ESE Environmental Engineering - Week 12 Waste Minimization PDF

TECHNOLOGICAL UNIVERSITY OF THE PHILIPPINES VISAYAS Capt. Sabi St., City of Talisay, Negros Occidental College of Automation and Control LEARNING MODULE Subject: (ENVIRONMENTAL ENGINEERING) (Week 12) COMPILED BY:...

TECHNOLOGICAL UNIVERSITY OF THE PHILIPPINES VISAYAS Capt. Sabi St., City of Talisay, Negros Occidental College of Automation and Control LEARNING MODULE Subject: (ENVIRONMENTAL ENGINEERING) (Week 12) COMPILED BY: ARON J. LEONORAS 2022  2 LEARNING GUIDE Week No.: 12 TOPIC: WASTE MINIMIZATION LEARNING OUTCOMES 1. Introduction to Waste Minimization 2. Life Cycle Assessment 3. Elements of Waste Minimization Strategy 4. Benefits of Waste Minimization 5. Elements of a Waste Minimization Program 6. Waste Reduction Techniques EXPECTED COMPETENCIES The students will be introduced to the concepts and importance of waste minimization, by focusing on its qualitative aspects and life cycle assessments from the conception of its products as raw materials to its disposal as wastes, with particular case study references to the chemical industry. Also, the strategy of waste minimization program will be discussed through reviewing the benefits and techniques of waste reduction, recycling, reuse, treatment and proper disposal, as well as its technical and economic evaluation and waste management. Introduction to Waste Minimization The limitations in the recuperative capacity of the ecosystem have been recognized since about 1960. The alleviation measures taken by industry to pollution were add-on installations (end-of-pipe treatments) and these succeeded in bringing about a relatively quick improvement. However, since the mid-1970s the limitations of these methods have also been recognized, and a waste minimization approach has been seen as the only sustainable means of dealing with the waste problem. Within any waste management system, the primary concern should be to reduce the quantities of waste material produced. This avoids the necessity to treat and dispose of such materials. Several reasons may be put forward in favor of waste minimization (Grujer, 1991). These are: 1. The generation of large volumes of waste correlates with the depletion of mostly non-renewable resources. 2. The energy requirement for the transformation and upgrading of wastes is in proportion to the quantities treated and rises exponentially with increasing dilution of the waste.  3 3. The increasing total costs for collection, segregation, intermediate storage, transport, treatment, and final storage make waste minimization economically attractive. 4. Increased public and legislative pressures seem likely to be mitigated only by waste reduction/minimization. 5. Since waste equals inefficiency, reducing waste increases efficiency and hence profitability. Many organizations, such as the International Chambers of Commerce and the Chemical Manufacturers Association, have endorsed the concepts of waste minimization and sustainability (Willums and Goluke, 1992; CMA, 1991). In many cases good operating practices, housekeeping, etc., can lead to a substantial reduction in industrial and other wastes. However, there is a need for innovation in the design and operation of plant and equipment, in order to fully achieve the waste prevention goals which are being and will be set. These innovations are the so-called clean technologies. Definition of Clean Technology In recent years the drive towards improved environmental performance has seen the emergence of a new approach to the solution of waste problems. This has variously been termed clean or cleaner technology, cleaner production, waste minimization, waste reduction, pollution prevention and so on. There are many definitions of ‘Clean Technology’. However, all incorporate the following same two ideas, namely: 1. The emphasis is on the generation of less waste and on the consumption of fewer raw materials and less energy. Thus, a simple but satisfactory definition of clean technology is ‘any technology or process which uses fewer raw materials and/or less energy, and/or generates less waste than an existing technology or process’. 2. The avoidance of ‘end-of-pipe’ emission reduction is also emphasized. End-of-pipe methods are those that attempt to reduce the environmental impact of a waste, after that waste has been produced. Although the concept of zero emission processes has been espoused, such a target is thermodynamically impossible for a manufacturing process, if such a process is regarded as an open system (a system that exchanges both material and energy with its surroundings). Manipulating the system boundary in an attempt to produce a closed system (one that exchanges only energy and not materials with its surroundings) is analogous to the end-of-pipe solution to material problems, which merely transfers matter from one medium to another. Enlarging the systems boundary to incorporate the energy supply facility reveals that the enlarged system is, in fact, open and depositing material into the surroundings (biosphere).  4 It should also be understood that traditional treatment methods merely alter the form of waste or transfer it from one medium to another. Thus, the total quantity of waste is not reduced. As a consequence of such an analysis, the following tenets arise: 1. There cannot be zero waste from any manufacturing process. 2. Once created, waste cannot be destroyed. It is important to note that there is no thermodynamic restriction regarding elimination of a particular waste, nor on the transformation of a waste material to a more innocuous one, provided that the conservation laws are observed. The only reasonable outcome from thermodynamic considerations is, therefore, that waste emissions from a manufacturing process can be minimized in terms of both quantity and toxicity, so that they fall within the assimilative capacity of the biosphere. This outcome leads to the principle of waste minimization, and ultimately provides the goal for setting environmental impact standards for manufacturing industry. Life Cycle Assessment (LCA) Before examining waste minimization techniques and strategies, let us first examine what is now called the life cycle assessment of a product. The objective of this section is to show that a systems approach is required when examining pollution sources in process operations. Initially the life cycle of the product or service should be assessed. This will indicate the relative contribution of the life cycle stages to environmental impact. Failure to do this may allow attention to be focused on a stage which is most topical but has least significance. For example, the usage of water, detergent, and electricity during the operation of washing machines is much more important than the emissions during their manufacture or