Speaking of biomass heating,we have several possible heat sources (fuels): firewood, briquettes, pellets, wood chips and hazel wood.
Despite a lot of misinformation that is circulating, these sources are cheaper, more efficient and green than methane and oil derivatives, which however remain the most currently used.
If you are wondering how to switch to biomass heating for your home or business, we recommend that you also read the in-depth article on pellets, so that you can consciously choose the right product for your specific needs.
It deals with all these issues Progetto Fuoco, the most important world event in the sector of energy production through wood and derivatives. An exhibition where there is a lot of information and which are present the major world producers of both biomass and technologies for their exploitation.
If you are interested in deepening the topic, Progetto Fuoco is also curator of PF Magazine, the first Italian magazine dedicated to the sector. Look for it in retailers, hardware stores, showrooms and large retailers.
But now let’s find out all there is to know about wood.
Devices
The first question to ask is: what do I use to burn wood?
The market offers us two families of solutions: the wood stove and the wood fireplace. There are several variations of both.
Wood burning fireplace
The wood-burning fireplaces can be of different types, which belong to four variants.
Open fireplace: the stereotype of the fireplace, aesthetically very beautiful but disperses the heat unevenly.
Open ventilated fireplace: saves aesthetics and is equipped with a ventilation system for the most efficient distribution of heat in the environment.
Closed or closed and ventilated fireplace: designed for energy efficiency, closed-structure combustion is safer, avoids smoke problems inside the home.
Heating Fireplaces: closed fireplaces that also implement a water heating circuit.
We do not currently deal with bioethanol fireplaces, which as we have seen are less efficient, more expensive and much less green.
Wood stove
Wood stoves are a more versatile solution. They can be easily installed even in rooms that are not structurally suitable for a fireplace. All you need is a connection to the chimney already present in the house.
Here too we have different types.
Wood stoves with oven: normal wood stoves with a dedicated oven compartment whose temperature cannot be regulated, however.
Cast iron stoves: normal wood stoves but with external cast iron walls, to better conduct heat. They are smaller in size but quickly cool down when turned off.
Ventilated wood stoves: these are the stoves we see most often on the market, they release hot air into the room from grills at the cost of a little ventilation noise.
Accumulation stoves: in masonry, with great heat storage capacity that is released from the walls for a long time into the environment. Much more expensive than steel stoves, but the investment is largely rewarded by the fuel savings.
Wood-burning thermo-stoves: like thermo-fireplaces, also thermo-stoves have a circuit for heating water, and are often associated with an accumulator to optimize the yield.
Clarified the different types of tools in which you can use wood, let’s talk specifically about the different types of wood and how to choose the right wood for your needs.
Types, characteristics and benefits
The first thing to explain when talking about firewood is the concept of calorific value.
The calorific value of a fuel is the maximum amount of heat it can produce.
Let’s say immediately that, with the same weight and water content all types of wood have a similar calorific value. There is not one that makes significantly more than another from this point of view even if the differences between wood and wood are there and we will see them in the next paragraphs.
The issue of water content is very relevant for biomass yield purposes, which is nothing but the amount of water still present in the wood. The higher this value, the more the calorific value of the wood drops. This is because part of the energy that wood can potentially produce is used to evaporate water instead of heating the environment.
In general, freshly cut wood has a water content of even more than 50% of its weight but is considered ideal for combustion when this value falls below 20%.
Furthermore, the higher the percentage of water content and the higher the emissions of fine particles (PM10). To give indicative data, just think that going down from 30% to 20% of residual humidity in the wood, during combustion the emissions drop from 1144 mg/Nm3 a 69 mg/Nm3 and the calorific value instead rises from 3.39 MWh / Ta 3.97 MWh / t (+ 17.5%).
Formats
Now let’s see the formats in which you can buy and use firewood.
As anticipated in the opening, the main sizes of firewood are, by decreasing size: logs, briquettes, wood chips and hazel wood.
Olive pomace oil, is produced from the waste from the processing of the olives, which are pressed in a similar way to the pellet but with dimensions more similar to those of the wood chips. The olive pomace has several advantages, first of all the drop power first of all the calorific value that oscillates between 6.2 and 7.4 kWh per kilogram (the pellet, for example, settles on average around 4.4). It is also very convenient to store and pack and it is biomass that produces the lowest environmental impact ever.
The wood chips are reduced to flakes ranging from a few millimeters up to 5-6 centimeters and are produced from agricultural and forestry waste. It has a calorific value ranging from 3 to 3.6 kWh per kilogram on average in A1 and A2 quality types.
It is particularly suitable in medium-large boilers of at least 40kW, and in boilers for the combined production of thermal and electrical energy. It is the cheapest source of biomass and for this reason it is most often used in the industrial sector. It is also generally uncomfortable for home use, where briquettes and logs are preferable.
