(In)Formation

Yes. Wood from forest maintenance (pruning and density management) or rejected wood and wooden leftovers coming from industrial process can be used as energy source for heating and cooking.

The valorization of such “residual” woods as an energy source can be an incentive to keep forest well maintained, minimizing the fire risk, and even to increase the forest areas in order to ensure a sustainable balance between available wood and consumption demand.

Compared with the use of wood, pellets require a simple industrial transformation, for which some nonrenewable energy sources may be required. However, the transformation of the wood into pellets allows a more efficient transportation, so its use can be more efficient that the use of the wood depending on the distance between the place where the wood is collected and the place where it will be use and how easy it is to ensure that dry wood will be available.

Ideally the access to this “residual” wood should be ensure to trees and woods (Árvores e Bosques) planted near the place where the wood will be need and the sustainable maintenance of the wood should be ensure.

An efficient device will take the most of each kilogram of wood/pellet introduced into the combustion chamber and will minimize the pollutants gases emissions released during the combustion (mostly carbon monoxide).

Primary efficiency measures the ratio between the amount of energy produced through the combustion and the amount of potential energy contained on the wood/pellets. So a 90% ratio of primary efficiency means that 90% of the potential energy contained on the wood/pellets will be transformed into heat energy and 10% will not be transform into heat being lost through smoke exhaustion.

Secondary efficiency refers to the proportion of the heat generated that is converter into heat for the room or rooms. So a 90% ratio of secondary efficiency means that 90% of the heat produced inside the combustion chamber will be transfer to the room or rooms being heated.

From the point of view of sustainability it is important to use a device with high primary efficiency, which reduces waste released by the combustion as fumes, charcoal and tar, but also a device with a high secondary efficiency, that for the same performance for house heating and food confection will demand a less quantity of heat produced inside the combustion chamber.

Some devices can, but they need to be equipped with a heat exchanger, a proper safety mechanism and a heat accumulator tank.

Some tips to keep in mind:

Level of automatization required

If you want to control the heat intensity, the hour of starting and finishing the combustion then you will need to consider a pellets device. Some pellet devices can even be controlled through your smartphone.

Pellets devices can be feeding with several hours of autonomy.

Diameter of the fumes exit

The smoke exhaustion on a pellets devices generally require an 80 mm diameter pipe while the wood devices require substantially higher diameters, usually between 150mm and 200 mm.

Storage and transport

Both storage and transport of pellets are much simpler than the storage and transport of wood, requiring a substantial lower space for the same quantity of energy storage/transported.

Device cleaning

A pellet device produce a substantially lower amount of ashes than a wood device.

Price

Wood prices are usually substantially lower the pellets price. The cost difference can even be more significant if the firewood could be storage during the summer to be used during the winter.

A firewood device is usually less expensive than a pellet device with the same functions and similar characteristics.