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Five top tips for choosing the right wood pellets

Posted by David Fields on 31 October 2011 at 5:30 am

Since the announcement of the Renewable Heat Incentive an increasing number of homeowners and businesses are looking to new and innovative ways to power and heat their property. Alongside solar panels and heat pumps, wood pellet boilers are emerging as one of the most efficient ways to generate heat or hot water for a whole house or building.

Wood pellet boilers work by dropping around five or six pellets into a small burn pot, which then fires them at a very high and constant heat. As a result, the wood pellet used must be the right size and, more importantly, quality, for the boiler you use.

So, when choosing the right wood pellets for your boiler, you should look for:

Low ash and dust content

A high quality wood pellet should have an ash content of 0.7% or less, to get scientific. The lower the ash content the better the pellets burn and the more efficiently your boiler will work. A high ash content is a sign of contaminates in your wood pellet, such as too much bark or moisture.

Similarly, too much dust can damage your boiler and high quality pellets are de-dusted before being bagged. Buying wood pellets to ENPlus standards mean that they should contain 1% or less of dust. 

High ash melting temperature

The burning of wood pellets can sometimes lead to lumps of residue that are unable to burn, which could result in your boiler clogging up. Double check that your wood pellet has an ash melting temperature of above 1200 degrees Celsius, as this will reduce the build up and improve the performance of your boiler.

Consistent wood pellet size

Each wood pellet boiler is designed to take a pellet of a certain size. Therefore, size is everything when it comes to wood pellets. Ensuring that you are using the correct size of pellet, which is 6mm in the UK, will increase your fuel efficiency and decrease the emissions you produce.

Low moisture content

Exactly as you’d expect, wood pellets that have high moisture content won’t burn correctly. ENPlus standards dictate that pellets should contain 10% or less moisture, as this will result in a higher heat per kg and better effectiveness from your boiler.

High heat output (kW/h)

The standard measurement for the heat output of wood pellets is kW/h, enabling you to compare different types of pellets and their performance. You can also use this measure to estimate the amount of fuel you might require in a typical year and therefore your costs.

Weighing up these five different factors, and comparing the different types of wood pellets with these in mind, gives you the knowledge to choose the very best fuel for your boiler. As a result, you should experience greater performance from your boiler, a higher heat output and a decrease in the amount of residue left behind.

About the author: David Fields is wood pellet manager at Woodpellets2u.

If you have a question about anything in the above blog, please ask it in the comments section below.

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3 comments - read them below or add one

David Fields

David Fields from Comment left on: 3 November 2011 at 2:20 pm

In answer to nnw49, you're correct on delivery of blown wood pellets. Pellets will break up under high pressure generating dust on delivery and leaving you a problem when trying to fuel your boiler. Our drivers are trained to deliver at low pressure with tankers limited on how fast they can offload the pellets. Tankers also carry vacuum systems which attach to the exhaust feed on the silo, extracting any dust generated.

Answering Jeff B, hopefully the comment above will offer some comfort in reducing dust in store. We now have 3 pellet producers in the UK certified to ENPlus A1 with other larger producers adhering to the requirements of BS14961-2. Major pellet producers carry out a number of test during production at regular intervals, these include durability, bulk density, moisture, length and fines. Upon loading into the tanker the pellets will be sieved so that the product is no more than 1% by weight fines.

UK Wood Pellets are now produced to the highest European standards with the ENPlus Certification being applied to distributors too.

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Jeff B

Jeff BComment left on: 31 October 2011 at 6:07 pm

David - thanks for your article. My pellets are delivered in bulk but it difficult to assess how much dust is caused by attrition during the delivery process or how many fines are already present in the pellets. I would say an important parameter for pellets would be a friability test i.e. some measure of the inherent strength of the pellets to resist abrasion. I see there is a standard in existence: BS EN 15210-1:2009 Solid biofuels - Determination of mechanical durability of pellets and briquettes. Do you know if UK pellet suppliers apply this test?


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nnw49Comment left on: 31 October 2011 at 1:15 pm

For Bulk Pellet delivery, you need to make sure the delivery driver uses the minimum pressure possible to get the pellets through the pipe.

 Higher pressure makes for a quicker delivery (which the operator will probably be keen to accomplish!), but will tend to smash pellets if they hit the far side of the store... You can get rubber curtains to minimise pellet damage, but they don't seem to be fitted as standard....

 Many feed mechanisms won't move dust/crushed pellets so that becomes waste fuel.

Bagged pellets get a gentler life, but I still haven't found anywhere to recycle the LDPE bags that it comes in!

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