Abstract
Beer is the most produced and consumed alcoholic beverage in the world, but the agricultural production of its most common ingredient, i.e. malted barley, is a significant contributor to the overall environmental footprint of beer. In addition, food wastage, particularly bread with millions of slices wasted daily, poses a waste management challenge across the globe. This study aims to address both issues through brewing beer with waste bread that would have otherwise ended up in landfill by replacing a portion of malted barley with waste bread. A sourdough pale ale was brewed at various bread percentages to understand how the inclusion of bread changed the sugar profile and fermentability of the beer. The samples were mashed at two different temperatures, 65 °C and 70 °C, to assess the impacts of mashing. It was found that the volume of alcohol produced declined with increasing bread amounts, but brewing with up to 60 wt% bread produced the same volume of alcohol as a standard beer. A life cycle assessment was performed to quantify the change in cradle to grave environmental impact for brewing beers with varying bread percentages with the view to conduct more targeted feasibility studies in the future with waste bread substitution. Significant reductions in emissions were observed as regards global warming potential, terrestrial ecotoxicity, acidification, eutrophication, ozone depletion, and abiotic depletion of fossil fuels. In particular, the global warming potential for the real-life example microbrewery studied in this work was decreased by 7.13% of the total carbon dioxide equivalent annually, demonstrating the environmental advantages of brewing beer with waste bread.