The California Integrated Waste Management Board (CIWMB) has published two interesting consultation draft reports exploring plastics which can be composted or degraded.

Degradable Plastics Study (still under consultation)

CIWMB launched a study on June, 2005 on degradable products (those not specifically designed to degrade in a compost facility per ASTM standard specifications) that are commercially available in California.

Research objectives were to evaluate performance, degradation rates, and environmental impacts of various commercially available degradable plastic packaging and disposable food service ware products in commercially operated compost facilities and in simulated marine environments. The study also included compatibility testing with postconsumer material resin, which was not covered in the compostable plastics study.

The composting environments were as follows:


The first compost environment is a laboratory setting that follows the testing procedures outlined in ASTM D6400 standard.
All of the degradable plastics and controls met the phytotoxicity requirements (poisonous to plants). PHA and sugar cane exhibited biodegradation at the end of 30 days. The Kraft paper, cellulose paper, PLA lid, corn-starch based trash bag, Ecoflex bag, LDPE bag, UV-degradable and oxodegradable supported growth of tomato seedlings after 10-days.

The second compost environment is a commercial compost facility at the city of Chico municipal site that is produced from green-yard waste
The corn-starch based trash bag and PLA containers degraded over 95% in 120 days. Small pieces of these materials were observed. The oxodegradable and UV -degradable plastics did not degrade or break down into smaller pieces. The oxodegradable plastics did not biodegrade. The degradation and disintegration results at the municipal compost facility demonstrate that the compostable plastics biodegrade and oxodegradable plastics do not biodegrade under moist green-waste compost

The third compost environment is a commercial compost production facility at the university farm that is made from a mixture of cow manure and straw
The Ecoflex bag, PLA straws, PLA cups, PLA lids, PHA bag, sugar cane plate, and Kraft paper degraded fully after 120 days. Similar to the results at the green-yard waste compost facility, small pieces of corn-starch based trash bag and PLA. The oxodegradable and UV-degradable plastics were not placed in the manure compost due to contamination concerns. The degradation and disintegration results at the municipal compost facility demonstrate that the compostable plastics biodegrade and under moist manure waste compost with in-vessel technologies.

The fourth compost environment is a commercial food-waste compost production facility in Vacaville, CA.
The corn-starch based trash bag, PLA lids, Ecoflex bag and PHA bag degraded fully. The sugar cane lids degraded at similar rates as the Kraft paper control. The oxodegradable and UV -degradable plastics did not degrade or break down into smaller pieces.

The fifth compost environment is a commercial municipal solid waste (MSW) waste compost production facility in Mariposa, CA.
The corn-starch based trash bag, PLA lids, Ecoflex bag and PHA bag degraded fully. The sugar cane lids and Kraft paper were significantly degraded. Several pieces of each were observed. The sugar cane lids had similar biodegradation rate the Kraft paper control.

The sixth biodegradation environment was in and anaerobic digestion vessel
Only PHA and sugar cane exhibited biodegradation at the end of 30 days. The corn-starch based trash bag, PLA cup, Ecoflex bag, and Kraft paper did not generate any biogas and thus did not biodegrade. Likewise, the UV degradable and oxodegradable plastics did not biodegrade.

The last biodegradation testing was in marine environment.
Only PHA experienced biodegrad