THE HITCH HIKER’S GUIDE TO LCA
HENRIKKE BAUMANN
ANNE-MARIE TILLMAN
1 LCA IN A NUTSHELL
In LCA, a product is followed from its cradle to its grave. Natural resource use and pollutant emission are described in quantative terms. The procedure for how LCA studies are done and interpreted is:
• Goal and scope definition
• Inventory analysis
• Impact assessment
There are a series of standards for LCA, ISO 14040-14043.
2 DEVELOPMENT OF THE LCA CONCEPT
Before LCA was known as LCA, it was known under many names, for example:
• Ecobalances
• Resource and environmental profile analysis (REPA)
• Integral environmental analysis
• Environmental profiles
In 1991, it was decided to name the concept Life Cycle Assessment. In 1997, ISO 14040 was issued.
3 GOAL AND SCOPE DEFINITION
The goal and scope definition is a crucial phase of LCA studies, since different purposes require different methodology. The goal and scope definition is a play between at least two actors, the commissioner and the practitioner. Important aspects when deciding on scope are:
• Which options to model?
• Functional unit
• Choice of impact categories and method of impact assessment
• Type of LCA (accounting or change-oriented)
• System boundaries
• Cut-off criteria
4 INVENTORY ANALYSIS
Activities of the life cycle inventory analysis (LCI) include:
1. Construction of the flowchart according to the system boundaries decided on in the goal and scope definition.
2. Data collection for all the activities in the product system followed by documentation of collected data
3. Calculation of the environmental loads of the system in relation to the functional unit.
Allocation is a big issue in LCA, and one that is still being discussed and researched upon. The first thing to do when dealing with allocation is to choose between increasing the level of detail, or to expand the system.
One of the most debated issues with LCA is how to deal with allocation in open loop recycling.
5 LIFE CYCLE IMPACT ASSESSMENT
The impact assessment is achieved by “translating” the environmental loads from the inventory results into environmental impacts, such as acidification, ozone depletion, effect on biodiversity etc.
The general categories of environmental impacts are resource use, human health and ecological consequences. The complex web of cause-effect chains of environmental impacts causes problems with these categories though.
The phase of LCIA include:
• Impact category definition
• Classification
• Characterisation
• Normalisation
• Grouping
• Weighting
• Data quality analysis
There are a number of ready-made LCIA methods, for example:
• Ecoindicator’99
• EPS
• Environmental themes
• EDIP
6 INTERPRETATION AND PRESENTATION OF RESULTS
The process of assessing results in order to draw conclusions is called interpretation. The use of different types of diagrams is very helpful in this process.
The following tests can be uses to test the robustness for the study:
• Completeness check
• Conistency check
• Uncertainty check
• Sensitivity analysis
• Variation analysis
• Data quality analysis
7 CRITICAL REVIEW OF LCA
In the early 1990s, there was a suspicion that LCAs sometimes just showed what the commissioner of the study wanted it to show. Credibility is thus one of the reasons for critical review.
There are today two main types of reviews, the full ISO review and the review of EPDs.
8 LCA DATA MANAGEMENT
There are at least 24 available software packages on the market. There is a ISO standard for the LCA documentation format, ISO/TS 14048. The packages can be divided into three categories:
• Screening LCA (simple LCA for product development for example)
• Accounting LCA
• Fullblown LCA
9 LCA AND PRODUCT DEVELOPMENT
Two challenges characteristic of product development are time pressure and trade-offs between competing issues.
Environmental considerations should start influencing the product development process as early as possible, otherwise only small changes to the product design is possible.
Several simplified LCA methods exist, for example the MET matrix. LC-DSM matrix
There are specialized software packages that allow for “quick-and-dirty” LCAs.
Sometimes, “ordinary” LCA is necessary.
LCA-derived rules-of-thumb and proxies can be efficient in the product development process. For example, the LCA experience that a cars biggest environmental impact is its use gives the rule of thumb that weight is an important factor to work with.
10 GREEN MARKETING AND LCA
If green marketing is “too successful”, it could lead to an increase in total consumption volumes.
The connections between green marketing and LCA are:
• A company can communicate that it performs LCAs, to increase its overall environmental credibility.
• LCAs can be used to set the criteria for eco-labelling.
