Plastics designed to degrade don’t break down any faster than their conventional counterparts, according to researchpublished in the journal Environmental Science and Technology . Because most plastics accumulate in landfills and remain intact for decades or longer, some manufacturers have begun producing plastics with proprietary blends of additives that are supposed to make the materials biodegradable, and a number of countries have adopted legislation promoting the use of those additives. But in laboratory tests, researchers found the plastics with biodegradation-promoting additives fared no better than conventional plastics in any of three different disposal scenarios — simulated landfill conditions, compost, and soil burial for three years. Previous research looked at plastics buried in soil for 10 years, the authors note, and found that only 5 percent of the so-called biodegradable plastic decomposed.