No one likes bad odour; what we can do about it?

Impacts on amenities from odour, dust, noise and light can often affect our enjoyment of the use of land. Some people may complain to their local authority or the Environment Agency when a specific activity impacts their amenities repeatedly and intensely. If regulators receive enough complaints and can substantiate them as a ‘nuisance’, they may serve an abatement notice on those activities causing the loss of amenities and require them to adopt ‘Best Practicable Means’ to prevent reoccurrence. If the operator doesn’t, the regulator can take legal action.

In recent times, the National Planning Policy Framework has been updated to include the ‘agent of change’ principle. New developers therefore often need to assess the potential for exposure to odours, dust and noise from existing sources on the future site occupants. Assessing the effects of newly proposed sources of odour, such as new pastoral agricultural sites, anaerobic digestors and wastewater treatment works, is also considered in the planning system to ensure existing receptors would not be adversely affected.

Temple is a leading planning, environment and sustainability consultancy. Our experienced air quality and odour personnel have extensive experience in undertaking odour assessment and reporting in support of planning and environmental permitting projects. We are therefore well placed to provide our insights into the factors which may affect the completion of odour assessments. So how do we assess odour?

The Institute of Air Quality Management (IAQM) have produced guidance which outlines three of the most effective mechanisms to assess odour in assessments: qualitative assessments, ‘sniff tests’ and dispersion modelling. We have discussed these below.

Qualitative Assessment

Qualitative assessments involve reviewing the potential for an odour source to be low, medium or high, using any known information about the source. The method then reviews the pathway effectiveness and receptor sensitivity to determine the potential overall impact. We found a qualitative assessment useful for a proposed residential Site located near a poultry farm. Sniff tests may have been ineffective, due to the variability in odours derived from poultry throughout the rearing cycle; although without knowledge of how the poultry farms operate, dispersion modelling may also have been inaccurate.

‘Sniff Test’ Monitoring

Monitoring using sniff tests can give a snapshot of odour at specific locations under conditions prevailing at the times and days of the sampling. Sniff tests require the human nose as a detector to enable the odour magnitude, frequency, duration and offensiveness of the odour to be recorded at a particular location at a specific time. To maximise the validity and reliability of any data collected from sniff tests, sniff tests would need to be carried out on sufficient occasions to represent the full range of conditions in which odour would be generated; and during a range of weather conditions. The odour survey must typically ensure the receptors sensitive to odour are downwind of the source during at least one, and ideally more, of the visits.

Dispersion Modelling

Dispersion modelling is advantageous in instances where there is a good understanding of how the odorous activity operates, in addition to the dispersion pathway and local receptors present. It also helps for planning applications where the source does not yet exist, such as industrial sites. Dispersion models require sources  to be established at different locations to be virtually represented. Other parameters are used to represent dispersion characteristics from sources, including meteorological data and terrain.

Dispersion models predict odour concentrations averaged over every hour of the year, so can capture a range of different weather conditions which may not be represented on the day of any odour sniff test. We have been able to effectively identify the locations at which odour thresholds would be breached, to delineate parts of Sites which are suitable for more sensitive land uses. This has been useful in providing design advice for residential sites. Temple’s air quality team have also undertaken dispersion modelling to optimise the height and characteristics of flues and flue gases discharging potentially odorous air at industrial sites. For example, the contour plot shown below indicates how we have demonstrated areas breaching or meeting odour thresholds in the vicinity of a proposed waste facility.

If you wish to obtain planning permission for a potentially odour-causing land use type; or are considering developing near an odorous land use, please contact us; we would be pleased to help.