Composting in the UK
Current status and future perspectives
J Gilbert
1. Introduction
The UK composting industry has come a long way from its humble origins a decade or so ago, with The Composting Association's annual surveys indicating that the overall picture is one of continued expansion. The latest survey (carried out last year by the Open University on behalf of the Association) suggested that composting increased by approximately 23% between 1998 and '99. Based upon respondents' returns and trends over recent years, it is anticipated that the UK was on course to compost one million tonnes of material during 2000 (see Figure 1).
Figure 1 - Mass of materials composted in the UK
Source: Slater & Frederickson (2001)[1]
2. The 'drivers' for change
There are a number of 'drivers' that are set to influence the collection and composting of organic wastes in the UK. The EU Directive on the Landfill of Waste (1999/31/EC) has laid down challenging targets, requiring the UK to divert increasing quantities of biodegradable municipal wastes from landfill from 2010 onwards. The respective national waste strategies have identified the importance of recycling and composting, with the Statutory Performance Standards in England, in particular, setting binding targets for the first time.
Of particular relevance, however, is the working document on the 'Biological Treatment of Biowaste' published by the European Commission[2]. The second draft (February 2001) promotes the source separation of organics (or 'biowaste'), differentiates between 'compost' and 'stabilised biowaste', and sets out strict processing and compost quality criteria. It seems possible that this document will form the basis of a Directive on the biological treatment of 'organic' wastes in the future.
Such drivers will inevitably result in greater quantities of organic wastes being diverted from traditional disposal routes, of which composting is set to form a mainstream treatment option. It therefore seems likely that significant changes will need to be made over a short timescale, setting considerable challenges for the UK to meet. Four fundamental questions thus need to be addressed, namely:
- How should the organic wastes be collected?
- What methods should be employed to process the feedstocks?
- Will sufficient facilities be established in time and how should they be regulated?
- How should composts be used and how sustainable will the market sectors be?
Most of these issues will be addressed by the Rapporteurs in their respective papers, and during the workshop itself. The following narrative provides a brief summary of the talks and raises a few challenging questions that could be used as the basis for debate by the workshop participants.
3. Feedstock collection
There are a number of ways in which organic wastes can be collected. This can either involve separation at source by the waste producer, or down stream, involving complex separation systems to remove the organics fraction from the residual waste fraction. Bring schemes (for example, at civic amenity sites and recycling centres) form the mainstay in which green wastes from households are collected in the UK at present.. These usually comprise clearly labelled, dedicated skips or roll-on, roll-off containers. Household kerbside and commercial waste collections can employ a number of different methods, which include the use of wheeled bins in different sizes (140 l, 240 l, 360 l) and types (standard, vented, split) and biodegradable bags made out of either kraft paper or plastic polymers. Householders may need to opt in, opt out, or participate on a voluntary basis. Collection schemes may be integrated with an existing collection service, or set up as an additional round.
Collecting organic wastes separately has a number of disadvantages in that it will necessarily incur additional costs, as extra collection schemes are required. It also relies upon a change in peoples' habits, and issues, such as odours, flies and hygiene, all need to be addressed. Despite these challenges, source separation is seen as a necessary pre-requisite in order to produce good quality composts, as the level of contamination in feedstocks is significantly reduced and the appropriate quality control mechanisms can be set in place. Composting as a waste treatment process will only succeed in the long-term if sustainable markets are secured (that is it also needs to be a successful product manufacturing process). As agriculture has by far the greatest potential, endorsement by this sector is essential, as it is both unable and unwilling to risk using "dirty" materials, especially where food and fodder crops are involved.
In his paper "Successfully introducing a source separated collection scheme for household organic wastes - the Dundee experience" Alistair Lamont describes his experiences of introducing the UK's first source separated wheeled bin ("Compostainer") collection scheme for household organic wastes in the city of Dundee. Mr Lamont describes the current status of the scheme - which has been in place for eight years - and outlines the ideal conditions for obtaining good quality compost feedstocks. He then discusses the methods used in Dundee to introduce a successful collection scheme.
Mr Lamont suggests that some households may be unsuitable to participate in the scheme, and suggested that it should be voluntary. This therefore raises the following questions:
- What housing types and socio economic areas are suitable for separate collection schemes and how can they be identified?
- How can continued participation be encouraged and maximised?
It is also suggested that introduction of the scheme reduced the quantities of residual waste for collection, however:
- What are the true costs of implementing such separate collection schemes? Are these, in conjunction with processing costs, less than potential fines that the EU may impose for failing to meet the Article 5 Landfill Directive Targets?
- Does the use of wheeled bins lead to an overall increase in wastes collected by the local authority?
The issue of source separation and its associated difficulties are highlighted by Dr Jerry Avis (Excelar Ltd) in his paper "Mixed MSW Composting - A Short Term Solution with a Future". Dr Avis discusses the need for the UK to adopt mixed municipal solid waste (mMSW) biostabilisation processes as an interim measure within an integrated waste management strategy before the UK makes a transition towards more widespread implementation of source separation schemes.
