Waste composting compensation

Most composting operations involve the composting of vegetation and vegetable waste and bark. The waste is generally stored for ‘bulking up’ prior to shredding. It is then composted in elongated rows known as ‘windrows.’ The process can take some 10 to 16 weeks depending on the required quality of the final compost. As part of the process the windrows need to be aerated from time to time. This is done by turning them often using machinery. Once the composting process is complete the material is often screened to size it and remove unwanted material and it is then stockpiled.

Problems sometimes occur if a windrow (a row of composting waste) does not get enough oxygen to keep it aerated, or if it becomes saturated, it will become anaerobic. Anaerobic windrows can produce methane gas and hydrogen sulphide. This may generate odours from the windrows. Turning an anaerobic windrow will increase the odour generated. Odours may also be generated by failing to keep the composting area clean and drainage channels clear.

The Environment Agency is primarily responsible for regulation as in order to store, sort or compost waste material, or spread waste compost onto land, a Waste Management Licence or site exemption is generally required with the Environment Agency. Whether a Waste Management Licence or an exemption is required will depend on the types and quantity of wastes.

Although the Environment Agency are responsible for site regulation the local authority also retains powers under the Environmental Protection Act 1990 to serve Abatement Notice if is it satisfied that a statutory nuisance is being caused.

Bioaerosols are in essence micro-organisms (bacteria, fungi/moulds or viruses) or their products that are airborne. As composting is a natural process in which micro-organisms are encouraged to grow to break down waste material large numbers of micro-organisms are present in compost and any handling of the material can create a bioaerosol. This can happen when the piles of material (called windrows) have to be aerated or turned. Further bioaerosols are likely to be created at the end of the process when the compost is often sieved.

Concerns have been raised that bioaerosols generated from composts can affect health. The Health and Safely Executive have prepared a report on this very question.

The primary objective of the HSE study was to critically review published literature related to studies of airborne micro-organisms or their constituent parts (bioaerosols) associated with organic waste composting facilities, and to establish whether there is a risk to worker health from the inhalation of these bioaerosols.

The review aimed to identify the personnel at risk on compost sites, identify the circumstances which increased the risk and indicate suitable control measures to control the risk. A further consideration was that airborne dispersal of bioaerosols from compost facilities could affect neighbouring facilities or residents, leading to health concerns, and the review also looked at evidence of bioaerosol dissemination from sites, potential exposures and reported ill health.

The full report is available at http://www.hse.gov.uk/research/rrpdf/rr130.pdf.

If you work with compost, you may be exposed to bioaerosols, because of the large number of micro-organism present in compost. If you breathe in those micro-organisms in large numbers over a long period they can trigger an allergic reaction. This can range form a short-term flu-like reaction (inhalation fever) to longer-term ill health such as asthma or bronchitis. Once a person has become sensitised, subsequent exposure to even a smaller quantity can trigger the allergy.

Your employer is obliged by the Health and Safety at Work Act and regulations to assess the risk to you.

Residents living near composting sites often complain of ill health affects such as exacerbation of Asthma, bronchitis and itchy eyes. Whether these symptoms are actually being caused by raised levels of bioaerosol is difficult to prove.

A study by C E W Herrof the Institute of Hygiene and Environmental Medicine, Medical Centre, Faculty of Medicine, Justus-Liebig-University of Giessen, Germany in 2002 did however find that bioaerosol pollution of residential outdoor air can occur in concentrations found in occupational environments. The study showed that residents exposed to bioaerosol pollution were shown to report irritative respiratory complaints similar to mucous membrane irritation independently of perceived odours.

The Environment Agency has a general presumption against permitting of any new composting process if the boundary of the facility is within 250 metres of a workplace or the boundary of a dwelling, unless the application is accompanied by a site-specific risk assessment.

The Environment Agency issued a position statement which stipulated that if new composting sites, or new activities on existing sites, are less than 250m from a sensitive receptor such as a nearby residential property, they must assess any health risk and, if necessary, control potential exposure of that sensitive receptor to bioaerosols.

The 250m distance was estimated from previous studies which indicated that by this distance any bioaerosols associated with commercial composting would disperse in the atmosphere and concentrations would be reduced to background levels.