18 June 2010 09:00 [Source: ICB]
Food crops are commonly being used as raw materials for plastics, but researchers are now looking out to sea for future feedstocks
When "plastics" and "the sea" are used in the same sentence, it is often to highlight the problem of pollution. In fact, a boat made of plastic bottles - the Plastiki - is currently travelling across the sea to the Great Pacific Garbage Patch, where plastic waste is alleged to accumulate.
But an increasing number of researchers are looking to get plastics from the sea - not by fishing out discarded bottles, but by using marine life forms as a raw material to make polymers.
Algae is the most promising area of research right now. It is already widely used as a raw material for biofuels, but this is increasingly extending to plastics. US-headquartered Cereplast, which already makes plastics from starch, expects to start producing algae-based polymers by the end of this year.
"The plastics industry is the success story of the 20th century," says Cereplast CEO Frederic Scheer. "But it was built on the back of a single feedstock: oil. To make a success of biopolymers, we need to rely on more than one feedstock."
The theory behind biopolymers is that they use sustainable resources, rather than petrochemicals, as a raw material. A number of established products already exist: Ingeo, from US group NatureWorks, is the company's trade name for polylactic acid (PLA), a polymer derived from corn; MaterBi is a starch-derived polymer from Italian research group Novamont; and US chemical giant DuPont has produced a nylon that is derived in part from castor bean oil. It is also worth noting that one of the earliest polymers to be commercialized, Cellophane, is made from cellulose.
"By 2020, the bioplastics industry could be worth $20bn [€16bn]. To make this happen, we must not create havoc for the commodities we use. We don't want to push up the price of starch - and we don't want to push up the price of food," says Scheer.
"To make a success of biopolymers, we need to rely on more than one feedstock"
Frederic Scheer, CEO, Cereplast
"We've encountered several brand owners in the US and Europe who are concerned about the fact we are using starches - as these are an agricultural resource. They've told us that, as soon as we have algae-based resins, they'll be interested," he says.
Cereplast sources its raw material from companies that are creating "oil from algae" - taking the spent biomass, which "they do not know what to do with," and treating it until it has turned into a powder.
"This is then very similar to starch. We then use the same kind of equipment to process it, although the configuration is different," says Scheer.
There are a few other differences with its starch-based products: they are off-white, while the algae-based product is dark green. Algae also has a distinct odor. The Cereplast factory usually smells like a bakery, rather than a plastics factory; with algae, the smell is closer to a fish processing factory.
Cereplast expects to have two algae-based grades ready by the end of this year: one for injection molding, and one for thermoforming. Its algae-based resins will be designed along the same lines as its starch-based Hybrid Resins. These products, which are not biodegradable, are nevertheless derived in part from a sustainable resource. Its Biopropylene, for example, is derived equally from petroleum and starch - producing a polymer that has "similar physical characteristics" to traditional polypropylene (PP).
Looking further forward - by maybe three years - Cereplast hopes to create resins completely from algae.
"We're starting to work out how to create a monomer from these materials. Once that's been done, we'll be able to polymerize it for lots of different applications," says Scheer.
An ongoing challenge is to have steady access to raw materials. Scheer says that he must be sure that this is solved before ramping up production.
"We don't want to go commercial with these materials, and then not be able to offer them on a consistent basis," he says.
He also has a vision of how the materials might be used further in the future.
"I'd like to think we could create a biodegradable alternative to expanded polystyrene [EPS]," he says. "It often ends up on the beach, or in the ocean as litter. If we could create a monomer that could be used in these applications, these products would biodegrade in the water. The algae would then be returned to the ocean."
This fast-growing sector now has an industry association. The Algal Biomass Organization was created two years ago. While its main focus is biofuels, it also promotes a number of other uses for algae - including water remediation, animal feed and as a polymer raw material.
"Companies such as General Motors, Dow Chemical and Kimberly-Clark attend our conferences, and are looking to use algae-based products. Algae-based resins is one area, though it's quite small. They are a few years behind fuel in terms of commercialization," says executive director Mary Rosenthal.
That said, she says the potential market for bioplastics - of which a growing amount could be taken up by algae - is 45 billion pounds (around 20m tonnes). This is the amount of conventional plastics that could be replaced with sustainably derived alternatives, she says.
Most - if not all - bioplastics are currently derived from "terrestrial" (or land-grown) crops. Rosenthal says algae could offer a key benefit in comparison.
"Corn takes 100 days to mature, but algae can grow - and be harvested - in one week. Algae also has higher yields. Under the right conditions, you could have 50 harvests per year. That's truly sustainable."
At the same time, algae is not an alternative food crop: corn is edible, while algae is not. While some algae crops are taken directly from the sea, most are grown "commercially'"- in open pond systems.
"Algae-based plastics have emerged very quickly into the marketplace. Although very small, they have great opportunity because of their renewability," says Rosenthal.
Cereplast is not alone in its quest to make plastics from algae - although most of the major players have been shy to show their hands.
Algenol, a Florida-based company, has developed a biofuel plant based on algae, as well as setting up a partnership with a number of companies, including compatriot Dow Chemical - which will host a pilot-scale biorefinery at its site in Freeport, Texas. Algenol has devised a way to convert algae into ethanol - which it calls Direct to Ethanol - which can then be used, among other things, as a raw material to make plastics.
Sustainably sourced ethanol has already been used to make plastic: Brazilian petrochemical company Braskem has made ethanol from cane sugar, then converted it into polyethylene (PE) and polypropylene (PP).
And the Soley Biotechnology Institute, a global research leader in microalgae since 2000, is "producing bioplastic from Spirulina dregs." Spirulina is a type of algae.
"When we extract some of the useful materials from Spirulina microalgae, a large volume of dregs are produced as a by-product," it says. "By our newly developed method, we are producing biodegradable plastics with the dregs."
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