A material that is compostable is not necessarily biodegradable. However, a material that is biodegradable is inherently compostable under the right conditions.

There are multiple forms of composting, and they do not function equally. A home composting system with limited control over humidity, temperature, pH, and bacterial concentration is vastly different from an industrial composting facility, which is specifically designed to break down materials like PLA under controlled conditions. 

Greenwashing is widespread, particularly in marketing. Simply labeling a product as “compostable”—regardless of font size or shade of green color—does not mean it can be discarded in a backyard composting system. The specific composting method required must be indicated, such as "Industrial Compostable" or "Home Compostable." 

Marine environments are the most sensitive biomes on the planet. While they cover 71% of Earth's surface, with 96.5% comprising the oceans, the long-held notion that “the solution to pollution is dilution” has led to widespread misuse. Instead of diluting, we continue to accumulate plastic pollution in marine ecosystems year after year. 

Biodegradation testing in marine environments is among the most complex and rigorous. These ecosystems have significantly lower bacterial concentrations, making them one of the most challenging conditions for assessing true biodegradability. 

Biodegradability alone is insufficient if the material releases toxins during degradation. Composting bioplastics serves no benefit if the resulting soil is contaminated with exotoxins, posing risks to plant growth and human health. 

Ecotoxicity and fragmentation testing are essential to verifying true biodegradability. Without proper testing, materials that claim to be "biodegradable" may still contribute to microplastic pollution and environmental harm.  Thus, we have adopted the Marine Biodegradable Standard from TÜV Austria for our PHAs.

The testing is made up of three consecutive trials. First, starting with ASTM6691, using sea water collected from nearby shores and paper (cellulose) as the benchmark for sustained biodegradability within the environment. For materials to pass ASTM6691, they must degrade as fast or faster than paper. The measurement for the degradation is CO2, thus validating bacteria activity in the medium. This test lasts 6 months, it cannot be accelerated or modified.

The second test utilizes the same seawater used during the first test and introduced microscopic crustacean life, specifically “Daphnia magna,” a species of water flea. To pass, they must survive at a 90% rate for a 24-to-48-hour exposure period.

The third and final test evaluates the fragmentation effect, ensuring that the material breaks down when exposed to a marine environment. This assessment uses cellulose (paper) as a benchmark and is considered the most challenging to meet, as it verifies the material's biodegradability in such conditions.

Please note that mixing drinking water with table salt does not accurately replicate an oceanic environment required for degradation. This mixture lacks naturally occurring bacteria and other organisms necessary for this process. Therefore, testing PHA printed parts in salted water is ineffective.

Cellulose (paper) is used as a benchmark because we understand its degradation rate and environmental impact. This makes it an excellent reference for creating biopolymers that minimize negative effects if mismanaged.

What are the loopholes? When money is involved in marketing claims, companies will exploit them. The common issue is the misuse of ASTM6691. This test supports biodegradation evidence but isn't perfect. It uses seawater at 27°C, unrealistic temperature compared to average ocean temperatures of 5-6°C, impacting bacteria activity and degradation speed.

Additionally, the test stops at 80% biodegradation instead of 100%, allowing companies to mix expensive PHA with cheaper alternatives such as PLA and still pass. While toxicity testing should control this, some companies manipulate parameters or skip true toxicity tests.