Background, aim, and scope
The aim of this study has been to estimate the carbon footprint of bread produced and consumed in the UK. Sliced white and wholemeal bread has been considered for these purposes and the functional unit is defined as “one loaf of sliced bread (800 g) consumed at home”. The influence on the carbon footprint of several parameters has been analysed, including country of origin of wheat (UK, Canada, France, Germany, Spain and USA), type of flour (white, brown and wholemeal) and type of packaging (plastic and paper bags). The effect on the results of the type of data (primary and secondary) has also been considered.
Materials and methods
The carbon footprint has been estimated in accordance with the PAS 2050 methodology. The results have also been calculated following the ISO 14044 methodology to identify any differences in the two approaches and the results. Primary data for the PAS 2050-compliant study have been collected from a UK bread supply chain. Secondary data have been sourced from the UK statistics, life cycle inventory databases and other published sources.
Results and discussion
The carbon footprint results range from 977 to 1,244 g CO2 eq. per loaf of bread. Wholemeal thick-sliced bread packaged in plastic bags has the lowest carbon footprint and white medium-sliced bread in paper bag the highest. The main hot spots are wheat cultivation and consumption of bread (refrigerated storage and toasting), contributing 35% and 25% to the total, respectively.
The carbon footprint could be reduced on average by 25% by avoiding toasting and refrigerated storage of bread. Further reductions (5–10%) could be achieved by reducing the amount of waste bread discarded by consumers. The contribution of transport and packaging to the overall results is small. Similar trends in the results are also found in the study based on the secondary data and following the ISO 14044 methodology.
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In the context of this study, primary (specific) data are those collected directly from a player in the bread supply chain and secondary (generic) data are those sourced from literature, LCI databases or other sources. Primary data are compliant with PAS 2050. Wherever necessary and possible, the secondary data have been adapted for the UK bread supply chain considered in this study to reflect the UK situation (e.g., background energy mix etc.).
However, it should be noted that, typically, the contribution of infrastructure to the overall results is insignificant and this is likely to be true for the bread system given the high volumes of production and a long life of equipment.
The highest tier approach set out in the IPCC Guidelines for National Greenhouse Gas Inventories for non-CO2 emissions from livestock and soils (IPCC 2006).
Twelve million loaves are sold each day, 80% of which is sliced and packaged; assuming the average carbon footprint of 1.18 kg CO2 eq./loaf (obtained in this study) gives: 12 x 106 x 0.8 x 1; 18 x 10−3 x 365 = 4.1 million t CO2 eq.year−1.
Diastatic power of a grain refers to the grain's ability to break down starches into sugars.
Based on own measurements of products available on the market.
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This study was funded by EPSRC, NERC and Carbon Trust as part of the CCaLC project (grant no. EP/F003501/1) and by Sustainable Consumption Institute at the University of Manchester. The authors gratefully acknowledge this funding.
Responsible editor: Shabbir Gheewala
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Espinoza-Orias, N., Stichnothe, H. & Azapagic, A. The carbon footprint of bread. Int J Life Cycle Assess 16, 351–365 (2011). https://doi.org/10.1007/s11367-011-0271-0
- Carbon footprint
- Global warming potential
- ISO 14044
- PAS 2050