Technological improvements are needed to make some bio-based chemicals environmentally competitive
Bio-based chemicals made from renewable materials are helping to reduce the chemical industry’s dependence on fossil fuels. But without vast improvements, some bio-based processes won’t be any kinder to the environment than their petrochemical equivalents - as a new study on bio-based glutamic acid and its potential industrial products demonstrates.
Glutamic acid is an amino acid needed to make other useful molecules, including chemicals involved in plastics production. Researchers at the University of Wageningen in the Netherlands compared the environmental impact of producing four industrial chemicals from glutamic acid isolated from vinasse - a by-product of sugar beet processing - with petrochemicals.
They used a life cycle assessment (LCA) approach to understand the impact of each stage of the production process on the environment under categories spanning, among others, use of land and resources, climate change, ozone layer depletion and toxicity to different types of ecosystems. There are currently no commercial bio-based processes for the chemicals the authors studied, the proposed routes being based on small scale experiments or designs. However, their results suggest that only two of the four chemicals could be made using vinasse as a feedstock in a way that would be environmentally competitive with traditional routes.
Bio-based N-methylpyrrolidone (NMP), a solvent used in paints and plastics, performed better overall than its petrochemical equivalent, as did N-vinylpyrrolidone (NVP). But acrylonitrile, an ingredient in acrylic fibres, and succinonitrile, didn’t measure up. ’There is still room for improvement for all of the processes,’ says Tijs Lammens, one of the authors of the study. ’One of them, acrylonitrile, I don’t expect to be competitive by the bio-based route we discovered, to be totally honest.’
The production process for bio-based acrylonitrile was environmentally harsher under every category, due largely to one particularly exothermic reaction of the glutamic acid intermediate with sodium hypochlorite that would require electricity for cooling. On the other hand, petrochemical-derived NVP lost out to its bio-based alternative in eight out of 11 categories and NMP in seven. Although there were some large uncertainties about how much heat and electricity would be needed to isolate glutamic acid from vinasse, the researchers say that for bio-based NMP and NVP, the environmental impacts are ’competitive’.
Last year, the EU launched Biochem, a €4.5 million (?3.9 million) scheme that provides support for chemical companies switching to renewable feedstocks. Adrian Higson, a bio-based chemicals expert at the UK’s National Centre for Biorenewable Energy, Fuels and Materials, says the Dutch researchers make a good case for glutamic acid as a target for companies developing new bio-based approaches. But politically, he thinks it is unwise to carry out environmental impact assessments at such an early stage in development.
’[Policymakers] will pick up a LCA and say they won’t support that technology because it’s not as good as the incumbent technology,’ says Higson. ’But it will never be as good unless you give the technology a chance to evolve and develop. You’ve got to look at what the LCA could be in the future and then decide whether to support it.’
Lammens, however, argues early stage LCAs can help identify areas in a bio-based process where there is room for improvement. He says assessments should be carried out throughout development. ’Once a process is better established you will have to re-do your complete LCA, but you shouldn’t wait for your process to be operational before you do the first analysis, because the results may actually be more helpful in shaping your process,’ he says.
Projections of the market potential for bio-based products vary wildly, with some suggesting the global market could be worth $250 billion (?162 billion) by 2020, although Higson thinks estimating market share is a ’finger in the air exercise’. The US Department of Agriculture estimates that 20,000 bio-based products are currently being manufactured in North America and has certified dozens with a ’bio-preferred’ label, denoting a high percentage of bio-based ingredients. Bio-based processes have already been adopted by the likes of Dow and BASF, who are making polyols - used in foams - from soybean and castor oil.
Meanwhile, biotechnology company Genencor has developed an isoprene replacement, BioIsoprene, which is made from renewable raw materials such as corn. The company is partnering with Goodyear to incorporate the product into its tyres. Christopher Dettore, Genencor’s LCA specialist in San Francisco, California, says the industry is ’acutely aware’ of efforts in LCAs and relies on these types of studies to guide process development, as well as to differentiate products already in the marketplace. ’Bio-based products...are not necessarily more sustainable than alternatives,’ says Dettore. ’This is something that needs to be evaluated on a case-by-case basis. LCA is the way to do this.’
T M Lammens et al, Environ. Sci. Technol., 2011, DOI: 10.1021/es201869e