Page 9 - Annual Review 2021 full

Annual Review 2021

Fig. 2 Life cycle of a blue fuel

Figure 2 shows the case of a blue fuel, which is produced from fossil sources. But the cleaning and refining
processes are augmented by carbon emissions-control methods such as CCS to reduce its carbon footprint.
The remaining steps in the chain are the same as those used in conventional grey fuels.

Fig. 3 Life cycle of a green fuel

Figure 3 shows the case of a green fuel and the production process which starts with electrolysis of water to
extract hydrogen. The energy used for electrolysis is produced renewably, e.g. from wind power, solar power,
hydropower, nuclear or a combination.

Once hydrogen is extracted from the water, it can be used for different purposes, e.g. it can be used as a fuel
itself, or used with CO2 captured from flue gas using Point Source Capture (PSC) technology or air using
Direct Air Capture (DAC) technology to produce zero-carbon fuels like E-LNG (CH4) with zero GHG emission.

Naturally, the fuel that is produced dictates the requirement for storage, transportation and bunkering.

Although liquefied natural gas (LNG) contains higher than previously expected. Additionally, only
less carbon per unit of energy than conventional 90 of the more than 750 LNG-fueled ships in service
marine fuels, its use might not reduce greenhouse or on order use HPDF engines.
gas (GHG) emissions on a life-cycle basis. As an
example this section compares the life-cycle GHG Using a 20-year GWP, which better reflects the
emissions of LNG, marine gas oil (MGO), very urgency of reducing GHGs to meet the climate
low sulfur fuel oil, and heavy fuel oil when used goals of the International Maritime Organization
in engines suitable for international shipping, (IMO), and factoring in higher upstream emissions
including cruise ships. The analysis includes for all systems and crankcase emissions for low-
upstream emissions, combustion emissions, and pressure systems, there is no climate benefit from
unburned methane (methane slip), and we evaluate using LNG, regardless of the engine technology.
the climate impacts using 100-year and 20-year HPDF engines using LNG emitted 4% more life-
global warming potentials (GWPs). cycle GHG emissions than if they used MGO.
The most popular LNG engine technology is low-
Over a 100-year time frame, the maximum life-cycle pressure dual fuel, four-stroke, medium-speed,
GHG benefit of LNG is a 15% reduction compared which is used on at least 300 ships; it is especially
with MGO, and this is only if ships use a high- popular with LNG fuelled cruise ships. Results show
pressure injection dual fuel (HPDF) engine and this technology emitted 70% more life-cycle GHGs
upstream methane emissions are well-controlled. when it used LNG instead of MGO and 82% more
However, the latter might prove difficult as more than using MGO in a comparable medium-speed
LNG production shifts to shale gas, and given recent diesel (MSD) engine.
evidence that upstream methane leakage could be

9