26.7 gallon is actually 101lt.
turns out it only produces a whole liter if at 30C,
at 20C it produces only 2/3 of a liter per day.
It is usually about 60% methane.
The recomended temperature seems to be 35C or above,
which would require insulation and some kind of heating.
most sustainable would be solar-thermal.
Air inhibits the production of biogas, so would need to make sure incoming matter didn't introduce any. potentially by having a small pre-holding tank, than drains into the main one via hose.
If it does have a lot of air in it, it'll be about a week before it starts producing biogas, since the aerobic processes have to eat it up.
the scientific literature is somewhat confusing in terms of processing time, it seems there are sources for it being 20-30 days for 20C, 35C and 55C.
Considering the space limitations, if 100lt is all that can fit aboard an average vessels, it's not going to be very useful for cooking.
Probably not going to be able to fully process it either,
However can still reduce the smells, by making use of the gas,
for lighting or extra heat, with a simple camping lantern, and a hose/vale coming from the top of your holding tank.