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Pellet stoves, boilers and other pellet burners are becoming more and more popular to generate heat and energy for homes and businesses. So how do they work and why are pellets the ideal fuel for these automatic systems. Most pellet stoves, boiler and burners operate on a hopper system, which feeds a burn pot.

The pellets in the hopper are fed to the burn pot via an auger system. The auger system will be variable speed. The variable speed on the auger system is important to regulate temperature, and for adjustments on the different types of pellets. The feed time will increase for higher desired temperatures. In many systems the auger will feed the burn pot every 30 seconds, how many seconds it feeds for is what can be adjusted to get more or less heat. The auger speed and timing also needs to be adjusted as not all pellets burn the same and generate the same amount of heat. Some pellets are denser and contain more energy; these pellets will be feed slower and less often into the burn pot than fast burning low energy pellets.

The objective is obviously to generate a set room temperature, and so the stove must be flexible enough to reach that temperature with a range of different pellets. Most pellet stoves are controlled via a wall thermostat, and the stove will monitor its own temperature, actual and desired room temperature to make the necessary adjustments, for example auger feed rate and timing. Today some stoves can even be started by mobile phone. The owner on their way home can send a txt message to the stove and it will start up. The property is up to temperature when the owner gets home.

Why are pellets the right fuel for stoves and automatic feed systems? The reasons are based around several qualities pellets have. Firstly pellets flow like a liquid, and so are ideal for hopper and auger feed systems. They have a uniform size and shape and so are less likely to cause issues in the auger. Wood chip boilers tend to have issues with oddly shaped chips every so often, which can block the auger. The second reason is pellets have a much higher density than unprocessed biomass such as wood chips, and increased density means increased combustion efficiency. Finally pellets have very low moisture content, generally below 10%, compared to between 30-50% for wood chip. Combustion efficiency is also achieved through low fuel moisture content. To summarise the features of pellets, it is their standardised form and features, which makes them more efficient, predictable and reliable in burning equipment. The small size, high energy content of pellets also means pellet burners can be a lot smaller than other types of biomass burners such as wood chip burners.

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It is important to understand that not all pellet boilers and stoves are equal in their abilities, and not all wood pellets are the same quality. Wood pellets range in quality depending on several factors. These factors range from the raw material used, the density of the wood pellets, the moisture content of the pellets and percentage of fines. Many countries have brought in quality standards, however there still seems to be quite a different range of wood pellets made to higher standards than others. It’s important to understand what are quality pellets and which pellets are of a lower quality to understand if it is a good price or not. It is also important to understand the qualities of the wood pellets to know if your stove or boiler will successfully burn the pellets. Some pellet stoves and boilers because of the burn pot design have limited abilities to cope with increased ash contents and the possibility of clinker formations. The air fan in many stoves provides the only means of ash removal to the ashbin. The air injected over the fire to fuel it, is the same air, which removes the ash. However when the pellets have higher ash content, this fan does not remove sufficient ash. This means after several hours the ash has built up and will start to effect combustion of the pellets. Poor combustion will result in less heat produced and lower efficiency. Many stoves will notice there is an issue with the stove and shutdown. If possible it is always better to choose a stove or boiler, which can handle higher ash fuels.

Wood pellets will have higher ash content if the wood contains bark, or is supplemented with materials such as cardboard and paper. Also fast growing wood species such as willow will also have a higher ash content than many softwood and hardwood pellets. With regards to moisture in the pellets, you should check they have moisture content below 10%, and ideally between 5-8% to get the best efficiency. Fines are particles, which have either come from the pellets or were not formed into pellets in the production process. Look for pellets with a low fines percentage as fines can cause issues with the auger feed mechanism is some stoves and boilers.

Before purchasing tonnes of wood pellets, purchase a few bags for testing first. This may cost slightly more, however it will save money in the long run. To reduce the carbon footprint of your fuel pellets, try to source local wood pellets if possible. Transportation of pellets is reducing their green credentials. The more transportation the more carbon released into the atmosphere.

