While fuel pellets are the primary market for wood pellets there are other uses. Most notably there is also the horse bedding market and BBQ wood pellets. However, there is another wood pellet niche that even I was unaware of until recently. It’s using wood pellets as a growing medium for mushrooms! The first video below provides a good introduction on the benefits of using wood pellets as a mushroom medium when compared to other materials such as straw.

The Advantages of Wood Pellets for Growing Mushrooms

As explained in the video, wood pellets require much less energy/cost to prepare the material for growing mushrooms. In comparision let’s say you were using straw as your mushroom growing medium, which is very common. Well, there will be a lot of other bacteria growing within that straw. You first need to kill that bacteria and rogue fungi before you can try and grow the mushrooms you desire.

Therefore that means you need to produce boiling water to sterilize the straw, wood shavings etc. Wood pellets are created under very high temperatures in the pellet mill. Furthermore, once the wood pellets are formed and cooled their high density means it’s very difficult for bacteria and fungi to penetrate into the wood pellets.

Therefore wood pellets are a sterile growing medium for mushrooms. So you can then just add clean cold water to prepare the material before introducing the mushrooms/fungi. Wood pellets are also apparently very flexible for growing Oyster mushrooms, Shiitake and Reishi.

Softwood or Hardwood Pellets?

After watching quite a videos and articles on using wood pellets for growing mushrooms I did start to notice a trend. There was a clear emphasis on using hardwood pellets and not softwood pellets. Now, most wood pellets are actually made from softwoods such as pine. Therefore I wanted to research a little bit more on why softwood pellets may not be suitable for growing mushrooms.

Well, apparently pine has anti-fungal properties, so that’s obviously not ideal if you’re trying to grow mushrooms! Some articles stated it’s not impossible to ground mushrooms with softwood pellets, but the yields will certainly be affected.

How to Prepare Wood Pellets for Growing Mushrooms

So, after I became aware of the benefits of wood pellets as a growing medium for mushrooms I wanted to look more into the process. I became curious about what methods are used to prepare the wood pellets. I then came across the video below which is a great little DIY setup which shows how to do it:

The process shown in the video uses a standard 40lb bag of wood pellets, so is an easy process to replicate. The creator of the video has made themselves a very handy barrel tumble mixer. First, the full 40lb bag of wood pellets is emptied into the drum, followed by roughly 5 gallons of water. The operator then lightly mixes the wood pellets and water, leaves for around 20 minutes and repeats the process.

Adding in the Mushroom Spawn

The wood pellets will have absorbed the water, hence why wood pellets make such a good horse bedding product. At this point, you are ready to add in the mushroom spawn. The operator then rotates the drum mixer around 20 times. The mixture is then unloaded onto a DIY bag filling area.

Loading into Plastic Bags

The mushroom growing medium is then loaded (quite tightly) into some tall/thin plastic bags. Clearly, the advantage is that there is a larger surface area for the mushrooms to appear from. Once the bags are tightly packed and tied off, holes are then made 5-6 inches apart. This is done in three rows across the surface of the bags. The bags are then placed in a cool environment (60-70F) for 2-3 weeks for the mushrooms to form.

Conclusions on Wood Pellets as a Growing Medium for Mushrooms

Before writing this post I thought I knew pretty much all the uses there were for wood pellets. However, using wood pellets to grow mushrooms even took me by surprise. The real benefit of wood pellets for growing mushrooms is that they are sterile. Therefore the success rate and yields for growing mushrooms increases. I’m now quite interested in buying a mushroom starter kit and giving it a go myself. I’m a fan of a nice tasty mushroom, but this is the first time I’ve ever thought of growing my own!

Moving around wood pellets in bags can take some time and for some people with limited mobility its simply not an option. In most places, you can have loose deliveries where the wood pellets are blown into some form of silo or store. But then you have to move the wood pellets from that silo to your wood pellet stove or boiler. Now, you could do it ‘old school’ like me with a bucket and shovel. However, in the 21st centry, most people are looking for something more automated. Therefore that’s where wood pellet vacuum systems come in.

The average 5 kW pellet stove will use around 1-3 tons of wood pellet fuel per year. This is a volume that for most people is not too much trouble to lift into the stove by hand with bags. However, pellet boilers generally start at 15 kW. For instance, our 25 kW pellet boiler consumes around 7 tonnes of wood pellets in a heating season. When it comes to these sorts of volumes many people look towards hoppers and silos to hold the wood pellets. Therefore more automated methods to get those wood pellets into the pellet boiler hopper.

Alternatives to Wood Pellet Vacuum Systems

The first alternative method is fixed augers. However, in many instances, this is not an easy retrofit and can also be very expensive. There are also flexible augers, these are easier to retrofit but are not as reliable as fixed augers. Also, flexible augers have their limitations due to length and getting around sharp angles. Therefore, that’s why in many cases wood pellet vacuum systems are a better fit. They are simpler, less expensive and can deal with long runs and changes in angles.

Below we are going to look at two wood pellet vacuum solutions. The first is an off-the-shelf product produced by Triotec and the second is an impressive DIY pellet vacuum build from the US.

