The food cold-chain and climate change
S.J.James *,C.James
Food Refrigeration and Process Engineering Rearch Centre (FRPERC),The Grimsby Institute of Further and Higher Education (GIFHE),HSI Building,Europarc,Grimsby,North East Lincolnshire DN379TZ,UK
a r t i c l e i n f o Article history:
Received 10November 2009Accepted 1February 2010
Keywords:Food
Climate change Cold-chain Refrigeration Energy usage Chilling Freezing
a b s t r a c t
Any noticeable increa in ambient temperature resulting from climatic change will have a substantial effect on the current and developing food cold-chain.A ri in temperature will increa the risk of food poisoning and food spoilage unless the cold-chain is extended and improved.The little data that is avail-able suggests that currently the cold-chain accounts for approximately 1%of CO 2production in the world,however this is likely to increa if global temperatures increa significantly.Using the most energy effi-cient refrigeration technologies it would be possible to substantially extend and improve the cold-chain without any increa in CO 2,and possibly even a decrea.
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1.Introduction
Climate change has been described as ‘the single most impor-tant issue that we face as a global community’(Blair,2004).Many recent publications (Brander,2009;Frar,2006;Gregory,2009;Miraglia et al.,2009;Patterson &Lima,2010)that consider rela-tionships between climate change and food concentrate,on pre-harvest factors.While Jacxns et al.(2009)look at the food supply chain but not the refrigeration aspects of it.This review concen-trates on the relationship between the refrigerated cold-chain for food and climatic change.
Refrigeration stops or reduces the rate at which changes occur in food.The changes can be microbiological (growth of microor-ganisms),physiological (e.g.ripening,nescence and respiration),biochemical (e.g.browning reactions,lipid oxidation and pigment degradation)and/or physical (isture loss).An efficient and effective cold-chain is designed to provide the best conditions for slowing,or preventing,the changes for as long as it is practical.Refrigeration is important in both maintaining the safety and quality of many foods and enabling food to be supplied to an increasingly urbanid world.In reality,less than 10%of such per-ishable foodstuffs are in fact currently refrigerated (Coulomb,2008).It is estimated that post-harvest loss currently account for 30%of total production (Coulomb,2008).The production of
food involves a significant carbon investment that is squandered if the food is then not utilid.Thus t
here is a balance to be achieved.The International Institute of Refrigeration (IIR),(2009)estimate that,in theory,if developing countries could acquire the same level of refrigerated equipment as that in industrialized countries,over 200million tonnes of perishable foods would be prerved,this being roughly 14%of the current consumption in the countries (Table 1).
So,what is the relationship between the cold-chain and climatic change?Before undertaking a review of publications on the topic it is important to be clear what we are trying to review.After much thought,we consider that there are two very different aspects to the question:
1.What will be the effect of climatic change,especially the pre-dicted increa in average world temperature,on the cold-chain?
2.How much does the cold-chain,and potential changes to it,
contribute to climatic change,especially an increa in world temperature?When considering the cond question,are there new technol-ogies,changes to existing technologies,or alternative process,that could make a substantial difference in the future?
The food manufacturing industry utilis chilling and freezing process as a means of prerving fo
ods.Refrigeration of the foods is continued during transportation,retail distribution and home storage to maintain the foods at the desired temperatures.The are important steps in maintaining the safety,quality and
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*Corresponding author.Tel.:+44(0)1472582400.
虽然的近义词E-mail address:jamess@grimsby.ac.uk (S.J.James),jamesc@grimsby.ac.uk (C.James).
URL: (C.James).
shelf life of foods for the consumer,and the process from primary cooling through to domestic storage make up the‘food cold-chain’.
