 
 cargo weight > 32 t , except for distribution in switzerland , which 
 was modeled with a specific fleet average truck of > 28 t. truck - transportation 
 in emerging economies was simulated with an euro 3 standard for cargo 
 weight > 32 t. by sea route the products are transported by freight 
 ship and in the air by an intercontinental freight aircraft .
the corresponding 
 ecoinvent processes were employed and distances were measured with 
 online tools ( si , section 11 ) .
crops need to be cooled 
 in order to avoid decay before arriving at the point of sale and to 
 elongate the storage life .
transportation was assumed to take place 
 in fully loaded iso - containers with independent cooling aggregates . 
 according to wild
one teu (= twenty - foot equivalent 
 unit ) is the size of a little standardized container with an average 
 load of 10 t. furthermore , the transportation 
 time ( si , section 12 ) was needed to model 
 the consumed cooling energy with the ecoinvent data set  diesel 
 electric generating set  .
several crops ( asparagus , bananas , carrots , 
 celery root , cucumbers , iceberg lettuce , lettuce , radish , spinach , 
 and zucchini ) need to be cleaned after harvesting .
it was assumed 
 that 0.4 l of tap water is used per kg of crop , except for bananas 
 which use 4.4 l per kg .
energy consumption depends on storage 
 time , outside temperature , ideal storage temperature ( crop specific ) 
 ranging from 2 to 13 c and packing density , which is generally assumed to be 300 kg / m .
nitrate and phosphorus - emissions 
 into different compartments were modeled generically , because no site - specific 
 values of the productions sites ( slope , soil , machine type , weather 
 etc . )
is emitted into the air as ammonia ( nh3 ) , 1.7% as nitric 
 oxide ( no ) and the same amount as nitrous oxide ( n2o ) into 
 the air as well , whereas 35% is estimated to be leached as nitrate 
 ( no3 ) into the soil .
constant 
 values of phosphate emission into groundwater ( 0.07 kg phosphate / ha / a ) 
 and of phosphorus emission into surface water ( 0.245 kg phosphorus / ha / a ) 
 were assumed .
assumptions and data about mulch film 
 application and flame treatment are documented in the si , section 6 and 7 .
the elaborated lci data 
 can be coupled with any lcia method . in this paper , we show selected 
 results for the impact categories climate change and water stress .
results 
 in terms of a lcia method using multiple impact categories were calculated 
 with recipe and are shown in the si , section 14 .
human toxicity impacts due to 
 pesticide use , if applied properly , were shown to be relatively small 
 in relation to  other  impacts like gwp and were excluded in this study . in order to efficiently identify 
 improvement potentials , crops were first ranked according to the impact 
 caused by the total sales volume of a crop ( isc , total in 
 eq 1):1where isc , i , j is the specific impact score per kg of 
 crop c from origin i and produced 
 with mode of production / transportation j , and mc , i , j is 
 the respective mass of crop c sold by the retailer .
in addition to the total impact , the sales - amount weighted average 
 impact per kg of product and the variation in specific impact across 
 different origins , production techniques and mode of transportation 
 were also taken into consideration .
priority crops for an in - depth 
 investigation were selected by quantifying the maximal ( not necessarily 
 realistic ) improvement potential per crop according to eq 2:2where ic is the 
 maximal improvement potential for crop c ( in % of 
 total current impact ) , mc  total is the total mass of crop c sold , isc , average is the sales - amount weighted impact score 
 per kg of crop c and isc , min the minimal 
 specific impact for crop c found in the considered origins and mode 
 of production / transportation .
those crops for which the sum of the 
 improvement potentials was larger than one - third of the current co2-footprint were selected for 
 in - depth analysis .
figure 2 shows 
 the co2-footprint of fruit and vegetable sales , calculated 
 according to eq 1 ( figure 2a ) and the specific co2-footprint with its variation ( figure 2b ) .
asparagus , lettuce and cucumbers were 
 selected for in depth investigation , to derive high - leverage recommendations 
 for a reduction in environmental impact .
switching to the respective 
 production alternative with minimal impact for these three crops would 
 achieve a reduction of more than one - third of the current overall 
 co2-footprint caused by the sale of all crops considered 
 ( table 1 ) .
