It’s easy to take the sewer system for granted — just dump some stuff down the drain, and it’s gone for good.
But that’s not necessarily true, especially when grease and cooking oils are disposed.
That out-of-sight, out-of-mind attitude has made Thanksgiving a busy day for residential sewer problems.
Pima County, along with the Town of Sahuarita and private-sector partners, collected post-Thanksgiving grease in an effort to prevent sewer-system backups and to put the collected material to good use.
“Over time, grease collects in our pipes,” said Laura Hagen Fairbanks, community relations manager with Pima County Regional Wastewater Reclamation Department.
Hagen Fairbanks said accumulated grease and oil becomes a magnet for other debris and waste, and cause sewer blockages — with disastrous impacts.
“The worst-case scenario is someone’s house is flooded with raw sewage,” she said.
In still-worse cases, long-term dumping of grease down drains can cause larger blockages further down the system, impacting more than a single household.
The Friday grease collection effort brought in 4,400 pounds of spent oil, about 12 barrels full of grease, all of which will be used again. Last year, the county collected about 2,500 pounds on Black Friday.
“All the oil we collect gets recycled into biodiesel,” Hagen Fairbanks said.
Biodiesel, a clean burning alternative fuel made from non-petroleum oils, has been around for some time. In recent years, its use has grown in popularity.
Traditionally, used cooking oils were not used for fuel. Anyone who’s worked in a restaurant knows that companies collect used cooking oils for tallow processors. Most of that oil gets processed for ingredients in livestock feed.
“About 90 percent of oil goes back into the food stream,” said Mike Kazz of Grecycle, a Tucson company that partnered with Pima County to collect the oily Thanksgiving offerings.
Called “yellow grease” in the industry, the cooking oils are strained of food particulates and separated from residual water before being processed into biodiesel fuel.
“In any diesel engine, there’s no conversions required,” Kazz said.
Blends of the fuel vary from 5 percent up to 100 percent biodiesel.
Kazz said the increasing use of oil to make fuel over the past several years has helped create a domestic market that could reduce the need to import petroleum.
In less than 10 years, production of biodiesel in the U.S. has grown from almost zero to more than 700 million gallons in 2008, according to the National Biodiesel Board. That’s the equivalent of about 16 million barrels of oil. It’s impressive growth, but hardly puts a dent in the more than 6.8 billion barrels of petroleum consumed annually in the U.S.
Grecycle processes enough biodiesel to fuel its own small truck fleet. It’s also partnered with the University of Arizona to research more uses for biodiesel.
“It’s valuable to us and it’s valuable to Pima County,” Kazz said.
Proponents say biodiesel is a better alternative than other renewable fuels because it can be used in most diesel engines without modifications.
Because it’s oil-based but not petroleum, biodiesel emits fewer toxins than standard diesel. That’s good for the environment, and potentially good news for the area sewer system, which has seen a multi-year decrease in overflows.
“We do have fewer sanitary sewer overflows,” Hagen Fairbanks said, and she attributes some of the decline to grease collection and other county efforts.
For more info
The National Biodiesel Board
Environmental Development Group
Pima County Regional Wastewater Reclamation Department