San Francisco Fights FOG From Grease Traps

FOG can be a big problem in San Francisco — not the misty kind that famously blankets the City by the Bay, but sewer-clogging fats, oils, and grease. FOG is a sticky problem for the San Francisco Public Utilities Commission (SFPUC), largely because of the many restaurants for which the city is known.

The men and women of SFPUC fight to keep FOG out of the city’s 1,000 miles of combined sewers, which carry 80 mgd of wastewater. They clean out gooey plaque that causes blockages. They clean up FOG-caused sewage backups and overflows. They fix sections of sewer broken as a result of clogs and backups. And they try to convince residents and business owners to take steps to avoid dumping FOG into the system.

And now, the commission uses a new technology to convert grease collected from commercial grease traps into high-quality fuels. The technology produces ASTM-certified biodiesel fuel, a renewable, nontoxic fuel that can be used in any diesel application, from vehicles to household furnaces, without modifying the machinery.

It’s all part of a new, comprehensive FOG-control program that the commission expects to help reduce sewer blockages, save on emergency responses and cleanups, and keep costs down for ratepayers.

Good food, bad clogs

Collection System Division manager Lew Harrison says his department handles about 9,000 work orders each year, about 6,000 of them related to sewer blockages, of which 44 percent are caused by restaurant grease traps. All told, the city spends about $3.5 million per year on grease-related blockages, and that doesn’t include the cost to private businesses and homes.

One reason FOG has been such a challenge is the city’s appreciation of good food. “San Francisco has more than 2,600 restaurants packed into a relatively small geographic area bounded by water on three sides,” says Harrison. “I’ve been told the city is home to more restaurants per capita than anywhere else in the country.”

In any city, restaurant food preparation, cooking, and cleanup generate the vast majority of the FOG. A restaurant that doesn’t follow the best anti-FOG practices and that isn’t equipped with a well-maintained grease trap can send an enormous amount of FOG down the drain every day.

Multiply that by hundreds of restaurants, and the volume of FOG flushed into the sewers adds up in no time. Harrison estimates that 9 million gallons of FOG enters the San Francisco sewer system daily. Once there, it cools, solidifies, clings to the sewer walls, and slows the flow of wastewater.

When wastewater moves slowly, or stops, odors build up. Eventually a heavy blockage causes sewage to back up into streets, commercial buildings, and houses, causing health hazards and costly cleanups and repairs.

Keeping FOG out

The best way to avoid FOG problems is to keep the material out of the sewers. Six years ago, SFPUC started a program to stop FOG at the main source: restaurants. The emphasis is on encouraging owners to collect and recycle as much FOG as possible.

As a first line of defense, restaurants can collect fryer oil in containers. They can also clean pots and pans of grease with rubber scrapers before washing, and collect the scrapings for disposal in the trash.

The next preventive measure is to have a designated sink for washing greasy or oily items, and having that sink drain into a grease trap inside or a grease interceptor outside. Both devices work well if maintained properly and cleaned frequently.

Keeping FOG out of the sewer means extra work and extra cost for a restaurant, so a successful anti-FOG program includes tools to educate owners about how keeping FOG out of the sewers can reduce their risk of costly and unpleasant backups. For the city, eliminating FOG pays off in lower maintenance costs.

Progressive approach

Although the U.S. EPA has mandated FOG pretreatment programs for years, San Francisco started its own largely voluntary program six years ago. In March 2009, the city stepped it up a notch by making participation mandatory for restaurants.

“We realized the financial and work-hour cost that FOG was causing,” says Harrison. “We knew we were spending millions of dollars each year on a problem we could prevent if we approached it the right way.”

The city and the EPA already had some regulations that required restaurants to have fryer oil hauled away, and private haulers were filling that need. Some restaurants were also using grease traps or the larger and more expensive interceptors, but not all were having them serviced properly.

