We are all going to have to understand a bit more about "Technologies", the new PR buzzword used to cover a multitude of sins.There are certainly many varied approaches some more profitable than others....but you are never going to compost plastics or tyres or tarmac or asbebestos or electricals or pesticides.So here goes..with all credits to the British Society of Ecological Medicine
The Problem of Ash
The incineration of waste produces a large amount of ash, amounting to 30% of the weight of the original waste; 40-50% of the volume of compacted waste. This is important as landfill sites are becoming less and less available so there is an urgent need for a workable alternative. It is clear that incineration will not solve the landfill problem since it can only reduce the bulk by just under half. Little thought has been given to this and incinerator operators are still being given 20 to 30 year contracts creating problems for the future.
Incinerators produce two types of ash, bottom ash and fly ash, sometimes called air pollution control (APC) residues. The latter is highly toxic and listed as an absolute hazardous substance in the European Waste Catalogue. It has high concentration of heavy metals and dioxins. Many substances such as metals have little toxicity before incineration but become hazardous once converted to particulates or fine particles in the ash. In fact, the combination of pollutants in the fly ash can amplify the toxicity. Using a biological test, researchers found that the toxicity in fly ash was five times greater than could be accounted for by the content of dioxins, furans and PCBs303.Fugitive ash is the stuff that leaks out of the holes, and is a local problem.
There is a basic problem with modern incinerators. The less air pollution produced, the more toxic the ash. Early incinerators emitted large volumes of dioxins. These emissions have been significantly reduced, but at the cost of a corresponding increase in the fly ash, with similar increases in heavy metals and other toxic chemicals. An incinerator burning 400,000 tonnes of waste annually for its 25 years of operation would produce approximately half a million tonnes of highly toxic fly ash3. Apart from vitrification, no adequate method of disposing of fly ash has been found. The EU Commission have stated that leaching from landfill sites may be one of the most important sources of dioxins in the future. Heavy metals are known to have high leachability. The US Environmental Protection Agency considers that all landfills eventually leach through their liners. Most of the pollutants are very long lasting indeed and bioaccumulate.
Advanced Thermal Technologies (ATT) and Plasma Gasification
In contrast with non-thermal methods, any thermal method of dealing with waste carries an inherent risk of causing fatalities. Because of this thermal methods should only be used for residual waste after full separation of recyclables has taken place. If thermal methods are used, these should always be the safest ones available. In effect this means plasma gasification or gasification using the Thermoselect process. Japan has more experience of incineration than any other country and has started to use plasma gasification as a safer alternative to incineration. Plasma gasification is also in use in Canada.
Plasma gasification achieves the final objective by disposing of the residual waste after separation and recycling and other separating technologies such as mechanical-biological treatment. It can deal safely with the most hazardous types of waste and can produce up to three times as much energy as incineration.
Gasification has been employed by the natural gas industry for over 80 years but has not, so far, been used extensively for dealing with waste, although such plants are now in operation in Italy, Switzerland, Germany and Japan. Gasification produces high temperatures and can thermally decompose complex and hazardous organic molecules into gases and benign simple substances. Plasma refers to the gas when it has become ionized and this happens when an electric current is passed through the gas. A very important distinction from incineration is that it does not produce ash. The gas cleaning process can convert many contaminants into environmentally benign and useful by-products. The abatement equipment of incinerators and gasification units is very different. If the abatement equipment in an incinerator fails, as is all too common, people downwind from the installation will be subjected to dangerous pollution. If the abatement equipment in a gasification unit fails it will cause serious damage to the plant itself – so the plant has to be built to a much higher quality.
In a plasma gasification plant, the residual toxic substances including metals become encapsulated in silicate which is like being encased in stone. The plant will remove the toxic and persistent compounds from plastics and other chemicals and reform them. A good quality plasma gasification unit will not produce any adverse residues or by-products, only synthesis gas, silica, sulphur and salt. Synthesis gas is a useful by-product which can be used as a fuel; ─ a major financial advantage which allows the capital costs of the unit to be paid within a 7 year period. Although it is a relatively expensive process, it is far cheaper than incineration once the health costs are taken into account . Note also that it would not incur costs under the European Union Emissions Trading Scheme, potentially saving millions of pounds annually. A recent review of plasma gasification considered it to be a promising alternative to older technologies