The Waste Management Industry today has to comply with the requirements of a wide spectrum of legislation designed to ensure that an operator is not having an adverse impact on the environment. An important part of this compliance is to undertake laboratory analysis of waste and ash which is either produced or used as a feedstock in a process. The UK Waste Regulations system implements various European Directives including the Waste Framework Directive and the key legislation can be summarised as follows-

- Environmental Protection Act 1990, Part 2
- Environmental Protection (Duty of Care) Regulations 1991, as amended
- Landfill (England and Wales) Regulations 2002 and amendments
- Pollution Prevention and Control (England and Wales) Regulations and amendments
- Waste Management Licensing Regulations 1994, and amendments.

Standard laboratory test methods that are either European BSEN or US EPA will normally be employed for waste and ash. However all these methods rely on a representative sample of the material being taken and the importance of this factor is often overlooked and can lead to erroneous data being produced. In practice, the way in which a representative sample of waste or ash is taken is equally, if not more important, than the analysis of the sample in the laboratory.

Obtaining a Representative Sample from the Process: The first problem that can be encountered is how to obtain a sample for submission to the laboratory from a waste process where many hundreds of tons of material are involved. In order to accomplish this the characteristics of the process need to be examined and would typically include the following-

- Does the process vary on an hourly, daily or weekly basis?
- What is the optimum location for the sampling e.g. cumulative grab sample from a conveyor or silo?
- What is the optimum quantity of the sample/cumulative sample?
- What are the characteristics of the sample e.g. free-flowing, includes large metal objects etc?
The sampling procedure will usually incorporate some element of manual mixing using the well established “coning and quartering” techniques originally designed for solid fuels e.g. coal and ash. The final sample that is submitted for laboratory analysis should be a well-mixed and representative portion and the quantity required depends on the type of testing required.

Obtaining a Representative Sample in the Laboratory: In the laboratory the sample has to be prepared for analysis and although, as described above, the sample should be reasonably uniform, it is rare that a completely homogeneous material is received. Indeed, it is very common for laboratories to receive materials that require a lot of preparation and with wastes or ashes can contain relatively large metal objects, rags, stones etc. The first stage in the laboratory preparation is the removal of large objects that are not amenable to grinding/shredding and these are weighed and put to one side. Next the sample is ground/shredded and a representative aliquot taken for the required analysis. For many analyses the sample has to be dried beforehand and results are therefore expressed on a “dry basis”.

Presenting the Analysis Data: The analysis data generated by the laboratory will be expressed on either a “dry” or “as-received” basis. This can often lead to confusion as normally data is required to be presented on an “as-received” basis in order to compare directly with legislative limits. This is particularly the case where a sample is from a material that is to be consigned for licensed waste disposal. Where the sample is wet, the moisture content needs to be measured and then concentrations corrected accordingly. Where nongrindable materials have been removed from the sample prior to analysis then test results also need to be corrected to produce data on an “as-received” basis.
Given the above it can be seen that it possible to obtain very different results for analysis of the same material by two different laboratories if results are expressed in different ways.

Waste Analysis Services from MSSL: MSSL is able to offer advice on all the issues discussed above relating to waste/ash sampling and analysis