other crops like bananas , pears , 
 apples , citrus fruits , and potatoes 
 also cause a relatively large total co2-footprint because 
 of large amounts sold , but due to their small specific impact the 
 potential for improvement is limited .
relative global warming potential ( gwp ) 
 in % of the total gwp generated 
 by all considered fruits and vegetables sold in 2007 ( ordered from 
 top to bottom , 2a ) and sales - amount weighted impact per kg of product 
 ( 2b ) .
the error bars denote the minimum and maximum specific impact 
 over all options assessed ( varying origin , means of transportation , 
 production modes , etc . ) .
asparagus was clearly the most important crop to be 
 analyzed according 
 to the ranking scheme applied .
figure 3 shows 
 that the main load of the gwp originates from air transport from mexico 
 and peru .
the carbon footprint of different origins and transportation 
 options differs by a factor of 1619 , respectively , from the 
 lowest ( produced locally in switzerland ) to the highest ( imported 
 by airplane from mexico ( green asparagus ) and peru ( white asparagus ) ) . 

therefore , a recommendation to reduce air transport and to encourage 
 seasonal production from near regions was derived .
gwp of green and white 
 asparagus imported to switzerland from different 
 countries of origin . for the remaining crops , classified as  high 
 priority to 
 reduce the carbon footprint  , the main driver of impact was 
 greenhouse heating with fossil fuels during production out of season . 

for example , a comparison between swiss cucumber production from unheated 
 and heated greenhouses shows a gwp - difference by a factor of more 
 than 10 ( figure 4 ) . a large difference between 
 heated and nonheated production
can also be observed for eggplants 
 ( factor of 6 ) , tomatoes and peppers ( both factor of 4 ) and lettuce 
 ( factor of 10 ) .
emissions including those from fossil fuel - heating 
 are not evenly distributed over the whole season .
the results of the 
 gwp combined with the seasonal heating energy model are shown for 
 a swiss lettuce production in figure 4 .
gwp of cucumbers 
 grown either unheated or in ( with an annual average 
 amount of heating oil ) fossil fuel heated greenhouses ( a ) .
gwp of 
 lettuce at harvesting time produced in a greenhouse for a year - round 
 production ( b ) .
energy demand for cool storage induces less gwp 
 than import by 
 ship from southern countries .
for example comparing kiwis imported 
 from italy and new zealand , import from italy is always less co2-eq .
intensive , even when considering 36% higher yields , which 
 have been reported for new zealand .
different scenarios of the total gwp of the fruits and vegetables 
 assessed reveal a reduction potential of 42% changing from the scenario 
 with air - freighted oversea - asparagus and vegetables produced in heated 
 greenhouses in northern europe to a supply without air transport and 
 fossil fuel heated greenhouse productions . without air transport , 
 asparagus alone bears a gwp - reduction potential of 20% . a similar 
 reduction ( 22% )
can potentially be achieved by avoiding vegetables 
 from heated greenhouses and sourcing them from southern countries 
 during winter and spring , or , even better , from heated greenhouses 
 with waste heat from other industrial processes . in figure 5b ,
the water consumed during the production of selected fruits 
 of different origins is weighted by the water stress index ( wsi ) .
differences in the environmental impact are 
 mostly caused by water scarcity of a specific region and the ratio 
 of irrigated water consumed to the yield .
the impact is clearly visible 
 for the asparagus and avocado production ( figure 5b ) , whereas for the other fruits and vegetables it is not . 
 in some cases , a
 good water performance  can be in 
 contradiction to a  good gwp performance 
, as in the 
 case of citrus fruits from israel ( si , 
 section 15 ) . in other cases ,
both indicators are in accordance , such 
 as in the case of seasonal production of fruits and vegetables from 
 switzerland , which have a low impact with respect to both indicators .
fraction 
 of water stress ( in % and ordered from top to bottom ) 
 caused by the sales volume in 2007 normalized by the sum of water 
 stress of all crops ( 5a ) and sales - amount weighted water stress ( irrigation 
 water ( m)wsi ) per kg of ( 5b ) .
several measures have been implemented to reduce the large impact 
 due to air transport .
