Hot Alkaline Digestion of NODAX™ PHA

Dishwasher Detergent, Steam and Poof! It is gone.

by Isao Noda, MHG CSO and Senior VP of Innovation

MHG’s Nodax™ PHA is produced by microbial fermentation of locally harvested vegetable oil, and it is completely biodegradable in many different natural environments with or without the presence of oxygen.

This unique property of Nodax™ PHA provides tremendous opportunities of this class of materials in broad applications where products arrive at the different end of life destinations, including composting, landfill, or even among items littered on the land or in the ocean. No other materials have such versatility of disposal, while still possessing highly desirable mechanical properties comparable to those of conventional petroleum-based plastics.

Practical means to dispose of MHG’s Nodax™ PHA are not limited to biodegradation. For example, it can be safely incinerated without generating harmful gases like some plastics.

More interestingly, it can also be readily digested using a simple and safe chemistry called hydrolysis. Hydrolysis literally means reaction with water and is a chemical process in which a molecule is cleaved into two parts by the addition of a molecule of water.

Nodax™ PHA is classified as a polyester that is susceptible to hydrolysis. However, it is actually a surprisingly stable material capable of withstanding attack of acid or alkaline exposure under normal use conditions.

Interestingly, this unexpected chemical stability of Nodax™ PHA against acid or alkaline attack suddenly diminishes when the temperature is raised to above 120°C (248°F). This is a temperature range easily achievable using low-pressure steam or autoclaves.

MHG's Isao Noda graphs PHA digestion rates by temperature
The above graphs show the experimental evidence of the rapid hydrolysis of Nodax™ PHA in the presence of highly alkaline dishwasher detergent (Procter & Gamble’s Cascade™) but only at an elevated temperature. The material remains stable below the boiling point of water (100°C), which covers most of the use conditions. The implication of this unique temperature-sensitive chemical stability property could be quite interesting.

Single use medical items made of MHG PHA can be disposed of via incineration or hydrolysis without toxic outputs.For example, current disposal of medical waste, such as tubing, syringes, and surgical gowns, relies almost exclusively on incineration. Unless the hospital has an on-site incinerator to handle such waste, they have to be transported under strict conditions to appropriate far-away places for burning. This actually is a very expensive process.

Now imagine the possibility of sticking these medical wastes into slightly modified autoclaves or steam chambers with a touch of dishwasher detergent. If the products are made of MHG’s Nodax™ PHA, they will be digested into harmless and pasteurized liquid, which might be safely flushed down to the sewer system. Intriguing possibility, isn’t it?