5 Energy Recovery Examples Explained
Energy recovery examples are; landfill gas capture, anaerobic digestion-gasification hybrid treatment, liquid biofuel production from agricultural waste, incineration-based heat capture, and pyrolytic cogeneration.
This article discusses energy recovery examples, as follows;
1). Landfill Gas Capture (as one of the Energy Recovery Examples)
Landfill gas capture, also known as landfill gas (LFG) recovery, is an effective approach to recover energy stored in fuel gases that are emitted in the course of biodegradation of organic waste.
The gases released from organic municipal waste in landfills can be referred to as biogas, biofuel, or biomethane; and is typically composed of approximately 50% carbon dioxide, and 50% methane, although small amounts of sulfuric gases and other compounds may also be present.
Landfill gas recovery is related to carbon capture and storage technology, because it leads to a reduction in the amount of greenhouse gas in the atmosphere [2].
It is therefore a good option to integrate into sustainable waste management and recycling schemes, to mitigate environmental degradation and achieve sustainability.
Landfill gas recovery equipment include compressors, absorption chambers, and blowers that actively collect and store biogas from landfills. Recovery wells and trenches are also used [4].
Millions of metric tons of methane can be recovered from landfills by this method. The gaseous fuel is useful for electricity generation, heating, as well as for hybrid vehicles.
Landfill gas recovery is highly conservative because it does not require direct conversion of the waste. Energy conservation is often achieved by the lack of need for active implementation of conversion methods in a biorefinery.
Also, the waste material which is not converted in the process, can still serve as a source of energy in other waste-to-energy processes like pyrolysis.
However, landfill gas recovery is not sufficient for effective waste management and energy recovery, since it does not involve removal of waste. Therefore, there is often the need to support this method with other approaches that can lead to waste removal.
2). Anaerobic Digestion and Gasification Hybrid Treatment
Anaerobic digestion and gasification are each distinct types of biomass conversion.
The combination of these two methods results in a hybrid system of waste management and conversion.
Anaerobic digestion is one of the most effective and innovative examples of energy recovery, because it serves for both energy production and waste reduction (or removal).
Also, the environmental impact of this approach is minimal compared to methods like combustion.
Studies have shown that the sustainability and energy efficiency of anaerobic digestion/gasification hybrid processes can be optimized by varying the conditions of the process [5].
3). Liquid Biofuel from Agricultural Waste (as one of the Energy Recovery Examples)
Agricultural residue, animal manure, and other forms of agricultural waste can be used to produce liquid biofuel, using any of various conversion methods.
This is an important example of energy recovery, considering that renewable energy integration is one of the principles of sustainable agriculture. Energy recovery can easily be integrated into sustainable farming, especially in large-scale scenarios, by utilizing waste materials for fuel and energy production.
Methods that can be applied to this effect range from chemical and biochemical to thermal methods. Anaerobic digestion and catalytic fermentation are good examples; with each of them involving the role of microorganisms in biodegradation of waste.
Products of energy recovery from agricultural waste include biodiesel, bioethanol, biogas, digestate and biochar.
Biodiesel and bioethanol are important liquid biofuels, while digestate and biochar can be used as organic fertilizer for soil conservation and remediation purposes, which is a recommendable practice of sustainable agriculture.
In order to improve the quality and performance of liquid biofuel, distillation of such fuels can be carried out to remove water and other impurities [3].
4). Incineration and Heat Capture
Incineration is basically a controlled form of waste combustion.
The advantage of this approach as a means of energy recovery is its versatility. Because combustion is a purely thermal process, it does not include any chemical specifications and can be used effectively to recover energy from both inorganic and organic waste.
In incineration and heat capture, the goal is to utilize heat transfer equipment to capture waste heat from the combustion of waste.
The application of energy recovered using this method depends on the amount of energy involved. However, the most common application is water heating, although steam produced in the process can be used to generate electricity by driving a steam turbine.
Incineration and heat capture (or ‘heat recovery’) may be carried out using equipment that are designed to reduce emissions and overall environmental impact of the incinerator facility. This means that the method also has environmental significance.
5). Pyrolytic Cogeneration (as one of the Energy Recovery Examples)
Pyrolytic reactors can be equipped to serve simultaneously as cogeneration systems.
The setup required to achieve this us similar to that which is needed for incineration heat capture, including heat transfer, storage and utilization equipment.
Pyrolytic cogeneration can be ‘coupled’; which refers to a hybrid approach combining multiple energy recovery methods, or ‘decoupled’ and implemented independently.
It is suitable especially for organic waste, and produces energy in the form of heat and synthesis gas. Biochar which is a byproduct of pyrolysis can be used in agriculture to replace chemical fertilizer.
Pyrolytic cogeneration is a cheap alternative to the use of fuel-based electric generators. It is also a thermo-chemical method and involves both thermal and chemical changes of the substrate [1].
Conclusion
Energy recovery examples are;
1. Landfill Gas Capture
2. Anaerobic Digestion and Gasification Hybrid Treatment
3. Liquid Biofuel from Agricultural Waste
4. Incineration and Heat Capture
5. Pyrolytic Cogeneration
References
1). Agrifoglio, A.; Fichera, A.; Gagliano, A.; Volpe, R. (2021). “Energy analysis of a micro-cogeneration unit fed by biogas as a function of pyrolysis operating parameters.” Available at: https://doi.org/10.5802/crchim.77. (Accessed 16 September 2022).
2). Elagroudy, S.; Warith, M. (2009). “Biogas recovery from landfills.” Available at: https://www.researchgate.net/publication/325999331_Biogas_recovery_from_landfills. (Accessed 16 September 2022).
3). Gebreegziabher, T.; Sahu, O. (2017). “Chemically Synthesized Biofuels from Agricultural Waste: Optimization Operating Parameters with Surface Response Methodology (CCD).” MethodsX 4(C). Available at: https://doi.org/10.1016/j.mex.2017.09.005. (Accessed 15 September 2022).
4). Niskanen, A.; Värri, H.; Havukainen, J., Uusitalo, V.; Horttanainen, M. (2013). “Enhancing landfill gas recovery.” Journal of Cleaner Production 55:67-71. Available at: https://doi.org/10.1016/j.jclepro.2012.05.042. (Accessed 15 September 2022).
5). Yao, Z.; Li, W.; Kan, X., Dai, Y.; Tong, Y. W.; Wang, C. (2017). “Anaerobic Digestion and Gasification Hybrid System for Potential Energy Recovery from Yard Waste and Woody Biomass.” Proceedings of the ICE – Energy 124. Available at: https://doi.org/10.1016/j.energy.2017.02.035. (Accessed 16 September 2022).
