AN EFFECTIVE STACK REDUCES ODOUR IMPACT

Odour emissions can pose a risk to the well-being of nearby communities. One way to mitigate this risk is to install a stack that helps emissions to disperse before reaching a human nose. Designing an effective stack is crucial as it can be a costly process. However, installing a tall stack may eliminate the need for treatment technologies, including adsorption, scrubbing and biofiltration. To maximise your investment, you must make sure your stack has the correct specifications, such as height, diameter and materials used. After installing a stack, it is a good idea to conduct regular odour stack sampling. By doing so, you can check that it is working properly, and demonstrate its effectiveness to regulatory bodies as part of your compliance with operating permits and planning conditions.

HOW TO DESIGN AN EFFECTIVE STACK

Understand Your Odour Issues

In order to design an effective stack, you need to understand the problem you are trying to overcome. Specifically, take steps to quantify the emissions from your processes. You need to undertake odour sampling and testing to learn more about the concentration, emission rates, intensity and characteristics of the odour emissions.

Choose the Right Height, Diameter and Location

Consider installing low-level odour sampling ports during the stack design stage.

The higher and broader the stack, the greater the initial cost. However, cutting corners can lead to increased expenses and difficulties later. So, getting it right the first time is essential. Your stack should be tall enough to allow odours to disperse before they reach receptors (people). It should also be located a suitable distance from those receptors. With this in mind, you should consider the height of nearby homes and workplaces, the topography of the surrounding area and how meteorological conditions may impact your emissions. Similarly, the stack diameter is important to control the exit velocity of the emission.

Also consider incorporating easily accessible sampling ports in the design. You can see in this photo, for example, that this particular stack benefits from low-level odour sampling ports.

Dispersion modelling can predict the impact of odour emissions from your proposed stack.

An essential step in the design is a dispersion model. This is a mathematical model which considers the factors mentioned above. It can predict the impact of odour emissions from your proposed stack. This information is essential in determining the correct design specifications. You will need data from odour sampling surveys conducted on your existing processes to inform dispersion models.

Sniff surveys are another valuable tool. They involve a trained odour panel visiting locations near your site to evaluate the intensity and characteristics of the emissions. You can use this information to confirm the impact of the emissions prior to stack construction.

Select the Right Materials

Selecting the most suitable materials for your stack is closely linked with understanding the nature of your emissions. The stack needs to be resistant to the specific properties of the odour compounds produced by your processes. Odour sampling and chemical analysis will give you the data you need here. You should also choose materials that can withstand the temperatures generated by your processes, as well as weather and environmental factors. In addition, we recommend that you consider using materials with the least environmental impact.

IMPLEMENT EFFECTIVE STACK TREATMENT TECHNOLOGY

Installing tall stacks is not always possible. Sometimes, you will also need to implement an effective technology to treat the odour emissions. There are various options available, depending on the nature of the emissions. For example, there are several different methods of eliminating odorous compounds from emissions, by passing them through a material or filter.

• Adsorption: an adsorbent material, such as activated carbon, captures the odorous compounds.
• Scrubbing: odorous compounds are eliminated by passing through a liquid scrubbing solution.
• Biofiltration: a biologically active filter, such as wood chips, breaks down and removes the odorous compounds.

To ensure that these technologies function correctly, the materials should be regularly replaced or replenished, making good maintenance practices critical.

STACK SAMPLING

Stack sampling equipment used by the odour consultants at Silsoe Odours.

Once you have installed your stack, it is a good idea to conduct regular odour monitoring to ensure it works correctly. Complacency can lead to unexpected odour complaints and problems. As with most things, issues tend to escalate if you do not deal with them promptly. As a result, you could face permit restrictions or legal consequences.

The most effective way to monitor emissions is to conduct stack sampling, which involves testing the temperature and velocity of the odorous emissions, as well as the odour concentration. You can use the results to demonstrate the stack’s efficacy to regulatory bodies. You may need to do this as part of your operating permits and planning conditions.

Silsoe Odours holds UKAS accreditation for testing odorous stack emissions. Our specialist team of odour consultants are highly skilled and can offer advice on your specific stack testing requirements. Get in touch with the team at info@silsoeodours.co.uk or by calling 01525 860222. You can also click the link below.

References:

Environment Agency: Monitoring Stack Emissions: Guidance for selecting a monitoring approach