Analysis of the production of a loaf of bread—growing wheat, milling flour, baking, etc.—reveals which part of the process contributes the most greenhouse gas.
The findings, published in the journal Nature Plants, show ammonium nitrate fertilizer used in wheat cultivation contributes almost half (43 percent) of the greenhouse gas emissions—dwarfing all other processes in the supply chain.
“Consumers are usually unaware of the environmental impacts embodied in the products they purchase – particularly in the case of food, where the main concerns are usually over health or animal welfare,” says Liam Goucher, a research fellow at the University of Sheffield who carried out the study.
“There is perhaps awareness of pollution caused by plastic packaging, but many people will be surprised at the wider environmental impacts revealed in this study.
“We found in every loaf there is embodied global warming resulting from the fertilizer applied to farmers’ fields to increase their wheat harvest. This arises from the large amount of energy needed to make the fertilizer and from nitrous oxide gas released when it is degraded in the soil.”
How to produce sufficient healthy and affordable food for the world’s growing and more demanding population, while protecting the environment is one of the biggest challenges of the 21st century.
An estimated 60 percent of agricultural crops grow with the use of fertilizers. Although they can dramatically boast the growth of plants and vegetables—assisting the growing demand of food yields—fertilizers consist of substances and chemicals such as methane, carbon dioxide, ammonia, and nitrogen. The emissions from these substances in synthetic fertilizers contribute to greenhouse gases.
“Our findings bring into focus a key part of the food security challenge—resolving the major conflicts embedded in the agri-food system, whose primary purpose is to make money not to provide sustainable global food security,” says Peter Horton, professor and chief research officer at the University of Sheffield’s Grantham Centre for Sustainable Futures and corresponding author of the paper.
“High agricultural productivity—necessary for profit for farmers, agri-businesses, and food retailers, whilst also keeping prices low for consumers—currently requires high levels of application of relatively cheap fertilizers.
“With over 100 million tons of fertilizer used globally each year to support agricultural production this is a massive problem, but environmental impact is not costed within the system and so there are currently no real incentives to reduce our reliance on fertilizer.”
Researchers used an advanced life-cycle assessment tool, SCEnAT, developed by coauthor Lenny Koh, professor and director at the Advanced Resource Efficiency Centre at the university’s management school.
“…whose responsibility is it to bring about the implementation of these interventions: the fertilizer manufacturer, the farmer, the retailer, or the consumer?
“This tool handles large and complex data sets and yielding data on the environmental impact, including greenhouse gas emissions of all the stages in the supply chain,” says Koh. “The tool identifies the processes that yield the most impact—the hotspots.
“The findings raise a very important issue—whose responsibility is it to bring about the implementation of these interventions: the fertilizer manufacturer, the farmer, the retailer, or the consumer?
“There is a growing recognition for a range of industrial processes of the notion of extended producer responsibility—the producer being responsible for downstream impact, expanded to the idea of shared producer and consumer responsibility. The consumer is key, whether being persuaded to pay more for a greener product or by applying pressure for a change in practice.”
The paper also highlights the available solutions that could potentially reduce these impacts in the future.
“The fertilizer problem is solvable through improved agronomic practices,” says coauthor Duncan Cameron, professor and co-director at the P3 Centre for Translational Plant and Soil Science. “These harness the best of organic farming combined with new technologies to better monitor the nutritional status of soils and plants and to recycle waste and with the promise of new wheat varieties able to utilize soil nitrogen more efficiently”.
Source: University of Sheffield