disposal. The emissions during the manufacture of pharmaceuticals may be more significant than the emissions during their distribution or after their excretion from the body. The general structure of processing systems and their component operations are discussed. Likely emission sources are identified. Following this, the need for an integrated pollution prevention and control approach is emphasized. The reader is referred to the reading list for further information. This brief section can only serve as an introduction. Life cycle assessment is a developing environmental management technique which has been applied to a greater or lesser extent for two decades but has been the focus of intense interest since 1990. It is an attempt to attribute all the environmental impacts in the life cycle of a marketable product. It recognizes that raw materials production and eventual disposal may be as significant environmentally as the product manufacture. Another name, disliked by the purists, is a ‘cradle-to-grave’ study. The first reported life cycle assessment was carried out for Coca-Cola in 1969, on the choice of beverage containers. In the 1970s, energy supply systems were the main concern. This illustrates that the technique may also be applied to services and activities, not just artifacts. However, the then limits to the theory and available data meant interest waned. Through the 1980s, the increasing problem of limited landfill capacity drew attention to the  5 disposal problems associated with the ‘throw-away society’ in general and packaging in particular. Life cycle studies were awakened, and we have tangible consequences in the German and EU packaging restrictions. What is Life Cycle Assessment (LCA)? It may be formally defined as ‘a systematic inventory and comprehensive assessment of the environmental effects of two or more alternative activities involving a defined product in a defined space and time including all steps and co-products in its life cycles’ (Pedersen, 1993). Other terms used in Europe are ‘ecoprofile’, ‘ecobalance’ and ‘product life assessment’. If the assessment stage is omitted, we can use the term ‘life cycle analysis’. Any product may have the following stages in its cycle, as shown in Figure 1. ⚫ Raw materials acquisition ⚫ Bulk material processing ⚫ Engineered and specialty materials production ⚫ Manufacturing and assembly ⚫ Use and service ⚫ Retirement ⚫ Disposal Figure 1 Life cycle of a detergent product system The term ‘life cycle’ in this context is not the same as the business life cycle. Instead, the physical life is considered. Raw materials acquisition includes mining non-  6 renewable material, e.g. coal, and harvesting biomass, e.g. forestry. These bulk materials are processed into based materials by separation and purification, e.g. converting bauxite to aluminum. Some base materials are converted into engineered and specialty, e.g. ethylene polymerization to polyethylene pellets. An Outline of the Steps Necessary to Conduct a Life Cycle Assessment An LCA has the following phases: ⚫ Planning ⚫ Screening ⚫ Data Collection (inventory) ⚫ Data Treatment (aggregation/classification) ⚫ Evaluation Planning The planning phase is critical. At this stage, decisions are taken which determine the complexity of the study. They also determine the range of results and what may be gained from these results. Goal definition is important. One must determine who is going to use the results and for what purpose. Different users have different demands. An enterprise seeking to promote a product has a different outlook from a Government determining policy. If the results are to be applied to a particular region, e.g. Europe, it is important that the data used are relevant. For example, one should not presume an 80 % recycle rate of retired products, e.g. glass bottles, if the actual rate is 20 %. The time horizon is also important. Is one trying to satisfy current or anticipated legislative limits, or plan for longer term sustainable development? Screening Having identified the parameters of interest and the alternatives of concern, one must decide where and how to gather the significant data. At this stage, decisions should be taken to limit the study to consequential factors only, i.e. those that will distinguish one product from another. A preliminary LCA should be carried out after the plan has been formulated. This should be a coarse and simplified study. Its purpose is to validate the plan and correct errors before too much effort has been spent. This may provide enough information to satisfy the initial objectives (Lindfors, 1992). Data Collection This phase is often known as ‘inventory’. It may be defined as ‘an objective data-based process of quantifying energy and raw material requirements, air emissions, waterborne effluents, solid waste and other environmental releases throughout the life cycle of a product, process or activity’. Data may be collected from relevant literature studies, databases and reports (e.g. BUWAL, 1991). On-site measurements, records and personnel estimates may be available. Theoretical calculations and finally informed judgment may provide the necessary information. Data Treatment This is often described as ‘classification’ or ‘aggregation’. Quality control must be exercised on the data. Extensive data are available but dispersed. Allowance must be made for time and regional differences. Different sources must be compared and measured and reported values assessed against theoretical predictions. Data validity generally must be verified. Having now accumulated all the data and calculated their effects through the process tree, the many results must be aggregated to a smaller, manageable number. There is often a desire to reduce all the results to a single parameter, particularly financial. While useful, care must be taken that this is not simplistic.  