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Cleaner Production Technologies

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Prevention, Control and Remediation

Conventionally, there are three ways of addressing pollution: prevention, control and remediation. These form a hierarchy, in which the first priority or option is prevention, followed by control measures, with remediation as a poor third. Pollution abatement can refer to any means that lessens pollution, or a mitigation of pollution; in practice, it usually means control. Though the hierarchy of the three ideas is in terms of preference or priority, this is not always so in practice: there may be regulatory pressures to choose one path rather than another; one strategy may be less expensive than another, or remediation may be the most urgent - for example, in the event of a major spill or the hazardous dissemination of pollutants from a contaminated site.

Pollution prevention

Pollution prevention can be defined as a strategy or strategies which avoid the creation of pollutants in the first place. In Barry Commoner’s phrase, “If it’s not there, it can’t pollute.” Thus, if a chemical whose use results in pollution is eliminated, there will be “zero discharge” (or “zero emission”) of the pollutant. Zero discharge is more convincing if the chemical is not replaced by another chemical - an alternative or substitute - which results in a different pollutant.

One central strategy of pollution prevention is the banning, elimination or the phasing out (“sunsetting”) of specified chemicals or classes of chemical. (Alternatively, use-restrictions may be specified.) Such strategies are laid down in the form of laws or regulations by national governments, less often by international instruments (conventions or treaties) or by sub-national governments.

A second strategy is pollution reduction, again in the context of prevention rather than control. If the use of a chemical which results in pollution is reduced, then the result will almost always be less pollution. Pollution reduction strategies are exemplified in North America by toxics use reduction (TUR) programmes and in Europe by “clean technology programmes”.

Unlike bans and phase-outs, which usually apply to all (relevant) workplaces within a political jurisdiction, pollution reduction programmes apply to specific workplaces or classes of workplace. These are usually industrial manufacturing (including chemical manufacturing) workplaces over a certain size, in the first instance, though the principles of pollution reduction can be applied generally - for example, to mines, power plants, construction sites, offices, agriculture (in regard to chemical fertilizers and pesticides) and municipalities. At least two US states (Michigan and Vermont) have legislated TUR programmes for individual households which are also workplaces.

Pollution reduction can result in the elimination of specific chemicals, thus achieving the same aims as bans and phase-outs. Again, this would result in zero discharge of the pollutant concerned, but requirements to eliminate specific chemicals are not part of pollution reduction programmes; what is prescribed is a general programme with a flexible range of specified methods. A requirement to eliminate a specific chemical is an example of a “specification standard”. A requirement to institute a general programme is a “performance standard” because it allows flexibility in the mode of implementation, though a specific mandatory target (outcome) for a general programme would (confusingly) count as a specification standard. When they have to choose, businesses usually prefer performance to specification standards.

Pollution control

Pollution control measures cannot eliminate pollution; all they can do is to mitigate its effects on the environment. Control measures are instituted “at the end of the (waste) pipe”. The usefulness of control measures will depend on the pollutant and the industrial circumstance. The main methods of pollution control, in no particular order, are:

  • the capture and subsequent storage of pollutants
  • filtration, whereby airborne or waterborne pollutants are removed from the waste stream by physical methods such as meshes, filters and other permeable barriers (such as coke)
  • precipitation, whereby the pollutant is chemically precipitated and then captured in its transformed state or captured by physical methods such as an electrostatic charge
  • destruction - for example, incineration, or neutralization, whereby pollutants are transformed chemically or biologically into substances which are less harmful
  • dilution, whereby the pollutant is diluted or flushed in order to lessen its effects on any one organism or on an ecosystem; or concentration to lessen the effect of disposal
  • evaporation or dissolution - for example, dissolving a gas in water
  • utilization - for example, transforming a pollutant into a potentially useful (though not necessarily less toxic) product (such as sulphur dioxide into sulphuric acid or using solid waste as hard core or road bed)
  • out-of-process recycling (where the recycling is not an integral part of the production process)
  • media-shift, whereby a waste-stream is diverted from one medium, such as air, soil or water, to another, on the rationale that the medium-shift makes the pollutant less harmful
  • state-changes—a change to the solid, liquid or gaseous state on the rationale that the new state is less harmful.


