Back on topic. Conversions of solid-fuel apparatus to oil, gas or other automatic-supply fuels will be a very rare event, given that many of these will have been obsolete for decades.
More likely is that the electrician may see an oil fired unit converted to burn....
solid fuel! 
Step forward..dah! dah! The wood pellet central heating burner!
These are popular in Nothern Europe, where they gotta lotta trees. The pellets are made from waste wood, highly compressed into cylinders about 5/16" diameter x 1" long. The 'glue' is lignin, which is part of the wood's structure. It 'melts' at about 200F in the pressing operation and is a natural binder. Pellets are force dried after pressing.
Here's a few samples of the genre from Denmark:
http://wood-pellet-ireland.blogspot.com/2006/06/danish-pellet-burner-units.html Ignore the political drift. The information is basic, but the pics are good.
Costs? Not good, given that a quality p.j. oiler can be had locally for well under $500. They will get cheaper in time.
These are obviously second cousins to the pressure jet oil burner. Ignition on the 80,000 btu model I examined locally was by an electrical hot-plate, set in a tiny firebed, which was raised to about 500-700F prior to a burn. There may be an issue here on the electrical costs of starting up? It took about 15 seconds to get to 'ready to fire'. The next [automatic] sequence was the start of a screw-auger to pull up pellets from a store bin. A small quantity of pellets [about 3 oz?] tinkled into the firebox, the fan started and she was away! Much quieter than a pressure jet. This cycle of three ounces of pellets was repeated every 60 seconds or so. As this was a friend's brand new machine, [ I noted the yellow duster on the bench, we are all the same us techno geeks, aren't we!
], I felt it to be slightly discourteous to rip it apart to find out how the fuel is metered- it may be just a timer. Pellets are very dry, between 6-10% moisture, [as compared to c.18% for airdry cordwood], and must be stored & kept dry. Their net calorific value will be c. 6000 btu/lb @ 10% m.c. This value takes account of the wood's hydrocarbon contribution, [one pound of hydrogen burns to about nine pounds of water!]. With any biomass fuel, a low liquid water content is vital. All water in the fuel [or formed in combustion] must normally leave the stack as steam, as water has a tendency to fall downwards! One pound of water needs c. 1000 btu of latent and sensible heat to convert to steam. This is why wood has a much lower net heat content than coal.
Ash is removed weekly. Wood has surprisingly little ash content, compared to that of coal at any rate.
Controls are exactly the same as for a diesel burner, a roomstat/programmer giving 'calls' to start/stop the burner.
Store bin was 4 cubic metres, 140 cubic foot, the pellets being 'blown' in pneumatically by a bulk tanker. The auger draws pellets up to about 6 feet before they drop toward the burner inlet port.
Pellets are supposed to be 'eco friendly' as they reduce the use of fossil fuels, plus the CO2 is continuously cycled to the atmosphere. My criterion would be cost. Pellets at 10% moisture content need to be priced at under US$200 a ton to compete with oil today and give one a payback to justify the capital outlay if converting from destroying fossils. In my area the price is too high IMHO, at c.= US$320 per ton. I may add that many of these machines will also burn corn [maize] kernels. I costed shelled maize locally at c.=US$180/ton in bulk. It also contains a small % of oil, so its calorific value is c. 8% better than wood at the same m.c.
I'll post a pic of my mate's set up, if I can break in to his boiler room un-noticed next week....
Alan
