Renewable diesel is an alternative fuel produced from vegetable oils and animal fats. Because plants produce oils from sunlight and air, and can do so year after year on cropland, these oils are renewable. Animal fats are produced when the animal consumes plants, plant oils and other fats, and they too are renewable since they are grown using carbon dioxide from the air. This fuel offers advantages over other alternatives. Besides being renewable, it can replace traditional gasoline and diesel, is energy efficient, and can be readily integrated into fuel supply systems.

Renewable diesel also produces less air pollution than petroleum based diesel and can help rein in greenhouse gas emissions.

In December 2006, ConocoPhillips’ Whitegate refinery in Cork, Ireland, began commercial production of renewable diesel to increase the use of energy from forestry, agricultural and waste materials. The European Commission’s 2003 rule, EC/2003/30, mandated that Member States must meet a target of 5.75 percent market share for biofuels or other renewable sources in their overall transport fuel supply by 2010, with the figure rising to 10 percent by 2020.

Whitegate refinery now produces 1,000 barrels per day (150,000 liters) of renewable diesel for sale into the Irish market. Ireland is the third-largest selling market in Europe for cars that run on biofuel – after Sweden and France. Car retailers expect this figure to grow year-on-year as fuel availability improves and as Ireland’s new vehicle registration tax and emissions tax make eco-friendly cars, like flexible-fuel vehicles, more attractive. The reductions in hydrocarbon-based emissions also will contribute to Ireland’s progress in meeting carbon dioxide emissions standards required under the Kyoto Protocol.

In 2002, the Bartlesville Emerging Technology group, in partnership with research and development (R&D) and Fuels and Regulatory Affairs, initiated the idea of renewable diesel as a biofuel alternative. “The question at the time was – can we produce a quality product at an economic price and be allowed to sell into the marketplace?” said Scott Mason, ConocoPhillips’ business development director, advanced biofuels.

“Testing at lab scale was done on hydrodesulfurization units with renewable feedstocks, such as soybean oil, rapeseed (canola) oil, beef tallow, restaurant grease, sewer grease and palm oil,” Mason said. “We tested many and finally settled on soybean oil, the main reason being that more soybeans were then grown throughout the world than any other renewable feedstock. Ships sail around the globe filled with them. And soybean oil was more economic than rapeseed oil, another leading renewable feedstock.” 
 

FAME HAS DOWNSIDES

 
A competing technology using renewable feedstock produces biodiesel, also known as FAME (fatty acid methyl ester). This process produces biodiesel by converting vegetable oil or animal fats through a chemical process called transesterification.

Biodiesel is chemically distinct from petroleum diesel or renewable diesel and is typically blended with petroleum diesel. In short, FAME is biodiesel; hydrotreating produces renewable diesel, which is diesel fuel with renewable content.

Compared to FAME, hydrotreated renewable diesel produces less byproducts and results in higher energy density, improved cold flow properties and better fuel stability. Biodiesel cannot be shipped by pipeline; it must be trucked or railed. Renewable diesel can go by pipeline to fuel suppliers, resulting in reduced costs.

After successfully hydrotreating soybean oil feedstock at R&D, the next step for Mason and his team was scaling up from laboratory to industrial base for real-world testing. Whitegate was chosen after a wide search.

“At the time, we had the facility and infrastructure and a serious reason to start making the fuel,” said Liam Foley, plant technical services lead, Whitegate.

Another alternative feedstock used to produce renewable diesel is animal fat. In December 2007,

ConocoPhillips and Tyson Foods, in a joint venture, began producing an ultra-low-sulfur, renewable diesel from beef fat at ConocoPhillips’ Borger, Texas, plant. Management is actively looking for additional opportunities to produce renewable diesel. 

ONLY A RESPONSIBLE MIX WILL WORK

 
“But there are limits as to how much renewable diesel our present day hydrotreating units can produce,” Foley said. “We’ll need cheaper feedstocks. Perhaps even second-generation feedstocks, such as jatropha or other non-food oils. Algae oils are even being tossed about now as a source. Fuel from food is an elegant concept, but in the future, do we grow crops for food or crops for energy?”

That brings up the question of sustainability and dependence on imports of raw feedstock. If biofuels suggest clean, green, sustainable energy with increased reliance on renewable energy sources and the potential to grow them domestically, where are the feedstocks to come from? Industrialized countries already have set ambitious renewable-fuel targets, but to meet those goals without importing fuel crops, Europe, for example, would need to plant 70 percent of its cultivable land with fuel crops just to meet today’s demand.

To this end, ConocoPhillips is sponsoring research at a number of universities throughout the world to increase the diversity of feedstocks away from food crops, increase the sustainability of such crops with regard to carbon dioxide, water and other issues, while learning the impacts of land use changes.

Only a responsible mix of technologies can work. But with climate change, rising oil prices and a concern for future supplies, governments are right in supporting biofuels. “It is difficult to replace fossil fuels as our primary source of energy supply,” Mason said. “Biofuels can and will extend and conserve our fossil fuels. We can take pride that because of our excellent technical and commercial resources, we are at the forefront and are pioneers in this emerging technology. But with Whitegate’s entry into the renewable-diesel market, we now have a way to get a significant value from a renewable resource.”