Top: Aerial view of the Wasatch Resource Recovery (WRR) facility for food waste preprocessing and anaerobic digestion, located adjacent to the South Davis Sewer District wastewater treatment plant. Inset: Momentum Recycling food waste collection vehicle (top right) and residential food waste containers (lower left). Photos courtesy of WRR and Momentum Recycling
Nora Goldstein
In November 2021, Momentum Recycling began a 6-month food waste collection pilot in a Salt Lake City, Utah neighborhood. Founded in 2008, the full service zero waste company offers recycling and food waste collection services to the residential, commercial and institutional sectors across the Wasatch Front (the north-south area from Brigham City to Provo and including Salt Lake City). The goal of the pilot was to assess if Momentum Recycling could offer a service on a permanent basis by measuring the level of participation, households’ willingness to pay for the service after the pilot, the quantity of food waste collected, and satisfaction with the two types of collection containers offered — a 16-gallon cart and a 5-gallon bucket. Over 700 households in the pilot neighborhood expressed interest, and ultimately, following the pilot, between 200 and 250 subscribed to the collection service, which accepts all food waste, as well as fats, oils and grease (FOG).
“We went into it assuming food waste needs to be collected weekly, which is the case, and learned that while the 16-gallon cart was more efficient for tipping into our vehicle, households generally preferred the 5-gallon bucket,” explains John Lair, Momentum Recycling’s President and CEO. “There was resistance on the part of the households to add another cart, plus the cost was higher for the larger container. After getting feedback that the lids on the original buckets were difficult to remove, we switched to 5-gallon buckets with a screw-on lid.”
Residential customers are required to put food scraps in compostable bags.
The company considered the pilot a success, but waited until 2023 to expand the program due to supply chain disruptions caused by the pandemic for collection vehicles, and a shortage of drivers. The 2023 expansion covered the northeast quadrant of the Salt Lake City metro area. The plan in 2024 was to expand southward, but changed when Momentum Recycling was approached by the Park City Community Foundation (PCCF), which had started a Zero Food Waste Initiative for households in Park City. The initiative includes a residential food waste collection program. “The PCCF reached out and proposed an incentive program to offer to single-family households in specific zip codes in the city,” says Lair. “The first 1,000 homes to sign up received the first month of service free and didn’t pay an activation fee. Even though it wasn’t in our plans, we decided to expand there in 2024. This year, our goal is to build route density in the neighborhoods we currently service. We have about 1,100 residential subscribers in total. About two-thirds are using buckets and one-third have carts. All customers are required to collect food waste in compostable bags. We supply bags from EcoSafe Zero Waste.”
No municipalities in the Salt Lake City region offer residential food waste collection, nor have any reached out to Momentum Recycling about providing service. “We always make sure we have permission to collect food scraps in their jurisdiction and have long-standing relationships with all of them for recycling services,” he adds. “Essentially, the municipalities support us providing the service but as of yet, they don’t want to be involved.”
Collection Logistics
Momentum Recycling began offering commercial and institutional food waste collection when the company started in 2008. Service was limited to vegetative residuals (green waste) because the two composting operations in the region did not accept proteins, fats, oils and grease. About 95% of the company’s customers for this service were grocery stores, where separating vegetative waste from animal proteins could be done fairly easily. Then, in 2019, Wasatch Resource Recovery — a food waste preprocessing and anaerobic digestion (AD) facility in North Salt Lake City — opened its doors. “That changed the game radically,” Lair recalls. “We were able to pivot from vegetative green waste only to all food waste streams. In 2018, we collected 1,258 tons of green waste only. In 2019, the tons collected increased to 2,000, and by 2024, we were collecting 6,000 tons a year.”
In addition to its own accounts, Momentum partners with local solid waste haulers whose customers want to recycle their food waste but the hauler doesn’t offer the service. It will also collect recyclables if the hauler doesn’t offer that either. Roll-off containers and compactors for food waste are available, along with carts. The client base includes restaurants, hotels, schools, convention centers, and grocery stores. Momentum uses rendering-style trucks for collection; filled containers at the rear of the vehicle are emptied into the top of the truck. For residential food waste collection, Momentum has Class 5 and 6 pickup trucks with a specialized food waste collection body mounted to the chassis. The trucks, which are equipped with cart tippers, optimize collection in mountainous areas where roads can be tight and four-wheel drive can be necessary.
Wasatch Resource Recovery
The Wasatch Resource Recovery (WRR) facility is a joint venture between a private company and the South Davis Sewer District. Sewer District staff operates the WRR AD facility, which is adjacent to the municipal wastewater treatment plant. The original facility includes two 2.5-million-gallon continuous stirred tank reactors (CSTR), a tank to receive fats, oil and grease (FOG), and a hydrolysis tank that feeds the digesters, which operate at mesophilic temperatures. Biogas is conditioned and compressed into renewable natural gas (RNG), which is fed into the natural gas grid operated by Enbridge.
Incoming food waste is received in four ways, explains Barrett, WRR’s Resource Recovery Procurement Manager:
- FOG from grease traps and a pig farm arrives in tanker trucks and is pumped into the FOG tank
- Liquids, e.g., milk, whey, meat slurry, brewery waste from area food processors can go directly into the digesters
- A loading dock where pallets of boxes containing soda, milk cartons, cereal, flour, sugar, etc. are pulled off of trucks
- A tipping floor where trucks tip loose loads of food waste
Momentum Recycling tips a loose load of food waste inside Wasatch Resource Recovery’s receiving building. Image courtesy Salt Lake Tribune
Residential drop-off site at WRR. Photo courtesy of Wasatch Resource Recovery (WRR)
The facility received close to 200,000 tons of food waste in 2024, or roughly 750 tons/day. The majority comes from food distributors and manufacturers. The liquid waste is from food manufacturers, and makes up about 45% of all feedstocks received. Packaged food comprises about 25-30% of the flow, but that volume is increasing, says Barrett, who adds that the facility is accepting less FOG currently due to the quality. WRR also has three food waste drop-off sites for households — one at the facility and two at grocery stores. Only source separated food waste is accepted.
Facility Upgrades
To expand food waste processing capacity, WRR is installing a third digester tank within the next 16 months. Having a third tank will also enable operators to clean out one tank while the other two continuing operating. “Currently, tank cleaning is hindered as we have to keep both in operation to process the volumes received,” notes Barrett. “That has created circulation issues within the tanks. We will be taking one tank off line this month to clean out, and then once that is operating again, shut down the other for cleaning and maintenance.”
Mavitec Paddle Depacker awaiting installation at WRR. Photo courtesy of Mavitec B.V.
WRR also is adding a second depackager this spring. It procured a Mavitec Paddle Depacker equipped with a twin-screw hopper system that feeds the unit. Throughput capacity is approximately 15 tons/hour, depending on the input material. A heavy-duty piston pump transports the slurry to the digester facility. “The original equipment limits our ability to depackage items like cottage cheese, sour cream and yogurt because it shatters the packaging into small plastic pieces that make their way into our digestate product,” says Barrett. “Mavitec’s design compresses the packaging to release the contents in a way that doesn’t cause shattering.” Digestate from the tanks is dewatered with a screw press. Solids are picked up weekly and land applied by a farmer who is growing alfalfa. The effluent from dewatering is routed to the wastewater treatment plant next door.