• LCAs, together with other environmental information, is used in Environmental Products Declarations, EPDs. EPDs are mainly uses in b2b situations.
11 LCA FOR PRODUCTION PROCESSES
Environmental concerns often conflict with other concerns in the production process, e.g. cost and performance. Thus, it can be useful to use optimisation methods to find the best solution. There are software packages available for this.
LCAs are often used to find the hot spots of the production processes.
Manufacturers of complex products such as cars and electronics have relatively little direct control of the emissions from production. Similarly to LCA, the supply chain concept grew out of the recognition that improvement of the individual supply chain stages did not lead to improvement of the chain as a hole.
There is little experience of making environmental assessments of supply chains.
Purchasers are in a strategic position to reduce environmental impact. Purchasers are often unclear about what they should base their environmental purchasing decision on.
Transportation has a small portion of the environmental impact of a product, with exceptions for for example clothes and bananas.
12 LCA AND WASTE MANAGEMENT
There are two ways waste management may be studied in LCA. In one approach the waste management system is the foreground system. Studies of this type are used to support planning of waste management. Waste management may also be a background system in LCAs that are focused on some other issue. For those types of study, generic data are needed.
Open loop recycling problems are handled with system expansion for the first type of study.
13 ORGANISING LCA ACTIVITIES IN A COMPANY
This chapter presents four cases of LCA use in industry.
Although the LCA concept is spreading, LCA work has not yet become routine procedure in industry. Companies tend to experiment, testing LCA on new products and new fields of application. This means that LCA projects often lead to learning and even surprising insights, perhaps also disappointment. In many companies, one may find an LCA entrepreneur, i.e. someone who actively and enthusiastically promotes LCA, and who is important for the process of implementing LCA.
Showing posts with label LCA. Show all posts
Showing posts with label LCA. Show all posts
Energy Use Life Cycle Assessment for Global Cotton Production Practices
Energy Use Life Cycle Assessment for Global Cotton Production Practices
Prepared for:
Cotton Incorporated
World Headquarters
6399 Weston Parkway
Cary, North Carolina 27513
Prepared by:
Marty Matlock, Ph.D., P.E., C.S.E.
Greg Thoma, Ph.D., P.E.
Darin Nutter, Ph.D., P.E.
Thomas Costello, Ph.D., P.E.
Center for Agricultural and Rural Sustainability
University of Arkansas Division of Agriculture
233 Engineering Hall
Fayetteville, AR 72701
March 15, 2008
Energy Use Life Cycle Assessment for Global Cotton Production Practices
Executive Summary
The goal of this project was to use Life Cycle Assessment (LCA) to quantify the energy required for cotton production over a range of global cotton production practices. Energy use is only one measurement of agricultural sustainability, but represents a method for unifying measurements of a variety of other inputs into agricultural production. The Center for Agricultural and Rural Sustainability at the University of Arkansas developed a model of energy usage by identifying a range of production practices across the globe and using these practices as parameters for the model. The LCA quantified various forms of energy inputs including direct mechanical, animal, and human energy required to produce a unit of raw cotton (expressed as a tonne or 1000 kg). The LCA also quantified energy embodied in the fertilizer, mechanical components and manure. The production of secondary products (seed, oil, etc.) was analyzed to quantify potential recoverable energy. The model quantifies energy used to perform various cotton production tasks including field preparation, planting, field operations and harvesting.
The average embodied energy of production of a tonne of cotton from the ten regions of the world ranges from 5,600 MJ/tonne (North America East) to 48,000 MJ/tonne (South America Non-Mechanized). The LCA of energy associated with use of manure as fertilizers in cotton production clearly demonstrated the large quantity of energy embodied in manure. Quantifying this opportunity cost (where manure energy can be practically utilized, e.g., using manure as a fuel for heating or cooking), increases the expressed embodied energy of cotton production of those systems almost tenfold. The LCA of net energy costs of production, measured as embodied energy minus potentially recovered energy (cottonseed oil and meal), showed that six of the ten regional production scenarios have the potential to be net energy-producing systems. The most sensitive variables for net energy production for cotton were yield and irrigation.
Prepared for:
Cotton Incorporated
World Headquarters
6399 Weston Parkway
Cary, North Carolina 27513
Prepared by:
Marty Matlock, Ph.D., P.E., C.S.E.
Greg Thoma, Ph.D., P.E.
