Horticultural reader Ed Hanson has emailed me with a query:
I have a log burner at home that I also burn coal on (a type of smokeless fuel actually). Can I use this stuff from the grate as a pot ash feed, or would I need to sift out the coal. I don't want to put anything on that would damage the soil.
I think I know the answer, and it's a no, but I am not quite sure why, other than the coal waste won't break down, and may contain chemicals that you wouldn't want in the soil - particularly if it's a form of smokeless fuel that's been treated.
Can anyone fill in the gaps in my knowledge on the science of coal dust?
I know that people used to use cinders from fires to make permanent paths, similar to the way we make paths with gravel now. Obviously this wasn't with smokeless fuel, just regular coal. And they got through a heck of a lot more of it than most of us. But perhaps you could recycle your cinders this way.
Posted by: Mel Rimmer | January 10, 2007 at 07:09 AM
Most composting guides say you should avoid coal ash, but very few say why.
http://www.richmondshire.gov.uk/default.aspx?page=27010 says it is because of the high levels of sulphur. Mind you, http://www.northamptonshire.gov.uk/Environment/Waste/Compost.htm says it's just fine to compost.
Mind you, I did find this page in my search: http://www.wasteonline.org.uk/resources/InformationSheets/HistoryofWaste.htm
It's not enlightening on the subject of coal ash, but it is pretty interesting!
Posted by: Muppet | January 10, 2007 at 09:20 AM
I use the burnt contents of my wood burner on my flower beds and they lap it up but not on my veg as household coal as far as I know does contain additives etc that I wouldn't really want to eat.
Posted by: Andrew | January 10, 2007 at 09:58 AM
I think the biggest problem with coal is it contains trace amounts of heavy metals and radioactive isotopes, which could become a problem in the long run if they built up in your garden. Coal ash is sometimes used in construction materials, like cement, but it's use is often restricted for this reason.
Making a walkway from the cinders sounds like a good way to use them.
Posted by: Patrick | January 10, 2007 at 11:02 AM
I beleive the reason for not using coal as on the soil is that it contains very few nutrients and also the dust particles are so fine they tend to turn the soil to mush. Nitrogen in the form of urea also has this effect.
Cheers
Funky
Posted by: Pete | January 14, 2007 at 07:32 PM
please send me abaut hydrotermal carbonisation from waste to soil an coal.thanks
Posted by: arti steradian | October 01, 2007 at 09:28 AM