Materials Management

A comparison of bottled and tap water using life cycle analysis

State law establishes a hierarchy of preferred methods for managing wastes. Recycling is preferable to disposal, but waste prevention (the “reduce, reuse” part of “reduce, reuse, recycle”) is even more preferred. While Oregon has made excellent strides at increasing recycling, progress at prevention has been more elusive.

 

Drinking water provides an opportunity to examine the “reduce, reuse, recycle” hierarchy in more detail. Drinking from the tap reduces waste in the first place. 5-gallon containers from water delivery services are typically reused. Single-use bottles can be recycled or disposed of.

 

DEQ has completed a study that compares a wide range of environmental impacts (including greenhouse gas emissions) of drinking water from the tap, 5-gallon reusables, and single-use bottles. It compares the environmental impacts of tap water (“reduce”) against the impacts of bottled water (“recycle” and “dispose”). The study confirms that while recycling bottles is environmentally preferable to disposing of them, buying bottled water and recycling the bottles is not the best environmental choice. Drinking water from the tap (waste prevention) typically has substantially lower impacts in most categories of environmental impact.

 

Other highlights of the study include the following: 

  • For water that is bottled and consumed within Oregon, the large majority of environmental impacts are typically from producing the plastic resin used to make the bottle.
  • If the bottle comes from across the country or the world, most impacts increase by a factor of 3 or more.
  • End-of-life (disposal) related impacts are very small, with the possible exception of biodegradable plastic bottles. If they decompose in a landfill, the resulting methane is a potent greenhouse gas. Even when landfills capture some of the gas to produce energy, the remaining gas escapes and contributes to climate change.
  • If you choose to drink bottled water, recycling the bottle can have moderate environmental benefits. These benefits, however, are still overshadowed by the negative impacts of making and transporting the bottle in the first place.
  • For tap water, the frequency of washing your container in a dishwasher influences the results more than any other factor.

Reports

 

Frequently asked questions

​The study not only tells us that how you obtain your drinking water makes a difference, it also helps illustrate the importance of following the “waste management hierarchy” of “reduce, then reuse, then recycle.”

The study shows that reducing your use of disposable packaging, and drinking tap water in a reusable cup or bottle instead, typically has significantly lower environmental impacts than buying water in disposable packaging and recycling it. While recycling is preferable to disposal, waste prevention is greatly preferable to recycling.

This conclusion helps us better understand the value of following the “waste management hierarchy.” In this case, it is better environmentally to take the “reduce and reuse” option over the “recycle” option.

​Using a “shared allocation” approach (where the benefits of recycling or using recycled material are shared between the system providing the recycled wastes and the system using them in new products), purchasing and recycling a “typical” water bottle reduces energy consumption by 24% and greenhouse gas emissions by 16% over the entire life cycle, compared against purchasing and disposing of the same water bottle. In contrast, consuming the same quantity of water from the tap in a “typical” reusable bottle, even if washed frequently in a highly inefficient dishwasher, reduces energy consumption by 85% and greenhouse gas emissions by 79%.

Comparing most other attributes (acidification, ecotoxicity, eutrophication, smog, ozone, cancer and non-cancer illnesses), the benefit of recycling relative to disposal is so small that it cannot be considered significant. In contrast, drinking tap water in the “typical” reusable bottle reduces these impacts anywhere from 72 to 96%, even if the reusable bottle is washed frequently in a highly inefficient dishwasher.

​Yes. Drinking tap water from a reusable cup or bottle generally has lower environmental impacts than bottled water options that exist in Oregon today. When existing bottled water options in Oregon are compared to tap water options, the energy requirements and greenhouse gas emissions for tap water are lower in all cases. Similar results are found for all other categories of environmental impacts included in this study: acidification potential, carcinogenic potential, ecotoxicity potential, eutrophication potential, non-carcinogenic potential, ozone depletion potential, respiratory effects potential, and smog formation potential.