Darin Nutter, Ph.D., P.E.
Thomas Costello, Ph.D., P.E.
Center for Agricultural and Rural Sustainability
University of Arkansas Division of Agriculture
233 Engineering Hall
Fayetteville, AR 72701
March 15, 2008
Energy Use Life Cycle Assessment for Global Cotton Production Practices
Executive Summary
The goal of this project was to use Life Cycle Assessment (LCA) to quantify the energy required for cotton production over a range of global cotton production practices. Energy use is only one measurement of agricultural sustainability, but represents a method for unifying measurements of a variety of other inputs into agricultural production. The Center for Agricultural and Rural Sustainability at the University of Arkansas developed a model of energy usage by identifying a range of production practices across the globe and using these practices as parameters for the model. The LCA quantified various forms of energy inputs including direct mechanical, animal, and human energy required to produce a unit of raw cotton (expressed as a tonne or 1000 kg). The LCA also quantified energy embodied in the fertilizer, mechanical components and manure. The production of secondary products (seed, oil, etc.) was analyzed to quantify potential recoverable energy. The model quantifies energy used to perform various cotton production tasks including field preparation, planting, field operations and harvesting.
The average embodied energy of production of a tonne of cotton from the ten regions of the world ranges from 5,600 MJ/tonne (North America East) to 48,000 MJ/tonne (South America Non-Mechanized). The LCA of energy associated with use of manure as fertilizers in cotton production clearly demonstrated the large quantity of energy embodied in manure. Quantifying this opportunity cost (where manure energy can be practically utilized, e.g., using manure as a fuel for heating or cooking), increases the expressed embodied energy of cotton production of those systems almost tenfold. The LCA of net energy costs of production, measured as embodied energy minus potentially recovered energy (cottonseed oil and meal), showed that six of the ten regional production scenarios have the potential to be net energy-producing systems. The most sensitive variables for net energy production for cotton were yield and irrigation.
Life Cycle Analysis (LCA)
Discuss the environmental life cycle approach to assessing cars. Your answer should contain:
a. A definition and brief explanation of what you mean by life cycle analysis (LCA).
b. The aim of an LCA.
c. Environmental impacts of a car throughout its life cycle? Illustrate your answer with a sketch to show how these impacts can be categorized in an LCA.
d. A conclusion which draws on the above analysis to justify your opinion of the merit of an LCA.
The life cycle analysis (LCA), a technique to pull together environmental indicators. Life cycle analysis is a system approach in that it traces environmental impacts at all stages of a product’s life cycle. It starts from the impacts arising from extracting and processing raw materials; then it identifies impacts from manufacturing and delivering a product, followed by the impacts involved in using a product, and finally examines what happens at the end of the product’s life-whether it is reused, the material from it is recycled or, if it is dumped, the environmental impacts concerned. An LCA is particularly useful if it is not immediately clear which are the major environmental impacts or at which stage of the life cycle the impacts occur.
The aim of LCA is to identify where the greatest environmental impacts occur in order to help decide the best approach to reduce them. Often a comparative LCA is undertaken on two design options: for example, the use of an electric vehicle to replace one powered by a conventional petrol engine. An electrical engine will result in no emissions at point of use, but the electricity has to be generated somehow, and so power station emissions associated with the energy used by such a vehicle need to be taken into account. An LCA can help to improve the design not only of a product (e.g. a car or train) but also of a service or a system. An example of the latter would be, if instead of traveling to a shop, you ordered shopping by the internet and it was delivered in a van servicing several households.
Student should sketch Figure 3.1 & 3.2 to show how these can be categorized in an LCA. The main materials used in the manufacture of cars are steel, non-ferrous metals (such as aluminum and copper), plastics and glass. Extracting and processing these materials involves a large amount of energy and water, the production of various emissions to air and water and the creation of a lot of solid waste. During manufacture and assembly of the car, further energy, water and other inputs are required and further emissions and solid wastes are produced.
After sale to the purchaser and during its useful life, the car will consume large amounts of petrol or diesel fuel which produces emissions, such as carbon dioxide (CO2), and air pollutants including carbon monoxide, un-burnt hydrocarbons and nitrogen oxides, which are harmful to human health and/or the environment. During its life, the car will also require the replacement and disposal of many parts and components, particularly tyres, batteries and exhaust systems. At the end of its life cycle the car will normally be broken up and many of its materials will be recycled. This may reduce energy consumption and emissions compared with sourcing virgin materials. Finally, non-recycled materials (glass, rubber and fabrics) are buried as solid waste or may be burnt, producing further emissions.
