Once the trees are collected, they must dry at least three years before they can be used. More machinery is used to strip the bark, which is then chipped into one-inch squares and cooked under tremendous heat and pressure. This wood stew is then "digested," with a chemical mixture of limestone and acid, and after several hours of cooking, what was once wood becomes pulp. It takes approximately three tons of wood chips to make one ton of pulp.
The pulp is then washed and bleached; both stages require thousands of gallons of clean water. Coloring is added to more water, and is then combined in a ratio of 1 part pulp to 400 parts water, to make paper. The pulp/water mixture is dumped into a web of bronze wires, and the water showers through, leaving the pulp, which, in turn, is rolled into paper.
Whew! And that's just to make the paper; don't forget about the energy inputs -- chemical, electrical, and fossil fuel-based -- used to transport the raw material, turn the paper into a bag and then transport the finished paper bag all over the world.
WHERE DO PAPER SHOPPING BAGS GO WHEN YOU'RE DONE WITH THEM?
When you're done using paper shopping bags, for shopping or other household reuses, a couple of things can happen. If minimally-inked (or printed with soy or other veggie-based inks) they can be composted; otherwise, they can be recycled in most mixed-paper recycling schemes, or they can be thrown away (which is not something we recommend).
If you compost them, the bags break down and go from paper to a rich soil nutrient over a period of a couple of months; if you throw them away, they'll eventually break down of the period of many, many years (and without the handy benefits that compost can provide). If you choose the recycle paper bags, then things get a little tricky.
The paper must first be re-pulped, which usually requires a chemical process involving compounds like hydrogen peroxide, sodium silicate and sodium hydroxide, which bleach and separate the pulp fibers. The fibers are then cleaned and screened to be sure they're free of anything that would contaminate the paper-making process, and are then washed to remove any leftover ink before being pressed and rolled into paper, as before.
HOW ARE PLASTIC BAGS MADE?
Unlike paper bags, plastic bags are typically made from oil, a non-renewable resource. Plastics are a by-product of the oil-refining process, accounting for about four percent of oil production around the globe. The biggest energy input is from the plastic bag creation process is electricity, which, in this country, comes from coal-burning power plants at least half of the time; the process requires enough juice to heat the oil up to 750 degrees Fahrenheit, where it can be separated into its various components and molded into polymers. Plastic bags most often come from one of the five types of polymers -- polyethylene -- in its low-density form (LDPE), which is also known as #4 plastic.
HOW DOES PLASTIC BAG RECYCLING WORK?
Like paper, plastic can be recycled, but it isn't simple or easy. Recycling involves essentially re-melting the bags and re-casting the plastic, though, according to the U.S. EPA, manufacturing new plastic from recycled plastic requires two-thirds of the energy used in virgin plastic manufacturing. But, as any chef who has ever tried to re-heat a Hollondaise sauce will tell you, the quality isn't quite as good the second time around; the polymer chains often break, leading to a lower-quality product.
What does that mean to you? Basically, plastic is often downcycled -- that is, the material loses viability and/or value in the process of recycling -- into less functional forms, making it hard to make new plastic bags out of old plastic bags.
WHAT ABOUT BIODEGRADABLE PLASTIC BAGS?
Biodegradable plastic is a mixed bag (pun intended) as well; while biopolymers like polyhydroxyalkanoate (PHA) and Polylactide (PLA) are completely biodegradable in compost (and very, very, very slowly -- if at all -- in a landfill) and are not made from petroleum products, they are often derived from our food sources.
The primary feedstock for bioplastics today is corn, which is rife with agro-political conflict and often grown and harvested unsustainably; because of these reasons, and because it competes with food supply, it is not likely to be a long-term solution in the plastics world.
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