I wrote this to help some of the new pellet burners better understand wood pellets. Its not for the novice and its just a basic beginners guide. I also included a few terms we commonly say around here.
I have been working on it for a while, So if you see errors(ya all know I can't spell for chit). Let me know. ........
A guide to wood pellets for Newbies
Its a common misconception that all wood pellets are the same. They look the same and feel the same. But they really are different in many ways. Here are some of the basics. Lets start with looking at the labels. No not the branding labels, The labels that you will see somewhere on the bag(usually on the front). There are catagories within these labels that may help give you an understanding. Here are 2 typical labels you might see.
Grade: The common grades are Premium, Standard and Utility. Each grade has different tolerance's. But we will concentrate on the Premium as it is the most common. I will list the tolerance's later.
Material: What the pellet is made from. Or what fiber is in the make up of the pellet. Commonly wood, But you could see actual fiber species. Label #2 is spruce fiber from a spruce tree.
Ash: What percentage of ash is in the pellet. Ash is what doesn't burn and is a left over. The stuff you will need to clean
Fines: The percentage of fines or degraded pellets. During transport and handling the pellet will rub together and fall apart leaving dust or small particles of the wood fiber.
Sodium: What is commonly called salt. The more salt the more the pellet has a chance the Ash to bind or fuse together Some of the labels may list this as chlorides.
Back to the grade tolerances. Here are what the EPA has sent them at. Premium being best and Utility being the worst.
There used to be a Super Premium grade. But that has been dropped buy the brands carring the PFI label. Some brands do still offer the Super Premiums So I will include the specs.
- Premium - <1% Ash
- Standard - <2% Ash
- Utility - <6% Ash
Now lets dig a little deeper. EPA has a chart that also shows other categories. These may not be on the bag. I am only going to cover what has the most effect on burning them for now.
- Super-Premium - <0.5% Ash
Bulk Density: This is basically the compression level of the pellet itself during the milling process. The higher the number the more dense the pellet is. This is measure buy using a 1 cubic foot box and the pellets are dumped in. The number you see is the weight of what the pellets were that filled the box. 40 to 46 is the standard.
Don't confuse this with bag weight. The bag will still only weigh 40 pounds. What you will notice is the denser pellets the bag will seem skinnier and The less dense pellet the bag will seem puffy or more full in appearance.
Size: Diameter and Length, Diameter is usually around 1/4(0.25) inches. Minimum is 0.23 and should not exceed 0.285. Length should be under 1.500 inches and The allowance for pellet over 1.500 inches is 1.0%(or 0.04 LBS).
Inorganic Ash: Same as the ash we already covered. Maximum allowed is less than 1.0% for Premium grade. 0.5% for Super Premium grade.
Moisture Content: The amount of moisture in the trapped in the pellet. Maximum allowed is 8%
Chloride: Also called sodium. Maximum allowed is 300 PPM(parts per million).
Heating value: Usually called out in BTU(british thermal units). The average pellet will commonly have 8000 BTU's per pound.
Additives. Things like die lube and binders may be listed. Die lube is just that something that help the fiber extrude through the die. Binder is something that may be added to help the fiber adhere better.
A few things that you may hear while shopping for pellets or some other stove burners may talk about.
Fiber: Is the wood base of the pellet. Usually its is from saw dust or chips from lumber production.
Hardwoods: Pellets made from hardwood fibers. A good example is Oakor Maple.
Softwoods: Pellets made from softwood fibers. Commonly you might see SPF. Which means Spruce-Pine-Fir.
Blend: A pellet made from a blend of hardwoods and softwoods.
Batch: Is what the mill the production lot. Can also be the mix they are using. Each time its changed they may designate a different batch number.
Chip to logs: Some mills don't use saw dust or chips. They will process whole logs to produce the fiber. First the log is debarked and then hammer milled into chips small enough to use in the milling of the pellets.
Carbon: Carbon is a solid form of the ash which sticks to the burnpot. This what you need to scrape from the burnpot in between cleanings.