7 Evaluation Finally, conclusions must be drawn from the exercise. A sensitivity analysis of the data will assess the significance of differences. This may also indicate that certain areas require even more consideration before a conclusion may be drawn. Impacts and improvements may be analyzed. Depending on the objectives, scope for process improvement will be identified or guidance provided in selecting alternative products or processes. Critique Life cycle assessment is a useful, through underdeveloped, environmental management tool. It must be recognized that LCA is a developing technique. Contradictory studies have been published on the same topic. This can easily arise through the application of inadequate, inconsistent, or inappropriate data. Different activities may be included or excluded from the cycle. The sheer scale of any problem necessitates simplification. This can distort the assessment. Selection of appropriate environmental performance indicators and criteria is difficult. At present, it is difficult to separate objective and subjective elements. Finally, as the methodology and available data are developed, it is worth revisiting previous life cycle assessments. As knowledge improves, it should be possible to place more confidence in our detailed assessments and also facilitate rapid, simpler, but nevertheless valid shortcut assessments. Elements of a Waste Minimization Strategy The Waste Management Hierarchy It is clearly seen from the foregoing that the prevention of waste generation is preferable to attempting to ‘clean up’ the waste after its production. Indeed, this concept leads directly to the hierarchy of preferred options, which is the hallmark of the waste minimization philosophy. The various elements of this hierarchy are explained below, together with some illustrative examples: Reduction at source As the name implies, the reduction or elimination of wastes at source, usually within a process, is an established waste minimization technique. It is the most effective means of waste minimization, and the one that should always be considered first. Source reduction measures include: ⚫ Process modifications ⚫ Feedstock purity improvements ⚫ Housekeeping and management practice changes ⚫ Increases in efficiency of equipment ⚫ Recycling within a process Improved purchasing procedures can prevent materials becoming waste by being out- of-date. Less packaging will result in reduced packaging waste. Altering reactor conditions to improve the yield reduces the quantities of by-products and unreacted starting materials which must be dealt with. Substitution by a more benign solvent  8 eliminates the potential for environmental release of a hazardous one. All of these examples will reduce or eliminate the quantities of waste being generated. Recycling/reuse This is the use or reuse of a waste as an effective substitute for a commercial product or as an ingredient or feedstock in an industrial process. It includes: ⚫ Reclamation of useful constituent fractions within a waste material ⚫ Removal of contaminants from waste to allow reuse The distinction between recycling and reuse is not always easy to make. Treatment Waste treatment incorporates any method, technique or process that changes the physical, chemical or biological character of a waste. The objective of waste treatment may be to accomplish one of the following: ⚫ Neutralize the waste ⚫ Recover energy or material resources from the waste ⚫ Render such waste - Non-hazardous - Less hazardous - Safer to manage - Amenable for recovery - Amenable for storage - Reduced in Volume Disposal Disposal is the discharge, deposit, injection, dumping, spilling, leaking or placing of waste into or on any land, or water or into the air. It is plain that concentration on the source reduction, recycle and reuse aspects of a waste problem will reduce the need for treatment and disposal. However, since there will always be some waste which is not amenable to the previous methods, an effective and environmentally safe means of ultimate disposal is necessary. Traditionally this has been the widespread use of landfill and incineration. However, with landfill sites becoming more scarce and increasingly stringent legislation governing both landfill and incineration, it is necessary to carefully manage such ultimate disposal facilities. Nevertheless, properly designed, controlled and managed landfill and incineration can result in low hazards. Benefits of Waste Minimization Companies often claim waste reduction credit for activities such as incineration that follow generation of a waste, rather than avoiding waste creation. Many companies use a definition of waste reduction that gives them credit for improved waste management and pollution control. Often the benefits of waste minimization are not seen. The apparent slowness in adopting methods which are clearly beneficial prompts the following questions:  9 1. Why do companies opt for end-of-pipe solutions, rather than clean technology? 2. Why should clean technologies be adopted? 3. What are the incentives and disincentives for adopting clean technologies? The answers to these questions are complex. Several possible answers suggest themselves. Why are Clean Technologies not Widely Used? In many cases the principles of waste minimization are poorly understood. The reduction of emissions to the atmosphere is seen as minimization. However, as has already been explained, waste once created cannot be destroyed. Thus, a reduction in emissions to atmosphere must necessarily lead to either an increase in emissions to land or water, or emissions of a different type to the atmosphere. While such emissions may be preferable to the original ones, their generation as a replacement cannot be regarded as waste minimization. In addition, companies are under legislative and public pressure to reduce waste. Hence, treatment systems that reduce the quantities of a certain type of waste emitted to a particular environment are claimed as waste reduction. Companies must invest in end-of-pipe technology to comply with emissions regulations. This diverts funding from waste reduction programs. Some disincentives to the adoption of clean technologies are listed below: ⚫ Lack of appreciation of economic benefits due to accounting systems that do not allocate total environmental costs of production profit centers ⚫ Competing production priorities ⚫ Belief that legally required pollution control is good enough ⚫ Incomplete data on exact sources and amounts of wastes ⚫ Difficulty of simultaneously spending resources on regulatory compliance and waste reduction Why Should Clean Technologies be Adopted? Enlightened Self-Interest Globally, many enterprises have seen that it is in their interest to minimize waste. The International Chamber of Commerce has prepared a Business Charter for Sustainable Development (Willums and Goluke, 1992). These 16 principles for environmental management are intended to assist enterprises in fulfilling their commitment to environmental stewardship in a comprehensive fashion. Principle 8 states: ‘Facilities and Operations: to develop, design and operate facilities and conduct activities taking into consideration the efficient use of energy and materials, the sustainable use of renewable resources, the minimization of adverse environmental impact and waste generation, and the safe and responsible disposal of residual wastes’. Companies such as Aer Lingus, 3M, Dow, IBM, Apple and DuPont have subscribed to these principles. Internationally, within the chemical process industry adherents include, Henkel, Johnson and Johnson, Pfizer, SmithKline Beecham and Syntex Corporation. In the United States, the Chemical Manufacturers Association, as part of its Responsible Care program, has produced