It converts CO2 and H2O into ethane and ethylene, oversimplifying the output is natural gas. What do you do with the natural gas?

You can put it in pipes and send it to a central location, but you need pumps and the pipes are a nightmare.

You can store it in a local tank but you need a pump again, and burn it but it release the CO2 again. Using a solar panel and a battery is easier and more efficient.

(Do they need also some water pipes?)

For a distributed production, solar panels are much better.

Pipes and pumps may work in a centralized setup, but I'm still not convinced it's better that biodiesel or ethanol.

Photosynthesis is very inefficient, so there is a lot of room for improvement. But plants are like self building robots and they store the output in grains that are easy to transport.

Right now they’re a fantasy so they can be as large or small as your imagination permits.