Too bad that PLA only degrades when composted, not in landfills.

Not true. PLA materials break down faster (in as little as 90 days under perfect condidtions) but will still break back down even in a landfill. It just takes alot longer. One of the problems with any materials in landfills has been oxygen levels. Even hot dogs and news papers don't break down if buried deep enough and starved of oxygen. Bacteria and microbes need the O2 to break things down, that's just how it works.

Given the choice between a polystyrene plastic and PLA plastic the PLA wins. Styrofoam (which is EPS expanded polystyrene) will be around for over 300 years. You cannot say that a...

Too bad that PLA only degrades when composted, not in landfills.

Not true. PLA materials break down faster (in as little as 90 days under perfect condidtions) but will still break back down even in a landfill. It just takes alot longer. One of the problems with any materials in landfills has been oxygen levels. Even hot dogs and news papers don't break down if buried deep enough and starved of oxygen. Bacteria and microbes need the O2 to break things down, that's just how it works.

Given the choice between a polystyrene plastic and PLA plastic the PLA wins. Styrofoam (which is EPS expanded polystyrene) will be around for over 300 years. You cannot say that about PLA or any of the other biograde materials bing made right now.

I got my info about PLA from this article in the Smithsonian, Napster. I'm not trying to be difficult, just pointing out that PLA isn't as biodegradable as a lot of people would like to believe. It needs special composting conditions; it doesn't breakdown in the average home compost bin. From the Smithsonian article:

According to a biodegradability standard that Mojo [executive director of the Biodegradable
Products Institute] helped develop, PLA is said to decompose into carbon dioxide and water in a “controlled composting environment” in fewer than 90 days. What’s a controlled composting environment? Not...

I got my info about PLA from this article in the Smithsonian, Napster. I'm not trying to be difficult, just pointing out that PLA isn't as biodegradable as a lot of people would like to believe. It needs special composting conditions; it doesn't breakdown in the average home compost bin. From the Smithsonian article:

According to a biodegradability standard that Mojo [executive director of the Biodegradable
Products Institute] helped develop, PLA is said to decompose into carbon dioxide and water in a “controlled composting environment” in fewer than 90 days. What’s a controlled composting environment? Not your backyard bin, pit or tumbling barrel. It’s a large facility where compost—essentially, plant scraps being digested by microbes into fertilizer—reaches 140 degrees for ten consecutive days. So, yes, as PLA advocates say, corn plastic is “biodegradable.” But in reality very few consumers have access to the sort of composting facilities that can make that happen. NatureWorks has identified 113 such facilities nationwide—some handle industrial food-processing waste or yard trimmings, others are college or prison operations—but only about a quarter of them accept residential foodscraps collected by municipalities.

Wal-Mart’s Kistler says the company isn’t about to take back used PLA for composting. “We’re not in the business of collecting garbage,” he says. “How do we get states and municipalities to set up composting systems? That is the million-dollar question. It’s not our role to tell government what to do. There is money to be made in the recycling business. As we develop packaging that can be recycled and composted, the industry will be developed.”

(my note here: Wal-Mart isn't "in the business of collecting garbage", but they are in the business of selling it!)

For their part, recycling facilities have problems with PLA too. They worry that consumers will simply dump PLA in with their PET. To plastic processors, PLA in tiny amounts is merely a nuisance. But in large amounts it can be an expensive hassle. In the recycling business, soda bottles, milk jugs and the like are collected and baled by materials recovery facilities, or MRFs (pronounced “murfs”). The MRFs sell the material to processors, which break down the plastic into pellets or flakes, which are, in turn, made into new products, such as carpeting, fiberfill, or containers for detergent or motor oil. Because PLA and PET mix about as well as oil and water, recyclers consider PLA a c...

For their part, recycling facilities have problems with PLA too. They worry that consumers will simply dump PLA in with their PET. To plastic processors, PLA in tiny amounts is merely a nuisance. But in large amounts it can be an expensive hassle. In the recycling business, soda bottles, milk jugs and the like are collected and baled by materials recovery facilities, or MRFs (pronounced “murfs”). The MRFs sell the material to processors, which break down the plastic into pellets or flakes, which are, in turn, made into new products, such as carpeting, fiberfill, or containers for detergent or motor oil. Because PLA and PET mix about as well as oil and water, recyclers consider PLA a contaminant. They have to pay to sort it out and pay again to dispose of it.

NatureWorks has given this problem some thought. “If the MRF separates the PLA, we’ll buy it back from them when they’ve got enough to fill a truck,” says spokeswoman Bridget Charon. The company will then either take the PLA to an industrial composter or haul it back to Blair, where the polymer will be broken down and remade into fresh PLA.

Despite PLA’s potential as an environmentally friendly material, it seems clear that a great deal of corn packaging, probably the majority of it, will end up in landfills. And there’s no evidence it will break down there any faster or more thoroughly than PET or any other form of plastic. Glenn Johnston, manager of global regulatory affairs for NatureWorks, says that a PLA container dumped in a landfill will last “as long as a PET bottle.” No one knows for sure how long that is, but estimates range from 100 to 1,000 years.

Gingembre-


Also from that Smithsonian article you referenced:

Eric Lombardi, president of the Grassroots Recycling Network and a leader in the international Zero Waste movement, takes a nuanced view of PLA’s progress. He says it’s “visionary” even to think about biologically based plastic instead of a petroleum-based one. True, he says, there are problems with PLA, “but let’s not kill the good in pursuit of the perfect.” He suggests that the difficulty disposing of PLA reflects a larger deficiency in how we handle trash. He’s calling for a composting revolution. “We need a convenient, creative c...

Gingembre-


Also from that Smithsonian article you referenced:

Eric Lombardi, president of the Grassroots Recycling Network and a leader in the international Zero Waste movement, takes a nuanced view of PLA’s progress. He says it’s “visionary” even to think about biologically based plastic instead of a petroleum-based one. True, he says, there are problems with PLA, “but let’s not kill the good in pursuit of the perfect.” He suggests that the difficulty disposing of PLA reflects a larger deficiency in how we handle trash. He’s calling for a composting revolution. “We need a convenient, creative collection system with three bins: one for biodegradables, which we’ll compost, one for recycling, and one for whatever’s left.”

Until such a system is in place, it’s going to be hard to have cheap convenience packaging and feel good about its environmental effect—to have our takeout cake and eat it too. But the manufacture of PLA does save oil and generates far less air pollution. And we have to start somewhere.