What is composting?

Composting is the natural process of decomposition (biodegradation) of organic waste materials such as manure, Food and Garden Organics (FOGO) or green waste through the action of microorganisms.  Microorganisms break down the organic matter in the raw materials to produce carbon dioxide and energy in the form of heat. Organic waste materials contain many nutrients, which are made available by the composting process. The composting process converts organic waste to a fertiliser with nutrients that are readily available for plant uptake.

At commercial composting facilities the composting process is optimised to enhance biodegradation and speed up the rate of decay of waste materials. Optimisation techniques include shredding of raw material to reduce the particle size distribution of the waste stream, mixing wastes to ensure that nutrients loading is homogeneous throughout the windrow, turning and aeration of the composting windrow to optimise the internal temperature and maintain aerobic conditions for the active microorganisms.

Composting odour

Composting is an inherently odorous activity. It uses raw materials that are odorous e.g. food scraps, garden trimmings and manure, and the composting process generates volatile odorous compounds as the raw materials degrade. The emission rate of volatile odorous compounds is dependent on the nature of the composting process and the materials that are being composted. In some situations, the initial mixing of raw materials quickly results in relatively low levels of odour. After one to two weeks after placement in windrows, the native odour of the raw material can diminish to a very low level with more elevated odour emissions only occurring when the composting materials are disturbed.

The characteristics of the composting materials can be managed to minimise odour emissions and maximise the quality of the final compost product. It is important to maintain aerobic conditions, avoid anaerobic conditions, maintain adequate pH and moisture and appropriate carbon: nitrogen (C:N) ratio. Managing the process to maintain the correct internal environment within compost windrows will help to reduce odorous emissions.

Why compost?

Composting is an important process  that can deliver environmental benefits including recovery and conservation of resources and reducing the quantity of organics going to landfills. Most jurisdictions actively encourage composting for these reasons.

For example, in Ireland, the European Union (Household Food Waste and Bio-waste) Regulations 2013, compliments and enhances the Waste Management (Food Waste) Regulations 2009.  Objectives of the Regulations include the recovery of household food waste, in line with the national policy and the relevant EU Directives, to maximise the resource that can be extracted from waste and minimise the disposal of waste. Composting is an effective means of recovering food waste in accordance with the requirements of the Regulations. The Regulations will also help to achieve the targets set out in the Landfill Directive (Directive 99/31/EC) to reduce the amount of waste material going to landfill.

In doing so, it is important to ensure that nuisance odour and other potential impacts of composting are appropriately managed.

Katestone has had extensive experience with the assessment and management of odours from industrial and agricultural activities. Studies have involved comprehensive monitoring programs and data analysis, or emissions estimation and forecasting through state-of-the-art meteorological and air dispersion models.

If you would like to discuss any aspect of odour impact assessment for your development contact us today for Clear Skies.