Composting in a Forest

by Liz
(Anne Arundel County Maryland)

We have recently purchased a home on a street with houses on one side and about 12 acres of woods on the other.

Historically all of the neighbors on 'my end of the street', put their leaves, grass clippings, and other yard waste in a pile in woods in front of my house. They call it composting.

While I do see value in this, I am concerned that this 'composting' is very concentrated in one area and possibly dangerous to the trees in this area. Currently the pile is about 40 feet long 20 feet wide and at least 3 feet deep (at least up to my hips in depth).

I have repeatedly asked if we could move the compost pile down the block ... sort of each year it be in a different spot and have gotten a lot of push back from the neighbors. Essentially it has always been in front of my house and no one wants it in front of their house. Of course my feelings are hurt, but beyond that I am concerned for the trees and the area where this is happening.

Is there any technical reason why we should move to 'compost' pile? Any reason why we shouldn't? Am I right to be concerned about the impact of such a large pile in a wooded area.

We do not add to the pile, only the neighbors around us. Right now, we bag all of our leaves to be collected by the county.

Also should mention that we are on a major river off the Chesapeake Bay. The compost pile is within 300 feet of the river.

Danger of Spontaneous Combustion

I think you have potentially a big problem here.
This is an very big "compost" pile, but as far as I can see no one is managing it.

You can get away with that with your average backyard compost but when you have a heap this massive there is a small but real possibility of spontaneous combustion and the start of a very tough to put out fire.

A compost fire is rare. Mostly they occur in piles that are fairly tall, 10 feet or more high. However all the other conditions for a spontaneous fire starting are present and no one is monitoring the material, they are just piling stuff on.

Here are some of the factors that could lead to that lovely heap of grass and leaves spontaneously catching fire…
• the moisture levels in the material are lower, say between 25 and 45%
• the moisture levels are not uniform, in other words there are moist spots where biological activity can get things heating up beside very dry spots which in certain conditions catch fire.
• the pile is large, insulated and with limited airflow… this would be likely in your case
• the pile is unattended… no one is checking conditions to make sure there are no problems developing.
• the pile has been sitting for a long time

Most of the references I looked at suggest that as long as your compost heap is less than 10 feet tall and moisture is more than 45% there shouldn’t be a problem. However, in your case no one is monitoring the moisture levels, nor is anyone out there with a long compost thermometer probing the pile in search of hot spots.

So in my opinion this pile is too big to be left unattended and unmanaged. It should be monitored for both temperature and moisture. At temperatures over 60˚C or 140˚F it would be wise to do something to cool things down.

When you get temperatures of between 70˚C and 80˚C, roughly 160˚ - 175˚F, the biology dies and chemical oxidation is the heat generator. An article in Biocycle magazine says “Unless immediate action reduces this temperature, a compost fire is very likely.”

In your case you wouldn’t know the temperature and you don’t have the machinery or knowledge to do something about it… a very bad combination.

Here is a link to an article describing compost fires. This article talks about these occurring at compost facilities… places where monitoring and equipment are standing by. While your piles are not excessively tall all the other conditions point to a possible disaster. I hope you and your neighbors can use the compost that is ready and find a way to properly manage this material for the future.

And I really hope you can all become and remain friends.

With Best Wishes for All

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