C/N Ratio for Compost Tumbler

by Kim
(Maine)

I lucked into an envirocycle left behind by the previous homeowner and though I’ve muddled through so far I’d love to improve my results.

I’m confused about how to achieve the correct green to brown ratio. Is the ration based on weight or volume?

If my thinking is right it could make a big difference since most of my green is kitchen scraps which tend to be very heavy and the brown is much higher by volume.

I’d like to get things as close to right from the beginning rather than discovering the mix is off and having to adjust midstream. Thanks!

It Depends...

First it depends on what you are using as your browns. In other words what is the C/N ratio of your paper, leaves or wood pellets.

Second your greens are wet as you say. Some common compost greens can be as much as 90% water. They can swamp the material in your tumbler. And if you also have rain you may find some of magically leaks into your machine drowning your compost creation.

So you need to balance not only the carbon nitrogen ratio but also the moisture levels in the composter.

The Moisture

Moisture levels are very important in a tumbler. One way to measure is to take a handful of the material and squeeze it. If no water comes out it is too dry. If a few drops come out it is about right. If a stream of water comes out it is too wet.

So let's say your compost is too wet. What to do? First open drainage to get rid of at least some of the excess water. Then add some brown material that will soak up excess water. One of the best is the compressed wood pellets sold as fuel (and sometimes for a lot more money as cat litter). these have no additives and very low moisture - 5% or less. But their C/N ration would be around 800. So - add this just a handful at a time and leave it soak up the water before adding more.

If your compost is too dry you need to add water a cup at a time. Add a cup, turn the tumbler. Check in an hour or so and add another cup if needed.

The C/N ratio

As for the C/N ratio of those browns - some leaves are about 80, those wood pellets would be closer to 800. That's why you can't measure with volume or weight. You need to balance a bit at a time.

As you work with your tumbler you'll find what works with your material.

Best of Luck.
Leslie