Which is cheaper – wood briquettes or firewood?
There’s something special about lighting a fire in a wood burning stove using firewood. It crackles, looks beautiful and creates a cosy atmosphere in the home. But is it also the cheapest kind of fuel for you?
Whether you just bought your wood burning stove or if you’ve been an owner of one for many years, you’ve probably been wondering about what kind of fuel to use.
Different factors determine what kind of fuel an owner of a wood burning stove uses to fire with. For some, wood briquettes are out of the question because they don’t look as beautiful in a wood basket as normal firewood does. For others, the important thing is having a cheap source of heat. If you belong to the latter category, calculations show that you should aim to buy wood briquettes.
It is cheaper to use wood briquettes
It’s difficult to calculate which kind of fuel is the cheapest. The Danish website fyrogspar.dk has asked engineer M.IDA Kurt Jacobsen to do it.
The result of the calculations is that you’ll get a 4 % higher heating value if you buy wood briquettes and not firewood that has been cut, split and stacked.
You can read the details of the calculations below.
The engineer’s calculation of heating value
The calculations are based on Danish prices for a pallet of 2.1 cubic metre of firewood (beechwood, oakwood and ashwood) that has been cut, split and stacked compared to a pallet of 960 kilograms of regular wood briquettes. The prices come from the biggest Danish suppliers and include delivery.
Prices vary depending on the supplier, but on average a pallet of wood briquettes is 5.88 % more expensive than a pallet of firewood. But a real comparison takes into account how much heat you will get out of the fuel you’ve bought. That’s what you call heating value.
The heating value of firewood
In order to compare the heating value of regular firewood to wood briquettes, you need to know something about the density of the wood and the moisture content. This will tell you something about the energy content (dry matter + water) per cubic metre.
In this example, engineer Kurt Jacobsen has estimated the total weight of the fuel to be 1053 kilograms – 842 kilograms of dry matter and 211 kilograms of water.
The heating value for dry matter is 19 MJ/kilogram = 5,226 so the energy in total is 4400 kWh for the firewood on the pallet. You have to take into account the energy that is lost when the water content evaporates during combustion. That’s why the heating value is 4253 kWh.
Heating value of wood briquettes
The heating value of wood briquettes is calculated the same way as the regular firewood’s heating value was. The water content is presumed to be 6 % so the wood will weigh 902 kilograms and the water content will weigh 58 kilograms. That corresponds to an energy content of 4714 kWh and an evaporation loss of 40 kWh. So the efficient heating value for the wood briquettes is 4674 kWh.
Comparison of wood briquettes to firewood
The calculations show that a pallet of wood briquettes contains more energy than a pallet of firewood. But before the comparison of the two, the price difference has to be taken into account.
The engineer does that by dividing with the factor x/100+1. X is the extra charge of the wood briquettes in percentage terms. So when the energy content has been adjusted, the heating value is 4414 kWh if you buy wood briquettes that cost the same as the firewood (which had an energy content of 4253 kWh).
Regular wood is more eco-friendly
If you’re environmentally conscious when you fire in your wood burning stove, you should pick regular wood. Research done by Technologie- und Förderzentrum in Bavaria shows that regular wood provides the best basis for complete combustion – as long as you fire correctly and always use dry wood in your wood burning stove. Read about the test here.