Drinking tap water from a cup or reusable bottle eliminates the impacts of extracting and producing the materials needed to make water bottles. This benefit is significant. Even the best performing bottled water scenario, which uses a light-weighted bottle not even available in Oregon yet, has global warming impacts 46 times greater than the best performing tap water scenario.

​This study clearly shows that a reusable container made of steel, aluminum, plastic, or glass has significant benefits over the single-serve water bottles made of PET (polyethylene terephthlatate), even if the reusable containers are eventually disposed of and the single-serve bottles are recycled. When comparing the existing single-serve water bottle options in Oregon to tap water with a reusable container, all tap water options studied have less impact than all bottled water options currently available.
​It is possible, yes. Study results indicate that for bottled water to be better, it would require comparing extremely poor tap water options (such as drinking out of a glass and washing it in a highly inefficient, less-than-full dishwasher after each and every use) and extremely low-impact single-use bottles that are not currently available in Oregon.
​If you choose to drink bottled water, recycling the bottle after use is better than tossing it in the garbage. Recycling water bottles reduces the amount of virgin resources needed to produce new water bottles. Conserving resources helps protect human and ecological health by reducing the pollution related to the extraction and processing of resources into water bottles. But while recycling offers some moderate benefits, the benefits of prevention (not using the bottle at all) are many times greater.
​Yes, but it is important to understand that there are several different types of compostable plastic bottles, each with different environmental impacts. For example, some are made from traditional polyethylene with small amounts of “oxodegradable” additives that cause the polyethylene to degrade into tiny fragments when exposed to certain environmental conditions. A different approach is plastic derived from corn as the primary feedstock, such as polylactic acid (PLA) produced by Natureworks under the brand name Ingeo. Both may be compostable (under certain conditions), but their environmental impacts differ. It should be noted that at the time DEQ’s report was published, water was not being sold in Oregon in compostable bottles.
​The answer depends on what type of compostable bottle you’re asking about.

Oxodegradable plastic bottles were not specifically evaluated in DEQ’s report. They are typically comprised primarily of PET, so the impacts of producing and transporting the bottles are very similar to the PET bottles profiled in DEQ’s study. The major difference occurs at end-of-life. If recycled, the oxodegradable plastics will blend with traditional plastics, potentially causing new products made from these recycled plastics to fail.

In the landfill, the oxodegradable plastics may eventually decompose, producing carbon dioxide and methane in the process. While some of the methane will be captured and used to produce energy, the remainder will escape to the atmosphere. Because methane is such a potent greenhouse gas, the oxodegradable PET bottles will likely have higher greenhouse gas impacts than traditional PET bottles if they degrade in the landfill.

PLA is difficult to evaluate, in part because it is a relatively new resin. Most PLA used in the United States is produced at a single plant in Blair, Nebraska. The manufacturer claims to have made significant process improvements in mid-2009 that significantly reduce the environmental impacts of production. Data reflecting these improvements were not available at the time DEQ was completing its study, so the PLA water bottles included in its study uses production characteristics from 2005. As such, these results may overstate some impacts over the life cycle of PLA bottles.

Comparing a PLA bottle composted 100% of the time against a PET bottle recycled 100% of the time, the PLA bottle consumes slightly less energy over its life cycle, and contributes slightly more to greenhouse gas emissions. The ecotoxicity impact of the PLA bottle is about half that of the PET bottle, and smog impacts are about 20% lower, but respiratory potential impacts are 50% higher and eutrophication potential is about 4 times higher than the PET bottle.

If the PLA compostable bottle is not composted or recycled (since there is no current recycling system established for PLA in Oregon) then the bottle will likely be disposed in the landfill. Once landfilled, the bottle could potentially decompose. Since not much is known about PLA’s decomposition in landfills, DEQ modeled both 100% and 0% decomposition rates. If the PLA bottle decomposes in the landfill, it contributes to the production of landfill methane, a potent greenhouse gas. In the 100% decomposition scenario, the PLA bottle’s life cycle global warming impact is approximately 60% greater than the typical PET bottle (recycled at a rate of 62%, an estimate of the current recycling rate for PET bottles under Oregon’s bottle bill). If the bottle doesn’t decompose, it has the potential to reduce global warming impacts by 23% compared to the average PET bottle.

