Pellet heaters are, and yes I run a pellet heater website so I am clearly biased, a great way to stay warm. Real heat, real fast, without the hassle. However, the quality of the wood pellets used can greatly impact on how well your pellet heater runs and heats your house. Poor quality pellets can cause a heap of issues such as excessive ash and clinkers, which can lead to reduced heater efficiency and more maintenance and cleaning. I touched on the importance of wood pellet length in another article, but below I’ll dive a little deeper and talk about other ways you can check the quality of pellets before you buy them, and even after you bring a test bag home.
Want to make sure you get the best quality pellets you can? Here’s some tips on how to check wood pellet quality. Read on below for more info:
- Length Test – Uniform pellet length between 2cm to 4cm is crucial for consistent feeding
- Smell Test – Wood pellets should smell natural, like wood, not chemicals or dampness
- Visual Inspection – The color and surface texture tell you about quality and manufacturing
- Smoke Test – When lit, pellets should produce minimal smoke that smells like a clean wood fire
- Water Test – High-quality pellets dissolve quickly and cleanly in water
- Density Test – Dense pellets provide more heat and burn longer
- Ask the Retailer – A knowledgeable supplier is your best ally
Length Test
Ideally, you want wood pellets to be around 2cm to 4cm in length. In reality you will probably see pellets that are 1cm to 4cm. Wood pellet length is critical because it affects how your pellet heater’s auger feeds fuel (wood pellets) into the burn pot. The more uniform or consistent the length of pellets, the more even burn you’ll get and constant heat output from your pellet heater.
As I’ve mentioned elsewhere on my wood pellet length article, just eyeball a bag of pellets. This is your first check at the store. Do the pellets look about the same length? Are there any really short or really long pellets? A quick look through the clear part of the bag can tell you heaps before you spend any money and it’ll prevent any surprised once you get home and take a closer look.
What happens with bad wood pellet lengths:
If the pellets are all very long or all very short, then you’ll find that your pellet heater may not burn correctly. Short pellets pack more densely into the auger, so more pellets get delivered per rotation. This means a bigger fire and more heat output than you want. It’ll also mean you’ll burn through a bag of pellets faster.
Longer pellets do the opposite. They don’t pack efficiently and can sometimes jam across the auger, creating gaps in pellet delivery to the burn pot. This leads to a smaller fire and less heat output. So you won’t be getting the same kind of heat from a bag of pellets that are all very long. In bad cases, really long pellets can jam the auger completely. That’s not something you want happening in the middle of winter.
The “fines” problem:
Look for “fines” – that’s the industry term for sawdust and tiny broken pellet pieces at the bottom of the bag. Bags with poor length consistency usually mean brittle pellets that have broken apart during transport. These fines are a pain because they can clog your auger, and won’t burn properly like wood pellets.
You can check for fines by looking at the bottom of the bag – lots of dust is a warning sign. When you pour pellets into your hopper, if you see a big dust cloud, you’ve got too many fines. A bag with lots of fines may also mean the pellets got wet. Wet pellets break down into fines. It’s unlikely you’ll encounter this buying pellets from a retailer but if you don’t know how to store your wood pellets properly at home you may encounter this problem.
When you go to buy wood pellets just quickly look the bags over. You’ll be able to see very quickly if the pellets look uniform in length or are too short or too long. For a proper test, take a handful from an open bag and lay them out. Most should be in that 2cm to 4cm range. A few outliers are normal, but lots of short stubs or really long pieces means poor quality control.
Smell Test
The next thing you can do to try and make sure you get good quality pellets is the “smell test”. This is an interesting one and I personally don’t know how accurate this is but some websites claim high-quality pellets should smell like freshly cut softwood. What I think they mean here is that pellets should NOT smell like anything other than wood.
Good wood pellets are just compressed sawdust and wood chips, held together by the natural lignin that comes out under heat and pressure. So they should smell like the tree they came from – a clean, woody smell. If the pellets have an unpleasant or strange smell (as in they don’t smell like wood), it could be a sign that something is wrong.
What bad smells mean:
The mill may have had to use binding agents to bind the pellets or the raw wood material they used could be poor quality, such as coming from wooden pallets, furniture scraps, or treated wood. A chemical or glue-like smell suggests synthetic binders or contaminated source material. You really don’t want to burn MDF, particleboard, or pressure-treated lumber pellets because they’ll give you a dirty burn due to all the chemicals.
Also, if the pellets were stored incorrectly, like outside in the rain, then a damp or moldy smell might be a sign the pellets weren’t stored properly and won’t burn very well. Wet pellets produce less heat and as I mentioned above may result in a bag full of fines. You may be able to smell the wet pellets and if so take a closer look to see if the pellets are brittle, expanded or starting to disinergrate.