There have been a number of international reports on the im-pact of climate change on‘‘access to food”and‘‘food curity”(Schmidhuber&Tubiello,2007).Access to food refers to the ability of individuals,communities,and countries to purcha sufficient quantities and qualities of food.Over the last30years,falling real prices for food and rising real incomes have led to substantial improvements i
n access to food in many developing countries.In-cread purchasing power has allowed a growing number of peo-ple to purcha not only more food but also more nutritious food with more protein,micronutrients,and vitamins.Climate change will increa the dependency of developing countries on imports and accentuate existing focus of food incurity on sub-Saharan Africa and to a lesr extent on South Asia(Schmidhuber&Tubi-ello,2007).As Garnett(2008a)states,while all regions of the world will ultimately suffer from the conquences of a warming climate, agricultural production in northern latitudes(including the UK), may initially benefit.Countries in the southern hemisphere,on the other hand,and particularly tho that are already agricultur-ally vulnerable are already beginning to suffer the negative con-quences of a warmer,more volatile climate.They will not be able to grow as much or be as confident about the yield as they can cur-rently are so the number of people at even greater risk of hunger will grow.There is therefore a strong moral ca for countries to ensure that their farming ctor is robust enough to grow enough food not just for their own populations,but also for people over-as(Garnett,2008a,2008b).Conquentially an effective and effi-cient cold-chain will be required to deliver this food around the world.
To provide safe food products of high organoleptic quality, attention must be paid to every aspect of the cold-chain from ini-tial chilling or freezing of the raw ingredients,through storage and transport,to
函数零点的求法
retail display.Removing the required amount of heat from a food is a difficult,time and energy consuming operation,but critical to the operation of the cold-chain.As a food moves along the cold-chain it becomes increasingly difficult to control and maintain its temperature.This is becau the temperatures of bulk packs of refrigerated product in large storerooms are far less nsi-tive to small heat inputs than single consumer packs in open dis-play cas or in a domestic refrigerator/freezer.Failure to understand the needs of each process results in excessive weight loss,higher energy u,reduced shelf life or a deterioration in product quality.
If climatic change results in a substantial ri in average ambi-ent temperatures this will impo higher heat loads on all systems in the cold-chain.In systems that have capacity to cope with the higher loads this will just require the refrigeration plants to run for longer periods and u more energy.In many other cas during cooling operations the food will take longer to cool or during temperature maintenance process the food temperature will not be maintained at current levels.In Section2we review the likely effect of climate change on the cold-chain.
A substantial amount of energy is ud just to maintain the cur-rent cold-chain and as countries develop their own cold-chains this will increa.In Section3,using available literature,an attempt has been made to identify the current major us of energy in the food cold-chain and the changes that a
re likely to occur in the future.In addition to the generation of CO2the refrigerants currently ud in cold-chain have considerable global warming potential(GWP). Using existing technology substantial savings in the energy ud per unit of product could be achieved and the are reviewed in Section4.In thefinal ction the u of alternative refrigerants and alternative refrigeration cycles with a reduced GWP are reviewed.
2.The effect of climatic change on the cold-chain
It is reported that,between1900and2005,there has been a 0.45°C ri in average world temperature(Carbon Disclosure Pro-ject,2006).The rate of ri appears to be increasing with a0.1°C ri in last9years.Local ris can be much higher,in the UK in thefirst quarter of2007temperatures were on average2.1°C war-mer than in thefirst quarter of2006(Department of Trade and Industry(DTI),2007).However,such changes could be due to nat-ural variability.In Australia(Commonwealth Scientific and Indus-trial Rearch Organisation,2001),it is estimated that global warming will cau temperatures to ri0.4–2°C by2030,and 1–6°C by2070.
There is clear evidence that food poisoning in many countries is affected by asonal changes,with a higher incidence in the sum-mer and fewer cas during the winter(Bentham,2002;Hall, D’Souza&
Kirk,2002).Hot summers may produce particularly large increas in food poisoning.There is thus concern that a ri in global temperatures due to global warming will bring with it a subquent ri in the incidence of food poisoning(Schmidhuber &Tubiello,2007).High temperatures favour the multiplication of pathogenic microorganisms in food.For example,multiplication of the salmonellas is strongly temperature dependent with growth occurring above about7°C and reaching an optimum at37°C (Bentham,2002).Semenza and Menne(2009)state that colonisa-tion of broiler chickenflocks with campylobacter also increas rapidly with rising temperatures.The risk of campylobacteriosis is positively associated with mean weekly temperatures,although the strength of association is not consistent in all studies.Warmer summer temperatures and humid conditions can enhance the survival of microbes in the environment,leading to incread con-tamination of food,and incread risk of infection(Charron,Walt-ner-Toews,&Maarouf,2005).High temperatures may also affect infection rates in food animals,for example by the multiplication of bacteria in animal feed(Bentham,2002).In addition,some a-sonal behaviour may also exacerbate the risk of food dia trans-mission,such as outdoor barbequing,al fresco meals,etc. (Bentham,2002;Charron et al.,2005).On farms,the microbial ecology may change with altered climate,potentially changing the species composition of pathogens and their infectivity to peo-ple(Charron et al.,2005).