Pollution remediation

Remediation is needed to the extent that pollution prevention and control fail. It is also very expensive, with the costs not always accruing to the polluter. The modes of remediation are:

The clean-up of contaminated sites

Clean-up has a common sense meaning, as when an employer is required to “clean up his act”, which can mean a large number of different things. Within environmental protection, clean-up is a technical term meaning a branch or a mode of remediation. Even within this restricted use of the term, clean-up can mean (1) the removal of pollutants from a contaminated site or (2) the rehabilitation of a site so that it is restored to its full use-potential. Again, clean-up sometimes refers to nothing more than the containment of pollutants within a site, area or body of water—for example, by capping, sealing or the construction of an impermeable floor.

To be successful, clean-up has to be 100% effective, with full protection for workers, bystanders and the general public. A further consideration is whether the clean-up materials, methods and technology do not create further hazards. Though it is desirable to use engineering controls to protect clean-up workers, there will almost always be a need for appropriate personal protective equipment. Normally, workers engaged in remediation are classified as hazardous-waste workers, though aspects of such work are undertaken by fire fighters and municipal workers, among others.

A large number of physical, chemical, biological and biotechnological agents and methods are used in the clean-up of contaminated sites.

Hazardous-waste treatment

Most treatment of hazardous (or toxic) waste now takes place in purpose-built facilities by hazardous-waste workers. From an environmental point of view, the test of effectiveness of a hazardous-waste facility is that it produces no outputs which are not inert or virtually inert, such as silica, insoluble inorganic compounds, insoluble and non-corrosive slags, gaseous nitrogen or carbon dioxide - though carbon dioxide is a “greenhouse gas” which causes climate change and is, thus, a further environmental detriment.

A further test is that the facility be energy efficient - that is, energy is not wasted - and as energy non-intensive as possible (i.e., the ratio of energy use to the volume of waste treated be as low as possible). A general rule of thumb (it is fortunately not a universal law) is that the more effective the pollution (or waste) abatement strategy, the more energy is consumed, which by sustainable development criteria is another detriment.

Even when the workers are properly protected, it is easy to see the drawbacks of hazardous-waste treatment as a mode of addressing pollution. Pollution prevention methods can be applied to the operation of the treatment process but they cannot be applied to the principal “input” - the waste to be treated. Hazardous-waste treatment facilities will usually require at least as much energy to treat the waste as was expended in its creation, and there will always be further waste as an output, however inert or non-toxic.

Spills and leaks

The same considerations will apply to chemical spills and leaks as to the clean-up of contaminated sites, with the further hazards caused by the urgency of the clean-up. Workers cleaning up spills and leaks are almost always emergency workers. Depending on the scale and the nature of the pollutant, leaks and spills can become major industrial accidents.

The Modes of Pollution Prevention

Definition and philosophy

The definition of pollution prevention may seem to be a trivial matter, but it is important because advocates of pollution prevention want, as a principle of policy, to see a single-minded and aggressive prevention strategy at the expense of control methods, and to avoid remediation. The more strictly pollution prevention is defined, they say, the more likely it is to succeed as a practical strategy. Conversely, the more widely employers are allowed to define the term, the more likely their activities are to result in a mix of the same old (failed) strategies. Employers sometimes reply that even toxic waste can have a market value, and control methods have their place, so pollution is really only potential pollution. Besides, zero discharge is impossible and leads only to false expectations and misguided strategies. Proponents of pollution prevention respond that unless we have zero discharge as an aim or practical ideal, pollution prevention will not succeed and environmental protection will not improve.

Most of the strict definitions of pollution prevention have, as a sole or central element, the avoidance of the use of chemicals which result in pollutants so that pollution is not created in the first place. Some of the most important definitional controversies concern recycling, which is dealt with in the context of pollution prevention below.


One possible objective of pollution prevention is zero discharge of pollutants. This is sometimes referred to as “virtual elimination”, since even zero discharge cannot solve the problem of contaminants already in the environment. Zero discharge of pollutants is possible using pollution prevention methods (while control methods cannot achieve zero in theory and are even less effective in practice, usually owing to lax enforcement). For instance, we can envisage automobile production in which there is zero discharge of pollutants from the plant; other waste is recycled and the product (the car) consists of parts which are reusable or recyclable. Certainly, zero discharge of specific pollutants has been achieved - for example, by modifying the production process in wood pulp mills so that no dioxins or furans are discharged in the effluent. The aim of zero discharge has also been written into environmental laws and into the policies of bodies commissioned to abate pollution.

