Everhard Industries is a Queensland based manufacturer of a wide range of products for the water and wastewater industry. In particular, the company is a market leader in small systems for wastewater treatment and distributes these products throughout Australia. The company also has an active research program to develop new products and improve product design.

The company manufactures hundreds of different products from a range of materials including plastics, concrete and metals, but it was decided at the onset of this study that an excellent demonstration of the LCA technique would be use it to help differentiate between similar products made from different materials. That is, the company looked to obtain useful information from a comparative LCA on a selected product range to help not just in assessment of manufacture, but in subsequent marketing based on environmental "friendliness" of its products.

A major product line is the 3000 L tanks used for on-site domestic wastewater treatment, such as septic or aerobic systems. This line includes tanks made in precast concrete (Figure 1) and a similar plastic range made from polypropylene (Figure 2).

Tanks made form these two materials are likely to have very different environmental burden profiles. As the concrete tank weighs around 2500 kg, and the plastic 115 kg, they clearly also have significantly different transportation and handling characteristics, factors crucial to the (usually remote) market sector that they serve. However, despite the ultimate and important environmental protection role of these tanks, no study had been undertaken to assess the respective environmental performance of manufacturing and distributing them.

The LCA study should produce the required different environmental profiles for these two products and identify environmental impacts where one product is superior to the other. Such information could also form the basis of a marketing strategy through promoting certain environmental benefits of one product over another.

Information was gathered on the manufacturing operations used to produce the concrete and plastic products. Process trees for the life cycle of the tanks could be then developed, which are presented in Figures 3 and 4. The approach then adopted to carry out the LCA study involved the conventional steps:

• goal definition and scoping;
• defining the system boundaries;
• compiling an inventory of material and energy inputs and outputs;
• assigning emissions to predetermined impact categories and quantifying the emissions where data permitted in terms of a reference substance;
• analysis of impacts to determine significant environmental burden areas.

 For a product differentiation LCA, it is essential to establish a basis for comparison in which the end-use performance delivered by both products is the same. In this study, it was required that this comparison be made on the basis of the use of the tanks in a wastewater system used to treat the same quantity of water over a fixed number of years.

Since the polypropylene and concrete tanks when used for this purpose have the same expected lifetime (15 years), the choice of a functional unit for this study was simplified by choosing tanks which have the same holding capacity - hence the chosen product unit of study was a 3000 L tank. For each product, the system boundary was defined to include the delivery of raw materials to the factory, the manufacture of the tanks and the delivery of the tanks to the customers. The environmental impacts resulting from the operation of the two tanks over their respective lifetimes (end-use stage) were not included as it was considered reasonable to assume that they would be identical.

Environmental burdens in terms of resource consumption and emissions for the raw materials used in the production processes were obtained from an LCA database.

The following environmental impact categories were used to compare the tanks:

• Resource depletion - indicator resource energy consumption
• Global warming potential - indicator equivalent greenhouse gas emissions
• Acidification potential - indicator equivalent sulphur dioxide emissions
• Photochemical ozone creation potential
• Human health impacts.

The first three categories were quantified using the indicator stated and the last two were treated qualitatively.

Transportation stages involve road and sea delivery of raw materials, and road transport of fabricated tanks to customers. The emission factors for use in the transportation models produced for this study were derived from the Australian Greenhouse Office workbooks for transport and fuel combustion activities. Additional information was obtained from the Queensland Road Transport Department and the Ship Owners Association of Queensland.

With respect to assessing operations within the company premises, as the company studied is one that produces a wide range of diverse products, difficulties arise from dealing with allocation of emissions amongst the various products. That is, unlike a single product company, it is clearly not possible to allocate factory inputs and outputs to each product from knowledge of total factory consumption of energy and raw materials, and subsequent discharges.

The manufacturing processes for both the products chosen for the study had, therefore, to be broken down into individual manufacturing steps. Then, providing information was available on energy and material usage on the selected per unit of product (3000 L tank) basis, it was possible to calculate both resource consumption and emissions directly for each of the two units.

