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How Does Composting Work?

While not as catchy as the three R’s (reduce, reuse, and recycle), there’s another great way we can live a more sustainable lifestyle and support our planet: composting.

While we can (and should) start by turning our discarded fruits, vegetables, and yard trimmings into nutrient-rich material that can support healthy soils, composting doesn’t end there. We can compost much more than that as this article will demonstrate.

Food Waste in America

The Problem of Food Waste in America

The problem of food waste is staggering. According to the Food and Agriculture Organization (FAO), if global annual food waste was a country, it would equal the world’s third-largest greenhouse gas emitter.  

In the U.S. alone, around 133 billion pounds of edible food ends up wasted every single year. This means we throw away around 30 to 40% of our food supply. This costs Americans an astonishing $161 billion according to the USDA.

Food waste makes up roughly 24% of the waste stream that enters our landfills, higher than any other single material. Fortunately, composting can help us save money, preserve resources, and support our planet. What's more is that food waste is just one thing that can be transformed into a valuable resource. 

What is Composting? How Can it Help?

How exactly does composting work? Let’s start with a definition of the final product, courtesy of the U.S. Composting Council:

“Compost is the product manufactured through the controlled, aerobic, biological decomposition of biodegradable materials.”

Finished compost or "humus" is a dark, nutrient-dense earthy material that can be used to grow plants or improve soil health. How do we get there? Let’s take a look at the process of turning organic waste into finished compost.  

The process of composting

There are a few elements required for the process of composting: 

  • Organic matter including food scraps/leftovers, grass clippings, raked leaves, etc.
  • Soil or another source of microorganisms
  • Water 
  • Air and oxygen

In a well-managed compost system, microorganisms in the soil consume organic materials. This breaks them down into humus that is rich in soil-boosting, inorganic nutrients like potassium, nitrogen, and phosphorus.

Spoiled fruit and vegetables in compost pile

Home vs. Commercial Composting

It’s important to realize that organic or natural materials will eventually decompose on their own. When we compost, we're just speeding up the decomposition process by creating an environment with microorganisms and adequate water and temperature conditions. The faster and more efficiently we recycle organic waste in controlled environments, the faster we can access the finished compost. 

Depending on the type and volume of organic material available, the compost process can occur in either home or commercial environments. 

Home Composting

Using a backyard compost tumbler, bin, or heap, home composting transforms organic waste like food scraps and yard waste into nutrient-rich humus. 

A home composting system requires three basic ingredients: browns (carbon rich dead twigs, leaves, and branches); greens (nitrogen rich food waste, coffee grounds, and grass clippings); and water.

Given the temperature limitations of home compost systems, certain items might not fully biodegrade. Also, there are other factors to consider like space and potential issues with pests. This makes commercial composting a better option for many consumers, especially businesses like restaurants looking to compost

Commercial Composting

In an industrial composting facility, the conditions are right for the rapid biodegradation of many types of organic material. Using a multi-step process, ideal conditions are created regarding particle size, water, air, and carbon to nitrogen ratios.

Commercial composting is the best way to transform a wide range of organic matter into finished compost. This includes compostable food packaging, meat, dairy, bones, food oils, and more.

food in a compost pile

Common (and Uncommon) Items that Can Be Composted

As the number of items that can be composted increases, we see an increase in composting efforts. These are happening at the federal, state, local and individual levels.

Traditionally, the following items could be composted (in a home compost bin):

  • Fruit and vegetable scraps
  • Coffee grounds
  • Teabags
  • Grass clippings & dead leaves
  • Newspaper
  • Paper napkins
  • Printer paper
  • Cardboard (free from plastic & tape)
  • Sawdust or wood shavings
  • Eggshells*
  • Cooked grains (rice, pasta, bread, tortillas)*
  • Spoiled food (excluding animal products)*

*May lead to pest problems

With the help of commercial composting systems, however, traditionally difficult items can also be effectively transformed to nutrient-rich humus:

curbside compost program

How Does Composting Work to Support a Healthy Planet?

The number of compostable items in our lives is on the rise. Since more people are sipping coffee out of compostable cups and dining from compostable bento boxes, we’re also seeing an increase in composting programs and facilities. And cities and towns are getting on board.

In 1996, San Francisco became the first U.S. city to establish a citywide food scrap composting program. Currently, they recycle and compost roughly 80% of their waste! Since then, other cities like Portland, Oregon, Boulder, Colorado, and Seattle, Washington have followed suit. Others have begun trialing curbside compost pickups or have established drop-off composting locations.

But, we still have a way to go. In the U.S., our composting rates hover between roughly 6% and 8.9%. Through education and increased access to commercial composting services, we can reduce the amount of trash that ends up in American landfills by at least 30%. When you use compostable materials and send them to appropriate facilities, we can all support our planet.


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