In practice, zero discharge often gives way to target reductions - for example, a 50% reduction in pollution emissions by such-and-such a year. These targets or interim targets are usually in the form of “challenges” or aims by which to measure the success of the pollution prevention programme. They are rarely the product of a feasibility analysis or calculation, and there are invariably no penalties attached to failure to attain the target. Nor are they measured with any precision.

Reductions would have to be measured (as opposed to estimated) by variations on the formula:

Pollution (P) = Toxicity of the pollutant (T) × Volume (V) of the discharges


P = T x V x E (exposure potential).

This is very difficult in theory and expensive in practice, though it could be done in principle by utilizing hazard assessment techniques (see below). The whole issue suggests that resources would be better allocated elsewhere - for example, in ensuring that proper pollution prevention plans are produced.

In regard to chemical pesticides, the objective of use-reduction can be achieved by the methods of integrated pest management (IPM), though this term, too, is capable of a wide or a strict definition.


The main methods of pollution prevention are:

  • The elimination or phasing out of specific hazardous chemicals
  • Input substitution - replacing a toxic or hazardous substance with a non-toxic or less hazardous substance or with a non-toxic process. Examples are the substitution of water-based for synthetic organic dyes in the printing industry; water - or citrus-based solvents for organic solvents; and, in some applications, the substitution of vegetable for mineral oils. Examples of non-chemical substitution include the substitution of pellet blasting technology for the use of fluid chemical paint strippers; the use of high-pressure hot water systems instead of caustic cleaning; and the substitution of kiln-drying for the use of pentachlophenols (PCPs) in the lumber industry.
    In all cases, it is necessary to perform a substitution analysis to ensure that substitutes are genuinely less hazardous than what they replace. This is at least a matter of organized common sense, and at best the application of hazard assessment techniques (see below) to the chemical and its proposed substitute.
  • Product reformulation - substituting for an existing end-product an end-product which is non-toxic or less toxic upon use, release or disposal
    Whereas input substitution refers to the raw materials and adjuncts at the “front end” of the production process, product reformulation approaches the issue from the final product end of the production cycle.


General programmes to produce products which are more environmentally benign are examples of “economic conversion”. Examples of particular measures in the area of product reformulation include the production of rechargeable batteries instead of throw-away types and the use of water-based product coatings instead of those based on organic solvents and the like.

Again, substitution analysis will be necessary to ensure that the net environmental benefit is greater for the reformulated products that it is for the originals.

  • Production unit redesign modernization or modification, which results in less chemical use or in the use of less toxic substances.
  • Improved operation and maintenance of the production unit and production methods, including better housekeeping, more efficient production quality control, and process inspections.
    Examples are spill prevention measures; the use of spill-proof containers; leak prevention; and floating lids for solvent tanks.
  • Using less and reusing more. For instance, some degreasing operations take place too frequently on a single item. In other cases, chemicals can be used more sparingly in each operation. De-icing fluids can sometimes be reused, a case of “extended use”.
  • Closed-loop methods and in-process recycling. Strictly speaking, a closed-loop process is one in which there are no emissions into the workplace or into the outside environment, not even waste water into surface water or carbon dioxide into the atmosphere. There are only inputs, finished products, and inert or non-toxic wastes. In practice, closed-loop methods eliminate some, but not all, hazardous releases. To the extent that this is achieved, it will count as a case of in-process recycling (see below).



Any definition of pollution prevention is likely to result in a number of “grey areas” in which it is not easy to distinguish prevention measures from emission controls. For instance, to qualify as a prevention method, a phase of a production process may have to be “an integral part of the production unit”, but how far away the phase has to be from the periphery of the production process in order to qualify as a prevention measure is not always clear. Some processes may be so remote from the heart of an operation that they look more like an “add on” process and, thus, more like an “end of pipe” control measure than a prevention method. Again, there are unclear cases like a waste pipe that provides the feedstock for a neighbouring plant: taken together, the two plants provide a kind of closed loop; but the “upstream” plant still produces effluent and, thus, fails the prevention test.

Similarly with recycling. Conventionally, there are three types of recycling:

  • in-process recycling - for example, when dry-cleaning solvent is filtered, cleaned and dried, then reused within a single process
  • out-of-process but on-site, as when pesticide production waste is cleaned and then reused as the so-called inert base in a new production run
  • out-of-process and off-site.


Of these, the third is usually ruled out as not qualifying as pollution prevention: the more remote the recycling site, the less of a guarantee that the recycled product is actually reused. There are also hazards in the transporting of waste to be recycled, and the financial uncertainty that the waste will have a continuous market value. Similar, though less acute, considerations apply to out-of-process but on-site recycling: there is always a possibility that the waste will not actually be recycled or, if recycled, not actually reused.

In the initial pollution prevention strategies of the 1980s, on-site but out-of-process recycling was ruled out as not being a genuine pollution prevention measure. There was a fear that an effective pollution prevention programme would be compromised or diluted by too great an emphasis on recycling. In the mid-1990s, some policy-makers are prepared to entertain on-site, out-of-process recycling as a legitimate pollution prevention method. One reason is that there are genuine “grey areas” between prevention and control. Another reason is that some on-site recycling really does do what it is supposed to do, even though it may not technically qualify as pollution prevention. A third reason is business pressure: employers see no reason why techniques should be ruled out it they serve the purposes of a pollution prevention programme.

Pollution prevention planning

Planning is an essential part of pollution prevention methodology, not least because the gains in both industrial efficiency and environmental protection are likely to be in the longer term (not immediate), reflecting the sort of planning that goes into product design and marketing. The production of periodic pollution prevention plans is the most usual way of realizing pollution prevention planning. There is no single model for such plans. One proposal envisages:

  • aims and objectives
  • chemical inventories and estimates of discharges into the environment
  • pollution prevention methods used and methods proposed
  • responsibilities and action in the event of the plan not being fulfilled or realized.


Another proposal envisages:

  • a review of production processes
  • identification of pollution prevention opportunities
  • a ranking of the opportunities and a schedule for the implementation of the selected options
  • measures of the success of the plan after the implementation period.


The status of such plans varies widely. Some are voluntary, though they can be spelled out in law as a (voluntary) code of practice. Others are mandatory in that they are required (1) to be kept on-site for inspection or (2) submitted to a regulatory authority on completion or (3) submitted to a regulatory authority for some form of scrutiny or approval. There are also variations, such as requiring a plan in the event that a “voluntary” plan is, in some way, inadequate or ineffective.

The degree to which mandatory plans are prescriptive also varies - for example, in regard to penalties and sanctions. Few authorities have the power to require specific changes in the content of pollution prevention plans; almost all have the power to require changes in the plan in the event that the formal requirements have not been met - for example, if some plan headings have not been addressed. There are virtually no examples of penalties or sanctions in the event that the substantive requirements of a plan have not been met. In other words, legal requirements for pollution prevention planning are far from traditional.

Issues surrounding the production of pollution prevention plans concern the degree of confidentiality of the plans: in some cases, only a summary becomes public, while in other cases, plans are released only when the producer fails in some way to comply with the law. In almost no cases do the requirements for pollution prevention planning override existing provisions regarding the trade secrecy or the business confidentiality of inputs, processes or the ingredients of products. In a few cases, community environmental groups have access to the planning process, but there are virtually no cases of this being required by law, nor are the legal rights of workers to participate in the production of plans widespread.


In the Canadian provinces of British Columbia and Ontario, pollution prevention measures are “voluntary”; their effectiveness depends on “moral suasion” on the part of governments and environmentalists. In the United States, about half (26) of the states have some form of legislation, while in Europe, several northern countries have legislated clean technology programmes. There is quite a wide variety in both the content and the effectiveness of such legislation. Some laws define pollution prevention strictly; others define it widely or loosely and cover a wide variety of environmental protection activities concerning pollution and waste, not just pollution prevention. The New Jersey law is highly prescriptive; those of the Commonwealth of Massachusetts and the States of Minnesota and Oregon involve a high degree of government scrutiny and assistance; that of Alaska is little more than a statement of the government’s intentions.

