Burning Wood Pellet in an Ordinary Stove

[cye]

At the request of Marian Farrell, Transition Derry, here's a picture of wood pellets burning in an ordinary wood-stove. No special £3000 wood pellet stove required!

Here's what's required to burn wood pellet successfully:
(1) Some form of 'basket' with suitably sized holes both to prevent the pellets falling through & to provide sufficient air to burn the pellets
(2) Understand the general refilling/refueling technique
(3) Spend a few evenings learning how to 'fine tune' the general technique for your own specific stove

Wood pellet is a beautiful renewable clean fuel. When burnt correctly, pellet not only provides great heat from a natural waste product (sawdust), but is such a clean & efficient burn that you will rarely have to empty the ashes or clean the stove glass.

Gone (largely) is the morning drudgery of emptying the ashes and cleaning the glass which all stove owners are familiar with.

I'll put up a number of posts over the coming days explaining a little bit about what type of pellet I've found works best, the general refueling technique, and some other considerations.

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[cye]

This is the basket the morning after a full day's burn. This photo was taken about two years ago and the basket is still going strong with no signs of burning out!

That tiny bit of dust at the bottom of the basket is all the ash there is per day. The 'mesh thing' in the middle of the basket is an additional air feed pipe which I've since removed as it is unnecessary except for burning very poor quality pellet.

The basket is made of woven stainless steel mesh and I've joined the sides crudely with stainless steel wire - Yes, I could have welded a basket up easily enough and made it 'professional', but this way anyone with a pair of heavy tin snips can make their own basket provided they've scavenged some suitable mesh.

Tip the minuscule amount of ash into your ash-pan and you're ready to go again. We need to empty our ash-pan once or twice a month!

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[cye]

Here's some rough notes on filling and refilling the pellet basket. You will have to fine tune this technique for own stove. This all sounds a bit fiddly, but after a while you don't have to think about it!

Key thing is to avoid the temptation to fill the whole basket up with fresh pellet each time it burns down - This never ever works, and only generates a stove full of unburnt smoke. Always try and keep active flame on at least some part of the basket.

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[cye]

What kind of wood pellet works well?

I have tried several types and grades of wood pellet: Hardwood, softwood, standard grade, premium grade, etc. Here's what I've concluded so far:

Premium grade pellet is <1% ash and low moisture (typically <10%).

Standard grade pellet is approx 4% ash and similar moisture.

There's no real difference between hardwood and softwood pellet as far as I can tell. This is because the sawdust is compressed into the same size and density of finished pellet.

Assuming your pellet is dry, the ash content of the pellet is the critical factor when burning pellet in an ordinary stove. Why? Well, it really just comes down to common sense and the need for a sufficient air supply when burning something.

Many specialised pellet stoves and boilers have an automated shaker or some other mechanism for ash removal, so ash content of the pellet is not so critical. With a pellet basket however you don't want to be shaking the basket constantly, and so you want as little ash generated as possible. High ash content is a problem because lots of ash can clog the air gaps between the pellets and will smother the burn, resulting in difficulty keeping the pellet basket lit without frequent intervention (i.e shaking/poking).

We tried a standard grade wood pellet supplied by Carlisle's in Ballynahinch and it nearly put us off burning pellet forever. The problem however was traced to their pellet being very high ash (4-5%), which clogged the air gaps between the pellet resulting in tonnes of work shaking/de-ashing to keep the pellet basket alight. They sell this stuff both as a fuel and as horse bedding. Stay clear of anything that is not guaranteed to be <1% ash.

Low ash pellet such as Balcas Brites doesn't require any shaking at all and produces a tiny amount of ash - See the photo of the empty basket above showing a day's worth of ash. Balcas Brites are made locally and are a dream to burn. Any other brand of low ash (premium grade) pellet should be just as good though.

I'll put up some notes on pellet costs, buying in bulk versus by-the-bag later on.

