Odour problems

There are two types of odour associated with compost farms:

  • A piney odour associated with aerobic composting;
  • A pungent and nauseating smell associated with anaerobic composting the best description of which is a ‘mixture of sileage and vomit.’- made by an EA officer visiting an open windrow composting site in BANES.

These smells are quite distinctive and quite different from normal farm smells you would get from muckspreading (although some operators are now mixing the compost with manures to ‘mask the smells’. Whatever, the odour what is distinctive is that they don’t just happen 2 to 3 times a year but occur frequently, day-in, day-out; week-in, week-out; depending on the weather conditions and the topography surrounding your site.

In South Gloucestershire the Environmental Health team have recognised that the piney odour is ‘more offensive than first perceived’. It is O.K. for the first 10 minutes which is the average time an officer will come out and smell it, but day in day out it is quite a different matter, it gets you in the back of the throat and once you become sensitised it’s hopeless.

Who is responsible for assessing odour impact?

This has always been rather confused, often with both the Local Authority and the Environment Agency claiming the the other body were responsible.

This has become rather clearer over recent months:

STOP PRESS : DEFRA have issued new guidance notes on assessment of the likely impact of odour problems by local authorities. This document now makes it clear that Local Authorites and NOT the EA are responsible for assessing the likely odour impact at the planning stage. Whether Local Authorities have the skills to do this is questionable. The other worrying fact about this is that once the Local Authority has given consent it is not responsble for following up once odour problems occur. This is now firmly the responsibility of the EA (Annex A, Permitting Regulations) – who notoriously do not attend on site for days if at all; making it virtually impossible to prove odour nuisance without private action.Even then the courts have to be satisfied that you have exhausted the possibility of making the regulatory authority act.

Measuring odour impact

Odour nuisance is defined in terms of odour units. In simple terms air is collected and put before a panel of people who are sensitive to smells ‘super sniffers’.

  • 1 odour unit is where such a panel can just begin to detect a smell is present but are unable to identify it.
  • 3 odour units is when the panel can just begin to detect what the smell is, be it coffee, bread, compost e.t.c.

The EA provides guidance that the smell of odour is actually so unpleasant that a level of 1.5 odour units is unacceptable, i, e, just over the point when you can detect a smell but not identify what it is.

Incidentally the Composting Association provides guidance that only a level of 3 ou is unacceptable. Since they are not a regulatory authority this should be ignored.

STOP PRESS : In DEFRA’s new guidance notes on assessment of the likely impact of odour problems by local authorities; they state that green waste composting only becomes unacceptable at 3 odour units, whereas compost including food waste becomes unacceptable at 1.5 odour units. This is at odds with many other publications by the EA and will have to be resolved. In essence DEFRA just seem to have adopted the figures which are provided by the Composting Association (now called Organics Recycling) which we believe is unacceptable – clearly representatives of the industry have a vested interest in the figures being as high as possible.

Lack of scientific assessment of odour impact

Although release of odour from composting facilities is as critical in respect of potential impact on sensitive receptors as bioaerosols, often no scientific assessment is made to assess this element.

Current UK Guidance (Horizontal Guidance for odour-published by the EA) demands that where a history of odour complaints or annoyance already exists there is a need for in-depth assessment using a quantitative approach (dispersion modelling).

As with bioaerosols the quantitative approach will take into account the size of the site, the local climatic conditions over a long period, and the local topography and comput this information to predict how often sensitive receptors are likely to suffer odours of more than 1.5ou. However, unlike bioaerosols modelling for odours is well established and well recognised. The EA even prescribe the model which should be used!

Unfortunately, our experience is that the EA ignores the requirement of its own guidance and rarely demands a quantitative assesment as a requirement. However, you can do this yourself and prove the likely extent of the odour problem and the costs are not too prohibitive at between £3,600 to £5,000.

Beware of claims in planning applications

The applicant often claims that malodorous activities will only take place when the wind is blowing away from residents therefore no odour nuisance will be caused. This is nonsense, the wind can turn very quickly and control in this way is impossible.

Also the reality of any commercial process is that the applicant will have booked and be paying for screening and shredding equipment. Therefore these machines and the men to operate them could not stand idle for several days when wind conditions are unfavourable, particularly when windrows must be turned at least 3 times a week to keep the composting process active.
Promises that the operator will make regular ‘odour assessments’ are worthless. Workers on these sites can become desensitised to the smell, in a phenomenon recognised in the Composting Association’s Code of Practice.

Although a Waste Management License prevents open windrow compost sites being located within 250 metres of occupied dwellings this distance is wholly inadequate and malodours can extend much further. For intensive pig farming, also policed by the EA, planning application must be sought when their are sensitive receptors within 400 metres.

Proving Statutory Nuisance

If planning consent is granted and you are suffering from the smell you must prove Statutory Nuisance in order to close a site down.

If your site is an exempt one the responsbility for assessing nuisance lies between the Council and the EA.

Under the new permitting regime local councils are no longer able to use statutory nuisance powers to regulate sites already regulated by the Environment Agency.

This is not good news as EA officers can be located a fair distance from sites and will not attend for 2-3 days if they respond to phone calls at all.

Our experience is that the Authorities are reluctant to pursue a case of odour nuisance believing it too difficult to prove. Certainly the Local Council will have to prove the nuisance ‘beyond all reasonable doubt’ whereas residents only have to prove a case ‘on the balance of probabilities.’

Nevertheless there are experts out there who can guide you through the process although you will have to bear the considerable costs of repeated odour testing.

In principle you must establish:

  • The nature of the odour;
  • The frequency of the odour and
  • The persistency of the odour.

Apparently to establish odour nuisance you must be able to prove you are suffering from 1.5 ou or more for more than 2% of the time on a normal distribution and that this state of affairs has continued for some time.

It would be nice to think the operator has to pay for the testing but in reality, when they do, we have found testing has been carried out when the compost site is not active and the climatic conditions are favourable so no malodours are caused.

So once planning consent is granted you are in for a lot of work and expense in terms of logging and monitoring and paying for experts.

History of prosecutions by the EA

Historically the EA seem to have been very reluctant to prosecute for odour.

Recently (12th April 2009, The Telegraph), the EA claim they have set up ‘stench squads‘, or specially trained officers who can deal with the massive increase in complaints regarding odour nuisance coinciding with changes in waste disposal.One group of residents recently asked for a visit by the’stench squad’ only to be told the EA officers didn’t know what the residents were talking about. When they explained, the officers reliably informed them that these stench squads would not result in any change in their area; so business as usual: no prompt attendance at site (indeed often no attendance at site at all), when odour nusance is reported.

For a full list of odour prosecutions by the EA in the last 6 years see the section on prosecutions.