Majority of the conventional plastics and composites used today are derived from petroleum, a non-renewable resource. A very high percentage of these materials end up in the landfills causing significant end of life disposal problem. Plant based natural polymers offer a sustainable, yearly renewable and environment friendly solution to the current plastic waste problem. Biodegradable polymers such as polysaccharides and proteins obtained from plants, animals and microbes are convenient and offer several advantages over petroleum-derived synthetic polymers. In the present research environment friendly processes were developed to crosslink starches to achieve higher mechanical properties as well as lower hydrophilicity. Thermoset starch based polymer resins were developed using polycarboxylic acids as crosslinking agents, utilizing a completely 'green' water based processes. The reactivity of starches varied owing to the inherent differences in the internal structure of the starches depending on their origin. Nanocomposites were fabricated by incorporating micro/nanofibrillated cellulose (MFC) in thermoset starch based resin. Incorporation of MFC showed significant enhancement in tensile properties (strength, stiffness and toughness) of the nanocomposites. The starch based resins were characterized for their adhesive properties for bonding wood. It was observed that the shear strength of the adhesive increased with increase in amylopectin content as well as with the increase in crosslinking of the starch based adhesive. Studies were compared to commercially available Tite Bond 2 adhesive which is considered a superior adhesive for wood. The research was also conducted on soy protein which also is an abundantly available biopolymer. Soy proteins are available commercially as defatted soy flour (SF), soy protein isolate (SPI) and soy protein concentrate (SPC). Of all these varieties SF, which contains about 55% protein and 32% carbohydrate, is the most easily available and inexpensive material and was used for this research. A novel, clean crosslinking reaction scheme was developed to separate the carbohydrates, modify them and use to crosslink the separated soy protein in soy flour. This process completely avoided the use of any external crosslinker. The resulting crosslinked protein was shown to have enhanced mechanical, thermal and moisture absorption properties comparable to commercially available plastics and composites.