Scientists turn food scraps into green energy resource

A Self-sustaining system recycles food waste to produce electricity, heat, and fertilizers.

A team lead by researchers from NUS has developed a self-sustaining anaerobic digester system that recycles food scraps to produce electrical energy, heat and fertilisers.
A team lead by researchers from NUS has developed a self-sustaining anaerobic digester system that recycles food scraps to produce electrical energy, heat and fertilisers.

Scientists at the National University of Singapore (NUS) in collaboration with the Department of Chemical and Biomolecular Engineering at NUS Faculty of Engineering and Co-programme Director of E2S2-CREATE, researchers from NUS and Shanghai Jiao Tong University have developed a self-sustaining anaerobic digester system that recycles food scraps to produce electrical energy and heat.

Through this easy-to-operate digester system, scientists were able to generate electricity, heat, and fertilizers. It requires less maintenance and ensures optimal performance and safety. The fascinating is it 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.

Assoc Prof Tong, who is also a Principal Investigator at NUS Environmental Research Institute (NERI) said, “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.”

Dr Zhang Jingxin, Research Fellow at NERI, who designed the system said, “An anaerobic digester works like a biochemical stomach that breaks down organic matter in an oxygen-free (anaerobic) 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.”

The heat is reused to deliver hot water that gets diverted over into the coating layer encompassing the anaerobic digester tank to guarantee that the assimilation is kept up at an ideal working temperature of around 50 degree Celsius. From the control PC, sensors and lights, to the motors, pumps and ventilating fans, each segment of the framework runs totally on power created from the independent framework.

Excess electrical energy is stored in batteries which can be utilized to power or charge electronic gadgets, for example, cell phones and tablets. In light of the group’s counts, one ton of nourishment waste can produce between 200 kilowatt-hours (kWh) to 400 kWh of power, contingent upon the arrangement of the sustenance squander. For example, sustenance squanders that is high in starch, protein and fat substance create more biogas, in this way yield more electrical vitality.

The researchers have developed a mobile anaerobic digester system which is currently being piloted at Raffles Hall, one of the six halls of residence of NUS, for about six months beginning from late January 2018.

The system is housed in a 20-foot container and can be purposefully carted off to venues to fulfill ad-hoc demands for a food waste recycling facility. This mobile unit can be parked within two outdoor parking lots, and has solar panels on its roof to harness solar energy as a backup power source and a tank for collecting rain water.

The team is targeting to process up to 200 kilograms of food waste daily and will be using the system to test out different configurations. Excess electrical energy generated by the system is channelled to a mobile charging station where students can charge their mobile phones and tablets for free.

Assoc Prof Tong said, “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.”

Currently, the team is closely monitoring and studying the feasibility and outcomes of the two anaerobic digester systems. They are also working with other NUS research groups to expand the project, such as processing the digestate into suitable fertilizers for horticulture and crop farming.