by Ulrich Frings and Jürgen Porst

With increasing industrialization in the developing countries in recent years there has been a corresponding increase in the importance of environmental protection. Apart from the environmental pollution caused by industrial plants and urban centres, a major source of soil and groundwater pollution is waste oil.

Prevention of contamination by waste oil is more or less a problem of awareness and of the collection system: most waste oil is generated by private consumers, who are usually not aware of the potential danger, at innumerable different locations. An inadequate infrastructure, a lack of government regulations, and insufficient controls are all factors which limit the likelihood that waste oil will be disposed of in an ecologically safe way.

Environmental pollution by waste oil

Waste oil seeping into the ground contaminates both the soil and the groundwater. Depending on the nature of the soil and the distance to the groundwater table, the oil can spread very quickly under the surface over a large area.

The toxic impact of the oil varies according to its origins. Engine and transmission oils in water are not toxic below the smell and taste threshold (0.001 - 0.01 mg/l). Above this threshold water is undrinkable. One drop of oil can pollute about 1 million litres of groundwater.

Depending on the quantity of water and the concentration of dissolved substances in it, other oil products may be toxic even below the smell and taste threshold.

Transformer oils contain polychlorinated biphenyls (PCBs), which are highly carcinogenic.

Sources of waste oil

Waste oil may be any of the following:

• Iubrication oils from motor vehicles, combustion engines and gearboxes (often by far the largest source in the Third World)

• hydraulic oils from transformers

• other industrial oils from axles,turbines etc.

Recycling possibilities

Owing to the variety of types of waste oil and its widespread production, possibilities for economic recycling are limited. In general, to avoid secondary contamination resulting from re-use, waste oil from engines and transmissions should not be mixed with other types of waste oil.

Refining

Waste oil can be refined, in highly complex plants, to produce highquality lubricating oil. There are several methods in use, the most common being the sulphuric acid process. All the methods depend heavily on an efficient collection system capable of providing the necessary minimum quantity of waste oil of a certain quality. On the other hand, the lubricating oil thus produced can be used as a substitute for costly imports. The advantages and disadvantages can thus be summarized as follows:

Advantages:

• recycling can produce a highquality lubrication oil;

• recycling can help reduce imports.

Disadvantages:

. recycling produces new waste with a high toxic materials content (with the sulphuric acid method, for example, 4 tons of waste water, 10 tons of sludge, and 3.2 tons of deposits are produced for every 100 tons of waste oil refined);

it is a high-tech solution which requires experienced personnel the process uses considerable amounts of electricity, water and chemicals (e 9. sulphuric acid, bleaching clay, ammonia etc.); supplies of these are either limited or they have to be imported;

a functioning collection system has to be established.

Overall, waste oil refining only seems possible in countries where:

• waste oil producers are regionally concentrated;

• there are sufficient technical personnel: and

• at least some of the raw materials needed are locally available.

Filtration

All oils which have not been heated in use can be filtered (e. 9. shaft lubricating oil, transformer oil, hydraulic oil, which are only polluted by small particles; their lubricating characteristics are not affected). Mechanical filtration can be carried out by small mobile units- experienced technicians are not needed. Waste production and energy consumption are comparatively low. Moreover, no additional raw materials are required, and so costs of materials from outside suppliers are extracted to the investment and the filter material. On the other hand, they help to reduce running costs. All in all, mechanical filtration can be recommended for both public and private companies which use heavy machines (e. g. road-building machinery).

Combustion

Waste oil can be burned in the following production processes, where the toxic contents of the oil are at least partially absorbed by the product:

• cement factories

• plaster production, lime kilns

• asphalt and tar production

• grass works

• porcelain works.

The use of waste oil as a fuel additive in cement plants in particular is an easy and ecologically acceptable way of re-using the oil if it cannot be reprocessed.

Certain special oils, e. 9. transformer oils, cannot be recycled in this way. They contain toxic hydrocarbons which cannot be bound in the products.