products transported by air freight are declared 
 with a label  by air  and the emissions are fully compensated 
 through offsetting schemes . through efficient logistics and
improved 
 storage techniques the amount of white asparagus transported from 
 overseas by ship was increased from 5090% from 2007 to 2009 .
however , 
 green asparagus is still not transported by ship from overseas due 
 to substantial losses . to lower the impact of the green asparagus 
 imported by air - freight the retailer decided not to sell this product 
 at discount prices anymore since spring 2009 . with this measure it 
 was possible to reduce the emissions from air - transported asparagus 
 by 75% from 2008 to 2009 .
in addition , a new production site in taroudant , 
 morocco is being established to avoid air transport dependency .
furthermore , the results of the study were communicated 
 to the purchasing staff ( in the forms of a report , a leaflet and a 
 calculation tool ) to enable an environmentally informed supply chain 
 management for all products .
airplane transport 
 dominated the carbon footprint of fruits and vegetables , that is , 
 asparagus and papaya . a decision recommendation for
consumers could 
 be , for instance , that seasonal consumption of local foods is to be 
 preferred over out - of - season fruits and vegetables that are imported 
 by plane .
for retailers it is recommended to avoid long - distance transports 
 or to prefer transport by ship whenever possible .
these results are 
 in accordance with the studies of jungbluth et al . or sim et al . , but differ 
 from weber et al . , who conclude that 
 foodmiles in the u.s .
another general result is that greenhouse heating 
 may be a key process for vegetables that are grown out of season in 
 colder climates . in many cases ,
heating greenhouses with fossil fuels 
 was more important than ground transport , even if distances were long 
 ( e.g. , south spain to switzerland ) .
thus , during winter and spring 
 it is often better to purchase vegetables that are grown in greenhouses 
 from southern countries , where no heating is needed , while during 
 summer or fall , local production is often better than imports .
however , 
 there is often a trade - off between the relatively low carbon footprint 
 of winter and spring production in southern countries and the water 
 stress induced in these countries , a situation that needs to be carefully 
 assessed case by case .
the use of heating systems with nonfossil energy 
 and particularly waste heat could be a solution which may reduce both 
 carbon footprint and water stress impacts .
some greenhouses functioning 
 with waste heat are already in operation , for example , the greenhouse 
 attached to a municipal solid waste incineration in hinwil , and the tropical centers in frutigen and wolhusen , 
 switzerland , which are heated with geothermal 
 heat ( warm water effluent from a tunnel ) and waste heat from a gas 
 concentration unit respectively . the decision recommendation for
food 
 producers would thus be to search for such alternative heat energy 
 sources or to avoid heating as much as possible .
the latter is already 
 standard practice for organic producers in switzerland , as heating 
 is only permitted to avoid harvest losses from freezing temperatures 
 according to the standards of bio suisse .
emissions by sourcing their greenhouse - grown products locally during 
 the season . in winter and spring
they should look for imports from 
 warmer locations , provided that there are no adverse effects such 
 as water stress ( and further impacts not investigated here ) .
retailers 
 are suggested to use results from lca studies , to decide where to 
 source each fruit and vegetable from , and which aspects to improve 
 in collaboration with the producers in each case .
they could also 
 label best - practice products , although the communication of lca - results 
 to consumers is a challenging task and consumer organizations already 
 warn against too much and too complex information on products .
finally , consumers should buy seasonal products or local products 
 that can be stored over the season as much as possible to avoid both 
 long - distance and air transport , as well as greenhouse heating .
moreover , 
 it is desirable that crops with low specific impact are consumed in 
 large amounts , as is already the case for pear , grape , potato , melon , 
 carrot , etc . to enable such decisions
, policy makers should ensure 
 that retailers label the origin , transportation , and mode of production 
 of their products .
storage energy is in some cases significant , 
 and efficient cooling 
 technologies are fairly important .
nevertheless , local production 
 combined with long storage tends to perform better than long - distance 
 imports from countries like new zealand , which is for certain crops , 
 such as kiwi and apple , a relevant country for imports into switzerland . 

