|Fig. 1: Viridor's 24 MW waste to energy plant located in Ardley, Orxfordshire, UK. (Source: Wikimedia Commons)|
The industrialization and economic development of a nation, whether developed or undeveloped, is likely met with an increase in consumption of raw materials transformed into useable goods.  These useable goods are consumed and the resultant is waste in the form of recyclable goods or Municipal Solid Waste (MSW). Municipal Solid Waste can be described as the things that we as consumers commonly use and then trash, including paper, old electronics, old furniture, food scraps, yard trimmings and things alike.  The amount of Municipal Solid Waste (MSW) produced by the United States has been increasing steadily since the middle of the 20th century. In fact, the generation of MSW increased by a rate of 2.5% over the two-year period from 2002 to 2004, jumping from 335.8 to 352.6 million tons of waste.  One method for tackling this startling reality is turning that waste into energy through a process commonly known as Waste to Energy. We will discuss the process of turning waste into energy, highlighting methods for improved efficiency, as well as take a look what the future holds for the global WtE market.
There are several methods for making energy from waste, but incineration is the most common, used to create both electricity and thermal energy. In a modern WtE plant, the waste is first measured and evaluated for its potential to be used before it is fed into a hopper, which could hold the waste for a matter of days before it is combusted. During the incineration, no other fuel is necessary besides the waste itself, as the temperatures reach around 1000°C. Some material will not be combusted and is sorted for further recycling processes. The high temperatures produced in the furnace then heat water running through furnace pipes into steam. This steam pressure is transferred to a turbine and generator to create electricity. 
However useful this incineration method may be for creating electric and thermal energy, it is not always as efficient as expected, with plants in the European Union averaging about 58% efficiency and those in the U.S. coming in at about 44%.  Using the excess energy created from incineration as district heating is one way to get the most out of the WtE process. Even after the steam has fulfilled its electricity producing function, it still contains heat which can be used for general district heating, heating water for buildings and domestic residence in the area surrounding the plant.  In Denmark, there exist many small WtE plants scattered throughout the nation in close proximity with communities, making the prospect of district heating very feasible.  For nations that cannot apply this model as easily, there are other modes for improved WtE efficiency, such as the combination of a gas turbine with the WtE plant, which has been used in both Japan and Spain. The addition of the turbine adds exhaust gases to the equation in order to further heat the steam and recover more energy from the steam turbine. At a plant in Zabalgarbi, Spain, recovery of electrical energy was increased by 20% using the gas turbine WtE combination. 
In comparison with other methods for power generation and waste management, Waste to Energy technologies continues to stand as an expensive option, but the global WtE had a valuation of 25.32 billion US dollars in 2013 and is projected to grow to 40 billion by the year 2023, leaving the door open for other nations to enter the market and existing users like the United States to improve their current industry. [4, 5] As of 2013, the European Union is leading the way in size and sophistication of WtE market, holding an impressive 48% of market share. Japan leads the way in the Asian market, looking towards more efficient forms of technology, but China has strong potential to continue its steady WtE growth rate which has led to a doubling of market capacity between 2011 and 2015. 
Improvements in WtE industries all over the world are a good sign, but as previously stated, they are the resultant of the inevitable increase in global waste production. According to the World Energy Council's 2016 report on energy resources, we can expect global waste production to increase to 6 million tons per day by 2025, and by the end of the century, we could witness a whopping 11 million tons of waste generation per day. Although WtE only holds a minimal 6% of the global waste management market, it's growth will boast contribution in the fight against the impending increase in waste generation. 
© Brian Nana-Sinkam. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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