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MPhil in Engineering for Sustainable Development

global challenges, engineering solutions

Studying at Cambridge

Nathan Vandromme

Household waste flow analysis in a UK context

Households in the UK account for 11% of all waste, equivalent to 26.7 million tonnes per year. Local authorities regulate waste management schemes and are transitioning from separate to co-mingled and dual stream collection schemes to reduce costs and increase the amount of dry recyclable waste (DRW) collected per household. However, mixing waste increases contamination, impacting the quality of the final product and the cost of sorting it at Material Recovery Facilities (MRF). This research investigates if co-mingled collection schemes in the UK result in higher waste collection rates and if the lower quality of co-mingled waste affects the ‘upcycling’ of recovered materials.

The collection rate and recycling rate of DRW are compared between 300 English local authorities using separate, dual stream and co-mingled collection schemes. Then, the waste final destinations are compared between 7 MRFs, managing the waste of more than 40 local authorities using a co-mingled scheme, and 15 local authorities using a separate collection scheme. Finally, the quantity and value of the waste streams coming in and out of two MRFs are compared.

The results demonstrate that even though the recycling rate of co-mingled scheme is higher, the difference becomes marginal when rejects rate, contamination and residual waste are taken into account. Additionally, separate collection schemes tend to favour local reprocessing of recovered materials, whereas waste sorted in a MRF is usually sold to traders. This can be partially explained by the ability of MRFs to adjust (to a limited degree) the contamination in their recovered materials streams depending on the requirements and specifications of the market, which gives them the opportunity to find more competitive buyers.

In conclusion, recovered materials of similar quality and in similar quantity can be obtained with both collection methods, with the exception of glass, for which a significant proportion, when sorted at a MRF, is ‘downcycled’ by reprocessors into aggregate. Therefore, when conducting a cost evaluation for a separate glass collection, benefits for MRFs and reprocessors related to not having to sort glass should be included. Suggestions are made on how policy, regulating the change of collection method for local authorities, could be changed to create a more objective framework and better comparative processes.