[Penninehillbilly]

HI
cleaned the rayburn flue this morning we burn joiners offcuts. got a black rubbish bag full of the black stuff.
now this isn't soot as I would think it, some powdery, but most of it is big lumps, very light,can I use this in the garden?

[Womble]

Personally I wouldn't.

With wood ash, what you're getting is all the stuff that didn't burn off, which hence contains minerals that your veg need, and helps to raise the pH of the soil.

With chimney sweepings, that's stuff that was carried up in the smoke, but then condensed or collected on the walls of the chimney.  As a result, especially with offcuts from any treated wood, I think this could contain lots of nasties that you don't want near your food. Your mileage may vary of course - this is just my gut feel.

[Cosmore]

but most of it is big lumps, very light,can I use this in the garden?

The lumps are probably tar residue, not nice stuff. Powdery soot and wood ash (potash) are ok to dig in the ground, but soot is best left for a year to weather before using - fresh soot will 'burn' plants and vegetation - but spread in a 2/3 inch band on the ground around the veg patch is good for keeping slugs off.

[Penninehillbilly]

Thanks, I think I'll let him dispose of it. I do use the wood ash, just thought this stuff may be useful.