Since conventional plastics are made from fossil fuels, are not biodegradable and are turning our oceans into huge plastic garbage dumps (plus they are entering our food chain), more and more companies and institutions are developing alternatives that are more environmentally friendly and are cost-competitive at the same time. But it is not so easy to find decomposable alternatives that are non-petroleum-based. Plastic made from corn, sugarcane ar other plant-based materials isn't always degradable, and at the same time you don't want it to degrade while still using it.
Natureworks, a company based in Minnetonka, Minnesota, is one of the world’s leading manufactures of bioplastics. The company makes polylactic acid, or PLA, a biodegradable plastic made from cornstarch and makes into a wide range of consumer products — including single-use flatware, cups and packaging — that decompose at the end of their useful life. The company’s initial production facility in Blair, Nebraska, came online in 2002 and can produce 150,000 tons of PLA per year. The company recently announced plans to open a second plant in Southeast Asia that would use sugarcane. However, at this moment bioplastics are still a small fraction of the industry, with less than 0.5% of all plastic coming from non-petroleum sources (according to the Society of the Plastics Industry, an industry trade group based in Washington, D.C.) Another company is Metabolix, Inc, based in Cambridge, Massachusetts, where bioplastics are developed in laboratory-scale fermentation chambers. They teamed up with Honeywell to develop Polyhydroxyalkanoates, or PHA, a bio-based plastic that is more expensive but also more versatile than PLA.
The downside of using plastic sourced from crops is that these use significant amounts of water, pesticides and fertilizers that can cause air and water pollution and compete for land with crops grown for food. A solution to this problem is provided by Novomer, a company founded as a result from research at Cornell University in Ithaca, New York, that is turning waste CO2 from ethanol production plants into plastic. The company makes polyols — polymers used to make flexible foam found in mattresses, seat cushions and insulation, as well as a range of specialty coatings and sealants. The polyols made by Novomer are degradable, but lose their degradability when combined with petroleum-based chemicals to make foam.
Geoffrey Coates, a chemistry professor at Cornell University in Ithaca and a co-founder of Novomer, is working on a new biopolymer with properties comparable to or perhaps better than polyethylene, the most widely produced thermoplastic that you can find back in everything from trash bags to water bottles to plastic toys. Even a thin layer of polyethylene is incredibly strong. “Most of that is because it’s a semicrystalline material,” Coates says. “The [polymer] chains pack next to each other in a very tight and specific fashion that overall, gives pretty impressive properties.” The new material, called poly (polypropylene succinate) and made from a sugar feedstock, hasn’t been tested on the time it needs to degrade in a landfill or marine environment. But based on its composition, Coates says, it should begin to decompose in water after several months, a time period that normally exceeds the useful life of most single use products. Poly (polypropylene succinate) breaks down into propylene glycol and succinic acid, nontoxic materials that are further reduced to CO2 and water when ingested by microbes.
Another initiative can be found at University of Nottingham where bio engineers are studying how to use shrimp shells, rather than food crops, to make biodegradable shopping bags and food packaging. Shrimp shells are part of the waste problem in Egypt and using a degradable biopolymer for bioplastic bags leads to lower carbon emissions and a reduction in food and packaging waste. The material is made from chitosan, an artificial polymer made from the organic compound chitin, which is extracted from crustacean shells. Chitosan is biodegradable polymer that is antimicrobial, antibacterial, and biocompatible. This substance is used to make a nanocomposite material that is biodegradable, affordable, and suitable for shopping bags and food packaging.
Not only is it very hard for bioplastics to compete with conventional plastic from an economic point of view (they are so cheap, and in order to have all (or at least a big portion of) plastic made from non-petroleum sources would require significant government support, such as fees that would make petroleum-based plastic more expensive). There is another reason why bioplastics is not the solution we need to solve the single-use plastic pollution problem. Contrary to what many people believe, bioplastics do not decompose unless they are treated under the same conditions as compost. The natural breakdown of the plastic will not happen if it is simply tossed in a landfill with other trash or if it ends up in the ocean. When biodegradable plastics are put into landfill they produce harmful greenhouse gases when breaking down. Another problem with bioplastics is that people might be thinking that it is ok for them to litter, because they assume that the products will biodegrade anyway. Jacqueline McGlade, chief scientist at the UN Environment Programme: "It’s well-intentioned but wrong. A lot of plastics labelled biodegradable, like shopping bags, will only break down in temperatures of 50C and that is not the ocean. They are also not buoyant, so they’re going to sink, so they’re not going to be exposed to UV and break down."
A part of the solution to plastics in the ocean is better waste collection and recycling, especially in the developing world, the UN said. We have to look beyond the current take-make-dispose extractive industrial model and aim for a circular economy to redefine growth, focusing on positive society-wide benefits. In a circular economy economic activity is decoupled from the consumption of finite resources, and waste is designed out of the system and involves a transition to renewable energy sources.