INTERNATIONAL: Asian Pellet Plants May Help Control Excess Trash

Adrienne Redd

As the standard of living in Asian countries such as India improves, solid waste concerns prevail. For example, Indians are beginning to consume more western-style packaging, but lack the proper infrastructure to process and dispose of it.

"A richer world will grow richer in garbage too," said the managers of a new pelletization plant.

To address this growing problem, the Department of Science and Technology (DST), New Delhi, India, has developed a garbage processing plant for producing fuel pellets in Deonar, Bombay.

In addition, India has two other privately run fuel pellet facilities in the cities of Bangalore and Baroda. On the west coast and often compared with Los Angeles, Bombay is India's largest city and commercial capital, with a population of 10 million.

The city produces approximately 4,500 metric tons of municipal solid waste (MSW) per day, most of which is currently disposed in unlined landfills, posing potential health hazards.

In 1989, the DST initiated an integrated waste management program which included opening the Deonar plant in late 1993. The facility was engineered and executed by the Technology Applications Group CMC Ltd., Bangalore, India.

The DST chose pelletization rather than incineration and power generation, anaerobic digestion and composting because the pellets' energy content is close to that of coal and can be substituted in local industry.

Indigenous technology also was available and a small plant could be economically viable. In addition, it was possible to treat the raw municipal solid waste (MSW) in a decentralized way. Finally, markets existed for the end product making the factory's profitability high.

As a pilot, the facility is intended to resolve any logistical impediments so that pelletizing technology can be used throughout India.

The plant's operation is relatively simple. Before processing, the MSW is sundried for one to two hours to lower its moisture content from 55-65 percent to 35 percent. MSW is then spread out on pavement to be dried while large items and undesirable objects are manually removed.

To avoid harming the equipment, screens separate sand and grit, which later can be used for gardening. A ballistic separator then removes dense noncombustibles such as stones and glass.

The materials are further dried with a hot air rotary drying system reducing moisture content to 10-12 percent. Next, a size reduction unit grinds the lighter combustible fraction containing biomass, paper, plastics, rags and clothes to produce a consistent particle size of 10 to 15 millimeters. Finally, industrial waste can be added to densify and bind the pellets and to increase caloric value.

At present, the plant operates three shifts, 20 hours daily. It was designed to produce fuel pellets in two parallel streams. One stream is currently operating, producing 1.5 metric tons per hour. The sale of the pellets covers slightly less than the plant's operating cost, interest and depreciation.

The DST intends to invest approximately $16,000 to add the second stream, making the plant profitable. At that time the plant will produce 80 tons of fuel pellets per day, which can be sold for $32 per ton. Currently, the cost to produce one metric ton of pellets is nearly $25.

The DST's capital investment in the plant was $742,000. Several private entrepreneurs and agencies have expressed an interest in taking over the pilot plant.

In the United States, citizens' concerns with health, odors and aesthetics are a major obstacle to any facility that processes raw municipal solid waste.

Only about 60 pelletization plants exist in the U.S., according to the 1995 survey by the Pellet Fuel Institute at the University of Minnesota.

U.S. pellet plants process either municipal solid waste or non-MSW, which industrial facilities use in their own boilers. The American process differs slightly from the Indian operation (see diagram).

MSW pellets can be burned in a 30 percent blend without specific regulation, according to the amended federal Clean Air Act.

In contrast, Indians often struggling with poverty, are more willing to tolerate the odors which come with a waste processing facility, knowing that they bring jobs and perhaps greater prosperity. Also, India has a hotter and, in the desert region, a much more arid climate. This is conducive to the drying process necessary for a well- run fuel pelletizing plant.

On the other hand, the plant in Bombay only operates 250 days per year, stopping during the heavy rainy season or monsoons.

The DST is very hopeful about the potential of fuel pelletization, according to Pawn Sikka, the department's head.