Overview and Definition
Composting is a natural process that turns organic materials into a conditioner for soil. As an organic-matter resource, compost has the unique ability to improve the chemical, physical, and biological characteristics of soils.
Compost is produced through the activity of aerobic (oxygen requiring) microorganisms. These microbes require oxygen, moisture, and food in order to grow and multiply. When these factors are maintained at optimal levels, the natural decomposition process is greatly accelerated. The microbes generate heat, water vapor, and carbon dioxide as they transform raw materials into a stable soil conditioner.
Compost can be produced from many “feedstocks” - raw organic materials, such as leaves, manures, food scraps, wet/soiled papers and certified compostable products. State and federal regulations exist to ensure that only safe and environmentally beneficial composts are marketed.
“Biodegradable” and “Compostable”
You may remember from high school geometry class that while every square is a rectangle, not every rectangle is a square. That’s a lot like the difference between the terms “biodegradable” and “compostable”. While everything that is compostable is biodegradable, not everything that is biodegradable is compostable.
Technically speaking, lots of things are biodegradable. That is because the term “biodegradable” has no time frame attached to it, meaning that if a given material will eventually break down, it can be described as biodegradable. The term “compostable” does have a time frame attached to it, though that time frame is defined by each individual composter and his or her specific operational requirements. Generally speaking, most composters would like the material they allow into their facilities to break down in fewer than 80 days.
Composting in the United States
According to the EPA’s 2015 data on Municipal Solid Waste (MSW) generation, Americans composted 8.9% of all the waste we generated. Compare that with 52.5% for Landfill, 25.8% for Recycling, and 12.8 % for Combustion with Energy Recovery.
In the EPA data, composted material is broken out into two main categories – yard trimmings (think leaves, cut grass, etc ) and food. In 2015, Americans generated almost 35 million tons of yard trimmings, and composted 61.3% of it. Contrast that with generating over 40 million tons of food scraps and composting only 5.3% of it!
Lack of Infrastructure for Food Scraps
Just as with traditional recycling, composting rates depend greatly on the infrastructure available, meaning how many facilities are in place to accept compostable materials for processing. A 2017 study conducted by BioCycle determined that there were 4,713 total compost facilities in the United States. Of those 4,713 facilities, 57% accept yard trimmings only, which helps explain why we see the number we do for total tons of yard waste composted. 5% accept yard trimmings and food scraps only, and another 13% accept “Multiple Organics”, which includes food scraps.
Another layer to the infrastructure issue is collection. In order for organics to be diverted from landfills, we need collection and transportation infrastructure to get those organics to composting facilities. This is true for commercial collection as well as residential (curbside collection). While access to collection infrastructure is expanding, it still lags well behind where traditional landill and recycling streams are.
The Role of Compostable Packaging
Studies have shown that the use of compostable packaging in a foodservice environment will increase the amount of food scraps they are able to capture and eventually send to a composter. This makes more sense if you picture a waste station in a foodservice environment that uses takeout packaging (which in the United States is a lot.). If patrons are able to deposit food scraps and packaging in one bin the accepts both materials, there is actually a chance that the food scrap portion will be diverted from the landfill. One of the keys to this is that food scraps (think leftover nachos in a container or a half-eaten pizza in a box) are a contaminant in traditional recycling streams. Without the compost part of the waste diversion system, all of the food scraps and packaging are lost to the landfill.