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Renewable Hydrocarbon By Tina Caparella Biodiesel has been an emerging advanced biofuel in the United States for more than two decades while renewable diesel has only come on the market in recent years. Both are biomassbased diesel fuels that are highly effective in reducing greenhouse gas emissions and providing energy independence. Because of their beneficial properƟes and various state and federal policies and incenƟves, biodiesel and renewable diesel are projected to conƟnue growing in producƟon and consumpƟon. Although both are manufactured uƟlizing some of the same feedstocks, each is unique in producƟon, final product properƟes, and end use. Diesel 101 REG’s renewable hydrocarbon diesel plant in Geismar, Louisiana. At the 2017 NaƟonal Biodiesel Conference nce and Expo held in mid-January in San Diego, California, Dave Slade of Renewable Energy Group (REG) provided a layman’s explanation of what exactly is renewable diesel, or what the industry has renamed renewable hydrocarbon diesel (RHD) to differenƟate it from straight oil products being labeled renewable diesel. Currently there are only two RHD facilities in the United States – REG’s 75 million-gallon-per-year plant in Geismar, Louisiana, and Diamond Green Diesel’s 150 million-gallon-per-year facility in Norco, Louisiana, which is a joint venture of Darling Ingredients Inc. and Valero Energy CorporaƟon. e d y n n ty re gy Similar to petroleum diesel, RHD is a hydrocarbon fuel – hydrocarbons are molecules consisƟng of only carbon and hydrogen (i.e., no oxygen, sulfur, or other atoms) – made from animal fats, used and virgin oils, and other biological feedstocks known as triglycerides. First the fats and oils are pretreated to remove impuriƟes. They then go through hydrotreating, which is reacƟng molecules with hydrogen to remove atoms other than hydrogen and carbon, and isomerizaƟon, which changes the structure of the hydrotreated molecules without changing the number of atoms involved. The next step in the process is fracƟonaƟon to separate the hydrocarbons into finished products – RHD that meets ASTM InternaƟonal D975 standard for diesel fuel, naphtha, and renewable liquefied petroleum gas, which is predominantly propane from the glycerin porƟon of the triglycerides.   By B comparison, biodiesel is a methyl ester este manufactured from the same oils and fats fats (triglycerides) by transesterificaƟon, a chemical che reacƟon with the alcohol methanol. Its resulting products are methyl esters that tha must meet ASTM D6751 to be sold as biodiesel bio and glycerin. One benefit of the RHD RH process is that removal of free faƩy acids ac (FFAs) in pretreatment is not necessary as as it is less sensiƟve to FFAs – unlike in biodiesel bi producƟon – giving animal fat and an used cooking oil an advantage as a lower-lo cost RHD feedstock.   ASTM D975 now specifies diesel fuel must m contain hydrocarbons. Slade shared Dave Slade of REG that that REG’S REG’S RHD RHD specificaspec Ɵon limits are similar to ASTM D975 with a few excepƟons shown in table 1. He stated that RHD is just another diesel fuel but with greater benefits than petroleum, such as reduced emissions, higher cetane (an indicator of combusƟon quality), and lower aromaƟcs and sulfur.   RHD can be used in exisƟng diesel engines without modificaƟon and blended at any level with petroleum diesel or biodiesel. It is approved for pipeline transport as a blend component and included in the Energy Policy Act of 1992 standards to meet a porƟon of the alternaƟve fuel vehicle acquisiƟon requirements. RHD has also been tested by the Environmental ProtecƟon Agency and passes its Clean Air Health Effects tesƟng condiƟons, qualifies for state and federal incenƟves, and reduces nitrogen oxides in diesel engine exhaust. It has an addiƟonal advantage as a potenƟal low-carbon fuel opƟon for aircraŌ. R Table 1. REG renewable hydrocarbon diesel specifications versus ASTM D975 petroleum diesel Current D975 Property REG limit ULSD limit Copper corrosion, max No. 1b No. 3 Sulfur, max (parts per million) 5 15 Aromaticity, max (% volume) 2 35 Cetane number, min 65 40 Cloud point, max (Celsius) <-10 Report *ULSD – ultra-low sulfur diesel 14 February 2017 Render www.rendermagazine.com


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