The transportation penalty of source separation: A case study of food waste in Oslo

Optical sorting systems offer convenient municipal waste management but face persistent challenges with material purity and cross-contamination. In Oslo, these long-standing issues have been exacerbated by recent policy incentives that unintentionally discouraged proper sorting, and stricter regulatory targets are now prompting a re-evaluation of source separation. Using Oslo’s complete road network and operational data, we model three curbside food-waste collection strategies through arc-routing optimization: the current commingled baseline, separate collection with dedicated single-compartment fleets (residual stream collected weekly or bi-weekly), and co-collection with multi-compartment vehicles The logistical impact depends strongly on the chosen strategy. Decoupling streams into separate fleets introduces significant route redundancy: weekly separate collection adds about 17% driving distance at current sorting levels, and switching the residual stream to bi-weekly roughly halves this penalty without closing it. Co-collection minimizes this penalty by preserving route density, with transport requirements approaching the commingled baseline as the compartment split better matches the waste-generation ratio, falling within 3% under close matching. However, transport minimization comes at the cost of operational adaptability. Multi-compartment vehicles impose rigidities on collection frequencies and offloading infrastructure, and their efficiency is fragile: it requires precise alignment between compartment configuration and waste generation, a target that shifts as sorting compliance evolves. The dedicated-fleet penalty is structural: each fleet traverses the network independently, and reducing the residual collection frequency narrows but does not close the gap. Collection strategy, infrastructure placement, and the policy levers shaping compliance together determine the transportation outcome and should be planned jointly rather than separately.