Reliable IR Gas Sensors Helping to Lower the Costs for Product Development

The gases arising in decomposition processes in landfill sites contribute to the greenhouse effect and also present a substantial health hazard. On the other hand they are often rich in methane and therefore a potential energy source. In China there is still

considerable potential for generating electricity and heat from landfill gas. An opportunity to find out in detail about the current situation and future trends in the Chinese waste-disposal industry is coming up at the environmental trade fair IFAT CHINA 2008.

Between 23 and 25 September international technology suppliers, service providers and investors will be coming together with experts and decision makers from the Chinese environmental sector at this event in Shanghai.

According to the United Nations each year 148 million tons of waste ends up each year in hundreds of landfill sites around China. And, as

everywhere else in the world, here, too, these dumps give off considerable quantities of methane and carbon dioxide, generated by the bacteriological and chemical decomposition of the organic content

of the waste. Over the years each ton of household waste can therefore generate 150 to 250 cubicmeters of landfill gas.

Without technology landfill gas would pose a considerable danger. The methane contained in it can combine with the oxygen in the air to create a combustible, in some cases even explosive mix. If the

carbon dioxide collects in shafts or channels at concentrations of over nine percent people in those areas can suffocate. Also, the bad-smelling gases from these dumps contain many trace elements, for

example sulfur compounds, that are damaging to health even in low concentrations.

As well as these dangers posed to human health, untreated gas escaping from landfill sites in an uncontrolled manner also has an impact on the

climate. Methane is regarded as one of the substances causing the destruction of the ozone layer; it is 20 times more powerful in its contribution to the greenhouse effect than carbon dioxide. By treating

the gases thermally, i.e. burning off, the negative effects of these gases can be reduced. A more elegant solution, however, is to exploit the energy content of the landfill gases to generate electricity

and heat. The heating value of 2.5 cubic meters of landfill gas is equivalent to that of around one liter of heating oil.

International emissions trading is making it more attractive to exploit landfill gas: the reduction in greenhouse gases that can be achieved by

generating energy from these gases now has an economic value. The key term here is CDM, or clean development mechanism. This instrument, agreed at the international climate conference in Kyoto, enables industrialized and developing countries to carry out climate-protection projects together in developing countries. Basically the system involves

working out how much gaseous emissions are produced by a power station, factory or landfill site, for example, then establishing howmuch greenhouse gas would be saved if the landfill gas were exploited

to generate heat and electricity. A company from an industrialized country then invests in and finances the landfill gas power station and receives certificates for the reduction in greenhouse gases achieved.

With these the investor can eithermeet the obligations of its own company at home to reduce a corresponding amount of greenhouse gases, or sell the certificates to other companies in emissions trading. The aim of the tool is to prevent as many harmful emissions as possible, at as low a cost as possible. And at the same time to help emerging and

developing countries to acquire the new technology that they themselves would not be able to afford.

So far in China such landfill-gas projects are rare.

Currently there are 680 landfill sites in China which have the minimum required system of passive degassing, i.e. by means of gas wells or collector pipes. By contrast there are only 20 CDM landfill-gas

projects with active gas collection and low pressure“ eight of them are already in operation, three under construction and nine on the drawing board, said Heinz-Peter Mang. This German expert, supported by the Centrum fur Internationale Migration und Entwicklung (CIM), works as an advisor on bio-energy and sustainable sanitary management at the

University of Science and Technology in Beijing.

In summer last year the World Bank also signed its first agreement on reducing greenhouse gas in China, in the form of a landfill-gas project. The gas comes from the Shuangkou dump in Chinas port of Tianjin.

Each day between 800 and 1000 tons of waste are deposited at this modern site.

The Tianjin Clean Energy and Environmental Engineering Company Ltd TCEE) will collect the landfill gas arising here via a pipe network and direct it to a centralized power station where it will be burned. The electricity generated here will be fed into the northern Chinese grid. TCEE will sell the equivalent of 635,000 tons of carbon dioxide each year to the Spanish Carbon Fund managed by the World Bank.

Biogas expert Heinz-Peter Mang sees landfill-gas projects as a good opportunity for China to introduce clean technologies and pursue sustainable options in waste-management and energy generation:

“The sale of emissions certificates is an important, additional financing tool, but only in a very few areas can CDM projects be profitably organized using these measures alone. When it comes to exploiting landfill gas, however, its different. In view of the relatively low investment input, projects here can indeed be

profitable solely via the sale of emissions certificates.”

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