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Abstract Food waste (FW) causes economic and environmental problems worldwide. Currently, most food waste is landfilled or incinerated for possible energy recovery. However, these methods have serious adverse effects on the environment. FW is nutritionally rich and offers a unique microbial feedstock for the production of numerous valuable bioproducts. The aim of this review is to investigate the technologies used to convert FW to forms of renewable energy such as biodiesel, ethanol, hydrogen and methane. Life-cycle assessment is performed to examine and compare the environmental effects of various methods of FW conversion. Keywords Food waste


Biodiesel
Ethanol
Hydrogen
Methane

1 Introduction Food waste (FW) is organic waste discharged from various sources, such as food-processing plants, domestic and commercial kitchens, cafeterias and restaurants. It comprises the ‘end products of various food-processing industries that have not been recycled or used for other purposes’, which are regarded as ‘the non-product flows of raw materials whose economic value is less than the cost of collection and recovery for reuse; therefore discarded as waste’ (Ezejiofor et al. 2014). According to the Food and Agricultural Organisation (FAO), between 1.3 and 1.6 billion tonnes of food, such as fresh vegetables, fruit, and meat, bakery and dairy products, are lost along the food-supply chain each year. This accounts for one third of the food produced globally for human consumption. Every year, food

W.-J. Deng (&) Department of Science and Environmental Studies, The Education University of Hong Kong, Tai Po, NT, Hong Kong e-mail: [email protected] © Springer Science+Business Media Singapore 2016 O.P. Karthikeyan et al. (eds.), Recycling of Solid Waste for Biofuels and Bio-chemicals, Environmental Footprints and Eco-design of Products and Processes, DOI 10.1007/978-981-10-0150-5_13

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worth billions of dollars is wasted by the developed economies of the world, whereas the greatest loss occurs during food production in low-income countries. However, the problem does not end with food wastage. More than 95 % of FW ends up at landfill sites, where it is converted into methane, carbon dioxide and other greenhouse gases (GHGs) by anaerobic digestion (AD). The negative consequences for the environment are severe. FW generation is expected to increase over the next 25 years due to economic development and population growth, mainly in Asian countries. In addition, when FW is buried at landfill sites, its high energy value and the opportunity to obtain a carbon-rich feedstock through regeneration are lost. Kiran et al. (2014) summarised typical foods wasted in Asia-Pacific countries and around the world, as shown in Table 1. In a report by the FAO, food produced but not eaten was estimated to add an annual 3.3 billion tonnes of GHGs to the planet’s atmosphere. In addition to its adverse environmental effects, the wastage of food costs producers (excluding fish and seafood producers) $750 billion per year. With global p