Biodegradable additives are additives that enhance
the biodegradation
of the polymers
by allowing microorganisms to utilize the carbon within the polymer chain
itself. Biodegradable additives attract microorganisms to the polymer through quorum
sensing after biofilm creation on the plastic product.
Additives are generally in masterbatch formation that use carrier resins such as polyethylene,
polypropylene,
polystyrene
or polyethylene terephthalate.
Testing methods of biodegradable additives
ASTM D5511-12 testing is for the "Anerobic
Biodegradation of Plastic Materials in a High Solids Environment Under
High-Solids Anaerobic-Digestion Conditions"
ASTM D5526-12 testing is for the "Standard Test Method
for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated
Landfill Conditions"
ASTM D5210-07 testing is for the "Standard Test Method
for Determining the Anaerobic Biodegradation of Plastic Materials in the
Presence of Municipal Sewage Sludge"
Laboratories performing ASTM testing methods
- Eden Research Labs
- Respirtek
- NE Laboratories
- NSF
Biodegradation process of biodegradable additives
A simple chemical equation of the process is:
C6H12O6 → 3CO2 +
3CH4
Definition of this process is as follows - In most cases,
plastic is made up of hydrophobic polymers. Chains must be broken down into
constituent parts for the energy potential to be used by microorganisms.
These constituent parts, or monomers, are readily available to other bacteria. The
process of breaking these chains and dissolving the smaller molecules into
solution is called hydrolysis. Therefore, hydrolysis of these
high-molecular-weight polymeric components is the necessary first step in
anaerobic biodegradation. Through hydrolysis,
the complex organic molecules are broken down into simple sugars, amino acids,
and fatty acids.
Acetate and hydrogen produced in the first stages can be
used directly by methanogens. Other molecules, such as volatile fatty acids
(VFAs) with a chain length greater than that of acetate must first be
catabolised into compounds that can be directly used by methanogens.
The biological process of acidogenesis
results in further breakdown of the remaining components by acidogenic
(fermentative) bacteria. Here, VFAs are created, along with ammonia, carbon
dioxide, and hydrogen sulfide, as well as other byproducts. The
process of acidogenesis is similar to the way milk sours.
The third stage of anaerobic digestion is acetogenesis.
Simple molecules created through the acidogenesis phase are further digested by
Acetogens to produce largely acetic acid, as well as carbon dioxide and
hydrogen.
The terminal stage of anaerobic biodegradation is the
biological process of methanogenesis. Here, methanogens use the intermediate
products of the preceding stages and convert them into methane, carbon dioxide,
and water. These components make up the majority of the biogas emitted. Methanogenesis
is sensitive to both high and low pHs and occurs between pH 6.5 and pH 8. The remaining,
indigestible material the microbes cannot use and any dead bacterial remains
constitute the digestate.
Biodegradable additive manufacturers
- EcoLogic LLC
- EcoSafe Plastic
- BioSphere Plastic[5]
- ENSO Plastics
- Bio-tec Environmental
- Hybrid Green
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