A Burning Question
Do Municipal Incinerators Create More Problems Than They Solve?
Municipal incineration is a means to removing unwanted waste and is an alternative to landfills but are they an environmentally sound one? Incinerators are a means to converting nontoxic, toxic and medical waste in to energy for human use. Most incinerators are municipal and must remain profitable. Thus such incinerators must burn waste at the lowest temperature possible in order to have optimal efficiency. If the furnace of a municipal incinerator burns too hot for too long, then the facility will be losing money. The entire point of a municipal incinerator is not just to burn waste, but to burn it profitably.
So what is the problem with burning waste at a minimal temperature? Toxic substances such as dioxins can actually be created from chlorides present in waste at low burning temperatures. Dioxins some of the most dangerous chemical compounds known to man. To put the toxicity of dioxins in to perspective: The maximum concentration of lead allowed in residential soil before it is considered contaminated has been set to 150 parts per million whereas the most toxic dioxin substance (called TCDD) allowed in residential soil before it is considered contaminated has been set to 4.6 parts per trillion.
Dioxins can be destroyed if burned at 600 degrees Celsius for at least 3 seconds, but municipal incinerators rarely operate at this temperature. Many municipal incinerators operate at approximately 300 degrees Celsius; at this temperature dioxins are actually created as a waste byproduct due to incomplete combustion (if oxygen and chlorides are present). Incomplete combustion within the furnace of a municipal incinerator can also create other environmental contaminants but none as toxic as dioxins. Municipal incinerators also emit other environmental contaminants such as heavy metals, Volatile Organic Compounds (VOCs), and Persistant Organic Pollutants (POPs) from the waste they burn. The concept of incineration is persuasive; refuse shall be destroyed via combustion and used the energy as a power source, but in order for a net energy gain to occur some pollutants must be released in to the environment as it is unprofitable to burn the most fire resistant.
Ash is the solid waste that is generated from municipal incinerators. Municipal incinerator ash can be sold as a soil amendment for acidic soils. Municipal incinerators do not always have lumber by-product and agricultural waste in supply and thus some have turned to alternative sources. In some US states (as in California), up to 30% of municipal incinerator fuel mass can be urban wood waste such as demolished homes. Up to 3% of this urban wood waste can be be non-wood waste such as nails, carpet, chemicals, etc. Sometimes municipal incinerator ash is toxic waste, sometimes it is not. In the United States incinerator ash defined as "toxic" must be sent to a hazardous waste landfill, but sometimes the regulatory lines for "what is toxic" can be unclear and varies from state to state. No farmer wants to find out that the soil amendment they spread on the top soil of their orchard has dangerous levels of arsenic in it.
Indeed modern emission control technology removes the vast majority of toxic substances that are present in municipal waste but is the leftover pollution acceptable to public health and the environment? Dioxins, heavy metals and other contaminants emitted from municipal incinerators will fall back to earth and many of these substances are contaminants of soil, groundwater and the food chain. The European Union has set the maximum level of dioxins allowed in eggs at 3 parts per trillion due to public outcry over dioxin contamination of European food supplies. Municipal incinerators should operate at a higher minimum temperature in order to protect the public and environment from soil, groundwater and food chain contaminants produced by such facilities.