Green plastics from citrus fruit peels and sugar
The need for bio-plastics is growing. Brand owners are looking for sustainable solutions for packaging, fibres, paints, inks and plastics. This creates a need for high-performance bio-plastics such as polyamides (PA) and polyesters (PET).
The total global production of PET polymers was over 50 MT and that of PA over 10 MT in 2015. Furan dicarboxylic acid (FDCA) -based polyethylene furanoate (PEF) polymers offer a bio-based alternative to petroleum-based PET polymers. Polyamides are used in applications calling for high durability and strength. Muconic acid is a versatile monomer which can be converted to multiple PA monomers such as adipic acid, terephthalic acid, hexamethylene diamine, caprolactam, caprolactone and 1,6-hexanediol. Polyamides (PA) are used as engineering plastics, for example in automobiles.
New prospects for the use of pectin
VTT has developed a process to convert pectin biochemically to an aldaric acid, which in turn can be chemically converted to monomers for bio-based polyesters and polyamides. Pectin is a side stream obtained from citrus fruit peels or from sugar beet pulp.
Sugar beet pulp is currently used as animal feed, but the goal is to use the pulp for higher-value applications. Pectin is currently underutilized as the production is only about 40 000 t/a, with the potential of several tens of million tonnes available annually. Its current use is in the food and beverage industry as, for example, a gelling agent. In addition to pectin, wood- or plant-based glucose can be used in the production of aldaric acid.
Competitive new technology
VTT has patented a technology combining biotechnical and chemical reaction steps to produce FDCA and muconic acid from aldaric acids. The first step consists of the oxidation of galacturonic acid, a constituent of pectin, to galactaric acid with a fungal biocatalyst. The conversion efficiency is high and this step has been scaled up to pilot scale (300 l) delivering kilogramme amounts of galactaric acid for the second step conversion.
The second step converts the aldaric acid into furan carboxylic acid (FCA) and FDCA or muconic acid depending on the reaction conditions. FDCA is a monomer for polyethylene furanoate (PEF), a bio-based alternative for polyethylene terephthalate (PET). Muconic acid is a precursor for polyamide monomers.
The techno-economic analysis shows competitive pricing and the life cycle analysis shows that the carbon foot print is lower compared to petroleum-based alternatives for both monomers.