寒食节是什么节日
A number of studies have investigated the direct relationship between environmental temperatures and the occurrence of food poisoning.D’Souza,Becker,Hall,and Moodie(2003)found a sig-nificant positive association between mean temperature of the previous month and the number of salmonellosis notifications in the current month infive Australian cities,with the estimated in-creas for a1°C increa in temperature ranging from4%to10%, depending on the city.Kovats et al.(2004)found,on average,a
Table1
Refrigeration requirements and loss due to lack of refrigeration(adapted from International Institute of Refrigeration(IIR),2009).
World population Developed
countries
Developing
countries
Population in2009(billion
inhabitants)
6.83 1.23 5.60
社团申请书
Refrigerated storage capacity
(m3/1000inhabitants)
5220019
Number of domestic refrigerators
(/1000inhabitants)
17262770
Food loss(all products)(%)251028 Loss of fruit and vegetables(%)351540
Loss of perishable foods through a lack of refrigeration(%)20923
S.J.James,C.James/Food Rearch International43(2010)1944–19561945
linear association between temperature and the
ported cas of salmonellosis above a threshold of
tionships were very similar in The Netherlands,
Wales,Switzerland,Spain and the Czech Republic.
Charron,Holt,Allen,and Maarouf(2006)found a
tion between ambient temperature and the
enteric pathogens(Salmonella,pathogenic
Campylobacter)in Alberta,Canada,and of
foundland-Labrador.However,the relationships驴成语
For Alberta,the log relative risk of Salmonella,
li weekly ca counts incread by1.2%,
respectively,for every1°C increa in weekly
For Newfoundland-Labrador the log relative risk
for Campylobacter for every1°C increa in weekly mean
temperature.
A number of countries have made projections of the effect of cli-mate change on the increa in cas of food poisoning.A UK report (Bentham,2002)in2001/2002estimated that cas in the UK could ri by about10,000extra cas per year.A further revision of this report in2008(Bentham,2008)considered that there were no grounds for revising that estimate.While an Australian report estimates that cas in Australia could ri to around79,000addi-tional cas per year by2050(Department of Climate Change, 2009).
It is very clear from the microbiological data,that if the food industries respon to a2–4°C ri in ambient temperatures,were to allow a similar ri in the temperature of chilled food then food poisoning and spoilage would increa.It is an accepted crude approximation that bacterial growth rates can be expected to dou-ble with every10°C ri in temperature(Gill,1986).Below10°C, however,
this effect is more pronounced and chilled storage life is halved for each2–3°C ri in temperature.Thus the generation time for a pudomonad(a common form of spoilage bacteria) might be1h at20°C,2.5h at10°C,5h at5°C,8h at2°C or 11h at0°C(Harrigan&Park,1991).In the usual temperature range for chilled meat,À1.5°C to5°C,for example there can be as much as an eightfold increa in growth rate between the lower and upper temperature.Surveys of temperatures in chilled retail display cabinets show that temperatures can range fromÀ1°C to 16°C(Evans,Scarcelli,&Swain,2007;James&Evans,1990),whilst mean temperatures in domestic refrigerators throughout the world range from5to6°C,with many operating at significantly higher temperatures(James,Evans,&James,2008).Thus,it is clear that the temperatures achieved in both retail display and domestic storage,need to be lowered rather than allowed to ri in the fore-eable future if food safety is not to be compromid and high quality shelf life assured.Keeping food at current or lower temper-atures will result in an increa in the energy ud by food refrig-eration systems as ambient temperatures ri.Sarhadian(2004) measured the average power consumed by refrigeration equip-ment in a catering establishment in different ambient(Fig.1). Increasing the ambient temperatures from17to25°C resulted in an11%increa in average power consumed.
