LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PARALLEL SESSION 4B: DIET 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
A novel nutrition-based functional equivalency metric for
comparative life cycle assessment of food
Martin C. Heller * , Gregory A. Keoleian
Center for Sustainable Systems, University of Michigan, Ann Arbor, MI, USA
* Corresponding author. E-mail: mcheller@umich.edu
ABSTRACT
Establishing functional equivalency between disparate food types remains a methodological challenge for comparative environmental
impact studies. In this paper, we demonstrate the influence of functional unit choice on the life cycle energy and greenhouse gas
emissions for a variety of food types. We introduce a novel functional unit approach utilizing the NuVal nutritional quality scoring
system. NuVal combines over 30 micro- and macro-nutrient properties of foods into a single score weighted on the basis of the
effects that nutrients have on health. “Nutritional weighting” of environmental impact scores expressed per unit of food energy
clearly influences the ranking of foods based on their environmental impact. The nutritionally weighted environmental impact indicator
provides a useful means to holistically account for nutritional quality in comparing and differentiating foods using life cycle
assessment.
Keywords: functional unit, nutrition, health, ONQI, NuVal, nutritional quality index
1. Introduction
Establishing functional equivalency has always been a methodological challenge in life cycle assessment
studies of foods. Food LCAs often use the system reference flow (mass or volume) as the functional unit
(Schau and Fet, 2008). Functional units are chosen to serve the goal and scope of the study (ISO, 2006), and
often a mass- or volume-based functional unit is sufficient for a stand-alone system assessment. However,
this reference flow basis does not fully capture the primary function of foods – delivering nutrition – making
comparisons between different food types in consumer-oriented analyses difficult. Water content of foods
can also play an important role with mass- or volume-based functional units as water adds mass or volume
without effecting quality such as nutrient or energy content. Numerous approaches have been put forth to
address this food functional equivalency challenge. Quality-based correction factors such as “energy corrected
milk” (e.g., Cederberg & Mattsson, 2000) or “protein corrected wheat” (e.g., Audsley, 2003) assist in
normalizing natural variations in qualities that influence value and processing. Martinez-Blanco, et al.,
(2011) use antioxidant compound content as a functional unit when comparing cultivation and fertiliser options
in cauliflower production. In a recent literature review, de Vries and de Boer (2010) compare impacts
of livestock products on the functional unit basis of “protein delivered” and “average daily intake,” allowing
comparison across disparate food types. Such single nutrient based functional units have merit for particular
study goals, but the fact remains that healthy nutrition is complex and multi-dimensional. Schau and Fet
(2008) propose the need for a quality corrected functional unit that incorporates fat, protein and carbohydrate
content, as well as potentially other quality functions, as deemed necessary.
The Overall Nutritional Quality Index (ONQI) is a tool designed to aid consumers in making wellinformed
dietary choices (Katz et al., 2010). Developed by nutrition and public health experts, the ONQI
algorithm combines into a single score over 30 entries representing both micro- and macronutrient properties
of foods, weighted on the basis of the effects (both promotional and detrimental) that nutrients have on
health. The index has been validated through expert panel rankings and statistical diet comparisons, and has
been implemented in over 500 supermarkets across the US as NuVal.
In this paper, we explore the utility of ONQI as a nutrition-based functional equivalency metric in environmental
impact assessments of food. Using the NuVal score (ONQI adjusted to values from 1-100) as a
nutritional weighting factor allows comparisons of environmental impacts of foods on the basis of their relative
contribution to a healthy diet. These results are contrasted with results based on single-dimension functional
units (e.g., weight, serving, kg protein, and energy content).
2. Methods
2.1. Food nutritional information
Nutritional and serving size information for the variety of foods found in Table 1 were from the USDA
Food and Nutrient Database for Dietary Studies, v 5.0 (Ahuja et al., 2012), accessed via the “What’s In The
Foods You Eat” Search Tool v. 5.0 (USDA, 2012). Nutritional data are for foods as listed in Table 1. These
were matched as closely as possible to LCA and NuVal data.
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