Disadvantages of Wood Fuel

The moisture content in wood is very high 45% to 50% which brings down the boiler efficiency of the boiler and disturbs the furnace condition. Higher moisture content will need more drying time.
Wood is a bulky fuel.
These boilers can degrade more quickly than if not pressurized
Large heat storage and heat dump provisions add to system set-up costs.
Deforestation and in the first place, illegal logging is a serious environmental concern. In the developed countries, the rate of illegal logging is relatively low but it remains high in the developing nations. Unsustainable wood harvesting does not only contribute to the rising levels of carbon dioxide in the atmosphere but it also threatens the local ecosystems and biodiversity.
In comparison to other forms of heating, wood fuel is often less convenient because most stoves and furnaces require refilling every few hours. Due to which heat loss occur.

For all types of Manually fed Boilers, Thermo Packs and Furnaces

Particular	Wood / Briquettes/Coal	Pellets with Injection System
Fuel Consumption	35-50% Higher than Pellets	35-50% Less
Feeding	Manual	Automatic
Ash%	10-20%	Less Than 3%
Startup-Time		30-40 Min Lesser
Maintenance &
Ash Removal	3 Times a Day	Once in 3 Days
Hazardous Smoke	Clearly Visible	Not Visible
Space requirement	Much Higher	60% less
Cleanliness	Worst	Better Housekeeping
Labor	More	Less