a Pollution Prevention Code. Members ‘have  10 committed to the goal of minimizing wastes, reducing releases to the environment, and managing generated wastes in a manner that is environmentally acceptable and protects human health’. According to the Code: ‘the goal is to establish a long-term, substantial downward trend in the amount of wastes generated and contaminants and pollutants released’. In Europe, the organization PREPARE provides a network for countries with waste minimization programs. PREPARE is an initiative of the Dutch government, but now encompasses 14 countries. PREPARE organizes expert workshops in various industrial sectors, with a view to determining relevant clean technologies. The factors that prompt an enterprise to take waste minimization initiatives are many and complex, but it is worth examining three in particular: economics, legislation and community response. Economics Waste, by definition, equals inefficiency. Inefficiency costs money. Reducing waste must therefore present opportunities for improving profitability. It also eases the burden of regulatory compliance. Treatment and disposal costs are reduced and potential liabilities lessened. Product quality may also improve through better operation. It is interesting to examine the position of two companies to adopt clean technology. 3M describes its program as Pollution Prevention Pays (3Ps) and Dow calls its Waste Reduction Always Pays (WRAP). 3M claims to have saved about $300 million through eliminating wastes. Legislation The European Union has expressed its preference for waste minimization and some member countries, e.g. Denmark, with its cleaner technologies program, has been putting this into practice. The sharpest expression of this preference comes in the US Pollution Prevention Act of 1990. This policy has been actively promoted by the US Environmental Protection Agency and is seen as a landmark in US American environmental legislation. The rising costs of treatment and disposal, and the continued tightening of environmental legislation means that a reduction in the quantity of waste generated may offer the only viable and economic strategy. Community response Adoption of waste minimization programs is a way of demonstrating corporate and employee commitment to the environment and the community. Customer behavior may be guided by a company’s environmental performance. While this may be most immediate in affecting the producer of consumer goods for the public, the idea of audits on quality is a familiar one. Similar environmental audits will lead to the primary producers. Product life cycle assessment may currently be of concern for the manufacturer of car components or packaging but, as this technique develops, its extension to chemical products can be anticipated. Finally, it must be recognized that pressure groups are demanding that the waste problem be addressed. What are the Incentives for Adopting Clean Technologies? Some incentives to the adoption of clean technologies are listed below: ⚫ Often improved process economics ⚫ Reduced treatment costs ⚫ Reduced disposal costs ⚫ Reduced liability ⚫ Reduced risk of fines for breaches  11 ⚫ Increased public satisfaction Waste Minimization Options: ⚫ Increase conversion ⚫ Recover solvents ⚫ Reduce separation costs (increase separation efficiency) ⚫ Eliminate losses Elements of a Waste Minimization Program In accordance with the waste management hierarchy, all strategies aimed at waste minimization should follow the priority sequence. To ensure an optimum waste minimization program a wide-ranging strategy must be employed. This is, in many ways, similar to the safety strategy employed by many large companies such as DuPont. The basic parts of the waste minimization strategy may be summarized as follows: ⚫ Management involvement ⚫ Setting of goals ⚫ Selection of targets ⚫ Technical and economic evaluation ⚫ Implementation of programs ⚫ Follow-up assessment and monitoring Management Involvement It is essential that top management be committed to the idea of waste minimization if the program is to be successful. The management of a company will support a waste prevention program if it is convinced that the benefits of such program can reduce its costs and improve its environmental performance. The potential benefits have already been outlined. The potential costs include both the direct and indirect costs which ensue from the various investments. The management, once committed to the objective of waste minimization, should issue a policy statement, together with environmental guidelines. In addition, it is essential to involve the whole organization if the waste minimization program is to maximize its chances of success. Policy statement A formal environmental policy document or manual or guideline is the best way to communicate the objectives of a waste elimination program. This is akin to a safety statement and should emphasize the company’s commitment to clean technology. An example of such a policy statement by PREPARE might be (De Hoo, 1991): (A chemicals company)... Undertakes the obligation to supervise and channel protection of the environment. Environmental protection is one of the primary responsibilities of management as well as the responsibility of all personnel.  12 As we intended to adhere to this policy it is our aim, as a company, to limit the generation of waste materials and emissions and to ensure that, through practicing environmental management, the adverse effects on the air, the soil and water will be kept to a minimum. Environmental guidelines The environmental guidelines include: 1. Protection of the environment is a line responsibility and an important criterion for measuring the achievements of employees. Also, each employee carries just as much responsibility for environmental protection as he or she carries with regard to safety and other company objectives. 2. The prevention of waste and emissions is, and will continue to be, a major consideration in research, the development of production methods and the running of the company; the management sets this on a par with safety, profits and the prevention of damage. 