Waste minimisation techniques

Waste minimisation techniques can be grouped into four categories ... 

A spin-off from these total approach waste minimisation techniques is that Hovione now market their know-how to third parties under the name Greencycle Technologies . A combination of R D and engineering expertise is offered to the fine chemical and pharmaceutical industries to solve other waste minimisation problems. A new business opportunity has thus been created and marketed from a simple concept and expertise built up over a ten year period. 

The limits are very low at fractions of parts per billion. A similar table exists for mercury emission limits (EC directive 84/156/EEC) but with even stricter emission limits. In the UK cadmium legislation has recently become stricter, in line with the EC initiative. December 1993 saw the publication, in the UK, of the Department of the Environment Process Guidance Notes (IPR 4/22) related to the manufacture of zinc, lead, antimony, arsenic, beryllium, gallium, indium, palladium, platinum, selenium, tellurium, thallium and their compounds. The publication tabulates potential sources of metal emission and places a large emphasis on effective and efficient waste minimisation techniques. The document sets the scene for stricter legislation on metal emissions in the UK. 

The hierarchy of waste management techniques has prevention as the most desirable option ahead of minimisation, recycling and, as the least desirable option, disposal. The term cleaner production embraces principles and goals that fall comfortably within the waste prevention-minimisation range. It has been described within the United Nations Environmental Programme as ... 

In principle, BAT(NEEC) and RACT offer the user flexibility in choosing an emission reduction strategy -choice between a variety of end-of-pipe abatement techniques, low solvent technologies, waste minimisation or any combination of these. It recognises that the most appropriate solution will vary from one application to another with size, product quality required and the age and location of a plant. 

Waste minimisation involves any technique, process or activity which either avoids, eliminates or reduces a waste at its source, usually within the confines of the production unit, or allows reuse or recycling of the waste for benign purposes. 

As can be seen, there is a good deal of overlap between the terms waste minimisation and cleaner production. Both terms fit within the hierarchy of waste management techniques ... 

Waste minimisation is not always achieved by changing processes, solvent, reaction conditions or by improving management techniques. Addition of auxiliary chemicals to the system under review changing the physical characteristics of the reaction medium, can achieve more efficient hence cleaner chemistry. 

Benefits of efficient waste minimisation and the techniques being used... 

The need to eliminate and minimise waste streams and produce environmentally friendly products is fundamental to the production process. To obtain a yes score this approach to process design must be clearly recognised in the CER. Factors included in the assessment will include product safety, the use of renewable raw materials, efficient processes, and manufacturing techniques and energy sources designed to minimise environmental impact. 

The technique results in a minimisation of dust emissions from moulding and finishing, as compared to sand moulding. The emissions of VOC are eliminated as no gas is emitted for the inert ceramic mould. Additionally the amount of waste (dust, metal) is reduced. The reduction of feeder systems results in a higher 5deld of castings per melt. 

Waste water prevention and treatment In many cases, waste water can be prevented or minimised by taking in-process measures. Waste water that cannot be prevented, will contain mineral or metal dust, amines, suphates, oil or lubricants, depending on its source within the process. The applicable treatment techniques differ for each of these compounds. 

If the volume/economics situation justifies continuous production versus batch production then the process development chemist has a whole new array of techniques available to minimise waste production at source, i.e. in the operation of the process. Recovery and recycle of solvents or raw materials as integral parts of the continuous process lead to greater efficiencies than most batch processes, make costs of production lower, and hence enhance the competitive position of the product in the market... 

Design attempts to combine the elements of art and science. The first consideration in any design and optimisation problem is to decide the boundaries of the system. Optimised process design in plastics waste recycling considers the costs of manufacturing, processing technique and the minimisation of waste. 

With respect to construction, a lot of experience has already been gained in the conventional mining industry, but the stringent specifications for the construction of deep rq)Ositories for radioactive waste require further development and testing of specific excavation and construction techniques. In particular, attention has to be paid to minimisation of host rock perturbations and creation of excavation damage zones. 

Around the world, more than fifteen underground experimental facilities have been established either in abandoned mines or built for special purposes in salt, clay, granite, basalt, tuff (see Table I). Several techniques have been demonstrated for sinking of shafts, excavation of galleries and drilling of waste emplacement holes. Therefore, further development should only aim at optimising the available techniques in terms of excavation space and costs and minimising disturbance of the host rock. 

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