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As a cheap renewable green energy, the popularity of premium wood pellets is growing all over the world. Very little ash is produced from burning the pellets. Premium wood pellets also have very low moisture content. The combination of a low ash and moisture content means premium wood pellets produce more heat and less maintenance. The heat and efficiency gained from pellet stoves and boilers can be as high as 99% efficient. The ashbin only needs to be emptied every few days at the most, and the pellets have an ash content below 1%. Some pellet stoves and boilers can operate for week’s even months without the need to empty the ashbin. Premium wood pellets are made from both softwood and hardwood waste and by-products from the wood industry. Most if not all bark is removed from the wood to achieve the very low ash content when burnt. The best fuel pellets are definitely premium wood pellets, there are future issues with them though.

We need to move away from fossil fuels as with our rate of consumption, current rates of supply are not sustainable. Unlike fossil fuels we can grow softwoods and hardwoods, and so we can replenish resources. However the rate of growth for hardwoods and softwood trees used for pellet production is not sufficient to sustain current demand, and definitely not enough to sustain future demand. Premium wood pellets are made from waste from the wood industry, and there is only so much waste. So once all wood waste resources are allocated, are we going to cut down hardwood and softwood trees for premium pellet production? Using softwood and hardwood trees for pellet production is waste of precious assets.

For this reason, we need to look at other biomass resources for fuel pellet production. This could be in the form of wood pellets made from willow and other fast growing wood species. It could include fuel pellets made from agricultural food crop waste, for example corncobs, wheat and barley straw. This way from growing food crops, you could obtain both food and fuel and the two are never in competition with each other. They actually complement each other and would encourage more food crops to be grown, which would produce more food and green renewable fuels. Hemp is an amazing crop; it can used to produce food, clothes, plastics, oils and other resources. Again the waste from Hemp processing could be used for fuel pellets. Hemp pellets do have a huge potential, as unlike straw and grass pellets, Hemp pellets are low corrosion and low ash. Normally crops which are low ash, low corrosion take a long time to grow (softwoods/hardwoods) however Hemp is grown from seed to harvest within a 3 month period, with massive yields. Hemps main issue is many regard it as cannabis, even though they are not the same plant. Quotes have been made that you could smoke a field of hemp, and not feel any effects.

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A relatively new form of renewable energy are fuel pellets. Traditionally pellets were just used for animal feed. Feed pellets and fuel pellets are similar in many ways. Both fuel pellet and feed pellets are made from a compressed milled raw material. Fuel pellets can be made from different raw materials; collectively these materials are referred to as biomass. There are many different types of biomass pellets, for example biomass pellets could be made from straw, such as barley straw and wheat straw. Many grasses are also being considered for biomass fuel pellets, this includes reed canary grass and switchgrass. Another biomass material which has a good potential for pellets is Hemp. Hemp pellets produce very little ash, almost equal to that of premium wood pellets.

Wood pellets of a certain standard are referred to as premium wood pellets. Premium wood pellets are the most popular type of wood pellet used in the US and Europe. Both hardwoods and softwoods are used in the production of premium wood pellets. Usually the pellets are made from the waste of wood processing. So it is common for wood pellet plants to be setup next to sawmills. For example Canada has very little premium wood pellet consumption, however their premium wood pellet production is as high as Sweden, the worlds largest user and producer of premium wood pellets. The wood used must have certain qualities for it to be used for premium wood pellets. The wood must produce a very low ash content, generally below 0.5%. For a premium wood pellet to produce so little ash the raw material must contain very little or no bark. The moisture content of a premium wood pellet must also be very low, this generally means below 10%, however many premium wood pellets are much lower. The density of a premium wood pellet is also very important. It must hold together well, and break cleanly producing few fines. Fines, which are pellet dust, must also be kept below a certain level. Excessive fines can cause issues with the auger system in the pellet stove or boiler, and also combustion efficiency is reduced meaning less heat and more ash is produced.

The advantages of premium wood pellets are when burning and maintenance. The high density and very low moisture content of the premium wood pellet means a very high efficiency burn. Some wood pellet stoves are rated a being 99% efficient. Efficiency of 99% is much higher than many oil and gas stoves and boilers operating today. The low ash content means the user will only have to clean the stove and empty the ashbin at most every few days. Some pellet stoves and boilers have very large ashbins and some have ash compression systems. This means that some pellet stoves and boilers can run for weeks and even months without the need for the owners attention.

