Biofuels may not become the zero-carbon solution of choice in the shipping industry’s decarbonization process in the longer term, but could have a significant role to play to accelerate the process. In a recent article DNV GL summarizes the regulatory issues, safety and other operational issues faced by those using these new fuels or fuel blends.
One of numerous possible ways to comply with the IMO’s strategy on the reduction of greenhouse gas (GHG) emissions from ships is to use biofuels or biofuel blends. Biofuels have very low sulphur levels and low CO2 emissions, as such they are a technically viable solution in meeting some of the current and future emission requirements. However, their NOx emissions might be higher than with fossil diesel oils and another immediate challenge is that the shipping sector still have limited knowledge on handling and applying biofuels as part of their fuel supply.
DNV GL is an independent expert in risk management and quality assurance and a frequent collaborator with Gard in in loss prevention and sustainability projects. We are pleased to re-publish their recent information and advice with respect to the increasing use of biodiesel in bunkers.
Types of biofuel
Regulatory items on biofuels to be observed
MARPOL Annex VI Regulation 18, “Fuel Oil Availability and Qualities”, applies to using both fuels derived from petroleum refining and derived by methods other than petroleum refining, e.g. biodiesel. Note that in this context, synthetic fuels according to EN 15940 are not considered to fall under “fuels oils derived by methods other than petroleum refining.” These synthetic fuels include the subgroups such as Hydrotreated Vegetable Oil (HVO), Biomass to Liquid (BTL), Gas to Liquid (GTL and Coal to Liquid (CTL) which are different resources converted to fuels though chemical processes.
In the case of biodiesel, the fuel shall, among others, not exceed the applicable sulphur content. Moreover, such fuels shall not cause an engine to exceed the applicable NOx emission limits. Meeting the sulphur limits is normally not a challenge for biofuels, however the NOx emissions might be higher than with fossil diesel oils, due to possibly high oxygen content.
To meet the requirements of MARPOL Annex VI, evidence must be made to confirm that the diesel engine complies with the applicable NOx emission limits (which depend on the keel laying date of the vessel and the operational area) also when biofuels are used for combustion purposes. To demonstrate this, depending on the biofuel used, the evidence may be a challenge and it may require on-board emission testing where the results should be presented in g/kWh (not only concentrations in ppm). Due to the complexity of the required tests, DNV GL recommends performing the emission tests on stationary test beds and offers to assist ship operators with obtaining the required exemption from the flag administration.
DNV GL also advices that, as an alternative to the measurements, and in case it can be proven by either analysis or reference to a known international standard that the emission properties of the biofuel are equivalent to that of conventional diesel, this evidence might act as proof that the biofuel does not cause the engine to exceed the applicable NOx emission limits.
If additional alterations, which are beyond the limits in the approved NOx Technical File, the engine(s) are required to optimize the combustion when using the biofuel, and the NOx Technical File needs to be formally amended.
Technical challenges and solutions
Below is a summary of items to be observed for the use of biofuels and a few words on how to prevent damages on board:
We thank DNV GL for permitting us to share this information with our readers. The original version of this article, with more information about DNV GL’s service offering, can be found on the DNV GL website.