A more sophisticated attempt to deal with environmental pollution emerged to some extent in parallel with the formal adoption of dilute-and-disperse strategies. If there were 'safe' levels of emission into the environment, then there might also be occasions on which emission levels exceeded those considered safe. In these circumstances it was necessary to devise technological strategies to stop emissions leaving industrial factories and entering particular environmental media.
This strategy has been dubbed end-of-pipe abatement because it relies basically on placing filters, scrubbers, separators and purification plants at the end of emission pipelines. These filters and scrubbers are added on to the end of the emission pipe of a particular industrial process, in order to stop the release of a particular contaminant into the local water or the atmosphere.
Without a doubt, end-of-pipe techniques have been effective in reducing certain pollution problems, particularly those which arise from point-source pollution, i.e. emissions from industrial smoke-stacks and pipelines. For example, sewage treatment plants have been used extensively in the Western world to reduce the emission of raw sewage into rivers, lakes and coastal waters. Filters of various kinds have been used to stop certain toxic metals from reaching the local environment. And the addition of scrubbers and filters has helped to reduce the emission of some dangerous air pollutants.
In spite of these successes, the end-of-pipe strategy has some serious drawbacks. First, it is clear that each end-of-pipe technology is a further process to be added on to the existing process. As such, it is subject both to the laws of thermodynamics and to the laws of economics. This means, amongst other things, that it will always be an essentially dissipative process itself, requiring high-quality energy inputs and resulting in low-quality energy outputs. Some of these dissipative flows will in themselves create environmental problems, so that we may be solving one environmental problem only at the expense of introducing another one.
The problem of controlling acid pollution from fossil fuel combustion provides a graphic illustration of these difficulties. When coal and heavy oils are burned, the sulphur content in the fuels combines with air to form sulphur dioxide. This gas is then emitted from the smoke-stack. In the atmosphere, it combines with water vapour to make an acid. This is one of the causes of the well-known problem of acid rain.
The end-of-pipe strategy for controlling acid rain involves fitting flue gas desulphurisation units on to power station and factory chimneys.
Making flue gas desulphurisation units involves using additional raw materials and energy. More importantly, the main commercial route for flue gas desulphurisation is a chemical process which uses wet limestone to convert the flue gas sulphur into gypsum.7 Providing sufficient limestone to carry out flue gas desulphurisation even for one large power station means quarrying and transporting large quantities of limestone.8 And the gypsum by-product presents a considerable waste disposal problem.9
In addition, of course, adding on a technology will involve a cost, over and above the cost of the manufacturing process. These add-on costs may well be lower than the costs of cleaning up environmental damage after it has been created. And in a well-regulated economy, such costs might also be offset against the costs of environmental fees for disposal or penalties for emissions. On the other hand, there may be circumstances in which the additional cost will threaten the productivity of the company operating the process.
Another worrying concern with end-of-pipe strategies is their overall effectiveness. Take the example of an end-of-pipe filter plant used to remove metal contamination emitted from a factory pipe into a river. By removing the heavy metal from the effluent, the filter plant attempts to protect the quality of the receiving water. We know from the conservation laws discussed in Chapter 1, however, that the metal itself persists in some form throughout the process. Even though it has been removed from the effluent, the same amount of metal remains in the sludge or filter-cake from the end-of-pipe plant. But what happens to this sludge? Sometimes, as we shall see later, it is possible to recover metal from the sludge. Sometimes, however, recovery is infeasible for physical or economic reasons. In this case we must look to different disposal options for the sludge. Treatment plant residues usually go either to landfill sites or to incineration plants. Neither of these options allows us to escape the conservation law. The metal must go somewhere. If it goes into a landfill site, there is a danger that the metal may eventually leak out of the site and into the water supply. If the sludge is incinerated, the metal might end up in the atmosphere and later be deposited on the ground or (once again) end up in the water.
One of the most perplexing features of this 'secondary' pollution is how difficult it is to control. Once a material has left the economic system it becomes subject to largely unpredictable environmental forces.
The amount of metal leaking out of landfills or being emitted from incinerator stacks might be small. But the damage it causes depends on where it ends up. The uncontrolled contamination of precious groundwater supplies from leaking landfill sites may turn out to be an even more intractable problem than the controlled contamination of river estuaries.
Finally, we should recognise that the end-of-pipe strategy is effective only in reducing emissions from relatively large point sources. Increasingly, environmental problems are arising from a variety of nonpoint sources. These sources include run-off from agricultural land or from city streets, and the emissions associated with large numbers of individual consumers. The dissipative nature of the economic system has already been pointed out. This dissipative nature is reflected by the increasing number and geographical spread of the actors involved as we move along the industrial chain.
For any one nation, the primary processing of materials will occupy at most a few tens of large mining companies in specified locations. But secondary manufacturing facilities will number at least in thousands and be distributed throughout the country. Consumers—who constitute the last link in the materials flow—will number in millions. The end-of-pipe strategy is really only likely to be effective on specific emissions from large industrial sources. A number of other kinds of emissions—the dissipative uses described in the previous chapter, and the disposal of distributed material products—are much more difficult to address in this fashion.
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