Several of the waste materials that have a negative impact on the sewer system are produced by fats, oils and greases (FOG) discharged from commercial and domestic kitchens. These materials accumulate at different points in the sewer catchment, from kitchens to pumping stations, sewers and sewage treatment works (STWs), and comprise oily wastewater, floating agglomerates and hard deposits. Despite their detrimental effects, these waste materials have a high calorific content and are an ideal feedstock for energy recovery processes. So far, the overall volume of each type of waste and their physical-chemical properties in relation to their collection point are unknown. However, from a management point of view, knowledge on each feedstock quality and volumes is necessary to develop an economic viable solution for their collection and for energy recovery purposes. In this study, FOG wastes collected from households, food service establishments (FSEs), sewage pumping stations, sewers and STWs, were compared to sewage sludge in terms of organic contents and energy potentials. As expected, FOG recovered at source (households and FSEs) were 'cleaner' and had a higher energy content. Once mixed with wastewater the materials changed in composition and lost some of their energy per unit mass. Our results showed that around 94,730 tonnes.year-1 of these materials could be recovered from the Thames Water Utilities' catchment, one of the most populated in the UK. These materials could produce up to 222 GWh.year-1 as biogas, close to double of what is produced with sewage sludge digestion and around 19% of the company energy needs. Finally, even with over six million households in the catchment, the results showed that most of the FOG waste was produced by FSEs (over 48,000 premises) with an estimated average of 79,810 tonnes.year-1 compared to 14,920 tonnes•year-1 from private households. This is an important outcome as recovery from

Daily, sewage treatment works (STWs) receive large volumes of fats, oils and greases (FOG), by-products of food preparation. To increase FOG removal at STW, conventional primary sedimentation tanks (PSTs) can be enhanced using chemical coagulant or through dissolved air flotation (DAF) techniques. This work aimed to assess the potential benefits of enhanced primary treatment for FOG removal through an energy and costs analysis. To achieve this, a five-year sampling programme was conducted monthly at 15 STWs measuring FOG concentrations in crude and settled sewage (i.e. after primary treatment). In addition, two DAF pilot systems were trialled for four months and their performance, in terms of FOG removal, was assessed and compared to that of a control primary clarifier. Across the 15 STWs, influent FOG concentrations were found at 57±11 mg.L -1 . Chemical coagulants dosed prior to PSTs increased FOG removal rates on average to 71% whilst traditional sedimentation only achieved 50% removal. Effluent FOG concentrations were found between 12-22 mg.L -1 and 19-36 mg.L -

In comparison to fats, oils and grease (FOG) found in commercial and industrial effluents, very little is known about FOG discharged at household level. To address this shortcoming, household FOG production was calculated following a year‐long monthly collection at 2.3 kg/year per household, equivalent to 0.8 kg/year per capita. In the United Kingdom, these numbers translate in an annual estimated FOG production of 62 380 tonnes. Physico‐chemical characterization of household FOG showed promising results for biodiesel production. Biomethane yield was measured at 875 mL CH4/g VSadded, twice as much that of sewage sludge, making it a desirable substrate for anaerobic digestion. It was thus estimated that energy recovery from household FOG through anaerobic co‐digestion or biodiesel production could generate about 490 GWh/year in the United Kingdom. However, insights from participants revealed that most of this waste is currently not recovered, requiring the development of schemes fitting with households' routine to maximize collection rates.

The understanding of fats, oils, and greases (FOGs) pathways in commercial kitchens is relatively poor. In this contribution, we extend our understanding of how FOG is perceived and managed by those working within food service establishments (FSEs). A questionnaire (n = 107) exposes awareness of and experiences with FOG and characterises two important behaviours: kitchen appliance cleaning regimes and waste management practices. Findings demonstrate that awareness of issues caused by FOG in sewer networks is independent of job role or position and that a majority of respondents (74%) are acquainted with the impacts of poor FOG management. Application of a risk ranking approach revealed a low risk of emissions from waste frying oils and exposed behaviours which can serve to reduce FOG emission potential including pre-rinsing of plates and cleaning of fryers and extraction hoods. Critically, 69% of FSEs had no means of managing their FOG emissions. We conclude that sampled FSEs were generally unaware of the relative contribution of FOG sources, thereby limiting their ability to respond to the behavioural and technological options available for minimising its impact. The risk ranking developed in this paper could be used to suggest efforts to reduce and mitigate FOG emissions from FSEs.