What Lurks Beneath

A new word has entered my consciousness.

Fatberg. 

It relates to the heaving, sick smelling, rotting mass of filth and faeces all nicely congealed together in cooking oil, fat, grease and lard and to be found collecting in our subterranean drains and sewers.

Householders and businesses have always tended to pour used cooking oils and fats down the sink but this has become an increasingly severe problem where these glutinous materials are trapped and can cool and accumulate by the presence of blockages caused themselves by discarded wet wipes, sanitary products, condoms and other non or slowly degrading everyday domestic products.

Fatbergs build up at pinch points in the ageing sewers under our urban centres and have in some cases grown to huge proportions. 

The London Borough of Kingston upon Thames recently undertook a three week project to disperse a 15 metric tonne fatberg that had taken up 95% of a 2.4 metre diameter sewer pipe. They were alerted to a problem with residents having difficulties flushing their toilets but will not have been expecting the actual cause. Had the solidified grease and oil not been found and removed then the Borough will have been at very real risk of drain back flow and major sewage flooding in the housing stock.

London does have a particular problem because of the density of households and also some of the highest concentrations of food outlets in the country. An estimated 32 to 44 million litres of various oils are used in the various processes and with a high proportion of this, after use,  poured down the drains.

The Thames Water Authority which is responsible for 59,000 miles of sewers has to clear 40,000 blockages every year as a direct consequence of restaurants and residences adopting such practices. Under conventional fat busting clearance by specialist companies using power washers the fatty wastes when reduced to a more manageable size are simply confined to landfill.   It may be difficult to re-educate the offenders and so a more innovative and practical approach is required. 

The global fast food chain, McDonalds, retrieve more than 600,000 litres of its own used cooking fat in London alone and this is converted into bio diesel to run half of its fleet of trucks. 

Local Councils are also interested in this type of initiative and even the former London Mayor, Boris Johnson saw the possibilities of running one fifth of the London Transport bus fleet on bio fuel from discarded oils and fats.

An energy company has plans to burn waste fat, oil and grease in order to generate enough electricity to power 39,000 homes. 

In a pilot scheme one bio fuel company was able to remove 30 tons per week of fatbergs from a water treatment plant in Birmingham which if extrapolated to the 9000 such plants nationwide shows the potential for a sustainable source of raw materials. 

Solidified grease can be harvested from fat traps in hospitals, stadia and from factory kitchens as well as food manufacturers and catering outlets. The process to isolate the valuable fats is not a pleasant one as the fatberg is a combination of typical sewage constituents and general waste. 

Gentle heating of the fatberg under controlled conditions in a purpose built complex is the first step followed by progressive filtering out of the nasty elements before a sawdust layer removes the finer impurities. The end product which can then be converted to bio fuel is actually a sweet scented liquid which is a remarkable outcome considering the steaming and stinking mass which was the starting point. 

In this way just one company hopes to be able to produce 90 million litres of bio fuel per year which by way of illustration of their ambition was the total consumption of that type of fuel in the whole of 2016.

As the clamour for commercial gain increases so will reliable sources of the new “off white oil”. There will have to be a more technological and clinical approach for prediction and exploitation where the fatbergs are likely to form. 

One initiative is the detailed mapping of drains and sewers to identify the volume and frequency of common blockage points beneath our streets so that these can be promptly harvested. 

This would suggest that there may be scope for actual encouragement and even the incentivising of individuals and business to continue dumping their oils, fats and lards down sinks and drains rather than making it into the undesirable and anti-social action that it really is.