Bioplastics: an important component of global sustainability uses figures from Brazilian plastic and bioplastic company Braskem, among other sources, to show that for every kilogram of non-biodegradable biopropolyene manufactured there is a net sequestration, or negative carbon footprint, of about 2.3kg of CO2.
This is compared to a net gain of over 5kg of CO2 for each kilogram of traditional plastic.
Degradable bioplastic also offers advantages over its petroleum-based cousins, the report said, but these advantages are less pronounced. Degradable plastics compost back into carbon dioxide and water, returning all the sequestered carbon to the atmosphere.
This situation is worsened if the bioplastic did not compost in air, “but rotted in an oxygen-poor landfill,” according to the report.
“In these circumstances, the plastic would degrade into methane (CH4) and other byproducts. Methane is a global warming gas of greater impact than CO2 and so the full carbon footprint needs to include any uncaptured CH4 produced in landfill,” the report says.