Thursday, February 24, 2011

Ashes From Your Fireplace- Compostable or Not?

Who doesn’t love gathering around a nice crackling fire in the winter, wrapped in a fuzzy blanket with a mug of hot cocoa in one hand and a toasting marshmallow in the other? Heck, I don’t even like marshmallows and it sounds like fun to me. But after the fire has died and the Norman Rockwellian merriment subsided, what do you do with the pile of ashes left in the fireplace? Is it okay to toss them in the compost bin?

Maybe, But Only in Small Amounts.

Be careful, and not just because leftover embers could burn you or start a fire in your compost pile (I know, you know fire = hot, no need to roll your eyes).

Wood ash is very alkaline so adding too much can raise the pH of your compost bin, which can wreak havoc on your little microorganism buddies breaking down materials in your bin. A neutral pH is the best environment for microorganisms.

So just a sprinkle is fine, but you don't want to dump a whole bucket in there.

That said, adding a light layer of wood ash can be a good source of lime, potassium, and trace elements. And sometimes you may want to neutralize an acidic bin. For example, if you frequently make fresh squeezed lemonade or orange juice (yes, I feel your eyes rolling again) and contribute lots of acidic peels to your bin, the wood ash can help neutralize the pH of the bin.

Curious Minds Want to Know

The reason wood ash is alkaline is that when it comes in contact with water it creates caustic lye. This is how you would make soap if you lived say, in a little house on the prairie.

Another reason you should use wood ash in moderation is that Cincinnati sits on a giant bedrock of limestone (also a higher pH) and shale. So we usually do not have acidic soils that you would need to neutralize. As always, we recommend testing your soils before using too much wood ash on your garden or in your bin.

Wow, two science lessons in one post- hold onto your hats.

Did I Mention the Answer is Maybe, with Caution?

One last tip- never use ashes from a barbeque pit or charcoal grill. These ashes can contain chemicals which could be harmful to the soil.

So you can compost wood ash if you 1) wait until it’s completely cooled, 2) use in moderation, and 3) don’t use BBQ ash.

If you burn a lot of fires in the winter, you should find another method of using your wood ash. Has anyone ever found a good use for this stuff? If so, leave a comment!