In addition,if climate change were to result in higher levels of microorganisms being prent on meat
s and produce prior to pro-cessing it could have a significant affect on the shelf life or storage requirements of chilled foods.With higher numbers,fewer dou-blings are required to reach a spoilage level of ca.108organisms/ cm2.For example,at a specific temperature,starting with one organism/cm2,27doublings would be needed;while for an initial load of103organisms/cm2,the number of doublings is reduced to 17.Thus lower storage temperatures may be needed to maintain required shelf-lives.
Currently food is frozen to and generally maintained at a temper-ature belowÀ18°C throughout storage,transport,retailing and domestic storage.In the ca of frozen food,if the food industries respon to a2–4°C ri in ambient temperatures were to allow a similar ri in the food temperature,then food poisoning and spoil-age would not increa.However,if this were universally adopted then the high quality storage life of many temperature nsitive food products including ice cream,frozen desrts,oilyfish and tuna would deteriorate.
3.The effect of the cold-chain on climatic change
Energy is required to maintain the cold-chain and the genera-tion of this energy contributes to CO2production and climatic change.In addition the manufacture and direct loss of refrigerant ud in
the refrigeration systems also contributes.However,it is difficult to obtain reliable data on the contribution either source actually makes.
Mattarolo(1990)estimated that40%of all food requires refrig-eration and that15%of the electricity consumed worldwide is ud for refrigeration.This15%figure is in agreement with International Institute of Refrigeration estimates(Coulomb,2008).Estrada-Flores and Platt(2007)estimated that the total energy spent in the Austra-lian food industry to keep an unbroken cold-chain from farm to consumer is about19,292GW h/year,or18MtC(Million tonnes of Carbon).In the UK,food,drink and tobacco manufacturers u more energy than is ud in iron and steel production(Department for Environment,Food and Rural Affairs,2006).Around14%of total energy consumption is ud in producing and processing food (Department of Trade and Industry(DTI),2002),with11%of elec-tricity consumed by the food industry,totalling22.4MtC for food and catering(Department for Business Enterpri and Regulatory Reform,2005).The food and drink manufacturing,food retail and catering ctors are currently responsible for approximately4%of the UK’s annual greenhou gas emissions(Anon.,2007).With about2.4%of the UK’s greenhou gas emissions due to food refrig-eration(although‘embedded’refrigeration in foods grown or man-ufactured and imported from overas,could increa thisfigure to at least3–3.5%)(Garnett,2007).The Carbon Disclosure Project
Re-port(Carbon Disclosure Project,2006)states that worldwide food only accounts for1%of total CO2emissions.
In addition,detailed estimates of what proportion of this is ud for refrigeration process in the cold-chain are less clear and often contradictory(James et al.,2009).Garnett(2008a)states that in the UK food and drink related refrigeration includ-ing refrigeration in supermarkets,catering outlets,pubs and cel-lars,staff catering and so forth)emissions work out at1.46MtC, equivalent to0.97%of the UK’s CO2emissions,and refrigerant leak-ages contribution to the UK’s total GHG emissions is also0.97%.In addition Garnet states that280,000tC is ud by refrigeration sys-tems in food manufacture and1.9MtC in domestic refrigeration.
Looking at individual operations through the cold-chain and commodities provides some idea of which combinations contrib-ute most to climate change.
Fig.1.Relationship between power consumed in refrigeration plant in a catering establishment and ambient temperature(adapted from Sarhadian,2004).
1946S.J.James,C.
3.1.Primary chilling and condary cooling
Primary chilling is thefirst and most important stage of the cold-chain for a refrigerated food.The rate of temperature reduc-tion often determines the subquent safety and quality of the food.In primary cooling systems,the majority of the total heat load should be the product load since the purpo of a primary chilling system is to extract this load.The total product heat load is depen-dent on the type of food product,its initial temperature(at harvest or slaughter),thefinal temperature to which the product is re-quired to be cooled to prior to storage,and the mass of the product that is being cooled.The rate of relea of heat from the food is also a function of the chilling system ud,its operating temperature(s) and the heat transfer coefficient(s)achieved.
