TITLE:
Influence of Weather and Purity of Plasticizer on Degradation of Cassava Starch Bioplastics in Natural Environmental Conditions
AUTHORS:
Michael Ahimbisibwe, Noble Banadda, Jeffrey Seay, Betty Nabuuma, Evans Atwijukire, Enoch Wembabazi, Ephraim Nuwamanya
KEYWORDS:
Bioplastic, Degradability, Purified Glycerol
JOURNAL NAME:
Journal of Agricultural Chemistry and Environment,
Vol.8 No.4,
November
29,
2019
ABSTRACT: The threat posed by plastics to the environment has prompted the
development of bioplastics. Starch plasticized by glycerol is a key renewable
resource in the production of high-quality bioplastics. Previous studies have
availed information on the mechanical quality of starch-based bioplastics
however there is limited information about their degradation pattern in the
natural environment which this research presents. Bioplastics were buried in
holes in loam sandy soil and weekly photographic data and weight were collected
to reveal the effect of degradation. Weather parameters of rainfall, temperature,
relative humidity, sunshine intensity and sunshine hours were recorded to
establish influence of weather on degradation. A control set up in the
laboratory was used to compare the results. Over time the tests revealed that
as the hydrophilic enzymes break down the bioplastic, its weight initially
increases (up to 87%) due to absorption of moisture and after saturation, the
bioplastic is disintegrated which initiates decomposition and the bioplastic
weight is steadily reduced. Degradation was further enhanced by invasion of
soil organisms like worms, termites among other soil microbes. Rainfall (r = 0.857) increased the moisture in the soil which
initially increased the weight of the bioplastic up to a point when the
hydrophilic enzymes set into breakdown the bioplastic then the weight started
to drop. This was the same case for relative humidity (r = ﹣0.04) however; the sunlight intensity (r = 515) and hours of illumination indirectly affect the
process by influencing microbial activity. An increase in the sunshine
intensity increased the activity of soil organisms up to a point beyond which
increased exposure caused the organisms to burrow deeper in the soil. Increase
in microbial activity increased the rate of degradation of the buried
bioplastics which took five to ten weeks to fully decompose (98.3%). The
reduced time of degradation means that starch-based bioplastics have a high
potential as sustainable substitute for petroleum-based plastics.