Off-the-Shelf Triotec Wood Pellet Vacuum

The wood pellet vacuum system shown in the video above is the PIV 3 from Triotec. The PIV 3 is described as a compact and flexible solution for homes and production facilities. There are several components to the system which I’ll discuss below in reference to the image below:

How the PIV 3 Wood Pellet Vacuum System Works

The wood pellets are pulled through the hose at the base of the wood pellet hopper. The wood pellets are then carried up the cyclone separator. You will also notice a pipe which exits the top of the wood pellet hopper. This pipe is to let air into the hopper when the fan starts. Without this pipe, the wood pellet vacuum wouldn’t work.

The Cyclone Separator

A vacuum is generated within the cyclone by the separate fan. The wood pellets fall out of the air stream and into the base of the cyclone separator. An automated gate valve then opens to let the wood pellets out. A small motor and auger then collect the wood pellets and drop them through the short hose. The short hose will feed into the hopper of the pellet stove or boiler. Hence the cyclone separator will also have to be mounted over the pellet stove/boilers hopper.

The Fines (Dust) Bin

The air and fines (wood dust) are then pulled from the cyclone and separated again. The fines are deposited in the metal drum and the air will leave (via a filter) from the top of the fan unit. How quick the fines bin fills up will depend on two factors. Firstly, the grade of wood pellets purchased and how gently the wood pellet delivery driver off-loaded the pellets.

Reducing the amount of Fines

You see on a loose wood pellet delivery the driver can control the fan speed. A quicker fan speed will deposit the wood pellets into the hopper more quickly, however, it’s also more likely to break the wood pellets and create fines. Delivery drivers are sometimes in a rush to get to their next delivery. Therefore if possible try to supervise you wood pellet deliveries and monitor the condition of the wood pellets. If you see large volumes of fines dust, ask them to lower the pressure.

DIY Wood Pellet Vacuum System

As you can see from the PIV wood pellet vacuum system above, the process is actually very simple. You just need a fan with enough power to carry the wood pellets in an air stream. You also then need to be separate the fines and air. Otherwise, every time you use a wood pellet vacuum system you would be surrounded in clouds of dust.

Below is a pretty impressive DIY wood pellet vacuum set up from the US. This particular wood pellet vacuum system has been designed so bags of wood pellets do not need to be carried from the basement where they are stored up the house.

Dust Explosions need to be taken Seriously

As stated in the video if you are tempted to build your own DIY wood pellet vacuum system you need to take dust explosions seriously. If you do a quick bit of research on dust explosions, you will see why it needs to be taken seriously. Static charge can be built up as the wood pellet travel through the pipework. Therefore all wood pellet vacuum systems need to be properly earthed so sparks from static electricity build up are not an issue.

How to Improve the DIY Wood Pellet Vacuum System

First off, I want to congratulate the individual who built this wood pellet vacuum system, it’s a project I would also be proud of. However, from watching the video there is improvements which could be made.

As the wood pellets enter the hopper located upstairs in the property they are impacting against a hard surface. This is increasing the percentage of fines produced.

The first improvements to be made are to fit a rubber matt against the side of the hopper. This will reduce the impact on the wood pellets, reducing fines. Secondly, a cyclone separator could be used instead of a basic filter. Currently, the fines are not removed from the hopper. So these dusty wood pellets will also be loaded into the pellet stove. For some pellet stoves, wood pellets with a higher percentage of fines can lead to various issues, including clinker formations.

Quick Note on the Pellet Mole

In both of the wood pellet vacuum examples above the wood pellets are sucked from the bottom of the hopper. However, what if you wanted to retrofit an existing wood pellet store with a vacuum system? Well, one solution to that problem is the Pellet Mole (great name for this product).

So essentially the Pellet Mole is mounted in the ceiling of the wood pellet store and its lowered into position. As the volume of wood pellet reduced the Pellet Mole follows the wood pellets down. A small motor and agitator is fitted on the end which sweeps wood pellets to the vacuum hose. The Pellet Mole still needs a fan and cyclone dust separator to operate. However, its an interesting solution on how to retrofit an existing wood pellet store for a vacuum system.

Conclusions on Wood Pellet Fuel Vacuum Systems

I personally feel that wood pellet vacuum systems are a more flexible solution for most domestic situations compared to augers. One advantage augers do have is that they don’t create additional dust. However, if a well-designed cyclone separator is used in a wood pellet vacuum system, dust shouldn’t be an issue.

If you would like to learn more about wood pellets and about how they are made please visit my homepage. I’ve got a considerable number of posts on the wood pellet production process and how wood pellets are made.

I’m interested in all aspects of wood pellets, from how wood pellets are made to how they are used. When it comes to wood pellet combustion there is the conventional pellet stove and boiler route. However, there is also a growing trend to use wood pellets in alternative combustion systems, in this case, rocket mass heaters. If your not sure what a rocket mass heater is I’ll talk more about that below. If you already understand the basic principles of rocket mass heaters, watch the video below on how rocket stoves can be designed to work more efficiently on wood pellets.

