No can do, boss. I have a troll allergy. I will do the math to compare these steam plants, Otto cycle DF engines, and diesel cycle DF engines based on that number, though.
According to hy-Bon.com 50'000 SCF of natural gas is 2636.4 lbs. That number works out to about 242 g/kwh for this googled up steam power plant.
According to this guy, an Otto cycle duel fuel engine can average 25% less than a sea-going natural gas steam plant. If we assume that a seagoing steam plant does as well as a shore-based steam plant, then we can guess that the Otto cycle DF engine gives us a kwh for every 182 grams of natural gas. That same guy also says that the diesel cycle DF engine can average 50% less than its sea-going steam equivalent, which is something like 121 g/kwh.
The promo material says that the most fuel gas wasted up the stack by the diesel cycle DF is 0.2 g/kwh, which is 1.7 % of the 121 g that was put in. But usually so much less as to be "undetectable." It also says that the Otto cycle DF engine slips 5-10% of its fuel, which would be 9-18 g/kwh. Steamer, you say that a land-based natural gas steam genny slips 1000 g/1000000 SCF. When I do the conversation assuming that it is using 242 g/kwh, it only slips 0.01 g/kwh, which is 0.04% of the fuel.
That's an interesting result. The steam plant uses twice the fuel for each unit of power, but puts out only 1% as many CH4s. It must put out about twice the CO2, though. But CO2 is way better for your global warming contribution report than CH4. I guess if you want to save money on fuel, you choose a diesel cycle DF engine and if you want to report a low global warming number you choose a steam plant. Although, presumably the ME-GIs that are used for onshore power generation nearly always operate in the optimal "undetectable" slip condition, so maybe it's the all-around optimum.
Do my numbers look reasonable to you guys?
Btw, the ships mentioned in the OP are using this ME-GI engine.