Generating Energy from Waste

A power plan  that burns garbage to generate electricity in Fujian, Sep. 4, 2007. [Xinhua]

So what happens to Beijing's unsorted garbage? First it is transported to dumping stations where it is sorted by workers, before going on to rubbish transfer centers where it is sorted into further categories by machines. Fans are used to extract plastic bags, magnets pull out scrap metal, and sieves of different sizes separate out organic waste to be taken to fertilizing plants. The inorganic waste left at the end of this process is taken away to be buried or burnt.

With an massive national annual garbage mountain of 160 million tons, burying is still the most common means of garbage disposal in China. However, as land prices increase, the cost of burying rubbish is also rising. The burning of garbage has thus become more common.

According to Guo Weidong from the Beijing Municipal Administration Commission, five garbage treatment projects were built in Beijing in the mid-1990s with a total investment of over RMB 600 million, which included capital obtained through World Bank loans, and capital and equipment provided by Germany. By the end of 2007, there were 23 refuse treatment facilities in Beijing, including six garbage transfer centers, four integrated garbage treatment plants, and 13 garbage burying sites, with a total daily treatment capacity of 10,350 tons. A comprehensive garbage treatment system has been established in the capital, with the portion of domestic garbage being treated increasing from 93.8 percent in 2004 to 99 percent in 2007. In Beijing's suburbs, the rates have gone from 33.3 percent to 76 percent over the same period.

The Beijing Asuwei Integrated Garbage Treatment Center is a typical set-up, that includes four main operations: garbage burying, the creation of fertilizer, burning and power generation, and methane power generation. The methane power project was completed and began formal operation in May 2007, using the world-class Deutz methane power-generating sets. The project provides power for 17,000 families annually, reducing coal consumption by some 10,000 tons.

Prior to the introduction of this methane power-generating technology, marsh gas from buried garbage was a big environmental headache for Beijing authorities. The greenhouse effect of this gas is 21 times that of carbon dioxide, and it can set off explosions, cause fires and trigger landslides at garbage dumps if not properly handled. Before the gas was harnessed for power generation, it was simply burned, causing air pollution and creating large amounts of carbon dioxide. The power-generating plant is now listed as a greenhouse control project under the Kyoto Protocol.

Another problem with burying garbage is seeping liquids. This is mainly organic wastewater with a complicated composition, potentially of great harm to the environment and human health. The Nanjing University Pollution Control and Resource Utilization Research Laboratory has developed seeping liquid filtering and treatment technology, which helps remove organic content. In the Asuwei Integrated Garbage Treatment Center, treated seeping liquids are used to water flowers.

These varied technologies are helping to reduce China's pressing garbage disposal problem, and recycling precious resources sorely needed to feed the nation's booming economy.

(China Today September 23, 2008)