How to do it properly:
Again, I don’t think you’ll get a “freshly cut wood” smell when you open a bag of pellets and take a sniff but instead check to see if the pellets have a natural smell or not. For the best test, pour a handful into your cupped hands and rub them together gently. The friction will help release the smell so you get a clearer idea of what you’re dealing with.
If they don’t smell natural, then it may be an indication that the material used to make the pellets was poor quality. Trust your nose – if it smells wrong, it probably is.
Visual Inspection
In addition to the smell test, the visual inspection of wood pellets is another good way to test their quality. The colour of the pellets can reveal a lot about their quality. High-quality pellets made from debarked softwood are usually light brown in colour. Again, it depends on what the pellets are made from as this will directly impact what they look like. Hardwood pellets, generally speaking, are darker in colour.
However, if the pellets are darker in color, it could be a sign of bark content, which increases the amount of ash and can lead to clinkers. Bark has way more silica and minerals than the actual wood fiber. Clinkers are a natural part of owning a pellet heater but low quality pellets form clinkers more often, which means the burn pot needs to be cleaned frequently to keep the fire burning efficiently.
What else to look for:
A well-made pellet should have a smooth, almost polished surface with a slight sheen. This glossiness is good – it means the pellet was formed under high pressure and the natural lignin melted to seal the surface. A dull, rough, or crumbly surface means low compression and the pellet is more likely to break apart.
Look for stress cracks or deep splits along the pellets – this also points to poor durability.
Furthermore, it is important to pay attention to the outer layer of the pellets. While the outer layer of pellets may be darker due to friction in the pressing dies, this is not an issue as long as the pellets are light in color inside. Breaking a pellet in half can reveal the colour on the inside. If the inside is darker in colour, it is a sign that the pellets may have a high bark content and are of lower quality.
The internal color is the real indicator of what raw material was used. Paying attention to the color and texture of the pellets can provide valuable insight into their quality.
Smoke Test
The smoke test is another way to test the quality of wood pellets. This simple test can tell you about potential contaminants and how clean the burn will be in your heater. To perform the smoke test, simply take one longish pellet and light it at the tip. For better control, use pliers to hold the pellet and a blow torch to ignite it.
Let a small flame establish for a few seconds, then blow it out and watch the smoke.
The smoke produced should smell like burning wood – like a clean campfire or wood-fired oven. If the smoke has an unusual, chemical, or acrid smell, it can be a sign of poor quality pellets. A smoky smell could indicate that the pellets contain additives, such as glue or other chemicals from treated wood sources like particleboard or old furniture.
What to watch for:
Pay attention to the color and amount of smoke. A small amount of thin, white or light-grey smoke is normal – that’s just water vapor and tiny particles from clean wood. But if the pellet produces thick, heavy, dark grey or black smoke, that’s a sign of incomplete combustion. This can be from excess moisture or worse – contaminants like petroleum products, plastics, or heavy resins.
Moreover, excess smoke can result in increased emissions, which are harmful to the environment and can pose health risks. Pellets that produce lots of smoke will also lead to faster buildup of ash in your pellet heater and glass door, plus creosote in your exhaust flue. Therefore, it is essential to ensure that the pellets produce a clean and natural smoke when burned, indicating high quality and efficient fuel.
Water Test
The dissolving test is a simple yet really effective way to test the quality of wood pellets. This test shows whether the pellet is held together by natural lignin or artificial additives. To perform this test, take a small handful of pellets and place them in a clear glass of room-temperature water. Watch what happens over the next few minutes.
High-quality pellets are made from pure wood fiber compressed under extreme pressure, which activates the natural lignin to bind everything together. When you add water, these lignin bonds break down and the compressed fibers expand back to their original state. The pellets should dissolve into sawdust within a few minutes, turning into pulpy mush at the bottom of the glass. That’s what you want.
If they do not dissolve, or dissolve very slowly, it could be an indication of the use of binding agents or poor quality wood material. Pellets that stay mostly intact after 10-15 minutes are almost certainly held together with chemicals or other additives, that may directly impact how clean the pellets burn.
What the sediment tells you:
After the pellets have dissolved, swirl the glass and observe what settles in the middle of the bottom of the glass. The heaviest particles will settle there. If there is a large amount of heavy particles, like sand, grit, or small specks, it might increase the amount of ash and clinkers.
High quality pellets should dissolve fairly quickly and consist of fine particles. A bit of sediment is normal, but if you see what looks like a pile of sand or dirt, you can expect a dirtier burn, more ash removal, and more clinkers.
Also check the water itself – is there an oily sheen on the surface? That can mean petroleum-based contaminants from the source material or machinery, which burns dirty and can damage your heater’s sensors.