Automated vs Gravity Wood Pellet Stoves

Wood pellet heating comes in two forms. You have the highly automated pellet stoves and boilers such as the ÖkoFEN units and you also have none powered wood pellet stoves. Both interest me and are important in their own way, but for different reasons. Highly automated conventional pellet stoves and boilers serve as a transition product, to get people away from conventional oil and gas stoves and boilers.

However, improving the design of none powered/gravity stoves is really more important. In most of the world where solid fuel is burnt, there is either no electrical supply or its highly irregular. Wood is typically burnt on highly inefficient open fires or basic stoves. This not only wastes most of the wood it creates significant amounts of smoke pollution which kills hundreds of thousands of people every year.

The Benefits of Rocket Stoves

Rocket stoves and in the case of this post rocket mass heaters use only a fraction of the wood of a conventional stove. In some cases, fuel consumption can be reduced by as much as 80-90% using a rocket stove design. Therefore significant issues around deforestations for stove fuel can be reduced. Its cheaper for the consumer and considerably better for their health.

Rocket stove designs which can also use wood pellets can further help to resolve the issues stated above. Continued improvements in designs could even potentially burn biomass pellets from agricultural residues (grasses/straws). However, there are significant challenges around the increased ash content and clinker formations compared to wood pellets.

How does a Rocket Stove work?

A rocket stove is designed to run on small diameter fuel, typically small chunks/chips of wood. Wood pellets are not only small they have a high energy density. The rocket stove design is about making sure the draft of the fire chamber is as good as possible without using power-assisted fans. That is what makes rocket stoves are so interesting.

It’s amazing that rocket stoves can achieve such a high efficiency with no electrical fan forcing air into the fire. Rocket stove designs work by ensuring that air predominantly enters either through the fuel or from underneath the combustion zone. This essentially gasifies the wood and its the gas and smoke from the wood which is actually being burnt. I’ll talk more about gasification in later posts.

But what is a Rocket Mass Heater?

The rocket stove principles have improved combustion efficiency significantly over a conventional wood stove. However, a rocket mass heater can improve combustion efficiency even more. Essentially a rocket mass heater is integrated into the design of the property. The flue pipe is extended in length through the property. Then a large heat absorbing mass (typically of clay) encases the flue pipe. This mass extracts the heat and will releases it gradually over time.

Avoiding the Dangers of Creosote

As you can see from the video above about what a rocket mass heater is, one of its impressive features is how it avoids the dangers of creosote. Creosote forms from burning wood with a high moisture content or poor combustion efficiency.

As stated in the video the previous trade-off has been to insulate the chimney to avoid creosote formations, but this also wastes a lot of energy. With a rocket mass heater stove design it is the combustion chamber which is insulated. This creates a much hotter combustion zone which burns off any potential volatiles which would form creosote.

Why Rocket Mass Heaters and Wood Pellets go together

With a properly designed rocket mass heater, you can take advantage of one of the unique features of wood pellets, how they flow. As wood pellets have such a high density they flow well through hoppers, therefore it’s possible to create a none powered stove which can run for many hours with a full hopper of wood pellets.

In the first video above, you first see the design of the grate which will hold the pellets but will also let the ash through the grate so combustion is continuous. Next, you see the various feed shoot designs. The later designs improve the spread of fuel over the grate. This, in turn, will also provide a better flow of wood pellets from the hopper.

It is interesting to see how much of a difference installing and removing the restrictor plate makes. The restrictor plate provides better air direction and also encourages more air to come in below the grate. It’s also important to note that higher temperatures were recorded on the heat exchanger than with any wood previously used. This is due to the high density of the pellets and their very low moisture content.

Conclusions on using Wood Pellets with a Rocket Mass Heater

I do really like the idea of a fully designed rocket mass heater which can run on wood pellets via a gravity hopper. It would mean that a highly efficient and low maintenance off grid wood pellet heating system is possible. When I get the chance I would like to have a go at building my own rocket mass heater which runs on wood pellets. I think it would be a really rewarding project. If you would to learn more about making, burning and using wood pellets, please visit my home page for other posts.

While BBQ wood pellets are still a niche product in most places around the world, it is a growing market. Wood can add fantastic flavour to food, and in pellet form its possible to make a wood pellet grill that is as easy to use as any gas BBQ. One of the most established brands on the market is Traeger Grills. Traeger even makes their own BBQ wood pellets. Traeger also offers a BBQ Fire Pit. But what makes this product unique and what do consumers think about it?

Traeger’s Well Established Reputation

Traeger pretty much introduced the idea to the mass market of a BBQ with a pellet hopper, controlled auger feed, thermostat and electric ignition. Applying the same technology of a pellet stove to outside cooking equipment.

Traeger has gained a solid reputation for well-made pellet BBQ’s and they have recently released a new product, their version of a fire pit. As you can see from the video above the idea of a fire pit is pretty much as it sounds. Any solid wood fuel can be used in this fire pit, from pellets to chips and logs.

Is the Traeger Fire Pit a Missed Opportunity?

