Waste Management Techniques
Prevention of waste is at the top of the list as far as waste management techniques are concerned, but as this is humanly impossible for us humans with the lifestyles that we are used to, the next best is the recycling and reuse of materials. While this may not yet be very prevalent in developed countries, many developing countries practice this method because of the economics of recycling and reuse which gives incomes to the underprivileged strata of people in the business.
Incineration with recovery of energy is considered the best method of waste management and ranks over plain incineration and landfill. Landfills are the most commonly practiced form of waste management, but the huge requirements of land and the fact that such landfill adds to pollution of groundwater and air by the formation of leachates and gases have made city managers wary of this method. Even with incineration, some quantity of waste is produced but this is reduced to just 10 percent of the original waste.
Image Source: Wikimedia: Incineration plant
So in effect incineration is considered a very effective method of waste management. What then are the advantages and disadvantages of incinerators?
Advantages of Incineration of Waste
Incineration is a practical method of disposal that saves a lot of money on transport of waste to landfills and thus also the carbon footprint that such transport leaves behind. The sheer reduction in the space required to dispose of the 10 percent of waste that it does produce relieves pressure on land, which in urban areas can constitute a big saving. Landfills have never been a pretty site and also give rise to a lot of pests and insects. An incinerating plant will look like any other industrial structure. Waste to Energy (WTE) incinerating plants have a huge advantage that they can produce electricity which in the long run can help to reduce costs. A 250 ton per day incinerator can produce 6.5 megawatts of electricity per day and this itself can save about $3 million per year. Some cold countries also use the heat from incinerators for heating of offices and houses in locations near the plant.
Gases and leachates that are produced in landfills by waste are totally eliminated and the waste that is produced in the incineration is totally free of any environmental risk. In fact there are efforts to convert even this waste to other materials.
Image Source: Wikimedia : Incinerator
Disadvantages of Incineration of Waste
The high cost of incineration plant has been a turnoff of for municipal authorities and is only now being addressed with the introduction of WTE plants. The need for huge waste to incinerate has led to abandonment of other plans for recycling and reuse of waste. Dioxins are produced in the treatment and is a cancer forming chemical. These are produced in the smoke stack. The plants require skilled personnel for operation and continuous maintenance.
The Process of Incineration
In the process of incineration, incinerators reduce the waste by burning it after the incinerator is initially fired up with gas or other combustible material. The process is then sustained by the waste itself. Complete waste combustion requires a temperature of 850º C for at least two seconds but most plants raise it to higher temperatures to reduce organic substances containing chlorine. Flue gases are then sent to scrubbers which remove all dangerous chemicals from them. To reduce dioxin in the chimneys where they are normally formed, cooling systems are introduced in the chimneys. Chimneys are required to be at least 9 meters above existing structures.
The advantages and disadvantages of incinerators need to be weighed carefully by any civic authorities considering this as an alternative. WTE plants are gaining more favor and the designing of incinerators is being constantly evolved to increase efficiencies and reduce production of dioxins.