Pretreatment of food waste by heat for sugar production

• Main Author: Goh, Wei Hao
• Other Authors: Liu Yu
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/61242
• Institution: Nanyang Technological University

In recent years, Singapore’s food waste generation has increased tremendously to 796,000 tonnes in 2013 which is the largest spike in 6 years. Hence, this presents an added burden on the capacity of incineration plants in Singapore as well as the Pulau Semakau landfill site. Therefore, it is critical to ramp up efforts on the management of food waste. One such option is to opt for energy recovery and this requires a fundamental change of attitude by treating wastes as misplaced resources. Hence, thermal pretreatment has been chosen to enhance the hydrolysis of food waste to produce useful materials such as glucose. However, glucose production was less than ideal and a more generalized indicator of hydrolysis effect would be soluble chemical oxygen demand (SCOD). Solubilized organic material, as a result of thermochemical pretreatment, are possible useful biodegradable materials for subsequent degradation by anaerobic microorganisms to produce biogas such as methane gas for energy generation. Thermal pretreatment at 120℃ at 90minutes gave the best SCOD. Subsequently, 1.5%HCl and 1.5%NaOH were introduced into separate food waste samples for the thermal pretreatment and SCOD results increased by 237% and 28% respectively compared to thermal pretreated food waste. Finally, the samples were subjected to anaerobic digestion in biochemical methane potential (BMP) tests to assess on their biodegradability. Heat + alkaline gave the best cumulative methane yield at 760.65ml/g VS and it has the greatest increase of 91.59% of cumulative methane yield over unpretreated food waste. Finally, a basic economic feasibility study on the thermal pretreatment with anaerobic digester process was investigated and the power generation from the biogas production proved to be attractive. Further studies such as to set up a prototype of a small scale complete anaerobic digestion system to assess the overall energy consumption of heat exchangers and biogas boiler would be good to provide a more complete assessment of the overall economic benefits.