While not much has changed today within the black-and-white Holsteins of a century ago, that’s less true for other things: television (black and white to color), gasoline (leaded to unleaded), telephones (wired to wireless and cellular). You get the picture; change is everywhere and happening faster than ever before, which includes the fuels we use to power diesel engines in the trucks, tractors and machines on the farm.

Moving to ultra-low sulfur diesel fuel was the biggest change in diesel fuel in the last 50 years, and now it’s already been nine years since that happened. Next up is expanded use of petroleum diesel fuel replacements, maybe from some unlikely sources.

Since the first diesel engine ran on peanut oil in 1893, fuels from plants have always been a part of the diesel conversation. In the 1970s, the oil embargo, veggie vans and grease-car era, backyard mechanics proved that you didn’t need “dead dinosaur oil” at all and instead proudly ran diesel cars on reclaimed, waste vegetable oil gathered from local restaurant chains.

Concerns about climate change and greenhouse gas emissions are moving governments to adopt new policies that will alter the composition of all fuels in a big way at some point in the future. It’s a tall order since total diesel fuel consumption in the U.S. in 2013 was about 54 billion gallons, according to the Energy Information Administration.

The Renewable Fuel Standard (RFS), first established in 2005, set national levels of production and use of renewable ethanol and biodiesel fuels. The first-generation soy-based biodiesel fuels are pioneers and dominate the landscape today. In 2008, just 20 million gallons of biodiesel fuel were produced.


At the end of 2013, it was 1.8 billion gallons, nearly all coming from soybean production. Technically speaking, the first-generation biodiesel is a vegetable oil processed using relatively simple techniques that yield a long-chain fatty acid methyl ester (FAME).

It is produced in 100 percent concentrations (B100) that are blended with ultra-low sulfur petroleum diesel fuel at varying concentrations to result in the B5 or B20 blends at the pump.

Every fuel has positives and negatives, and biodiesel is no different. First-generation FAME biodiesel has about 9 percent less energy content than a similar volume of petroleum diesel.

Its attractiveness to water means the formation of some acidic compounds that can cause corrosion and damage the precision fuel injectors and other components in the diesel engine. At higher blends and colder temperatures, there are concerns for freezing and gelling.

Some researchers have found that used in higher concentrations, biodiesel can make air pollution problems worse, not better, because the biodiesel blends behave differently in the combustion chamber, igniting at different temperatures, which can result in an increase in engine emissions.

There is also the issue of transportability of the blended products; currently, biodiesel can only be shipped by tanker truck or rail car to a blending location, preventing access to the vast network of oil pipelines in the U.S., which increases transportation and storage costs.

A new generation of renewable fuel products and technologies promise to improve upon the shortfalls of the first-generation products. These are often referred to as “drop-in replacements” for diesel fuel. Some process the feedstock differently, and some don’t use vegetable-based feedstock at all.

Non-esterified renewable diesel (NERD) is a second-generation alternative to the biodiesel FAME. It uses the same soybean feedstock but processes the raw material in a more refinery-like fashion, which yields a product that has better performance in cold weather (lower cloud point), better fuel stability in storage and transportation, less concern about corrosion, better ignition properties (higher cetane level) and more favorable emissions characteristics.

In addition to soybeans, this refinery-like processing method can use a more diverse feedstock including recycled waste and vegetable oils.

An example of second-generation renewable diesel is Neste Oil’s NEXBTL renewable diesel, which claims 40 to 90 percent reduction in greenhouse gas emissions compared to fossil diesel.

Its properties enable it to be directly blended at the refinery and transported via pipeline directly to distributors and petroleum marketers without the concerns for corrosion or low temperature performance of first-generation products. Honeywell also produces Honeywell Green Diesel, a hydro-processed NERD-type fuel from a variety of feedstocks which is being used in vehicles and jet aircraft.

Biotech companies are new and somewhat unusual players in the transportation fuels market. Amyris produces a high-cetane diesel fuel from its “industrial synthetic biology” platform that turns plant-based sugars to a building-block chemical – farnesene (trademarked Biofene).

This base chemical product has been used as the basis for a cure for malaria and is now popular in the flavors, fragrances and pharmaceutical industries. It also can be engineered to produce a neat diesel-fuel product, very clean, which is currently used in vehicles and aircraft.

Pond scum
Today, if you find algae growing in your diesel fuel tank, you call it contaminated. But tomorrow, another form of algae might actually be responsible for making the diesel fuel in the tank. The University of Arizona and many others are working to produce diesel fuel from pond scum, engineering the single-cell algae organisms.

Algae consume quite a bit of carbon dioxide in the production of the high-quality diesel-fuel replacement, making it carbon-favorable. It is produced in large-scale farms that use giant rotating plastic bladders filled with algae organisms, saltwater, exposed to sunlight and carbon dioxide (CO2).

Finally, with all the talk about natural gas production in the U.S., a renewed interest in gas-to-liquids (GTL) projects could mean that a future liquid diesel fuel is made from natural gas. GTL products are free of sulfur, burn very cleanly and have a high energy content but are costly to produce at current scales.

They have been used by diesel-powered race cars that won the 24-hour LeMans races over the last couple years. GTL fuel is made by converting methane into carbon monoxide and hydrogen (syngas) through a reforming process, then reacting the syngas in a special reactor unit to create long-chain hydrocarbons, which can then be converted into diesel fuel, naptha and other products.

It adds expense but also eliminates all the issues with pressurized tanks, compressors and pipelines to handle a natural gas in a gaseous state.

Will you be pumping a pond-scum-produced diesel fuel in your tractor soon? Only time will tell. The key for all these non-petroleum diesel fuels in the future is how they enter the market. Today, none of the renewable fuels are cost-competitive with petroleum diesel fuel, even at $4 per gallon, so that means government policies to address climate change or air pollution must establish by legislation or regulation a market-forcing mechanism.

If it happens on a large-scale basis, it will happen in California first. California has enacted a low-carbon fuels standard which requires that diesel fuel sold in the state have lower carbon intensity than the current fuels.

Because of their air pollution problems, they are capping the use of conventional FAME biodiesel to less than a 10 percent blend. This opens the door for second-generation renewable diesel fuel products to ultimately become a component of every gallon of diesel sold in that state. PD

Allen Schaeffer is the executive director at the Diesel Technology Forum. Contact him by email.

allen schaefer

Allen Schaeffer
Executive Director
Diesel Technology Forum