How seaweed can produce sustainable plastics

Materials World magazine
31 Jan 2019
Microorganisms that produce polyesters to make the bioplastic. Image Credit: Tel Aviv University

A process to produce bioplastic polymers derived from seaweed has been developed in a bid to address plastic waste. Idha Valeur reports. 

A biodegradable polymer that doesn’t break down into toxic materials and recycles into organic waste is now possible, thanks to a new process. 

Dr Alexander Golberg and Professor Michael Gozin, both from Tel Aviv University, Israel, discovered the method in their efforts to tackle the global plastic epidemic. 

The new polymer is derived from microorganisms that feed on seaweed, named polyhydroxyalkanoate. As it is not made of petroleum it doesn’t produce chemical contaminant by-products, presenting a more sustainable alternative to conventional plastics. 

According to Golberg, bioplastics could be a partial solution to the waste problem, but even they have an environmental price tag, requiring fertile soil and freshwater to grow the plants that are home to the bacteria. This makes the process less sustainable, but the researchers say that using seawater eliminates this obstacle. 

Golberg told Materials World, ‘Our process produces both feedstock and final polymers using only seawater. The idea is to use offshore cultivation for biomass production and halophytes fermentation, so we do not use arable land or freshwater for the process.’ 

Golberg estimates that the polymer could degrade into CO2 in six months, however, he says, they have no yet tested this but it is a current research project. 

Although there are factories already producing bioplastics, they are dependent on large areas of land and freshwater. Now, this new process could enable producers in countries such as Israel, India and China, which don’t have access to large amounts of freshwater, to swap petroleum-based plastics to biodegradable ones. 

‘Plastic from fossil sources is one of the most polluting factors in the oceans,’ Golberg said.  ‘We have proved it is possible to produce bioplastic completely based on marine resources in a process that is friendly both to the environment and to its residents’. 

Will it be enough? 

When asked if this method could be scaled up to meet the huge demands required if, in theory, many manufacturers swapped to bioplastics, Golberg said, ‘In the future, yes. Our previous studies dealt with the estimation of the offshore biomass potential. We show that for optimum fresh weight stocking density of 4kg m–2 the total potential of offshore cultivated ulva biomass, our seaweed feedstock, is of the order of 1,011 dry weight (DW) tonnes year−1 , over a surface area of around 108km2. But the technology for such an offshore cultivation is still not there.’ 

New development processes and materials are next on the agenda for the researchers, according to Golberg.  But how quickly could this technology be commercially implemented? As Goldberg says, ‘It all depends on the industry which needs to risk time and money. There is a need for a combination of biotechnology industry in large scale with polymer companies. Our process is scalable.’

The study, Macroalgal biomass subcritical hydrolysates for the production of polyhydroxyalkanoate (PHA) by Haloferax mediterranei was published in the journal Bioresource Technology.