Should shady composting look to the sunny side of life?

composters
Photo credit: Chris LaBelle
Q:

Will my EarthMachine composter work better if it's placed in a sunny part of my yard? Or is a shady place just as good? My friend claims food scraps compost faster when they are warmed up by sunlight (meaning the bacteria would be more active if warmer).

- Multnomah County, OR
A:

Here is the fact: for each 10 degrees Celsius increase in temperature, the rate of a biological reaction doubles. Of course, there are limits, because above a certain temperature, the reaction will stop. So, yes, your friend is correct.

However, solar heat is not necessary for a well-managed compost pile to reach optimal temperatures. I routinely get my compost to 140 degrees F and it's completely shaded. I'm challenged by limited space, so I prefer to use all available sunny spots for vegetable and flower plants (which require sunlight) and keep the compost in the shade - because it can clearly do well without sunlight.

An increase of 10 degrees Celsius is about 18 degrees Fahrenheit.

To really succeed with food waste, be sure to have enough carbon-y dry stuff (straw, deciduous leaves), and enough (but not too much) moisture. A compost recipe of mixed materials - food waste, paper waste, leaves, yard debris - including grass clippings will best feed the microorganisms doing the work in the compost pile and give you good results with fewer pest and odor problems.

Linda Brewer
Senior Faculty Research Assistant
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