Can You Compost Wood Ash?
Yes, with care. Ash from clean, untreated firewood adds potassium and calcium, but it's strongly alkaline. Dust it on in thin layers, keep it out of compost for acid-loving plants, and never use ash from painted, treated or manufactured wood.
At a glance
| Home compost pile | With care |
|---|---|
| Green or brown | Neither (not a green or brown input) |
| Moisture | Dry |
| Prep | None needed |
| Worm bin | No |
| Bokashi | No |
How to compost wood ash
Let ash cool completely for several days in a metal container, since buried embers can stay hot and start fires. Sprinkle it in a thin dusting between layers, like flour on a countertop, not in heaps. Stop if you're adding it every week.
Wood ash can also go straight onto beds that need liming, in thin amounts and ideally after a soil test. Otherwise, bag it for the trash.
What goes wrong
Too much ash raises the pH, which drives off nitrogen as ammonia and makes compost unsuitable for blueberries, azaleas and rhododendrons. If you've overdone it, dilute with more greens and browns. Ash from treated wood, painted wood, trash or plastic can contain heavy metals and should never go in.
Worm bins and bokashi
Worm bin: Keep wood ash out of worm bins; it's caustic and dries out the bedding.
Bokashi: Ash doesn't belong in bokashi, which relies on acidic fermentation.
Balancing the rest of your pile? Check the balance with the compost mix calculator.
From hopcompost.com/can-you-compost/wood-ash/ · General guidance, not professional advice.
Frequently asked questions
Is wood ash good for compost?
In small amounts, yes. It adds potassium and some calcium. In large amounts it makes compost too alkaline.
Can you compost fireplace ash?
Yes, if the fireplace burns only clean, untreated firewood. Skip it if you burn painted scrap wood, trash or manufactured fire logs.
What's the difference between wood ash and charcoal ash?
Ash from untreated firewood can go in sparingly. Charcoal briquette ash contains binders and additives and should stay out.