WASTE DISPOSAL: A CHALLENGE FOR SOUTHERN CALIFORNIA COMMUNITIES

Rapid economic development and population growth have led to ever-increasing quantities of solid waste. Los Angeles County has an abundance of landfills that have satisfied its refuse disposal needs. However, many of these landfills have closed in recent years. Los Angeles County now faces a shortage of acceptable disposal sites in the metropolitan area.

The development of facilities for the production of energy from solid waste is one facet of the solution to this problem. Environmentally sound refuse to energy facilities, which use waste as fuel to produce power, can play a role in managing the 36,000 tons of waste disposed of every day in Los Angeles County.

Refuse-to-Energy facilities can lessen our reliance on fossil fuels and prolong remaining landfill capacity for future use. The City of Commerce and the Sanitation Districts of Los Angeles County have jointly taken the initiative to design and build the first municipal refuse-to-energy facility in Southern California.

COMMERCE REFUSE-TO-ENERGY FACILITY:
BEGINNING A NEW ERA

Planning for the Commerce Refuse-to-Energy Facility began in 1981. The original goal of the project was to demonstrate that refuse-to-energy is a viable alternative method of solid waste management in the South Coast Air Basin, where air pollution requirements are the toughest in the world. The Facility has achieved its goal, having been in successful operation since 1987.

The Commerce Facility was the first plant in the world to use a unique state of the art combination of air pollution control devices. These devices consist of ammonia and limestone injection into the furnace, followed by a dry scrubber and finishing with a baghouse. This combination of devices has earned the Commerce plant the reputation for being among the cleanest of all the plants of this type in the world.

The Commerce Facility poses no heath threat to the community. A health risk assessment prepared by an independent consultant reveals that the cancer risk for the average person living near the Facility is only 0.2 in a million. To put this into perspective, the cancer risk from drinking tap water is 100 in a million and the risk from drinking one pint of milk per day is 140 in a million.

OPERATION

The Commerce Refuse-to-Energy Facility produces power seven days a week, 24 hours per day. An average of 120 trucks per day deliver loads Monday through Friday during normal working hours. The Facility burns an average of 360 tons of trash per day and generates ten megawatts (net) of electricity for sale to the Southern California Edison Company. This is enough electricity for 20,000 Southern California homes. The facility also provides certified destruction services for classified or sensitive documents and materials. Documents such as medical or government classified records are destroyed through the burning process. The facility is approved by the Department of Defense for this service.

Sophisticated air pollution control equipment approved by the Air Quality Management District consistently maintains low emissions. Testing of the emissions is performed continuously with in-stack monitors. Let's look at the Facility operation step-by-step by following the numbers through the following schematic.

1 / Weigh Scales

Each truck must be weighed and pay a fee based upon the load weight before disposing of its load. All loads are screened by meters for radioactive materials, which if found, will be safely handled by the County Department of Health Services.

2 / Refuse Storage Pit

After weigh-in, the trucks discharge their loads into the refuse storage pit. The storage pit has a 1,200 ton capacity, enough to run the Facility for three to four days. Some loads are pulled aside on an unannounced basis and checked for hazardous wastes each day. All loads are scanned for large pieces of ferrous metal which are removed and recycled. The crane operator scoops up 3,000 pound loads of refuse and delivers them the furnace feed chute. The entire storage pit area is enclosed and air is continuously drawn into the refuse storage building to eliminate the escape of odors or dust. This air is then used for burning of the refuse. Odors are destroyed by the high temperatures in the furnace. Four carbon filters are used for odor control at times when the furnace is shut down for maintenance.

3 / Furnace & Boiler

After the refuse reaches the bottom of the feed chute, hydraulic rams push it into the burning area. The floor of the furnace contains moving grates that push the burning refuse through the furnace and ensure complete combustion. The ash falls from the end of the grates and is quenched with water. The hot gases of combustion rise through the furnace as they travel to the boiler. The walls of the furnace contain steel pipes carrying water that begins to heat as the gases pass over the pipes. Ammonia is injected into the furnace to remove oxides of nitrogen. Limestone is also added to aid in acid gas removal. As the hot gases enter the boiler, the hot water contained in the boiler tubing is converted to high pressure and temperature steam.

4 / Turbine-Generator

The Steam leaving the boiler enters a steam turbine. The high pressure steam causes the turbine blades to turn at high speed. The turbine is coupled to a generator that produces 11.5 megawatts of power. One and a half megawatts of this power is used to run the plant leaving 10 megawatts to be sold to Southern California Edison. The revenue from the sale of power helps to retire the bonds that were sold to build the Facility. 5 / Dry Scrubber

After leaving the boiler, the hot combustion gases travel through the beginning of the sophisticated air pollution control system. The dry scrubber removes acid gases such as sulfur dioxide and hydrochloric acid. These are by-products of the refuse combustion. Lime slurry is sprayed into the exhaust stream to convert the acid gases to a solid which is removed downstream in the baghouse. In excess of 95 percent of the sulfur dioxide and hydrochloric acid are removed in this process.

6 / Baghouse

The baghouse operates like a gigantic vacuum cleaner. As the air is drawn through the baghouse, particulate matter and fly ash are left on the inside of the bags and the air is allowed to travel through. The baghouse contains eight modules with bags made of fiberglass. The modules are cleaned by blowing air, in the reverse direction, through the bags. The particles and fly ash are removed through the bottom. This process removes 99.5 percent of the particulate matter in the airstream down to sub-microscopic levels, eliminating any visible plume. After leaving the baghouse, the cleaned exhaust gases exit through a 150 foot stack. Monitoring devices incorporated into the stack continuously monitor the air for oxides of nitrogen, sulfur dioxides and carbon monoxide.

7 / Ash Treatment and Recycling

The ash exiting the refuse-to-energy plant makes up approximately 30% of the total weight of the incoming refuse. The bottom ash is screened and metals are removed for recycling. The screened bottom ash and fly ash are mixed with cement to make concrete which is then used at the landfill as road base. Ninety nine percent by weight of the incoming refuse is recycled as metals, energy or roadbase.

THE COMMERCE EXPERIENCE: A DOCUMENTED SUCCESS

The Commerce Refuse-to-Energy Facility has established itself as one of the best refuse-to-energy plants in the world, having produced some of the lowest emissions on record and operating an innovative ash reuse system. The system has won four national awards:

• Environmental Protection Award from "Power" magazine
• Award of Excellence from the Solid Waste Association of North America (SWANA)
• Grand Prize for Operation/Management from the American Academy of Environmental Engineers
• Facility Recognition Award from the American Society of Mechanical Engineers

Since the beginning of operation in 1987, the Commerce Refuse-to-Energy Facility has continuously generated enough electricity for 20,000 homes.

More than 4,000 people have toured the plant, including visitors from almost every state in the United States plus countries such as Japan, Finland, Canada, Denmark, New Zealand, Taiwan, China, Sweden, the Philippines, Korea, Costa Rica, Mexico, Russia, Germany, England, and Italy.

Looking Toward a Regional Solution to Disposal ProblemsSociety can not completely eliminate the generation of wastes. As long as there are people and industry, wastes will be created and require disposal. While we can't make the waste disappear, we can create an environmentally safe and cost-effective integrated solid waste management system incorporating refuse-to-energy, recycling, composting, materials recovery and state of the art sanitary landfilling. State Law requires cities and counties to divert up to 50 percent of the waste stream from landfills by the year 2000. Refuse-to-energy can create electrical power and help to fulfill the 50 percent diversion requirement. This integrated approach is the future for waste management in Los Angeles County.