Raw Material Sourcing
Ore mining of metals, which is predominantly open cast mining, results in a lasting scar on the landscape. The fraction of metal extracted from the ore (1 to 2%) exacerbates this problem. Crude oil in contrast is extracted via a bore-hole and consequently has much less of a lasting effect on the landscape. Furthermore, almost 100% of crude oil is subsequently converted into useable products e.g. oils, fuels and chemicals.

Raw Material Processing and Pipe Material Production
The refining and smelting of metals consumes far more energy than the refining of oil and polymerisation of plastics. The emissions from metals production processes in terms of soil, air and water pollution also far exceed the impact of oil refining and plastics polymerisation. The emissions into soil from metal refining are increased due to the large fraction of the electrical energy used for smelting being generated by coal combustion. The ore residues together with the ashes from power production have a considerable polluting effect on the landscape. Emissions from these metal refining processes also have an impact on both water and air pollution due to the generation of sulphur dioxide, carbon dioxide, other gases and airborne particles, plus sulphates and other solid/chemical emissions. In contrast, the oil refining and plastics polymerisation processes generate very little in the way of emissions since they are essentially fully integrated processes.

Pipe and Fitting Manufacture
For both metals and plastics the production of pipes and fittings involves raising the temperature of the raw materials above their melting/softening points. The temperatures involved however are much higher for metals in comparison with plastics, with consequential differences in energy efficiency ratings.

Pipe Systems Installations
The actual weight of a piping network is not considered to be a factor in building installations. But it is important in assessing the overall energy efficiency of the piping system. Due to their much lighter weight, plastic materials exhibit a distinct advantage over metal pipes in this respect. The total energy consumption to manufacture metal pipes required for the piping system of for instance a 16-family housing complex is significantly higher than for plastic pipes. The following figure shows the energy equivalent value which takes into account the total weight and the associated energy consumed in producing the complete piping network in each of the different materials.

Energy equivalent value of the complete piping network of a multiple dwelling with 16 appartments acc. DIN 1988 for the individual pipe materials

Applicational Life Expectancy
Two considerations should be taken into account with respect to the applicational life expectancy of a piping installation. First of all, the lifetime of a system delays the need for replacement, and hence reduces the environmental impact on a time-dependent scale. Secondly, when a material has completed its useful applicational life, its environmental impact is reduced if it can be recycled. Both metal and polyolefin thermoplastics, including Polybutene-1, can be recycled, however since the plastic piping systems are expected by standards accreditation to provide a service life in excess of 50 years, it is difficult to reliably predict the environmental impact of recycling on such a long timescale.

Quantitative Assessment of Emissions
To quantify the environmental impact of emissions, the Technical University of Berlin developed a standardised comparison method referred to as VENOB (Vergleichende Normierende Bewertung). This environmental analysis is based on scientific facts and compares the energy consumption in relation to emissions in air, water and soil during each stage from raw material sourcing to the installation of the piping system. The University evaluated six different materials used for drinking water pipe installations according to DIN 1988 part 3 on the basis of a 16-family housing complex with central hot and cold water distribution at 4 bar pressure. The following 3 figures illustrate the standardised comparison (VENOB) of the various pipe materials impact on the environment in terms of soil, water and air emissions.




Standardised comparison (VENOB) of various pipe materials, impact on the environment - emissions in soil




Standardised comparison (VENOB) of various pipe materials, impact on the environment - emissions in water




Standardised comparison (VENOB) of various pipe materials, impact on the environment - emissions in air