Paper or plastic? The Devil’s work

For some environmental activists, plastic disposables are the Devil’s work. Paper or biopolymer disposables and reusable items are “obviously” better for the environment, they may say. However, it can be “devilishly” difficult to make reliable comparisons.

A typical controversy is whether to replace, with different products, the cups and trays made of expanded, closed-cell polystyrene foam–sometimes mistakenly called Styrofoam, a Dow Chemical trademark for slabs of extruded foam. The main alternatives are reusable cups and trays made of glass, solid plastics, metals and ceramics, and disposable cups and trays made of paper, biopolymers and composites.

Reliable comparisons will weigh several environmental impacts. Those include at least energy consumption, greenhouse-gas emissions, water and air pollution of many types, human, animal and plant toxic exposures, soil erosion, mineral extraction residues and side-effects, stratospheric ozone depletion, and eutrophication of water bodies. They need to examine product life-cycle and cost factors for raw materials, manufacturing, transportation, cleansing for reuse, recycling and disposal.

For some factors, there will be more than one option. Options that reduce impacts may increase costs. The more costly options are less likely to appear in common practice, making it hard or impossible to know their real prices. There will sometimes be big uncertainties, such as total cycles for a reusable item. There will typically be more than one type of environmental impact. Factors that cut some impacts may boost others.

Preferences among products involve relative values for multiple impacts. A theory to evaluate such situations began to appear in the 1970s, expressed through the mathematics of linear algebra and multivariate calculus. So far, however, textbooks on so-called “eco-efficiency” avoid the ugly foundations: large uncertainties that sometimes turn elegant theory into practical rubble. Impact studies often try to elide these problems.

Even comparisons limited to a single type of impact can substantially disagree. For example, van der Harst and Potting (2013) reviewed ten life-cycle studies comparing disposable cups for greenhouse-gas emissions. The studies produced conflicting estimates for the same types of cup. Van der Harst and Potting were unable to identify “a best or worst cup material.” They traced conflicting results to differing inputs, including “weight, production processes, waste processes, allocation options and data.”

Among the comparisons van der Harst and Potting reviewed was Ligthart and Ansems (2007), a sophisticated work that considered ten types of environmental impact. Those were consolidated into a single impact-measure by adding the so-called “shadow costs” of impacts, which multiply estimated market prices to mitigate impacts by amounts of materials needing mitigation.

A key weakness of such an approach is information that may be unknown or unknowable. For example, mitigation of farm fertilizer as a eutrophication impact may require changes in practices and technologies that have never been tried on a large scale. Unless there are widely applied mitigations–such as scrubbers for power-plant smokestacks–”shadow cost” estimates will lack a reliable base of knowledge, turning elegant theory into practical rubble.

Such problems likely influence conflicts among life-cycle studies of disposable cups that van der Harst and Potting documented. With care, one might be able to estimate individual impacts, but knowledge may be lacking to understand impact relations or assign weightings and combine them–for example, to predict fair and effective prices that might be charged, rather than arbitrarily banning some types of cups but not others.

Don’t just do something. Stand there!

– Craig Bolon, Brookline, MA, May 28, 2014

Eugenie van der Harst and José Potting, A critical comparison of ten disposable-cup life-cycle analyses, Environmental Impact Assessment Review 43:86-96, 2013

T.N. Ligthart and A.M.M. Ansems, Single-use cups or reusable drinking systems: an environmental comparison, Netherlands Organization for Applied Research (TNO), 2007

PWC France, Life-cycle assessment: three approaches to commercial fish boxes, Price-Waterhouse Coopers, 2011

Shunrong Qi, Lan Xu and Jay Coggins, Deriving shadow prices of environmental externalities, Department of Applied Economics, University of Minnesota, 2004

Rolf Färe, Shawna Grosskopf, C.A. Knox Lovell and Suthahip Yaisawarng, Derivation of shadow prices for undesirable outputs, Review of Economics and Statistics 75(2):374-380, 1993

Gjalt Huppes and Masanobu Ishikawa, ed., Quantified Eco-Efficiency: An Introduction with Applications, Springer, 2010

Jukka Hoffrén, Strengths and weaknesses of eco-efficiency, Statistics Finland and Ministry of the Environment, 2012

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