Ask NRRI

Dear NRRI Experts,
"What’s the best, most environmentally-friendly, way to compost kitchen scraps and yard waste?"

NRRI Scientist Cindy Hale answers:

We recommend that outdoor composters use a traditional backyard pile (or a compost barrel) that is turned and watered regularly. This activates the natural fungi and bacteria which heats the piles over 110 degrees, killing any earthworms or egg cocoons that may be in the pile.

Some people want their compost in weeks instead of months and vermicomposting (with worms) is a way to do that. But remember, all earthworms are exotic species here (more details at www.greatlakeswormwatch.org) so it’s technically illegal to knowingly introduce them into this region if they’re not already established. A standard "hot" compost pile is very effective and doesn’t have unintended consequences — loosing invasive earthworms.

If you compost outside in a backyard pile, rather than a container of some kind, and if earthworms are present in your yard, they will probably find their way there and live on the edges very happily. I worry less about this scenario because they won’t survive in a well-managed "hot" compost. However, you should never add any earthworms to your outside compost intentionally. Ordering online compost worms could result in local invasions of especially damaging Asian worms in the genus Amynthas.

Apartment and condo dwellers like vermicomposting because they don’t have the backyard space. We recommend that they freeze the vermicompost before they introduce it to an outdoor environment. That would kill the worms and their egg cocoons.