by Lay Leng TAN
plant that generates energy from left-over food scraps has started running in Singapore to process some 300 tonnes of food waste a day. When fully operational by the end of 2007, the facility can ramp up to handle up to 800 tonnes of feed at maximum capacity in its next phase of development.
The highly sophisticated plant represents the first such venture in Asia for IUT Global, an environmental waste technology and management company headquartered in Singapore. By collaborating with an Austrian partner to develop cutting-edge technology, the venture represents a model pilot project for Asia. Europe’s greater expertise in such technology results from regulations forbidding the disposal of organic waste in landfills.
Edwin Khew, CEO and managing director of IUT Global, explains that in simple terms the biological system employs bacteria that digest organic matter to release methane gas, which then gets converted into energy. Food outlets and manufacturers in Singapore provide the organic food waste to feed the reactor. The IUT Global plant generates 3 megawatts of power per hour, of which 0.5MW maintains the various processes and 2.5MW goes into the grid every hour. Each 100 tonnes of food waste generates about 1MW of energy.
In reality, the system is of course much more complex. A high-temperature anaerobic bioreactor uses carefully selected bacteria to digest waste materials and produce gas in as short a time as possible. The microorganisms go into a digestor filled with waste materials to grow and proliferate. They feed on the organic food and produce methane. The whole operation involves many factors, such as temperature, type of waste, combination of bacteria, and so on, to function at the optimum level. When the bacteria reach their equilibrium state, the system will continue to run indefinitely as long as it gets food waste.
Khew has partnership in IUT AG, a European company that jointly develops the full food-recycling system. The biomethanisation process comprises three parts: pre-treatment, digestion, and composting. Although most operators possess only the digesting portion, IUT Global has proprietary sorting and screening expertise as well as in-house technology on high-temperature thermophilic biodigestion. It also owns a whole range of advanced composting technology that provides high-quality biocompost and operates under conditions that produces no odours. By integrating the best of the three processes, the company feels confident it offers the most state-of-the-art operation in Asia.
IUT Global collaborates with research groups in the chemical, environmental, and microbiology departments at the National University of Singapore and the Institute of Chemical and Engineering Sciences to improve even further the already efficient biomethanisation process as Khew feels the advantage of a biotech system is the limitless discovery of bacteria consortia that will allow the digestor to operate under conditions where more gas can be produced at higher temperatures and shorter digestion times. They therefore investigate such variables as increasing the temperature to speed up operation, and culturing the right combination of bacteria to get the best mix to digest various wastes, among other biochemical parameters.
Although many technical issues exist, Khew sees acquiring correctly separated waste as the biggest hurdle. It requires a big change of mindset for people unaccustomed to thinking about what to do with their waste products, especially organic waste. The challenge lies in educating them about proper waste sorting at the source and making them aware of the contribution this makes to helping the environment. It takes only a little extra effort to segregate food from plates and containers.
Furthermore, by removing the estimated 20% food waste from the rubbish incinerator plant, power-production efficiency can jump by more than 20% as the lower calorific waste is taken out of the incineration process and biodigested in the IUT plant to generate “green power.”
Roadblocks and Motivations
Because of environmental issues such as smell and viability, the rate of food waste recycling remains very low in Singapore — 5–7% over the last 20 years. Most organic waste ends up in incineration plants and before that in landfills such as Lorong Halus and Tampines. Landfilling is a cheaper alternative than incineration and is the treatment process of choice by most Asian countries because of the abundance of land. Landfilling unfortunately allows digestion of the organics in the landfill that generates methane gas; methane is 24 times more destructive as a greenhouse gas compared to carbon dioxide. This noxious gas also renders the landfill unusable for up to 60 years.
Singapore has switched to incinerating its organic waste, but toxic ash remains. Furthermore, the wet-waste component reduces incinerator efficiency. The best approach lies in treating such waste separately to extract the maximum amount of energy, followed by recycling the product as biocompost for organic growth mediums, resulting in a viable sustainable solution.
So, what holds companies back from investing in such clean technology? When oil was cheap, the low cost made development of alternative energy source dismissible. However, with climbing fuel prices and concerns over climate change, businesses have to pay serious attention to renewable energy.
Recycling usually concentrates on materials with high value such as glass, paper, metal, and plastic. Organic waste presents more difficulties in recycling because of the associated bad smell and contamination caused by the organics. Singapore, a small island, justifiably finds this a big issue.
IUT Global’s anaerobic process creates no smell as the airless or anaerobic digestors contain and extract all gases for combustion in gas generators to produce power. After digestion, the end product is composted in an aerated enclosed composting facility to ensure production of high-quality biocompost. This composting facility also acts as a biofilter where odours generated by the pre-treatment of the organic waste prior to feeding the digestor is filtered by the compost. As an additional odour protection, this air coming out of the composting facility is put through bio-scrubbers to polish off any remnant odours.
Another challenge arises when feeding small amounts of renewable energy into the electric grid without disrupting its operation. The Energy Market Authority and the Singapore Grid have been working closely with IUT Global (being a first-mover small generator) to resolve all these issues to allow other small renewable energy generators to supply into the Singapore grid.
Hotels, restaurants, food courts, shopping malls, and enlightened management generating food waste all supply their unwanted matter to IUT’s Singapore plant. Incentives to encourage participation include lower cost for waste collection, green power for manufacturers, and the Singapore Environment Council’s/National Environment Agency’s endorsement of these companies’ efforts. The stamp becomes a powerful marketing tool for selling environmentally sustainable products, especially in markets like the US and Europe that embrace such practices.
The biocompost by-products also help the greening of Singapore by providing blended topsoil for plants. Singapore can back up its claim of being a model environmentally green city. Khew feels confident that more enterprises will participate in the recycling of food waste products to generate sustainable energy because it attacks two pressing problems simultaneously — less use of fossil fuel energy and the recycling of this waste as biocompost to enrich the poor soil conditions in Singapore and elsewhere in the Asian region.
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