Distributed recycling system with microwave-based heating for obsolete alkaline batteries

Abstract

In the recycling sector, the transition in system networks from centralization to decentralization is an emerging concept. The feasibility to decentralize the recycling of e-waste needs to be analyzed, considering the different characteristics of each municipality. We propose a distributed recycling system for obsolete alkaline batteries using microwave apparatus as a small-scale recycling technology. Firstly, the reactivity of obsolete alkaline batteries with microwave irradiation was empirically examined. In lab-based experiments, pyrometallurgical microwave-based heating successfully separated a mixed sample of Mn₃O₄ and ZnO contained in obsolete alkaline batteries and recovered MnO and Zn separately, achieving a recovery rate of 97% under an ambient atmosphere. It was also found that the recovery rate of zinc obtained by microwave-based heating is 1.5-fold that using conventional electric furnace-based heating, with less than half of the heating time required. The experimental results were then used to analytically determine the energy efficiency of the distributed recycling system for the treatment of obsolete alkaline batteries with microwave apparatus compared with the centralized recycling system. In an analytical study which considered the characteristics of 1710 municipalities in Japan, it was found that an annual energy and greenhouse gas reduction of 26,500 GJ and 1.54 Gg-CO₂eq, respectively, can be achieved at the national level by creating a well-balanced harmony between the centralized and distributed systems. The method applied in this study to determine the effectiveness based on population and intercity transport distance can be readily implemented in any city for the adoption of a distributed recycling system.