What Is the Difference Between Hazardous Waste and Solid Waste?

Solid waste is the stuff that piles up at wastewater treatment plants and in landfills. Hazardous waste is waste that's toxic or dangerous, whether it's mercury light bulbs or poisonous industrial chemicals. Most hazardous waste is solid waste, but most solid waste is not hazardous. Hazardous and non-hazardous wastes have to be treated differently.

Solid waste doesn't have to be solid. It includes municipal solid waste -- all the garbage, trash and yard clippings we throw away -- but also sludge from waste-water treatment plants, plus air pollution and solid, liquid, semi-solid and gas wastes produced by industry, manufacturing and mining. There's very little we do that doesn't produce some sort of solid waste. Individually, we generate an average 4.4 pounds per year, according to the Environmental Protection Agency.

The EPA maintains several sub-classes of hazardous waste. Listed wastes include waste from manufacturing, industrial and commercial chemical products that the EPA has officially labeled as hazardous. Universal wastes are obviously risky items such as batteries, pesticides and products containing mercury. Characteristic waste describes items and substances that aren't officially listed, but are known to be highly flammable, poisonous or corrosive.

There are several ways to get rid of non-hazardous solid waste. In 2011, for instance, Americans recycled 87 million tons of municipal solid waste -- slightly more than a third of the total 250 million tons generated that year. Other MSW gets dumped in the trash, shipped to landfills or composted. The EPA encourages cutting municipal solid waste by source reduction -- designing products and packaging so that as little as possible has to be thrown away.

Disposing of toxic chemicals and other hazardous waste is tougher than non-hazardous waste. Businesses or governments can store it temporarily, as long as they meet EPA standards. Eventually, however, it has to be treated or disposed of by changing its physical, chemical or biological characteristics to minimize the hazard to people and the environment. The federal Resource Conservation and Recovery Act gives the EPA the authority to permit and review hazardous waste storage, treatment and disposal. Failure to follow EPA rules can lead to heavy fines.