In practice, a full LCA is a complex and expensive process and the results are not always clear cut. A particular problem is deciding the relative importance of different environmental impacts. For example, a number of packaging LCAs have identified a dilemma: plastic packaging, made form oil, has one set of environmental impacts, including depletion of a non-renewable resource and emissions in manufacture, while cardboard packaging tends to involve water pollution issues. Which of the two is the more important? Simply conducting an LCA will not answer this question.
An LCA systematically creates a list (or 'inventory') of environmental impacts, but comparing these impacts or deciding what to do once this information is gathered can be tricky. Consequently, in practice, LCAs are used more often to identify the main environmental impacts and at which stage in the life cycle these occur. LCAs are particularly helpful in systematically identifying environmental 'hot spots' and clarifying the decisions that need to be made. In many cases it is obvious where the largest effects are and more detailed studies can concentrate on where the situation is unclear. The LCA also illustrates that point about trade-off between environmental issues
a. A definition and brief explanation of what you mean by life cycle analysis (LCA).
b. The aim of an LCA.
c. Environmental impacts of a car throughout its life cycle? Illustrate your answer with a sketch to show how these impacts can be categorized in an LCA.
d. A conclusion which draws on the above analysis to justify your opinion of the merit of an LCA.
The life cycle analysis (LCA), a technique to pull together environmental indicators. Life cycle analysis is a system approach in that it traces environmental impacts at all stages of a product’s life cycle. It starts from the impacts arising from extracting and processing raw materials; then it identifies impacts from manufacturing and delivering a product, followed by the impacts involved in using a product, and finally examines what happens at the end of the product’s life-whether it is reused, the material from it is recycled or, if it is dumped, the environmental impacts concerned. An LCA is particularly useful if it is not immediately clear which are the major environmental impacts or at which stage of the life cycle the impacts occur.
The aim of LCA is to identify where the greatest environmental impacts occur in order to help decide the best approach to reduce them. Often a comparative LCA is undertaken on two design options: for example, the use of an electric vehicle to replace one powered by a conventional petrol engine. An electrical engine will result in no emissions at point of use, but the electricity has to be generated somehow, and so power station emissions associated with the energy used by such a vehicle need to be taken into account. An LCA can help to improve the design not only of a product (e.g. a car or train) but also of a service or a system. An example of the latter would be, if instead of traveling to a shop, you ordered shopping by the internet and it was delivered in a van servicing several households.
Student should sketch Figure 3.1 & 3.2 to show how these can be categorized in an LCA. The main materials used in the manufacture of cars are steel, non-ferrous metals (such as aluminum and copper), plastics and glass. Extracting and processing these materials involves a large amount of energy and water, the production of various emissions to air and water and the creation of a lot of solid waste. During manufacture and assembly of the car, further energy, water and other inputs are required and further emissions and solid wastes are produced.
After sale to the purchaser and during its useful life, the car will consume large amounts of petrol or diesel fuel which produces emissions, such as carbon dioxide (CO2), and air pollutants including carbon monoxide, un-burnt hydrocarbons and nitrogen oxides, which are harmful to human health and/or the environment. During its life, the car will also require the replacement and disposal of many parts and components, particularly tyres, batteries and exhaust systems. At the end of its life cycle the car will normally be broken up and many of its materials will be recycled. This may reduce energy consumption and emissions compared with sourcing virgin materials. Finally, non-recycled materials (glass, rubber and fabrics) are buried as solid waste or may be burnt, producing further emissions.
In practice, a full LCA is a complex and expensive process and the results are not always clear cut. A particular problem is deciding the relative importance of different environmental impacts. For example, a number of packaging LCAs have identified a dilemma: plastic packaging, made form oil, has one set of environmental impacts, including depletion of a non-renewable resource and emissions in manufacture, while cardboard packaging tends to involve water pollution issues. Which of the two is the more important? Simply conducting an LCA will not answer this question.