Swain,Evans,and James(2009)calculated the energy required to cool different raw food materials using the overall weight of an-nual UK production multiplied by the enthalpy change required to reduce the temperature post-harvest/slaughter to its recom-mended storage temperature.In the UK,milk is the raw material that requires the most cooling with an estimated energy value at least2.5times more than all the other major materials added to-gether and over4.5times more than all types of meat combined. In addition to milk and meat the primary chilling of vegetables, especially potatoes,requires the extraction of substantial quanti-ties of heat.
3.2.Transportation
Sea,air and land transportation systems are expected to main-tain the temperature of the food within clo limits to ensure its optimum safety and high quality shelf life.It is estimated that there are approximately1300specialid refrigerated cargo ships, 80,000refrigerated railcars,650,000refrigerated containers and 1.2million refrigerated trucks in u worldwide(Heap,2006). The type of transportation ud will substantially affect the energy ud.It has been estimated that the same amount of fuel can trans-port5kg of food only1km by personal car,43km by air,740km by truck,2400km by rail,and3800km by ship(Brodt,Chernoh, &Feenstra,2007).Refrigeration accounts for roughly40%of the to-tal energy requirement during distribution,making the distribu-tion of frozen food around1.7times as energy-intensive as the distribution of groceries at ambient temperature(McKinnon& Campbell,1998).
Air-freighting is increasingly being ud for high value perish-able products,such as strawberries,asparagus and live lobsters (Sharp,1988;Stera,1999).However,foods do not necessarily have to fall into this category to make air transportation viable since it has been shown that‘the intrinsic value of an item has little to do with whether or not it can benefit from air shipment, the deciding factor is not price but mark-up and profit’(American Society of Heating,Refrigerating and Air-Conditioning Engineers, 2006).Air is the most intensive form of transport with the highest CO2em
issions per tonne of the commercial transportation sys-tems(AEA Technology,2005;Department for Environment,Food and Rural Affairs,2005;Garnett,2008a).UK studies show that while less than1%of all food consumed in the UK is carried by air it accounts for11%of total food transport CO2(including car trips),1.5%of fruit and vegetables are carried by air but it ac-counts for40%of the total CO2(or50%of freight CO2)ud in transport of vegetables.
Over a million refrigerated road vehicles are ud to distribute refrigerated foods throughout the world(Billiard,2005;Gac, 2002).Freight transport consumes nearly25%of all the petroleum worldwide and produces over10%of carbon emissions from fossil fuels(Estrada-Flores,2008).Food transport accounts for one quar-ter of all Heavy-Goods Vehicle miles in the UK,with the average number of miles that food travelling doubling in the last30years (Department for Environment,Food and Rural Affairs,2005).It has been reported in that in the US foods are typically transported over an average distance of2100km before arriving on the con-sumer’s plate(Miller,2001).A study by Nestlédemonstrated that transport generated roughly15kg of CO2emissions per tonne of product delivered.This reprents approximately10%of the total CO2generated during the manufacturing process(Carbon Disclo-sure Project,2006).
Transport of food,consumed in the UK,accounted for an esti-mated30billion vehicle kilometres in200
2,of which82%were in the UK(AEA Technology,2005).Road transport accounted for most of the vehicle kilometres(Table2),split between cars,HGVs (Heavy-Goods Vehicles)and LGVs(Light Goods Vehicles).Food transport produced19million tonnes of carbon dioxide in2002, of which10million tonnes were emitted in the UK(almost all from road transport),reprenting1.8%of the total annual UK CO2emis-sions,and8.7%of the total emissions of the UK road ctor(AEA Technology,2005).The role of the consumer of this food should not be discounted either.It has been estimated that around one in ten car journeys in the UK are for food shopping(Department for Transport,2007).
Improvements in energy efficiency would not only cut distribu-tion costs,but also reduce atmospheric emissions.The u of die-l-powered refrigeration equipment substantially increas the level of emissions per tonne of product distributed.Unlike lorry tractor units,which have been subject to tightening EU emission standards,the refrigeration motors on much of the‘reefer’trailer fleet continue to produce high levels of noxious emissions per litre of fuel consumed(McKinnon&Campbell,1998).The ri in super-market home delivery rvices where there are requirements for mixed loads of products that may each require different storage temperatures is also introducing a new complexity to local land delivery(Cairns,1996).
