Sugar Oil as sustainable marine fueLs

Introduction

This project considers crude sugar oil (CSO™) as a fuel for internal combustion engines, specifically those that propel sea-going vessels. CSO™ is produced from cellulose, and a stable blend with fossil marine fuel is created through emulsification. The SOL project aims to validate the technical and economic viability of this fuel source whilst also achieving a greater than 80% relative greenhouse gas (GHG) emission avoidance during the first ten years of operation compared to the reference scenario.

Global Sugar Production

Globally, sugars are produced by photosynthesis at a scale of roughly 100 billion tonnes per annum, mostly in the form of cellulose (a polymer of glucose units). By contrast, a “mere” 5 billion tonnes per annum of fossil-based oil is pumped out of the ground.

While sugars are abundant fuels in nature, SOL is the first project in the world to optimize and scale up their use as transport fuels. This requires two process steps:

1. The conversion of cellulose to crude sugar oil (CSO™) by means of dilute acid hydrolysis.
2. The emulsification of CSO™ with heavy fuel oil (HFO).

Historical Context of Hydrolysis

The use of dilute acid hydrolysis to convert cellulose to sugar dates back to the late 19th century. Historically, hydrolysis conditions were optimized to achieve a maximum sugar yield, since in nearly all commercial settings, the target product was ethanol.

In SOL, the objective is to maximize the yield of CSO™, which also contains some sugar derivatives, notably levulinic and formic acid, which would act as inhibitors to the fermentation of sugar to ethanol. CSO™, being a blend of sugar (derivatives) in water, does not readily blend with HFO, so it requires emulsification.

Stable sugar-water-HFO blends are prepared with the aid of surfactants that allow for the polar sugar molecules to form a stable emulsion with apolar HFO.

Advantages of CSO™

Currently, cellulosic ethanol is the go-to transport fuel that is produced from cellulose. However, unlike cellulosic acid, sugars can be used directly in engines, without the need for downstream fermentation and distillation operations, which are both expensive and energy-intensive.

Bypassing the need for these processes results in greater GHG emissions avoidance. Moreover, the CSO™ process also offers superior atom economy, with more than 90% of the carbon in the cellulose feedstock ending up in the transport fuel compared to less than 50% in the case of cellulosic ethanol.

As a result, this process delivers more fuel calories per unit of biomass in the combustion process than competing ethanol technologies and therefore supports the decarbonization targets for the maritime sector, as outlined in the ‘Fit for 55’ Section of the EU Renewable Energy Directive.

Project Scale-Up

The SOL project will increase the technical maturity and scale of this production technique from a 1 kiloton per annum (ktpa) demonstration plant to a 5 ktpa commercial plant in the Port of Rotterdam. When the project is complete, the aim is to develop a full-scale 250 ktpa plant in the same location.