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How do I handle the ash from my biomass boiler?

Posted by Trish O'Flynn on 27 February 2017 at 2:05 pm

In this video SuperHomer Mark Brown reveals the suprisingly small amount of ash produced by his wood pellet boiler after burning through around  4.5 tonnes of wood pellets each year. Mark lives in a five bedroom house in South Buckinghamshire with wife Liya and their children. The house was built in the early 1980s and the boiler installed in 2009.


Marks’ boiler uses bagged wood pellets and is filled by hand. The bags are delivered on pallets, which are over 1 metre high. Bag size may vary but are usually 10 or 15 kg in weight. Stacking the bags safely, lifting and emptying the bags requires physical strength. If manual handling of bagged pellets is not for you and you have the space for bulk storage, why not think about an automatically fed pellet boiler with a silo for blown pellet deliveries?

Installing a silo for automated deliveries and boiler feeding may not take as much space as you think, YouGen member installer Chris Boniface of Intelligent Heating Solutions explains:

“Not all boilers require a lot of space around them for servicing, some only need two inches, and we have fitted a boiler, pellet silo and buffer tank into a floor space of less than 10 square metres. If you think you’ll change your mind about hand filling the boiler, then it is worth remembering that some boiler models have the capacity to add automated filling at a later date. Ask your installer before you decide which model to buy.”

For more, see the YouGen blog on choosing a boiler and Mark Brown's videos on refuelling your biomass boiler and dealing with bagged wood pellet deliveries.

What can I do with the ash from my biomass boiler?

Surprisingly, the 4.5 tonnes of wood pellets Mark burns annually produce such a small amount of ash that the ash box only has to be emptied once a year. Of course, this will vary according to the model of boiler and the amount of wood fuel you burn.

When your wood ash comes from a stove, there are some basic safety precautions you’ll want to remember:

  • let ashes cool down overnight before handling
  • use a metal ash shovel and bin
  • wear gloves.

With a biomass boiler, you only need to worry about hot ashes if you are cleaning out the burner unit shortly after use. Any ash that the biomass boiler produces drops into a metal bin where it very quickly cools as there is so little of it.

You can put fully cooled down wood ash in your bin for collection by the council but, unlike coal ash, there are other uses for wood ash that you might want to think about.

Chris Boniface comments: “Wood ash is good for your garden soil and compost. It’s a source of potash (potassium), but it is very alkaline, so it’s best added to your compost or mixed directly into the soil in small quantities. It doesn’t suit all plants and definitely not your roses... Not all wood ash is suitable for the garden - ash from treated or manufactured wood (including from mixed fuel briquettes) should be avoided.”

Other uses for wood ash include:

  • treating slippery or icy paths
  • producing lye for unblocking drains and making soap.

Mark and Liya Brown are committed to reducing their carbon footprint and have achieved a 90% carbon saving by investing in solar thermal and PV, insulation throughout the house and, of course, the biomass boiler. Take a look at Mark and Liya’s SuperHome page.

Video credit: SuperHome 59 on YouTube


1. Royal Horticultural Society



More information about Biomass Boilers and Energy Saving and Renewable Energy on YouGen.

Find a Biomass Boiler installer

About the author: Trish is a web content writer with the National Energy Foundation.

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

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