The environmental impact of all types of carrier bag is dominated by resource use and production stages. Transport, secondary packaging and end-of-life management generally have a minimal influence on their performance. (Exec. Summary)

“Recycling or composting generally produce only a small reduction in global warming potential and abiotic depletion.”

(Exec summary)

40.3% of plastic bags are reused as bin liners.

(Study at p. 30)

“Reuse as bin liners produces greater benefits than recycling bags.”

(Exec summary)

“When each bag was compared with no primary reuse (i.e. no reuse as a carrier bag), the conventional HDPE bag had the lowest environmental impacts of in eight of the nine impact categories, because it was the lightest bag considered.” The study did not consider litter impacts. (Study at 56.)

[A] paper bag has a more adverse impact than a plastic bag for most of the environmental issues considered. Areas where paper bags score particularly badly include water consumption, atmospheric acidification (which can have effects on human health, sensitive ecosystems, forest decline and acidification of lakes) and eutrophication* of water bodies (which can lead to growth of algae and depletion of oxygen).

Paper bags are anywhere between six to ten times heavier than lightweight plastic carrier bags and, as such, require more transport and its associated costs. They would also take up more room in a landfill if they were not recycled.

The Scottish Report contains the comparison in the table below (at page 23). The lightweight plastic bag was given a score of 1 in all categories as a reference point. A score greater than 1 indicates that another bag makes more contribution to the environmental problem than a lightweight plastic bag when normalised against the volume of shopping carried. The indicators take account of emissions which occur over the whole lifecycle.

The report took into account that a paper bag holds more than a plastic bag and applied an adjustment factor.

The Boustead report was commissioned by Progressive Bag Affiliates, a plastic bag industry organization. It was peer reviewed by an independent third party, a Professor of Chemical Engineering at North Carolina State University. He is an expert on life cycle analysis with extensive experience in the field. He commented that the Boustead report “provides both a sound technical descriptions (sic) of the grocery bag products and the processes of life cycle use…. Whatever the goals of the policy makers, these need to be far more explicit that general environmental improvement, since the life cycle story is consistent in favor of recyclable plastic bags.”

The professor reviewed every single one of the figures in the report and disagreed with some of them. The Boustead report was amended to the extent that the Boustead author agreed with the professor’s comments. For example, the figure “103” for electricity in Table 9B was corrected to “154.” 

Use-Less-Stuff.com (“ULS”) has issued a report comparing plastic and paper grocery bags. ULS made the following findings (at pages 3-4):

1. Plastic bags generate 39% less greenhouse gas emissions than uncomposted paper bags, and 68% less greenhouse gas emissions than composted paper bags. The plastic bags generate 4,645 tons of CO2 equivalents per 150 million bags; while uncomposted paper bags generate 7,621 tons, and composted paper bags generate 14,558 tons, per 100 million bags produced.
   
   
2. Plastic bags consume less than 6% of the water needed to make paper bags. It takes 1004 gallons of water to produce 1000 paper bags and 58 gallons of water to produce 1500 plastic bags.
   
   
3. Plastic grocery bags consume 71% less energy during production than paper bags. Significantly, even though traditional disposable plastic bags are produced from fossil fuels, the total non-renewable energy consumed during their lifecycle is up to 36% less than the non-renewable energy consumed during the lifecycle of paper bags and up to 64% less than that consumed by biodegradable plastic bags.
   
   
4. Using paper sacks generates almost five times more solid waste than using plastic bags.
   
   
5. After four or more uses, reusable plastic bags are superior to all types of disposable bags -- paper, polyethylene and compostable plastic -- across all significant environmental indicators.

The ULS report concludes as follows (at page 5):

Legislation designed to reduce environmental impacts and litter by outlawing grocery bags based on the material from which they are produced will not deliver the intended results. While some litter reduction might take place, it would be outweighed by the disadvantages that would subsequently occur (increased solid waste and greenhouse gas emissions). Ironically, reducing the use of traditional plastic bags would not even reduce the reliance on fossil fuels, as paper and biodegradable plastic bags consume at least as much non-renewable energy during their full lifecycle.