Fire pits are nothing new, therefore what’s strange is that the Traeger fit pit does not appear to innovate in any way. Personally I would have expected them to introduce the idea of gravity fed pellet hopper, similar to that currently used on the Wiseway pellet stove.

With a gravity fed pellet hopper Traeger would have produced a fire pit with an additional level of convenience over a standard fire pit. It would have also kept the focus on Traeger products on BBQ wood pellets.

Reactions to the Traeger Fire Pit

Some of the reactions on the YouTube comments section are from Traeger customers who are not impressed by the product or its $200 + price tag. One comment states “Looks like a good way to burn $15 worth of pellets”. It is worth noting again that Traeger produces and obviously recommends their own wood pellets.

BBQ wood pellets are a premium product, and the fit pit would consume wood pellets quite quickly. Consumes are aware of this and some appear to be taking offence at Traeger selling a product where pellet consumption would be so much higher than with their automated BBQ’s. However, according to the reviews for the Traeger fit pit currently on the Google listing, the feedback is quite positive.

Many different sources of woody biomass can be made into wood pellets. A fairly obvious source of wood waste is damaged wooden pallets used for shipping purposes. Most bulky products which are transported are done so on wooden pallets. They make it easy for folk lifts to load and unload the products. Recycling wooden pallets for making wood pellets involves several stages of raw material preparation. Skipping any of these stages can either lead to poor quality wood pellets or potentially even damage to the pellet mill.

Recycling Wooden Pallets into Wood Pellets

Overtime and after multiple uses wooden pallets get too damaged to be reused for shipping purposes. Therefore its quite understandable to look at wooden pallets as a source of raw material for making into wood pellets. They can be recycled and processed into wood pellets using either a flat die or ring die pellet mill. However, various stages of material preparation are required first. An example of suitable equipment to process wooden pallets ready for making into wood pellets is the Peterson Pallet Grinder in the video below.

The wooden pallet grinder from Peterson shown in the video above does two important jobs. First, it reduces the wood pallets into a smaller particle size. Secondly, it features a cross-belt magnet to screen the material for nails. You can watch how the cross belt magnet works in the video below:

The cross-belt magnet collects the high-grade steel nails from the shredded wood pallets and deposits the nails into a bin. As you can see from the video, after half an hour of operation there is a considerable amount of metal nails which have been collected. Remember, this waste metal has a value. According to Peterson, some of their clients are able to cover 40% of the fuel costs of the running the wood pallet grinder by selling the nails as scrap metal!

Removing ALL Metal Nails is vital to avoid Pellet Mill damage

I cannot emphasise enough how important it is to remove all metal contamination from the material before it is used in a pellet mill to make wood pellets. The pellet mill rollers and die are set up with a 1mm clearance. Therefore any stones or metal which enter the pellet mill can cause serious damage. Best case scenario the pellet mill die and rollers are scratched. Worst case scenario the metal becomes trapped between the rollers and die. The result would be either tooth on the gearbox sheering or some other drive component to fail.

From the Shredder to the Hammer Mill

Once the wood pallets have been processed via a shredder and the metal nails removed, the material then needs to be processed by a hammer mill. The shredded wood is in particles several inches long (50-100mm). Before the material can be used in the pellet mill to make wood pellets it needs to be reduced consistently to 5mm particles. Therefore the shredded wood is processed via a hammer mill with a 5mm screen fitted. Essentially, whatever size of wood pellet you wish to produce you use a screen size which is slightly smaller. So, to make 6mm wood pellets, a 5mm hammer mill screen size is used.

Metal screening is also important to protect the hammer mill. Metal entering the hammer mill may puncher the screen reducing particle size screening efficiency. It may also spark and ignite dust particles which can lead to a dust explosion.

The Benefits of Wooden Pallets and Moisture Content

Going from a chipper or shredder then on to a hammer mill is similar to the process of making wood pellets from logs. However, the big difference between logs and wood pallets is moisture content. With logs from a recently cut down tree (virgin timber), they will contain a moisture content around 50%. When it comes to making wood pellets, you want a moisture content below 15%.

So with logs, the pellet making process has to involve some form of drying process. However, wooden pallets are a source of dry timber. Therefore the drying process of a pellet making set up can often be avoided. Therefore the cost per tonne when making wood pellets from pallets is less than making wood pellets from virgin timber logs. Not only from the fact you do not need to purchase a dryer, but you also don’t have to cover the costs of running that material dryer.

Final Metal Screening before the Pellet Mill

As stated above, metal contamination can cause serious damage to the pellet mill. Therefore to be extra safe it’s sensible to fit another electromagnet on the material conveyor before it enters the pellet mill. The additional cost of this electromagnet will easily be recovered by avoiding pellet mill downtime and damage to the rollers and die.

Avoid using Wooden Pallets which have been Treated

Presuming the issue of metal contamination can be resolved there is still the issue of treated wood. As the pallets are often left outside various chemicals are sometimes used to try and preserve the wood. Wood fuel pellets with these chemicals will not pass any accredited standards and you could get in a lot of trouble for selling them.

