The ‘Grime Scene Investigation’ took place on Monday 23rd November next to the Butler Court student hall. The following bin bags were collected from the hall and inspected: food waste, recycling and general waste.
Five food-waste bags were collected from the kitchens in the student hall. Additionally, the food waste misplaced in the recycling and general-waste bags was sorted and assessed. Food waste was classified and weighed according to the following criteria:
- Edible / Inedible
- Animal based / Plant based
- Packaged / Unpackaged
- There was a significant amount of food waste in the general-waste bag. The amount of food waste in the recycling bag was much smaller.
- Most of the food waste is plant based and unpackaged.
- The amounts of edible and inedible food waste were similar in the food-waste bags. In the recycling bag, most of the waste was inedible (however the sample was too small to come to definitive conclusions), but in the general-waste bag 75% of the food waste was edible. There is a need to reduce edible food waste by behavioural change in consumers which can be caused by an increase of awareness of the issue through different initiatives and campaigns.
- Sometimes it was difficult to assess what was edible and what inedible (e.g. apple cores, tops of strawberries). In these cases, we tried to separate manually the edible part from the inedible. When this was not possible (e.g. apple core), an estimate of how much is edible was used. When the amount of edible food waste was very small (meat on bones) everything was considered inedible.
- A small portion of the food waste contained in bags was not possible to weigh: tiny pieces of food and liquid waste. This explains why the weight of the full bag is larger than the sum of the different food-waste categories.
- The large bags were weighed imprecisely (food-waste bag 5 and general-waste bag). A better scale in the range of 1-15 kg will be necessary in the next Grime Scene Investigation.
- The different weight of bin bags of similar size was explained by the liquid remaining in the bag after emptying.
- The waste collected was not very significant in terms of composition: food disposed by one person one time changes the proportions notably (e.g. meat bones in food-waste bag 3). Larger sizes of samples would be useful as well as repeated assessments over several months.
- The food-waste collection is currently sent to anaerobic digestion by Wastecycle. The final aim of the classification used in this report was to better understand the types of food disposed of in order to find an optimal waste management alternative to deal with it. This works well for food manufacturing waste but not for consumer food waste, as this is very heterogeneous and not sorted when treating it. Moreover, fewer alternatives are available for this type of food waste, such as redistribution for human consumption and animal feeding.
For more information, please contact:
Grime Scene Investigation – Food waste