An LCA systematically creates a list (or 'inventory') of environmental impacts, but comparing these impacts or deciding what to do once this information is gathered can be tricky. Consequently, in practice, LCAs are used more often to identify the main environmental impacts and at which stage in the life cycle these occur. LCAs are particularly helpful in systematically identifying environmental 'hot spots' and clarifying the decisions that need to be made. In many cases it is obvious where the largest effects are and more detailed studies can concentrate on where the situation is unclear. The LCA also illustrates that point about trade-off between environmental issues
Life Cycle Analysis ( LCA ) Industri Pengecoran Logam (Aluminium)
Konsep analisis siklus hidup adalah salah satu alternative baru dari industri, masyarakat umum, dan pemerintah yang timbul sebagai respon terhadap kesadaran lingkungan.
Komponen utama LCA dapat dibagi menjadi empat bagian, yaitu:
Tujuan dan cakupan (Goal and Scoping)
Tujuan dari industri pengecoran logam dengan metode High Pressure Die Casting adalah menghasilkan produk coran dengan kualitas yang lebih baik yaitu diukur dari akurasi dan kompleksitas dari produk dibandingkan coran dengan cetakan pasir. Kelebihan dari metode pengecoran logam dengan metode High Pressure Die Casting antara lain :
Ketelitian dan kecermatan yang tinggi
Lebih fleksibel dalam desain
Menghasilkan permukaan yang halus
Dapat menghasilkan coran yang tipis
Lebih ekonomis dari pada benda kerja yang dibuat khusus dengan machining
Cakupan dari kegiatan produksi industri pengecoran logam dengan metode High Pressure Die Casting antara lain :
Penyediaan bahan baku
Bahan baku yang digunakan adalah alumunium bekas velg mobil sehingga bahan baku dapat diperoleh dari bengkel-bengkel mobil. Setelah dilakukan penelitian komposisi alumunium tersebut termasuk alumunium paduan. Bahan yang digunakan (Al-Si 7,79) berdasarkan pengklasifikasian, termasuk paduan Alumunium Die Casting (ADC 10 ). Paduan ini memiliki sifat mekanis yang sangat baik, Mudah dimachining dan mudah dicor dengan cetakan permanen. Dampak yang ditimbulkan pada proses ini adalah polusi suara dan debu, karena velg bekas mobil perlu dipecah menjadi bagian yang kecil-kecil sehingga lebih mudah untuk dilebur. Pada saat proses pemecahan velg mobil debu dan suara akan menyebar ke daerah sekitar sehingga pekerja perlu menggunakan masker dan perlu dipikirkan lokasi industri agar tidak terlalu dekat dengan pemukiman.
Proses Peleburan dan Pengecoran
Pada proses peleburan bahan baku diperlukan energi panas yang cukup besar untuk melebur alumunium. Peleburan alumunium ini dapat menggunakan bahan bakar solar, minyak tanah, gas LPG, arang maupun kayu. Masing-masing bahan bakar perlu dikaji kelebihan dan kekurangannya. Pada penelitian ini bahan bakar yang digunakan adalah gas LPG dengan pertimbangan bahan tersebut lebih bersih. Dampak yang ditimbulkan pada proses ini adalah pencemaran udara karena asap dari pembakaran alumunium dapat mengganggu lingkungan sekitar.
Mesin die casting ini adalah mesin yang digunakan untuk proses pengecoran logam dengan cara memasukkan logam cair kedalam cetakan logam dengan menggunakan tekanan. Dapat digunakan untuk material seperti aluminium, magnesium dan tembaga.
Cara kerjanya diawali dengan peleburan cairan logam menggunakan tungku terpisah dari mesin die casting kemudian dituang kedalam mesin die casting menggunakan ladel melalui tabung injeksi (shot sleeve) yang tidak dipanaskan, setelah cairan logam tersebut berada pada tabung injeksi, ditekan dengan plunyer tenaga hidrolik kedalam rongga cetakan (die cavity), tekanan injeksi ini dijaga selama proses solidifikasi. Setelah coran membeku, die dibuka dan benda coran akan keluar secara otomatis melalui mekanisme ejektor.
