So basically the idea is that items from offices (paper blocks, cardboard boxes, paper/plastic cups…) serve as fuel in the fireboxes of the steamers. Items that don’t burn well (PCs, keyboards, mice, mugs, lamps, calculators…) just slide back out.
The idea is that, if you were to run out of coal, you can go to the nearest station and get enough fuel to get to the closest coaling tower