Conclusions on Making Wood Pellets from Wooden Pallets

If the issue of metal contamination can be resolved and only nontreated wooden pellets are used it is potentially a suitable material for fuel pellets. Wooden pallets are appealing as a source of dry wood waste for wood pellet production as dry/nontreated waste wood is becoming harder and harder to source.

A question I’ve been asked many times is “can you use lawn clippings to make grass pellets for a pellet stove?”. While making lawn grass pellets is fairly simple to do even using a cheap Chinese imported flat die pellet mill as seen in the video below, it’s actually not a great idea.

While lawn grass pellets (besides being green) obviously look similar to wood pellets, they perform very differently in a pellet stove or boiler. By burning grass pellets made from lawn clippings you could even cause significant damage to your pellet stove or boiler.

The Process of Making Lawn Grass Pellets

First, let’s look at the process of using a pellet mill to turn lawn clippings into grass pellets. As seen in the video above you can get a cheap Chinese flat die pellet with a small single phase motor and quite easily produce grass pellets. In fact, lawn grass clippings is a very easy material to run through the pellet mill. It flows very well and can produce pellets to a good density with a nice surface shine.

In the video above this particular pellet mill owner is showing how he prepares his raw material. He shows how he adjusts the moisture content of the grass clippings and evaluates pellet quality. Even with a very small pellet mill as shown in the video above you can get a reasonable productivity per hour with lawn grass pellets. You will also find videos on YouTube of homemade and DIY pellet mills processing lawn clippings into grass pellets.

But whats Wrong with Burning Grass Pellets from Lawning Clippings?

Let’s presume you have purchased a cheap pellet mill and it’s all gone well. After a few hours, you now have a good amount of ‘quality’ grass pellets. You wish to use these grass pellets made from your lawn clippings in your pellet stove or boiler. However, this is where the issues really begin.

Grass Pellets and Ash Content

Grass pellets will produce around 5-7% ash when produced from lawn clippings, compared to say premium grade wood pellets at between 0.5-1% ash. Now depending on your brand and design of pellet stove or boiler, you may be able to burn grass pellets successfully. Some pellet stoves have a forced auger feed which will push the ash buildup out of the burn pot.

However, most pellet stoves use a basic drop down burn pot design that relies on the combustion fan blowing the ash out of the burn pot. The fan speed will be set up for wood pellets (1% ash), so it simply cannot deal with the ash volume from burning grass pellets.

Grass Pellets and Clinker Formations

The second issue associated with burning grass pellets is clinker formations. This is where the ash gets very hot and fuses together to form a sticky mass. Again, most pellet stoves are not going to be able to deal with clinkers.

Finally, let’s presume your stove/boiler can even deal with the ash and clinker issues, well there is a final issue and the most serious. Grass pellets during combustion produce a lot of chloride which is a high temperature corrosive. So while grass pellets may appear a cheap fuel option they can actually destroy your pellet stove in just a few years of use. The high percentage of chloride increases corrosion damage to the pellet stove significantly.

Why Making Quality Fuel Pellets is not Simple

People often see a video of making grass pellets and think that making wood pellets is also that simple. They then go ahead and purchase a cheap Chinese pellet mill. After trying to operate the pellet mill for the first time and experiencing blocked pellet mill die, they quickly learn that making wood pellets is not that simple. Issues with the die blocking, a low productivity per hour and poor pellet quality are just a few of the issues that I try to help people avoid.

Before you even consider purchasing any equipment I would encourage you to read my post on how to make wood pellets. The general principles apply to making pellets from any biomass material.

Conclusions on Grass Pellets made from Lawn Clippings

So when it comes down to it, is burning grass pellets made from lawn clippings really worth it? While a cheaper alternative to wood pellets they could seriously damage your pellet stove or boiler. Even if you are within the warranty period of the pellet stove. The manufacturer will be able to tell that you have not been using approved wood pellets to cause that type of damage. With many pellet stoves, using anything other than premium wood pellets will void its warranty. While grass pellets made from lawn clippings is not a viable alternative to wood pellets, fuel pellets made from hemp actually have a lot of potential.

There are quite a few videos on YouTube of DIY homemade pellet mill projects. Some of these DIY pellet mills are a lot more successful than others. The video below is quite a popular example and not a bad attempt at a wood pellet mill. While I respect those that put the time and effort into a DIY project to make a pellet mill the limitations of these machines is not clear to many people. The reasons being, most people don’t have the experience of how to make wood pellets. With this post below I’m not attempting to discourage anyone from attempting a homemade pellet mill if you are willing. I just want you to approach a DIY pellet mill project with realistic expectations. You need to be realistic on what a DIY pellet machine can achieve and the grade of wood pellets you will produce.

DIY Flat Die Pellet Mill Design

The first thing to note from this video is the basic vertical flow flat die pellet mill design. Material is fed through the hopper on top and the wood pellets come out from under the die. Not the most efficient pellet mill design, however, it’s very popular in China due to its simplicity. In fact, many homemade pellet mills actually use a die and rollers made in China. What is actually homemade is the chassis of the pellet mill, the gearing etc. The most efficient pellet press design is a ring die pellet mill. However, that would be much more technically demanding DIY project.

