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March 24, 2008


B. Sanders

I'm all for shifting to renewable resources as I'm sure most readers to this are. However, I heard somewhere that PLA, albeit made from renewable resources, breaks down into methane eventually. Methane is 23 times worse than carbon dioxide from a global warming perpective.... If this is true, why isn't that being discussed in the big picture? Thus, is the cure, worse than the disease? Or, in this case would it be better if it didn't break down at all to thereby permanently sequester the carbon?

Chris Smith

In response to the post by B Sanders, NatureWorks PLA will, if composted in the absence of oxygen, decompose to methane and that is more than 20 times more harmful than carbon dioxide. The critical question with regard to PLA packaging, however, is how much will be composted at all?
PLA will only compost in commercial composting units. If the consumer cannot put it into such a unit it's no better than landfilling.
One other point to take into account. NatureWorks PLA is made from "renewable" corn but a whole lot of energy is used to sow, water, harvest, extract, ferment and polymerise the material.
On a straight energy balance, PLA is probably better than traditional polyethylene in a single use disposable application - but not by much. Natureworks buys renewable energy and uses this to offset its carbon dioxide emissions but some would say we should be looking to reduce ALL energy consumption.
Of course, if you use a traditional plastic and recycle it, then use it again the energy balance quickly moves in favour of petrochemicals.
Finally, this argument may all become a little hypothetical as companies such as DuPont, Dow and Braskem are all developing traditional plastics made from corn or sugar cane - that's probably the future.

John Murray

There are two basic post consumer resins in specific applications that today are recycled. PET bottles (soda, water) and HDPE bottles (milk, laundry detergent) are the most commonly collected plastic materials in recycling programs. Less than 21 percent of PET bottles, or roughly 1.6 million pounds of plastic PET bottles produced in the United States were recycled in 2002. That means nearly 80 percent of plastic bottles are lanfilled, incinerated, etc rather than recycled. Please note that not all containers that are labeled as #1 and #2 are recycled - only very specific applications (bottles) are recycled today. The remainder, even when sorted by the consumers for curb side pickup typically end up in a landfill - and these plastic have been around for decades yet have failed to create a consistent recovery component of any magnitude for their plastic.

While the HDPE recovery rate is up slightly from 23.2 percent in 2001 to 24.2 percent in 2002, PET bottle recycling showed a more than 2 percent decline to 19.8 percent during this period. These vastly different results for the major bottle resins are linked to how consumers use each type of packaging. PET bottles saw a decrease in recycled pounds primarily due to the difficulty in capturing single-serve bottles consumed away from home. Conversely, HDPE bottles, used for packaging milk, household cleaners shampoo, etc. are typically used at home, close to a recycling bin, which makes them easier to recover.

Trials by leading NIR (Near Infrared) machine sorting system manufacturers show that NatureWorks biopolymer can be separated from the post-consumer RPET (recycled Polyethylene Terapthalate) stream, and can be separated into its own stream when post-consumer amounts warrant. Based on this in August 2005 NatureWorks LLC introduced a bottle "buy back" program for PLA bottles. NatureWorks LLC continues to work with recycling stakeholders to ensure the successful integration of PLA into the recycling stream. In addition to its ability to be mechanically recycled and composted, NatureWorks® biopolymer has shown favorable properties for use where incineration is the preferred waste disposal system and offers potential for chemical recycling.

The multiple disposal alternatives of NatureWorks biopolymer means it can play a key role in landfill diversion. NatureWorks biopolymer has been successfully composted in applications where collection is feasible and a commercial composting infrastructure is in place. If land-filled, PLA is inert – it contains no harmful toxins that can leach into the soil.

As you can see there is no "perfect" story for any plastic today used for food packaging. However, we hope you agree that we are attempting to take steps in the right direction to develop alternative solutions.

Tim Dunn

There are a lot of problems with PLA - If we made all of the plastic disposable items used in the world every year, it would take one hundred million tons of corn to make it. That would lead to mass starvation in the third world, as that represents at least 10% of the world's grain supply. Also, in landfills, PLA exudes methane when it decomposes-and methane is a potent greenhouse gas. It also takes a huge amount of diesel to grow, fertilize, ship, and process this corn. As a practical matter, it is also not recyclable. The alternative? Oxo-biodegradable plastics. See for full information. -Tim Dunn

Rene Olivier

Thank your for the feedback thus far. The biggest question is, what is the total amount of energy used in the process? I know of no other way that is more energy efficient than sachets (or bags as some might say) to transport liquids. Traditionally, the biggest problem has been the fact that sachets are messy, you always spill when you cut a corner, and once opened, is exposed to air, in other words you don't have a cap or something to limit the amount of air. Liquid Living has developed a reusable tap/dispeser system that solves both of these issues and thus promotes a more cost effective energy efficient method of consuming liquids by making it more convenient and extending the shelf life once opened as no liquid is exposed to air once opened. See for more detail on how this works.

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