Plasma gasification is not just a technique that helps manage municipal waste through vaporization. It is a technique that could supply our homes with electricity and help us reduce greenhouse gas emissions.
The world’s tallest peak, Mount Everest, has earned itself another title: the world’s highest garbage dump. With over 40,000 visitors frequenting Everest from the Nepal side alone, 600 tons of trash has been strewn on the jagged landscape. Now, the peak stands testimony to the waste problem that the world as a whole faces.
In 2008, the municipal solid waste generated per person across developed and developing countries is estimated at around 880 lbs. per year. In the same year China, the world’s second largest economy, generated more than 250 million tons of municipal solid waste, surpassing the US. It has become glaringly apparent that the unprecedented growth in consumption and trash are now challenging the ways in which the world manages its waste.
Historically, countries across the world have managed trash by dumping it in landfills, recycling a part of it, and incinerating the rest. Although recycling could be the most effective way to manage waste, typically only 30% of all the materials from municipal waste qualify to go through the process. The remaining 70% of trash decomposes slowly in landfills giving rise to greenhouse gases such as methane and other toxic wastes. In the US, the 135 million tons of trash dumped in landfills accounts for 40% of the methane generated in the country. Furthermore, as landfills get dearer due to dwindling supply, the costs associated with dumping trash in them will be gradually going up. Currently, dumping a ton of trash in the US costs anything between $40 and $50, on average. All these problems necessitate new waste management technologies that are both economical and environment friendly.
One of the technologies that could help manage waste is plasma gasification. Plasma gasification involves subjecting trash to such high temperatures that the atoms in the trash are split and reduced to their most basic elements. Although the technique has been available over the past few decades, its application was largely limited to wastes such as sludge from the oil industry that is more difficult to treat than municipal waste. The relatively high cost of plasma gasification had inhibited its widespread use. But with the cost of landfills rising, plasma gasification could be given a second look.
The plasma gasification technique involves a special kind of torch, with a core that holds a pair of electrodes. When the torch is charged, electric current arcs between the pair of electrodes, producing a temperature of around 25,000 degree Fahrenheit, almost three times that found on the surface of the sun. At such high temperatures the waste practically vaporizes, producing a desirable by-product called syngas, which has large industrial applications. To put this in perspective, ordinary incineration is carried out at around 1400 degrees Fahrenheit, often by supplying external energy, and waste is not completely burnt, leaving behind 30% ash. Ordinary incineration also results in the emission of large amounts of carbon dioxide, sulfur dioxide, methane and other nitrous compounds. These factors make plasma gasification a more attractive alternative waste treatment method.
Plasma gasification, which converts trash to vapor while generating
a useful industrial by-product called syngas, not only reduces the
cost of managing waste but also eliminates the harmful gases
associated with other waste treatments.
Another major advantage of the gasification technique is its ability to sustain the process without external energy. Startech Environmental Corporation, which designs and markets plasma gasification units, has designed a plant that requires power only to get started. Once the unit starts to vaporize the waste, syngas is produced instantaneously. The syngas produces more than the heat required to run the plant and obviates the need for power. What’s more? The syngas produced while vaporizing waste is usually more than what is required to run the plant. Nearly a fourth of the syngas could be sold back to the utility. Startech claims that it can manage waste for $15 a ton, compared to the steep price of $90 per ton that New York pays landfills to get rid of trash.
However, one of the biggest problems associated with plasma gasification is the capital expenditure. The gasification units designed by Startech, which are capable of handling 2,000 tons of trash, cost a whopping $250 million. Even Startech admits that companies that buy its gasification equipment would take over six to eight years to recover their initial investment.
But a number of other factors are favoring gasification over landfills and incineration. SRL Plasma, an Australian firm, has made substantial improvement in the nickel alloy used to make plasma torches. Another gasification company Geoplasma, which is planning to build a $120 million gasification plant, is more optimistic about recovering initial costs within a year. The company says this will mainly be possible by supplying 20,000 homes with electricity produced from syngas. Even the US government seems to be supporting plasma gasification. Currently, gasification plants are eligible for tax credits under the Renewable Energy Production Incentive (REPI).
One sign of surging demand for gasification plants is evident from the huge demand for the plasma torches. Westinghouse Plasma Corporation, based in Pennsylvania, which sells and rents plasma torches, says its torches command a rental rate of $150,000-$175,000 per day. With a number of petrochemical plants showing increased interest in the technology in China and India, the process will only gain in popularity.
So, the humble dust bin that accumulates through the day shall be viewed as an energy pot henceforth. And in the wake of the Japan nuclear disaster, which has cast doubts over the reliability of nuclear power, another energy source may be just what we need.