Although today it can be said that almost everyone has heard of it we consider it necessary to learn more about it since there are many circulating and discordant rumors...
First of all, it should be said that, in itself, the term does not identify an environmentally friendly alternative wood fuel as it is understood: in fact, this term indicates the cylindrical shape of a compact product of small size resembling a cork or bullet–this term has also been used for a compacting/densification process in the feed and agribusiness sector in general. In fact, pellets have existed as a result of this process for dozens of years and were created to meet the need for transportability, storability of feed for farm animals.
The correct term is “wood pellets,” and we owe its existence to the development of such technologies in the agribusiness and animal husbandry sectors.
It would appear that Canadians were among the first to adopt the “pelleting” process in the feed industry as early as the 1960′s and then, from there, special machines were created to try to densify sawdust more as a waste product from processing logs and lumber in general (1980′s). However, it should be kept well in mind that the presses used to compress sawdust look very similar not to say identical to those for animal feed but in reality have quite different characteristics that also affect the entire production process; this remains to this day a red herring for those wishing to break into this production sector since this belief (and thus facilitation) has recently claimed many industry victims.
Some may ask why so much effort and strain when Mother Nature already provides us with the wood in the natural state we all know, with only the sacrifice of cutting.
The answer is articulated in multiple benefits that are in our view undeniable:
As an example, below is a fuel comparison table with pellets:
|Fuel type||Unit of measurement||Heat output (P.C.I.)*|
|Wood pellets||Kg||4,400 Kcal/h approx.|
|Firewood||Kg||2,500 Kcal/h approx.|
|Methane||Lt||8,200 Kcal/h approx.|
|Diesel fuel (1 Lt=0.85 Kg.)||Kg||8,500 Kcal/h approx.|
|G.P.L. (1 Mc=4.166 Lt.)||Mc||21,500 Kcal/h approx.|
(P.C.I.)* = Lower Calorific Value; that is, the calorific value that does not take into account the latent heat of evaporation of water : in practice, from the total energy released by combustion, that part necessary for the evaporation of the water contained within the fuel is rightly deducted. In the case of biomass, this part of energy is relevant and heavily conditioning the value of P.C.I.
It remains understood that the caloric value of wood has important variations depending on its seasoning and therefore water content. From the diagram above, it is easy to derive what the percentage of savings is compared to traditional fossil fuels: surely 50 percent is a more than reliable average figure, even considering the differences in prices according to areas. If we then consider heating by hot air (stoves, central air generators, etc.) in normal-sized housing and houses, we can reach peaks of 70%. As for the comparison with wood, and at its normal market price, we can say that we are on the same page, with some cases of further small savings.
Ashes and returns:
The other very important aspect of pellets is ash content: in fact, firewood not only has the problem of water content (<40%), which drastically lowers its calorific value, but also that of bark content and various impurities. Most good-quality pellets on the market offer ash contents of less than 1 percent of total weight and water contents of less than 10 percent; this means that the appliance that burns them (e.g., small stoves) will offer the user the possibility of greatly limiting its cleaning and refueling, making pellet burning something acceptable even for those who have always used liquid or gaseous fuels.
Alternatives to pellets:
For fairness and completeness of analysis, it is necessary to make a small comparison with a woody biomass fuel called “wood chips” (from English wood chips). Through the process of shredding/grinding the wood and its waste, a more or less uniform product is obtained, which also allows automatic feeding of boilers and various heat generators. To ns. Way of looking at it, the market for wood chips begins where the market for pellets ends and vice versa: in fact, wood chips still obliges larger automatic feeding systems because of its larger size; the water content, which is always high in any case, does not allow the use of simple and compact combustion chambers but often makes use of very expensive and complex technologies. In practice, regardless of the availability of fuel, the overall investment in woodchip combustion technology is significantly higher, making it uneconomical on small- to medium-sized plants; put simply, there is no point in paying very little for fuel if the small plant has very high depreciation costs.