Health, safety and employment

Pollution prevention is of central concern to occupational health: if the use of toxic substances decreases, there will almost always be a corresponding decrease in worker exposure to toxic substances and, thus, in industrial diseases. This is a prime case of prevention “at the source” of the hazard and, in many cases, the elimination of hazards by “engineering controls”
(i.e., methods), the first and best line of defence against chemical hazards. However, such preventive measures are different from one traditional strategy, which is the “total isolation” or the “total enclosure” of a chemical process. While total enclosure is highly useful and highly desirable, it does not count as a pollution prevention method since it controls, rather that reduces intrinsically, an existing hazard.

The pollutants which pose hazards to workers, communities and the physical environment alike, have usually been addressed primarily because of their impact on human communities (environmental health). Though the greatest exposures are often received by workers within a workplace (workplace pollution), this has not, so far, been the prime focus of pollution prevention measures. The Massachusetts legislation, for instance, aims to reduce the risks to the health of workers, consumers and the environment without shifting the risks between workers, consumers and parts of the environment (New Jersey is similar). But there was no attempt to focus on workplace pollution as a major detriment, nor was there a requirement to accord a primacy to the chief human exposures to hazards - often the workers. Nor is there any requirement to train workers in the discipline of pollution prevention.

There are several reasons for this. The first is that pollution prevention is a new discipline in the context of a general, traditional failure to see environmental protection as a function of processes utilized and adopted within workplaces. A second reason is that worker-management co-determination in the area of environmental protection is not well advanced. Workers in many countries have legal rights, for instance, to joint workplace health and safety committees; to refuse unsafe or unhealthy work; to health and safety information; and to training in health and safety issues and procedures. But there are few legal rights in the parallel and often overlapping area of environmental protection, such as the right to joint union-management environment committees; the right of employees to “blow the whistle” (go public) on an employer’s anti-environmental practices; the right to refuse to pollute or to degrade the outside environment; the right to environmental information; and the right to participate in workplace environmental audits (see below).

The impacts of pollution prevention planning on employment are hard to gauge. The explicit aim of pollution prevention initiatives is often to increase industrial efficiency and environmental protection at the same time and by the same set of measures. When this happens, the usual effect is to decrease overall employment within any given workplace (because of technological innovation) but to increase the skills required and then to increase job security (because there is planning for a longer-term future). To the extent that the use of raw materials and adjuncts is reduced, there will be decreased chemical manufacturing employment, though this is likely to be offset by the implied transition of feedstock to speciality chemicals and by the development of alternatives and substitutes.

There is one aspect of employment which pollution prevention planning cannot address. Pollution emissions from a single facility may decrease but to the extent that there is an industrial strategy to create wealth and value-added employment, an increase in the number of production facilities (however “clean”) will tend to nullify the environmental protection gains already achieved. The most notorious failing in environmental protection measures - that pollution emission reductions and controls are nullified by an increase in the number of sources - applies, unfortunately, to pollution prevention as well as to any other form of intervention. Ecosystems, according to one respected theory, have a “carrying capacity”, and that limit can be reached equally by a small number of highly polluting or “dirty” sources or by a correspondingly large number of clean ones.

Workplace environmental audits

Pollution prevention planning can form part of or be accommodated in a workplace environmental audit. Though there are many versions of such audits, they are likely to be in the form of a “site audit” or “production audit”, in which the whole production cycle is subjected to both an environmental and a financial analysis.

There are roughly three areas of sustainable development and environmental protection which can be covered in a workplace audit:

  • the conservation of natural resource inputs - for example, minerals, water and wood products
  • energy use, which may also include consideration of energy sources, energy efficiency, energy intensiveness and energy conservation
  • pollution prevention, control and remediation.


To the extent that pollution prevention is successful, there will be a corresponding decrease in the importance of control and remediation measures; pollution prevention measures can form a major part of a workplace environmental audit.

Traditionally, businesses were able to “externalize” environmental detriments through such means as the profligate use of water or unloading their wastes onto the outside community and the environment. This has led to demands for taxes on the “front end” such as water use or on “outputs” such as environmentally unfriendly products or on wastes (“pollution taxes”).

