Does it make sense to burn our domestic waste in power stations?

In central Europe, most of the municipal waste is incinerated, because it is difficult to find land for dumpsites, and there are large municipalities. This used to cause major emission problems, because municipal waste is a complex mix of materials – metals, some materials which only burn with difficulty, plastics and other materials containing chlorine and producing hydrochloric acid. To make matters worse, some materials such as PCBs did not burn completely, but were released into the environment. Both PCBs and chlorophenols used as wood preservatives contained also dioxins as impurities, and dioxins can even be created during the incineration process.

High quality technology needed

Emission problems are not necessarily unavoidable in waste incineration. In older incinerator plants, often there was no flue gas cleaning at all or it was poor and ineffective. Therefore dioxin emissions were quite high, and they polluted nearby fields and pastures, where cattle fed on this grass and thus the dioxins entered to the food chain in meat and milk. However, when technology improved, dioxin emissions decreased rapidly and this could be seen both in decreased dioxin concentrations in meat and dairy products, and also in human concentrations as measured from breast milk.

If the incineration temperature is high enough to destroy dioxin-like compounds, and flue gas cleaning is properly done, emissions are no longer a reason to avoid municipal waste incineration. There is an interesting solution in Vienna where the large modern Spittelau incineration plant is situated in the very centre of the town. No attempt has been made to hide the building; it is very prominent and colourful with a glazed tile-coated chimney. The concept is to bring the incinerator as close as possible to the origin of the municipal waste to avoid expending energy in bringing the waste to the plant, and also traffic risks are as few as possible. Secondly, since the plant is in the centre of town, the energy it produces can heat the town. Energy is utilised as effectively as possible in the combined production of electricity and heat. If the plant was situated away from the city then only electricity could be produced and this would not be nearly so efficient.

How about indirect consequences?

In addition to the risk of toxic emissions, waste incinerators have been opposed also for other kinds of reasons. These are rather matters of principle. It has been claimed that waste incineration destroys the logic of saving, reuse and recycling. In other words, if a substantial part of waste is incinerated, material for recycling remains so scarce that it is no longer profitable to recycle. Moreover people might not be motivated to save or recycle, because it is too easy to throw everything away and cart it off to be incinerated.

The problem with this kind of thinking is that it is possible to motivate a certain proportion of the population to sort their waste into ten different fractions, but others will not bother. This leads to a situation that responsible people sort their waste very carefully, but others just throw everything into the general garbage bin. These wastes then end up in a dumpsite, and this is by far the worst solution. This means that the crucial comparison is in fact: which is the greater problem, (a) a large amount of waste ending up in a dumpsite or (b) that the combustible part of waste produces energy and is not recycled for more valuable use. If the waste is incinerated, only the part of the ashes which is not usable at all e.g. for road construction, ends up in the dumpsite.

Sensible recycling is profitable

One should not be too pessimistic when it comes to reuse or recycling, if people feel it is rational. Good examples are recycling of glass and office paper, and the reuse of glass bottles. Most people are ready to an effort when they understand the issue and see it as meaningful. It is not possible to make the whole population behave in the ideal way, but if the less valuable organic waste is incinerated, no duplication of systems is needed, one for responsible citizens and another for the others.

It is a question of typical life-cycle analysis. One needs to calculate, how much energy is needed to collect, transport, clean and reprocess poor-quality paper and cardboard, in other words relatively cheap materials, to produce another cheap raw material. In general, recycled material cannot be used for its initial quality purpose. Office paper can be the raw material for recycled paper, but mixed paper can only be used to make cardboard or egg boxes and so forth. This must be compared with the possibility that newspaper or at least office paper is made of wood. In a life cycle analysis, all details are investigated step by step. The next question to be asked is what would happen to wood if it were not used for paper production. If it is burned for energy, one might ask why not make paper first and then burn the paper after it has been used. But if wood is used to make furniture or construction material, then this is clearly more valuable use than paper, and it should be preferred.

Analyses with no prejudice are needed

This little example above illustrates that waste incineration and recycling are not simple straightforward questions. One has to approach the problem with an open mind. It might well be that recycling of office paper is environmentally friendly, but not recycling of cardboard or construction waste. In either case, taking them to a dumpsite is irrational. If there is combustible material present in dumpsites this can catch fire and produce large amounts of dioxins. For all of these reasons, the European Union has listed the methods in order of preference: reuse, recycling, energy production, and dumpsite and the best mix of these options should be sought.

Often a lengthy analysis is needed considering also the local conditions. However, the solution which is best for the environment is often also most economical, because price is not determined by chance. High expenses mean investing in land use, energy consumption or labour, and therefore very expensive solutions are often also burdensome to the environment.

Waste incineration is a complicated issue requiring a thorough life-cycle analysis. Incineration in good quality power plant is, however, always better than burying energy-containing materials such as paper, cardboard, and waste wood in dumpsite.

Notes and references

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