The Water Footprint of Your Plastic Bottle

As consumer products go, plastic has become ubiquitous, and for good reason: it is an extremely useful material that has made life more convenient and in some cases, safer, but plastic has a huge environmental footprint with high costs to its creation. While the many activities that keep humans alive and advancing — agriculture, manufacturing, power production — require lots of water, plastic production is often, by design, one of the most unsustainable, including the huge amount of water required to produce it.

Water in the Plastic

Less understood is plastic’s substantial water footprint. Accounting for all the water involved in production underscores how plastic — especially the single-use plastic created for beverage bottles and the rest of the food packaging industry — encourages consumers to pour good water down the drain.

Each step in the life cycle of plastic, from the extraction of oil or natural gas at the well pad, through the many steps that result in the resins that become various types of plastic, consumes water. The water footprint accounts for the total volume of freshwater consumed in the entire production process.

Within this context, “water consumed” refers to the water permanently withdrawn from its source, or “water that is no longer available because it has evaporated, been transpired by plants, incorporated into products or crops, consumed by people or livestock, or otherwise removed from the immediate water environment.”

PET Plastic Production

Polyethylene terephthalate (PET or PETE) plastic – the source material of water bottles, soda bottles and more — makes up 10.2 percent of global plastic production. Because PET is a petroleum product, its water footprint includes the water consumed in the processes of extracting, refining and manufacturing of oil and natural gas, which produces the raw material that becomes PET resin pellets. The final step includes molding these pellets into plastic packaging.

To calculate the total water footprint of PET plastic, both the “blue” and “grey” footprints have to be assessed, which means taking into account not just the water consumed during creation of the raw material, but also the water required to reduce the thermal pollution from cooling water heated during processing.

In a 2011 study, researchers affiliated with the Water Footprint Network estimated the blue and grey water footprints of PET by analyzing the steps by which raw material becomes PET plastic resin. The estimated blue water footprint of the “oil to PET” steps was 2.64 gallons of water per pound (10 liters per kilogram). Adding the grey water footprint caused the water footprint to jump to 28 gallons per pound (235 liters per kilogram). Based on these numbers, it takes about 1.4 gallons (5.3 liters) of water to produce a typical single-use water or soda bottle.

According to the plastic waste study referenced above, from 2002 to 2014 approximately 3.83 billion MT of PET plastic resin was produced worldwide — this is equivalent to 29,000,000,000,000,000 plastic water bottles. The blue and grey water footprint for all that PET works out to about 91.8 billion m3 (which is like filling 693 billion bathtubs full of water).

Think Globally, Drink Locally

A paper by Vorosmarty et al., published in the journal Science explains that, while water impacts are most sharply felt and managed at a local level, in an era of international supply chains, local water problems may be impacted by global systems and processes. Because so much water use and pollution occurs from trade that moves water “virtually” around regions, countries and continents, local water mismanagement can lead to clashes over water resources. In India, for instance, soft drink giants PepsiCo and Coca-Cola have bottling operations with a long history of using and polluting residents’ scarce water supplies. While the companies slurp up loads of water during the soft drink-making process, the finished beverages are sent outside the community and around the region. This becomes even more contentious during times of drought for these already water-scarce areas of India.

Vorosmarty goes on to say that global trade can “[outsource] environmental problems to countries with lax regulation[s] that host highly polluting manufacturing or agriculture.” Not only can environmental problems be outsourced from one country to another, but also from one region to another within a country, particularly to places that are more open to resource exploitation or that have accommodating regulatory conditions.

In the case of plastic production, if it occurs within a stressed watershed, and if water management within that watershed is suboptimal, then consumers who reach for those plastic products are unwittingly contributing to unsustainable water use. This does not mean the problems can be ignored.

Although the issues might be hidden from consumers’ view because they are a town or continent away, the risk remains for producers, their supply chains and all those who rely on impacted watersheds. Governments, companies and consumers alike must take the water issues that come with upstream plastic production as seriously as they take the plastic pollution floating into their rivers and seas.