(Invited) Novel Fuel Production Based on Sonochemistry and Sonoelectrochemistry
Authors: Islam Md Hujjatul , Lamb Jacob J. , Lien Kristian M. , Burheim Odne Stokke , Hihn Jean-Yves , Pollet Bruno G. 
Published: February 2020

Power ultrasoundhas been used in many applications such as the chemical and processing industries where it is employed to improve both catalytic and synthetic processes and to produce new chemicals. This technology area has been termed sonochemistry, which mainly focusses on chemical reactions in solutions yielding an increase in erosion of catalytic surfaces, reaction kinetics, and product yield [1,2]. Sonoelectrochemistryis the study of the combination of ultrasound and electrochemical processes and its applications [2-4]. This area of research covers various studies from organic syntheses, polymeric materials syntheses, production of nanomaterials, environmental (soil and water) treatments, water disinfection, corrosion of metals, analytical procedures, film and membrane preparations to the elucidation of electrochemical mechanisms in various ‘exotic’ solvents.

In the ongoing energy transition from a fossil based energy economy to a renewable energy economy, most of the energy input will change from readily storable carbons and hydrocarbons into intermittent electricity. [5] This means that we need to both process electricity efficiently and intensively into forms that are storable and portable. Such a mix is likely to be presented by chargeable batteries, hydrogen systems and biofuels. Power ultrasound is a tool that can allow for more intensive and more efficient ways for the energy conversion required in the coming generation and here we look particularly on efforts within production of hydrogen and biofuels.

Hydrogen is an attractive fuel source due to its rather high specific energy compared to other conventional fuel. There are various methods available to produce hydrogen. However, most of the methods are not environmentally friendly, since they release large amount of fossile CO2(ca. 7.05 kg of CO2per kg of H2production). Power ultrasoundcould be an attractive alternative since ultrasonication of water produces clean hydrogen. Power ultrasound breakdowns water molecules into OH• and H• radicals, where the recombination of these radicals produces hydrogen. It is crucial to characterize the amount of radicals formed by ultrasonication in order to understand and further developing the hydrogen production process using ultrasonication [4].

Global biogas production has been growing significantly in recent years. A new generation of feedstocks, potentially allowing extensive increases in yields, is currently under development based on lignocellulosic-containing residues. However, lignocellulose presents a bottleneck due to its’ rigid and obstinate structure. Pre-treatment of feedstocks can be achieved in a variety of ways including enzymatic hydrolysis [6,7] and steam explosion [8]. In this research, a new method has been applied using power ultrasound coupled to Fenton reagents to assess its ability to improve the yield of biogas from steam exploded birch wood. In our conditions, an increase in the yield of 5% and an increase in the rate of production of 7% of biogas has been observed.

[1] B.G. Pollet, M. Ashokkumar, Introduction to Ultrasound, Sonochemistry and Sonoelectrochemistry, B.G. Pollet, M. Ashokkumar, Eds.; SpringerBriefs: Berlin, Germany, 2019; in press.

[2] B.G. Pollet (Ed), Power ultrasound in electrochemistry: from versatile laboratory tool to engineering solution, John Wiley & Sons (2012) ISBN: 978-0-470-97424-7.

[3] B.G. Pollet, A short introduction to Sonoelectrochemistry. Electrochem. Soc. Interface
2018, 27, 41–42.

[4] Md.H. Islam, O.S. Burheim, B.G. Pollet, Sono(electro)chemical Production of Hydrogen, Ultras. Sonochem. 51 (2019) 533-555.

[5] O.S. Burheim, “Engineering Energy Storage”, Academic press, ISBN: 9780128141007, 2017.

[6] J.J. Lamb, S. Sarker, D.R. Hjelme, K.M. Lien, Fermentative bioethanol production using enzymatically hydrolysed saccharina latissima. Adv. Microbiol. 2018; 8(05)

[7] J.J. Lamb, D.R. Hjelme, K.M. Lien, Biomethane potential from enzymatically hydrolysed Saccharina latissima. Adv. Microbiol. 2019; 9(04).