Note: The fact is that waste-to-energy incinerators are responsible for distortion of waste management. It is hazardous to public health. The need for landfill remains. What happens to the fly ash and bottom ash? waste-to-energy incinerators create landfill in the sky.
ToxicsWatch Alliance (TWA)
With waste-to-energy, landfill search ends
NEW DELHI: In 1999, Singapore was sending 0.76 million tonnes of waste to its landfill site in a year and incinerating 2.04 million tonnes. In 2011, only 0.2 million tonnes was sent to the site while 2.66 million tonnes was sent for incineration to its four waste-to-energy (WTE) plants. The plants process around 7,600 tonnes of waste daily and produce more than 40 MW of power.
Sources in Singapore's National Environment Agency (NEA) explained that "the four WTE plants incinerate waste by 90%. What remains is disposed of safely at the landfill site. Waste management becomes easier because about 50% of all waste produced is recycled."
Delhi, with three overflowing landfill sites, a growing population and a miserable waste management strategy has been growing desperate for a solution to its waste problem. With 8,500 tonnes of waste reaching its landfill sites daily, the government at one point contemplated creating a fourth landfill site in the middle of the city's ridge area.
In 1990, after a failed attempt at incinerating its waste, the city tried to set up another WTE plant. Mired in controversy and dogged by protests, the plant did come up but the government is still to convince Delhiites that it is the best solution to the waste problem. Meanwhile, two other WTE plants are being constructed. The three plants together will incinerate 7,500 tonnes of waste each day.
Delhi's problem with WTE technology started with the Timarpur plant that was set up in 1990. It shut down seven days after operations commenced as the government realized that Delhi's waste did not have the calorific value to function well with the Danish technology.
"Since Indian waste is never segregated, it is wet and often mixed with hazardous material. This waste does not burn well at all. Similar plants set up in other Indian cities also failed. Jindal Ecopolis, which is operating the new plant in Okhla, claims to be using better technology but the waste is the same. How can the plant be successful then," asks Gopal Krishna of the ToxicsWatch Alliance.
Singapore's four WTE plants are Tuas, Senoko, Tuas South and Keppel Seghers Tuas Waste-To-Energy Plant (KSTP). KSTP was developed under a design, build, own and operate model and was commissioned in 2009 to replace the city's first WTE plant at Ulu Pandan which was closed in August 2009 after 30 years of operation.
"Prior to the collection of solid waste, recyclables are sorted out and retrieved for processing to prolong their lifespans," says an NEA report.
"The solid waste that remains is then collected and sent to the various waste-to-energy plants for incineration. Incineration reduces the volume of solid waste by about 90% and produces steam that runs turbine generators to generate electricity. The incinerated ash and other non-incinerable wastes are then transported to the Tuas Marine Transfer Station (TMTS) and then to Semakau Landfill."
"Licensed collection vehicles deliver incinerable solid waste to the plants. To prevent odours from escaping into the environment, the air in the refuse bunker is kept below atmospheric pressure. High-capacity rotary crushers reduce the size of bulky solid waste to improve its burning efficiency. The solid waste is then fed into the incinerator by a grab crane. As the incinerator is heated to temperatures of between 800 and 1,000 degrees Celsius, a lining of silicon carbide tiles protects the incinerator walls from the extreme heat and corrosion. Each load of solid waste is reduced to about 10% of its original volume in about five hours," says NEA.
Catalytic fabric filter systems and two-zone electrostatic precipitators remove pollutants from the flue gas before it is released from the plant while ash is collected and the ferrous material is removed to be sold and recycled.
Ranjit Devraj, who has been an active member of protests against the Okhla WTE plant, says the biggest drawback for the technology in India is that waste is not segregated.
"The Okhla plant is in the middle of a residential area. Not only were residents not consulted, the technology being used is also suspect. If waste is not segregated, the plant will be burning everything, from plastic to chemicals. For 16 MW of power, it is too high a price to pay. Singapore is using the best technology possible but Delhi government has not managed to convince us of the benefits of this plant. Even the Central Pollution Control Board has questioned the technology being used in this," he said.
Jul 11, 2012
The Times of India