This is a series of post on my work in the field of green marine fuel.

First of all, for marine companies that are considering switching greener fuel, choosing the right marine fuel is no easy task. To me, there are two major hurdles. First, there are many possible pathways. Here is a partial list:

  • Liquefied natural gas (LNG)
  • Biofuel
  • Methanol (either from natural gas, or coal)
  • H2 (could be from Biofuel, natural gas, coal, oil, solar)

So there roughly a dozen choices. The second is about the cost of converting the current infrastructure. This post only discusses the first issue.

A sensible methodology is to compare each alternative on a USD/Gigajouele ($/GJ) fuel cost basis. That is, how much does it cost to generate 1 GJ unit of energy? 1 GJ is about 278 Kilowatt hour, by the way. See for detailed definitions.

There are several major contributing factors in calculating fuel cost:

  1. Cost of purchasing the primary energy.
  2. Cost of converting primary energy into a fuel. This will be a fixed investment cost of building the conversion facility that is spread over the lifetime of the facility.
  3. Operating and maintaining the energy facility.
  4. Distributing a fuel.

These costs need to traded off the cost of carbon emission. To illustrate this, I use Taljegard et al‘s numbers as input. Let me first summarize their results with the following chart:

As is seen above, using natural gas (NG) and methanol are the cheapest options, although the current dominant fuel of oil is also among the cheapest. The most expensive one to convert solar energy into H2, and all the H2 solutions are relatively more expensive. However, these costs do not factor in Co2 emissions, which are illustrated below:

We can combine these two costs, but of course we will need the price of carbon. How would the total costs change as a function of carbon price? Here is my result:

With current carbon price below $0.1/KgC, the cheapest solution is to use natural gas. However, carbon price climb above $0.3/KgC, H2 from Biomass using CCS becomes the most attractive. This is because this technology can actually sequester more carbon than it emits.

Biofuel emits no co2, and therefore becomes more attractive when carbon price is high. Coal and oil as a primary energy sources become less attractive when producers need to pay more for their emissions.