Pellet Press Power Input from a Tractor PTO

The video states that an 80HP (60kw) motor is used, as you can see to the right there is a PTO shaft so this pellet mill is running from a tractor. A lot of people are interested in PTO pellet mills, however, it’s not something I personally encourage. For one, its dangerous, many people die every year from getting caught up in PTO shafts. With a pellet mill, you are standing very close to that PTO shaft.

Even with a cover on the PTO shaft, it’s still not very safe being stood next to it. Secondly, an 80HP diesel engine is being used to power a very small pellet mill. It’s stated in the video description that this DIY pellet mill is producing 130 kg/h. I don’t believe that’s realistic, its probably around 40-50kg/h. Therefore, those wood pellets will have a very high cost per tonne.

DIY Pellet Mill Productivity

With regards to the productivity per hour of this DIY pellet mill, let’s be generous and presume it can produce 130 kg/h of wood pellets. You are having to load the material in above the pellet mill via a bucket, metering it in bit by bit. That’s a lot of hard work. Also, you cannot really be doing anything else such as bagging up the wood pellets.

With this particular DIY pellet mill, the operator also seems to be experiencing a bridging issue where the pellets are coming out of the machine. This is likely due to the high fines percentage. Fines are particles of material that were not compressed into wood pellets, they are then separated from the finished pellets and returned into the process.

DIY Pellet Mill Issues

This particular DIY pellet mill is producing quite a lot of fines. This is either down to one or two issues. The material could be too dry. If this is the case with a DIY pellet mill such as this you have no means to precisely control moisture content to address the issue. Secondly, it could be an issue with the compression ratio on the die holes, or the die is worn and needs replacement.

When we get to see the finished wood pellets at the end of the video you can see that there are very few good quality wood pellets. There is a poor consistency with some very short pellets that look to have a poor density. With a small pellet mill such as this, it would probably benefit from the use of a suitable pellet binder.

Conclusions on DIY Pellet Mills

While this DIY homemade pellet mill is a respectable attempt you should not look at a machine such as this and think that producing wood pellets at home is a viable option. When you work out the cost per tonne of wood pellets covering your time and equipment costs it just doesn’t add up.

Over the years I’ve been asked on several occasions about homemade pellet mills. As you may know from reading my post on how to make wood pellets, the process is not as straightforward as many people make out. Those people include resellers of cheap Chinese pellet mills. The quality of many small pellet mills is not very good in most cases. Therefore it appears some people are interested in trying to make their own pellet mill from home. There are various videos on YouTube of such projects, and I’ve included an example of a homemade pellet mill below.

Example of a Homemade Pellet Mill

The video above is of a small homemade pellet mill made in the EU. They have based the design on a small flat die machine and they appear to be producing wood pellets to a reasonable quality. The design is very simple, the material is fed from the top and they have a fixed die and a rotating roller carriage which is forcing the material through the die. They have a fairly low gearing which will provide them with good torque to produce better quality pellets. However, the productivity of this small homemade pellet mill is going to be very low, probably about 10kg/h.

Homemade Pellet Mill Rollers and Dies

Something to note about most homemade pellet mills you will see on YouTube is that they are not totally ‘homemade’. Often as the case appears with the video above the rollers and die are actually sourced from China. I recognise the rollers and die from a range of flat die Chinese pellet mills I’ve seen in the past.

Therefore, the homemade element of these builds is actually to do with the pellet mill housing, gearbox, motor and electronics. Realistically, this is the most practical means to produce a homemade pellet mill. As pellet mill dies and rollers are made from a specific grade of carbon steel which is then hardened to ensure a reasonable operating life. No one has the ability to hardened steel rollers and dies at home. Therefore sourcing these parts from existing pellet mill manufacturers is really the only viable option.

You could make the die and rollers from machined steel and skip the hardening process. However, the rollers and die of your homemade pellet mill would probably last under a hundred hours of operation before they were worn out. Also, a die is drilled to a specific compression ratio with an inlet taper to suit the material being processed. Trying to make your own dies would take a lot of trial and error to produce a suitable grade of wood pellets for stoves and boilers.

Does it make sense to produce a Homemade Pellet Mill?

While you may be able to produce a homemade pellet mill such as that in the video above, is it really worth the effort? A homemade pellet mill as seen in the video requires constant supervision. Also, you have first have to source and prepare a suitable raw material to the right particle size and moisture content before you can even think about using it in a homemade pellet mill.

Homemade Pellet Mill Economics

So let’s say for instance you are producing between 10-20kg/h an hour of wood pellets with a homemade pellet mill. It will take you around 66 hours to produce 1,000 kg/h which has say a value of £230/$290. You are effectively paying your self under £3.50/$4.40 an hour to operate the homemade pellet mill. Within that time you also have to cover raw material costs/preparation and the payback on the equipment you purchased.

When you add up the cost of equipment and time to produce wood pellets for fuel at home it’s not really viable. To be honest, a much better idea would be to invest the money into a larger wood pellet storage silo so you could get a lower price per tonne. With a wood pellet silo, you could have loose bulk deliveries of wood pellets via tanker instead of bags.

