The briquettes these unknown…

Wood is one of the most important renewable sources of energy found in nature.

In addition to being neutral with respect to CO₂ emissions, wood and its by-products are cheaper than conventional fossil fuels in respect to the same amount of heat supplied.

In Italy, woody biofuels play an important role in the powering of heating systems: firewood, wood chips, pellets and briquettes. Firewood is the most common and known wood fuel, whose consumption reaches about 17 million tons per year, pellets show a consumption of about 3,5 million tons while for wood chips there is an annual consumption of 1,5 million tons, according to the data registered in 2018. These biofuels, especially pellets, are largely imported from abroad, from countries in which the costs of raw materials and labor are lower if compared to the Italian situation.

Among the different types of woody biofuels mentioned above, the briquettes, despite they are a biofuel produced since 1970, have the least diffusion and they are not still fully appreciated on the market.

One of the most popular uses of the briquettes is for food cooking in pizzerias and bakery, but they can also be used, instead of firewood, in boilers, stoves, fireplaces stove and traditional fireplaces for domestic heating.

Production similar to pellet

The production process of the briquettes is similar to that of the pellet: they are, in fact, a pressed product derived from woody materials such as wood sawdust or other wood waste deriving from specific processes.
It also must considered that their packaging makes them more handled: a cardboard box allows for tidy and clean storage and conservation of 20 kg of briquettes.

The quality of the briquettes, as for all other woody biofuels, can be assessed by referring to a specific technical standards, in particular UNI EN ISO 17225-3: 2014: “Solid biofuels – Fuel specification and classification – Part 3: Definition of wood briquette classes”.

It should be noted that the reference technical standard and the Italian legislation only allow the use of untreated virgin wood and that any additives can only be natural and used to the extent of less than 2%.
The briquettes, usually with a circular or octagonal section, have a length of no more than 30 cm and a diameter of about 8 cm; in the last few years, briquettes with particular shapes have also been produced to make them not only an original product, but to better adapt them to combustion.

Higher density

Compared to firewood, the briquettes have a higher density. Considering beech as a wood species, briquettes have a density of 1100 kg / m³ to be compared to 750 kg / m³ for firewood; it therefore follows that, for the same volume and water content, the briquettes are characterized by a higher energy density (Table 1)

Being a product derived from an industrialized process, the briquettes have a stable moisture content, with values below 15%, which allows to maintain the shape and ensures good mechanical durability. Furthermore, deriving from untreated virgin wood waste, the ash content is less than 1,5%.

The briquettes are also characterized by an excellent net calorific value than for beech briquettes, that represent the majority of those offered on the market, is equal to about 4,6 kWh / kg with a moisture content of 10%.

As already mentioned, the briquettes being a product obtained by compression of sawdust, have an energy density greater than the wood; in other words, starting from the same woody raw material, the same amount of energy is contained in a smaller volume in the briquettes than in the firewood and this can be an important element when storage volumes are considered.

Furthermore, the supply channels, similar to those of pellets, make easier the availability; in fact, the briquettes can be purchased or directly from producers, dealers and distributors specialized in the sale of woody biofuels and heating systems or be from retailers of agricultural materials and large-scale distribution, in 10 and 20 kg packs with a cost that, according to a survey carried out by the Laboratorio Analisi Biocombustibili of the Dept.TESAF, is approximately 270 € / t.