A hazardous waste is waste that poses substantial or potential threats to public health or the environment. According to the U.S. environmental laws (see Resource Conservation and Recovery Act) hazardous wastes fall into two major categories: characteristic wastes and listed wastes. Characteristic hazardous wastes are materials that are known or tested to exhibit a hazardous trait such as:

• ignitability (i.e., flammable)
• reactivity
• corrosivity
• toxicity

Listed hazardous waste are materials specifically listed by regulatory authorities as a hazardous waste.

Many types of businesses generate hazardous waste. For example, dry cleaners, automobile repair shops, hospitals, exterminators, and photo processing centers all generate hazardous waste. Some hazardous waste generators are larger companies such as chemical manufacturers, electroplating companies, and oil refineries.

These wastes may be found in different physical states such as gaseous, liquids, or solids. Furthermore, a hazardous waste is a special type of waste because it cannot be disposed of by common means like other by-products of our everyday lives. Depending on the physical state of the waste, treatment and solidification processes might be available.

Recycling Edit

Many HHWs can be recycled into new products. Examples might include lead-acid batteries or electronic circuit boards where the heavy metals can be recovered and used in new products. A non-household example is the ash generated by coal-fired power plants; these plants produced two types of waste: fly and bottom ash. Fly ash particles have a low density, are very fine, and are removed by air pollution control devices. On the other side, bottom ash is a dense, dark, gravely substance that remains on the bottom of combustion chambers. After these types of ashes go though the proper treatment, they could bind to other pollutants and convert them into easier-to- dispose solids, or they could be used as pavement filling. Such treatments reduce the level of threat of harmful chemicals, like fly and bottom ash, while also recycling the safe product.

recycling one ton of hazardous waste could keep 1,240 pounds of hazardous metals, 41/225 tons of solvents out of landfills