Agricultural Odours or Smells

Why Spread on Farmland?

There are a number of forms of waste, or waste products which are valuable fertilisers. It makes sense for these to be spread on land to help crops or grass for grazing grow. The alternative would be dispose of the material to landfill sites, which would be wasteful and difficult to mange safely for the environment. By using these materials, there is less need to use chemical fertilisers, which need a lot of energy for their production. Use of energy usually means generation of Carbon dioxide, widely recognised as a greenhouse gas which contributes to global warming.

Most materials spread to land (except chemical fertilisers) have some smell associated with them. Because our communities are surrounded by farmland, it is to be expected that we will smell what has been spread from time to time.

What can be spread on Farmland?

Traditional fertilisers include:

• manure from farmyards and cattle sheds used during the winter. This often includes straw on which animals have been bedded and is stored up until conditions are right for it to to be spread on land. Because it is fairly solid, it is usually spread from a 'muck spreader behind a tractor which 'throws' it across the land; and
• slurry, a more watery form of manure, which is often stored in tanks until it can be spread on the land. Because it is liquid, it is transported in a tanker trailer and is either injected into the soil or is allowed to flow out in a controlled manner through nozzles close to the ground.

From intensive chicken farming comes 'hen pen', which is the deep bedding material used on the floors of chicken sheds. It is cleared out from time to time and has a noticeable smell of ammonia from bird droppings. The ammonia provides a rich source of nitrogen, which is a good fertiliser. It will sometimes contain some dead birds. It may be stockpiled within fields for later distribution and is spread in a similar way to manure.

Recent developments include:

• sludge cake. This is the dried, treated solid material from the sewerage system and is rich in nutrients. Whilst the liquid from the sewerage system is treated and returned to rivers or the sea, the solid material is removed, dried and treated to give a material which looks a little like peat or flakes of chocolate. This can have a strong odour. It is often spread with lime; and
• PAS110 Bio fertiliser (opens new window). This arises from the anaerobic digestion of waste, including food waste which is now commonly collected separately from homes and businesses. The name relates to the British Standard which controls the processing of this material to ensure quality, safety and consistency in the end product. Liquid PAS110 material has been used in West Lothian. This can have a strong odour.

When does spreading take place?

Spreading should take place when conditions are right. Things which farmers and contractors should take into account are:

• whether rain is expected. Spreading before heavy rain should not be carried out as the nutrients will be washed off the land into water courses, which can cause other environmental problems;
• the direction of the wind. Spreading should not take place when the wind will; take the smell directly towards neighbouring communities;
• the temperature. Very warm weather may make the odour stronger. At the same time, residents of local communities may have windows open for ventilation, increasing the effect of the odour in homes. Frost or snow on the ground will prevent nutrients getting into the soil;
• what material has already been spread on the land and when. There are accepted limits as to how much fertiliser land can usefully accept; and
• whether the land is firm enough to take tractors, trailers and other machinery. It can't be spread if the land is too soft following long term rain.

Spreading often takes place late winter before summer planting and late summer / early autumn following harvest. It can also happen at other times of the year when weather conditions are suitable.

Standards Expected

Guidance on spreading and minimising odour nuisance is available in 2004 publication, 'Prevention of Environmental Pollution From Agricultural Activity (opens new window)'. In addition, for some materials there are mandatory or recommended limits on how much material can be spread to land.

To minimise odour problems, Environmental Health expects:

• no surface spreading on pasture (grassland) which is close to houses; and
• all surface spreading to other land to be followed up within 48 hours by ploughing to turn the material over in the soil.

However, there may be genuine reasons why it is is not always possible to do everything to minimise the smell from spreading.

Regulatory Controls

There are no specific regulatory controls on the spreading of:

• manure; and
• PAS110 Bio fertiliser (opens new window). This is because it is classed as a product, not a waste, subject to specific criteria (opens new window).

SEPA - Scottish Environment Protection Agency (opens new window) licenses:

• the storage on land of sewage sludge cake, but not its subsequent spreading; and
• the injection of slurry, depending on the volumes concerned and the circumstances

Please note that there is no requirement to notify the local authority or request permission from the local authority before spreading. This means that we do not usually know where or when spreading will happen.

What to do when there is a problem

There will always be some smell from agricultural spreading, so being able to smell what has been spread doesn't mean that the farmer should stop or that the farmer of contractor has done something wrong. If you believe that:

• the farmer has done something wrong or unreasonable; and
• the duration, strength or nature of the smell is unreasonable

you should first discuss it with the landowner. If this does not succeed, you may ask for the matter to be investigated. Contact Environmental Health with as much information about what you are smelling and where the smell is coming from (if known). (However, please note that Environmental Health does not routinely investigate agricultural odour complaints). Only when other higher priority work permits and the problem is serious and persistent will an investigation be carried out. We will liaise with SEPA - Scottish Environment Protection Agency (opens new window) when needed.

If there is evidence of best practice not being followed with the result that the smell is unreasonably intrusive, Environmental Health may take formal action using Statutory Nuisance law legislation. However, formal action will generally only be taken where informal intervention would not succeed or where there have been repeated incidents of failing to follow best practice. It is also important to understand that taking formal action against the farmer or contractor will not make the smell go away immediately.