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how to fix unhealthy compost? (at a primary school)

Posted by harold_splat australia (My Page) on
Wed, Feb 5, 14 at 22:38


Our school compost bin is not looking good. It's quite large and receives several buckets of food scraps per week. Most of the scraps are fruit and fruit peels. We've instructed the children not to put in citrus but unfortunately a lot of citrus still goes in, including whole oranges on occasion.The bin is in a spot where it receives plenty of sun.

Lately the bin does not look good. Fruit flies(?) rush out in a swarm when we open the lid and there are layers of maggots crawling around on the top. Haven't seen a worm for a long long time. It stinks so bad it sends small children reeling when they open the lid (and adults too). The kids are learning to be afraid of the compost bin.

Is our compost doomed? Is there something we can do to restore the balance?Should we try harder to keep the citrus out? Is it even possible to maintain a compost which is 90% fruit scraps?

I realize some of these questions have come up before but in other ways the situation is quite distinct so I posted a new thread. Hope you guys have some ideas!!!

Follow-Up Postings:

RE: how to fix unhealthy compost? (at a primary school)

The flies & maggots indicate a pile with too many greens that's gone anaerobic. Mix in some browns, leaves etc. & mix/aerate thoroughly & you'll be back on track in no time. All the fruit is high in nitrogen & needs browns for carbon to balance things out. An approx. 50/50 mix of greens & browns is the best balance.
If citrus will be added, the smaller the pieces the better. They may take a couple of cycles to completely decompose otherwise.
So to summarize the fruit scraps are excellent for nitrogen (& trace minerals) just remember to add equal parts or more browns for carbon & you'll be set.
Hope that helps.

RE: how to fix unhealthy compost? (at a primary school)

Yup, more browns and more oxygen via turning/mixing the pile.

Since you have a pile in need of immediate help you're going to want to look for browns that will break down quickly...dead leaves, shredded newspaper, shredded chipboard cardboard (very shredded/small..not corrugated cardboard like packing boxes, more like cereal box type chipboard), straw, paper bags, etc.

Small twigs, wood chips, corrugated cardboard, and things like that are decent browns if you have time for it...but this seems like an issue where you're going to be looking for more immediate help in your pile construction.

It will probably look and act like a bit of a gooey mess before it settles out and normalizes...there's not an extremely quick fix to it.

If it gets horrible some agricultural lime (1 cup for every 20-25 cubic feet, turned/mixed) can quickly eat up some of that excess N and regulate a bit of the smell, but that's more of a quick-fix rather than a continuing solution for building a proper compost.

RE: how to fix unhealthy compost? (at a primary school)

As paleo said, more brown. When I start getting flies and bugs, I put a layer of raked leaves over the top. Let it sit for a bit, then turn.

Also, when adding stuff to the bin, always dig a small hole, and add the material into the hole. Then cover up the "hole" with the stuff from the bin. It's not foolproof that it'll keep the bugs down, but it helps a LOT. I have friends staying over that just toss stuff in the bin. No covering or anything. And when I open the lid, I get bombarded by flies.

For now for you, I'd rake some fallen leaves, or even get newspaper, and layer it on top of the existing pile in the bin. Let it sit for a day or 2 to kill off most of the flies. Then turn the pile. Outside in. You can put egg cartons (not the shiny plastic like ones), newspaper (the ink is soy based. At least in the US.) crumpled paper, dried twigs (broken up. They help create "air pockets") paper napkins, paper plates, etc. just incase enough dried leaves are hard to come by.

But definitely cover with a layer of brown first, and let sit. Otherwise you'll be working among flies while they're landing on you and buzzing around. Oh. The layer doesn't HAVE to be thick thick. Maybe an inch or so unless you use newspaper, then a few layers.

I currently have a pile going for 3 years. I get flies every once in a while, when people don't bury the fresh stuff. And covering and then turning has always helped. Other people may have better techniques. Hopefully someone more experienced than I will chime in. This is my first compost bin and first attempt at compost :)

Good luck :D

RE: how to fix unhealthy compost? (at a primary school)

The presence of maggots tells me that the material is too wet and the foul odor says the same thing, the compost is too wet. You need to add a lot of some dry material, which would be something in the high carbon (brown) material category.
Perhaps the linked composting tutorial will be of some help.

Here is a link that might be useful: Composting Tutorial

RE: how to fix unhealthy compost? (at a primary school)

I imagine that at a primary school you will have a shredder and that there will be a supply of shredded office paper on tap. I'd mix a lot of that in with what you've got to soak up excess moisture and rebalance the mixture. Also, being at a school, I imagine that you have very limited time to fiddle about with the compost heap and the counsels of perfection regarding turning, ratios and heat are going to be untenable.

I think it would be a good idea to start a second bin. Take the stuff from your first bin, mix it with the shredded paper and pile into the new bin. Then leave it alone. Start filling the old bin again. When it is full have a look to see how the other bin is doing. Some of the contents will be ready to spread on the garden. The bits which are not ready can be put around the system again. Transfer the material from the old bin to the new and start the process all over again.

As a teacher myself, I know the last thing you need is another job, so I'd really try to keep the whole composting thing simple. And I would not bother about banning citrus.

RE: how to fix unhealthy compost? (at a primary school)

Add shredded paper and/or shredded leaves

RE: how to fix unhealthy compost? (at a primary school)

We compost at my office building, mostly coffee grounds and filters but some food waste also. Been doing this for 15 years now so I have some experience. The advice to add browns is spot on. Since you have a lidded bin, no need to dig a hole. Spread out each day's addition evenly, then top with a layer of browns. We use sawdust/wood shavings, sometimes leaves or pine chips like the kind sold for horse bedding (we get damaged bags free). Very important to do this layering for aeration, nitrogen balance, moisture balance, odor and insect control. When a pile is built up this way, it will be balanced all through the cycle. We have very few fruit fly and maggot problems.

When the bin is full, you can turn it into a second bin to 'finish'. We turn our two bins every 6 months, into a chicken wire/cement block bin. By this point there are some recognizable bits but the pile is not that attractive to varmints, and after another few months it will all be compost. Meanwhile begin filling the bin again.

BTW, no reason to leave citrus out, it can be slow especially if left on top or the outside of the pile, but when buried in the pile, especially if it's turned at least once, it will compost just fine.

Good luck and keep us posted!

RE: how to fix unhealthy compost? (at a primary school)

Most every school based composting program I have seen has a lot of high Nitrogen material available and not much high carbon material and that results in a wet and stinky pile of garbage.
If the composting tutorial linked above is not of much use perhaps this from Cornell University might help.

Here is a link that might be useful: school composting

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