电子回收作为一种能效措施外文文献

Electronics recycling as an energy effi ciency measure e a Life Cycle Assessment LCA study on refrigerator recycling in Brazil Anne Sophie Foelster a Stefan Andrewa Leonardo Kroegerb Philipp Bohrb Tina Dettmer a Stefan Boehmea Christoph Herrmanna aChair of Sustainable Manufacturing accurate as it makes use of cut off criteria to balance cost and increased precision conservative as engineering judgement is used only on minor mass fl ows with small expected impacts and because missing data for the geographic region are imputed from more effi cient production leadingtounderestimationoftherecycling benefi ts consistent as it follows one ISO standard and transparent as it discusses its assumptions and limitations The recycling of the refrigerators at Ind stria Fox is a so called open loop recycling OLR and therefore the specialities of this kind of process are explained in the following Life Cycle Assess ments with OLR distribute the impact to two systems combined by the OLR in accordance to the 50 50 or the cut off allocation rule The avoided disposal processes as well as the prevented environ mental impacts through raw material extraction are allocated to the respective system 50 50 or not considered cut off Kl opffer and Grahl 2009 Both rules do not completely apply to the recy cling company Ind stria Fox as this is a reverse production process Nevertheless the principles can be applied Therefore the company avoids a most likely not proper and environmentally friendly disposal and produces at the same time secondary raw materials that substitute primary raw materials Following the allocation rules of waste LCAs the credits can be assessed through an equiv alence system Kl opffer and Grahl 2009 With this method various recovery options of end of life vehicles have been assessed While the recycling system produces certain products from the waste input the complementary system disposes of the same waste input and produces an equivalent set of complementary products Recycling product and complementary product must both fulfi l the same function To achieve this a mass correction with the substi tution factor S can be calculated as followed S mcp mrp 7 with mcp for the function specifi c mass of the complementary product and mrpfor the recycling product N rrenbach et al 2005 3 2 Goal and scope defi nition The goal of the study is to quantify the reduction of the energy demand and the reduction of GHGs that can be achieved by recy cling refrigerators in Brazil Furthermore it is the target to evaluate recycling as an energy effi ciency measure in accordance with the evaluation frameworks used by Brazilian authorities Therefore the energy demand and GHG emissions associated with collecting sorting and processing secondary raw material are compared with the use of primary raw materials and the conventional disposal of refrigerators The case study compares the impact categories cu mulative energy demand and climate change potential of the recycling system with an equivalence system using the method of Life Cycle Assessment as defi ned in ISO 14040 ISO 14044 The compared systems were modelled and calculated with openLCA v1 4 1 The recycling system evaluates the refrigerator reverse pro duction with all activities from the collection of old waste re frigerators to their reprocessing in the manufacturing industry including cleaning sorting etc Auxiliary materials are traced from cradle to their utilization in the recycling process In the equiva lence system the waste is disposed of corresponding to the state of the art in Brazil and the equivalent amount of primary raw mate rials which the recycling system produced as secondary raw ma terial is produced from cradle to gate The equivalence system is further specifi ed in the life cycle inventory see chapter 3 4 Con struction of the recycling plant maintenance of the machines and particulate matter and trace gas emissions are ignored As water consumption has no signifi cant effect neither on climate change nor cumulative energy demand it is only considered to obtain a correct mass balance Comparison is done by the functional unit defi ned as the disposal of 1000 refrigerators and the specifi c use of each sub product resulting from refrigerator recycling For com parison of primary and secondary products mass allocation was employed for the Ind stria Fox multi output system The system boundaries of the LCA with the inputs and outputs can be seen in Fig 1 and more detailed in Table 3 in subchapter 3 4 1 Within the LCA system boundary are the three phases of the recycling process at Ind stria Fox The inputs into the system are on the one hand the waste refrigerators but also energy sources e g for the machines and raw and auxiliary materials On the output side the various parts and materials for re use and recycling respectively leave the system together with waste and emissions The largest share of the recovered materials are recycled and brought back into the value chain and therefore substituting pri mary materials 3 3 Data acquisition Ind stria Fox s internal mass emissions and energy fl ows have been measured auxiliary material and input fl ows have been quantifi ed byaveragecompany data from2014 Recycling processes carried out by third parties have been specifi ed by information provided by the latter or assumptions made on the respective process For the production of electricity complementary products etc data has been obtained from literature and ecoinvent data bases v3 1 and v2 2 one process 3 3 1 Tests for mass and energy balance Two tests with a sample size based on CENELEC standard BSI 2014 have been conducted 1002 randomly selected PU foam insulated and 736 glass wool insulated refrigerators were pro cessed The glass wool appliances are the oldest generation of re frigerators arriving at Ind stria Fox They contain approx 60 wt of ferrous metals and only 7 wt of plastics Apart from the insulation material this ferrous metal and plastics