How to solve the 'monster' fatberg problem
Fatbergs – enormous solid masses of oil, grease, wet wipes and other hygiene products that congeal together to cause major blockages – are wreaking havoc on the sewers of cities around the world. A 130 tonne specimen described as a "monster" recently caused backups in sewers in London's Whitechapel, and the cities of Baltimore, Singapore and Dannevirke, New Zealand have also all experienced similar issues in recent weeks.
Fatbergs are not a recent phenomenon, but have attracted increased attention in recent years as old sewerage systems struggle to cope with an increased consumption and disposal of everyday products like fats, oils and greases from cooking. This is a particular issue for cities like London with Victorian systems. The visceral disgust that runs alongside the image of fatbergs lingering under the city, and the potential impact they will have on local flooding, means that they will remain a topic that demands attention.
Strategies are already being put in place in order to prevent sewer fatbergs. Current water industry tactics tend to focus on removing sewer blockages and reducing the fats, oils and greases that enter sewers from commercial sources (such as restaurants). But around three quarters of the fats, oils and greases in sewers comes from domestic sources, making household disposal a key priority for change.
Awareness campaigns directed at the public currently focus on what people put down the kitchen sink. Current advice is that cooking fats, oils and greases should be disposed through food or solid waste recycling. But there is little information on how we can dispose of other products – like that fatty off milk at the back of the fridge – without pouring it down the sink. The mucky complexities of how people actually deal with fats, oils and greases in the home suggests that the solution might need to be more complex than awareness campaigns.
In a recent report we suggest that changing people's broader behaviour related to food waste and disposal of fatty products is not going to be easy to change – and that we also need to look beyond the plughole.
Down the plughole
Fats, oils and greases are changeable, often smelly, visceral materials. The way we dispose of them is tied to attempts to reduce their impact on our kitchens and in our lives, and this becomes entrenched in our everyday habits and routines.
They can be troublesome materials to handle. The fact that they are liquid at cooking temperatures, and often at room temperature, makes them simpler to dispose of via liquid waste than via solid waste channels, yet their tendency to solidify and accumulate in the specific physical and chemical conditions of drains and sewers makes this disposal highly problematic. Fats, oils and greases are not only difficult to deal with, but many also find it unpleasant.
Evidence from research into food waste and disposal suggests that when food begins to deteriorate, its material properties – and the bodily reactions caused by its appearance, smell and feel in the people handling it – play an important role in how it is discarded. The more effectively and reliably it can be sealed off and ejected from the home with minimal human contact, the better.
Our research suggests that if the same is true of householders' reactions to leftover fats then successful interventions to divert fats, oils and greases from sewers will mean providing an alternative, yet similarly effective, option for quick and seemingly hassle-free disposal than the kitchen sink.
These ideas of disgust, dirt, smell, and convenience are also likely underpinning similar dynamics for the disposal of wetwipes, nappies, and other hygiene products down the toilet rather than the bathroom bin.
Beyond the kitchen sink
But crucially, fats, oils and greases do not end up in our sewers purely due to decisions related to disposal at the kitchen sink. Rather, actions throughout the stages of food provisioning – including shopping, food preparation, cooking, dealing with leftovers, and clearing up – leads to fats, oils and greases entering sewers.
Another way of thinking about the issues is in regards to tracing the numerous decisions that occur in the process of carrying out routine household tasks: moments in which resources are used up and waste is produced. This is broader than just individual behaviours and involves a consideration of all of those moments where waste fat is indirectly or directly produced – such as when we are choosing what to cook; how much oil to use; whether to reuse that rendered meat fat from the Sunday roast in the next meal we cook or discard it.
Insights into what shapes behaviour at these points lead to a range of implications and recommendations for policies and intervention programs. For example, there needs to be a recognition that disposal of products like fats, oils and greases is part of a wider set of kitchen practices that are in turn shaped by wider systems of food provision (supply chains, retail, and so on) as well as waste disposal facilities.
Interventions that influence household behaviour therefore don't just need to target the household but could involve product innovations that reduce likelihood of excess fat oil and grease production – for example, fryers that use less fat. Retail environments and packaging could be used as means of changing social norms. Sewerage systems could be rethought. Effective alternative waste fat and oil disposal infrastructures could be envisioned.
Rather than fatbergs just being seen as a water industry issue there needs to be greater collaboration across sectors (water, energy, food) to deal with the problem. Potential solutions need to range from the level of the household right through to new infrastructures that are experimenting with turning this mucky fatberg problem into energy and biofuel.