Urban biorefinery for waste processing

Abstract

This paper uses the biorefinery concept as a way to approach the problem for integrated municipal solid waste management. The design of an urban biorefinery, integrating the plastics and paper recycling processes, was performed using a superstructure optimisation approach. The objective function was the maximisation of before-tax profit. The approach was applied to a case study in Bangkok for the design of an urban biorefinery processing 500,000t/y of waste. Three scenarios were analysed: (1) considering recycling and technology-specific targets, (2) considering supply of local demands and (3) similar to 1 but without incentives for waste-to-energy facilities. The biorefinery approach allowed balancing deficits and surpluses from the various processes, making the whole plant profitable. Scenario 2 showed that more resources can be circulated within the system if policies focus on targets for satisfaction of local demands. Under scenario 3, the biorefinery offers economic advantage over stand-alone processes such as AD with CHP or incineration and also promotes the recycling of resources. Therefore, urban waste biorefining has the emerging property of enabling resource looping and can potentially increase resource efficiency in urban environments. This property does prevent destruction of valuable materials, that otherwise go to energy production, and favours their recovery and circularity within the local system.