Plasma incineration an attractive option

Posted on April 6, 2011. Filed under: Waste |

Ahmad Ibrahim
New Straits Times (Malaysia)
April 6, 2011

WASTES have become a major global issue. They not only smell but also pose serious problems for the environment. We often experience this during festive breaks when rubbish is left uncollected for days.

The smell can be nauseating, not to mention unhealthy. And it can attract all kinds of disease-spreading vermin. The disposal of untreated wastes from industries and households is also known to pollute rivers and waterways. There have been many reported cases of this.

Some wastes contain toxic components. One that has been much publicised is the mercury pollution reported some years back. It led to the infamous Minamata disease in Japan. There have also been reported cases of serious ground water contamination by heavy metals coming from wastes. Many studies have shown that the waste problem is going to worsen.

For a start, the amount of wastes generated is increasing by the day. With growing rural-urban migration, many towns and cities now have reported massive increase in household wastes. One study has shown that in Malaysia, local communities generate close to 20,000 tonnes of domestic waste per day. The amounts per capita vary from 0.45 to 1.44kg per day, depending on the economic well-being of the areas studied.

The management of municipal solid wastes (MSWM), for example, takes up much of the revenue generated by local authorities in urban areas. It has been reported that on average, 50 per cent of the municipality operating budget is spent on MSWM and of this, 70 per cent is spent on the collection of wastes. Not only that, the traditional way of disposing of wastes by simply burying them cannot go on for long as land becomes scarce. New approaches will have to be developed. And they have to be the ones that do not require much land area.

In some developed countries, incineration is widely used. This has become controversial in Malaysia as people see more negatives than positives in incineration. A major worry, as demonstrated in a recent attempt to introduce waste incineration in the Klang Valley, concerns the emission of dioxin and other health-threatening gases.

Incineration, on the other hand, is widely used in Japan, where land is a major constraint. With proper maintenance, incineration is an attractive option in waste disposal. But in Malaysia, good maintenance remains a struggle. We can see evidence of this in many public amenities where poor maintenance has changed many such projects into white elephants.

Lately, however, there has been some advancement made in waste-incineration technology. The technique involves tearing wastes into their constituent atoms using electricity. Proponents of the technology claim it is clean and might even be profitable. The technology essentially uses electric plasma torches.

These are devices that heat matter to a temperature higher than that of the sun’s surface. The torch is a pair of electrodes, usually made from a nickel-based alloy. A current between the two electrodes turns the surrounding air into plasma by stripping electrons from their parent atoms. When fed with chopped-up wastes, the intense heat and the electric charges of the plasma break the chemical bonds in the waste turning them into vapours.

The vapours contain two main gases: carbon monoxide and hydrogen. Both are potent fuels. Metals and other inorganics in wastes fall to the bottom of the reactor chamber as molten slag. The slag finds potentially wide use in building and road construction.

Plasma incineration is not new. The use of electric arcs has been around for a while now. But the early plasma torches were not noted for reliability. Thanks to research and development, things have improved significantly. For example, the quality of the nickel alloys has improved. This allows the torches to work continuously.

Furthermore, through developments in computational fluid dynamics, the rubbish going into the process can be mixed optimally to maximise the production of the gases using the least input of electricity. The latest plant to exploit this technology will be built in Florida in the United States.

Designed to be fed with wastes from local households, the plant will provide electricity for more than 20,000 homes. The project is expected to make enough money for the company to service the project loan plus an attractive profit.

The gases, apart from generating electricity, can also be fermented to produce ethanol for use in cars. In a world now gripped by the fear of global warming and environmental degradation, the new plasma technology should be a welcome change.

With the recent difficulties experienced in Japan on the dangers of nuclear power plants, such development in plasma technology should justifiably be an option which deserves serious consideration. In fact, with increased investment in R&D, there is no reason there cannot be further improvement to the technology. What better technology to have than one which not only solves the waste-management issue, but also produces clean climate-friendly energy for the world?

This is the kind of innovation that Malaysia should pursue if we are to tap into the growing world demand for green technology. And undeniably, it is only through such innovation that Malaysia can eventually reach the high income targets that the country aspires. There is no other way.

Dr Ahmad Ibrahim is science analyst at the Malaysian Industry-Government Group for High Technology and fellow, Academy of Sciences, Malaysia

( END )

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