FOG – Fat, Oil & Grease

Fat, oil & grease (FOG) is a waste by-product of food production that enters the drainage network as a result of poor practices when performing washing activities in both domestic and commercial kitchens. FOG is a major contributing factor to sewer overflow. FOG is an international problem costing millions of euros to municipal authorities each year. In the UK alone, it is estimated that FOG costs the local authorities up to 79 million euro a year. A 15 tonne “fatberg” – a lump of fat and grease – removed from the London sewers in 2013 highlights the nature and size of the FOG problem in urban sewer lines.

Up to 50-70% of in-line sewer blockages are attributed to FOG as it accumulates and hardens in the sewers as the temperature decreases.  To combat the volume of FOG entering its sewer system from Food Service Outlets (FSOs), Dublin City Council introduced its FOG Prevention Programme in 2008. Under the programme, FSOs are required to install and maintain properly sized grease trapping equipment, dispose of all FOG using permitted waste hauliers only and introduce best management practices (BMPs) onsite to reduce the quantity of FOG entering the drainage network. This programme appears to be one of the most successful in any city worldwide. 

A number of research projects have been funded on this topic, the most recent being a Fulbright Award (TechImpact) received by Dr Tom Curran, a lecturer in UCD School of Biosystems and Food Engineering and Director of the MSc Environmental Technology Programme at University College Dublin. As a Fulbright-TechImpact Scholar, he will be hosted by Professor Joel Ducoste at North Carolina State University to develop an early warning system for sewer network blockages. In recent years, Dr Curran has developed a European wide reputation as a specialist in 'fatbergs' and has made frequent media contributions on this issue. The Fulbright Award builds on two projects (outlined below) that have been previously funded by the Irish Research Council and Noonan Services Group in partnership with Evolution Environmental Services as part of the Employment Based Postgraduate Research Programme.

DubFOG Research Project: Critical evaluation of Dublin City Council’s Fats, Oils and Grease (FOG) Programme and an investigation of the potential to implement similar initiatives internationally.

Principal researcher: David Gibbons.

The aim of this project is to review the progress of the FOG Prevention Programme since implementation in 2008 and to develop a mapping tool that highlights areas of risk for use by environmental inspectors and asset managers in the daily operation of the programme. A study has been undertaken on a catchment of 160 FSOs (c. 7% of all FSOs in Dublin City); this has found that approximately 100,000 litres of grease trap waste and 170,000 litres of used cooking oil waste are prevented from entering the drainage network in this area annually.

NatFOG Research Project:  Development of a National Strategy for Recovery and Utilisation of Fats, Oils and Grease (FOG) from Food Service Outlets (FSOs).

Principal researcher: Tom Wallace.

Having quantified the rate of production of FOG waste in  Project 1, the current approach for the disposal of this waste will be assessed to determine how effectively this resource is being exploited. The objective of this project is to evaluate the production and consumption cycle of FOG waste in the food service industry. This includes an assessment of the current trends in FOG waste prevention and segregation, and the design of processes and strategies for the utilisation of the high energy potential of the waste as a resource.


Wallace, T; Gibbons, D; O'Dwyer, M; Curran, TP (2017) 'International evolution of fat, oil and grease (FOG) waste management - A review'. Journal of Environmental Management, 187:424-435. Link

UCD School of Biosystems Engineering Research Review 21: ‘Fat, Oil and Grease (FOG) utilisation trends in Dublin’. Full book of research reviews available at:

November 2015: Sutainability Ireland article by Dr. Tom Curran ‘Sustainable Management of Fat, Oil and Grease Waste – A Global Challenge’, http://researchrepository.ucdie/handle/10197/7212

10/08/2015 The Guardian article by Ian Wylie ‘Fighting the fatbergs: how cities are waging war on clogged sewers’. Link.

UCD School of Biosystems Engineering Research Review 20: ‘Development of a national strategy for recovery and utilisation of fat, oil and grease (FOG) waste from food service outlets (FSOs)’ and ‘Assessing Dublin City Council’s fat, oil and grease (FOG) programme through grease trapping system (GTS) installation and maintenance’. Full book of research reviews available at:

25/04/2015 Dave Fanning 2FM radio interview  with Dr. Tom Curran regarding FOGwaste & fatbergs, here.

Abstracts submitted to the Environmental Science Association of Ireland’s Environ 2015 conference: ‘Assessing the efficacy of Dublin City Council’s Fat, Oil and Grease (FOG) Programme through the quantification of FOG waste recovered’ and ‘Development of a National Strategy for Utilisation of Fats, Oils and Grease (FOG) Waste from Food Service Outlets (FSOS)’. Full book of abstracts available here.

SSSE 2014 abstract ‘Developing GIS maps to monitor sewer blockage risk from fats, oils and grease (FOG) in Dublin city’:

UCD School of Biosystems Engineering Research Review 19:




Project Team

The Project Manager is Dr. Tom Curran,, UCD School of Biosystems Engineering, UCD Agriculture and Food Science, University College Dublin, Belfield, Dublin 4.

The Principal Researchers are David Gibbons,, and Thomas Wallace, UCD School of Biosystems Engineering, UCD Agriculture and Food Science, University College Dublin, Belfield, Dublin 4.

The Employment partner is Michael O’Dwyer, Evolution Environmental Services, The Guinness Enterprise Centre, Taylor’s Lane, Dublin 8,


These studies have been funded by:

The support of North Carolina State University, Dublin City Council and Irish Water is also acknowledged.



Noonan ESS