Clinker: When the ash fuses together it forms a hard rock like object. They usually clog the burnpot and requires removal.
Middle of the road: This is what the average pellet might be called by some.
Shoulder Season: The time of year where your stove only needs to work part time. Early fall and late spring for the most part.
Shoulder Pellet: Another name for an average to below average pellet. Because your stove is only working part time. You can get by with them.
OK, Now that we know some of the terms. Here's what I think may help you while your out searching for pellets.
Besides comparing the price. The most important thing to check is whether the pellets are wet from being out in the elements. It the bags have physically gotten wet and you see water on them. Be careful as the pellets may have absorb moisture. Try to avoid these if possible. Some sellers will exchange them if you do happen to get a wet bag, But if you open a bag and see soggy or mussy pellets don't even try to burn them. It may clog your stoves auger.
You could look at the ash content and try to choose the lowest possible in your price range. You might need to ask the dealer when the label only states <1.0%. Usually the Softwoods will have the lowest ash content. But some Hardwoods also do very well. I recommend to try to stay below 0.7% as if you go higher it will require more cleanings.
The ash you see can be deceiving. What you see is volume and it’s not how it’s measured for the standards. Ash standards are calculated by weight or percentage of the samples weight. Example, To stay in the < 1.0% standard a 40 pound bag of pellets ash content can’t weigh more than 0.4 lbs.
BTU content can also be used to help choose. You can find BTU contents usually at the manufacturers web site or on review sites. If you can find the BTU reports. Always use the as received test data. The moisture free is a corrected test and we never see moisture free in the real world. This is because Moisture Content effects BTU output. The average pellet usually has approximately 6% MC.
Watch out for long pellets. Anything over 1.50 inches could be a problem for some stoves. They may cause bridging in the hopper and auger jams. Not to mention they also effect the heat output. Long pellets don't provide as much volume to the burnpot as a shorter pellet does
Lets get to what some of the details the stove needs to do before I continue. Stove manuals often specify that if feeds a certain pounds per hour. This isn't actually true. The stove doesn't have a tiny scale measuring the amount of weight it feeds. It conveys the pellets to the burnpot with an auger and feeds it by volume.
Example of Bulk Density. With a higher bulk density pellet you will fit more pellets into the hopper. And a lower bulk density pellet may not fit the whole bag into the hopper. Less dense pellets will require more area (volume) for the same 40 pounds bag. So, A higher density pellet has more weight in the same volume as a less dense pellet. A dense pellet has a higher compression rate, So more fiber is packed into the pellet itself. Confusing, But just think more fuel equals more heat.
A pellet that can provide the most volume or fiber to the burnpot usually offers more heat out of the stove.. As long as they aren't oversized or too long in length. Size and bulk density are the key factors in how hot a pellet feels. If you here someone saying "these pellets are hot"! Its generally because they are a high bulk density pellet that has a small size. They feed more fuel to the burnpot and make more heat.
Now lets get to some tips on choosing pellets. For the most part you aren't going to want to travel to far if you are going to transport them yourself. Even getting them delivered your going to try to stay close to reduce delivery fees. Look for what is available locally and make a list. You can either purchase a few brands and burn them or start digging into what others think of them by reading reviews. I have always liked burning them myself to get a good feel for them.I usually purchase 2 to 6 bags and try them to see how they do. Reviews are good, But first hand information is Better.
If your going to use reviews try to take an average of what's available. More good usually means they are pretty decent. If many are saying bad things, They are usually bad. If the reviews seemed mixed they are probably what we call middle of the road or average at best.
Forums like this one usually have many seasoned burners that don't mind sharing what they have found and you can also get tips for getting the best out of your stove. Most will freely offer assistance and also help with some of the terms above if you don't understand.
If you are going to use the test data. Here is a copy of one and what column has the information you should be using. See red arrow over as received column.
I have only touched the surface, Much more can be learned. I hope this helps you to understand some of the differences and helps you in your venture of finding just the right pellet.
Written by: Jay Takeman