Appendix - Ecoprofile methodology (cont'd)

A14. Interpreting results

When interpreting the tables, it is important to bear in mind the following points:

1. The values presented in the tables refer to the cumulative results when all of the production sequences are traced back to the extraction of raw materials from the earth. There are therefore some parameters over which the chemical industry will have no control. For example, a significant contributor to mineral waste will be the coal industry which supplies the production of electricity in many countries. As a consequence of consuming public electricity, a proportion of this waste will be attributable to the production of any product.
2. The values of some of the parameters will be a reflection of the country in which some plants are sited. For example, plants in countries which generate electricity from coal will exhibit a higher emission of sulphur oxides than plants in countries which do not use coal in electricity generation.
3. The magnitude of many of the parameters often owe much to the degree of monitoring of the parameter. This is especially true of air and water emissions. For example, a company which has a detailed programme for monitoring all air emissions may well apparently appear worse than a comparable company which does not monitor air emissions in any great detail and must therefore estimate their magnitude.
4. Fuel requirements, energy requirements, solid waste output, emissions to air and emissions to water all refer to the total load for all processes starting with raw materials in the earth. Although the table headings refer to these sequences of operations by naming the final operation in the sequence, the results should, under no circumstances, be interpreted as referring only to the final operations in a production sequence; they refer to the cumulative effect of the whole production sequence.
5. Solid waste arising from industrial processes has been categorised under five main headings. Mineral waste refers to waste earth and rock generated in mining operations. In this report the principal source of mineral waste is in coal production. Frequently, mineral waste is replaced in a mine working once the valuable minerals have been removed and so represents a measure of the rock moved rather than the generation of permanent waste. Slags and ash refer to the solid waste produced by industrial boilers and furnaces. This is usually inert and because it contains no organic matter that can decay with time, it is frequently used in civil engineering operations such as road building. When slags and ashes are used in civil engineering projects they are products from the process producing them and so carry with them a proportion of the burdens of the processes. In all of the data supplied by the plants examined here, none of this category of waste has been claimed as a product. Waste from chemical processes has been divided into two categories referred to in the tables as inert waste and regulated waste. The terminology is imperfect because there is strictly no such thing as unregulated waste. However, for want of a better shorthand description, the distinction between these two categories in this report is that inert chemical waste can be sent to landfill sites without further treatment. Regulated waste represents the category of chemical waste that has to be sent to special storage sites because it is either corrosive or toxic. The final category, referred to in the tables as mixed industrial waste is a catch-all classification so that if the waste does not fit into any of the other categories it will appear here. Usually this consists of wastes such as discarded packaging and general housekeeping waste.
6. It is important to recognize that the data presented in the input-output tables represent the total burdens that have been assigned to the output product from the system. The inputs should not be regarded as the inputs that are incorporated into the final product; they are inputs to the production system.
7. The hydrocarbon feedstocks used in the production of all organic materials represent a consumption of materials (crude oil or gas) that could be used as a fuel. Indeed within many organic processing sequences, unwanted products are frequently incinerated with energy recovery, a process which corresponds to a conversion of feedstock energy to fuel. In the calculations and in the presentation of results, hydrocarbon feedstock materials are accounted for in energy terms (e.g. MJ) rather than mass terms (e.g. kg) so that the conversion of feedstock to fuel can be readily taken into account. In the final results, the feedstock measured in energy terms can be readily converted to mass terms using the factors shown in Table A8.
8. The input-output tables show a raw materials input of sulphur as SO 2 . This refers to sulphur dioxide recovered from other processes, principally metallurgical smelting, and used to produce sulphuric acid. In the calculations, no burdens have been attributed to this input; it is assumed that all burdens will have been assigned to the main product from the primary process.
9. The raw materials tables show a number of different entries for water. Data were requested with process water separated from cooling water and for cooling water, the source of the water was requested. In general, process water is derived from purified sources but cooling water, which represents by far the greatest contributor, is often pumped directly from rivers, wells and, sometimes, the sea and after use is returned to these sources. Many plants use a captive recirculating system for cooling water and for these plants, data was requested for the total amount of cooling water passing into the process and not just the amount of water used to top-up the system.
10. The input-output tables are simply a listing of the data for which information is available. Such tables should not be regarded as a comprehensive environmental description of the system but only a description of the characteristics which are currently monitored. Furthermore, the inclusion of a parameter in the input-output tables should not be taken as an indication that it produces some undesirable environmental effect. For example, mineral waste usually refers to the quantities of waste rock that were moved during mining operations; in many mining processes, this waste rock is simply shifted to a different location within the mine and will be undetectable to an outside observer. When interpreting the data, the onus is on the user of the data to demonstrate that the parameter possesses some physical significance; it must not be assumed that entries in input-output tables automatically imply some environmental effect.
11. In the input-output tables there is frequently a high output of sodium and chloride ions in the water emissions. This arises principally from those plant sites close to the sea or to tidal rivers. In such cases the sodium and chloride ions are discharged directly to sea water.