BioCycle July 2010, Vol. 51, No. 7, p. 56
Small companies in California and North Carolina are recycling used cooking oil and other types of yellow grease – as well as brown grease and FOG – into biodiesel.
Diane Greer

WHEN searching for a more sustainable source of biodiesel for his nascent biofuels distribution business in 2002, Kumar Plocher, president of Yokayo Biofuels in Ukiah, California, discovered a rich source of oil in his local community – used cooking oil. At the time the company was distributing biodiesel made from soybean oil.
Over the next four years, Plocher started a used cooking oil collection business and built a small plant to convert it into biodiesel. Today the company collects used cooking oil from more than 1,000 area restaurants and food services facilities to produce nearly 500,000 gallons of biodiesel annually.
Across the country, small companies like Yokayo, New Leaf Biofuel in San Diego, California, and Piedmont Biofuels in Pittsboro, North Carolina, are recycling used cooking oil and other types of yellow grease into biodiesel. Initiatives are also under way to develop technologies to convert brown grease collected from restaurant grease traps and FOG (fats, oils and grease) recovered from sewers and wastewater treatment plants (WWTP) into biodiesel.
In 2009, the U.S. produced 545 million gallons of biodiesel. Seventy-seven percent was made from virgin oils such as soybean, canola, cottonseed and palm, 17 percent from animal fats and 6 percent from yellow grease (used restaurant fryer oil).
Current production of biodiesel from waste oils and greases represents just a fraction of what is possible given available feedstock. The U.S. EPA’s Office of Solid Waste estimates one billion to three billion gallons of waste greases are produced annually. These include yellow grease, brown grease caught in grease traps, animal tallow, fish oils and FOG recoverable from sewer pipes and WWTPs.

BENEFITS OF WASTE DERIVED BIODIESEL
Biodiesel produced from waste oils and grease offers an attractive alternative to conventional diesel. Like biodiesel made from virgin oils, waste oil biodiesel exhibits performance characteristics similar to petroleum diesel while emitting less carbon monoxide, particulate matter and volatile organic chemicals that cause smog and health problems. Burning 100 percent biodiesel (B100) eliminates all sulfur emissions.
A recent EPA study found biodiesel produced from waste grease resulted in an 86 percent reduction in lifecycle greenhouse gas emissions compared to conventional diesel, says Olof Hansen, environmental protection specialist at the EPA. In comparison, soybean-based biodiesel resulted in 54 percent less lifecycle greenhouse gases. (These analyses look at all the greenhouse gas emissions related to the full fuel cycle, from feedstock generation and extraction through production, distribution and use.)
In urban settings, FOG is a “crop” to be harvested and used locally in a sustainable cradle-to-cradle manner, Hansen explains. “It is created locally in large quantities at universities, POTWs [publicly owned treatment works], military bases and corporate campuses where demand for fuel is high.”
Lower cost for these feedstocks is another advantage. “Used oils and greases tend to be available at lower costs than first use or food grade oils,” says Jon Van Gerpen, University of Idaho professor and biodiesel expert. Lower feedstock prices are extremely important to an industry where 70 to 85 percent of production cost is the feedstock.
Lower feedstock prices are moderated by competing uses. Typically, used cooking oil is collected by renderers for use in animal feed and industrial products. “The price is not extremely low,” Van Gerpen says. “It is just that it’s priced at a discount to first use oil.”
Piedmont Biofuels started producing biodiesel using virgin soy oil in 2006. “When soy oil became too expensive we converted to waste poultry fat,” says Lyle Estill, cofounder of Piedmont. “When waste poultry fat became too expensive, we converted to used cooking oil and that is where we are now.”

