Q: How do modern landfills protect the environment?

A: The purpose of solid waste management is to remove wastes from living areas in a way that protects human health and the environment. By sealing in wastes, well-designed and well-managed landfills control odors, vermin attraction, litter, gaseous emissions, and water pollution. A modern landfill, referred to as a “Title D” landfill as referenced in the Resource Conservation and Recovery Act (RCRA) must be sited to protect environmentally sensitive areas, designed and constructed and operated to reduce and eliminate effluent leakage, odors and gaseous emissions, litter, and vermin. The landfill must be closed properly and monitored. A Title D landfill for municipal solid waste is a cold, dry, airless storage facility that is not designed for any but incidental biodegradation.

Solid waste management facilities that promote biodegradation include composting and bioreactor landfills. The latter are intended to produce saleable methane. Uncontrolled biodegradation could result in production of leachate that, if leaked, would endanger nearby groundwater supplies, lakes and streams. Title D landfills include heavy-gauge plastic liners, required by the EPA, that help protect the groundwater from contamination1.

Construction and demolition debris, including broken concrete, asphalt, shingles, metals, some plastic, and broken wood, may be placed in a special “C&D” landfill. C&D landfills are for materials that do not produce leachate and do not pose risks to groundwater or attract vermin or generate obnoxious odors.

Q: Can degradable plastics contribute to solid waste management?

A: Because modern landfills are designed, built, and managed to limit degradation, degradable materials of any type are not likely to degrade and reduce the volume of landfill required to hold them. Bacteria and fungi convert carbonaceous material, such as paper and food, to carbon dioxide, methane, and water. Biological degradation is either aerobic, meaning air is required and the gaseous product is primarily carbon dioxide, or anaerobic, meaning air is excluded and the gaseous product is primarily methane. Material placed in Title D landfills have periods of aerobic and anaerobic digestion with the generation of landfill gas that is roughly 50:50 methane can carbon dioxide plus about 1% other gases. If the methane is separated from the rest, that methane can be sold as natural gas.

In 2005 7% of disposed solid waste was yard waste. 19.9 million tons, was composted. In addition, 0.4 million tons of food waste was composted. In total, 8.4% of US municipal solid waste was composted in 20052. This does not include backyard composting. In areas where composting is a municipal solid waste disposal option and water is available to promote degradation, compostable plastics can effectively be included in the compostable material. Such compostable material includes wastewater biosolids, manure, yard trimmings, and food waste.

Biodegradable plastics that meet ASTM D6400-99 (American Society for Testing and Materials) (or European Standardization Committee (CEN) EN13432 or International Standards Organization (ISO) ISO 14855) provisions for compostability are considered “compostable plastics”. This means the plastic will rapidly disintegrate in standard industrial composting facilities to compost indistinguishable from compost from other sources at normal processing schedules. Municipal solid waste composting facilities for foodstuffs require special conditions of temperature and humidity not achieved in backyard compost piles. Compostable plastics require the more rigorous conditions of the municipal composting facilities to degrade. It is important to note that not all plastics derived from plant sources are compostable. In the United States, be sure to look for ASTM certification by the Biodegradable Products Institute http://www.bpiworld.org/.

Flushable, biodegradable diapers and personal hygiene products are readily treated in a regulated wastewater and sewage treatment facility, reducing the impact on other disposal systems.

Degradable or compostable plastics can make a positive contribution to solid waste management. Compostable yard waste bags enhance the value of composted trimmings. Compostable dinnerware allow for efficient composting of restaurant food and cutlery waste. But, degradable plastics do not excuse littering. The degradable plastics generally require intentional solid waste composting facilities to disintegrate. Degradable plastics left on the ground or dropped into waterways and oceans do not “disappear” and do not excuse poor behavior. Degradable plastics are also an issue for recycling of recyclable plastics. Recycled plastics are expected to perform without degraded properties in their subsequent lives. If degradable plastics are mistakenly placed into the recycling stream, the recycled plastics no longer are assured of high quality performance. Once again, proper human behavior can prevent problems. Similarly, recyclable plastics should not be placed with compostable plastics.

Q: Are we running out of safe places to put landfills?

A: In the 1980s, there was a perceived crisis over a lack of landfill space that led to the presumption that America would soon run out of room for its garbage. Images of garbage barges floating up and down our coasts were ingrained into our minds. Even today there are those who believe that America still has a waste "crisis." Yet, the threat of running out of landfill space simply does not exist, and never did. While it is true that there were some localized landfill shortages in the 1980s, particularly in densely populated areas, a shortage never occurred nationwide. While the total number of landfills has decreased over the years, total landfill capacity has increased3 due to construction of larger landfills. Three cartage companies, Waste Management, Allied Waste, and Republic Services collect more than half the nation's trash. According to the New York Times, rather than running out of landfill space, they have sufficient capacity to operate for decades assuming no further expansion of existing sites, no additional sites and no benefit from improved technology. James Thompson with Chartwell Information, publishers of Solid Waste Digest, said the nation has 6.561 billion tons of landfill capacity4. At current rates, this equals 49 years of capacity.

According to a 2005 U.S. EPA report, “Municipal Solid Waste in the United States, 2005 Facts and Figures”, waste disposal has actually declined since 1990. This can be attributed again to the renewed emphasis placed on curbside recycling, the addition of compost programs into communities and the pursuit of source reduction. Between 1990 and 2005, these efforts were responsible for a decrease in waste landfilled, from 142 million tons in 1990 to 133 million tons in 2005. The tonnage landfilled in 2005, 133 million tons, was actually less than landfilled in 1980, 134 million tons. At the same time, the population increased from 227 million in 1980 to 296 million persons in 2005. National recovery levels reached 32.1 percent in 2005 and municipal solid waste landfilled declined from 88.6 percent of all MSW in 1980 to 54.3 percent in 2005.

Environmentally compatible long-term landfilling will continue to evolve with scientific research, technology development, and improved construction and operation. With these safeguards in place, the disposal of plastics will continue to be problem-free.

1 MSW Landfill Criteria Technical Manual, USEPA, 1993
2 Municipal Solid Waste in the United States 2005 Facts and Figures, USEPA, 2005
3 New York Times, August 12, 2005, “Waste Yes, Want Not; Rumors of a Shortage of Dump Space Were Greatly Exaggerated”
4 Environmental Industry Summit 2004, March 10 - 12, 2004, Coronado Island Marriott Resort, San Diego, California


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