1.  LCA analyses can be massaged according to where one starts and ends one's examination, and the assumptions one makes about how a product is used, treated, and disposed. "Life Cycle Inventory flows," which include inputs of water, energy, and raw materials, and releases to air, land and water, must necessarily be simplified for analytical purposes. The processes assumed for the purposes of analysis do not necessarily correspond to actual practices.

2.  Although there are international standards for conducting LCAs, there are a number of methodological issues, especially when comparing the impacts of radically different materials. This is not to say that comparisons are useless, but they should be taken with a grain of salt.

3. In their narrow focus on one analytical target -- energy use and carbon emissions -- LCA approaches overlook other crucial topics, such as human health and ecotoxicity. LCA analyses look at what are called "mid-point" measures such as the release of greenhouse gases.  They do not cover "end point" measures such as the survival of marine environments.  Thus, according to most sustainability experts, LCA analyses should not be used as the sole determinant of environmental policy.  Rather, they must be considered alongside other data.

4.  Finally, as other readers have noted, the study was sponsored by the Plastic Foodservice Packaging Group, a member of the American Chemistry Council.  Are these disinterested parties or merchants of doubt?

It has been widely reported that the environmental impact of Polystyrene foam (EPS) is less than that of comparable products made of corn and paper. The argument is that manufacturing EPS cups uses less energy and water than manufacturing paper cups, and that an EPS product releases fewer greenhouse gases when it breaks down than does paper.  The people who make these claims support them by pointing to an impressive 150-page study offering a comparative cradle-to-grave analysis of competing products that rules in favor of EPS.  Similar arguments have been made to argue that plastic bags are better than paper for the environment. 

It all sounds very reasonable, but this is a classic bait-and-switch capitalizing on our concerns over global warming.  Consider the following:

1  The study ignores the health effects of polystyrene.  Styrene is toxic, paper is not.  As the authors of
a study on how people define "sustainable" packaging note, toxicity is the very first criterion.

2.  The study ignores the broader ecological impact of polystyrene.  Unlike paper, polystyrene never decomposes into soil.  Rather, it just breaks down into smaller and smaller bits,
microplastics, which have extensive consequences for the food chain.

3.  What the study ignores points to some
broader limitations with Life Cycle Assessment (LCA) analyses, evaluations of the environmental impact of a product that take into account every aspect of its production, from cradle (harvesting of raw materials) to grave (final disposal).  Although immensely useful for understanding the broader environmental footprint of a given product, the LCA approach also has certain blindspots that must be taken into consideration when formulating policy:

refuting the nonsense:

Plastic Bags and Polystyrene are NOT Greener Than Paper