Waste to energy can be defined as the process of generating energy for treating waste. This energy is usually in the form of electricity or heat and this process is a process of energy recovery. It usually creates direct heat or electricity as a result of combustion or produces a combustible fuel product like methane, ethanol, synthetic fuel etc.
This process is gaining prominence because of the increase in waste that is being dumped in landfills and the increase in consumption and depletion of non-renewable energy like coal and oil. This method removes the shortcomings of both the trends by taking the waste and converting that into energy.
How does the process of WtE work?
The process includes burning of waste at high temperature and subsequently using the heat generated to make steam. The steam is then used to run a turbine that generates electricity. Waste from industrial sector is usually not utilized in this process, as it is toxic. Thus, waste generated from households, agricultural sector or light industries are the one used as an intermediate product in the waste to energy conversion process.
Advantages of using this method are:
- It helps conserve the natural resource that is not only non-renewable but also depleting at a rapid rate. One must not consider this process as a mere waste disposing process. It is a mechanism that helps manage waste and is complementary to recycling. It acts as a substitute to the valuable natural resource and taps the potential that lies in waste.
- Once you convert the waste, you can use two thirds of it as Carbon Dioxide neutral fuel. Waste conversion is a method that is an excellent alternative to using oil and other forms of energy. A major portion of the household waste is biomass and this portion can be used to create energy for daily use.
- It is a method that can help us reduce our contribution to global warming. By using this clean energy, we decrease our usage of fossil fuel and hence the carbon footprint and emission decreases.
One disadvantage of this process is that the process designed for conversion is limited to only certain kinds of waste. Hence, with further advancement in technologies, conversion methodologies can be diversified to utilize all kinds of waste barring the toxic ones.
What are the methods of converting waste to energy?
There are several methods for producing energy from waste. They are:
- Incineration: this is the most common method for this process. It is done by combusting organic waste. The heat that is generated during the combustion process is utilized to turn water into steam that is in turn used to power turbine to generate electricity. The plants that incinerate waste in the OECH countries have to follow certain emission standards and must keep a check on their emission of nitrogen oxide, sulphur dioxide, dioxins and heavy metals. The new plants reduce the excess volume of waste by about 96 percent. This, however, depends on the composition of the waste. There are some disadvantages of these plants as waste recovery from this leads to the emission of fine particulate matter, acid gases, dioxins etc. these need to be handled with care and should be disposed off carefully. The by-product of the process, that is not fit for use, must also be disposed off with caution.
- Gasification: it is the process of converting waste material in the presence of oxygen. It is a thermochemical process and results in a creation of a mixture of combustible gases. The steam or even the oxygen in the environment is made to react with the carbon in the waste to give rise to gases like carbon monoxide, methane and hydrogen. This is then used to create electricity. The fuel created by the gasification process can be transported and collected easily.
- Pyrolysis: this is different from gasification as it takes place in the absence of oxygen. However, the product of this process is a mixture of combustible char or bio oil. It is using heat to break the waste to make energy without using oxygen. Coal, cardboard, paper, human waste, plastic, rubber and the like can be used for this process. This process is a recent development, as far as its application to this field is concerned. The most common product of this process is char that hold on to the carbon content of biomass and hence becomes extremely suitable for soil productivity enhancement.
- Anaerobic Digestion: this process can either take place naturally or in a digester, which is a warmed airtight and airless container, which promotes bacteria to ferment waste like slurries and animal byproducts to create biogas. It is the process that creates biogas when the waste material is left undisturbed in the landfills. The main problem with using this method is that it uses liquid waste as well. Most processes mentioned above have not taken into account liquid waste. Since the production of biogas is dependent on the size of the digester or landfill, it is limited and hence is used in small-scale tasks.
- Fermentation: The process that uses yeast and other natural microorganisms to produce ethanol is known as fermentation. It involves a series of chemical reactions like hydrolysis, distillation etc.
With increasing population and consumerism, management of waste has become an important aspect of sustainable development. Thus, converting waste into energy is a boon that can not only increase the standard of living but also help retain the environmental balance that is extremely crucial. Here’s how we can conserve energy.
Do check out our article on National Energy Conservation Day here.