When might a Homemade Pellet Mill project work?

Small flat die pellet mills from China are often not made to the best quality. Therefore by building a homemade pellet mill you would probably be using better quality parts. As stated above, the economics of a homemade pellet mill means you will not be doing it for cheaper fuel for your pellet stove or boiler. Really, it would only be a hobby project with one exception, BBQ wood pellets.

If you’re not sure what BBQ wood pellets are, I’ve got a post about Traeger and their BBQ wood pellet plant. Basically, BBQ wood pellets are easier to use than charcoal and produce a better flavour than cooking on gas.

BBQ wood pellets are the most profitable wood pellet fuel you could produce. To the point where even on a small scale with a homemade pellet mill producing 10-20kg/h, you could actually make a profit. The thing with BBQ wood pellets is there are so many different blends and flavours. If you could produce your own unique flavour and establish a brand you could make a profit producing BBQ wood pellet from home. So that’s something to think about, first though you really need to learn as much as you can about how to make wood pellets before even consider making a homemade pellet mill.

Wood pellets have a very wide range of uses. They can be used in stoves and boilers for fuel, as animal/horse bedding and even for BBQs. With such a wide range of uses, wood pellets are produced to different standards and qualities. For instance, when it comes to burning wood pellets the percentage of ash produced is an important consideration. However, when wood pellets are used for horse bedding how much ash those pellets produce when burnt is relevant. Therefore with this post, I wanted to discuss the different grades of wood pellets and what effects their grade.

Premium Wood Pellets For Fuel Uses

There are various different grades of wood pellets used for fuel. The highest standard of pellets and the most expensive are referred to as ‘premium wood pellets’. These are typically produced from the waste sawdust from timber production. However, to produce premium wood pellets from logs the bark has to be removed.

What is considered to be a Premium Grade Wood Pellet?

To be considered as a premium grade wood pellet generally means the following requirements are met:

• Ash content at or below 0.7%
• Moisture content below 10%
• Good mechanical durability with low fines

So as shown above, a premium grade wood pellet requires ash content below 0.5%. However, it also means the pellets produce very little dust, also known as fines. Finally, it also means the wood pellets were produced to a sufficient density. Wood pellet density is very important, as a low-density wood pellet will produce more fines during transportation and handling. You can easily test for yourself if a wood pellet is produced to a good density by breaking the pellet horizontally as shown in the diagram below.

For premium wood pellets, in fact, any well-made wood pellets you expect a clean snap with very few fines. There are various premium wood pellet certification schemes, below are some examples:

Pellet Fuels Institute Wood Pellet Grading

The Pellet Fuels Institute (PFI) is the predominant wood pellet trade association in the US. The institute works with both pellet fuel manufacturers and pellet stove manufactures. Pellet stoves and boilers can use the PFI Fuel Grade stickers to inform consumers that they should only use a particular grade of wood pellet fuel in that appliance.

The PFI has three grades of wood pellets under its certification scheme. They include Premium, Standard and Utility. The table below from the PFI shows the requirements to meet the certification standard of each grade.

The Difference between Premium, Standard and Utility Wood Pellet Grades

First, it’s important to note that all grades have the same required diameter and length. However, the premium grade has slightly higher durability (>96.5), lowers fines (>0.5%), lower ash content (>1%) and moisture content (>8%). Most pellet stoves sold in the US can only use the PFI Premium grade however some are branded with the PFI Standard. Standard grade wood pellets are cheaper to purchase, but you will have to clean out the ash draw more frequently.

ENplus – European Premium Wood Pellet Standard

ENPlus is a premium wood pellet standard agreed by the European Wood Pellet council back in 2011. The objective was to create a quality standard to make the trade of wood pellets as a commodity simpler with an understood price to a quality relationship. Since then ENPlus has seen the following:

• 911 companies part of the ENPlus certification scheme
• 10 million tonnes of ENPlus wood pellets produced in 2018

However, it’s important to note that this standard is not only used in Europe. There are wood pellet manufactures in North and South America and even Asia who are part of the ENplus premium wood pellet certification scheme.

ENplus Premium Wood Pellet Requirements

So as you can see from the table above, there are three grades of ENplus wood pellets. A1 is the top ‘premium’ grade, then there is A2 and finally, grade B.

You can see that all the wood pellet grades are produced as either a 6mm or 8mm pellet, however, there is also a length requirement of between 30mm and 40mm. The reason for this is some pellet feed system augers are specifically designed to deal with pellets up to s certain length. If the wood pellets are too long they can potentially cause damage to the feed systems on some stoves and boilers.

The ash percentages are below 0.7% for A1, below 1.2% for A2 and below 2% for grade B. You will also notice that grade A1 is produced to slightly mechanical durability than A2 of B grade. Most pellet stoves and boilers could probably run on the A2 grade. However, grade B may produce just too much ash for some pellet stoves and boilers.

What are ENplus Grade B Wood Pellets for?