The Environmental Paper Network (EPN) has published a comprehensive report entitled: “The State of the Paper Industry.”  The EPN states in the report as follows:

[T]he paper industry’s activities – and our individual use and disposal of paper in our daily lives—have enormous impacts. These include loss and degradation of forests that moderate climate change, destruction of habitat for countless plant and animal species, pollution of air and water with toxic chemicals such as mercury and dioxin, and production of methane—a potent greenhouse gas—as paper decomposes in landfills, to name just a few. (Page iv)

One of the most significant, and perhaps least understood, impacts of the paper industry is climate change. Every phase of paper’s lifecycle contributes to global warming, from harvesting trees to production of pulp and paper to eventual disposal. (Page v)

The climate change effects of paper carry all the way through to disposal. If paper is landfilled rather than recycled, it decomposes and produces methane, a greenhouse gas with 23 times the heat-trapping power of carbon dioxide. More than one-third of municipal solid waste is paper, and municipal landfills account for 34 percent of human related methane emissions to the atmosphere, making landfills the single largest source of such emissions. The U.S. Environmental Protection Agency has identified the decomposition of paper as among the most significant sources of landfill methane. (Page v)

According to the report at page 3:

• Plastics contribute 4% of toxic emissions
• Paper contributes 12% of toxic emissions

According to the report at page 5, discards in the U.S. Municipal solid waste streams by material are as follows:

• Plastics 16%
• Paper and paperboard 25%

The Daily Green has summarized the EPN report. Some of its observations are as follows:

1. Forests store 50% of the world's terrestrial carbon. (In other words, they are awfully important "carbon sinks" that hold onto pollution that would otherwise lead to global warming.)
   
   
2. Half the world's forests have already been cleared or burned, and 80% of what's left has been seriously degraded.
   
   
3. 42% of the industrial wood harvest is used to make paper.
   
   
4. The paper industry is the 4th largest contributor to greenhouse gas emissions among United States manufacturing industries, and contributes 9% of the manufacturing sector's carbon emissions.
   
   
5. If the United States cut office paper use by just 10% it would prevent the emission of 1.6 million tons of greenhouse gases -- the equivalent of taking 280,000 cars off the road.
   
   
6. Paper accounts for 25% of landfill waste (and one third of municipal landfill waste).
   
   
7. Municipal landfills account for one third of human-related methane emissions (and methane is 23-times more potent a greenhouse gas than is carbon dioxide).

Friends of the Earth has published a report entitled “Forests And Climate Change.” This is the most balanced report we could find on the paper industry and deforestation. We believe that it does not overstate or understate the impact of logging. The report contains the following findings:

• Deforestation in the tropics is the second most important source of greenhouse gas emissions.
  
  
• Fossil fuel consumption is the greatest source of greenhouse gas emission.

• The forest industry's claims that they are “combating climate change” are over-stated and provide no justification for the intensive forest management practices and timber/paper production of the industry, or the continued wasteful consumption of wood and paper products.

The report says that changes in ocean chemistry, caused by ocean acidification, means that we can predict that some creatures in the Antarctic Ocean will be among the first to be affected. For example, some types of plankton a major source of food for fish and other animals   may be unable to make their calcium carbonate shells by 2100. This may have significant consequences for entire food webs in the region, although the overall impact of this is unclear.

Higher concentrations of carbon dioxide may also make it harder for some larger marine animals to obtain oxygen from seawater. For example, squid are particularly sensitive because they move by jet propulsion   this is very energy-demanding and requires a good supply of oxygen.

The London Times reported as follows on the Royal Society’s findings:

[Dr. Hall-Spencer of the University of Plymouth, who led the Royal Society study, stated:] "Our observations verify concerns, based on laboratory experiments and model predictions, that marine food webs will be severely disrupted and major ecological tipping-points are likely if human CO2 emissions continue unabated."

This appraisal of life in a more acidic ocean was if anything conservative, Dr Hall-Spencer said, because it mimicked future ecosystems only partially.

The acidity around carbon dioxide vents can be reduced by rough conditions, which dilute the water - something that would not happen if the whole ocean was highly acidic.

The researchers also noted that while fish continued to swim through more acidic waters, they avoided breeding or spawning in them. “That isn't a problem at the moment, as they can go elsewhere,” Dr Hall-Spencer said. “But in a more acidic ocean there will be no escape.”

Global warming will also have an independent impact on sea life, by raising ocean temperatures.

When considering whether to ban plastic bags in favor of paper bags, the impact of greater CO2 emissions on the oceans must not be disregarded.

Click here for a BBC article about the huge destruction of coral reefs caused by global warming, and the devastating effect on marine ecosystems.