​Yes. The long-distance transport of bottled water has significant impacts compared to water that is bottled and consumed locally. For the long-distance transport scenarios, the study examined plastic bottled water coming from Maine by truck and Fiji by boat then truck. DEQ also looked at glass bottled water coming from France by boat then truck. The global warming impacts of the bottled water coming from Maine or Fiji are 3 to 5 times greater than the typical bottled water sourced within 50 miles of its final destination here in Oregon. The glass water bottles from France were about 10 times more impactful than the typical bottled water sourced within 50 miles of its final destination – partly because of transportation, but also because the heavy glass bottle and heavy plastic closure have higher impacts in manufacturing when compared to relatively lightweight plastic bottles.
​Yes, bottle size matters. Since the study quantifies the environmental impacts of delivering 1,000 gallons of drinking water to the consumer, the size of the bottle will directly influence how many bottles are needed to deliver that water. The smaller the bottle, the more bottles are needed to deliver the water. In this study DEQ evaluated 8 fluid ounce and 33.8 fluid ounce (1 liter) bottles compared to the typical 16.9 fluid ounce bottle. Results indicate that the smaller bottle (8 fl. oz.) had approximately double the environmental impacts of the typical bottle. Since the 8 fluid ounce bottle uses about the same amount of plastic for half as much water, many of the impacts are doubled. The 33.8 fluid ounce bottle was slightly more impactful than the 16.9 fluid ounce bottle. Although the bottles held twice as much water, they used more than twice as much plastic, which caused their impact to be slightly higher than the typical 16.9 fluid ounce bottles. The findings here indicate that both bottle size and bottle weight-to-volume ratios are important.
​Yes, when compared to heavier single-serve bottles. Light-weighting a bottle helps reduce the amount of material needed to produce the bottle and thereby reduces all of the impacts associated with extracting and producing that material. The “typical” water bottle in this study weighed 13.3 grams. Reducing the weight to 9.8 grams reduced the global warming impacts of the bottle by about 18%. It should be noted that 9.8 gram bottles were not available in Oregon at the time of this study.
​Comparing the ranges of results for HOD water delivery against the ranges of results for single-serving bottles (bottled in Oregon), there are many sub-scenarios where the two systems have impacts that overlap, so no general statements can be made about which of these systems has lower environmental impacts. The impacts, however, are distributed differently. The majority of the impacts of the HOD system were split between delivery of the water, washing the reusable cups, and washing the bottles to prepare them for reuse. In contrast, the majority of the global warming impacts for the single-serve bottles were incurred during the production of the bottles.

In the case of single-serve bottles containing water shipped from out-of-state, HOD has lower impacts.

​Yes. In this study, washing reusable cups or bottles comprised the large majority of global warming and most other environmental impacts for all of the tap water scenarios. The global warming impacts are directly proportional to how often you wash the cup. For example, if you use your cup two times before washing it, the impacts will be about half as much as using the cup once and then washing it. To reduce these impacts, consumers should consider reusing cups or bottles multiple times before washing them, using an energy and water conserving dishwasher, and only running the dishwasher when it is full.
​This study did not evaluate washing reusable cups or bottles by hand. These impacts can be highly variable, and may be more or less impactful than using a dishwasher.
​No. The factors that contribute most to the varying global warming impacts among bottle water option are the transport distances from bottler to retail, consumer driving behavior, mass and volume of the bottle, type of material (plastic or glass), and the rate at which the bottle is recycled. In one scenario, DEQ evaluated a consumer driving to the store only to buy water. In this case, the impacts of the consumer’s trip were very significant.

In summary, if someone chooses to consume bottled water, the conclusions from this study support water that is bottled and distributed locally, using light-weighted (ultra-thin) plastic bottles that are larger than the small 8 oz. bottles available. Additionally, the consumer should avoid making a special trip to buy water. Finally, it’s important to recycle the bottle after using it. But again, the best environmental choice is to avoid the single-serve bottle altogether, and drink water from the tap.