[campbeji]

Hi Cye,

I'm really enjoying the series on burning wood pellets in your stove. I'd love to be able to do something like that but I currently live in a house with no chimney, so thats not going to work till I get a new place (anyone got a £100,000 there not using just now ;D ).

I know nothing about these wood burning stoves especially burning wood pellets, all I have seen has been huge ugly industrial type burners that would go in a plant room and be fed from a big hopper.

A question I was wondering about, the pellets are obviously available commercially, but can you make your own? Assuming of course you had the wood available, they are just compressed sawdust aren't they. Mind you it'd probably be more hassle than it'd be worth.

Jim

[cye]

Jim,

As far as I know you don't need a chimney for a stove. Provided you follow the rules for minimum distances between the stove and the walls and any surrounding flammables. Stove can sit on a DIY-built hearth, flagstones etc. Flue pipe can exit a wall provided certain rules are followed to protect the wall where the pipe passes through. I can look up the regs and let you know what the details are if you like?

Pellet machines are available but cost big money. If you have waste wood dust or chip to burn you may be better thinking of a woodchip or sawdust burner or perhaps a gasification boiler, but these are special purpose burners unlike the ordinary stove.

hope this helps

[cye]

And here's another method - the Pellet Grate. I haven't tried this method but these are sold in the states as the "Bradley Burner' and there's also a bloke who sells them on eBay Uk for about £40.

The idea is to help the air feed to the pellet.

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[cye]

And here's a Swedish made pellet basket for sale on the likes of eBay for about £40. Not sure what material it's made of, but this one has the raised floor grill which provides more air to the inside of the basket:

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[cye]

How to light a pellet basket:

In the US they all seem to use alcohol gel, in Sweden firelighters - All sounds like trouble compared to lighting with gas.

We use a cook's lighter with a push button spark. One of those half lighter half blowtorch affairs used for caramelising desserts and cakes. 1 refill tin of lighter gas costs about £2 and lasts a year i guess.

Use the lighter/mini-blowtorch for 1 minute then close the door of the stove and open up the bottom vent to roar the fire up.

[cye]

Some thoughts on coal versus wood pellet.

Energy Content of Wood Pellet - versus- Coal: Typical energy content of wood pellet is 4800KwH per metric tonne. That's only about half that of the theoretical content of coal.

However, at about £130/tonne when bought in bulk deliveries, wood pellet is less than half the price of coal and so is better value.

Here's a few other considerations on the energy efficiency of burning coal:

(a) Most coal I've seen is normally soaking wet and burns very uncleanly. Lots of smoke, tar and soot build-up. These are all telltale signs of inefficient combustion because visible smoke, soot etc is all really just unburned fuel. As a result, you won't get near extracting the theoretical max energy return from burning coal unless you use a specialised high efficiency coal burner such as a gasification burner/boiler.

Pellet on the other hand is very low moisture content and burns very efficiently in any good woodstove, as evidenced by the low soot, low smoke, and almost negligible build-up of tar on the stove glass.

(b) handling coal is dirty. wood pellet is clean to handle

(c) Daily maintenance and cleaning out of ashes required for coal burning. Far less frequent ash removal and stove cleaning required when burning pellet.

(d) Ease of lighting. Pellet requires a cook's lighter for less than a minute to get it started, coal requires considerably more effort such as firelighters, sticks, papers, etc.

Disadvantage of wood pellet used in an ordinary stove:

Probably the only disadvantage I can think of is that pellet won't keep a fire in overnight. Needs tending (refilling at least every hour).

[ramack]

Yeah, I'm resurrecting an old thread....
Those of you the are using the baskets in your non-pellet wood stove, how well are they burning and heating?

[cye]

the pellet fuel burns very cleanly with almost no ash. i empty the ashes only once every few weeks as opposed to every few days with wood or daily with coal or turf/peat.

the glass in the stove stays cleaner too. other than slightly more frequent feeding required, in my view the basket with pellets is the cleanest, easiest fuel to burn in a wood stove.