Sea squirts new raw material to bioethanol

Published: 27 February 2017

Cellulose from Swedish large- scale seacultivation system of sea squirts is to be used for the production of bioethanol. Marine Biogas AB in Lysekil, developers of a large-scale cultivation of sea squirts for the production of biogasi, is initiating a collaboration with Luleå University of Technology. Scientits will utilise the tunicate cellulose-rich outer shell, to produce ethanol.

– We will develop a process that enables us to utilise the outer casing of the sea squirt to produce bioethanol equivalent to fifty percent of the annual demand for ethanol in Sweden, said Paul Christakopoulos, a Professor of Biochemical Process Engineering at Luleå University of Technology.

The mantle is extremely rich in cellulose

It is all about the Swedish sea squirt, Ciona intestinalis, a pouch-like organism which belongs to the tunicate family (invertebrates). It feeds on phytoplankton and is grown on a large scale cultivation system on the west coast. The species are solitary, but often sit close together in large numbers. The Swedish sea squirt is about eight centimeters high, has a protective cover, a so called mantle that researchers at Luleå University of Technology are very interested in. The shell of the sea squirt Ciona is in fact composed of 60 percent of the cellulose-like substance tunicin. Researchers will demonstrate that it is possible to inexpensively at a large scale produce high quality bioethanol from tunicin. Researchers at the Biochemical Process Engineering lab report positive results and successful testing so far.

– Early testing shows that we can achieve a conversion of around 85 percent of ethanol from tunicate cellolose. We now look to improve the process further, says Ulrika Rova, professor of Biochemical Process Engineering at Luleå University of Technology.

Energimyndigheten has assigned 4.7 million

Luleå University of Technology and Marine Biogas AB have been awarded 4.7 million by the Swedish Energy Agency to develop the process of producing bioethanol from sea squirts. The European Commission wants to find other sources than terrestrial plants for the production of bioethanol and hence marine resources naturally becomes more interesting. It is possible to extract large amounts of cellulose of cultivated sea squirt. One hectare of cultivation can provide 200 ton cellulose per year. This is believed to equate a large part of Sweden's current annual bioethanol consumption.

– The large-scale cultivation of sea squirts is likely to become more common in marine environments.  The cultivated biomass can be used as raw material for renewable energy (biogas) or to produce organic feed. Sea squirts have the ability to bind considerable amounts of nitrogen and phosphorus and can therefore contribute greatly to reduced eutrophication in lakes and other bodies of water. Furthermore they are highly valuable as fish- and livestock feed as they do not contain heavy metals and their inner body has a high protein and lipid content, says Ulrika Rova.

The cellulose contains no lignin

Unlike the biomass from forest residues, the tunicate cellulose contains no lignin or hemicellulose.  The absence of lignin makes it possible to successfully pre-treat and break down the tunicate cellulose with enzymes. The mantle of the tunicate largely consists of cellulose and also has a high crystallinity (coherent structure of large surface).

 Researchers at Luleå University of Technology aim to develop a process that integrates the most relevant achievements in the field of organosolv pretreatment (in this case, to pretreat the tunicate cellulose), enzymatic hydrolysis (which with the help of enzymes break down the cellulose into glucose) and fermentation for bioethanol production.

This is a project related to research in Bio4Energy.

Ulrika Rova

Ulrika Rova, Professor

Phone: +46 (0)920 491315
Organisation: Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering