For the most part, California’s farmers grow food, not fuel. But the fuel required to operate farm equipment is diesel fuel, increasingly refined from food grown on America’s great plains.
Digging into this reveals a rabbit hole of such depth and complexity that I’ll skip to the conclusion before evaluating just a few critical details. The California Energy Commission, in collaboration with the California Air Resources Board, needs to produce and publicize a report, at least once per year, that offers by percentages a concise breakdown of what raw materials are going into the state’s diesel fuel supply. That information is surely available, but it is not easy to find. It needs to be clear, easy to understand, preferably displayed on a simple table that is included in a widely promoted press release. Energy policy should not drift into the carbon neutral nirvana of biofuel without eyes wide open.
According to the California Energy Commission, during the 12 months through the end of September 2025, 3.35 billion gallons of diesel fuel were produced in California, and 48 percent of those gallons were “renewable diesel.” We can also infer, based on data from the Public Policy Research Institute and compilations based on USDA reports on fuel requirements per acre in the American Southwest, that not quite 10 percent of all diesel fuel produced in California is used by farmers. That’s a rough estimate. The actual percentage is probably greater than 10 percent.
Before going further, consider the indispensability of diesel technology. Skeptics are invited to watch the YouTube video “Can We Ever Ditch Big Diesels?,” which offers a reality check for anyone who thinks we can ditch them anytime soon. Diesels do the heavy work of civilization. Big, durable, powerful machines, unique in their simplicity, longevity, energy density, and low maintenance.
According to the U.S. Dept. of Energy, renewable diesel is defined as “made from fats and oils, such as soybean or canola oil.” Again, it would be helpful to know how much of California’s renewable diesel comes from animal fats, and where those animal fats are sourced, and to what degree such a procurement chain could scale if America adopted California’s renewable fuel standards. But for the moment, let’s focus on soybeans as a raw material for diesel fuel.
According to multiple sources – Penn State, Purdue, University of Idaho, and the University of Arkansas – the best biodiesel yield to expect from soybeans is 75 gallons per acre. So let’s suppose just 20 percent of California’s 3.35 billion gallons per year of diesel fuel used soybean oil. That would equate to a 8.9 million acres planted in soy crops, nearly 14,000 square miles.
Before getting carried away, it’s relevant to acknowledge that over 85 million acres of soybeans are harvested each year in the United States, and these farmers, along with their corn ethanol brethren (another 87 million acres), are delighted to collect biofuel subsidies and ship increasing percentages of their harvests to California refineries. But these production numbers, impressive though they are, cannot even come close to fulfilling demand if the whole nation adopted biodiesel. And isn’t that the point?
California’s ambitious reformulation mandates for diesel fuel and gasoline are not enacted, after all, with the intention of our state being the only place where carbon neutral transportation fuel becomes the standard. But 20 percent of America’s total diesel fuel production is over 9 billion gallons per year, which would require 192,000 square miles of soybeans. And even if that prodigious expansion of soybean production were to happen, where will the other 80 percent of California and the nation’s renewable diesel fuel come from? Canola oil? Animal fat? How much canola? How many animals?
Something that appears to be selectively applied as California gallops towards carbon neutrality are the restrictions on so-called “leakage.” This refers to the prohibition, explicitly stated in California’s Global Warming Solutions Act and the scoping plans pursuant to it, on “exporting” CO2 emissions to other states and nations in order to reduce California’s in-state emissions. But that is clearly something that is ignored when California imports 77 percent of its crude oil from nations with little to no regulations governing emissions, or, for that matter, labor standards. We might also ask what we ignore in nations that send us their tallow, their palm oil, and every other supposedly carbon neutral feedstock for our renewable diesel and reformulated gasoline.
It is shortsighted to assume that producing an abundant, cost-effective, sustainable, carbon neutral diesel fuel is an impossible technological hurdle. But today, “carbon neutral” fuel is not a feasible replacement for petroleum-based fuel for at least two reasons. First, because we are still mostly ignoring the impact it has on the environment where it is produced, and second, because there is no possible way production of biofuel crops and animal fats can be increased enough to replace petroleum-based fuel in the foreseeable future. And while we should not dismiss the possibility that the next generation of EVs will capture increasing market share for personal vehicles, the engines that do the heavy work of civilization are going to remain diesel powered for a very, very long time.
Californians for Energy and Water Abundance, a project of California Policy Center, was launched to build a coalition committed to abundance-oriented policies in California. The coalition aims to promote these solutions to the public and policymakers, and develop sample legislation to unlock California's energy and water potential to benefit all Californians.
Edward Ring
Director of Water and Energy Policy at the California Policy Center
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