This section addresses the key modern issues in 'disposal' of meat processing waste, including environmental considerations and the issue of transmissible spongiform encephalopathies (TSEs) (e.g. bovine spongiform encephalopathy (BSE)), with regard to destruction of infectivity.
A range of varied wastes are generated as a result of meat processing. All of these wastes require disposal in one form or another, as dictated by local legislation, local environmental sensitivity and, in some instances, the requirements of the markets into which products and co-products are sold.
All of these requirements (legislative, environmental, health and safety, market, etc.) are captured, cross-referenced and addressed in a single waste management plan for the operation. While the specifics for each jurisdiction may vary, some typical 'key steps' in developing a waste management plan (EPA Victoria, 1993) are to describe:
• Background: the relevant legislation that governs plant operation.
• Production processes: the activities that generate waste including the types and amounts of waste generated and procedures for dealing with accidents, spills and other incidents that affect waste management.
• Waste assessment: how the waste is disposed and current costings. Procedures for identifying and implementing opportunities to minimize the amount of waste generated.
• Evaluation and feasibility: technical and economic feasibility analyses for each waste minimization opportunity including the best available technology (BAT) and commonly available technology (CAT).
• Selected projects: list of waste minimization projects with expected costs and savings.
• Implementation: a timetable and funds for implementation.
• Review: indicators or other criteria on which the performance of waste management practices will be assessed, and how often performance is assessed.
• Details of staff training.
The four broad categories of waste generated through meat processing are waste odours, wastewater, organic solid waste and specified risk material (SRM). Unless managed well, each of these categories has the potential to significantly undermine the operational viability of a meat processing plant.
The major sources of odour from slaughterhouses emanate from manure, paunch content and rendering. Manure and paunch content odours can be effectively managed through routine collection and composting of these materials.
The biodegradable nature of rendering raw materials has a direct impact on the generation of odours. Storing these raw materials for prolonged periods at ambient temperature, prior to their separation and stabilization via the rendering process, both increases the production of noxious odours and diminishes the value of the resultant protein meals and fat fraction. Rapid processing minimizes noxious odours and maximizes the quality of rendered products. In order to minimize odour emissions, modern plants totally enclose the entire rendering process line to allow entrapment and treatment of odours. Biological scrubbers operate via microbial decomposition of air pollutants absorbed in the scrubbing medium.
Burning rendering gases in an existing boiler presents a simple and effective method for significantly reducing noxious odour emissions. Steam collected from rendering cookers, driers and evaporators is passed through a cyclone to separate solids, and a heat exchanger to dewater the moist air. The condensate is discharged to wastewater treatment and the remaining odour laden air is burned. This method is particularly applicable to the low-volume, high-concentration odours generally associated with rendering and has been described in the BREF (best available techniques (BAT) reference) document from the European Commission (BREF SA, 2003).
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