Ada Genavia
Apr 7, 2012

Waste-to-energy: A growing industry for renewable energy and a greener future

Spittelau incineration plant is one of several plants that provides district heating in ViennaIt has taken a while for society to make “one man’s trash into another man’s treasure” pertinent to industry. Trash has been recognized as a source of energy for at least a century -- however, since the outset of the industrial revolution, industrial waste has long ended up as just waste. It has polluted environments and caused illnesses and harm to society and other species. In recent years, thankfully, energy innovators and engineers have started rapidly developing ways to turn that waste into money, energy and a cleaner environment.

With billions of people on this planet and the continuing population growth, something has to be done about better waste management. Waste-to-energy (WTE) is a renewable form of energy that has become the basis for many of the most successful solid waste management systems in the US. It is a process that takes incineration from municipal solid waste creating an energy source in the form of electricity or heat. The waste is transferred into combustion chambers where it is combusted and reduced to ash. The heat produced from the combustion stage heats up water in steel tubes that outlines the chamber walls. The water is turned to steam and sent through a turbine generator that generates electricity which is then received by the power grid.

Garbage has sufficient energy potential; each US citizen produces nearly one ton of of trash per year. Researchers have estimated that this is enough electricity generated for 8 million homes. WTE facilities offer a safe, technologically advanced means of waste disposal while also generating clean, renewable energy, reducing greenhouse gas emissions and supporting recycling through the recovery of metals. In Oregon, Marion County has utilized a waste-to-energy plant for solid waste process since 1986. The facility generates enough electricity to power about 7,000 homes and WTE has helped to reduce greenhouse gases produced from solid waste.

Another aspect to be considered for WTE facilities is that they serve as landfill alternatives. In Lancaster County, Pennsylvania, the Lancaster Solid Waste Management Authority’s WTE facility has the primary goal of minimizing landfill consumption to protect one of the area’s most valuable resources -- farmland. They’ve processed over 7.5 million tons of waste; this would have occupied 190 acres of farmland, 100 feet deep. The plant has also recycled over 128,000 tons of metals and generated 4.4 billion kilowatt-hours of electricity which is enough to power all of Lancaster County homes for three years.

Solar, wind, geothermal, hydropower and biomass have long been top contenders for renewable energy. Energy from waste is a new player and has a promising place in the renewable energy market. There is an overwhelming amount of municipal solid waste even after reuse and recycling. This waste can serve as a constant stock of fuel for WTE facilities; it will be continually replenished for an anticipated greener future. Covanta Energy, a US-based leading operator of WTE infrastructure, considers energy from waste to be renewable because the fuel and waste is constantly replenished. The energy restored by the WTE process preserves natural resources and avoids secondary impacts from mining and the combustion of those resources.

Sugar/Ethanol Plant located in Piracicaba, São Paulo State -- it produces the electricity it needs from bagasse residuals from sugarcane left over by the milling process, and it sells the surplus electricity to the public gridAlthough salvaging energy from waste seems to be the ultimate solution for energy sustainability, there are still arguments against it. The primary conflict is the process of incineration and the emissions which are produced. Not all materials result in complete combustion and this can result in the creation of methane, nitrous oxide and gases that affect air quality. The incineration of heavy metals and other harmful substances can produce byproducts such as furans and dioxins which have highly toxic potential. Based on these facts, it can be deduced that the incineration is volatile and uncontrolled.

Modern WTE plants should not be confused with primitive incinerators, however. Covanta Energy uses several air quality controls. Specially designed boilers are used to ensure complete combustion. During the burning process, the trash is sprayed with ammonia and the air is recirculated in the boiler which reduces nitrous oxide formation. Emissions are also prevented from being released into the environment using advanced pollution control equipment. This eases concerns about greenhouse gas discharge. Utilizing waste in this way is an emerging technology improving the environmental performance of waste to energy.

According to a report by Pike Research the WTE market is rapidly growing and is expected to grow $29.2 billion by 2022. In 2011, the world produced an estimated 2 billion tons of municipal solid waste. This number will undoubtedly grow in the upcoming years which in turn increases the global demand for the WTE solution. Large corporations such as Covanta are not the only ones recognizing the value of WTE -- even the local zoo is seeing its potential. In Colorado, the Denver Zoo has emulated the iconic garbage-burning DeLorean from Back to the Future II. The tuk-tuks (motorized carts) used for touring around the park are actually fueled with animal feces. Additionally, UK companies Versus Energy and Knowaste have taken it to the next level with the first diaper recycling plant in England. This facility will use sustainable energy produced from the organic materials recovered from disposable diapers. 

Our daily garbage is diversifying our energy mix. Population growth, rising levels of wealth, resource scarcity and continued urbanization leaves energy from waste an appealing technology option in this global renewable energy landscape. Municipal solid waste energy is one of many elements in achieving energy independence and a promising future for sustainability.