Ashes from burning coal:
If the ashes are from burning coal, then you must be more aware of proper ash removal for
many reasons. First, you will have much more ash to remove versus wood. Second, coal ash
is not beneficial to a garden because its potassium and phosphorus content are very low
compared to wood. Third, coal ash also contains a great deal of other elements, such as
cobalt, boron, and arsenic among others, which are toxic to plants, animals, and people.

Fuels Emission of Carbon Dioxide - CO₂

When burning coal the ash can trap unburned carbon which means
that more unburned fuel is tossed away with coal ash versus wood.

When there are no longer any potentially "live" coals, you can bag
and dispose of coal ashes at a waste transfer station or the local landfill.

Coal Ash Note: you will get approximately 18 gallons of ash / ton of coal that you burn.

Smoke:
Smoke is essentially water vapor and unburned fuel,
caused by an incomplete burn and the quality of the fuel supply.
In order for the fuel to burn completely, the right environment must exist.
This includes the proper mix of fuel, oxygen and heat, which is what these forced
draft outdoor hot water furnaces are designed to do when they are burning!

Hence why you will create smoke when an appliance is "throttled down" or idles (if it is
automatic controlled and has no demand or manually choked down). This is why you should
load your appliance more often with less fuel, as a smaller fire is a hotter fire that will burn
more efficiently with less ash and smoke. If your appliance has a glass door you should always
beable to see the fire through it! It should never creosote up to the point that you cannot
see the fire, if the glass creosotes up think about what the inside of your chimney looks like.