AMDEA response to consultation on the transposition of the revised Waste Framework Directive (Directive 2008/98/EC) in England and Wales

15 September 2010

We would like to take this opportunity to reiterate our view that any target for separate collections of household waste should acknowledge the potentially crucial role of domestic food waste disposers (FWD).

AMDEA agrees that anaerobic digestion (AD) is the process that recovers most value from food waste.  However any contingent suggestion that separate, additional, kerb-side collection is the only available option for delivery would be misleading and counter-productive.  Research for Herefordshire and Worcestershire CC found that the global warming potential (GWP) was the same whether food waste was delivered to AD by trucks or via FWD and sewers.  The GWP of centralised composting of incineration was worse.

Relying on separate collection alone will inevitably not capture all food waste and is likely to lead to cross contamination of other [dry] recyclables.  Householders often cannot (and in many cases will not) separate food waste efficiently and storing it for collection presents problems of space and hygiene, particularly in multiple occupancy [flatted] dwellings.

Domestic food waste disposers deliver this waste stream from the kitchen sink directly to the wastewater treatment and AD plants.  The majority (by weight) of sewage sludge is treated by AD and that proportion is increasing.  Only 6% of homes in the UK currently use domestic food waste disposers to prepare and transport this waste stream.  However, requiring minimum effort and no storage, it has proved the most efficient mode of delivery to AD in Surahammar, Sweden, where given sufficient incentive, peer-reviewed research (to be published later this year) has shown that when 50% of households adopted this mode of delivery the average annual biogas increased by 46% (P=0.01) but the flow, BOD, N and ammonia decreased, though this was not statistically significant.  Benefits have proved to be both environmental and economic.  Using the existing sewerage system avoids any need for additional refuse collection vehicles that would increase traffic congestion, fossil fuel consumption and vehicle emissions.  Enriching the sewage sludge has produced a 46% increase in biogas production.  No additional costs have been incurred in waste water treatment and over a 10 year period the sewage system has recorded no increase in blockages, or build up of fats oils or grease (FOG).  This research is in print for publication in the UK later in 2010 and advance copies of the detailed results can be provided.

In the light of current life cycle assessment methods and the growing body of  international experience and research on the longer term use of FWD, major cities that were previously reluctant to promote FWD are now adopting them - New York and Stockholm are two examples; Herefordshire and Worcestershire have promoted and subsidised FWD as has Capri in Italy.  In New Zealand FWD are promoted by environmental authorities and have 34% penetration, Australia has 25% and nationwide usage in the US is 50%.  In Anaheim, California 93% of homes use FWD and none of these authorities has reported problems in the wastewater treatment systems as a result of this widespread use.

FWD are popular with householders because they are the simplest, cleanest solution and require no change of behaviour.  Once installed, they are a permanent solution and remain in the property if householders move.  In contrast to their potential to increase the sustainable energy yield of AD plants  by 78 kWh electricity per FWD per year , they consume only 3–4 kWh of electricity a year.  This equates to adding about 32p per year to a household electricity bill.  Water usage is also low - at less than 6 litres per day, this is comparable to one extra flush of the toilet.

Resistance to FWD in the UK is primarily driven by lack of familiarity with their use and with the scientific evidence about their efficacy.  Some of the UK’s water companies are against the fitting of FWD because they believe that mixing finely ground food waste with existing sewage might cause blockages, increasing their maintenance and sewage processing costs.  However, scientific evidence and experience in other countries with a high concentration of FWD is proving these fears unfounded.

As Government and local authorities face vast investment challenges to meet environmental targets and recover value from food waste, FWD is an important underutilised option, with proven potential to make environmental gains in densely populated urban areas.  A key element in achieving the target of 50% of household waste recycled by 2010 will be to determine ways of doing this that are “technically, environmentally and economically practicable”. 

There is growing evidence that FWD can be part of that solution.