3. Reuse of materials will be given preference above the incineration and disposal of waste. Communication: line organization Involvement of the entire company is essential if conflicts are to be resolved and obstacles are to be overcome. It is the employees that are the key to the program’s success through their direct involvement with production processes, installations, waste streams and emissions. The inventiveness of the personnel is essential in identifying opportunities for prevention. Bonuses, rewards and other forms of acknowledgment may be used to motivate employees. Achieving prevention goals may be used as a measure for assessing the performance of managers and workers. Setting of Goals Corporate level Apart from qualitative objectives such as those in the waste minimization policy statement, quantitative goals should be set. Examples of this are: ⚫ 35 % reduction in waste by 1992 when compared to 1982 values (DuPont). ⚫ 60 % waste reduction from 1990 to 1994 (Chevron) A simple statement like 5 % reduction per annum would be a realistic goal. Site-specific level These can be more specific than the corporate goals, e.g. ⚫ 20 % reduction in air emissions from 1988 to 1990 (Michigan Division of DOW, USA) Selection of Targets There are usually many opportunities for minimizing waste. Notwithstanding any corporate policies, it should be the responsibility of individual facilities to select targets and implement waste reduction. This may be carried out on a ‘freelance’ basis or it may be as part of a more structured company ethos. For example, the DOW Chemical Company requires each facility to develop an action plan to:  13 ⚫ Inventory all process losses to air, water and land ⚫ Identify sources, establish priorities, quantify losses and ratio to production ⚫ Evaluate environmental impact and risk ⚫ Set action priorities ⚫ Determine cost-effective actions ⚫ Set reduction goals ⚫ Determine resources necessary to accomplish goals ⚫ Track and communicate performance and plan for future reductions In any event it is necessary for each facility to select target areas for waste reduction. These should bear in mind the size and nature of the waste stream, as its source, the cost savings brought about by reduction, the technical feasibility of any solution, the required investment and the feasibility of monitoring the effects of the proposed initiative. To facilitate the selection of target areas or candidate projects a waste minimization audit or assessment is necessary. A waste minimization audit is not an environmental audit. Its purpose is not to measure compliance with regulations but to identify areas where waste reduction may be achieved. Several approaches to carrying out a waste minimization assessment have been documented. These differ in detail only and the general consensus is that a two-tier approach is most beneficial. The components are variously termed as follows: ⚫ Pre-assessment phase or first-tier investigations ⚫ Assessment phase or second-tier investigations First-tier investigations This phase is a screening operation which is used to identify the viable areas of priority for preventing waste. It is a means of obtaining an overall picture of the waste streams and company activities with limited means and within a short period. A pre-assessment can help substantially increase motivation in the company to launch a full-scale assessment. The steps in the pre-assessment phase may be as follows: 1. Establish a waste minimization assessment team. 2. Make an inventory of the waste streams and omissions generated on site. 3. Make an inventory of prevention opportunities and bottlenecks. Second-tier investigations This is a natural follow-on from the pre-assessment phase and involves further investigations on the prioritized options already identified. The assessment team may have to be strengthened, with additional personnel from affected areas of the plant becoming involved. The assessment procedure is similar, but more detailed than in pre-assessment. Process flow diagrams and material balances are useful, but more information is needed, and visits to plants together with interviewing plant personnel are seen as essential. The type of information to be gathered should include:  14 Design information ⚫ Process flow diagrams ⚫ Material application diagrams ⚫ Piping and instrumentation diagrams ⚫ Equipment lists, specifications, drawings, data sheets, operating and maintenance manuals ⚫ Plot plans, arrangement drawings and workflow diagrams Environmental information ⚫ Hazardous waste manifests ⚫ Emission inventories and waste assays ⚫ Biennial hazardous waste reports ⚫ Environmental (compliance) audit reports ⚫ Permits and permit applications ⚫ Spill/release prevention and countermeasure plans Raw material/production information ⚫ Composition sheets ⚫ Material safety data sheets ⚫ Batch sheets ⚫ Product and raw material inventory records ⚫ Production schedules ⚫ Operator data logs Economic information ⚫ Waste treatment and disposal costs ⚫ Product, utility and raw material costs ⚫ Operating and maintenance labor costs Other information ⚫ Company environmental policy statements ⚫ Company and department standard operating procedures ⚫ Organization charts For very small installations, the use of a two-tier approach may not be strictly necessary, since it may be possible to identify prospective projects quickly. Even in such cases, however, it is often advantageous to carry out a brief screening procedure. Technical and Economic Evaluation Technical Evaluation The final product of the assessment phase is a list of waste minimization options postulated for the assessed area. The assessment will have screened out the impractical or unattractive options. The next step is to determine whether the remaining options are technically and economically feasible.  15 The technical evaluation determines whether a proposed waste minimization option will work in a specific application. Typical technical evaluation criteria include the following (Hanlon and Fromm, 1990): 1. Is the system safe for workers? 2. Will product quality be maintained? 3. Is the new equipment, material or procedure compatible with production operating procedures, workflow and production rates? 4. Is additional labor required? 5. Are utilities available? Or must they be installed, thereby raising capital costs? 6. How long will production be stopped in order to install the system? 7. Is special expertise required to operate or maintain the new system? 8. Does the system create other environmental problems? 9. Does the vendor provide acceptable service? If, after the technical evaluation, the project appears unfeasible or impractical, it should be dropped. Economic evaluation All proposed projects in industry are subject to economic scrutiny. Waste minimization projects are no different and the usual decision criteria should be applied. However, it is now being increasingly recognized that knowledge about the true costs associated with generating hazardous waste is limited. The availability of such information would heighten the awareness of management to the need for different waste management programs and it would support many capital projects aimed at reducing waste. The four basic costs incurred when a company generates waste arise from: ⚫ Under-utilizing the value of the raw materials ⚫ General management costs associated with moving the waste around the site, storage, keeping track of waste records and shipping ⚫ Disposing of the waste ⚫ The associated costs with third-party liabilities if the waste is improperly disposed of Attempting to determine the true management costs associated with generating wastes at a particular company, either at a plant site or from a product line, will give managers the opportunity to truly realize waste management costs and waste minimization will become much more attractive.  