How used cooking oil becomes Green Diesel

  • Oct 18, 2021
  • OMV

The whole country smells of schnitzel, fries and chicken nuggets because the cars run on biodiesel made of used cooking oil? Could this be the future of driving? Yes. And no. After all, the rumor about the smell is not true.

“OMV is working on increasing the amount of used cooking oil for the production of biofuels”, confirms Gudrun Kollmitzer. But the path from the fast-food-chain fryer to the tank of a car is long and complex. And used cooking oil is just one of many raw materials that OMV works with and that can be processed into Green Diesel using a method known as Co-Processing.

“Co-Processing” basically does what it says – processing substances together. In this case it refers to the technology that will be used in the Schwechat Refinery to produce Green Diesel. While conventional methods blend in the biofuel component from vegetable oil or used cooking oil only after the diesel has been produced, with Co-Processing the biofuel is processed together with the crude in what’s known as a hydrotreatment plant. Here hydrogen is added to the oil mixture, thereby removing non-desirable components such as oxygen or other impurities. What remains is pure carbon, which, from a chemical viewpoint, closely resembles diesel fuel obtained from crude oil alone. This is also a very high-quality fuel that can be used in vehicles without any problems.

Even today, the diesel that we pump at the filling station usually has a conventional biocomponent mixed in, although this is limited to up to seven percent for quality reasons. The high product quality achieved with Co-Processing allows us to increase this to as much as 25 percent, thereby achieving a far sharper reduction in the carbon footprint.

The first attempts in the Schwechat Refinery to produce high-quality biodiesel through Co-Processing started back in 2016. The plan now is to build a large plant capable of processing up to 160,000 metric tons of biogenic feedstock every year. This will make OMV one of the first companies in Europe to run an industrial-scale Co-Processing operation. “The advantage with Co-Processing is that there are no technical limitations regarding the raw materials, the feedstock. In theory, the plant can process crude together with any other type of oil – rapeseed, sunflower or, yes, used cooking oil. That said, just like with the crude itself, these oils must meet certain quality levels, but there are clear specifications for this. For example, a limit on how much phosphorous or other metals they are allowed to contain”, explains Gudrun Kollmitzer. At present, the limiting factor is rather one of availability: “The oil used is heavily dependent on supply. Not all feedstocks are available in the requisite quality and quantity”.

Initially, vegetable oils should be the primary source in the Co-Processing plant in Schwechat, thereby producing first-generation biofuels. And there is a clear legal framework in place to ensure that no competition develops between plate and tank: “For us this means that we will not be allowed to raise the biocomponent in our fuels above the national limit of 7 percent maximum in the coming years”, reports Gudrun Kollmitzer. “That is why we are already looking at the next phase, namely the expansion of our portfolio to include second-generation biofuels, i.e. waste-based fuels. Included here for example is processing used cooking oils. The special challenge lies in the availability of used cooking oil and its quality. The feedstock first has to be processed properly before it can be incorporated in the refining process”. And OMV is also on the ball when it comes to “Advanced Fuels”, i.e. third-generation biofuels. “We are constantly looking at alternative sources of feedstock”, explains Gudrun Kollmitzer. This is where oils from algae and cashew shells for example come into play. “A lot is being done worldwide in this area, new developments are happening all the time and there’s a lot of research in every direction. What’s important for us is to stay on the ball and to evaluate for each of the highly promising developments whether the availability and product yield are right for us for each of the different feedstocks”.

Hydrotreated vegetable oil, as produced in the Co-Processing plant in the Schwechat Refinery from 2023, can save up to 360,000 metric tons of CO2 a year compared to fossil diesel. That is equivalent to the emissions of a car driving 60,000 times around the equator. To qualify as a biofuel, the fuel must achieve a CO2 reduction of at least 65 percent compared to fossil diesel.

Even if we cannot know at present which feedstock will eventually win the race, it is clear that there is no way around reducing CO2. After all, even though the importance of alternative drive forms such as electric is increasing, in the medium term, cars powered by gasoline and diesel will remain a common sight on our roads for a long time to come given their long service life. This means that environmentally sound alternatives for these conventional fuels are simply a must.