The journey of a banana peel: What happens to all that stuff you throw in compost bins in Austin?
Before Sarah Berson's East Austin neighborhood was phased into the city’s composting program, her family would make their own compost. It was a lot of work.
They mixed kitchen scraps — consisting mostly of coffee grounds and banana peels — with leaves in a composting barrel. The barrel needed to be manually rotated to mix the microorganisms with the organic material. Then they had to wait for everything to break down before they could use it. After all that, there were still some issues.
“We were producing way more than we needed,” she said. “And then we would dump it on the garden bed [and] random stuff would grow from the seeds that had been in the compost. So, we’d randomly get like a squash growing.”
Berson said she was excited to completely relinquish composting duties to the city.
“It was just so much maintenance,” she said. “We ended up feeling really grateful when the city …expanded the composting program.”
Now, Berson just has a gallon-sized food waste container on her kitchen counter by the sink. She tosses in her coffee grounds, banana peels, eggshells, veggie scraps and chicken bones. The bin has a lid with a carbon filter to help reduce odor. When it’s full or starts to smell, she empties it into her city-issued curbside composting bin. She’s excited she can compost more things now, too, like pizza boxes.
Thinking about how much work it was to make her own compost, she became curious how the city was doing it and where it ended up. She guessed it might be processed and spread in areas the city is trying to develop into green spaces.
So she asked our ATXplained project about it.
A step toward zero waste
The city’s residential composting program started more than a decade ago and now serves around 210,000 homes. It's part of Austin's zero waste goal to reduce material sent to landfills by 90% by 2040. By the end of fiscal year 2021, the city was diverting only about 42%.
If compostable materials like food waste get tossed in the trash, they not only take up space in a landfill, but they also decompose there without oxygen, releasing harmful methane gas. Instead, this material can be used to create compost that can be added to soil to help it retain moisture and nutrients.
Austin Resource Recovery, the city department that collects the compostable material along with other residential waste, serves single-family homes and multifamily properties with up to four units. But larger apartment complexes, for example, would need a private contractor to provide composting services.
From the households it does serve, ARR estimated it picked up 43,548 tons of curbside compost in fiscal year 2022. (For reference, your car probably weighs between 1 and 2 tons.)
From garbage to compost
The 50 trucks rolling through Austin neighborhoods collecting yard waste bags and the contents of the green bins take them east to Organics By Gosh, a composting company in Elgin. The facility is mostly open land with neat piles of compostable material in varying stages of the composting process.
When ARR trucks arrive, they weigh in, dump their contents onto a pile and then weigh out. The city pays the company about $18 per ton of material it drops off. General Manager Craig Crawford said the company receives about 3,500 tons, on average, per month.
In some of the newest piles, you can easily distinguish yard waste bags from Lowe’s and Home Depot, branches, apples, eggplants and pizza boxes. While the piles don’t really smell, Crawford said they do draw in some visitors, like birds and hogs who help themselves to the “buffet.”
ARR’s composting guide details exactly what can and can’t be composted. Green bins and yard waste bags should contain only food scraps (including spoiled food), yard trimmings, food-soiled paper (including paper cups and take-out containers without plastic or wax coating), and natural fibers like shredded paper, toothpicks and chopsticks.
But other things end up in those piles.
There are no machines or conveyor belts involved in sifting through the piles to pick out unwanted items. Instead, Crawford said, three men go through the piles manually looking for things that don’t belong. They wear bandanas over their faces and bright yellow safety vests as they climb up and down the roughly 20-foot-tall piles.
Crawford said, initially, random items like a mattress or a cooking grill turned up in the city’s collections. While that doesn’t happen anymore, the workers still find the occasional shoe, piece of silverware and basketball. There is also a huge pile of the city’s own green bins that ended up inside the collection trucks.
The bigger issue is contamination from glass and hard plastics because the next step of the process is to grind down the material.
“If the glass makes it through and goes into the grinder, it’ll get ground into thousands of tiny pieces, and it ends up in the compost,” Crawford said. “And if we catch it, we have to get rid of that pile.”
Operations Manager Zach Thomas said the material could be sold at a significant discount as long as the buyer is told about the contamination.
Crawford said people are getting better at not putting glass and plastic items in their green bins. He attributes the improvement to the amount of time the program has been running and ARR's reminders.
After being ground down, Crawford said, the material sits out for 20 to 30 days. It is saturated with water, in part to control the temperature.
“If you were to stick a thermometer deep inside [the pile], it is very very hot,” he said. “And we don’t want them to catch on fire. And the watering process also helps with the compost process as well.”
Thomas said the target internal temperature of the piles is between 131 and 160 degrees Fahrenheit. The high temperature makes it easier to break down things like meat and bones. The heat also kills any viable seeds preventing, say, a random squash from growing wherever the compost is used. But beyond 160 degrees, the beneficial microorganisms would be killed.
The material is then laid out in piles about 5 feet tall called windrows. The piles are regularly “turned” – moving material on the outside of the pile toward the middle where it will decompose more quickly. Turning also fluffs the material, allowing enough oxygen to enter the system and help with the process.
After about 65 to 70 days of the material being laid out in the windrows, you get compost.
According to the Environmental Protection Agency, “green” nitrogen-rich materials — like food scraps and grass clippings — heat up the pile, helping to break down the material. And “brown” carbon-rich materials — like dry leaves and branches — provide food for the microorganisms to consume and digest.
Crawford said the facility could use more food waste in the green bins to balance out the brown material.
A collection of waste
In a warehouse at the back of the property, food from distribution centers that have expired, been recalled or gone out of the acceptable temperature range are dropped off and run through a “depackaging” machine. The machine separates the food (like peanut butter) from the packaging (its jar). The food waste is added to the composting piles. The packaging is recycled or thrown away.
Warehouse manager Matt Walker said when three food distribution centers lost power during the 2021 winter storm, the warehouse received about 60 truckloads of food waste — 30 of which contained bananas.
The company also collects compostable food waste from restaurants, bars and hotels.
Together, food waste from those three sources — residential, distribution centers and businesses — enable the composting operations.
Crawford said the site produces about 3,800 tons of compost each month.
Returning to the earth
The compost is sold as is or mixed with other substances like sand. Crawford said construction companies and large-scale landscaping companies buy 500 to 700 cubic yards of it at a time. It’s also sold to farmers and homeowners.
The company also donates some of the compost to places like Festival Beach Food Forest. The “food forest” sits on two-thirds acre of public city land east of I-35 and just north of the Colorado River. Volunteers maintain the garden, but anyone can harvest the food for free. The garden has many different foods and herbs — like figs, peaches, mulberries, mint and pecans.
“[The compost] was really soft and warm, which is all good signs of healthy compost because it means it’s alive,” Jenna Jasso, who helped create the food forest, said. “And when it has that nice, sweet smell, it means it’s balanced.”
Jasso said the donation enabled them to apply compost under all their tree canopies.
“From the base of the tree, all the way to as far as the branches extend, we covered the ground with compost,” she said. “That helps to ensure that we’re feeding it into the soil that is feeding the roots of that tree.”
So where did Berson’s banana peels and coffee grounds end up?
Perhaps a little ended up just a few miles from her home in an urban forest where people freely pick fruit and hopefully compost the inedible parts to start the cycle again.