By Lynne Peeples
FairWarning.org
Environmentally-conscious shoppers tend to be drawn to labels that say "compostable," meaning the product is biodegradable under the right conditions. But they might not be aware of a critical drawback:As biodegradable materials break down in a landfill, which is where they usually end up, they can release methane, a potent greenhouse gas with climate warming effects upwards of 30 times that of carbon dioxide.