To enable direct comparison of the environmental impact of life cycles of the two products, the impact categories previously defined were determined for the following four key stages:

1. Raw material production
2. Raw material transport
3. Manufacture of tank
4. Transport of tanks to customer

The environmental burdens for the impact categories were calculated and the results for the three key impact categories are summarized in Table 1 for an example delivery distance of 250 km. In practice, these tanks are delivered Australia-wide and as mentioned previously, the key transportation issues are the tank weights and ability to stack them.

It can be seen that the concrete tank has the lower resource energy consumption, which stems mainly from the large difference in favour of concrete at the raw material stage. Resource energy is the basic fossil fuel energy used in each stage of the life cycle of the tanks and is inclusive of the energy content of all the feedstock materials used.

Since polypropylene is derived from fossil fuels while concrete is not, the resource energy consumption of polypropylene production is much higher than that for concrete.

Currently, 100% virgin plastic is used in manufacture due to concerns over longevity in the field (in particular with respect to exposure to ultra violet (UV)). If, however, research could lead to incorporation of recycled material, then significant inroads could be made into this impact.

This feedstock energy could be also recovered by incineration of the plastic tank at the end of its useful life, although gains would be partially off-set by a further release of greenhouse gases. Alternatively, recycling of the used polypropylene tanks into other products may be feasible and would return benefits by way of reduced environmental loading as allocated to the plastic tanks in this analysis.

However, by taking the overall LCA picture the plastic tank appears more attractive, in particular when the key factor of transportation to the customer is taken into account. To assess this in more detail, a model devised to analyze this situation and incorporate the crucial impact of the distance the end-product is transported. This model was developed on the assumption that within 50 km of the factory, tanks would be delivered by small and medium sized trucks, and for longer hauls, sets of tanks are delivered on 12 m semi-trailers.

Unlike the concrete tanks, plastic tanks can be stacked (typically 4, as shown in Figure 2) and they have a much lower mass (115 kg) compared to the concrete tank (2500 kg). As a consequence, a typical long-distance (> 50 km) trailer load will be 24 plastic tanks for use in septic systems or 12 for use in aerated systems (more complex inner-components), as compared to only 6 concrete tanks.

As a result, substantial environmental burden savings in terms of overall life cycle emissions per 3000 L tank were identified for those manufactured in polypropylene.

The results of the model are illustrated in Figure 5 for greenhouse gas emissions generated from the life cycle of each 3000 L tank. This environmental burden issue is clearly very much at the forefront of government and public attention, and hence one by which a valid and meaningful comparison can be made. There are also further benefits at the installation site to be gained from the unloading and handling of plastic tanks as compared to concrete tanks. Whilst these benefits were not quantified in Figure 5, for remote and/or offshore regions they are significant (e.g. two operators could handle a plastic tank, whereas a crane is needed for the concrete version).

A comparative LCA has been completed for the production and distribution of 3000 L on-site domestic wastewater treatment tanks manufactured in polypropylene or concrete. As these tanks are destined for use for environmental protection and typically need transporting to remote communities, the study focussed on quantifying the environmental burdens for each type of tank in terms of greenhouse gas emissions, atmospheric acidification and resource energy depletion.

The results from the type of comparative environmental profile conducted can usefully help enable companies such as Everhard Industries to identify the life stages in the production and transport of their products that have significant environmental impacts (and where possible cost saving can be made through better resource utilization).

In addition to significantly better transportation and handling characteristics, the results of the study clearly demonstrated that plastic tanks impose a very much lower environmental burden with respect to greenhouse gas emissions, a key high-profile issue for government and public.

The significantly lower impact of polypropylene tanks in this regard arises from two sources: the high emissions of carbon dioxide associated with the manufacture of clinker for concrete and the higher quantities of fuel on a per unit tank basis used to deliver the end-product to the company's customers.

As a consequence, the study has indicated potential marketing promotional opportunities for the plastic tanks over the concrete tanks due to their much greater environmental "friendliness" with respect to greenhouse gas emissions.

Dr Jim Ness

Mr Venkatesan Narayanaswamy

Prof Ashley Scott

The CIEP gratefully acknowledge the very significant support of the EPA and Everhard Industries, in particular Mr Selwyn Davis, Mr Lou Florakx, Mr Brett Davies and Mr Tony Formica.