Biodiesel is the great hope, our main hope, the only renewable fuel of all the many options, and the closest to the diesel essential for rail, trucks, and ships to do the actual work of civilization.

The U.S. produces over a billion gallons a year of biodiesel in the U.S. Our biodiesel is made from 95% vegetable oils (68% soybean, 16% corn, 11.4% canola) and 5% animal fats and grease (EIA 2019a).  About one tenth of biodiesel comes from used cooking oil.

No other biofuel can substitute for diesel fuel besides biodiesel, for reasons explained here and a dozen chapters in Life After Fossil Fuels: A Reality Check on Alternative Energy. Not ethanol from corn, cellulose, or kelp. Nor biodiesel from algae, finite liquefied coal (CTL), hydrogen, ammonia, power-to-gas, methane hydrates, natural gas, or oil shale.  And while I’m at it, nor can transportation be electrified with batteries or overhead wires.

Biodiesel hits the ball out of the park. It is renewable. Trucks can run on it. It is commercial.

Scale is an issue though.  Globally, 27.95 million barrels of petroleum diesel are consumed per day, but only 655,000 barrels of biodiesel (BP 2020). Biodiesel production would need to be scaled up 43-fold after oil decline.

And there’s not enough land, too much soil erosion and aquifer depletion, climate change, drought, and more limiting soybean and other oilseed production.

The U.S. burns 46 billion gallons of petroleum diesel a year. It makes just 1.8 billion gallons of biodiesel annually, 25 times less than needed (EIA 2018, EIA 2019).

It bears repeating: 68% of U.S. biodiesel comes from soybeans. Even if all 87.2 million acres of soybeans, grown on a quarter of America’s cropland, were used to make biodiesel, just 5.7 billion gallons could be produced. But that isn’t likely, since soybeans are also in demand for livestock feed, cooking oil, baked goods, soy milk, tofu, industrial lubricants and other goods (NCSPA 2019).

Corn can yield 18 gallons of biodiesel per acre. Soybeans can yield 65 gallons of biodiesel per acre.  What accounts for this difference?  Not crop yield. Corn yields 177 bushels per acre and soy just 52 bushels. Rather, it is fat content. Corn is 4% fat whereas soy is 20% fat. You need fat to produce biodiesel.  Despite its low-fat content (four percent) and because of its high yield, corn manages to contribute 16% of annual U.S. biodiesel production in 2019.

For biodiesel, peanuts would be better than either corn or soybeans. Peanuts are half oil and can yield 123 gallons per acre. But they grow only in the most humid areas of seven Southeastern states. Nor do other oil seed crops scale up.

Besides ramping up production, distribution will need to be scaled up too. There are 168,000 gas stations but only 300 where 20% biodiesel (B20) or above is available (AFDC 2020).

Biodiesel requires a lot of water. The water footprint of biodiesel from seed to harvest to delivered fuel is vast, not good at a time of increasing drought, population growth, and aquifer depletion. Soy biodiesel requires 13,676 liters (3613 gallons) of water per liter of biodiesel produced and corn ethanol 2,570 liters (725 gallons) (Gerbens-Leenes 2009). Petroleum gasoline has a much smaller footprint, on average just 4.5 gallons of water per gallon of gasoline produced Wu et al. (2018).

Water is a problem both coming and going. Plants end up as 90-95% water. Removing this water to make fuels takes a lot of energy, but has to be done to avoid corroding and clogging diesel engines (Racor 2013).

Bad chemistry.  Making fuels from plants is challenging because their chemistry differs from crude oil, which is nearly all hydrocarbon chains of 82-87% carbon and 12-15% hydrogen.

Plants have hydrocarbons, but are also chockablock with oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, zinc, sulfur, chlorine, boron, iron, copper, manganese and more.  Good for vitamin pills, bad for trucks, these elements need to be removed to make biodiesel, adding to cost and energy.

Even then, plant oils are so different from petroleum diesel oil that it is hard to match the specifications of the diesel fuel standard. This standard, ASTM D 975, specifies energy density, oxidative and biological stability, lubricity, cold-weather performance, elastomer compatibility, corrosivity, emissions (regulated and unregulated), viscosity, cetane number, distillation curve, ignition quality, flash point, low-temperature heat release, metal, ash, and sulfur content, water tolerance, specific heat, latent heat, toxicity, and ash and sulfur content. It seems nearly miraculous that crude oil can be refined to conform to all these specifications. And it’s a lot to ask of a soybean.

Unlike standard diesel, biodiesel is biodegradable, and thus needs to be used within 45 to 90 days.

Why such extensive specifications for diesel? Fuel outside the specifications can harm diesel engines by gelling up in cold weather or acting as a solvent, releasing rust and other contaminants that plug filters and fuel injectors, and more (Bacha et al. 2007, Schmidt 2007).

