What are fatbergs and what can be done about them?

All food service businesses in St Andrews are to receive visits from environmental officials as Scottish Water tries to cut down on the problem of fatbergs.

– What are fatbergs and what causes them?

Fatbergs are large lumps of fatty gunk in the sewer system which can set as hard as concrete. They are caused by fat, oil and grease (FOG) being disposed of incorrectly down sinks and drains, and then accumulating over time. They may combine with other items which should not have been flushed away, such as wet wipes and sanitary products.

– But aren’t the oils in liquid form?

Fat, oil and grease in liquid form may not appear to be harmful but they congeal when they cool down. Whether it is saturated fat, like lard, or mono-unsaturated fat, like olive oil or vegetable oil, they all congeal and harden.

– What damage can fatbergs do?

They can cause blockages to the inner lining of drain pipes, which can lead to waste water flooding into gardens and properties, causing a health hazard to wildlife and the local environment. The waste water drain that runs from your house to the public sewer is usually only about four inches wide, meaning that problems can accumulate quite quickly. In extreme cases, blocked sewers can spill into burns, rivers, streams, coastal waters and beaches, causing further environmental damage.

– How big can fatbergs become?

A giant fatberg was discovered in a London sewer last year. The “monster” fatberg, weighing more than 10 double-decker buses, had clogged up a stretch of Victorian sewer under the busy Whitechapel Road. It was 250 metres long, more than twice the length of the Wembley football pitch, or just under four times the length of a Boeing 747.

– What is the financial cost of dealing with fatbergs?

Scottish Water deals with 37,000 blockages every year, costing £6.5 million to attend and clear. The utility says that more than half of all the blockages in Scotland’s sewers are caused by FOG.

– What can go into the drainage system?

Water bosses stress that only human waste and toilet paper should enter the sewers. Environmental campaigners say that people should think carefully about what we put down the drains, avoiding items such as wet wipes and cotton buds, as well as fats. Cooking oils can be recycled into valuable products such as biofuels.

– What does the law say?

It is an offence under the Sewerage (Scotland) Act 1968 to interfere with the free flow of the sewers. Under the Waste (Scotland) Regulations 2012, urban food businesses, such as cafes, restaurants or takeaways which produce more than 5kg of food waste per week, also have to present food waste separately for collection unless excluded by a rural location.