16 Implementation of Programs Waste minimization options that involve operational, procedural or materials changes (without additions or modifications to equipment) should be implemented as soon as the potential cost savings have been determined. For projects involving equipment modifications or new equipment, the installation of a waste minimization project is essentially no different from any other physical plant improvement project. Follow-up Assessment and Monitoring A useful measure of the effectiveness of a waste minimization project is its payback. The project should pay for itself through reduced waste management costs and reduced raw material costs. In very many cases payback is two years or less. Thus, it can be expected that waste minimization projects increase profitability. However, it is also important to measure the actual reduction of waste brought about by the waste minimization project. The easiest way to measure waste reduction is by recording the quantities of waste generated before and after a waste minimization project has been implemented. Since waste production is normally a function of plant throughout it is important that waste measurements reflect this. Thus the quantity of a waste generated per unit product or per unit raw material used is felt to be an acceptable measure. Continuing the Policy A waste minimization program is not a once-off program, but rather an on-going one. After having implemented projects and reduced waste in priority areas, other, lower, priority areas should be assessed. The overall objective is to reduce waste generation to the greatest possible degree. It is important to realize that reduction of hazardous waste is only a first step. All industrial discharges should be reduced, since their generation implies inefficiency and lost profits. In many companies a safety or quality culture has been established. A waste minimization culture should similarly be developed. Thus, waste minimization must be an integral part of a company’s operations, and be on a par with safety, quality and production. Waste Reduction Techniques Previous topic outlined the ethos behind implementing a waste minimization policy. The question arises as how best to implement the elements of such a policy. For example, what techniques are available for source reduction, recycling, etc. The answer to this question is not straightforward and depends on the application. The so-called clean technologies do not exist in their own right. If a clean technology is regarded as one that reduces waste generation, and/or material and energy usage, then it can be seen that what may be regarded as a cleaner technology in one industrial sector or application is not necessarily so regarded in another sector. For example, distillation is widely used throughout the chemical industry to recover materials for reuse. Consequently, it would not normally be regarded as a clean technology in this context. Research is ongoing to attain better and more energy efficient separation techniques. On the other hand, in a small paint spraying operation which produces pigment-contaminated solvents, the  17 installation of a small distillation column for solvent recovery would indeed be a cleaner technology. It can thus readily be seen that there is no panacea for reducing wastes. Nevertheless, several general guidelines have been established, which can be supplemented by examples gleaned from experience. The techniques for bringing about waste reduction can be broken down into four major categories as follows (Hunt, 1990): ⚫ Inventory management - Inventory Control - Materials Control ⚫ Production process modification - Operational and maintenance procedures - Materials change -Process equipment modification ⚫ Volume reduction -Source segregation -Concentration ⚫ Recovery - On-site - Off-site Figure 2 Hazardous waste minimization techniques These techniques are discussed in more detail in the following sections. Figure 2 is often used as an alternative means of conveniently summarizing possible waste minimization techniques. It should be noted that waste reduction techniques are generally used in combination so as to achieve maximum effect at the lowest cost. It is  18 important to realize that the impact of a waste reduction technique on all waste streams must be considered. For example, switching from solvent-based to water-based methods may result in lower organic emissions to atmosphere, but can lead to an increased burden on wastewater treatment. Inventory Management Proper inventory control over raw materials, intermediate products, final products and the associated waste streams is an important waste reduction technique. In many cases waste is just out-of-date, off-specification, contaminated, or unnecessary raw materials, spill residues or damaged final products. The cost of disposing of these materials not only includes the actual disposal costs but also the cost of the lost raw materials or product. Inventory management incorporates both inventory and material control. Inventory control Inventory control involves techniques to reduce inventory siz3 and hazardous chemical use while increasing inventory turnover. Proper inventory control can help reduce wastes occurring as a result of the following: excess, out-of- date and no-longer-used raw materials. Methods that can be used are purchasing in small quantities, purchasing in appropriate container sizes and just-in-time purchasing. Material control It is essential to have proper control over the storage of raw materials, products and process waste and the transfer of these items within the process and around the facility. This will minimize losses through spills, leaks or contamination. It will also ensure that the material is efficiently handled and used in the production process and does not become waste. A list of typical sources of losses is given in Table 1. Table 1 Potential sources of process material loss Area Source Loading Leaking fill hose or fill line connections Draining of fill lines between filling Punctured, leaking or rusting containers Leaking valves, pipings and pumps Storage Overfilling of Tanks Improper or malfunctioning overflow alarms Punctured, leaking or rusted containers Leaking transfer pumps, valves, and pipes Inadequate diking or open drain valve Improper material transfer procedures Lack of regular inspection Lack of training program Process Leaking process tanks Improperly operated