The concept of‘‘food miles”is clearly of concern to countries with well-established export markets,suc
h as Australia and New Zealand.However a comparison of dairy and sheep meat pro-duction by Saunders,Barber,and Taylor(2006)concluded that New Zealand produced products for the UK market were‘‘by far more energy efficient”than tho produced in the UK.This included the energy ud in transportation.With production being twice as efficient in the ca of dairy,and four times as efficient in ca of sheep meat.This reflects the extensive production system in New Zealand compared with the UK and the proportion of energy ud and carbon produced during the production of food rather than in its processing and transportation.
Table2
Transport emissions,estimated for transporting food from its source to UK stores and onto consumers homes(adapted from AEA Technology,2005).
Transport mode CO2emissions as a
proportion of total
food transport
emissions(%)
Transportation
(tonne-km)as a
proportion of total
transportation(%) (UK road total commercial)3935
UK road HGV a3319
UK road private cars1348
Overas road HGV a127
International by a120.04
International HGV a125
International air freight110.1
UK road LGV b616
Overas road LGV b25
Rail,inland waterways Insignificant Insignificant
a HGV=Heavy-Goods Vehicles.
b LGV=Light(Local)Delivery Vehicles.
S.J.James,C.James/Food Rearch International43(2010)1944–19561947
3.3.Storage
Following harvesting/production many foods are transported to centralid‘‘cold stores”(Europe)or‘‘refrigerated warehous”(US)prior to distribution to retailers/end-urs.Cold stores may be chilled or frozen and operate at a range of different tempera-tures depending on the product or customers requirements.When correctly ud the facilities are only required to maintain the temperature of the product.
There is limited published data on energy consumption in cold stores(Duiven&Binard,2002;Famarazi,Coburn,&Sarhadian, 2002;Werner,Vaino,Merts,&Cleland,2006)赵温
.The energy con-sumption of cold-stores depend on many factors,including the quality of the building,activities(chilled or frozen storage),room size,stock turnover,temperature of incoming product,external environmental conditions,etc.(Duiven&Binard,2002).
FRPERC has carried out a comprehensive study of three large cold store complexes in the UK(James et al.,2009).The actual per-formances of the cold stores per cubic and square metre are shown in Table3.
It is common practice in the frozen food industry to u refrig-erated trailers as overspill storage space.In a survey of1300refrig-erated trailers over a48h period,it was found that roughly afifth of their time was spent loaded and stationary(McKinnon&Camp-bell,1998).
3.4.Catering
Refrigerated Commercial Service Cabinets(CSCs)are ud to store food and/or drink in commercial catering facilities.There are approximately500,000units in u in the UK(Market Transfor-mation Programme,2006).The vast majority of the cabinets sold are integral cabinets(refrigeration system on board the unit).Most of the market is for chilled or frozen upright cabinets with one or two doors or under counter units with up to four doors.The aver-age energy consumption for chilled cabinets is29
20kW h/year and for frozen is5475kW h/year(Market Transformation Programme, 2006).
The limited published data on energy consumption of CSCs in u are shown in Fig.2.Although each cabinet type is of similar size and therefore can be directly compared in terms of functional-ity,there is a large difference in energy consumed by each type of CSC.
There are over4million refrigerated vending machines in the USA consuming12billion kW h of electricity per year(Refrigera-tion Technology&Test Centre(RTTC),2009a).They consume be-tween7and16kW h per day,which is typicallyfive times more electricity than a domestic refrigerator.Ambient temperature has a substantial affect on energy consumption.An8°C ri in ambi-ent from24to32°C resulting in a40%increa in energy consumption.3.5.Retail
In2002it was estimated that there were322,000supermarkets and18,000hypermarkets worldwide and that the refrigeration equipment in the supermarkets ud on average35–50%of the total energy consumed in the supermarkets(United Nations Environment Programme,2002).In a US survey of a store(Refrig-eration Technology&Test Centre(RTTC),2009b)68%of its total annual electric u was attributed to refrigeration,with only8% to heating,ventilation and air conditioning,and23%to lighting. For a typical size food retail store,3500MW h of electrical energy will
be consumed in a year,of which2100MW h can be due to the refrigeration systems(Evans et al.,2007).In the retail environment the majority of the refrigeration energy is consumed in chilled and frozen retail display cabinets(James et al.,2009).
