Agreement is hard to find when comparing the environmental effects of paper and plastic bags. To a varying extent, both are heavy users of natural resources in the manufacturing and recycling processes, both cause pollution and both produce landfill. It is a matter of degree which is the least harmful.
Ultimately, it comes down to energy use and the production of waste, both of which involve complex global calculations.
Here are some websites that comprehensively discuss the pros and cons of both.
http://blog.greenfeet.com/index.php/paper-vs-plastic-the-shopping-bag-debate/reducing-your-footprint/121
http://www.foe.co.uk/resource/briefings/consequence_pulp_paper.html:
http://www.angelfire.com/wi/PaperVsPlastic:
http://www.enviroliteracy.org/article.php/1268.html
http://blog.greenfeet.com/index.php/paper-vs-plastic-the-shopping-bag-debate/reducing-your-footprint/121
What follows is some of their key points:
Plastics take up less landfill than paper bags. According to one estimate, plastics comprise 18% of waste by volume and 7% by weight. If plastic was replaced by other materials, “rubbish weight would increase by 150%, packaging would weigh 300% more and energy consumed by the industry would increase by 100%”. Comparatively, plastic bags require less energy to produce.
Paper is easily and regularly recycled. It is biodegradable, rather than photodegradable, and can be used in compost, for instance. Stray plastic bags litter the planet’s land and waters. Estimates vary on how long it takes for plastic to fully break down, with figures ranging from 400 to 1000 years. In the absence of empirical evidence, it seems any plastic ever manufactured still exists either in its original or reconstituted form. In other words, it never completely returns to the earth.
So-called biodegradable plastic is in fact typically made from wood fibres mixed with plastic, meaning only the organic material degrades. It is argued that this leaves millions of tiny plastic fragments to mix in with the soil, enter the food chain and end up on our plates, with unpredictable effects on human health.
Although plastics do not biodegrade, modern landfills are designed in such a way that nothing biodegrades, because the waste is isolated from air and water in order to prevent groundwater contamination and air pollution.
In both cases, the manufacturing process creates pollution and waste products. The inks and additives found in plastic can create dioxins when burned and create toxic substances that need to be disposed of in special waste dumps. Paper manufacture requires vast amounts of wood chips and water. Depending on the process employed, chemicals used can include sodium hydroxide and calcium carbonate.
Manufacturers of both kinds of bags take steps to reuse waste materials and reduce pollution. For instance, some materials produced from plastics manufacture are used as fuel for energy; the paper industry says more and more manufacturers now use water-based inks
The machinery needed for felling trees and removing logs is a heavy user of fossil fuels. Also the creation of roads and destruction of habitat has a deleterious effect on wildlife. The fuel used in the transport of timber is a cause of emissions. It is estimated that it would take seven trucks to transport the same number of paper bags as can be moved by a single truck full of plastic bags.
Recycling, too, can make heavy demands on energy and water, and in the case of paper, particularly, may rely on the use of chemicals
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