and maintained process equipment Leaking valves, pipes and pumps Overflow of process tanks; improper overflow controls Leaks and spills during material transfer Inadequate diking Open drains Equipment and tank cleaning Off-specification raw materials  19 Production Process Modification Waste can be significantly reduced by improved process efficiency. Such improvements can range from simple, inexpensive changes in production procedures to the installation of state-of-the-art equipment. Three techniques for production process modification have been identified. These are improved operation and maintenance, material change and equipment modifications. Operational and maintenance procedures Improvements in operation and maintenance are usually relatively simple and cost effective and may lead to significant waste reduction. The techniques used are not new but have not generally been applied to waste reduction problems. A list of examples of operational changes is given in Table 2. A strict maintenance program which stresses corrective and preventive maintenance can reduce waste generation caused by equipment failure. Such a program can help spot potential sources of release and correct a problem before any material is lost. Material change The replacement of materials, used in either a product formulation or in a production process, can either result in the elimination of a hazardous waste or facilitate recovery of a material. For example, CFCs are gradually being replaced by more ozone-friendly products. This is an example of eliminating a hazardous waste source. Replacement of a solvent by one with a different vapor pressure may allow separation and recovery by distillation, condensation, etc. Table 3 gives some examples of waste reduction through material change. As previously emphasized, care must be taken to examine the impact of changes on the total wastes from a process. This is particularly important in the case of material changes. The effect on aqueous wastes of changing from organic solvents to water is a case in point. Table 2 Examples of operational changes to reduce waste generation ◆ Reduce raw material and product loss due to leaks, spills, drag-out, and off-specification process solution ◆ Schedule protection to reduce equipment cleaning, e.g. formulate light to dark paint so the vats do not have to be cleaned out between batches ◆ Inspect parts before they are processed to reduce number of rejects ◆ Consolidate types of equipment or chemicals to reduce the generation of dilute mixed waste with methods such as using dry cleanup techniques, using mechanical wall wipers or squeegees and using compressed gas to clean pipes and increasing drain time ◆ Segregate wastes to increase recoverability ◆ Optimize operational parameters (such as temperature, pressure, reaction time, concentration and chemicals) to reduce by-product or waste generation ◆ Develop employee training procedures on waste reduction ◆ Evaluate the need for each operational step and eliminate steps that are unnecessary ◆ Collect spilled or leaked material for reuse Adapted from Hunt, 1990. Reprinted by permission of McGraw-Hill, Inc.  20 Table 3 Examples of waste reduction through material change Industry Technique Household Eliminate cleaning step by selecting lubricant compatible with next process step appliances Printing Substitute water-based ink for solvent-based ink Textiles Reduce phosphorous in wastewater by reducing use of phosphate-containing chemicals Use ultravioletlet light instead of biocides in cooling towers Air Replace solvent-containing adhesives with water-based products conditioners Electronic Replace water-based film-developing system with a dry system components Aerospace Replace cyanide cadmium-plating bath with a non-cyanide bath Ink Remove cadmium from product manufacture Plumbing Replace haxavalent chrome-plating bath with a low-concentration trivalent fixtures chrome-plating bath Pharmaceuti Replace solvent-based tablet-coating process with a water-based process cals Adapted from Hunt, 1990. Reprinted by permission of McGraw-Hill, Inc. Table 4 Examples of production process modifications for waste reduction Process step Technique Chemical reaction Optimize reaction variables and improve process controls Optimize reactant-addition method Eliminate use of toxic catalysts Improve reactor design Filtration and Eliminate or reduce use of filter acids and disposable filters washing Drain filter before opening Use counter-current washing Recycle spent washwater Maximize sludge dewatering Parts cleaning Enclose all solvent cleaning units Use refrigerated freeboard on vapor degreaser units Improve parts draining before and after cleaning Use mechanical cleaning devices Use plastic-bead blasting Surface finishing Prolong process bath life by removing contaminants Redesign part racks to reduce drag-out Reuse rinse water Install spray of fog nozzle rinse systems Properly design and operate all rinse ranks Install drag-out recovery tanks Install rinse water flow control valves Install drip racks and drain boards Surface coating Use airless air-assisted spray guns Use electrostatic spray-coating system Control coating viscosity with heat units Use high-solids coatings Use powder coating systems  21 Equipment Use high-pressure rinse system cleaning Use mechanical wipers Use counter-current rinse sequence Reuse spent rinse water Use ‘pigs’ to clean lines Use compressed gas to blow out lines Spills and Leaks Use below-sealed valves Install spill basins or dikes Use seal-less pumps Maximize use of welded pipe joints Install splash guards and drip boards Install overflow control devices Adapted from Hunt, 1990. Reprinted by permission of McGraw-Hill, Inc. Volume Reduction While reduction of volume does not, of itself, constitute waste reduction, it frequently facilitates separation and recovery. The reduction in volume may involve complex concentration technologies or may simply consist of source segregation. Some examples of waste reduction through volume reduction are given in Table 5. Table 5 Examples of waste reduction through volume reduction Industry Technique X-ray film Segregate polyester film scrap from other production waste and recycle Resins Collect waste resin and reuse in next batch Printed circuit Use filter press to dewater sludge to 60 percent solids and sell sludge boards for metal recovery Pesticide Use separate bag houses at each process line and recycle collected formulation dust into product Research laboratory Segregate chlorinated and non-chlorinated solvents to allow off-site recovery Aircraft components Use ultrafiltration to remove recoverable oil from spent coolants Paint formulation Segregate and reuse tank-cleaning solvents in paint formulations Furniture Segregate and reuse solvents used to flush spray-coating lines and pumps