Pure waste oil should not be burned, because this causes numerous pollutants (heavy metals. toxic hydrocarbons. dust etc.) to be emitted into the air we breathe. It can, however, be used as an additive (1 to 5%) to fuel or crude oil in oil-burning facilities, as mentioned above.

Steps towards a waste oil collection system

Protection of the environment against waste oil depends to a great extent on the existence of a functioning collection system. The basic precondition for this is that both the population and the decision-makers responsible are aware of the need. The next most important factors are the legal basis and the provision of collection points which are not too far from consumers. Only after the collection system has been established will economic utilization or recycling be possible. A waste oil project should therefore include the following stages:

1. campaigns to alert people to the dangers of waste oil;

2. measures to promote awareness among decision-makers;

3. establishment of collection points along main roads and at locations where oil is frequently changed;

4. action to make public authorities (e.g. power authorities, road construction departments) aware of possibilities for filtration;

5. interim use of waste oil in waste incineration, or burning of the oil in drums and barrels in the open air, until more environmentally acceptable solutions are identified and put into practice;

6. identification of potential uses (e.g., in cement works);

7. initiation of transport of waste oil to plants where it can be used.

Introduction of a waste oil collection system in the Yemen Arab Republic

The first steps in setting up a waste oil collection system inYemen were taken in 1987, as part of a rural development project. Before this, waste oil had been dumped anywhere. Even the power stations let their waste oil (2,000 litres per month) run straight into the fields. As a first step, numerous meetings and many private discussions were held to increase public awareness of the problem. This increased awareness resulted in the inhabitants putting pressure on owners of workshops in the town to stop getting rid of their waste oil by simply letting it drain off into the street. At the same time, the Local Development Authority placed a number of waste oil tanks near the workshops and the power station, and the Governor issued a regulation under which unauthorized dumping is fined: the penalty for private persons is 5,000 YR (about DM 1,000), and for businesses 10,000 YR. The municipal authorities have instructions to empty the tanks and use the oil for waste incineration (previously, fuel was added to the solid waste for incineration purposes because of the low proportion of organic matter it contains). Initial problems have been overcome, and the system has now been operating for one-and-half years without any major difficulties. The next step will be to collect waste oil from other power stations in the area and transport it to the cement plant (about 120 km away), which already uses waste oil from another area. However, this can only be done if the quantity of waste oil is large enough to motivate a private entrepreneur to engage in the business. The amount of waste oil now available would generate almost income to cover the cost of transport to the cement factory. As crude oil prices and the quantity of waste oil collected increase, the system will become economically viable.

The fact that a waste oil collection system can be an economically viable proposition is clearly illustrated .

Abstract

Waste oil can be recycled in a variety of ways. It can be processed to produce lubricating oil, in a technologically complex process, or filtered, i.e. mechanically treated. But filtration is only possible if the oil was never heated. A third possible disposal method - under certain conditions - is burning. However, none of these methods is economically viable unless backed up by an efficient waste oil collection system.

Résumé

Les huiles usées peuvent être traitees de différentes façons. D'une part, un processus technique très complique permet de les transformer en huile de graissage. D'autre part, on peut les filtrer et donc leur fair subir un traitement mécanique. Ceci n'est cependant possible que dans le cas d'huiles n'ayant jamais ete chauffées au cours de leur utilisation préalable. Une troisième possibilite d'élimination des huiles usées consiste, dans certaines conditions, a les brûler. Ces trots possibilités ne sont cependant réalisablas que dans la mesure ou un système gable de collecte des huiles usées existe.

Extracto

El aceite viejo puede reciclarse de diversos modos. Por ejemplo, mediante un complicado procedimiento técnico pare convertirlo en aceite lubricante. Por otra parte, también es posible filtrarlo, es decir, someterlo a un procedimiento de recuperación mecánico. Pero esto solo es posible en un aceite que no se haya recalentado durante todo el períado de uso. Y como tercera posibilidad de eliminación existe, bajo ciertas condiciones, la incineración. Pero sodas estas tres posibilidades son factibles solo si existe un sistema de recogida de aceite viejo que funcione satisfactoriamente.