Matt Leuck discusses the future of refining for alternative fuels

In hyper-charged political and economic atmospheres, where struggles between corporations and green interests intersect with geopolitical instability, you have to admit, it’s tough to be in the traditional refining business. The question for any refiner is: How do you remain viable in a cleaner and more efficient world?

As diesel prices continue to rise, and the pressure for investment in environmentally friendly fuel alternatives and technologies grows, refiners are on the lookout for new ways to better improve not only the refining process but also the resulting product that pays dividends now and well into the future. Yet, while promises of electric, biofuel and natural gas sound remarkable, the reality is commerce must continue to roll today – just as demands intensify.

The growing demand: California
In the US, the on-highway diesel market in California is currently about three billion gallons a year1. Combine that number with the fact that California is the single biggest contributor of greenhouse gas, nitrogen oxide emissions and diesel particulate matter in the atmosphere2, and it’s becoming critical for the state to find alternatives to powering its vehicles.

An increasing number of fleet managers have now turned to renewable diesel to power Class 8 trucks on day trips and on longer runs across California. Throughout the state, fleet managers also deliver critical municipal services with renewable diesel in fire trucks, garbage trucks, buses and other locally driven vehicles.

Although renewable diesel currently displaces only a small percentage of California’s annual fossil diesel consumption, demand is beginning to exceed the available supply. A number of renewable diesel producers in the US have begun initiatives to both produce and sell renewable diesel in California; and money from the California state coffers is now in the mix to build new production facilities as well as convert traditional refineries to renewable diesel. By 2020, it’s expected that an additional several hundred million gallons of renewable diesel will be delivered for use in heavy-duty vehicle (HDV) applications3.

Refining beyond California
The advantages of renewable diesel are obviously of great interest to anyone who is responsible for the efficient operation of a diesel-powered fleet. That reality extends globally. The UK now faces even stricter biofuel targets, aiming to double the use of renewable fuels within the transportation sector over the next 15 years4. Meanwhile, the Renewable Transport Fuel Obligation (RTFO) will push refiners to ensure their mixture of fuel is at least 12.4 per cent biofuel by 20325. Could widespread adoption of a cleaner refining process be the answer?

Standing in the gap: renewable diesel
Renewable diesel is a premium-quality diesel fuel that’s made completely from renewable and sustainable biomass, including wastes and residues from animal and fish fat, as well as used cooking oils and vegetable oils.

Producing renewable diesel not only employs several techniques refiners worldwide are familiar with but also allows for greater advantages over traditional petroleum diesel. For example, feedstocks are 100 per cent renewable, and the cetane and cloud point of these fuels can be custom engineered. The process is quite revolutionary.

Step One: Hydrotreating
After pretreatment to remove metals and contaminants, high-temperature hydrogen and a catalyst are applied under pressure in a process called hydrotreating. This process breaks the feedstock’s triglyceride molecules to create straight-chain hydrocarbons. That’s a normal paraffin, which would be solid at room temperature. Though pure and an ideal diesel fuel, it can be obviously problematic in application. A byproduct of the process is renewable propane.

Two: Isomerization
Isomerization renders the result of hydrotreatment as a liquid at different temperatures by changing the ratio of straight-to-bent hydrocarbons, making them more or less averse to binding.

This process allows for precise adjustment of cold properties, depending upon how much of the product is isomerized. For example, around 80 per cent isomerization yields a fuel that is stable down to -4 degrees Fahrenheit. Some renewable diesels have been successfully produced to be stable for arctic applications, as low as -29 degrees Fahrenheit.

The initial steps of the renewable diesel refinement process break triglycerides from 100 per cent renewable sources into straight-chain hydrocarbons. The result of hydrotreating and isomerization yields ideal hydrocarbons for diesel applications, falling into the ‘sweet spot’ of C15 to C18 without the olefins and aromatics. Compare that with the range of hydrocarbons present in petroleum diesel, many of which present significant challenges for clean and efficient combustion.

Thus, the resulting cleaner emissions and added benefits of renewable diesel pay off for customers who purchase and adopt this fuel into their current fleets.

  • With a cetane number ranging from 75 to 85, renewable diesel combusts more readily than petroleum diesel, which has a cetane number from 42 to 52. The result: better throttle response, quicker cold-starts and quieter operation.
  • Renewable diesel can be poured straight into an existing fuel tank or mixed in the tank with petroleum diesel already available at a fleet’s home base or refueling centers along the route.
  • Renewable diesel has nearly zero impurities that can contaminate oil, foul fuel injectors and plug diesel particulate filters (DPF). This quality lowers maintenance costs and roadside delays for DPF regenerations.

Renewable diesel not only provides all of the sustainability and performance benefits customers – and even the government – demand, but it also fuels the growing profitability that refiners require for the sustainability of their businesses now and in the future.

2 Ibid.
5 Ibid.

Neste US, Inc.
Matt Leuck is the renewable diesel fuel technical manager for Neste US, Inc., where he applies engine and equipment expertise to support Neste’s position at the leading edge of cleaner, low-carbon renewable fuel. Neste Corporation is the world’s largest producer of renewable diesel refined from waste and residues, also introducing renewable solutions to the aviation and plastics industries.

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