Salah satu upaya yang dapat dilakukan untuk mengurangi pencemaran udara tersebut adalah dengan membuat cerobong asap yang tinggi dilengkapi dengan penangkap debu ( dust collector ). Alat ini bisa menyaring dan menangkap debu atau asap yang dihasilkan dari proses pengecoran. Limbah debu dan asap yang ditangkap oleh alat ini bisa diolah dan dimanfaatkan menjadi campuran pembuat refraktori Alumina ( batu tahan api )
Proses finishing produk
Proses finishing dilakukan setelah pelepasan produk dari cetakan. Produk yang sudah jadi kemudian difinshing dengan cara dikrom. Proses ini menghasilkan limbah cair yang cukup berbahaya, oleh karena itu harus diolah agar tidak mencemari lingkunan.
Untuk menanganinya, chromic acid harus dirubah menjadi ion chrom bervalensi tiga (trivalent chrom), yang tidak mudah larut dalam air. Untuk mereduksi chromic acid digunakan sodium metabisulfite. Chromic acid (Cr 6+) yang tadinya berwarna kuning akan berubah menjadi warna hijau (Cr 3+) dan dengan diberi soda api (Na OH) akan terbentuk chrome hidroksida yang tidak larut dalam air, sehingga dapat mudah dipisahkan dengan air.
Untuk mempercepat pemisahan digunakan larutan tawas sebagai koagulant.Untuk menambah waktu pengendapan dibutuhkan bak pengendapan dengan design seperti pada gambar di bawah ini.
Buat bak untuk instalasi limbah sesuai dengan kapasitas limbah chrom dan proses limbah tersebut dengan benar. Untuk mengurangi jumlah limbah sebaiknya dibuatkan sistem pembilasan yang baik, sehingga jumlah bahan kimia yang dibutuhkan untuk pengolahan limbah juga ikut berkurang. Harga bahan kimia untuk limbah seperti sodium metabisulfite, soda api, dan tawas, tidaklah mahal. Sehingga biaya proses jauh lebih kecil dibandingkan dengan biaya kerusakan lingkungan yang diakibatkan oleh limbah yang tidak diolah.
Proses pemasaran produk
Analisis inventori (Inventory Analysis)
Analisis inventori merupakan bagian LCA yang berisi inventori input yang berupa:
Energi
Industri pengecoran logam dengan mesin HPDC (High Pressure Die Casting) menggunakan energi listrik untuk menggerakkan motor dalam powerpack. Sedangkan untuk melebur Alumunium menggunakan energi panas dengan gas LPG
Bahan baku
Output emisi maupun limbah
Impact Assessment
Impact Assessment digunakan untuk menganalisis dampak suatu proses terhadap lingkungan dan kesehatan manusia yang telah didata secara kuantitatif pada penakaran inventori. Dalam pengklasifikasian data inventori yang dihubungkan dengan efek potensi terhadap ekologi dan kesehatan manusia ditempatkan dalam kategori-kategori khusus.
4. Analisis Dampak Sosial
Keberadaan industry pengecoran logam dapat menyerap tenaga kerja dari masyarakat sekitar. Secara umum keberadaan dan pengembangan usaha pengecoran logam memberikan dampak yang positif bagi wilayah yaitu dengan terbukanya peluang kerja serta peningkatan pendapatan masyarakat dan sekaligus peningkatan pendapatan daerah.
5. Analisis Dampak Lingkungan
Usaha pengecoran logam menimbulkan jelaga dan asap dari kupola, dan suara bising. Dampak ini memberikan pengaruh buruk pada kesehatan pekerja dan penduduk sekitar pabrik. Oleh karena itu perlu diambil tindakan-tindakan untuk meniadakan penyebab-penyebab pencemaran umum tersebut di atas. Peralatan yang paling sederhana untuk menghilangkan asap dan debu dari kapola adalah sebuah silinder dengan tutup berbentuk kerucut yang dipasang di atas kapola. Debu ini dialirkan kebidang miring dan jatuh ke dasar penangkap debu. Dalam industry pengecoran, suara dikeluarkan dari berbagai mesin. Kebisingan tersebut menyebabkan perasaan tidak enak bagi para pekerja dan orang-orang sekitar pabrik. Cara pencegahan dari kebisingan tersebut adalah dengan jalan menutup mesin-mesin yang menjadi sumber kebisingan atau menempatkan mesin-mesin tersebut di ruangan yang kedap suara tetapi hal ini pada prakteknya susah dilaksanakan. Kalau kebisingan yang terjadi sampai ketingkat tertentu kebisingan dapat ditahan dengan jalan membuat ruangan kedap suara, dengan member lapisan bahan peredam getaran pada dinding dan di atas langit-langit.