That’s why many heavy-duty engine manufacturers have warranties that don’t allow biodiesel, though B5 (5% biodiesel / 95% petroleum diesel) is often fine. Some warranties prohibit B20 to B100.

Distribution is a problem too. Biodiesel can’t travel in oil or gas pipelines, because, like ethanol, biodiesel is a good solvent, and able to pick up water and impurities that can harm engines (APEC 2011).  It is five to 20 times more costly to move biodiesel by rail or truck than were it possible to use pipelines (Curley 2008).

A barrel of crude oil is only 10-15% diesel in the U.S.  It will take decades to build thousands of biodiesel factories, shift more cropland to oilseed crops, modify truck engines to burn B100, and build pipelines that can handle biodiesel.

If we could convert more crude oil to diesel, we could buy time for a transition from diesel to biodiesel. But only about 10 to 15 percent of a barrel of crude oil can be refined into diesel. A barrel of crude oil makes dozens of other useful products. As crude oil is heated at the refinery, fractions split off. The first to go are lighter hydrocarbons for plastics, then propane, gasoline, kerosene for jets, diesel, heavy oil, and asphalt.

The EROI of biodiesel is low, roughly 1.3 to 1.9 (Pimentel 2005, Hill et al. 2006), far short of the 10 to 14:1 needed to keep civilization as we know it continuing (Lambert et al. 2014).

Conclusion. Biodiesel is significantly more expensive to make than petroleum diesel, so like ethanol, its existence is almost entirely due to federal policies such as the RFS biomass-based diesel and biodiesel production tax credits, excise tax credits, small biodiesel producer credits, and the RFS mandate that requires specific amounts of biodiesel in the overall fuel pool (Schnepf 2013).

Farmers can’t grow enough oilseeds to replace petroleum diesel. But some of it is made from animal fats and grease. That brings us to the next question: Can we eat enough French fries to keep trucks running?

Alice Friedemann  www.energyskeptic.com  Author of Life After Fossil Fuels: A Reality Check on Alternative Energy; When Trucks Stop Running: Energy and the Future of Transportation”, Barriers to Making Algal Biofuels, & “Crunch! Whole Grain Artisan Chips and Crackers”.  Women in ecology  Podcasts: WGBH, Planet: Critical, Crazy Town, Collapse Chronicles, Derrick Jensen, Practical Prepping, Kunstler 253 &278, Peak Prosperity,  Index of best energyskeptic posts

References

AFDC (2020) Biodiesel Fueling Station Locations (B20 and above). U.S. Department of Energy, Energy Efficiency & Renewable Energy.

APEC (2011) Biofuel transportation and distribution. Options for APEC economies. Asia-Pacific Economic Cooperation.

Bacha J, Freel J, Gibbs A, et al (2007) Diesel Fuels Technical Review. Chevron Corporation.  https://www.chevron.com/-/media/chevron/operations/documents/diesel-fuel-tech-review.pdf.

BP (2020) Statistical Review of World Energy 2020. British Petroleum.

Curley M (2008) Can ethanol be transported in a multi-product pipeline? Pipeline and Gas Journal 235: 34.

EIA (2018) Table 3.7c Monthly Energy Review. Petroleum consumption: transportation and electric power sectors. U.S. Energy Information Administration.

EIA (2019a) Table 3. U.S. Inputs to biodiesel production.  U.S. Energy Information Administration.

EIA (2019b) Table 10.4 Biodiesel and other renewable fuels overview. U.S. Energy Information Administration.

Gerbens-Leenes W, Hoekstra AY, van der Meer TH (2009) The water footprint of bioenergy. Proceedings of the National Academy of Sciences 106: 10219-10223.

Hill J, Nelson E, Tilman D, et al (2006) Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels. Proceedings of the National Academy of Sciences 103:11206-11210.

Lambert JG, Hall CAS, Balogh S, et al (2014) Energy, EROI and quality of life. Energy Policy 64:153–167.

NCSPA. 2019. Uses of soybeans. N.C. Soybean Producers Association.                 https://ncsoy.org/media-resources/uses-of-soybeans/.

Pimentel D, Patzek TW (2005) Ethanol production using corn, switchgrass, and wood; biodiesel production using soybean and sunflower. Natural Resources Research 14, 65–76.

Racor. 2013. Water, a diesel engine’s worst enemy. Racornews.                 https://www.racornews.com/single-post/2013/12/05/Water-A-Diesel-Engines-Worst-Enemy.

Schmidt CW (2007) Biodiesel: cultivating alternative fuels. Environ. Health Perspect. 115: 86-91.

Schnepf R (2013) Agriculture-based biofuels: overview and emerging issues. CRS Report R41282. Congressional Research Service.

Wu M, Xu H (2018) Consumptive water Use in the production of ethanol and petroleum gasoline – 2018 Update. Argonne National Laboratory: Energy Systems Division. doi:10.2172/1490723