In this way, costs to business are “internalized”. However, it has proved difficult to put the right price on the inputs and on the detriments - for example, the cost to communities and the environment of wastes. Nor is it clear that pollution taxes reduce pollution in proportion to the amounts levied; taxes may well “internalize” costs, but they otherwise only add to the cost of doing business.

The advantage of environmental auditing is that the audit can make economic sense without having to “cost” externalities. For instance, the “value” of waste can be calculated in terms of resource input loss and energy “non-utilization” (inefficiency) - in other words, of the difference in value between resources and energy on one side and the value of the product on the other. Unfortunately, the financial side of pollution prevention planning and its part in workplace environmental audits is not well advanced.

Hazard assessment

Some pollution prevention schemes work without any hazard evaluation - that is, without criteria to decide whether a plant or facility is more or less environmentally benign as a result of pollution prevention measures. Such schemes may rely on a list of chemicals which are objects of concern or which define the scope of the pollution prevention programme. But the list does not grade chemicals as to their relative hazardousness, nor is there a guarantee that a chemical substitute not on the list is, in fact, less hazardous than a listed chemical. Common sense, not scientific analysis, tells us how to go about implementing a pollution prevention programme.

Other schemes rest on criteria for assessing hazardousness, that is, on hazard assessment systems. They work, essentially, by laying down a number of environmental parameters, such as persistence and bioaccumulation in the environment, and a number of human health parameters which serve as measures of toxicity - for example, acute toxicity, carcinogenicity, mutagenicity, reproductive toxicity and so on.

There is then a weighted scoring system and a decision procedure for scoring those parameters on which there is inadequate information on the chemicals to be scored. Relevant chemicals are then scored and ranked, then (often) assembled in groups in descending order of hazardousness.

Though such schemes are sometimes devised with a specific purpose in mind - for example, for assessing priorities for control measures or for elimination (banning) - their essential use is as an abstract scheme which can be used for a large variety of environmental protection measures, including pollution prevention. For instance, the top group of scored chemicals could be the prime candidates for a mandatory pollution prevention programme, or they could be candidates for phasing-out or substitution. In other words, such schemes do not tell us how much we should reduce environmental health hazards; they tell us only that any measures we take should be informed by the hazard assessment scheme.

For instance, if we have to make decisions about substituting a less hazardous chemical for a more dangerous one, we can use the scheme to tell us whether, prima facie, the substitution decision is a good one: we run both chemicals through the scheme to determine whether there is a wide or merely a narrow gap between them regarding their hazardousness.

There are two sorts of considerations which rarely fall within the scope of hazard assessment schemes. The first is exposure data, or the potential for human exposure to the chemical. The latter is difficult to calculate, and, arguably, it distorts the “intrinsic hazard” of the chemicals concerned. For instance, a chemical could be accorded an artificially low priority on the grounds that its exposure potential is low; though it may, in fact, be highly toxic and relatively easy to deal with.

The second sort of consideration is the socioeconomic impact of eliminating or reducing the use of the chemical concerned. While we can start to make substitution decisions on the basis of the hazard analysis, we would have to make a further and distinct socioeconomic analysis and consider, for example, the social utility of the product associated with the chemical use (which may, e.g., be a useful drug), and we would also have to consider the impact on workers and their communities. The reason for keeping such analysis separate is that it is impossible to score the results of a socioeconomic analysis in the same way that the intrinsic hazards of chemicals are scored. There are two entirely distinct sets of values with different rationales.

However, hazard assessment schemes are crucial in assessing the success of pollution prevention programmes. (They are also relatively new, both in their impact and their utility.) For instance, it is possible to apply them without reference to risk assessments, risk analysis and (with reservations) without reference to cost-benefit analysis. An earlier approach to pollution was to first do a risk assessment and only then decide what sort of action, and how much, was necessary to reduce the risk to an “acceptable” level. The results were rarely dramatic. Hazard assessment, on the other hand, can be utilized very quickly and in such a way that it does not delay or compromise the effectiveness of a pollution prevention programme. Pollution prevention is, above all, a pragmatic programme capable of constantly and speedily addressing pollution issues as they arise and before they arise. It is arguable that traditional control measures have reached their limit and only the implementation of comprehensive pollution prevention programmes will be capable of addressing the next phase of environmental protection in a practical and effective way.



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