Artificial fertiliser biggest contributor to bread’s carbon footprint
Wednesday 03 May 2017
University of Sheffield researchers have calculated that ammonium nitrate fertiliser accounts for 43% of the greenhouse gas emissions produced during the manufacture of a supermarket loaf ‘dwarfing all other processes in the supply chain.’
Looking at the emissions associated with the wheat-to-bread supply chain and reporting their findings in the journal Nature, Sheffield researchers assessed “primary data for all the processes involved in the farming, production and transport systems that lead to the manufacture of a particular brand of 800g loaf.” They found that more than half of the emissions associated with industrial bread production occur at the wheat growing stage, highlighting the “Dependency of bread production on the unsustainable use of fertiliser.”
Although they can dramatically boost the growth of arable crops and vegetables, synthetic fertilisers consist of substances such as methane, ammonia and nitrogen, which have a global warming potential higher than that of carbon dioxide when these components are released into the atmosphere.
Researchers at the University’s Grantham Centre for Sustainable Futures said they hope the research will help identify areas for action when it comes to reducing the carbon footprint of the global food system; this is urgently needed if we are to tackle climate change and work towards global food security.
Dr Liam Goucher, who carried out the study, said, “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.
“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 fertiliser 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.”
Researchers said the study highlights the major conflicts inherent in the current agri-food system, which is primarily geared towards making money, and not to providing sustainable global food security, or protecting the environment for future generations or other species. Professor Lenny Koh, a co-author on the report, said, “The findings raise a very important issue – whose responsibility is it to bring about the implementation of these interventions: the fertiliser 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.”