AMDEA response to Defra Review of Waste Policies 

6 October 2010

All our members are fully committed to reducing waste and encouraging recycling but we have some member companies with a particular interest in the segregation of food waste as they manufacture domestic food waste disposers (FWDs). These companies have compiled an evidence base of scientific studies into alternatives to landfill and an accumulation of practical experience of household use of such devices around the world.

AMDEA also joined the National Food Waste Programme and contributed funding for their research into the impact of FWDs on waste water treatment. Regrettably we have not seen any reports and no data have yet been published. However we are awaiting publication of results from a 15 year research programme from Sweden which is due out later this year.

In the meantime this call for evidence represents an ideal opportunity for Defra to consider seriously the viable options for achieving the objectives of reducing waste to landfill and particularly how to address the difficulties of dealing with the household waste stream.

Food waste is a particular problem, given its potential health hazards and the fact that its mixed nature makes it difficult to store and transport, and costly to process. The promotion of separate kerb-side collection of food waste in isolation would be to waste this opportunity to look at alternatives to local authority collections which are already generating adverse publicity in terms of their complexity and cost.

Kerbside collection of food waste is particularly costly for local authorities with the need to provide additional storage containers, additional collections, extra street cleaning and payment for treatment facilities.

Extra kerbside collections add to traffic congestion, pollution and fossil fuel consumption as well as noise while the storage of food waste poses significant health and nuisance issues.

Domestic food waste disposers that fit under the kitchen sink offer a convenient and easy solution, particularly for flats, densely populated urban areas and sparsely populated rural areas. Unlike the compost heap they take virtually all food waste and grind it into minute particles that go directly into the wastewater system and on to wastewater treatment and anaerobic digestion (AD) plants.

There were at one point concerns that FWDs might increase the incidence of sewer blockages and/or add to the build up of fogs, oil and grease (FOG) but research has demonstrated that these fears are unfounded. Even in areas where some 50% of households use FWD there has been no change in the hydraulic loading of collection systems or increase in blockages. In Anaheim in California 94% of households have FWDs and its incidence of sewer blockage is comparable to any other city of similar size.

The addition of food waste has been proven to enrich sewage sludge and enhance its value: when processed by anaerobic digestion. It may even improve the quality of the resulting digestate which can then be used as fertilizer or soil improver.


2.3 The Government’s approach to waste.

What should the nation’s ambition for waste management be?

AMDEA supports efforts to encourage consumers to reduce the amount of food that they throw out but it is inevitable that there will still be a percentage of food waste jettisoned for public health reasons and this waste stream should, wherever possible be recovered and treated for reuse.

The simplest method of recovering food waste is the use of a food waste disposer (FWD) that is connected to the sewerage system leading to treatment at a wastewater treatment plant, where it can either be treated and then used as fertiliser on agricultural land, or can first be used for the production of biogas via anaerobic digestion (AD).

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, in Surahammar, Sweden, where 50% of households have FWDs, research to be published later this year shows that the average annual biogas production has increased by 46% compared with when there were no FWDs.

The local authority has also saved the costs of kerbside collection, transporting the waste to the treatment site and treatment. Over a 10 year period there have been no additional costs for wastewater treatment, the biogas produced has increased by 46% and there has been no reported increase in smell, blockages, or FOG. Overall Surahammar’s waste strategy has decreased the tonnage of waste to landfill from 3600 tonnes in 1996 to 1400 tonnes in 2007. This research will be published in the UK later this year and advance copies can be provided 1.

FWDs enable food waste to be separated at source easily and conveniently and transported for treatment using existing infrastructure. Policies for sustainable food waste management need to be adapted to people’s behaviours and expectations if they are to be successful.

How could the contribution waste management in England makes to the economy and our environmental and energy goals be maximised?

A study of FWD use in Hereford and Worcestershire showed that for every tonne of food waste diverted from landfill (capturing biogas for energy and re-using bio solids for land) almost one tonne of CO2 equivalent emissions is avoided; attributing a negative carbon footprint or carbon credits to this method of food waste management 2.

Internationally several major cities that were previously reluctant to promote FWDs are now adopting them - New York and Stockholm are two examples. In the UK Herefordshire and Worcestershire have promoted and subsidised FWDs, as has Capri in Italy. In New Zealand FWDs are promoted by environmental authorities and have 34% penetration, Australia has 25% and nationwide usage in the US is 50%. In Anaheim, California 94% of homes use FWDs and it is important to note that none of these authorities has reported problems in the wastewater treatment systems as a result.

Another economic benefit of using FWDs is the increase in biogas production. The Directive on Energy from Renewable Sources acknowledges biogas from sewage treatment plants as a renewable energy so biogas from waste water treatment plants can contribute to both national and European energy goals as well as offering potential income from sales of electricity or biomethane.

Other economic and environmental benefits include the option to recycle biosolids as fertiliser. As well as containing the nutrients that were embodied in the food waste the organic matter contributes to improving soil structure and cultivation, as well as water-holding capacity, water infiltration and soil aeration.

