A study from a life cycle analysis firm claims half-gallon milk containers made from high density polyethylene have less of an environmental impact than similar containers made from polylactide acid. But a major maker of the corn-based polymer says the study is flawed.
Franklin Associates Ltd. of Prairie Village, Kan., prepared the study at the request of the Arlington, Va.-based American Chemistry Council's plastics division. The report focuses on energy use, solid-waste generation and environmental emissions.
Released in November, the study used information from PLA supplier NatureWorks LLC, as well as European resin industry trade group PlasticsEurope and the Franklin Associates database.
According to the study, HDPE containers consume 40 percent less energy, produce 28 percent less post-consumer solid waste, and generate 40 percent fewer greenhouse gas emissions than containers made from PLA. They also ranked better in each of those categories than glass bottles and paperboard.
``These findings are both ironic and counterintuitive,'' said Bob Lilienfeld, author of ``Use Less Stuff: Environmental Solutions for Who We Really Are,'' who also edited from 1994 to 2000 a bimonthly newsletter focused on helping people conserve resources and reduce waste.
``The fact that an HDPE milk jug is primarily produced from natural gas but still consumes less energy and generates fewer greenhouse gas emissions than a jug made from a corn-based material is not at all what the public expects or has been led to believe,'' Lilienfeld said.
Much of the reduced environmental burden associated with HPDE containers, he said, stems from the fact that they are ``lighter than containers made from other materials, giving them the ability to deliver the same amount of product while using less material.''
Snehal Desai, chief marketing officer for NatureWorks, said there's no evidence that the results of the study were critically reviewed by external independent experts.
``To compare new materials in their early stage of development with mature materials often leads to a biased comparison,'' Desai said.
In addition, he said, ``the bottle weights used in the study concern us. PLA bottles can be much lower in weight.'' Because of that, the Franklin study creates an ``apples with pears'' analysis, particularly when it comes to greenhouse gas emissions.
He added it is inaccurate to make assumptions about whether PLA bottles will be recycled based on current recycling rates.
``PLA bottles are not recycled today simply because the volumes are too small to make it work from an economic point of view,'' he said.