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?