Researchers at Ghent University have developed a process that turns grass into the hydrocarbon decane via a lactic acid intermediate. The process was the basis for the doctoral dissertation of Way Cern Khor.
To improve the biodegradability of grass, pretreatments such as extrusion and calcium hydroxide pretreatment were performed; efficiencies were tested through biogas production. Next, a fermentation process using mixed microbial populations was carried out to produce higher value products such as lactic acid.
From here, lactic acid was converted into caproic acid (C6H12O2) (also called hexanoic acid—a carboxylic acid normally produced from hexane). Caproic acid was further converted into decane (C10H22) (an alkane hydrocarbon) via Kolbe electrolysis (a decarboxylative dimerization of carboxylic acids). Decane has many uses, such as aviation fuel.
Different extraction technologies for lactic acid were also tested to investigate the advantages and disadvantages for each technology. The research of each individual process unit gives a complete process pipeline for a grass biorefinery.
The amount of biofuel that can be made from grass in the laboratory is currently limited to a few drops. The results indicate that the overall conversion can be highly efficient, though.
If we can keep working on optimizing this process, particularly in cooperation with industrial partners, the efficiency will come up and feasibility will follow.—Way Cern Khor
Stephen J. Andersen, Vicky De Groof, Way Cern Khor, Hugo Roume, Ruben Props, Marta Coma and Korneel Rabaey (2017) “A Clostridium Group IV Species Dominates and Suppresses a Mixed Culture Fermentation by Tolerance to Medium Chain Fatty Acids Products” Front. Bioeng. Biotechnol. doi: 10.3389/fbioe.2017.00008