What drives the viability of waste-to-energy? Modelling techno-economic scenarios of anaerobic digestion and energy generation for the Scottish islands

Abstract

Anaerobic digestion, a technology which converts biowaste into biogas, can address issues of waste utilisation, energy security and reducing emissions. Co-digestion of waste could improve biogas yields and synergies between sectors but requires transport of waste. To improve on existing biowaste-to-energy models which consider simple transport costs, this work combines a techno-economic model with a capacitated vehicle routing problem (CVRP) solver to consider detailed waste transport costs with actual Open Street Map (OSM) road networks. This addresses whether biowaste-to-energy techno-economic modelling is improved with more specific transport costs and more broadly how factors of resource availability, generation technology and transport costs influence the viability of anaerobic digestion and generation plants. The levelised cost of energy (LCOE) is used to compare scenarios of these aspects. The Scottish islands have been modelled as a case study due to high biowaste potential and varied topographies, which both influence transport costs. Number of waste vehicles required is improved by 42.8% and the unit cost of collection varies from £0.1–1670.0/tonne. Local topographies and waste availability significantly affects the viability of individual facilities, which might not be considered by simpler collection cost metrics. Between 14.0 and 20.6% of the regions electricity demand could be met by biogas. While industrial facilities co-located with demand have the cheapest LCOE, this can in some cases be improved with other waste streams, highlighting the need for further research on and policies supporting co-digestion, as well as improving household and business participation rates. Incentives and avoided costs are crucial to supporting biowaste-to-energy if more isolated regions are to benefit from improved waste utilisation.