HOW LIFE CYCLE ASSESSMENTS MEASURE THE SUSTAINABILITY OF FOODS

Our food choices have associated environmental impacts. Understanding how and why foods differ in their effects can help us make better, more informed decisions that advance the sustainability of the food system.

Defining Sustainability

Put simply, “a sustainable system is one which survives or persists,” which means that the sustainability of a system is a question of prediction rather than definition.¹ Perhaps the best-known operational definition of sustainability comes from the Brundtland Commission report, which states that sustainable development requires meeting the “needs of the present without compromising the ability of future generations to meet their own needs.”² Another popular conceptualization of sustainability is the triple bottom line, which balances priorities across people, planet, and profit.^3,4

Threats to Sustainability

Global warming,^5,6 increased demands for food due to population growth,⁷ and significant environmental effects associated with dietary choices^8-10 pose threats to the sustainability of the current food system. Without changes being made, future generations are unlikely to have the same resources and conditions necessary to meet their needs as we have today. The short-term economic aspects of food systems continue to drive the majority of decision-making.

Even if sustaining the current food system indefinitely were feasible, it is questionable if that approach would be desirable. With about 800 million undernourished people and more than 2 billion people with micronutrient deficiencies,¹¹ the current food system fails to meet its most fundamental purpose of feeding humanity. Meeting that goal will be an even greater challenge as the global population grows to 9 billion people by 2050.⁷ Meanwhile, obesity, driven in part by the overconsumption of unhealthy, yet affordable and effectively marketed food,¹² continues to increase and has more than doubled in 70 countries since 1980, leading to adverse health effects.¹³ The environmental effects associated with food production also cause undesirable outcomes including global warming, deforestation, water eutrophication, pollution, and soil depletion, all of which will also increase as food production increases, unless significant changes are made.

A Sustainable Food System

A sustainable food system would be one that either eliminates these problems, or reduces their magnitude to levels that can be managed over the long term. A sustainable food system would be one that would respect the limits of our planet and stay within a “safe operating space for humanity,”¹⁴ essentially staying within the ecological carrying capacity of the earth. Options to do so include dietary change, improvements in technology and management, and reducing food loss and food waste; although, no single change is enough on its own.¹⁵ In general, diets are more sustainable when they are comprised of whole, plant-based foods that are in season locally and are efficiently produced, with minimal food lost or wasted.¹⁶

Life Cycle Assessment

To quantitatively evaluate the effectiveness of methods to improve the sustainability of the food system, a method of measuring sustainability is required. One of the most widely used and versatile tools for assessing the environmental effects of products, including foods, is life cycle assessment (LCA). This methodology is designed to provide a way to quantify the resource usage and pollution emitted across the entire life cycle of a product, from extraction of raw materials through the ultimate disposal of what is left from the product. These stages typically are considered to be raw material extraction, processing, manufacturing, distribution, use, and disposal-- although there are variations depending on the product and industry. For example, LCA of food would include raw materials extraction (e.g., for processing into fertilizer), but would also incorporate farming, retail sales, meal preparation, and disposal of leftovers for a complete life cycle.

Performing a complete LCA of any product, including food, is a time, labor, and data intensive process that requires skilled researchers and cooperative businesses. Ideally, onsite measurements will quantify all resource inputs and pollution outputs at every stage of the life cycle. LCA researchers often must rely on existing studies for upstream data, such as for fertilizer, diesel, and electricity usage at the farm, and for the environmental burdens associated with transportation. Fortunately, LCA practitioners can use extensive databases along with software for such information in order to get the most complete picture possible of the life cycle impacts without unreasonable burdens. The collection of the data from across the life cycle of a product is known as a life cycle inventory (LCI). Once the LCI is completed, the data must be characterized to translate into environmental impacts, typically through the use of LCA software which is also used for data collection and organization. There are numerous characterization methodologies to choose from, each different in its assumptions regarding things such as time horizons to calculate radiative forcing of greenhouse gas emissions. LCA is also an iterative process, so as researchers gather, characterize, and interpret data, they may uncover information that leads to changes in other aspects of the LCA.

LCA of Soy

As an example of how LCA has been applied to food, consider the Dalgaard et al. paper “LCA of Soybean Meal” published in 2008.¹⁷ Soybean meal has a co-product of soybean oil; therefore, the researcher had to decide how to divide the total environmental impact of the system between the two. The solution in this case was to use a “consequential” approach, which meant assigning the entire burden of the system to the soybean meal, but also expanding the system to take credit for the avoided production of an oil that the soybean oil would displace, which in this case is palm oil. That assignment itself requires its own “system expansion” since the co-product of palm oil (palm kernel meal) displaces soybean meal, creating a never-ending loop. The amounts displaced are quickly reduced, so the loops do not have to continue indefinitely to arrive at a satisfactory value for the environmental impacts assigned to soybean meal. Ultimately, the researchers found a global warming potential value of 0.721kg CO₂ equivalents per kilogram of soybean meal with their palm oil displacement scenario, although this value could be even lower if the displaced oil was canola instead of palm. This study reflects the complicated and interconnected nature of the food system wherein changes in demand for one product can influence the production of others that lack an obvious connection.

Insights from LCA

LCAs of foods have provided insights into the nature of the food system, and what matters most when attempting to reduce environmental effects associated with food choices. Some LCA conclusions are intuitive, such as plant-based foods having relatively low environmental impacts compared to other types of foods because they require fewer resources.⁸ Other LCA conclusions are counterintuitive, such as processing and transportation of food having a smaller influence than production on its ultimate environmental impact, contrary to public concern with “food-miles.”¹⁸ Sometimes the nuance of how the comparisons are framed, such as the functional unit used as the basis for comparison, also influences the outcome. For instance, soy protein isolate (SPI) on a mass basis (per kilogram) has a global warming potential that is roughly equivalent to peanut butter. However, when the functional unit also accounts for the true ileal digestibility and serving size, SPI has a far more favorable comparison, roughly 1/5 of the global warming potential of peanut butter.¹⁹ In LCA, it is therefore important to make comparisons in a fair way, by using a functional unit that captures the obligatory properties of all products being compared.²⁰

LCA and Sustainability

LCA can help society move toward a more sustainable food system by quantifying and comparing the environmental impacts of food choices. New insights derived from rigorous LCA studies that make fair comparisons and utilize a variety of perspectives should help shape the decisions of diverse stakeholders. Of course, sustainability is more than just environmentalism, so other factors should also be considered. Nonetheless, it remains a powerful tool.²¹ 

References

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