The briquettes (or logs) are untreated wood waste pressed in a cylindrical shape. Products mostly from wood chips. They can be used like logs, but they burn more like coal, with low flames. The advantage is that for the same volume they guarantee a higher calorific value (up to 4.8 kWh) and do not give problems of water residue and therefore not even emissions. Comfortable for those who have little storage space and have no aesthetic needs.
The logs are the classic pieces of logs or branches that we are used to imagining in the fireplace. They can vary in size from 20 to 40 centimeters for stove wood, while for fireplace wood it can go up to 50 centimeters.
Always pay attention to the diameter of the logs, which should never exceed 20cm. The ideal size is between 10 and 15 centimeters because too thick pieces do not lose moisture homogeneously, with all the problems already mentioned.
Charcoal must also be mentioned, which despite having a very high calorific value follows very different processes and logics from those seen for firewood and is not used in fireplaces or wood stoves.
Is pellets or wood better?
Here too, it depends. Both of these wood fuels have pros and cons.
The main advantage of wood is that it costs much less. If quality wood is used in certified plants, the economic and ecological savings are considerable. We are talking about 450 euros of wood against 650 euros of pellets for heating a standard house of about 60m2 which requires about 10 MW / h of energy.
On the other hand, however, the pellet is more comfortable to manage, less bulky, easier to store and does not require long curing times. Not to mention the fact that it is now possible to buy retail throughout the GDO.
As always, the choice must be made on the basis of the specific situation. For an apartment without a garage or warehouse, perhaps pellets are more practical. For a villa with a large shed to be used as a woodshed, wood is intuitively more suitable.
Types of firewood
Wood is divided into two large families: sweet wood and strong wood.
As you will have understood by now, there is no right and wrong answer to the question “which wood to use?”. The choice of one or the other depends primarily on your needs.
Always remember, however, that wood must always have a water content of less than 20% to be suitable for combustion, regardless of the type.
Sweet wood (or soft or medium) is generally lighter (300-350kg per cubic meter), is easier to ignite and is characterized by the production of a very long and aesthetically more pleasant flame. For this reason, sweet wood burns faster than hard wood, producing an immediate but short-lasting heat peak.
For these characteristics, this wood is more suitable for those with design and aesthetic goals.
Sweet wood is, for example, that of fir, chestnut, alder, pine, poplar and willow.
On the contrary strong (or hard) wood is heavier (350-400kg per cubic meter), it burns much more slowly and with lower flames, therefore also for a longer duration of time. It is therefore the most suitable type for domestic heating as it allows substantial economic savings.
The strong wood is, for example, that of red maple, white hornbeam, black hornbeam, cherry, beech, ash, holm oak, walnut, elm, oak, oak and olive.
Usage tips
We now summarize the good habits regarding the use of firewood.
For heating, choose strong woods.
For the design, prefer soft woods.
Do not accumulate large quantities of wood all together in the fireplace or stove.
Initially, light the wood and let it burn until it forms a ‘bed of embers’ on the bottom of the fireplace. Then add individual logs above it for a more homogeneous combustion.
Always choose the size of the wood cuts carefully. For stoves use 25-33-40 cm cuts, for fireplaces larger ones (50cm) are fine.
Longer pieces burn slower than shorter ones, they are better for heating.
The ideal diameter of the logs is between 10 and 15 centimeters. Smaller ones burn too quickly and bigger ones risk having a lot of humidity inside.
Speaking of humidity, it is very important not to burn wood with water content greater than 20%, it reduces the calorific value and increases both CO2 and particulate emissions and the risk of problems to the plant.
How to choose firewood
Here we are finally at one of the longest-running questions: how to choose firewood?
We have already said that to really achieve savings and efficiency, there is no choice but to start with quality wood. The easiest way to be on the safe side is undoubtedly to rely on Biomassplus certified timber, which guarantees quality control, the supply chain, seasoning and provides us with all the useful information in this regard.
We will explore the issue of certification later.
For heating we have already said that it is better to prefer hardwood, but there are also differences between these. For durability, autonomy and homogeneity, the most suitable essences are beech, hornbeam and oak.
The problem is that not all the wood on the market is certified and we know that buyers often take risks in order to seize an opportunity that seems advantageous.
It being understood that not all non-certified woods are of low quality, let’s see together how to recognize the good ones when we are faced with firewood in pallets, loose or in bags.
Tips for choosing
As we have repeated many times now, the first aspect to check is that the water content is below 20%.
In the event that the water content is not explicitly reported, we can observe two things: the color and the weight.
Leaking water, the wood tends to darken, so paying attention to color is a good practice, but not sufficient and can be misleading.
The weight assessment is more reliable. During drying, the wood also loses more than 30% of its weight in water, so with the same volume, the lighter the water content is.
For this reason we should only choose wood that has been dried for at least one season and up to two, depending on the type of wood.
Buy by volume and not by weight, otherwise for wood that is not well dried you risk paying for water which will still have to be lost.