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So what are pellets and briquettes and what are the differences? Well essentially pellets and briquettes are one and the same apart from one is generally bigger than the other. Both pellets and briquettes are formed through compression of the raw material in to a cylinder. Pellets tend to be small, ranging from a diameter of a few millimetres up to say 20mm. Briquettes on the other hand have a larger diameter from 20mm upwards, and resemble a wooden log. Pellets have a solid centre, and some briquettes have a solid centre and some have a hole in the centre. Some believe that a briquette with a hole in the centre burns more efficiently, and more complete combustion is achieved. However having a hole in the centre means for the same weight of fuel more briquettes are needed, which is unappealing to some as this means higher transportation costs. I’m sure this issue will be discussed more in the future to decide which feature is the most significant in terms of good combustion and reduced transport costs.

So what are the key advantages and disadvantages for choosing between pellets and briquettes? The advantages of pellets are they flow liquid a liquid, therefore they are ideal for automatic feed system. This means a very low level of maintenance can be used even with a solid fuel. Automatic feed systems can be placed in a very small form factor even a small stove. You simply have to make sure the stoves hopper has enough fuel and it will feed its self. Depending on the stove and the size of the hopper, it could run for several hours’ even days. Briquettes on the other hand will have to be loaded by hand into the fire like logs; this means there is more maintenance involved. Briquettes are more suited to open fires than pellets, and so makes them ideal for developing countries for use in cooking stoves. Pellets and briquettes both have the same issues, how exposure to water can make them useless. Both pellets and briquettes need to be protected from moisture or they will absorb the moisture and disintegrate.

For automatic systems pellets are more suitable, and for cooking stoves briquettes are more suitable. It will be easier to convince the western world to choose pellets, as it is a more suitable choice. Systems can be designed to replicate the convenience of today’s oil and gas boilers, and even small stoves can be low cost and low management. To move the western world onto carbon neutral fuels, the changes in lifestyle must appear small, however their affect will be significant in reducing global warming.

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Fuel pellets are becoming more and more popular. Due to the need to move away from conventional fossil fuels such as oil and gas for cost, political and environmental reasons. Pellets give similar levels of convenience to their fossil fuel cousins, however are much kinder to the environment and cost less. Pellets flow like a liquid, and are therefore ideal for hopper fed systems. Similar to how for an oil boiler you would have an oil tank, for a pellet boiler you have a pellet tank. Relatively little processing is required to convert wood into wood pellets compared to producing bio-diesel for example. The reduction in processing means less time and energy is needed in production, which is why its cheaper and better for the environment.

Before you can turn your raw material into pellets you must prepare it accordingly. ]Firstly the material needs to be in small particles ready for the pellet mill. This may involve processing the material through a hammer mill or grinder. You must make the raw material smaller than the diameter of pellet you intend to produce. ]So if you wish to make a 6mm pellet, your raw material needs to be smaller than 6mm. Also it is only possible to make pellets when the raw material is relatively dry, so the raw material may also need to be dried before going into the pellet mill.

So how are pellets made, well to put it simply it involves a lot of heat and pressure, as you would expect. The key part of the process happens in the pellet mill or pellet press. The pellet mill contains a die and rollers, put simply the material enters the pellet mill and the rollers compress the material against the surface of the die. The material then begins to get compressed through the holes in the die. Through this compression heat is generated, which begins to melt the material. This melting is what helps the material bind together, by melting a natural sugar found in all biomass material called lignin. The lignin begins to melt as the pellet mill gets up to tempreture. If proper material and lignin melting has taken place the pellet should emerge from the pellet mill with a smooth surface shine. However the pellet is still soft at this point. As the pellet cools the lignin solidifies and then forms a strong durable pellet.

Once you have your strong durable pellets you must protect them from moisture. If moisture comes into contact with the pellets, they will begin the break apart, these pellets will now not burn. So protecting your pellets from moisture is very important to keep them in top condition. Dry pellets will reward you with more heat when they are burnt, and cause less issues with your pellet stove/boiler.

