Carton makers fall foul of LCA trap

Milk cartons perform better than plastic bottles on air emissions, consumption of energy and non-renewable resources and disposal volume, but lose out on discharges to water, according to a life-cycle assessment (LCA) commissioned by the Alliance for Beverage Cartons and the Environment (ABCE). But the ABCE then makes a controversial comparison of the liquid discharges with the other impacts - without any scientific justification.

Conducting LCAs and reporting on their results is fraught with difficulties. The European Commission's Strategic Analysis in Science and Technology Unit (SAST) warned of the problems last year (ENDS Report 219, pp 25-26 ). The science is still young and, although the "inventory" stage is now well established, consensus on the "aggregation" and "valuation" of the data compiled in the inventory is a long way off. It is in these areas that the ABCE's interpretation of the results is at its most dubious.

The inventory stage was conducted by the packaging consultancy PIRA. The study compared two-pint cartons for milk with high-density polyethylene "polyjars" - a market where "reusability" does not have to be addressed. Pints of milk are generally sold from supermarkets in cartons, while four- or six-pint containers are made of plastic. But a battle is under way in the two-pint market as retailers switch from cartons to polyjars - one of the underlying reasons for the ABCE's study.

PIRA used industry average data for the polyjar, but company-specific data for cartons. SAST has criticised this practice because company-specific information tends to come from well managed firms. Indeed, PIRA used data from carton-board producer Stora which "takes into account moves to clean up effluent".

But PIRA also warned against using its data to make comparisons. It says that "care must be taken when making comparisons between the systems as different system boundaries may have been used during the data collection procedures." PIRA itself did not aggregate the various impacts to the different media.

However, the ABCE carried out an aggregation purely on the basis of the weight of the two containers. For example, it aggregated emissions of CO2 with emissions of VOCs, CO, NOx, SO2 and dust into a single indicator. This is a common but scientifically unjustified approach because each pollutant may have a very different environmental impact.

After aggregation, the comparison was as follows:

Beverage cartons are made mostly from paper, which is counted as a renewable resource. In addition, most of the energy used in paper production is generated from renewable sources. On the other hand, the polyjar scores badly because it is made from oil and fossil fuel is used in its production.

However, discharges to water from pulp mills count heavily against the carton - despite the exclusion from the study of discharges of chlorinated organics on the grounds of poor data.

But the ABCE committed an even more bewildering error is in its attempt to compare the aggregated categories. It based its argument on a list of priorities purportedly agreed at the 1992 Earth Summit in Rio. Global warming tops this list, it says, which "helps when assessing the environmental significance of the outputs into air and water." The ABCE then implies that cartons are "environmentally sound" because air emissions are "consistently lower by significant amounts for the carton than for the HDPE alternative."

The ABCE is on very thin ice with this argument. Firstly, although the Rio conference made CO2 emissions a priority issue, it also outlined other priorities. No statement was made that CO2 emissions should be tackled first without concern for other pollutants. Secondly, the contribution to global warming made by the manufacture and use of beverage containers may be less significant than their contribution to water pollution. In many cases the best overall environmental improvements can only be made at the expense of increased releases of one or more individual pollutants.

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