Here's what's happening to all the tree branches piled up on Austin curbs
The winter storm in February loaded trees with a thick layer of ice causing them to bend and break. Since then, tree limbs have lined neighborhood sidewalks, as Austin residents sawed off weakened branches and dragged fallen ones to the curb.
Overall, almost a third of the city’s tree canopy — or about 10.5 million trees — were damaged during the storm, based on estimates from the Texas A&M Forest Service.
So, what happens to all those broken tree limbs now?
Austin Resource Recovery, the city department that is managing the residential cleanup, has about 70 city and contracted crews collecting yard debris from curbs.
Austinites can call 311 to make a request to have their debris picked up. So far, the city has received about 39,000 requests — mostly from areas west of MoPac. The department says while crews will make their way through all neighborhoods, it is using those service requests to determine which neighborhoods and regions are ready for pickup.
ARR expects to complete a first pass through all Austin neighborhoods in the next seven to 10 days, according to Austin Resource Recovery Division Manager Amy Slagle. She said second and third passes are expected to be completed by April 30.
The equipment crews use varies, but you may notice some large double-trailer trucks making their way through residential streets with mechanical arms lifting and loading the large stacks of branches.
Director of Austin Resource Recovery Ken Snipes said at a news conference Wednesday that crews have collected about 100,000 tons of debris already.
"This has been a massive and extensive effort here in the city of Austin," Snipes said. "[It's] much more debris than we've collected at any other time for any other storm events or any other situations that we've had to deal with in terms of recovery efforts."
When full, the trucks will drop off the collected debris at an intermediate point, like the Circle C Metropolitan Park, Bolm District Park or Old Manor Road. Those are not public drop-off sites. Only contracted crews are permitted to unload there.
At the intermediate collection sites, the large branches are ground into a mulch-like substance. That ground-up material is then taken to Austin Water’s Hornsby Bend Biosolids Management Plant in East Austin.
Ian Moede, an environmental program coordinator with Austin Water, said the plant uses the ground-up yard trimmings from ARR as a bulking agent in its composting operation. The facility mixes about one part wastewater sludge from Austin Water treatment plants with two parts ground-up yard waste to make a compost they call Dillo Dirt.
Moede said the compost is sold to agricultural end users, turf growers, landscape suppliers and contractors for the Texas Department of Transportation.
A corner of the Circle C Metro Park is being used as a collection site for storm debris. Large trucks drop of piles of branches which are ground into a mulch-like substance and trucked off to Austin Water’s Hornsby Bend plant in East Austin to be turned into compost. pic.twitter.com/PbxQ04tXwE— Sangita Menon (@sangitamenon) March 1, 2023
Moede said the site produces 30,000 to 40,000 tons of compost a year. The additional ground-up branches they are receiving won’t mean more compost will be produced, though, because the amount produced depends on how much wastewater sludge comes out of the water treatment plants.
Before it’s ready to be sold, the compost is screened to remove a woody material called "overs." Normally those overs are put back into the compost-making process several times before they are finally trucked off to a cement plant to be burned for energy. But with so much freshly ground-up debris coming into the Hornsby Bend plant, Moede said staff will likely send the overs directly to the cement factory instead of trying to feed them back into the compost-making process.
Typically, the site gets about 18,000 tons of ground-up yard trimmings each year. But the plant received more than 12,000 tons of brush in February alone.
Moede said around 2019 or 2020, there were concerns about having enough yard trimmings for Austin Water’s composting operation as demand for yard trimmings increased when Austin Resource Recovery ramped up its food waste composting facility. Moede said they were able to find additional sources at that time.
“So, we were worried at one point about being limited by the bulking agent that we would have, but … we have plenty,” Moede said. “And now we have more than plenty. We have enough that it’s going to last us a long time.”
Moede said Austin Water will store the extra material until it can be used.
“We can store this material on some of our farmland without issue,” he said. “We can leave it there for a pretty long time without changing the quality of the material.”
Snipes said the debris at the Hornsby Bend plant is stored in piles of limited sizes and spaced apart to limit the risk of fire spreading. He said those piles are turned regularly to release heat that builds up within them.
"The process for managing it to prevent fires doesn't change," he said. "We just have more rows than we would have had ordinarily."