Improvement Analysis
Pada tahapan ini dilakukan interpretasi hasil, evaluasi, dan analisa terhadap usaha-usaha yang dapat dilakukan untuk perbaikan
Komponen utama LCA dapat dibagi menjadi empat bagian, yaitu:
Tujuan dan cakupan (Goal and Scoping)
Tujuan dari industri pengecoran logam dengan metode High Pressure Die Casting adalah menghasilkan produk coran dengan kualitas yang lebih baik yaitu diukur dari akurasi dan kompleksitas dari produk dibandingkan coran dengan cetakan pasir. Kelebihan dari metode pengecoran logam dengan metode High Pressure Die Casting antara lain :
Ketelitian dan kecermatan yang tinggi
Lebih fleksibel dalam desain
Menghasilkan permukaan yang halus
Dapat menghasilkan coran yang tipis
Lebih ekonomis dari pada benda kerja yang dibuat khusus dengan machining
Cakupan dari kegiatan produksi industri pengecoran logam dengan metode High Pressure Die Casting antara lain :
Penyediaan bahan baku
Bahan baku yang digunakan adalah alumunium bekas velg mobil sehingga bahan baku dapat diperoleh dari bengkel-bengkel mobil. Setelah dilakukan penelitian komposisi alumunium tersebut termasuk alumunium paduan. Bahan yang digunakan (Al-Si 7,79) berdasarkan pengklasifikasian, termasuk paduan Alumunium Die Casting (ADC 10 ). Paduan ini memiliki sifat mekanis yang sangat baik, Mudah dimachining dan mudah dicor dengan cetakan permanen. Dampak yang ditimbulkan pada proses ini adalah polusi suara dan debu, karena velg bekas mobil perlu dipecah menjadi bagian yang kecil-kecil sehingga lebih mudah untuk dilebur. Pada saat proses pemecahan velg mobil debu dan suara akan menyebar ke daerah sekitar sehingga pekerja perlu menggunakan masker dan perlu dipikirkan lokasi industri agar tidak terlalu dekat dengan pemukiman.
Proses Peleburan dan Pengecoran
Pada proses peleburan bahan baku diperlukan energi panas yang cukup besar untuk melebur alumunium. Peleburan alumunium ini dapat menggunakan bahan bakar solar, minyak tanah, gas LPG, arang maupun kayu. Masing-masing bahan bakar perlu dikaji kelebihan dan kekurangannya. Pada penelitian ini bahan bakar yang digunakan adalah gas LPG dengan pertimbangan bahan tersebut lebih bersih. Dampak yang ditimbulkan pada proses ini adalah pencemaran udara karena asap dari pembakaran alumunium dapat mengganggu lingkungan sekitar.
Mesin die casting ini adalah mesin yang digunakan untuk proses pengecoran logam dengan cara memasukkan logam cair kedalam cetakan logam dengan menggunakan tekanan. Dapat digunakan untuk material seperti aluminium, magnesium dan tembaga.
Cara kerjanya diawali dengan peleburan cairan logam menggunakan tungku terpisah dari mesin die casting kemudian dituang kedalam mesin die casting menggunakan ladel melalui tabung injeksi (shot sleeve) yang tidak dipanaskan, setelah cairan logam tersebut berada pada tabung injeksi, ditekan dengan plunyer tenaga hidrolik kedalam rongga cetakan (die cavity), tekanan injeksi ini dijaga selama proses solidifikasi. Setelah coran membeku, die dibuka dan benda coran akan keluar secara otomatis melalui mekanisme ejektor.
Salah satu upaya yang dapat dilakukan untuk mengurangi pencemaran udara tersebut adalah dengan membuat cerobong asap yang tinggi dilengkapi dengan penangkap debu ( dust collector ). Alat ini bisa menyaring dan menangkap debu atau asap yang dihasilkan dari proses pengecoran. Limbah debu dan asap yang ditangkap oleh alat ini bisa diolah dan dimanfaatkan menjadi campuran pembuat refraktori Alumina ( batu tahan api )
Proses finishing produk
Proses finishing dilakukan setelah pelepasan produk dari cetakan. Produk yang sudah jadi kemudian difinshing dengan cara dikrom. Proses ini menghasilkan limbah cair yang cukup berbahaya, oleh karena itu harus diolah agar tidak mencemari lingkunan.