3.6.Domestic
Domestic refrigerated storage is an often-unregarded part of the food cold-chain by the food industry.However,from an environ-mental point of view this ctor is important.There are approxi-mately1billion domestic refrigerators worldwide(International Institute of Refrigeration(IIR),2002).At prent,most of the are in industrialized countries.However(as noted by Billiard, 2005),production in developing countries is rising steadily(30% of total production in2000).When the environmental impact of the refrigerators is considered using a LCCP(Life Cycle Climate Performance)approach,the emissions of refrigerant in a domestic HFC-134a refrigerator reprent only1–2%of the total contribu-tion to global warming while emissions due to energy consump-tion reprent98–99%(Billiard,2005).Therefore,energy consumption is the most significant issue with regards to global warming.In a study on ketchup,Anderson,Ohlsson,and Olsson (1998)found that energy ud in long-term storage in home refrig-erators can dwarf energy u in any other ctor of the ketchup life cycle by a factor of two or more,and fuel ud for consumer shop-ping can be as mu
ch as fuel ud in all other transportation earlier in the life cycle,on a per kg basis.
3.7.Overall
On the best available data,James et al.(2009)identified the top ten process,excluding domestic systems,in the UK cold-chain in terms of energy saving potential as shown in Table4.The saving potential within the topfive consuming operations in the UK
Table3
Energy consumed by each cold store.
Refrigeration plant kW h/
year kW h/
year/m3
kW h/炖牛肉怎么炖
year/m2
Cold store1(3frozen chambers
1550m2)
710,33557.3458.3
Cold store2(1frozen chamber910m2)652,57371.1710.6
Cold store3(3chilled and1frozen
chamber total2458m2)
1138,17857.9463.1
Stores1and3were operated by a direct expansion refrigeration system with single stage reciprocating compressors and evaporative condenrs.Store2was operated from a low pressure receiver system with a twin screw economized compressor and an air cooled condenr.All stores were operated on R22.
1948S.J.James,C.James/Food Rearch International43(2010)1944–1956
(retail,catering,transport,storage and primary chilling)was esti-mated to lie between4300and8500GW h/year in the UK.
As yet few other studies appear to have looked at the cold-chain.Work in Germany on thefish cold-chain found that retailing consumed over six times the energy of the next most energy-inten-sive operation of spiral freezing(Meurer&Schwarz,2003).While Ramirez,Patel,and Blok(2006)reported tha
t the specific energy consumption required to produce frozen carcass meat was far higher than for chilled(Table5).Further processing the meat to produced cut up and deboned products further incread the en-ergy required.In Europe the amount of energy required to produce a tonne of meat has incread by between14%and48%between 1990and2005(Ramirez et al.,2006).
3.8.Refrigerants
About20%of the global-warming impact of refrigeration plants is due to refrigerant leakage(March Consulting Group,1998). However,it depends of cour on the applications:for domestic refrigerators,for example,thefigure is2%;while for mobile air conditioning,thefigure is37%.Refrigerant leakage can be up to 15%per year in commercial refrigeration plants(Coulomb,2008), and leakage varies greatly from one system to another.
The dominant types of refrigerant ud in the food industry in the last sixty years have belonged to a group of chemicals known as halogenated hlorofluorocarbons(CFCs)and the hydrochlorofluorocarbons(HCFCs).Scientific evidence clearly shows that emissions of CFCs have been damaging the ozone layer and contributing significantly to global warming.Conquentially the Ozone Depletion Potential(ODP),the Global Warming Poten-tial(GWP)and the Total Equivalent War
ming Impacts(TEWI)have become the leading criteria in the choice of refrigerants today(Dui-ven&Binard,2002).
