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| Fig. 1: The Jordan Biogas Plant. (Courtesy of the Jordan Biogas Company) |
In a world where we are actively trying to promote energy independence and reduce overall greenhouse gas emissions, we need to look at alternative energy sources other than fossil fuels to sustain our lifestyles. Waste-to- Energy is one way of doing that.
"Waste to Energy" is essentially a term used to describe the process of generating electricity from the primary treatment of waste. Considering our consumption habits have caused a worldwide waste problem, there is a need for new methods to safely dispose this waste in an efficient manner. Waste-to-Energy is known to "reduce the amount of materials sent to landfills, prevent air/water contamination, improve recycling rates and lessen the dependence on fossil fuels for energy generation". [1] There are two main methods of waste-to-energy used: combustion and gasification. Combustion, which is the more common practice, involves burning the municipal solid waste to boil water, which then powers the steam generators that are used to make electric energy. Gasification is a process where burning is not used. Instead, the municipal solid waste is combined with small amounts of air or oxygen, which breaks the material down into simpler molecules, creating a gas that can in turn be converted into electrical energy. [1]
Jordan is a small country in the Middle East, with few natural resources, located between Palestine, Saudi Arabia, Iraq and Syria. One of the biggest challenges faced by the country is securing a stable energy supply to the population of 8 million, seeing that Jordan has no indigenous energy resources, a high dependency on imported energy, and an increasing demand due to the influx of refugees into the country. [2]
The growing population In Jordan is consequently leading to larger volumes of waste being disposed of. The capital Amman is divided into districts, and each districts generates a different volume of waste. The city deals with the waste that is generated by dispersing community containers throughout the city, and asking the residents to dispose their trash in these containers. The municipality then collects the trash from the containers in specific collection vehicles at least once a day, transporting it to the closest transfer station out of the three existing ones. After that, final waste is taken to "Ghabawi Sanitary Landfill", which meets international standards of collection, filtration and treatment processes. [3] Municipal solid waste in Jordan amounts to around 1.96 million tons each year, with a generation rate of .95 kg/cap/day in urban areas. [4] Therefore, plans for proper management of waste disposal were set out. Those plans included extraction of landfill gas in Ghabawi and final utilization of the methane product for energy. The gas recovery was a project initiated in November of 2009 under a "Design-Build-Operate" contract proposed by the Hashemite kingdom of Jordan as well as the Government of Luxembourg. Other plans involved setting up the "Jordan Biogas Plant", where the main purpose was to use the waste to generate electricity for the country. It receives 60 tons of organic waste daily from food waste by restaurants, vegetable waste from farmers markets, slaughterhouse waste etc. [5] The plant consists of a receiver for the solid wastes, a receiver for liquid waste, a waste conveyor, a mixing tank which mixes the waste to form slurry, a reactor which receives the slurry anaerobically, a separator which receives the digested slurry and separates it into liquid and solid form, storage tanks, a gas cleaning system, a gas drying system, a gas storage system and a gas engine generator producing electricity. [5] This plant produces 3.5 megawatts of electricity from the biogas and methane from the landfill. Through the different parts of the system, the waste is mixed, sent to the reactor where fermentation takes place, and finally the biogas is processed, cooled and stored. The biogas is then burned, and this process is what generates electricity. [3]
Obtaining energy from "Waste-to-Energy" is considered to be a clean, "guilt-free", reliable method of generating electricity. Although burning trash is related with major air pollution, "Waste to Energy" pollution technology ensures that emissions from the smokestacks are controlled and are relatively safe for the environment. In the boiler of the plant, air is injected in to control release of nitrogen oxide. Mercury release is controlled when carbon is injected into the exhaust gases. The dry scrubber on top of the stack contains a lime slurry so that when gases pass through sulfur dioxide emissions are controlled. Finally, combustion gases are also controlled since they pass through a bag-house that contains multiple fabric filters that get rid of metals and particulate matter. [6] Gasification on the other hand takes place in a low oxygen environment where the formation of dioxins and SOx and NOx pollutants are limited. [1]
Waste-to-Energy plants still emit greenhouse gases, but the amount is a lot less than the gases generated by ordinary landfills that do not properly dispose trash. Another benefit is that it deals with the growing trash problem in the country, and considering Jordan is quite efficient in the collection of waste, this method is especially useful in this context. Finally, with the 2.2% population growth rate in Jordan, electricity generation needs to increase as well through the introduction of a renewable energy mix with an emphasis on biogas.
Finally, when looking at different opportunities to deal with the municipal solid waste, it is important to recognize that this method (waste-to-energy) should be considered after other important strategies to manage waste, such as prevention, reusing, and recycling are implemented. These need to be practiced to the maximum before considering waste-to-energy as the sole method of managing waste in the country.
© Zaha Masri. 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.
[1] A. Klein and N. J. Themelis, "Energy Recovery From Municiap Solid Wastes by Gasification," ASME 1572345, Proc. 11th Annual North American Waste-to-Energy Conference, 26 Apr 03.
[2] W. H. Bloss and F. Pfisterer, Eds., Advances in Solar Energy Technology, Vol. 4 (Pergamon Press, 1988).
[3] M. Medina, "Solid Waste Management In Amman," BioCycle 52, No. 10, 44 (2011).
[4] M. Aljaradin and K. Persson, "Environmental Impact of Municipal Solid Waste Landfills in Semi-Arid Climates - Case Study - Jordan," Open Waste Manage. J. 5, 28 (2012).
[5] Z. S. H. Abu-Hamatteh et al., "Biogas Energy: Unexplored Source of a Renewable Energy in Jordan," Renewable Energy and Power Quality Journal, No. 8, 202 (April, 2010).
[6] S. L. Otto, "Waste-to-Energy Technology Is Cleaner and Safer than Generally Believed," MinnPost, 6 Jan 13.