BIODIESEL PRODUCTION
Fats and oils are mainly composed of three fatty acid molecules connected by a glycerin molecule. Biodiesel is typically produced via a transesterification process that chemically reacts the oils or fats with an alcohol, like methanol, using an alkaline or acid catalyst to speed the reaction. The chemical reaction splits the oil, combining a fatty acid molecule with a methanol (alcohol) molecule to form methyl ester or biodiesel. The glycerin molecule, separated in the reaction, is a by-product of the process.
Processing used cooking oils into biodiesel is slightly more difficult because the feedstock contains water, food particles and free fatty acids (FFA). FFAs are formed when the virgin vegetable oil is cooked, causing some oil molecules to break apart, Plocher explains.
During transesterification, FFAs combine with the catalyst (lye) to form soap. Soap is also formed when water in the feedstock causes the fats and oils to hydrolyze. Soap slows the reaction, reduces yields and must be removed to meet ASTM biodiesel standards. Extra processing steps to deal with contaminants, water and FFAs increase costs. “But the fact that you can get the feedstock at a lower price more than offsets the higher processing costs,” Van Gerpen says.
Yokayo is collecting over 40,000 gallons of oil to make about 34,000 gallons of biodiesel each month. The feedstock contains two to seven percent FFA and up to 10 percent water/solids. The solids, such as food scraps, are removed by filtration. Dewatering equipment decants off the water. This equipment, designed to rendering company specifications, leaves up to 2 percent of the water in the oil. “We are trying to get that down to 0.1 percent dry or better because water in our process really affects the yield of the finished fuel,” Plocher explains.
New Leaf, which collects used cooking oil from about 1,000 restaurants in the San Diego area, pretreats its feedstock using an acid esterification process to remove FFAs. (Feedstock with very low FFAs do not require pretreatment.) The oil typically contains 20 to 30 percent water and 5 percent FFAs, says company CEO Jennifer Case.
Acid esterification reacts the oil with an alcohol, like methanol, in the presence of a strong acid catalyst such as sulfuric acid, to convert FFAs into biodiesel. The fats and oil in the feedstock are then converted to biodiesel using a standard tranesterification process. Once the transesterification is completed, glycerin produced by the process is separated from the biodiesel. The resulting biodiesel contains impurities such as soap and residual amounts of glycerin, methanol and catalyst.
Yokayo uses three water washes to remove the impurities. (The contaminants more readily dissolve in water than biodiesel.) A chemical, such as phosphoric acid, is typically added to the second wash to facilitate soap removal.
Glycerin produced by the process is sold to a rendering company that refines it for sale to commercial markets. Wastewater from the wash process, which contains residual methanol and biodiesel, is disposed.
Yokayo is currently exploring options for removing residual methanol and biodiesel from the wastewater so it can be used for irrigation. “It has a value as liquid fertilizer since is contains potassium phosphate,” he explains Plocher.
New Leaf employs a flocculant to remove impurities, eliminating the wastewater stream. Unused methanol is recovered throughout the process. Glycerin is sold to a broker for further refining. The only waste is food scraps removed from the oil prior to processing, Case explains.

SUPPLY CHALLENGES
Finding and collecting large volumes of used cooking oil presents challenges. Piedmont originally produced 1.3 million gallons of biodiesel annually from virgin feedstock. Now it produces about 20,000 gallons from used oils. “You can’t collect a million gallons from the back of restaurants,” Estill explains.
New Leaf invests considerable time convincing restaurants to use its oil collection service and then keeping them on board once they become customers. “The challenge is keeping the oil that we already have coming in and growing,” Case says.
“Competition for the grease has increased manyfold since the advent of commercial biodiesel,” Plocher says. Renderers and collection companies that do not pay oil suppliers are now finding themselves at a competitive disadvantage in areas with biodiesel companies that pay for the oil.
New Leaf faces stiff competition from renderers that collect used oil in San Diego. “There is a lot of theft when oil prices are high,” Case says. New Leaf’s oil storage tanks at customer sites have been vandalized. One thief used a hacksaw to chop a hole into the $500 tank to steal oil.
The biggest challenge facing the biodiesel industry is the price of conventional diesel. “There was a big boom in converting waste grease when fuel prices were about $4 per gallon,” Hansen says. “Then in 2008 gas and diesel prices tanked and the economic driver was not there anymore.”
Compounding the problem is uncertainty with regard to fate of the $1 a gallon biodiesel blending tax credit, which expired in 2009. Reinstatement of the credit was passed by the U.S. House of Representatives in May but is still under consideration by the Senate. “No one is going into biodiesel until the $1 [tax credit] gets sorted out,” Estill says.
In terms of product marketing, Yokayo distributes its own fuel to wholesale (like the Biofuels Oasis in Berkeley) and retail customers. New Leaf sells its fuel to Pearson Fuels, which has service stations around the San Diego area. Piedmont sells to petroleum marketers who blend the fuel with conventional diesel.

