This is a Roast Beef Sandwich 1 How much water was used to make this sandwich? Water use in Agriculture 2 How much water in a roast beef sandwich? All over the world, in every country, agriculture uses the most amount of water. A United Nations study of global averages calculated that 70% of total water consumption goes to agriculture, mostly irrigation. By contrast the domestic use of water in homes is only 5% to 10% of total water consumption, depending on how “developed” the country is. Beef Cattle on the Farm 3 How much water in a roast beef sandwich? To get beef, we need to raise a cow! Some cows weigh up to 900kg. It takes 13,500,000 litres of water to raise a cow for the land, feed, drinking water, and cleaning. To roughly calculate the amount of water we actually need, let’s calculate the weight of beef we need: =30g slices X 2 slices each X number of people. Now use that value to calculate the amount of water: [13,500,000L/900kg] X weight (kg) = L water needed for our sandwiches Raising cows for beef uses the highest amount of water compared with other agricultural product Let’s compare water usage… Ask your classmates to guess the order! 4 How much water in a roast beef sandwich? For 1kg of… Beef = 15 cubic meters of water Lamb = 10 cubic meters of water Chicken = 6 cubic meters of water Palm Oil = 2 cubic meters of water Wheat = 1.5 cubic meters of water Oranges = 1 cubic meter of water Beans = 1 cubic meter of water Carrots = 1 cubic meter of water Potatoes = 1 cubic meter of water Water use in the Bakery 5 How much water in a roast beef sandwich? Now let’s go to the bakery to buy our bread. Let’s say we need two loaves of sliced bread which each take approximately 53 litres of water to make when you include the cleaning and industrial processes required in a commercial bakery. =another 106 litres of water Water use in processed foods: 6 How much water in a roast beef sandwich? Now let’s go to the store to buy the mayonnaise and mustard. These are processed foods made in commercial food manufacturing plants. We need to add in the water used for keeping the factories and their transportation trucks clean to a safe standard, as well as what’s actually used in the production process. =32 litres per package, one for the mayo and mustard. Water in the Kitchen 7 How much water in a roast beef sandwich? We have all of our ingredients now, so we can go to our kitchen to prepare the sandwiches. First, we must wash our hands. Anyone who prepares food for others in a commercial kitchen must wash their hands for a minimum of 20 seconds to ensure they are thoroughly clean and won’t make people sick by contaminating the food. = another 3 litres of water per person. Cleaning the Kitchen 8 How much water in a roast beef sandwich? Our kitchen needs to be cleaned each day using three 5 gallon buckets: one to wash with soapy water, one to rinse the soap and food away and the last one with bleach and water to kill any bacteria on the preparation table surfaces and equipment. =15 gallons =68 litres of water. To Make Our Beef Sandwiches 9 How much water in a roast beef sandwich? How many litres of water in total?