Green Bunkers, Eco-bunkers, Bio-bunkers, Renewable Bunker…Caveat Emptor!

By Ara Barsamian, Eliseo Curcio, and Daniel Son, Refinery Automation Institute, LLC
Monday January 18, 2021

With efforts to save the planet from global warming and recognition of the need to protect the environment, many countries and the UN have been considering stricter greenhouse gas, SO2, and NOx emission regulations.  This pressures IMO and other standards organizations to adopt stricter rules to be followed by fuel suppliers, shipowners, oil terminals, and refineries.

The pressure to find solutions to become more environmental-friendly is pushing for 0 emission targets. One potential solution that is heavily being researched is alternative fuels. However, this is an idealized solution, since many alternative fuels are not yet ready to be utilized as bunker fuel replacement – e.g., global infrastructure is not ready for LNG, and not enough research has been done to use Hydrogen, methanol, or ammonia. Nevertheless, among these alternative fuels, Biofuel has caught the attention for its potential.

Biofuel as a possibility has been promoted because of its promise to reduce CO2 emission, limit Sulfur level in fuel to 0.5%, provide higher mileage, and improve lubricity. Saving planet while burning fuel with superior mileage, doesn't that sound too good to be true? Well, CAVEAT EMPTOR! That is, buyer beware!

In order to understand the pros and cons of Biofuel, it is important to look into what they really are. There are two classes of biofuels commercially available on a large scale:

  • First-generation Bio-Diesel, which is FAME (fatty acid methyl ester)
  • Second-generation Bio-Diesel, which is Renewable diesel

Both generations of Biofuels are produced by processing biomass (see Fig.1). FAME is produced through a process called Trans-Esterification, which utilizes catalysts and methanol to transform vegetable oil into FAME. Renewable diesel is produced through Hydrogenation to produce HT VO (Hydrotreated Vegetable Oil) or through the Fischer-Tropsch synthesis process to transform vegetable oil into BTL FT (Biomass to Liquid Fischer-Tropsch synthetic diesel).

These two generations of Biofuel have very different characteristics, which ISO8217 also clearly distinguishes (see Fig. 2). FAME diesel is relatively cheap to make, but it is not necessarily carbon-neutral. Most importantly, FAME, with its superior lubricity properties, covers the engine parts with sticky gum, which promotes corrosion and mechanical damages. This became the fundamental basis for ISO8217-17 section 5.1 to specifically ban the deliberate blending of FAME in RM grade fuel (Residual Bunker Fuel), and that FAME level should not exceed the "de minimis" level or 0.5 volume percent.

On the other hand, renewable diesel's properties are indistinguishable from those of petroleum-derived diesel. Because it does not do any damage to the engine, there is no limit to the amount that can be used in marine fuels, whether marine gasoil or residual bunkers. Not only that, compared to FAME, it has higher quality because it has cleaner burning (higher cetane), and its production has lower carbon GHG footprint intensity, and can use a wider range of feedstock, such as algae.

A number of companies have advertised "Green bunkers", "eco-bunkers", and "biobunkers". Some of these companies use renewable diesel in their RMG bunkers and comply with ISO8217.  The renewable diesel is used as a diluent of residues, such as ATB, VTB, and VBKB, generally in less than 10 volume percent with a healthy dose of LCO and slurry to maintain aromaticity. Other companies are using FAME type biodiesel in "biobunkers", and it is not clear from their descriptions if it is a marine distillate with FAME or RM grade with FAME, the latter contravene ISO8217 section 5.1

So, watch out for misleading information when it comes to "BIO". Using fuel containing FAME, not only against the regulation, but it will easily destroy the engine parts. Need more advice on this issue? We are covering these in detail in our brand-new on-line bunker blending course. We also provide consulting service to whom needs help with. Feel free to contact us at: