Waste to energy: A lucrative alternative

The enormous increase in the quantum and diversity of waste materials generated in Dhaka city and their potentially harmful effects on the general environment and public health have led to an utmost necessity of adopting scientific methods for safe disposal of garbage. While there is an obvious need to reuse and recycle some of them, the technologies for recovery of energy from wastes can play a vital role in mitigating the problem. Besides, with the increasing price and scarcity of conventional fuel in the country, this alternative energy source can be very lucrative. Waste-to-energy(WTE) technologies involve converting various elements of municipal solid waste such as paper, plastics and food wastes to generate energy by either thermochemical or biochemical processes. The thermochemical techniques consist of combustion, gasification, thermal depolymerization, plasma arc gasification or pyrolysis that produces high heat in fast reaction times. The biochemical processes consist of anaerobic digestion, hydrolysis, Mechanical Biological treatment (MBT) or fermentation using enzymes that produce low heat in slow reaction times. Some of these technologies burn waste materials in an incinerator while many of the new and emerging technologies are able to extract energy from waste without direct burning. In fact, modern plants may utilize a combination of the thermochemical and biochemical processes to ensure maximum efficiency and minimum emission. These facilities can either produce electricity and steam for process heating or they can also produce a combustible fuel commodity such as methane, methanol, ethanol or synthetic fuel.