Decarbonizing shipping with e-fuels from crude sugar oil

For billions of years, sugars have fueled almost all living organisms. Here, Dr. Michael Booth from Vertoro explains how raw sugar butter can aid their clients’ decarbonation process.

Direct Air Capture (DAC) of CO₂ for the production of so-called e-fuels is often touted these days as a revolutionary technology that can play a big role in decarbonizing the transport sector. Therefore, it may come as a surprise to learn that the DAC of CO₂ of sugars achieved through photosynthesis is more than three billion years old. This probably makes sugars, specifically glucose, the most ancient of e-fuels, given that almost all flora and fauna – past, present and future – convert (release) glucose through cellular respiration (i.e. oxidation) into chemical energy and heat.

Glucose as e-fuel

This “godfather of e-fuels” is produced on a scale of approximately 100 billion tons per year, mostly in the form of cellulose – a polymer of glucose units. Importantly, this figure is less than the roughly five billion tons of fossil oil pumped out of the ground each year.

Unfortunately, neither cellulose nor glucose has ever been used as an internal combustion engine (ICE) fuel. The “man-made” distinction was added because all flora and fauna are internal combustion engines running on sugar (glucose) by design. This begs the question, why don’t we use glucose as an e-fuel to help decarbonise hard-to-cut sectors like shipping?

The answer is practical. Glucose is solid at room temperature and internal combustion engines usually run on liquid or gaseous fuels. Furthermore, it is insoluble in all commercially used fuels; whether non-polar petroleum-based species such as heavy fuel oil (HFO) or the less common polar varieties such as methanol or ethanol.

Finding a solvent for glucose

To resolve this discrepancy, we need to find a cheap, stable and non-toxic solvent for glucose that is somehow also compatible with commonly used transportation fuels. Mother Nature uses water as this solvent. Of course, water and oil don’t mix easily, as a kitchen sink experiment will quickly confirm.

One way to overcome this is to use a so-called surfactant. In everyday use at home, we use soap as a surfactant to mix oil and water. Surfactants are molecules that have a hydrophilic or hydrophilic head with an oleophilic or lipophilic tail. In our case, the water-loving end must be compatible with a high concentration of uncultured sugars dissolved in water—crude sugar oil (CSO™)—with the oil-loving end being susceptible to HFO.

Both the use of water and sugars in HFO may sound a little strange. In fact, there is a positive effect of oil and water emulsions on hazardous engine emissions. The presence of water improves the atomization process of the fuel (especially if the oil droplets are below 10 microns) and lowers the combustion temperature, thus limiting soot and nitrogen oxide (NOx) emissions respectively.

Adding water-soluble modern biofuels to the mix isn’t new either. Quadriceps, a London-based fuel innovator, is actively trialling (on a large container ship in commercial service) bioMSAR™ – an emulsion of HFO in water and glycerin – a by-product of biodiesel production – with MSC, the world’s largest container shipping company . Previously, the same company conducted trials of oil-in-water emulsion (MSAR®) container vessels with Maersk, the world’s second largest shipping company.

In chemical nomenclature, glycerin belongs to a class of carbohydrates called sugar alcohols and occurs naturally in fermented foods and beverages, including beer, honey and wine. Therefore, replacing sugars with glycerin in such emulsion compositions may also be possible.

Indeed, stable bioMSAR™ emulsions were successfully prepared by the Quadrise laboratory based on the replacement of glycerin with second-generation (advanced) sugars, mainly xylose and glucose, which were produced by Vertoro from lignocellulosic forest residues.

Using sugars directly in engines, rather than first fermenting them to ethanol, which is the standard fuel valorization route for sugars today, is attractive for several reasons. First of all, half of the carbon in sugar is lost to CO₂ during the fermentation process.

Second, since fermentation takes place in an aqueous environment, the isolation of ethanol by subsequent distillation is highly energy and capital intensive, not least because water and ethanol form an azeotrope, requiring a particularly complex, multi-step evaporation process to separate the two compounds.

Will sugar help decarbonise the container shipping sector? Follow our progress online with Quadrise and stay tuned.

Please note that this article will also appear in the twelfth edition of our quarterly publication.