Efforts to quantify the carbon footprint of agriculture are often focused on the greenhouse gas emissions resulting from on-farm activities, mostly from fertilizer production and the energy required for use of farm implements. While you, as a climate change-conscious consumer, may place your attention on the environmental impact of your food before it arrives in your grocery bag, a recent study published in the Science of the Total Environment examined the relative impact of different parts of the supply chain (on-farm, processor, retail, and consumer) for potato and tomato products, both fresh and processed. Study authors from the University of Arkansas, led by Ranjan Parajuli, assert that the way food is prepared presents a significant opportunity to reduce greenhouse gas emissions. If the goal is to reduce the overall environmental foodprint, changing the way potatoes are cooked may make more of a difference than how the potatoes themselves were grown.
Consumer demand for sustainable farming practices have been a driver in the creation of organizations like the Potato Sustainability Alliance, allowing growers, processors, and major buyers like McDonalds and Sysco to collaborate and ensure certain environmental standards are followed at the farm level. There appears to be a missing puzzle piece, however, in terms of recognizing the influence of parts of the supply chain after products leave the farm gate, including the impact of the consumers themselves.
A “cradle-to-grave” life cycle assessment, or LCA, can give us a better idea of the impact of different parts of the supply chain. In this particular study, researchers used the LCA method to follow the movement of a common American favorite, the potato, through its entire journey from seed at planting to potato peel in the compost. The benefit of this type of analysis is that an LCA can uncover impacts throughout the production and consumption process that are often overlooked. Rather than simply examining the environmental impact of on-farm production inputs, cradle-to-grave LCA examines the wide range of points along the supply chain, including impacts resulting from the transport to retail, electricity used at retail, food preparation methods, and bio-waste treatments.
As it turns out, the biggest opportunity to reduce greenhouse gas emissions in the life cycle of a potato occurs when the decision is made about how to prepare said potato. Parajuli and his colleagues examined various processed potato products (chips, frozen fries, and dehydrated potato), and found that frozen fries had the highest greenhouse gas emissions, with 38% of the total emissions occurring during the consumer stage of the supply chain. The farming stage, on the other hand, accounted for a mere 18% of the total greenhouse gas emissions (Figure 1). So how does this result show there are opportunities for reducing the carbon footprint? The carbon dioxide equivalent, or CO2-eq, is the unit used to measure that carbon footprint. French fries are generally par-fried prior to being frozen at the processor, then fried again at a restaurant or other food service establishment (which is considered part of the consumer stage in Figure 1). When fries are oven baked instead of a second deep frying step, the result is a 19% reduction in total greenhouse gas impact.