|Simplified refinery pathway for hydrogenation of vegetable oil. Click to enlarge.|
ConocoPhillips has begun commercial production of renewable diesel fuel at the company’s Whitegate Refinery in Cork, Ireland.
The production process, developed by ConocoPhillips, hydrogenates vegetable oils to produce a renewable diesel fuel component that meets European Union standards.
The refinery is producing 1,000 barrels per day (42,000 gallons US) of renewable diesel fuel for sale into the Irish market. The fuel, with vegetable oil as the feedstock, is produced using existing equipment at the refinery and is blended and transported with petroleum-based diesel.
The ConocoPhillips process can also be used to convert animal fats and oils to renewable diesel fuel.
ConocoPhillips developed the production process and conducted a successful test run at Whitegate last year. Soybean oil will be the primary renewable feedstock used, although the plant can also produce renewable diesel using rapeseed oil and other vegetable oils.
According to the UK Petroleum Industry Association, of which ConocoPhillips is a member, the specific chemical structure of the paraffinic hydrocarbons produced by the hyrdogenation of vegetable oils is defined by the natural oil source. Rapeseed oil (RSO) feedstock, for example, produces mostly C16, C18 and C22 molecules (diesel fuel is a complex mixture of compounds, mostly paraffinic, naphthenic and aromatic hydrocarbons from C10 to C22).
The hydrogenation of vegetable oils can be carried out by using the oils as feedstock to a refinery distillate hydrotreater. The product of vegetable oil hydrogenation is a liquid hydrocarbon mixture similar to diesel fuel components, and is high cetane, zero aromatic and sulphur free.
The precise value of the energy input and therefore the greenhouse gas emissions will be dependent on the oil that is being processed and the set-up of the refinery unit. Results from trials carried out using rape seed oil (RSO) as a feedstock to a high-pressure hydrotreating unit show that the hydrogenation of natural oil delivers a small reduction in GHG emissions compared with the esterification and blending process, according to the UKPIA.
Neste Oil is aggressively developing its own hydrogenation process for vegetable oils and fats—NExBTL—as a second-generation biofuels solution. (Earlier post.)
In 2005, the British government issued a tender to encourage refineries or other companies to investigate the use of hydrogenation as a means of producing renewable fuels. (Earlier post.)