Another aspect to consider is the size of the combustion chamber of our stove: do not take too long wood, or you will have to further cut it before using it.
Speaking of size, thickness is also important, the closer it is to 10 cm, the better.
Try to avoid whole rods, wood when split into wedges has two advantages: a greater surface area corresponds to greater yield, and the splits facilitate the passage of air inside, facilitating combustion.
Last but very important point: absolutely take the utmost care never to buy painted wood or that has been chemically treated (for example, old railway sleepers), during combustion they release a lot of soot and chemical agents with risks for our health, for The environment and not least for the system.
Certification
The only certification useful in Italy to guarantee the quality of firewood, wood chips and briquettes is Biomassplus®. Conceived by AIEL (Italian Association of Agroforestry Energy) and ENAMA (National Organization for Agricultural Mechanization) on the ISO 17225 standard, it is an information and training partner of Progetto Fuoco.
Biomassplus certifies 3 things: product and process quality, environmental sustainability, traceability and legality.
Among the checks on the companies, the infrastructure checks to ensure that they can provide quality products all year round, the checks on the drying, packaging and transport processes and above all the periodic quality control checks.
4 levels of certifiable quality: A1 +, A1, A2 and B, each with its own technical and specific characteristics that you can find on the official AIEL website https://www.aielenergia.it/formazione_certificazioni.php
Traceability
Now that we have learned to recognize quality wood, let’s see now where and how it can be purchased.
The first thing to check is whether you are a private individual or a company and how much wood you need.
The market laws that we all know apply: buying large quantities lowers the price, buying in advance lowers the price, buying from geographically close sources lowers the price because transport costs are reduced.
If you are a company with important needs, the advice we give is always to directly contact a producer close to you and negotiate the price and type of raw material and transport, based on the needs of your plant. If possible, always choose certified products, it is difficult to check quality firsthand when it comes to large quantities.
If, on the other hand, you are a private individual, the advice we give is first of all to check if there are already purchasing groups in your area, in order to associate with other private individuals and enjoy advantageous prices and bargaining power.
For purchases of large quantities, auctions can also be considered, in which entire lots are typically offered for sale, but it is a procedure that we do not recommend to non-experts because problems and unexpected events are always lurking.
A factor to consider is whether or not you have a suitable storage space: a covered and well-ventilated place to leave the wood detached from the ground and walls. In the event of a positive response, the advice for those who can afford it is to buy the wood well in advance, typically in spring and summer, when prices are lower.
In this way you can also take a wood with a higher water content, going to save further. It will then be left to mature for 3-6 months to complete the drying process within the winter.
The situation is different if you are used to obtaining firewood yourself. In this case you must have a lot of space to use for the seasoning process and always be sure that the wood is well dried before burning it.
A tip we give is to cut deciduous plants (not evergreens) during the winter months to prevent them from being full of lymph.
As the times progress, the purchase of wood online is increasingly frequent. We would like to specify that there is nothing wrong with these channels, but they have the drawback that it is almost never possible to personally verify the quality of the raw material. We therefore urge the purchase of certified products only to avoid nasty surprises.
The last sales channel are the specialized shops and the large-scale retail trade. This solution is very convenient especially for individuals who do not have much storage space. In these shops we can find wood in pallets, in bulk or in bags, with the availability of all the best known essences and always available in constant quality. But we have to come to terms with higher prices.
Prices
Speaking of thecost of firewood the premise is that comparisons are always made on the price per quintal.
As a general indication, consider a mixed wood pallet, by definition less valuable and therefore cheaper. Here the prices are around 10-12 euros per quintal in fireplace cuts (40-50cm) and rise to 12-13 euros per quintal in stove stoves (20-33cm).
If you want to go on hard wood of only one type, the price should fluctuate between 15 and 20 euros per quintal, depending on the time of year and the specific type of wood.
As for the price of the wood chips, it is valued by the meter (about 5-6 quintals of dried wood chips) and settles on the 28-30 euros, therefore a significantly lower cost compared to wood and pellets, but we already had it He said. The price may then vary based on the transport and quality of wood, but this figure is a good reference point.
The price of wood briquettes is more in line with that of firewood, on average it settles on 25-30 euros per quintal even in retail. If compared to its calorific value, it is a very interesting solution.
Be careful, especially online the cost of firewood is very variable. The marketplaces apply commissions, to which is added the cost of transport to our home. At the end there is beech firewood at prices even over 50 euros per quintal.
The situation for firewood is not very different.
It goes a little better with the price of oak wood which is also found at 25-30 euros per quintal on the fireplace cut.
As you can see, they are all quite high prices, for this reason our advice is always to buy as much as possible at zero kilometer.
Conclusion
We hope to have given you all the information you were looking for, now it’s up to you to assess whether the time has come to switch to wood biomass heating or not.
When doing so, always remember to add the various state incentives available to your assessments: the so-called thermal account.