content is the main difference to the PU foam devices which contain 20 wt of plastics and only about 45 wt of ferrous metals which corre sponds with other studies on refrigerators Liu et al 2009 An overview over the material composition of these two refrigerator classes can be seen in Fig 2 These appliance classes account for 89 of all recycling activity with PU foam appliances contributing 64 and glass wool appliances 36 refl ecting the respective weights for the functional unit The mass balance was obtained by using the weight of input refrigerators and output fractions while electricity meters were installed to determine the energy fl ows of the system The Ind stria Fox recycling systemhas been divided into six processes see Fig 3 Administration and logistics include transport activities and the electricity used for administrative activities Recycling activities are divided into manual disassembly mechanical processing nitro gen production pelletising and the gas processing Output weight and electricity consumption have been determined as well as the input weight of oil cooling and blowing agents into the fi nal manufacturing activity and the gas processing As the nitrogen A S Foelster et al Journal of Cleaner Production 129 2016 30e4233 compressor does not produce a measurable mass fl ow its energy consumption is assigned to mechanical separation and pelletising in the LCA model The measurement of the diluted acid production output was not possible and was therefore calculated assuming stoichiometric reactions as mentioned in chapter 2 2 Eqs 1 e 6 of the refrigerant and blowing agents measured as input to the gas processing 3 3 2 Data acquisition for auxiliary material expenditures and transport activities LPG is the only signifi cant auxiliary material employed as combustion gas both in the forklift truck and in the gas treatment reactor 2014 average consumption was 55 g per refrigerator for the forklift truck and 220 g per refrigerator for heating the gas cracking reactor Ind stria Fox uses its ownEURO5 vehicle fl eet with heavy trucks for long distance transportation and small trucks for the refriger ator collection from households Transportation is modelled with the currentecoinvent freight transport datasets transport freight lorry size metric ton EURO5 RoW According to Spielmann and Scholz 2004 the dataset refers to a unit process including vehicle manufacturing maintenance operation and disposal as well as road construction operation and disposal The lorry size is chosen according to the gross tonne vehicle weight GVW of the employed lorries For quantifi cation of the transport service expressed in tkm the average distance per lorry was multiplied with the total mass of thousand refrigerators as reference fl ow The average distance per lorry has been calculated for a scenario that includes three main metropolitan areas S ao Paulo Rio de Janeiro and Curitiba amounting to almost 20 of Brazil s total population and taking into account historical company data of total cargo and average load Table 2 3 3 3 External data collection The plastic fraction from the manual and mechanical treatment is further processed before reuse The main compressor recycling company has been visited and enquiries were directed to the main plastic recyclers The compressor recycling takes place in a small factory in S ao Paulo approx 90 km from Ind stria Fox s plant The disassembly is done mainly manually with 20 t of compressor input resulting in 2 t of copper and 18 t of iron consuming 1300 kWh of electricity Plastic pieces are transported on average over 62 km to be cleaned and ground before re utilization With an electricity consumption of up to 12 kWh ton 79 wt ground polystyrene 13 wt other recyclable plastics and metals and 8 wt waste are produced Plastic from mechanical treatment is of inferior quality A sorting analysis of 3 kg randomly drawn material revealed that 14 wt are waste fractions mainly polyurethane foam The plastic manufac turer is assumed to use a swim sink process with an energy con sumption of 1 82 kW h per 1 5 t of plastic processed The grinding process is assumed to be the same used for the plastic pieces As cleaning has already taken place the waste content is not considered Waste fl ows white glass wool ceramics fi ne particles and the magnets of the sealing gasket plastic treatment waste are transported and disposed of on a sanitary landfi ll For this a conservative assumption has been made with a distance of 85 km Ind stria Fox e Landfi ll Paul nia and a medium lorry size of 7 5e16 t The model treats glass wool ceramics and magnets as inert waste and fi ne particles including litter as mixed plastic waste The transport service TS for the model is calculated with the following equation Phase 1 Manual preparation and degassing Phase 2 Mechanical processing Phase 3 Transformation of gases and scrubbing system boundary of the LCA ferrous metals PU foam aluminium copper polystyrene other plastics Blowing agents hydrochloric acid hydrofluoric acid cooling agents refrigerator casings waste refrigerators cables copper pipes door sealings iron gratings glass plates plastic parts compressors glass wool if applicable steel copper aluminium plastics glass recycling re use steel copper aluminium plastics recycling neutralisation plant energy sources raw and auxiliary materials emissions waste Fig 1 System boundaries of the LCA Table 2 Transport service for collecting 1000 refrigerators 52 82 t in S ao Paulo Rio de Janeiro and Curitiba TransportInd stria Fox data southeast scenarioTransport model assumptions Distance km GVW t Load t Transport tkm Lorry size t Long distance24521 64 725895 416e32 Collection154 40 71585 43 5e7 5 A S Foelster et al Journal of Cleaner Production 129 2016 30e4234 TS tkm distance km 2 weight of transported mass t 8 even including the return of the lorry 3 4 Life cycle inventory analysis The Life Cycle Inventory Analysis contains the activity specifi cations necessary