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New EPA Guidance on Pig Odour

The EPA has released an instruction note which will provide applicants with a methodology on how to screen for and assess odour impacts from the licensable intensive agriculture pig sector, as well as providing assistance for applicants in demonstrating compliance with BAT 13 (to reduce odour emissions and/or odour impact) of the Commission Implementing Decision (CID) 2017/302. The instruction note replaces the EPA guidance document and screening methodology ‘Odour Impacts and Odour Emission Control Measures for Intensive Agriculture (2001)’.

There are a number of published documents on general theory, advice and guidance on odours from licensed sites and odour abatement methodologies for industrial and waste facilities. Examples of this include the following:

• Air Dispersion Modelling from Industrial Installations Guidance Note (AG4), EPA, 2020;

• Air Guidance Note 5 (AG5) Odour Impact Assessment Guidance for EPA Licensed Sites, EPA, 2021;

• Odour Emissions Guidance Note (Air Guidance Note AG9), EPA 2019;

• Commission Implementing Decision (CID) 2017/302 establishing Best Available Techniques (BAT) Conclusions for the intensive rearing of poultry or pigs & associated BREF documents.

However, these published documents do not specifically include a list of emission factors for pig rearing in Ireland, nor do they recommend a specific screening procedure to determine the potential impacts from piggeries on sensitive receptors. Therefore, the purpose of the instruction note is to ‘bridge this gap’.

Odour Sources

The odours generated in pig production units typically originate from the following sources:

• Feed;

• Spilled feed;

• Animal body odour;

• Urine and faeces.

The most relevant source of odours from intensive pig production is animal excreta. The odours generated from excreta are a final product of the interactions between odorous and non-odorous components that are produced during the anaerobic degradation of organic matter in animal slurry.

In terms of the screening assessment tool, the magnitude of odour emissions from intensive pig installations and the subsequent impact on sensitive receptors will depend on several factors. Some of these factors are considered in the screening tool and all factors can be incorporated into more detailed odour modelling, if necessary.

Acceptable Odour Level Benchmarks

The EPA instruction note sets out what the EPA considers acceptable odour levels, below which licensed sites may operate without generating unacceptable odour pollution at sensitive receptors.

The following acceptable odour levels at sensitive receptors are applicable to intensive agriculture activities:

• 3.0 OUE/m3 for new pig-production units;

• 5.0 OUE/m3 for existing pig-production units (includes sites licensed by the EPA between 2001 and 15th February 2017 only);

• 6.0 OUE/m3 for existing pig-production units (only includes sites licensed by the EPA prior to 2001 and not reviewed since this date).

It should be noted that the above acceptable odour levels are only applicable at odour sensitive locations. The applicant’s dwelling and farmyard are not considered to be odour sensitive locations for the purposes of this instruction note. In the case where there are no third-party odour sensitive receptors present, a higher odour level may be considered to be acceptable.

Mitigation of Odour Emissions

Commission Implementing Decision (CID) 2017/302 and associated BREF document sets out the appropriate methods/best available techniques for the minimisation of emissions under normal operational conditions in order to ensure compliance with the acceptable odour level benchmarks.

Screening Tool for Odour Assessment

The EPA examined a number of international models in determining which method could be adopted for screening the odour impacts of a pig rearing installation.

The EPA identified four main objectives in the development of the screening tool:

• Provide odour prediction in a format that is consistent with the EPA odour benchmarks and of a suitable standard for a licence or planning application;

• Make it easy for all stakeholders (i.e., operators, consultants, planning officers, EPA inspectors and neighbouring communities) to understand and apply the tool;

• Provide a clear and concise output;

• Prevent reliance on external delivery mechanisms which may be outside the EPA’s control.

The screening tool allows users to test the feasibility of a pig farm in a specific location. It enables users to generate a worst-case-scenario odour impact from the pig farm. As mentioned above, the screening tool is designed to be easily navigable and requires users to input and select basic parameters such as pig numbers, pig types and the dispersion characteristics of animal houses as well as basic input parameters for any external slurry storage buildings/infrastructure. Once the user has completed this step, the screening tool carries out background calculations to determine the odour emission rate and provides a recommendation of what dispersion characteristics should apply. The screening tool then combines the odour emission rate for the installation with the appropriate dispersion profile which calculates the odour of the installation at sensitive receptors.

The EPA instruction note provides a step-by-step guide to using the screening tool and can be accessed here. The screening tool can be downloaded in Excel format from the same link above.

July 2023