Another benefit is that by separating wet food waste FWDs make the recovery of solid waste; particularly dry waste much easier, thus reducing costs and increasing energy efficiency.

In terms of the energy required to run FWDs, this is negligible. Domestic FWDs typically have a 350W – 500W motor. Field studies show usage averages 2.4 times per day for 16 seconds per use, equivalent to an annual electricity consumption of about 2-3 kWh/household per year. At the current average UK electricity prices quoted by the Energy Saving Trust this adds approximately 30p per year to a household electricity bill. As for water consumption, studies show that FWDs use as much water as one modern toilet flush (6 litres) per day.3 kWhe/household, i.e. 25 times more than is used by the FWD. Compared with thermal electricity generation there is a net annual benefit of 3900 litres of water and 40 kgCO2e per household.

A study from the New York City Department of Environmental Protection concluded that the impact of FWDs on the sewer system was insignificant.4 Since food waste is 70% water and essentially has the same, or lower, specific gravity as human waste,5 the design of sewers is therefore compatible with sediment-free transport of food waste particles.

FWDs encourage more separation of food waste because they are easy to use and the waste is instantly removed, unlike compost bins or “slop” buckets. Once installed FWDs remain in the property even when the householder moves. In Germany the level of physical contaminants in kerbside bio-waste is reported to have increased from 4% to 20% as citizens’ enthusiasm for diligent separation has declined.6

2.5 Preparing for Reuse and 2.6 Recycling

Post-collection separation of dry recyclables is compromised by contamination with wet, sticky, putrescible food waste. FWDs separate food waste at source, in the kitchen. They remove food waste from the waste stream. They grind the waste, they do not chop it, so plastic film, metal and other undesirable physical contaminants remain in the grind chamber. One solution will not fit all situations or individuals; some people will prefer to home-compost, others are happy to have a wormery, others tolerate kitchen caddies but a substantial number of households are unable or unwilling to use any of these and a FWD offers a viable alternative.

Motivating people to recycle more is complicated and generally the more simple, convenient, clean and appropriate to their household it is, the more likely it is to succeed.

There is some scope for financial incentives - in 1997 Surahammar introduced new tiered waste charges with food waste rates being £0 per year for home-composters, £27 per year for an 8-year leasing contract for a FWD installed by the municipality and £209 per year for kerbside collection of kitchen waste. By late 1998 30% of households were using FWD, in 2008 this had increased to 50%, 30% were home composting and 20% had kerbside collection. There were also drop-off bins for cardboard, glass, plastic and metal. Waste to landfill was cut from 3600 to 1400 tonnes/year. While the treatment plant’s biogas increased by 46% the load to treatment did not change and it was suggested that the dissolved load was biodegraded by bio films in the sewers, whereas particulate food particles passed through to the anaerobic digester.

2.7 Energy recovery

Biogas, biomethane and heat from sewage treatment plants are acknowledged sources of renewables. The value of energy recovered from food waste going through FWDs is that transport to the treatment plant and AD processors uses existing infrastructure. There is no further environmental impact or added carbon cost. The majority of sewage sludge in the UK is treated by AD and the proportion is increasing. The flow to AD, from FWDs via the sewage treatment plant is consistent and predictable - there is no speculative element required in projecting the AD capacity demands.

In Milwaukee, Wisconsin, people are actively encouraged to increase the food waste they put into their FWDs because the Milwaukee Metropolitan Sewerage District (1.1 million people in 28 authorities over 411 square miles) uses anaerobic digestion. In 2007, the district saved $1.9million in energy costs from methane generated by its wastewater treatment plants.

2.8 Disposal

The experience in Surahammar shows that including FWDs as an option for householders reduced the waste sent to landfill to 40% of the amount sent before the strategy was deployed.
Half the residents now use FWDs while 30% have home composting and only 20% use the kerbside collection for kitchen waste.


Including FWD in the mix of options is consistent with the Government’s overall objectives.

Using existing infrastructure means that there are no additional costs at a time when we are attempting to reduce our public expenditure.
FWDs encourage separation of food waste by people who might otherwise be unable/unwilling to participate.

They help to convert food waste to renewable, base-load energy and nutrient-rich soil improver.

Separating wet, putrescible food waste increases the yield of dry recyclables and/or energy.

The environment is protected and natural resources conserved because of a net reduction in global warming potential of about 1 tonne CO2e/t food waste; the nutrients in food waste can be recycled to land (especially important in the case of phosphate); renewable energy can be generated and water usage reduced.

They contribute to sustainable local options to deal with waste but also aid the sewerage undertakers

They help to reduce the greenhouse gas emissions from landfill and contribute to the UK targets for carbon emissions, renewable energy generation and diversion from landfill.

And finally, FWDs have a very high user satisfaction rate, in contrast to the adverse publicity that has greeted some centrally imposed kerbside schemes.