Converting Municipal Solid Waste (MSW) to Energy
The oldest technology used to convert MSW to energy is incineration. Incineration is the combustion of organic material such as waste with energy recovery. Incinerators have electric efficiencies on the order of 14-28% the rest of the energy generated is lost as waste heat.
Incineration generally entails burning garbage to boil water which powers steam generators that make electric energy to be used in our homes and businesses. One serious problem associated with incinerating MSW to make electrical energy, is the pollutants that are put into the atmosphere when burning the garbage that power the generators.
These concerns regarding the operation of incinerators include fine particulate, heavy metals; trace dioxin and acid gas emissions, even though these emissions are relatively low from modern incinerators. Other concerns include toxic fly ash and incinerator bottom ash management. Discussions regarding waste resource ethics include the opinion that incinerators destroy valuable resources and the fear that they may reduce the incentives for recycling and waste minimization activities.
These pollutants are extremely acidic and have been doccumented to cause serious environmental damage by turning rain into acid rain. One way that this problem has been significantly reduced is through the use of lime scrubbers on smokestacks. The limestone mineral used in these scrubbers has a pH of approximately 8 which means it is a base. By passing the smoke through the lime scrubbers, any acids that may be in the smoke are neutralized which prevents the acid from reaching the atmosphere and hurting our environment. According to the New York Times, modern incineration plants are so clean that "many times more dioxin is now released from home fireplaces and backyard barbecues than from incineration.
There are a number of other new and emerging technologies that are able to produce energy from waste and other fuels without direct combustion. Many of these technologies have the potential to produce more electric power from the same amount of fuel than would be possible by direct combustion. This breakthourgh is mainly due to the separation of corrosive components (ash) from the converted fuel, thereby allowing higher combustion temperatures.
Thermal technologies include gasification, which produces combustible gasses, hydrogen or synthesis gas (nitrogen and carbon monoxide), that can be used to make synthetic fuels. Thermal depolymerization produces crude oil for further refining. Pyrolysis producing bio-oil. Plasma arc gasification producing carbon monoxide and hydrogen for use in fuel cells or generating electricity.
Non-thermal technologies anaerobic digestion producing bio gas rich in methane. Fermentation production for ethanol.
These emerging technologies show much promise for increased energy production, reducing green house gasses and reducing the need for landfills.