In an area known for environmental awareness and innovation, it seemed natural that the city would find an innovative and progressive solution to the problem. The FOG program combines restaurant operator education with carrot-and-stick regulations.

“You couldn’t find a better place in the country to try out this method,” says Harrison. “People here tend to support environmentally friendly practices and are also more open to unusual ideas than in some other places. But the reality is that no matter how altruistically motivated restaurant owners are, the system also has to make business sense, or they won’t embrace it.”

Prevention first

The first prong of the FOG program is toughening up best-practice requirements, many of which had been voluntary. For example, restaurants are now required to dry-wipe pots and pans and monitor grease hauled away from their businesses.

The FOG program also includes an ordinance requiring restaurants being built or remodeled to install an automatic grease-removal device (AGRD) by 2012. Other restaurants must do so by 2015. Right now, such a system costs about $2,300. SFPUC estimates show that once the systems become more common, competition and volume manufacturing will drop the price to about $1,500.

To help restaurants offset the cost and to help jump-start the FOG program, the city will cut sewer rates for restaurants that install or convert to AGRDs in the next two years. Harrison estimates that the reduced rates will let restaurant owners recover the cost of the AGRD in three years. Revenue the city loses from the lower rates will be offset by lower spending on emergency repairs and clearing of blockages.

The AGRDs will do more than trap the brown grease for conversion to biodiesel. They will also separate and collect food waste, which the city plans to convert to biogas through anaerobic digestion. The biogas will be compressed and used as fuel for vehicles.

Waste to resource

Of more immediate benefit is the grease-to-biodiesel facility, which began producing fuel last November at the commission’s Oceanside Wastewater Treatment Plant. The system was installed there to take advantage of 24-hour staffing, heating systems, and existing transportation corridors.

The system, from BlackGold Biofuels in Philadelphia, Pa., receives grease trap waste delivered by pumping contractors who service restaurants. The pre-fabricated, skid-mounted system easily hooks into the treatment plant infrastructure.

To convert FOG into fuel, the BlackGold system starts by removing water, trash, and grit. It then uses methanol and a catalyst to chemically transform the grease into fuel. And an intensive purification phase follows.

The fully automated, continuous system requires little training to run and operates with minimal staff attention and training. The SFPUC awarded BlackGold sole-source status after the company won a selection competition that included a test conversion of multiple samples of San Francisco grease into biodiesel at the company’s Philadelphia pilot plant, the first of its kind in the country.

The SFPUC uses the biodiesel to fuel some of its vehicles. That means the commission saves on fuel as well as on landfilling of grease. That in turn helps keep sewer rates down for restaurants and other customers.

“When you landfill grease, you are doing a good thing by keeping it out of the sewer where it causes problems,” says Harrison. “But you are still not doing anything useful with it. When you convert the grease to biofuel, you are making it into something beneficial, and you are also helping reduce the rate at which you use up another resource — petroleum. Ultimately, if you convert FOG to more biofuel than you need, a city could develop an income stream by selling it.”

The SFPUC believes grease haulers will be attracted to the BlackGold facility because discharging there costs less than landfilling, and because the site is closer to the central city, saving haulers money on fuel, bridge tolls and other expenses.

Just the beginning?

Down the road, Harrison envisions even bigger benefits. At present, about 9 million gallons of brown grease are discharged into the system per day, and up to 5 million gallons is recoverable, he estimates.

As restaurants come on board, and as the commission gets better at using the recovered waste, Harrison believes enough eventually could be converted to biogas to help fuel the turbines that generate electricity at the wastewater treatment plant, ideally at some point making it self-sufficient.

“If this system catches on across the country with the general public, and people decide they want to have their food and grease waste used for fuel instead of landfill, we might someday be able to take the country’s entire wastewater industry off the grid. That would cut the country’s energy needs by 3 percent.”

The first steps in that journey are taking place now as SFPUC ramps up its new FOG program. Says Harrison, “San Francisco wants to perfect this program, then help lead other cities out of the FOG.”