our results are in accordance with blanke et al . , but in contradiction withmil i canals , who considered 540% loss for apples 
 which are stored for 410 months .
the latter assumption is 
 justified for apples consumed in european spring . in many purchasing 
 decisions , retailers or consumers
can generate 
 significant savings in environmental impacts by following simple guidelines 
 as outlined above .
although the study has been made for a swiss retailer , 
 the lci data are adaptable to assortments of other retailers worldwide .
some key pieces of information about 
 the supply chain like crop , origin , transportation mode , and sales 
 numbers were provided by the retailer .
the inventory data are based 
 on this information and use generic data for the production processes , 
 for example , swiss averages from the horticultural association , which 
 produces according to gap .
however , it should be noted that variability 
 is large between regions and even between farms .
for example , eutrophying emissions are a function of many parameters 
 including climatic factors .
thus , our average data is rather uncertain 
 and may need to be revised particularly for countries without gap - tradition 
 in the field of fertilization , yield and machinery use and in case 
 the data is applied to retailers which do not make sure that gap is 
 followed by all suppliers .
the storage lives 
 of the analyzed products vary from 10 days to half a year , something 
 which has , among other factors , an influence on the amount of food 
 losses .
food losses may be significant and should be assessed , although we were not able to collect representative 
 data within this study .
data on food losses are specific for each 
 retailer , supply chain and crop .
thus , such data should be added to 
 the inventory data when performing lca studies . in the particular case of the commissioner of this study ,
it was 
 decided that the highest leverage decisions can be taken on the levels 
 of purchasing decisions of the retailers and communication to producers . 

the rational was that only sustainable products should be offered 
 ( also for social standards which are not discussed in this paper ) , 
 so that the consumers can buy any product without violating minimum 
 standards and the vast majority of customers is covered .
additionally , 
 consumer information such as origin and mode of production of all 
 fruits and vegetables are provided so that environmentally educated 
 consumers have the chance to choose the environmentally friendliest 
 product among those offered .
the results of the implemented 
 measures shows that the reduction potential identified by a lca - analysis 
 and implemented into daily business can lower the overall impact without 
 substantially compromising the company economically .
it also demonstrates 
 the opportunities of retailers for reducing environmental impacts 
 of food consumption .
food products are known to have significant 
 environmental impacts 
 other than climate change and water use impacts .
those other potential 
 impacts should be covered in a lca complementing the carbon and water 
 evaluation to avoid problem shifting .
further environmental effects 
 of concerninclude impacts from land use , eutrophication and toxic 
 effects .
while for some of these impacts ( e.g. , ecotoxicity and eutrophication ) 
 standard assessment methods exist , methodological developments are 
 needed for others ( e.g. , soil fertility , erosion , salinization , and 
 biodiversity impacts ) .
a complete lcia 
 including these impact categories is also needed for a fair comparison 
 between organic and intensive production systems .
furthermore , 
 the assessment could be expanded to an 
 analysis from cradle to grave , including the use phase ( transport from the store to where it is consumed , preparation like e.g. cooking , etc . ) and especially the food losses over 
 the whole chain .
 food production and consumption is known to have significant 
 environmental 
 impacts . in the present work 
 , the life cycle assessment methodology 
 is used for the environmental assessment of an assortment of 34 fruits 
 and vegetables of a large swiss retailer , with the aim of providing 
 environmental decision - support to the retailer and establishing life 
 cycle inventories ( lci ) also applicable to other case studies . 
 the 
 lci includes , among others , seedling production , farm machinery use , 
 fuels for the heating of greenhouses , irrigation , fertilizers , pesticides , 
 storage and transport to and within switzerland . 
 the results show 
 that the largest reduction of environmental impacts can be achieved 
 by consuming seasonal fruits and vegetables , followed by reduction 
 of transport by airplane . 
 sourcing fruits and vegetables locally is 
 only a good strategy to reduce the carbon footprint if no greenhouse 
 heating with fossil fuels is involved . 
 the impact of water consumption 
 depends on the location of agricultural production . for some crops 
 a trade - off between the carbon footprint and the induced water stress 
 
 is observed . 
 the results were used by the retailer to support the 
 purchasing decisions and improve the supply chain management . 
Introduction
Materials and Methods
Results
Discussion
Outlook