as coating thinner Adapted from Hunt, 1990. Reprinted by permission of McGraw-Hill, Inc. Recovery Waste recovery should not only be considered after all other waste reduction options have been instituted. The recovery of waste costs money in terms of energy and/or material input. Reduction of waste generation at source is more cost effective, since it represents a reduction in lost raw materials, intermediates, products, etc. Nevertheless, since there will always be some waste generation, recovery represents a viable and cost-effective waste management alternative. Effective recovery is enhanced by segregation of materials, as already outlined. Recovery may be carried out on-site or off-site. On-site recovery is preferable, where possible, since it reduces possible handling losses and allows the management of the waste to remain within the compass of the producer. On-site recovery is particularly appropriate where the recovered  22 material can be reused as a raw material. Table 6 gives some examples of waste recovery techniques. Most on-site recovery systems will generate some type of residue (i.e. contaminants removed from the recovered material). This residue can either be processed for further recovery or properly disposed of. The economic evaluations of any recovery technique must include the management of these residues. In the event that on-site recovery is not feasible, for economic or other reasons, off- site recovery should be considered. In some situations, a waste may be transferred to another company for use as a raw material in the other company’s manufacturing process. Example 1 A production process uses a raw material that contains a small amount of sulphur as an impurity. After processing the sulphur appears as sulphate in an aqueous waste stream. This waste is anaerobically biodegraded to produce a biogas, which is used as a boiler fuel. In the anaerobic digestor, the sulphate is converted to hydrogen sulphide, which results in sulphur dioxide emissions in the boiler flue gases. Outline various methods of reducing the SO2 emissions and identify them as specific waste reduction techniques. Solution (a) Purchase alternative sulphur-free raw material. This is material substitution. (b) Divert waste from this production process away from the anaerobic digestor. This is source segregation. (c) Recover hydrogen sulphide from the gas stream as pure sulphur for sale. This is material reuse. Table 6 Examples of waste reduction through recovery and reuse Industry Technique Printing Use a vapor-recovery system to recover solvents Photographic Recover silver, fixer and bleach solutions processing Metal fabrication Recover synthetic cutting fluid using a centrifuge system Mirror manufacturing Recover spent xylene using a batch-distillation system Printed circuit boards Use an electrolytic recovery system to recover copper and tin/lead from process wastewater Tape measures Recover a nickel-plating solution using an ion-exchange unit Medical instruments Use a reverse-osmosis system to recover a nickel-plating solution Power tools Recover alkaline degreasing baths using an ultrafiltration system Textiles Use an ultrafiltration system to recover dyestuffs from wastewater Hosiery Reconstitute and reuse spent dye baths Food processing Send all solids off-site for by-product recovery Wastewater treatment Reuse waste caustic solids to treat acid waste stream Pickles Transfer waste brine pickle solution to a textile plant as a replacement for virgin acetic acid  23 Chemicals Use spent electrolyte from one division as raw material in another; purify hydrochloric acid in waste stream and sell as a product Industrial and Segregate and sell office paper, corrugated cardboard, paper consumer products trimming and rejected paper products Aluminum die-caster Sell waste fumed amorphous silica for use in concrete Adapted from Hunt, 1990. Reprinted by permission of McGraw-Hill, Inc. Conclusion The basic elements of a waste minimization have been outlined. Many techniques and technologies exist to reduce the generation of waste and to recover wastes once generated. However, a waste minimization program should not rely on technology alone. Senior management commitment, a rigorous waste management program and a continuing emphasis on reduction at source are prerequisites for success. The reward is increased competitiveness, reduced waste treatment and disposal problems, legislative compliance and an improved public image. Some waste will always exist, even after rigorous implementation of a waste minimization program. PROGRESS CHECK: Essay. Total: 100 points. Write your answers clearly. 1. Draw up a plan for a preliminary assessment of waste minimization opportunities in a small automobile repair shop. Identify, in advance, possible target areas for waste reduction. (20 points) 2. Five methods for reduction of waste at source are given in the topic. Prioritize these in terms of preferred order of implementation. Explain why you have made such a decision. (20 points) 3. A car (automobile) manufacturer is designing a new bumper (fender). The material choice lies between plastic or steel. Applying the principles of LCA, which do you think is preferable? (30 points) 4. Liquid milk may be sold in any of four containers, each of one-liter capacity: a.) waxed paper cartons, b.) disposable plastic bottles, c.) re-usable plastic bottles, d.) re-usable glass bottles. Qualitatively assess which is least detrimental to the environment. Explain what factors must be considered. (30 points) REFERENCES: BUWAL (1991). Ecobalance of Packaging Materials State of 1990. BUWAL.  24 Chemical Manufacturers Association (CMA)( 1991). Pollution Prevention Resource Manual. Chemical Manufacturers Association. Davis, M. L. and S. J. Masten (2009). Principles of Environmental Engineering and Science, 2nd Edition. McGraw-Hill. De Hoo, S., H. Dielman, R. Von Berkel, F. Reigenge, H. Brezet, J. Cramer and J. Schots (Ed.) (1991). PREPARE. Dutch Ministry of Economica Affairs. Grujer, U. (1991). Waste Minimization: A Major Concern for the Chemical Industry, Water Science Technology, 24(12), 43-56. Hanlon, D. and C. Fromm (1990). ‘Waste minimization assessments’, in Hazardous Waste Minimization. H. Freeman (Ed.). McGraw-Hill. pp. 71-126 Hunt, G. E. (1990). ‘Waste reduction techniques and technologies’, in Hazardous Waste Minimization. H. Freeman (Ed.). McGraw-Hill. pp. 25-54. Kiely, G. K. (1997). Environmental Engineering. McGraw – Hill. Pedersen, B. (Ed.)(1993). Environmental Assessment of Products - A Course on Life Cycle Assessment, 2nd Edition. UETP-EEE. USEPA (1990). Guides in Pollution Prevention: The Paint Manufacturing Industry. EPA/625/7-90/005/EPA. Willums, J. O. And U. Goluke (1992). From Ideas to Actions: Business from Sustainable Development. International Chamber of Commerce (ICC).