Confused about Composting? 9 Common Questions Answered

Daisy Prado, CUESA Staff
January 19, 2018

Composting can be thought of as recycling’s smellier and more complex kin. But as important as it is, it can also create a lot of confusion. Approximately 40 percent of food in the US gets thrown away every year. Although reducing food waste should always be your first goal, composting is a last-ditch effort to put inedible food scraps to good use.

Why is composting important? When those food scraps are sent to the landfill, not only are their valuable soil nutrients wasted, but they can actually cause environmental harm. In the landfill, organic materials decompose anaerobically (without oxygen), releasing methane, a greenhouse gas that is 23 times more potent than carbon dioxide. Landfills account for 34% of methane emissions in the United States, so composting can help to mitigate climate change.

Ten years ago, most of what ended up in the garbage cans at the Ferry Plaza Farmers Market was compostable. Since then, 90% of that waste has changed course as CUESA along with the city of San Francisco embarked on a journey to get to zero waste by 2020.

Today in the Bay Area, you can find three waste bins: a black one for trash, a blue one for recyclables, and a green one for compost. Composting doesn’t have to be smelly or complicated. Here are a few top questions and myths people have about composting.

Let’s start with the basics. What is compost?

Compost is formed when organic matter (material that comes from plants or animals) decomposes aerobically (with oxygen). The resulting nitrogen- and carbon-rich substance can be added to soil for nutrients, to prevent erosion, and encourage the growth of beneficial insects and microorganisms. On farms, compost is an essential ingredient to creating healthy soil and plants, reducing the need for chemical fertilizers and pesticides.

What can I actually compost?

Usually this is summed up to “organic matter,” but the lines can get blurry for what you can and cannot compost. If it is food or a food-soiled paper product, it can go in the green compost bin. Compostable plastics (which need to say “compostable” or have a green stripe, like Greenware) can go in the compost bin, while plastics that aren’t labeled as compostable must go to the landfill. Styrofoam of any sorts does not break down and therefore not compostable. Find a complete list of what’s compostable here.

What do I do with my coffee cup?

Most of the food service ware you find in CUESA’s farmers markets is compostable or recyclable. But coffee cups have been moved to the recyclable category, even if the coffee cup says that it is compostable. Recology recommends that you put cup, sleeve, and plastic lid in blue bin, only after dumping out any remaining liquids. Coffee cups that come from other coffee shops outside of the farmers market or Ferry Building might not be recyclable at all.

What about straws?

Straws are considered to be the worst of the worst from an environmental standpoint; Americans use over 500 million of them every day! Unfortunately, plastic straws aren’t recyclable because most of them are too lightweight to make it through the mechanical recycling sorter, and they are most definitely not compostable. Restaurants such as Tacolicious (at the Ferry Plaza Farmers Market on Thursdays) have taken a stand against this environmental abomination and recently transitioned from plastic straws to paper straws.

Can I compost my meat scraps and dairy?

Yes, meat scraps, bones, eggs, dairy, and seafood can go in the green bin, though be aware that adding any animal products to your compost can make your bin smelly and spawn critters. If you are unsure about which bin a certain item goes into, visit Recology’s “WhatBin” page, type in the item you want to dispose of, and they will tell you which bin it goes into.

Where does my compost go after I put it in the building’s green bin?

After your compost bins are collected, the contents are transported to one of two Recology composting facilities, either outside Vacaville or Tracy. Your composted food waste will go to good use after it is sorted through and treated for any contaminants, then sold to farms, vineyards, and home gardeners as soil amendments.

I created my own compost pile at home and it’s starting to smell bad. What do I do?

There are lots of resources out there, but the general rule is a healthy compost should have much more carbon than nitrogen. If this balance is off, it can cause a sour odor to arise. To ensure that your compost stays healthy and odor-free, consider this ratio: two-thirds brown and one-third green materials. Brown materials, or carbon-rich materials, include twigs, dry leaves, egg shells, straw, fruit peels, and yard debris. Green, or nitrogen-rich materials, include food waste and fresh lawn clippings. For indoor compost bins, using a container with a charcoal filter can help to reduce odors.

I live in an apartment and don’t have a backyard. Can I compost indoors?

Yes! Apartment buildings sometimes offer bins and compostable bags for your composting needs, so be sure to ask your management office first. If they don’t, you can purchase a plastic or ceramic bin at most stores. San Francisco residents can also request one from Recology. The key to composting indoors is ventilation and keeping an optimal wet-dry ratio.

What do I do now with what I’ve composted?

The most popular use for compost is using it as a natural fertilizer. Use your compost to add rich nutrients to your indoor potted plants or lawn. If you want to be eco-friendly by composting but don’t have a place for your compost or if you simply have too much of it at one time, you can always donate it to your nearest community garden. If none of these options work for you, it’s time to head to your apartment building’s green bin to dispose of your compost.

Get more tips about composting and recycling through CUESA’s Waste Wise Initiative.

Photo by Antonio Gravante.