The importance of the criteria has changed over the years.Ini-tially the greatest concern was stratospheric ozone protection, with the Vienna Convention and resulting Montreal Protocol forc-ing the abandonment of Ozone-Depleting Substances(ODSs), resulting in the replacement of CFCs by HCFCs(Calm,2008).This has broadly shown some success and there is evidence of ozone recovery(Calm,2008).More recently climate change has become the prime motivator for concern and change and thus the GWP and TEWI of refrigerants has become important.The Kyoto Proto-col,pursuant to the international Framework Convention on Cli-mate Change,ts binding targets for greenhou gas(GHG) emissions bad on calculated equivalents of carbon dioxide, methane,nitrous oxide,hydrofluorocarbons(HFCs),perfluorocar-bons(PFCs),and sulphur hexafluoride.National laws and regula-tions to implement the Kyoto Protocol differ,but they typically prohibit avoidable releas of HFC and PFC refrigerants and in some countries also control or tax their u(Calm,2008).Within the European Union the are generally referred to as‘‘F-gas”regulations.
The retail ctor,including supermarkets,is one of the largest urs of F-gas(fluorinated greenhou
gas)refrigerants.In the UK,emissions due to leakage of HFC refrigerants from all types of stationary refrigeration was estimated to be equivalent to 1740,000tonnes of CO2in2005,with leakage from supermarket refrigeration systems contributing769tonnes(AEA Technology, 2004).
Thefirst reaction of the refrigeration and chemical industries to the Montreal Protocol was to look for interim refrigerants,most bad on R22,with friendlier environmental properties that could be ud until optimum alternatives could be developed.Interim replacements for R502for example were Isceon69S and69L,Suva HP80and HP81and Atochem FX10.Suva MP39and MP66were in-terim replacements for R12.Hydrofluorocarbon R134a has been the popular choice to replace R12in a wide range of food refriger-ation and air conditioning applications.The include most of the commercial applications that ud R12and in domestic refrigera-tors.R134a does not contain chlorine and,therefore,has an ODP of zero and,similarly to R12,has low toxicity levels and a low boil-ing point.However,134a has a global warming potential(GWP)of 1300while European rules require any new refrigerant to have a GWP of less than150.
Further developments have produced refrigerants with lower GWP.Hydrofluorocarbon R152a is almost a straight drop-in substi-tute for R134a(Mohanraj,Jayaraj,&Muraleedharan,2008)and has a GWP of120,which is ten times less.It has similar operating char-acteristics to R134a,improved coolin
g ability,and typically only requires two-thirds the charge of R134a(AA1car,2009).HFO-1234yf is another new replacement for R134a and has a GWP of only4.A report produced by SAE International(2008)claims that HFO-1234yf is the best replacement refrigerant for R134a.
R502is the preferred refrigerant in supermarket and food trans-port systems.Many chemical companies have worked on a long-term alternative to R502with a zero ODP.Dupont produced Suva 62,ICI Klea60,Rhone-Poulene Isceon RX3and Atochem.Sol-kane507,with an ODP of0and a GWP of0.84,now claims to be ‘in practice’the optimal replacement for R502(Solpac,2009).
Table4
Best estimate of the top ten food refrigeration process ranked in terms of their potential for total energy saving(basis of estimations provided imsby.ac.uk/ documents/defra/usrs-top10urs.pdf).
Sector Energy Saving
‘000t CO2/year GW h/year%GW h/year
1Retail display3100–68005800–12,70030–506300 2Catering–kitchen refrigeration2100400030–502
000 3Transport1200480020–251200 4Cold storage–generic50090020–40360 5Blast chilling–(hot)ready meals,pies167–330309–61020–30180 6Blast freezing–(hot)potato products120–220220–42020–30130 7Milk cooling–raw milk on farm50–170100–32020–30100 8Dairy processing–milk/chee13025020–3080 9Potato storage–bulk raw potatoes80–100140–190$3060 10Primary chilling–meat carcass60–80110–14020–3040
Table5
Specific energy required(MJ/t)to chill,freeze and process(cutting and deboning)
克服懒惰meat(adapted from Ramirez et al.,2006).
Product Whole and
chilled Whole and
frozen
Cut,deboned and
frozen
Beef,veal and
sheep
139021102866
Pork209331283884
Poultry30964258–55185014–6274
S.J.James,C.James/Food Rearch International43(2010)1944–19561949