Untuk menanganinya, chromic acid harus dirubah menjadi ion chrom bervalensi tiga (trivalent chrom), yang tidak mudah larut dalam air. Untuk mereduksi chromic acid digunakan sodium metabisulfite. Chromic acid (Cr 6+) yang tadinya berwarna kuning akan berubah menjadi warna hijau (Cr 3+) dan dengan diberi soda api (Na OH) akan terbentuk chrome hidroksida yang tidak larut dalam air, sehingga dapat mudah dipisahkan dengan air.
Untuk mempercepat pemisahan digunakan larutan tawas sebagai koagulant.Untuk menambah waktu pengendapan dibutuhkan bak pengendapan dengan design seperti pada gambar di bawah ini.
Buat bak untuk instalasi limbah sesuai dengan kapasitas limbah chrom dan proses limbah tersebut dengan benar. Untuk mengurangi jumlah limbah sebaiknya dibuatkan sistem pembilasan yang baik, sehingga jumlah bahan kimia yang dibutuhkan untuk pengolahan limbah juga ikut berkurang. Harga bahan kimia untuk limbah seperti sodium metabisulfite, soda api, dan tawas, tidaklah mahal. Sehingga biaya proses jauh lebih kecil dibandingkan dengan biaya kerusakan lingkungan yang diakibatkan oleh limbah yang tidak diolah.
Proses pemasaran produk
Analisis inventori (Inventory Analysis)
Analisis inventori merupakan bagian LCA yang berisi inventori input yang berupa:
Energi
Industri pengecoran logam dengan mesin HPDC (High Pressure Die Casting) menggunakan energi listrik untuk menggerakkan motor dalam powerpack. Sedangkan untuk melebur Alumunium menggunakan energi panas dengan gas LPG
Bahan baku
Output emisi maupun limbah
Impact Assessment
Impact Assessment digunakan untuk menganalisis dampak suatu proses terhadap lingkungan dan kesehatan manusia yang telah didata secara kuantitatif pada penakaran inventori. Dalam pengklasifikasian data inventori yang dihubungkan dengan efek potensi terhadap ekologi dan kesehatan manusia ditempatkan dalam kategori-kategori khusus.
4. Analisis Dampak Sosial
Keberadaan industry pengecoran logam dapat menyerap tenaga kerja dari masyarakat sekitar. Secara umum keberadaan dan pengembangan usaha pengecoran logam memberikan dampak yang positif bagi wilayah yaitu dengan terbukanya peluang kerja serta peningkatan pendapatan masyarakat dan sekaligus peningkatan pendapatan daerah.
5. Analisis Dampak Lingkungan
Usaha pengecoran logam menimbulkan jelaga dan asap dari kupola, dan suara bising. Dampak ini memberikan pengaruh buruk pada kesehatan pekerja dan penduduk sekitar pabrik. Oleh karena itu perlu diambil tindakan-tindakan untuk meniadakan penyebab-penyebab pencemaran umum tersebut di atas. Peralatan yang paling sederhana untuk menghilangkan asap dan debu dari kapola adalah sebuah silinder dengan tutup berbentuk kerucut yang dipasang di atas kapola. Debu ini dialirkan kebidang miring dan jatuh ke dasar penangkap debu. Dalam industry pengecoran, suara dikeluarkan dari berbagai mesin. Kebisingan tersebut menyebabkan perasaan tidak enak bagi para pekerja dan orang-orang sekitar pabrik. Cara pencegahan dari kebisingan tersebut adalah dengan jalan menutup mesin-mesin yang menjadi sumber kebisingan atau menempatkan mesin-mesin tersebut di ruangan yang kedap suara tetapi hal ini pada prakteknya susah dilaksanakan. Kalau kebisingan yang terjadi sampai ketingkat tertentu kebisingan dapat ditahan dengan jalan membuat ruangan kedap suara, dengan member lapisan bahan peredam getaran pada dinding dan di atas langit-langit.
Improvement Analysis
Pada tahapan ini dilakukan interpretasi hasil, evaluasi, dan analisa terhadap usaha-usaha yang dapat dilakukan untuk perbaikan
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