|All bioplastics begin with a plant’s naturally-occurring sugars or starches, and sugar cane or corn starches are often the preferred feedstocks. But potatoes, which can contain from 13% to as much as 23% dry matter (starch) depending on their water content, may be ideal for some plastics. “Potatoes are starch factories,” according to Dr. Qiang Liu, who headed the bioplastics research team of the BioPotato Network, funded by Agriculture and Agri-Food Canada’s Agricultural Bioproducts Innovation Program. More than 30 food scientists, molecular biologists and plant production specialists across Canada investigated possible functional food-ingredient and non-food applications in an effort to find new, more profitable crops for Canada’s potato farmers, whose crop was valued at nearly US$1.13 billion in 2009.
|Fermentation, heat, chemical manipulation or even microbes are used to turn a sugar or starch feedstock into the building blocks-polylactic acid, hydroxymethylfurfural or poly-3-hydroxybutyrate-used as the basis for the even more complex and varied chemical creations we call “plastic.” Once thermoset plastics solidify, their polymer strands form tangled bonds that cannot be undone without destroying the plastic, and they are tough and temperature-resistant. In contrast, thermoplastics can be moulded, melted, then moulded again. Transparent polylactic acid (PLA) is obtained from starch fermented into lactic acid, then polymerised, and has characteristics similar to polyethylene and polypropylene. It can be processed with equipment already used for petroleum-based plastics for a wide range of products, including computer casings, food and other packaging, even biodegradable medical implants. Thermoplastic starch(TPS), currently the most widely used bioplastic, can be derived from potatoes or from corn. Plastarch Material (PSM) is a biodegradable, thermoplastic resin, composed of starch modified to give it heat-resistant properties and combined with other biodegradable materials to improve flexiblity or give it other characteristics, and is used for food packaging and utensils, plastic bags, temporary construction tubing and stakes, foams, films, window insulation, and planters, and some are biodegradable in compost, wet soil, and water, and by some microorganisms. Scientists are now experimenting with microbes that can convert natural sugars and oils into biodegradable polyhydroxyalkanoate (PHA) materials.
|“People do confuse biodegradability and bioplastics. Not all bio-based products are biodegradable, and not all biodegradable products are bio-based,” Liu says, explaining that biodegradability can be engineered into a bio-based or petro-based product. High temperatures are required to break most bioplastics like PLA down, usually in commercial facilities that maintain temperatures of between 40° C to 65° C. But Liu notes that using renewable feedstocks such as potato starch or dry matter to produce carbon-based polymer materials will benefit the environment, whether or not the end product is biodegradable. The production of one metric ton of bioplastic generates between 0.8 and 3.2 fewer metric tons of carbon dioxide than one metric ton of petroleum-based plastics. Thus, the development of bioplastics will help control and even reduce CO2 emissions, says Liu, “helping to meet global CO2 emissions standards set by the Kyoto Protocol, and provide for an improved environmental profile.”
|The BioPotato Network’s research goals included manipulating potato starch to produce bioplastics with stronger mechanical properties and greater water resistance and to make them easier to work with. “In some cases, it is easier to modify potato starch than corn starch,” Liu observes, and he and his team were able to make some significant discoveries. “We successfully developed various novel starch-based bioplastic products,” he says, including TPS with fibre from potato and pea, TPF using potato pulps derived from different potato varieties, TPS with PLA and nanofiller, and TPS combined with a common mineral nanoclay. “A significant outcome was finding a paraffin wax that maintains biodegradability while reducing moisture sensitivity compared to PLA as an additive.” The scientists wanted to focus next on starch-based foam to replace current non-bio-based foam. “Unfortunately, the program ended in March 2011,” says Liu, but he hopes the government will consider renewing it.
|Source Courtsey krishijagran.com