Activity Overview: Every step involved in producing bottled water—from treating the water, making the bottles, and shipping it to its final destination—requires energy, and both the water’s quality and its location affect the amount of energy embedded in the process. For locally sourced bottled water, producing the bottle itself outweighs other energy requirements. However, long-distance transportation increases energy requirements substantially. Other energy requirements include those for processing, bottling, sealing, labeling, and refrigerating. Analysis indicates that manufacturing of water bottles dominates the energy intensity of locally produced bottled water. On the other hand, the energy requirement of long-distance transportation exceeds even those requirements to manufacture the bottle.

The purpose of this activity is to look at the different energy requirements of bottled water, defined as fresh water sold in individual-sized bottles. As discussed above, the two largest energy inputs are bottle production and transportation. Students will use numerical reasoning to analyze different bottled water scenarios. These activities are appropriate for individual and for group work.

The following table is reproduced from the report in Environmental Research Letters on the energy implications of bottled water by Peter Gleick and Heather Cooley. It provides representative information about three journeys of bottled water.

Part 1: Algebraic Expressions

Using the information in the table below, ask students to translate the three different scenarios into algebraic expressions, using variables to represent the energy cost in megajoules (MJ) per liter for a single kilometer. Students' variables may differ, but their expressions should align closely with the examples listed here. For the purpose of this activity, the energy consumed per kilometer for heavy trucks is assumed to be one-half that for medium trucks.

Example variables:

m = medium truck
h = heavy truck
r = rail
c = cargo ship

Example expressions:

Local production: 200m = 1.4
Spring water from Fiji: 100m + 8900c = 4.0
Spring water from France: 100m + 600h + 3950r + 5670c = 5.8
Heavy truck: 2h = m

Part 2: Solving for per kilometer Energy Requirement

Using the algebraic expressions they created in Part 1, ask students to solve for each variable. The solutions below have been rounded where appropriate.

Medium trucks:

200m = 1.4
m = 0.007

Heavy trucks:

2h = m
2h = 0.007
h = 0.0035

Ship:

100m + 8900c = 4.0
100(0.007) + 8900c = 4.0
0.7 + 8900c = 4.0
8900c = 3.3
c = 0.00037

Rail:

100m + 600h + 3950r + 5670c = 5.8
100(0.007) + 600(0.0035) + 3950r + 5670(0.00037) = 5.8
0.7 + 2.1 + 3950r + 2.0979 = 5.8
4.8979 +3950r = 5.8
3950r = 0.9021
r = 0.00023

Part 3: Rank Modes of Transportation by Energy Intensity

Based on the calculations from the above step, students should be able to determine which mode of transportation is the most efficient per kilometer. In order to judge this, first students should rank energy intensity in terms of MJ per liter per kilometer, the unit of the calculated value in the previous step. The modes are ranked in order of most energy intensive to least.

1. Medium truck
2. Heavy Truck
3. Cargo ship
4. Rail

Rail is the most efficient mode of transportation per kilometer.

Part 4: Compare With Published Results

In addition to the three different transportation scenarios reproduced on this page, the report publishes an average of transportation energy costs based on compilations and analysis compiled by different government energy and transportation departments. These calculated transportation energy costs in MJ per t per km are used to calculate the estimates for transportation scenarios explored above.

Ask students to compare the results of their investigation in Part 2 and analysis in Part 3 to the summary reproduced in the table above. Are their results consistent with these figures? If the correlation isn't immediately obvious, ask students to rank the energy costs in the table above and then compare it to their ranking in Part 3. Other than air cargo, medium truck transportation is the most energy intensive, and rail transportation is the most efficient.

Part 5: Calculate a Bottled Water Journey

Look around your classroom or school for a packaged bottle of water. Most labels list the spring or municipal source from which the water was bottled. Ignoring the water treatment, plastic manufacturing, refrigeration, and other energy costs associated with bottled water, estimate this bottle's journey to your classroom and then calculate the energy intensity of the journey.

Because distances between places are key to the analysis, you may need a set of maps, atlases, or a digital mapping tool. Also, you can provide students with the following assumptions, which will help them plan the journey.

• Bottled water is almost never transported by air.
• Medium trucks are used for moving bottles within cities or metropolitan areas.
• Heavy trucks are used for moving bottles between cities or metropolitan areas and over long distances.
• Rail is used for long-distance inter-regional transport.

Answers for this scenario will vary depending on your geography and the bottle of water selected. However, students' work should resemble the following example.

Brand: Italian upscale sparkling water
Source: Val Brembana, Italy
Port of Export: Genoa, Italy
Port of Entry: Houston, Texas
Destination: Luckenbach, Texas

Distance from Source to Port of Export: 235 km by medium truck
Distance from Port of Export to Port of Import: 12,100 km by cargo ship
Distance from Port of Import to Destination: 458 km by heavy truck

235(0.007) + 12100(0.00037) + 458(0.0035) = 7.725 MJ/l

Italian upscale sparkling water in Luckenbach, Texas, requires about 7.725 megajoules per liter in transportation energy cost.

The introduction for this activity was reprinted in part from the Energy of Bottled Water section from Resourcefulness: An Introduction to the Energy-Water Nexus. This section provides a synopsis of the different energy inputs in the life-cycle of bottled water as abridged from P H Gleick and H S Cooley, “Energy implications of bottled water,” Environ. Res. Lett. 4 (2009).