Bonus Tip #1: Density Test
The density test is another important way to test the quality of wood pellets. While it takes a bit more effort and needs a kitchen scale, it gives you a proper measure of pellet quality. Density is directly related to how much energy is packed into each pellet and how long it will burn. Denser pellets mean more fuel by weight and higher heat output per bag.
To perform this test, take a container larger than 1 litre and weigh it on a kitchen scale, noting the empty weight. Fill the container to the brim with wood pellets and weigh it again, noting the weight. Then, fill the container with water to the same level and weigh it again.
Deduct the weight of the container from both measurements and divide the weight of the pellets by the weight of the water. The result should be between 0.6 and 0.7 kg/litre and preferably around 0.65 kg/litre.
This indicates that the pellets have been pressed at the right pressure, resulting in a suitable density for efficient heating. If the pellets have a density below 0.6 kg/litre, they are too soft and break easily, forming fines as a consequence. Low density pellets contain more air and less wood fiber, so they burn faster and produce less heat. This leads to reduced heating output, increased emissions, and more clinkers.
Therefore, it is essential to ensure that the pellets have the correct density for optimal heating results.
Quick test: Drop a few pellets into a glass of water. Very dense pellets should sink immediately, while low-density pellets may float for a bit before getting saturated.
Bonus Tip #2: Ask the Retailer
OK, I threw another one for free and it’s probably the best and easiest way to check wood pellet quality. Before you start doing any wood pellet tests mentioned above, have a chat with your pellet retailer. In my opinion, a good wood pellet retailer should be able to tell you what to look for when buying pellets but also they should check quality of their own pellet stock. It’s in their interest to sell pellets of good quality to their customers, because an unhappy customer won’t give them repeat business.
In Tasmania, Pellet Fires Tasmania do everything they can to make sure they are selling a quality product. They understand their reputation depends on the fuel they sell just as much as the heaters.
No matter where you live or what retailer you buy your pellets from, they should be checking their own stock and help you to understand what makes a pellet good quality. Don’t be afraid to ask specific questions. A good retailer should be able to tell you the source wood (softwood/hardwood) and the manufacturer.
What to ask:
- Where are these pellets made and what wood is used?
- What’s the ash content like?
- How do other customers rate these pellets?
- What do you do to ensure pellet quality?
If you are yet to buy a pellet heater and finding all of the above overwhelming, don’t. Ask the retailer where you plan to buy your pellets from what they do to make sure the pellets they sell are good quality. Any good pellet retailer should be able to tell you what they do to make sure you get good pellets from them.
Summary of Ways to Check Wood Pellet Quality
Now, while each of the tests above are definitely useful, I think the most important and useful (besides asking a retailer) is checking pellet length. The reason for this is because most of the other ways to test pellet quality requires opening bags of pellets or other tools, and length can be checked right in the store.
If I had to pick a second test for in-store assessment, it would be the visual test. Look for fines and overall pellet quality. However, please keep in mind the best way to check pellet quality is to burn them. The above methods are not fool proof, but they’re excellent indicators that can help you avoid a bad batch.
Most practical for store shopping:
- Length check – quick visual through the bag
- Visual inspection – colour and texture assessment
- Ask the retailer – free expert advice
For testing at home:
- Water test – great for comparing brands
- Smoke test – good for troubleshooting performance
- Density test – if you want to get technical
Lastly, in addition to wood pellet length, the other way to check pellet quality is price. Yes, I’m not joking. While not perfect, price is often a reliable indicator. Manufacturing high-quality pellets from clean, debarked raw materials costs more than using low-grade sources, which may contain bark and other contaminants. The more expensive wood pellets are the better quality they’ll usually be. Choosing the cheapest wood pellets will usually burn dirtier, which isn’t a bad thing provided you clean and look after your pellet heater.
Regardless, the above should help you spot better quality pellets and give you a much better heating experience. If you’ve got the time check out my wood pellet guide to learn more about wood pellets.
P.S: Expensive Heaters Don’t Make Bad Pellets Good
Pellet heater brand and type of heater, such as a hydronic pellet boiler which heats water instead of air, does not change the importance of wood pellet quality. I see on many forums and FaceBook groups people boasting that their expensive pellet heater can burn any type of pellet, regardless of quality. This is complete rubbish.
Spending more money on a pellet heater does NOT mean it can somehow magically burn poor quality pellets better. A high-end heater may have fancier sensors and more durable components, but it can’t defy physics. Feed it low quality wood pellets and you’ll still get clinkers and lots of ash. Feed it wet, low-density pellets and you’ll still get low heat output and creosote buildup.
All pellet heater brands, from expensive European Piazzetta pellet heaters, Palazzetti pellet heaters to the cheaper Chinese pellet heaters, which are popular in Tasmania, are all impacted the same way by pellet quality. Protect your investment, no matter the brand, by feeding it the high-quality fuel it was designed for.
Resources:
Simple ways to check wood pellet quality website
