Lard-Fired Boiler Cleaner Than Fuel Oil

"Today, the lard produced when processing a pig is used in restaurants, bakeries and cosmetics while the choice white grease is used in animal feedstuffs and as chemical feedstock," says Bruce G. Miller, associate director of the Energy Institute at Penn State. "The market for both edible lard and non-edible choice white grease is changing and Hatfield Quality Meats investigated new options for their products."

A butchered hog is 60 percent meat and 40 percent other products. Of that 40 percent, 20 percent becomes products like processed lard and the other 80 percent becomes animal feed, including choice white grease. In 1998, Hatfield was processing about 7,000 pigs per day averaging 250 pounds per pig. If the markets for lard or choice white grease should substantially decrease, then they could incur heavy costs for waste disposal if alternative uses are not found.

"Currently, all the choice white grease and lard products are being sold at a price higher than the per gallon cost of fuel oil," says Mark W. Badger, director of the analytical research group of The Energy Institute. "It would not be profitable to burn lard now, but Hatfield is looking toward the future."

The researchers, working closely with Hatfield and in John Larsen, Lehigh University, and supported by the Ben Franklin Partnership of the Commonwealth of Pennsylvania, compared the combustion properties of semi-finished and finished lard to No. 6 fuel oil. Hatfield currently has three boilers operating on Nos. 4 and 6 fuel oil in their main processing plant. The research was reported today (Aug. 21) at the American Chemical Society meeting in Washington, D.C.

Pig fat contains essentially no sulfur or sulfur compounds and so produces no sulfur dioxide when burned. The study showed that both pork products produced about one-third the nitrogen oxides produced by No. 6 fuel oil. Because the lards are processed, they produce almost no ash as well. While pig-derived fuels produce slightly less energy per gallon than No.6 fuel oil, they are cleaner. The tests were run on a boiler adjusted for No. 6 fuel oil producing slightly more carbon monoxide from the pig-derived fuels, but this could be eliminated with proper adjustments. The same fuel handling system was used with all fuels.

"Although lard and choice white grease are semi-solid at room temperature, this posses no problem because typically, No.6 fuel oil is heated before burning," says Miller. "We preheated the lards to 120 degrees Fahrenheit and the they became nicely liquid."

In the processing plant, the edible and inedible fats are processed separately. The inedible fat is rendered and becomes choice white grease. The edible fat goes from the cutting room floor to the melt tank, is heated, centrifuged to break it down and liquified in a heat exchanger to remove the solids. This produces semi-finished lard, which is as good a fuel as finished lard. The extra expense of finishing the lard by putting it through a separator that removes small insoluble solids and some of the water would be unnecessary should it be used as a boiler fuel.

"Production at the Hatfield plant produces almost nothing as waste," says Miller. "If the current demographics of lard consumers changes, these products make very good fuel.