BROWN GREASE AND FOG
Faced with lower petroleum prices and higher feedstock costs, biodiesel producers are looking to less expensive, higher FFA feedstock, such as brown grease collected from grease traps and FOG recovered from sewer systems and WWTPs. “The future of biodiesel is going to come from deeper in the waste stream,” Estill says.
Brown greases and FOG contain high percentages of FFA and are often contaminated with water, trash, food waste and unknown materials. “Oftentimes the problem with brown grease is that you are not sure what is in there,” Van Gerpen says. Anything flushed down the drain, such as cleaning products, cooking materials and even sewage can become entrained in the grease.
Typically brown grease is vacuumed out of grease traps, designed to prevent grease from getting into the sewer system. The waste is trucked to WWTPs where haulers pay to dispose the material. WWTPs extract and treat the water in the waste. The remaining waste is processed via anaerobic digestion, incinerated or sent to a landfill.
Improperly disposed grease gets flushed down drains and attaches to the walls of sewer lines, eventually clogging sewer pipes. San Francisco estimates that about four million gallons of grease ends up in the City’s wastewater system annually.
Collecting the grease to make biodiesel before it gets into the sewers could result in substantial savings for municipalities. FOG clogging city sewer pipes is responsible for 80 percent of the sanitary sewer overflow events in the U.S., Hansen says. The San Francisco Public Utility Commission (SFPUC) estimates that grease-related service calls cost the city $3.5 million annually.
New technologies are under development to cost-effectively convert brown grease and FOG into biodiesel. San Francisco’s Oceanside Water Pollution Control Plant has installed equipment to convert these sewer greases into biodiesel using technology and equipment from Philadelphia-based BlackGold Biofuels. Final commissioning and optimization of the facility is underway. Once optimized, the plant is expected to produce 100,000 gallons of biodiesel from 125,000 gallons of dry (dewatered) grease. Plans include using the fuel in city vehicles.
BlackGold CEO Emily Landsberg sees an unmet need in the wastewater industry for reliable, profitable and environmentally responsible solutions for sewer grease disposal. “There is a trend away from just throwing it away to resource recovery.”
According to Landsberg, the company’s proprietary FOG-to-Fuel® system “processes anything from 0 to 100 percent FFA without changing operating conditions, catalysts or reagent ratios. That allows us to handle the high variability that is characteristic of sewer greases along with other high FFA feedstock and conventional feedstock in the same process.”
The technology performs esterification and transesterification simultaneously in a single process without contaminating the fuel with soap. Pretreatment is more extensive than conventional biodiesel technology with processes to separate the water and trash solids from the FOG. The backend purification process involves several steps to ensure removal of all contaminants. Methanol used by the system is recycled. Small amounts of water created by the process are sent to the headworks of the WWTP.
Process by-products include 25,000 gallons of biobased #4 and #6 fuel equivalent and glycerin. The glycerin, which is not commercial grade, can be used to increase biogas production in anaerobic digesters, as a fuel or as a carbon source for denitrification. BlackGold is targeting water utilities in metropolitan areas or companies capable of consolidating about 400,000 gallons of FOG a year. “These are regional projects where we consolidate all the waste for a region at a single location we call a ‘greaseshed’,” Landsberg explains.
Meanwhile, Piedmont Biofuels is piloting an enzymatic biodiesel process developed in partnership with the Biofuels Center of North Carolina, Novozymes, and the Chatham County Economic Development Corporation. The new technology, which performs esterification and transesterification simultaneously, has the potential to increase yields, decrease wastes and process higher FFA feedstock, Estill says. Ribbon cutting for the new facility is in mid-July.

Diane Greer is a Contributing Editor to BioCycle.