After eating lunch, students in Oak Park Elementary School District 97 sort their leftover food scraps into compost bins located in school cafeterias. But what happens to those food scraps after they leave the school?
Seven Generations Ahead (SGA) sought to answer that question by following those scraps. Its team recently toured the Willow Ranch Compost Facility, which is operated by Waste Management and located in Lemont, Ill.
Willow Ranch accepts both food scraps and landscape trimmings and transforms them into nutrient-rich compost in just 90 days. Composting involves the same processes that occur in nature when microorganisms and other soil critters consume organic matter as food and break it all down into humus, the organic component of soil. What composting does is control and speed up this process.
Through its Zero Waste Schools Program, SGA supports District 97 waste reduction efforts by providing guidance on operational changes and educating students and staff. While it doesn’t take long for students to learn the routine of sorting, understanding the environmental impact of putting an apple core into the compost bin instead of the landfill bin is where the more impactful learning can happen. To that end, the photos and information gathered by SGA at Willow Ranch will be shared with teachers and used in future educational presentations for students. Students may even be able to take a field trip to the facility.
Here’s now the process unfolds:
Food scraps at Willow Ranch first get mixed with ground-up landscape trimmings. This mixture is placed into windrows (the long piles, about 4 feet high, as shown in the top photo). At least once a week, the windrows are aerated by the yellow machine in the photo above. Temperature is monitored and maintained between 140-150 degrees Fahrenheit to kill off pathogens. (Note: heat is generated by the metabolism of the soil microbes as they eat the organic materials).
After 90 days in the windrows, the compost is screened in the blue machine in the photo below to remove contaminants such as plastics and pieces that didn’t fully decompose.
The pile of finished compost in the photo below is ready to be sold. Waste Management sells it in bulk for $11.50/yd3.
The compost facility is located next to the DesPlaines River so wildlife like the turtle below frequently make their way into the facility. Contamination, such as the plastic in the photo, results from improper sorting upstream (in a school cafeteria or a residential compost bin) and is a challenge for any commercial composting facility trying to make a high-quality finished product. The turtle highlights another reason to prevent contamination-- wildlife often mistake plastics or other pieces of garbage as food or get entangled in it. The hope is that sharing images like this with students will inspire them to sort more carefully.
What are some of the environmental benefits of composting? Composting:
Reduces greenhouse gas emissions: When microbes decompose organics in the low-oxygen environment inside a landfill, they generate methane instead of carbon dioxide. Methane is at least 20 times more potent than carbon dioxide as a climate-changing greenhouse gas (A study from Institute for Local Self Reliance reports that methane emissions from landfills are actually 72 times more potent that carbon dioxide in a 20-year timeframe). Adding compost to soil also improves its ability to store carbon.
Improves soils: Returns nutrients to the soil, helps soils retain moisture, reduces or eliminates need for synthetic fertilizers and pesticides, promotes soil biodiversity, removes soil pollutants
Reduces stormwater runoff and soil erosion
Extends landfill capacity thereby reducing the need for more new landfills
And one more benefit: composting is relatively local. The Willow Ranch Compost Facility is only 25 miles from Oak Park, while the garbage collected in District 97 and the Village of Oak Park is trucked 118 miles away to Waste Management’s Liberty Landfill in Monticello, Ind.