for the refrigerator recycling including external downstream and upstream activities Furthermore a system for avoided burden credits and substitution of primary material is defi ned 3 4 1 Recycling system Results of the two conducted tests and data acquisitions are listed in Table 3 The column source shows whether the data was obtained from measurement 2014 average data or calculation stoichiometric reaction mass or energy balance Products inter mediate products raw material or auxiliary materials are classifi ed accordingly as Material Type Good G Cut offs e materials not contributing to the life cycle inventory e are classifi ed as Neutral N Bad B materials are those causing direct or indirect emis sions These emissions are allocated by mass criteria to all materials with the material type Good G This classifi cation goes back to Dyckhoff 1994 All neutral cut off materials sum up to 5 1 wt of input weight including 2 2 wt of material losses and measuring errors 3 4 2 Equivalence system Since the function of the equivalence system is to dispose of 1000 refrigerators and the provision of primary material according to the substituted mass conventional refrigerator disposal and the function of the signifi cant product fl ows are analysed in the following No data is available on the disposal of waste re frigerators Onlya minimum of refrigerators are recycled in a state of the art plant with caption of the cooling and blowing agents R12 R134a R11 R141b Therefore the measured gases in the gas processing are modelled to be emitted into the atmosphere by the avoided burden system see Table 4 Other elementary fl ows are not considered because it is not known whether materials end up on landfi lls waste dumps or at local recyclers informal or formal In order to compare the recycling process with a system of primary production the use of each secondary product has to be defi ned as a set of functional subunits which together with the disposal of 1000 refrigerators form the functional unit Therefore the destination of each material was traced and according to destination and quality aspects the substituted product and its substitution factor is determined The substitution factor describes the ratio of the primary product mass towards the recycled product mass given that both fulfi l the same function Table 5 presents results and respective functional units Ferrous scrap is used for crude steel production In the recycling system it is obtained in form of ferrous grids manual disassembly shredded scrap and compressor shapes 73 3 of Brazilian crude steel production is based on the blast furnace process World Steel Association 2014 Here ferrous scrap can optimize the process or completely substitute pig iron Martens 2011 As scrap impurities are inferior to those present in pig iron the conservative substi tution factor is 1 In lack of Brazilian data the complementary system simulates the pig iron production based on the ecoinvent global average dataset pig iron production GLO Brazilian steel production differs from the international steel industry in its main reduction material which is charcoal as opposed to coal Ugaya and Walter 2004 Charcoal is produced from native forests and forest plantations using a technique lagging greatly behind state of the art Nogueira et al 2009 Aluminium scrap has been analysed by an external laboratory With 0 5 wt of other materials and 99 5 wt aluminium alloy with an aluminium content of cal 97 9 wt the material is appropriate for the aluminium alloying industry Complete sub stitution of primary aluminium is not possible due to quality standards Paraskevas et al 2015 but the low level of recycling ABAL 2015 BGR 2013 justifi es a conservative substitution factor of 0 97 kg primary aluminium per kg aluminium scrap which is given in the ecoinvent dataset of Latin American production Relevant standards demand 99 9 wt Cu content in tubes for refrigeration and air conditioning BSI 2010 Manually sorted refrigerator copper scrap is nearly without impurities Copper ob tained from compressor recycling does not differ in its quality High quality copper can be directly employed for alloying and therefore substitutes copper cathodes which have a similar copper content Most plastic from refrigerators is high impact polystyrene HiPS Quality of recycled polystyrene differs from primary mate rial as physical properties worsen during the use phase and thermal stress during the recycling process shortens polymer chains Tarverdi 2010 However the visited extrusionprocess allows for a mix of up to 40 wt ground secondary polystyrene with 60 wt virgin material This produces a material comparable to general purpose polystyrene with inferior quality requirements resulting in a substitution factor of 1 The polyurethane pellets substitute charcoal in cement kilns as they represent a refuse derived fuel RDF A growing share of energy demand in the cement industry is covered by petroleum coke and RDF while petroleum oil charcoal and coal are dimin ishing EPE and MME 2014 To determine the substitution factor the lower calorifi c value of charcoal with 28 0e30 1 MJ kg Brandt 1999 is compared to the results of two external laboratory ana lyses on the calorifi c value of the pellets 26 2 MJ kg With these values the substitution factor is determined to S mcharcoal mpellet 26 2 MJ 28 0 MJ 0 94 Recycled glass wool is used for insulation in the construction sector The thermal conductivity of glass wool in the refrigerators is appreciated as quality aspect According to Schneider and Albert 2014 glass wool has a thermal conductivity between 0 039 and 0 05 W mK To account for ageing effects such as structure modi fi cations and broken fi bres the higher conductivity value is assumed for the recycled glass wool The reference material in the ecoinvent dataset of the equivalence system has a thermal con ductivity of 0 045 W mK In order to achieve the same insulation properties a recycled glass wool layerhas to be 11 t