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Wood pellet are a compressed form of the original raw material. Collectively the raw material is called biomass. Biomass can take many forms, for example one form of biomass is . By compressing the material into pellet creates a uniform highly compressed commodity. This commodity can be used for several purposes, for example they can be burnt to produce energy in the form of heat or used for animal bedding.

The reasons for turning the raw material into pellet is quite simple. In its raw form the biomass has a low density and is very expensive to transport. pellets can drastically reduce the foot space of the raw material. This means more of the raw material can be placed on the back of a lorry or on a boat. This means reduced transport costs, however there is another advantage. Pellets are seen as a environmentally friendly fuel and kind to the environment because of several reasons and one main reason is it takes less lorries and boats to transport pellets from one location to another. This means less CO2 is produced, which helps to reduce the rate of global warming.

Secondly in its raw state most wood is awkward to handle and use. For example wood log stoves are very common, however the user has to manually load the stove every few hours. By turning wood into pellets the user can load a hopper and the stove will feed its self. Depending on the size of the wood pellet hopper the user may have to fill the hopper every day up to once a year. Therefore tuning the raw material into pellets gives a similar level of convenience users today expect and receive from gas and oil appliances.

Pellets are produced under vast amounts of pressure and heat. The biomass enters a machine called a pellet press and under pressure and heat is turned into a pellet. The raw material is effectively melted and reformed. The pellets come out of the machine very hot, and cannot be used until they have cooled. Once the pellet has cooled it resembles a coloring crayon, they are normally about 1 inch in length and should have a surface shine. As pellets are a lot denser they weigh a lot more. Due to the weight and uniform size they flow like water. This ability to flow means they are ideal for hoppers and feed systems for pellet burners. The uncompressed raw material would simply bridge in a feed hopper and cause lots of problems.

Pellets burn a lot better than the unprocessed raw material. Due to the high density of the pellet, a more complete burn is achieved. This means more heat, efficiency and fewer particulates and emissions. Keeping emissions and particulates as low as possible benefits air quality and the environment.

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Reducing the effects of global warming are one of the reason wood pellets and other fuel pellets are becoming more popular, environmentally friendly energy to replace the use of fossil fuels such as oil and gas. Other reason is to move away from the large energy companies, who control the market price of energy. There are also political reasons to move away from the use of fossil fuels.The opportunity that biomass and pellets bring to us is the opportunity to set-up a new energy economy that is locally based. Locally, referring to each country produces its own energy demands through the use of its own biomass resources. This could be on a national scale, even down to a local community scale. There are several advantages to this system, and here are the two main positive aspects. Energy price fluctuations would be reduced, as energy would be made from several resources and from several locations. As more resources are used there would be more market competition, which would keep prices competitive nation wide. Keeping energy prices stable is one of the most important factors of a stable economy, as it affects remaining consumable income, which many industries rely on.

Increased local jobs and economic support are some of the benefits of increased production on a national and local scale, which in current times of economic depression these jobs are in great demand. Jobs based in the energy sector are generally more secure than other industrial sectors, as we always need energy.

With local energy production another cost to energy is also greatly reduced, and this is the cost of transportation. By using local resources, processing local resources locally and consuming those local resources local, the whole loop has reduced transportation. Reducing transportation costs has benefits for the environment as well as reducing the costs to the consumer. Reduced transportation means reduced CO2 emissions. After all one of the main aspects of biomass and renewable fuels is to reduce CO2, so excessive transportation would contradict one the key principles of green renewable energy sources.

Using local resources to be processed into fuel locally, for example in the form of pellets then consumed locally is where a large part of each nations energy supply needs to come from to support stable energy prices and support the reduction of carbon dioxide levels and global warming. Reduced transportation CO2 and costs are one of the main benefits, as obviously this would also reduce congestion as the global population grows. One of the simplest forms of local renewable energy production is small-scale local pellet production.Fuel transportation would be kept as minimum as possible and the local economy would see several benefits.

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