Climate change, population and economic growth are putting increasing pressure on our planet’s water resources, leading to ever more people living in water scarce areas. Water supply and use has a seemingly underappreciated and complex relationship with climate change: it is affected by climate change, however also part of its driver, as its supply, end-use and treatment consumes energy and is responsible for the emission of a considerable amount of greenhouse gases. For the linkages between water and energy use, the term “water-energy nexus” has evolved. Despite water end-use being the largest contributor to energy consumption in the water value chain, its energy consumption has gained only little attention in research, especially industrial water end-use. The first data chapter of this work, Chapter 3, delivers an estimate of the water-related energy use in industry, taking the UK manufacturing sector as an example. The remaining work focusses on one of the most water and energy-consuming sectors, the food and drink sector – in this work comprising the food and drink manufacturing and the food service sectors. The overall aim is to understand how the food and drink sector’s water use can be decarbonised and water resources most efficiently managed. Heat recovery from waste and by-product streams as well as the (water-) efficient use of agri-food by-products is explored for this purpose. A Life Cycle Assessment (LCA) methodology is applied to take a holistic view on these strategies, and to detect and avoid potential environmental trade-offs arising from their implementation.

Chapters 4 and 5 look at the most water-consuming and energy-intensive product category within food and drink manufacturing – distilled spirits. Chapter 4 provides an LCA of Scottish single malt whisky based on primary data from Arbikie distillery, focussing on water scarcity and carbon footprints. It investigates different options for the use of by-products – from livestock feed and bioenergy pathways, to compensate for the whisky footprint and finds the feed use-route to offer the highest water scarcity footprint offsets due to the replacement of irrigated imported feed crops such as soybeans. Chapter 5 explores several configurations for recovering heat from process and by-product streams in a distillery to lower its energy consumption and water scarcity impacts, combining environmental with financial criteria through the eco-efficiency methodology. Results show benefits for both carbon emissions and water scarcity impacts, while at the same time offering a financial payback of under 2 years. However, greater savings would be achievable through the inclusion of heat and water sinks outside the distillery.

Chapters 6 and 7 address commercial kitchens as part of the food service sector, studying the environmental savings potential through heat recovery from their drain water based on primary data from a demonstration site. Comparison of the installation’s LCA footprint with operational emission savings find the great majority of kitchens in the UK to be suitable for heat recovery from an environmental point of view; environmental savings were also found to increase through the use of low-impact materials for the equipment. In order to provide guidance and facilitate uptake of heat recovery in commercial kitchens, Chapter 7 presents a publicly-available calculator designed for kitchen managers to estimate individual heat recovery, environmental and cost savings potential.

This work demonstrates that waste (water) heat recovery can significantly contribute to a reduction of overall and water use-related carbon emissions of the UK food and drink sector, though requires the engagement of businesses and the support by policy-makers. Water scarcity footprints add value to a holistic evaluation of water and energy-efficiency measures and should be included in the feed/food vs bioenergy discussion to avoid potential trade-offs for global water scarcity issues.