Development of bio-plastics from rice husks

Abstract

Agriculture is still the main stay of Uganda’s economy contributing 42% of the GDP. Uganda has registered recent successes in rice production making it a potential rice basket for Eastern Africa, paddy production jumped from about 120,000T in 2002 to more than 220,000T in 2011. The extensive use of plastic based on petroleum for over than a century has resulted a major cause towards the environment, all known sources of petroleum will be gone before the end of the 21st century which is estimated through the current rate of consumption of petroleum resources. Burning of rice husk contributes to high CO2 emission and environmental pollution, which further causes health issues. The current study stresses on the reuse of waste lignocellulose biomass (rice husks) for the synthesis of carboxymethyl cellulose (CMC) and further conversion of this CMC into a bioplastic. Addition of commercial starch or gelatin was done to form several bio-plastics due to their capacity to form a continuous matrix. Plasticizers such as Glycerol and citric acid were used to provide flexibility and strength to the film.as-synthesized CMC-gelatin based bio-plastic showed the best fiber-matrix adhesion hence indicating better strength and low brittle fracture as opposed to CMC-Starch based bio-plastic that showed a number of fiber agglomerates and voids indicating exhibition of brittle fracture due to insufficient fiber-matrix adhesion. Surface modification performed on the cellulose fibers lead to formation of CMC through mercerization and etherification, the modification usually focused on changing the polarity of the fibers from hydrophobic to hydrophilic thus better fiber-matrix adhesion. Cellulose exhibited a higher thermal stability than modified CMC (from TGA and DTG thermographs), This is due to inter and intra-molecular hydrogen bonds between cellulose fibers in contrast to CMC,mercerization with sodium hydroxide during CMC production increased amorphous structure of CMC which require lower degradation temperature due to their rapid decomposition than cellulose thus lower thermal stability of CMC,for this same reason CMC-based bio-plastic shifted the maximum weight loss temperature(Tmax) to lower temperatures thus their low thermal stability.Developing Cellulose and CMC using cellulosic wastes (rice husks) can be a sustainable alternative contributing to the production of important value-added products and solving environmental problems caused by adverse methods of rice-husk waste management such as burning.