Research into the effectiveness of biodegradable polymers is due to be concluded in December, according to resource minister Rory Stewart.
The findings will reignite the debate about whether plastic carrier bags made with such polymers should be exempt from the 5p charge in England.
The Single Use Carrier Bags Charges (England) Order 2015, introduced in October 2015, required larger retailers to charge at least 5p for each single-use plastic carrier bag. It included provision for exemptions but none was considered appropriate.
Manufacturers of biodegradable bags had lobbied hard for an exemption. But Defra said that would only be possible if a suitable material was identified and techniques to avoid them contaminating the plastic waste stream were found.
A Defra review found there to be a number of standards for plastic bag biodegradability, and in December 2015 the department said further work was needed.
Conservative MP Tania Mathias raised the issue in a written question, asking: “What research [Defra] is (a) carrying out and (b) encouraging into extending the use of materials that biodegrade more quickly?”
Stewart replied by saying that in October 2014 his department had commissioned the Small Business Research Initiative project on biodegradable plastic carrier bags.
“The project is contracted to the plastic packing manufacturer Aquapak Polymers, and is due to report in December this year.
“The project is testing the biodegradability of a hydrophilic polymer under simulated composting and anaerobic digestion conditions, in experiments simulating natural conditions and testing the impact on aquatic life,” he added.