ENPlus grade B wood pellets can also be referred to by the term ‘standard grade’ or ‘industrial grade’. Now, there are some domestic pellet stoves and boilers which can burn these wood pellets. For instance, my Tatano pellet boiler can burn pretty much any type of biomass pellets. I’ve successfully burnt cardboard pellets up 10% ash content! Therefore ENPlus grade B wood pellets at 2% is not an issue. The main market for grade B wood pellets is larger commercial pellet boilers and even for co-firing in coal power stations.

ENPlus Wood Pellet Certification Fraud

There are some wood pellet manufacturers and resellers falsely claiming their product is manufactured to the ENplus standard. Therefore ENPlus have a fraud investigation team. They also invite customers to contact them over wood pellets carrying the ENplus certificate which they believe are not up to standard. ENplus actually have a blacklist of companies who have misused their trademark.

Wood Pellet Grades for Horse and Animal Bedding

There are no specific grades for wood pellets used for horse or animal bedding. However, as stated above, ash content and durability of horse bedding are not a concern. Therefore, for the best value for money, you could purchase loose wood pellets of either standard/utility grade as per the PFI or ENplus Grade B. Just make sure to store the pellets in a space protected from the elements with low humidity.

Fuel pellets for pellet stoves and boilers are today almost exclusively made from wood. However, hemp may start to replace wood as the prominent source of biomass for fuel pellets for domestic pellet stoves and boilers.

Currently, its the wood industry who have really driven the fuel pellet market. Wood pellets produce a much lower ash content compared to grass, hay or straw pellets. Furthermore, grass, hay and straw pellets can create significant issues with corrosion in the pellet stove or boiler. However, hemp fuel pellets have very similar qualities to wood pellets but are made from a much more sustainable raw material.

What are the Issues with Other Biomass Materials?

Before we discuss the benefits of hemp pellets, we need to address the issues other biomass fuel pellets experience. The pellet fuel market is now developing to include other biomass energy crops such as miscanthus, switchgrass and hemp. All of these biomass materials can be collected and processed in the pellet mill to produce grass pellets which are suitable for fuel-flexible pellet stoves and boilers. However different biomass materials produce different combustion results, we have seen this through our experiments with our biomass pellet boiler.

The Issue of Ash

While miscanthus and switchgrass both have their merits, they also have their issues. The problem with most grasses and straws is during combustion they produce a significantly higher ash content than say premium wood pellets. Many pellet stoves and boilers are designed specifically to burn wood pellets with an ash content below 2%. Therefore using grass pellets can often create issues. With some biomass pellets, the ash content can be as high as 10%. Therefore this either means the ash bin fills up really quickly or in some cases, the pellet stove or boiler can stop working altogether.

Clinker Formations

The other problem with some biomass fuel pellets made from grasses and straws is clinker formations. Clinkers are where the ash melts and forms together into a clump. Most pellet stoves and boilers have no means to deal with clinkers, as they were specifically designed to run on wood pellets. When the clinker is hot it’s soft and sticky. However, when it cools it’s as hard as glass. Luckily our pellet boiler is very durable and able to deal with such clinkers. However, most pellet stoves are not. And a clinker such as that shown in the image above could do a small pellet stove some serious damage.

Why are Hemp Pellets Different?

Well, hemp pellets, unlike other none woody biomass fuel pellets, produce only around 2% ash content. Therefore hemp pellets can be used in a much larger range of pellet stoves and boilers currently on the market today.

Another advantage is that hemp pellets are no more corrosive to burn than wood pellets. This is not the case with fuel pellets made from straw, miscanthus and switchgrass. Finally, hemp pellets do not produce clinker formations as the ash melting temperature of hemp is similar to wood.

So what’s holding Hemp Pellets back?

The biggest issue with hemp is the current legal restrictions around its growth. Industrial hemp under many laws today is covered under the umbrella of laws restricting the growth of marijuana. While hemp may look very similar to marijuana it is not the same plant. The THC content of industrial hemp is so small it’s said you would have to smoke a whole field of hemp to feel any effect. Even where hemp is currently legal there are restrictions on its growth. In the UK you can only grow hemp if there is a suitable processor to take your crop. But this creates the ‘chicken and egg’ scenario. It’s very hard to grow hemp as there are very few legally registered processors. And they are very few hemp processors because they don’t have a ready supply of industrial hemp.

Is all of the Hemp Plant used to make Fuel Pellets?

No, hemp fuel pellets are only produced from the shiv. Hemp shiv is the woody core of the hemp plant. First, the outer fibre is separated from the hemp plant and goes to make clothing and other products. Large hemp shiv particles can be used in construction in combination with lime. What’s left over are small shiv particles and its these particles that can be processed into hemp pellets.

Conclusions on Hemp Fuel Pellets

While wood pellets are currently where the fuel pellet market is focused, hemp pellets could hold significant market share in the future. As the use of industrial hemp scales up, more hemp shiv and shiv dust will be produced. That’s a particular aspect of hemp fuel pellets I find so appealing. The raw material is a byproduct of a byproduct. It means making fuel pellets from hemp is the most efficient fuel pellet process there is.