Residual products are an almost inescapable feature of industrial processes. When they can no longer be re-utilized in the process, they are classified as waste. Facilities for the destruction of unsorted waste have been built in Sweden and at a number of locations in other countries.
Not all waste can be destroyed. Inorganic residual products are disposed of on a landfill site instead. Landfill sites have a restricted life at the current time, and the methods used require supervision.
Both destruction plants and landfill sites have been built according to the principle that the waste does not need to be sorted before final processing. Both destruction plants and landfill sites are constructed to swallow everything.
This is unfortunate from an environmental point of view. It is out of step with the modern concept of recycling, and it does not result in reduced volumes of waste. Furthermore, the investment in destruction plants for unsorted waste is very high, as are the operating costs of landfill sites.
A developed recycling concept also calls for increased recycling of industrial chemical waste. Various materials have to be kept separate in order to achieve this. Waste is classified according to new principles based on the ease of processing the waste. The following is an initial classification:
1. Materials that are difficult to handle, but usually possible to recycle. Examples are oil sludge, paint waste, adhesive waste and solvents.
2. Environmentally hazardous waste containing substances which society has decided must not be used, and must be destroyed. Examples of such materials are PCB's, pesticides, chlorinated solvents and freons.
3. Inorganic waste which cannot be recycled with our present knowledge, but must be disposed of in landfill sites. Examples are metal hydroxide sludge and contaminated soils, etc.
Neither technology nor costs are standing in the way of sorting the various types of waste at source. What is needed is a new approach. The possibility of recycling material from the first group already exists. It should also be possible to achieve increased recycling of the materials in group three. An alternative processing system is based on the following principles:
- Residual materials must be recycled to whatever extent is technically and economically feasible.
- Residual materials must always be kept separate until they are required for use or treatment. Material which is to be destroyed in particular must be kept separate from material which is only difficult to handle.
- Physical methods should be used as far as possible to keep organic substances separate from inorganic substances.
- The technique used for disposal on a landfill site must be of a long-term nature, must not give rise to environmental problems, and must not create the need for future supervision.
- The investments should be low.
This approach differs in three essential respects from current practice:
- Material must be under supervision from production to treatment. The possibility of material becoming mixed or going astray must be excluded.
- The waste must be handled as far as possible as a raw material in treatment processes for conversion into new products.
- Existing technology and resources must be used as far as possible.
The treatment system, which is summarized on page 5, is based largely on familiar basic technology. The various stages have been refined in order to adapt them to the special handling problems associated with residual materials. The system is under continuous development - process stages are developed, treatment methods are added, and efficiency is improved.
The knowledge from the cement industry is an important part of our concept, for two reasons. On the one hand the cement industry is the buyer of fuels which are produced in the separation process, and on the other hand it possesses skills in the field of cement chemistry which were applied in the development of our landfill system.
The cement process has proved extremely useful all over the world as a means of destroying waste which would otherwise call for special furnaces. Incineration produces no negative effects, either on the environment or on manufactured products. The objective of the cement industry is to reduce its energy costs by replacing traditional fossil fuels. The higher the proportion of substituted fuel, the higher the requirements which must be imposed.
Our technology permits the production of fuels with given quality requirements, which are no longer classified as waste. This differs fundamentally from the systems in international use, according to which the waste is simply made pumpable or is mixed with sawdust. The fuel can be tailor-made to meet the customer's specification; for example, the cement process is able to accept a higher ash level than in many other industrial processes.
The traditional approach to the treatment of environmentally hazardous waste embodies the notion of the final solution to the problem. The colossal, advanced furnace which swallows up every problem are used as an environmental alibi. Time has proved this approach to be wrong.
One example is provided by paint residue containing metallic pigments. As long as the pigment is encapsulated in the binding agent, no metals will leach out. If, on the other hand, the pigment is thrown into an incineration furnace, the metals will be mobilized. They are largely transformed into readily soluble metallic chlorides, which are driven off with the flue gas. The metals should accordingly be separated prior to incineration of the organic paint residue.
In a destruction furnace the energy balance will be upset when adding materials with a high ash content and a low organic content. This can lead to increased emissions, which cannot be calculated from the start. Such material should instead be disposed of on a landfill site in a way which does not permit leaching out that can harm the environment.
The common method of disposal on a landfill site relies on encapsulation in impervious layers of organic material such as plastic or asphalt. These make excellent sealing layers, although they are subject to ageing. We are not entirely certain how long their useful life is; they may last for 10 years, or perhaps even 20 years, although not for 50 years. We know of landfill sites of this kind containing paint waste and metal hydroxide sludge that are now experiencing increasing problems.
The principal problem associated with landfill sites is leakage. The requirements relating to the control and treatment of leachate increase whenever the landfill site is extended. This has the effect of increasing the cost for all subsequent waste. Disposal on landfill sites is thus becoming as expensive as, if not more expensive than destruction. Ageing landfill sites may become the major environmental problem by which we will all be faced in the next century, as they will have to be cleared up at the taxpayer's expense.
Our waste disposal concept aims to prevent environmentally hazardous leakage on a time scale that will extend until the next Ice Age. This will require the landfill sites to be local, accessible and controllable. The technology of future generations may include recycling solutions for the encapsulated problems.
The idea is to reconstitute the waste to a state in which it can be compared with mineral rock. These monoliths can be disposed of in the open without constituting a risk to the environment.
Sorting at source and recycling should be introduced for both domestic refuse and industrial waste.
The re-utilization of residual products represents a saving of resources on the one hand, and on the other hand a means of financial control to prevent the spread of environmentally hazardous waste.
Advanced incinerator furnaces provide poor environmental alibis. Our environmental conscience can be kept clear by sorting, recycling and Monolithic disposal. Sorting enables the proportion of waste for destruction to be reduced considerably. Recycling enables our industrial dependence of fossil fuels to decrease. Monolithic disposal has allowed us to accept our share of responsibility for future generations, and has also given them the chance to solve problems for which we do not yet have the answers.