Parliamentary questions

Concerns about open-windrow composting are increasingly being raised in Parliament

On 6 June 2008 Steve Webb MP asked

“What estimate has he made of levels of emission of bio-aerosols from open windrow composting sites in the last period for which figures are available; what assessment he has made of implications for (a) human and (b) animal health of such emissions; and what guidelines his Department issues to planning authorities on applications for new open windrow composting sites.”

Joan Ruddock MP, Parliamentary Under-Secretary, Department for Environment, Food and Rural Affairs, replied:

There are no estimates of emissions of bioaerosols from open windrow composting sites for any period.

See for the full answer.

On 24 June 2008 Michael Clapham MP said:

“I am pleased to have secured this debate this evening on open windrow composting. Let me say at the outset that I support the recycling of green waste. However, it must be done in a safe manner and without endangering the safety of those live in close proximity to recycling sites. It is in that context that I want to make two points in my contribution—about the danger associated with this type of process, and about public safety.

I also want to take this opportunity to thank the Minister for her reply to me of 16 June 2008, which goes some way to answering some of my concerns, but I want to encourage her to go a little further. I will refer to her letter later and suggest how we may take the matter forward.
The problems associated with open windrow composting were brought to my attention by local residents in my constituency who were protesting against the proposal for a composting site near to the village of Hood Green in the hinterland to the Pennines. I know that matters to do with the site are for the local planning authority and not for this debate, but I want to speak about the dangers generally associated with the open windrow composting process and what can be done to mitigate them.
The process takes place on a large concrete base and the method of decay is helped by the natural internal combustion of the waste. As the green waste heats, the process of decay is facilitated. The waste is turned over by machine at intervals to ensure thorough decomposition. That agitation produces bioaerosols, which can be called organic dust. One such bioaerosol is Aspergillus fumigatus, a fungus that can cause serious respiratory damage and has been known to be fatal. There are other downsides to the process, including the odour that results—particularly from the run-off of rain, which can collect and stagnate. That adds to the sickening smell, which also attracts vermin and flies; they are a further hazard of the process.

I want to draw the Minister’s attention to the Giessen study, which took place in Germany; I shall read from its introduction and conclusions in a moment. I want to do that because the Environment Agency advises a 250 m precautionary buffer zone, although from its website it appears that the agency is not too sure of what the distance should be. That is an important issue.

I contend that, on the evidence available, a 250 m buffer site is inadequate in many circumstances. In that context, I refer the Minister to a study carried out by scientists at the University of Giessen Institute for Hygiene and Environmental Medicine on the effects of bioaerosol-polluted outdoor air on the airways of residents. It is dated 14 November 2005. I am advised that, for some strange reason, the study was not included in the Health and Safety Executive review of research report 130.

The introduction to the study states:

“A team of doctors, process engineers, microbiologists and meteorologists were assembled, and conducted this investigation into the effects of bio aerosol polluted air on the airways of residents. The study was double blinded to the ongoing microbial levels. A total of 356 medical questionnaires were collected from residents near a green waste compost site and also from an unexposed residential control area. The prevalence of health complaints were assessed against distance from site and the recorded microbiological pollution levels…The site near Giessen, Germany processes yard trimmings, grass cuttings and organic waste. The material is shredded, formed in windrows and turned regularly. Throughput is approximately 12500m per year.”

The conclusions of the study are of great interest, and I want to draw the Minister’s attention to them:

“There is clear evidence of elevated health changes with residents living up to 500 metres from this green waste site. Mucus membrane infections are particularly elevated, shortness of breath is shown to be an effect of spore inhalation and excessive tiredness is distinctly linked to site emissions.”

The study continues:

“This study is believed to be the first to actively show the causal link between levels of bio aerosols and health conditions. Other studies over the last 20 years have hypothesized over the effects on those living in close proximity to compost sites and have identified raised levels of fungal spores at 500 metres distant, but apart from stating that ‘there is potential for chronic ill health, which may not yet have had time to manifest itself’, no change in Environmental Agency recommendations for distances from sensitive receptors has yet emerged.”

The agency referred to is of course the German environment agency. It concludes in its final paragraph:

“Fungal spores are common in air and every cubic metre of air breathed will contain a few minute spores. Generally the immune system can cope with levels above background, but in the area of a composting site the concentration of airborne spores is increased dramatically. Exposure should be limited wherever possible up to the 500 metre line where background levels then descend to normal.”

In effect, the study is saying that we should have a buffer zone of 500 m. Given that it is the most comprehensive study that has been done, I am rather surprised that it was not included in the HSE review of research report 130.

The Minister will be aware of the Stourbridge case, where, on 10 December, a composting site that was within 250 m of residential homes was closed. A man who acted as a consultant to the group that opposed the site advises me that it was closed because of excessive amounts of odour and bioaerosol emissions; I know that the Environment Agency takes a different view. He has provided me with the medical backgrounds of 12 of the 14 victims. Two of the 12 were suffering from the Aspergillus fungus; the others had picked up different infections on top of their chest conditions. Since the closure, I am advised that the five people who have been followed up have all reported that their health has improved and that they are using only half the medicines that they were prescribed at the time when the site was open. If we not only look at the Giessen study but draw on the experience gained from Stourbridge, it is clear that important evidence links the victims to the inhalation of organic dust from those composting sites.

The Minister may be interested in the work that is being done at Sheffield university. The Environment Agency decided on its 250 m buffer zone on the basis of a study carried out on flat lands in Norfolk, but when people from Sheffield university investigated how the wind carries spores in the hinterland to the Pennines, they found that it blows up the hill and then forms a kind of vortex on the other side, carrying some of the spores up to 1 km further than was previously supposed. It is important that we take into consideration the terrain for which many composting applications are made. I understand from a similar study that the Californian authorities have decided to go with a 500 m buffer zone instead of the shorter one that was previously used.

As the Minister will be aware, there are alternatives to open windrow processing, including complete enclosure and a system called IVC—in-vessel composting—which operates almost like a low-pressure cooker and deals with the green waste without producing the bioaerosols.

Problems may be created in the work environment for employees, and that issue should also be considered closely.

The Minister wrote me a helpful letter—it included one point on which we may be able to make further progress—in which she referred to the development of amenity risk assessments at waste management facilities. She wrote:

“This project will help to develop methods for estimating downwind concentrations of bio-aerosols and focus on improving data availability to support research into dispersion modelling.”

As I say, dispersion modelling is being done at Sheffield university. She went on to say:

“The report will describe a number of peer reviewed journal papers examining bio-aerosol production and dispersal”

It is in that context that I urge her to ask that the Environment Agency and the Health and Safety Executive, which has a public health function, look at the Giessen study. As far as I can see, it is the foremost study on composting in the community.

In conclusion, I ask the Minister to do four things. First, I would like her not only to ensure that the HSE and the Environment Agency review the Giessen study, but to encourage them to take a cautious view on recommendations of a more appropriate buffer zone, particularly in areas such as the hinterland to the Pennines, where it is very hilly and we get the sort of wind problems and vortexes to which I referred. I would also be pleased if she advises that research done before 2000 is outdated, because much of the relevant literature is more recent. The Cornell Waste Management Institute, which is an Ivy league institute, is making that recommendation. Will she ask the HSE to advise on the best and safest composting method for employees and the public? Finally, will she ask local authorities to defer any proposals for new sites until the Environment Agency and the HSE advice is available so that we can ensure public safety in the future?
See Hansard for the Minister’s response