Dr Avis acknowledges that organic wastes separated at source produce inherently better quality composts than un-segregated feedstocks, however, this raises a number of questions regarding mMSW-derived materials, namely:
- For what purpose are they fit for?
- Will sufficient market sectors be available for these materials?
The issue of public acceptance and risk perception remain important considerations.
- Should, mixed waste materials (stabilised biowaste) remain a 'controlled' waste, rather than a marketable product, as implied in the Working Document from the European Commission?
- What would be the implications of such a policy (or perhaps more pertinently, what would be the implications of not controlling these materials)?
Dr Avis suggests that mMSW composting could lead to a "Rapid contribution to Government Targets".
- Would mMSW processes count towards the Best Value Performance Indicators for 2003 / 04?
- How quickly could such mMSW treatment facilities be established?
4.Processing and regulation
There are a number of composting options available, which allow local authorities to take a flexible approach. These could employ decentralised on-farm sites, coupled with the use of large-scale centralised composting facilities and smaller home composting promotions. Community-run and on-site composting both have important roles to play. There is also a choice of system (such as open-air turned-windrows, forced aeration and in-vessel systems), depending upon waste types and local issues. This enables a flexible approach to be adopted.
In his paper "Development of Soil Making Materials from Municipal Solid Waste: An Alternative to Established Composting Techniques", Chris Barker sets out the case for processing mixed MSW through a technique referred to as 'In situ Soil Stabilisation' (ISS). Such a process differs from that traditionally recognised as composting, and is described as "the controlled decomposition of effectively segregated BMW [biodegradable municipal waste] in an aerobic environment". It is reported to have been used effectively at various sites within England for creating soils in forestry, conservation and public amenity.
Mr Barker suggests that the diversion of biodegradable municipal wastes from landfill is currently hindered by the requirement for 'high quality' composts, which are not always necessary in certain applications. In his paper he argues that the waste industry should not be forced to follow the route of producing high quality composts, rather, materials should be tailored to the market's requirements (comparison was made with the problems currently experienced by the retailer Marks and Spencer). This thus raises the following questions:
- Should environmental protection be forsaken for consumer pressures, in which case, what does the consumer really require?
- What control measures should be set in place to ensure that the environment and human, animal and plant health are not harmed (for example, to prevent lower grade materials being applied to food or fodder crops that might enter the human food chain); how should this be 'regulated'?
Mr Barker raises the question of MAFF's interpretation of the 1999 Animal By-products Order[3]. The thermophilic composting process has been demonstrated scientifically to sanitise and stabilise biodegradable materials, and is a recognised treatment option for a range of materials, such as biosolids. In the USA the Environmental Protection Agency developed its Part 503 Regulations and its Processes to Further Reduce Pathogens[4]. In the light of the continuing outbreaks of Foot and Mouth Disease (at the time of writing):
- How would the ISS process ensure appropriate pathogen destruction?
- How would wild birds be prevented from gaining access to so-called 'catering wastes'?
A novel composting technique is described by Bill Butterworth in his paper "Experience in deep clamp composting - low cost recycling without pollution". This is portrayed as a small-scale decentralised process that can be carried out by farmers, who can use the resultant compost on their own land.
Mr Butterworth describes the process and argues that conditions within the clamp do not result in leachate because, if set up correctly, then nutrient flow will be balanced; reference is made to recent work carried out by the Environment Agency. Given that there are very little published data in the scientific press about leachate quantity and composition:
- To what extent does precipitation (such as rainfall) affect the potential for leachate production in the clamp?
- What data are used to support the assertion that leachate is not produced? How would this be used to carry out a risk assessment, such as that described by the Environment Agency[5]?
The deep clamp process described is aimed at the farming community. Given the recent difficulties this sector has faced and the concerns about applying perceived "waste" materials to land:
- What monitoring and record keeping activities are carried out to ensure that sanitisation has been carried out appropriately and that any resultant compost applied to land would meet the strict demands of the farm food assurance schemes?
5. Markets
Composting is not only a waste management operation; in most cases it is also a product manufacturing process. As such, the success of the composting industry relies upon the establishment of sustainable markets for composts.
In his paper Trelawney Dampney discusses "Markets for Compost - Are they Sustainable?" He describes some of the major market sectors and provides estimates of the potential quantities that might be met by composted materials. Reference is made towards developing new markets and how the potential use of composted materials as daily landfill cover may hinder market development. This therefore raises the following questions:
- How can the markets for composts be expanded through initiatives such as the Waste and Resources Action Programme, the various ReMaDe projects across Britain and International Composting Awareness Week?
- What qualities do the market sectors require and how important are quality standards?
- How can fiscal measures help promote the marketing of composts?
Mr Dampney also raises the issue of the use of biostabilised materials.
- Will the increase in availability of 'biostabilised materials' (as also suggested by Dr Avis) have the potential to 'undermine' the marketing of 'composts'?
6. Summary
The Rapporteurs have collectively addressed the four main priority areas in their papers, namely: collection, processing, regulation and marketing. It will be interesting to see the outcomes of the respective workshops and whether the participants managed to reach a consensus view on what are currently topics of considerable interest.