Electric cargo ship

I think a lot of the wasted materials produced by our civilization could be tapped to create fuels.
For example manure ponds exist because there is no disincentive to them.
Biogas digesters are not generally considered to be economically viable but as soon as manure ponds are not allowed, the economics change.
A regional biogas digester can accept human manure,  food waste, even some yard waste.
(Human waste has issues that other waste may not)
Once we accept the responsibility for actually dealing with the waste, any profit becomes a bonus.

I believe that some fuel cells can use the gas produced in biodigesters.

I like the idea of growing azolla or duckweed in greenhouses.
Azolla in particular requires relatively low light conditions.
I wonder if there is a way to do this on the sea, in a floating vessel.

@Eric Hanson

I was really tempted to bring up nuclear because it's the one setting where it really does make sense. Getting the industry to retrain engineers to be able to work on nuclear would be a mammoth task but they have shown that they are capable of it when they created the third officer type, the electro-technical officer.

I would love it if there was the will to get them running on thorium reactors.

The biggest downside that I can see is security. The piracy attacks on merchant shipping are still happening and can you imagine the threat that would pose? It would make the current hostage taking pale in comparison.  

William Bronson wrote:I think a lot of the wasted materials produced by our civilization could be tapped to create fuels.
For example manure ponds exist because there is no disincentive to them.
Biogas digesters are not generally considered to be economically viable but as soon as manure ponds are not allowed, the economics change.
A regional biogas digester can accept human manure,  food waste, even some yard waste.
(Human waste has issues that other waste may not)
Once we accept the responsibility for actually dealing with the waste, any profit becomes a bonus.

I believe that some fuel cells can use the gas produced in biodigesters.

I like the idea of growing azolla or duckweed in greenhouses.
Azolla in particular requires relatively low light conditions.
I wonder if there is a way to do this on the sea, in a floating vessel.

Biogas digesters are now commonplace in the UK. They process a bunch of waste streams.

Public policy helps support them, but they are largely a product of favourable economics. As natural gas prices rise, digesters become more profitable.

William Bronson wrote:
I like the idea of growing azolla or duckweed in greenhouses.
Azolla in particular requires relatively low light conditions.
I wonder if there is a way to do this on the sea, in a floating vessel.

Why not just grow seaweed on the sea?

I posted a week or so ago about a project to grow huge amounts of seaweed in the mid ocean and sink it to the abyssal seafloor as a long term carbon sink. The same seaweed growing systems could be used to feed biodigesters and make methane. Potentially floating biodigesters, to then export the fuel back to shore.

edit: There is some tentative research taking place already.

Seaweed biogas digestion
Notice that this paper talks about 1.5l volumes.

Unlike all other biofuel proposals, using seaweed does not compete with landbased agriculture. It neatly sidesteps the perverse issues of deforestation and fossil fuel burning to make biofuels from human edible crops.

Here is the seaweed thread

Seaweed thread