Compost piles will warm up and steam in the winter

Healthy organisms in the compost will be active and produce steam even in the winter time. Steaming compost is not an indication that the compost is on fire. Be Firewise by actively managing your compost.

As a regional resource for Firewise and statewide resource for composting for Michigan State University Extension, I received the perfect question the other day that hit both topics. A caller expressed concerns regarding her compost when her neighbor declared it was on fire and knocked it flat and divided it with his yard tractor because he saw “smoke” coming from it. Apparently, the neighbor was worried it would start a forest fire because the compost was within the tree line of the woods they shared. What that neighbor really saw was steam as a byproduct of healthy bioactive leaf compost, not a fire caused from spontaneous combustion.

This is what I told the caller:

  1. Spontaneous combustion of home compost piles is rare and usually is associated with other contributing conditions, such as composting indoors.
  2. Compost temperatures must reach 300°F to 400°F (150°C to 200°C) for spontaneous combustion of materials to take place. This is unlikely to happen outdoors during a Michigan winter.
  3. Hot composting typically averages temperatures around 150°F to175°F for a short time and requires a minimum size of 3 feet x 3 feet x 3 feet (5 feet is best) before cooling to ambient temperatures due to limiting factors. This method of composting requires more than just leaves to work effectively such as the addition of grass clippings and other nitrogen rich stocks.
  4. Do not confuse steam from your compost in the cooler months with fire. Compost piles will steam and actively managed piles often have the snow completely melted off throughout the winter.
  5. Sheet composting or sheet mulching  is acceptable for leaves and reduces temperature of the pile if you do not plan to actively manage your compost. Just know that this is a cold composting method and takes much longer for the material to decompose.

Then the conversation turned to living near forests and how to prevent wildfires through using Firewise techniques. Leaves and other forest debris on the forest floor contribute to ground fuel during fire events. Avoid risky behaviors near areas that are fire sensitive, such as outdoor burning and using holiday fireworks. Our homes and other outbuildings are also at risk during a wildfire or forest fire and require adequate protection. Maintain a defensible space between your buildings and the trees for optimum fire safety. Maintaining a clearing of 30 feet around your home is recommended, using fire resistant landscaping materials, avoiding a lot of wood decks and keeping lawns healthy and green.

We then discussed all the ways that the adage “Good fences make for good neighbors” was a good one. Even minimal fencing can prevent well-meaning neighbors from entering your property without permission. Landscaping to create a defensible space around your home can protect you from forest and wild fires and looks nice too.

Composting is the best alternative to managing backyard waste and kitchen food scraps. It reduces the amount of waste you produce and provides a beneficial soil amendment product. There are several Michigan State University Extension educators working across Michigan to provide Michigan Firewise educational programming and assistance. For more information, you can visit the MSU Extension Firewise website and Gardening in Michigan.