AsianScientist (Jun. 1, 2018) – Researchers at the National University of Singapore (NUS), in collaboration with scientists from Shanghai Jiao Tong Univeristy, have developed a method to convert food waste into energy and fertilizer.
In Singapore, food waste accounts for about ten percent of the total waste generated in the city state. The recycling rate of such waste currently stands at about 14 percent.
In the present study, a team of scientists led by Associate Professor Tong Yen Wah at NUS have invented an anaerobic digester system that recycles food scraps to produce electrical energy and heat. This digester system is self-sustaining as the electricity and heat generated during the digestion process is sufficient to fully power the system and its processes.
“We want to play our part in reducing waste in Singapore. Our digester system is easy to operate, and we can now generate electricity, heat and fertilizers from food waste that would otherwise be disposed of. All the processes in the system can be easily controlled and monitored to ensure optimal performance and safety. For instance, we have sensors that are programmed to send out end-of-process updates and flag any safety concerns in real-time directly to the team via mobile phone alerts,” said Tong.
Dr. Zhang Jingxin, a research fellow at NUS, explained that the anaerobic digester works like a biochemical stomach that breaks down organic matter in an oxygen-free environment.
“Using a specially formulated mix of anaerobic micro-organisms, the digester system efficiently breaks down food waste into biogas that is subsequently converted into heat and electrical energy,” he added.
The heat is reused to produce hot water that gets channeled back into the jacket layer surrounding the anaerobic digester tank to ensure that the system is maintained at an optimum working temperature of about 50 degree Celsius. From the control computer to the engines, pumps and ventilating fans, every component of the system runs entirely on electricity generated from the self-contained system.
Excess electrical energy is stored in batteries which can be used to power or charge electronic devices such as mobile phones and tablets. Based on the team’s calculations, one ton of food waste can generate between 200 kilowatt-hours (kWh) to 400 kWh of electricity, depending on the composition of the food waste. For instance, food waste that is high in carbohydrate, protein and fat content produce more biogas, thus yielding more electrical energy.
The anaerobic digester also converts about 80 percent of the food waste fed into the system into nutrient-rich digestate, which can be processed to produce liquid fertilizers for farming and horticultural needs.
The researchers are also working on a larger anaerobic digester system to cater to the needs of a canteen or food center. This system would be able to process up to 400 kilograms of waste food daily.
“Unlike composting which is used in a lot of commercial waste food digesters, anaerobic digestion is relatively odorless, which makes this approach suitable for an urban city environment. Our system removes moisture and trace gases such as hydrogen sulfide that gives food waste its unpleasant smell,” said Tong.
Source: National University of Singapore; Photo: Pixabay.
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