How a Texas refinery turns fat into ‘green’ jet fuel

A Texas refinery that supplies green fuel to US airlines has been purchasing animal fat from cattle raised on illegally cleared lands in the Amazon rainforest, according to a Reuters review of government tracking data, interviews and eyewitness accounts. Louisiana-based Diamond Green Diesel, a joint-venture between biofuels producer Darling Ingredients and petroleum refiner Valero Energy, has invested hundreds of millions of dollars into a refinery in Port Arthur, Texas that turns cattle fat — called tallow — into a cleaner alternative to petroleum-based jet fuel and diesel.

Diamond Green Diesel is a major player in the US sustainable fuels market. It has collected over $3 billion in US tax credits for producing biofuels since 2022, according to filings. But interviews and documents show at least two Brazilian factories that supplied Diamond Green Diesel with tens of thousands of tons of cattle fat since 2023 are sourcing some of it from slaughterhouses that have bought animals from illegally deforested ranches in the Amazon rainforest.

Carriers such as JetBlue and Southwest Airlines , which struck deals with Valero to use the “green” jet fuel, can claim credit for lowering their emissions because Diamond Green Diesel’s plant is certified under a United Nations agreement curbing the impact of aviation on the climate called CORSIA.

The global market for sustainable jet fuel is small, about $2.9 billion in 2025 according to analysis firm SkyQuest Technology Group, compared to the $239 billion global market for conventional aviation fuel. But government incentives are expected to help the market grow exponentially, pumping more resources into the Brazilian cattle industry, the leading driver of the destruction of the Amazon rainforest.

Pedro Piris-Cabezas, an economist at the nonprofit Environmental Defense Fund, said any additional demand “could result in the expansion of herds and directly or indirectly drive deforestation and forest degradation.”

It could also violate Brazilian law. “Companies that profit from raw materials originating from a supply chain that involves deforestation, are also responsible for these illegalities,” said Ricardo Negrini, a Brazilian federal prosecutor who has opened a number of government investigations into the cattle industry.

Diamond Green Diesel, Darling Ingredients, Valero Energy, Southwest and JetBlue did not reply to multiple requests for comment, including detailed questions about the Brazilian tallow supply chain.

To track the tallow trade from illegally deforested ranches in the Amazon to Diamond Green Diesel, Reuters partnered with the nonprofit investigative outlet Reporter Brasil, which helped review court documents that link slaughterhouses to the tallow plants, corporate filings, trade data, and government cattle tracking records.

Reuters also interviewed over a dozen people involved in each step of the beef tallow supply chain, including traders, truck drivers, prosecutors, auditors and regulators. Diamond Green Diesel sources tallow from multiple countries, and Reuters was unable to determine how much of it came from ranches in illegally-cleared land in the Amazon.

In 2022 Darling Ingredients CEO Randall Stuewe announced the $557 million acquisition of several plants in Brazil, including four in the Amazon region, that would supply “waste fats to be used in the production of renewable diesel and sustainable aviation fuel,” according to a statement issued at the time.

Reuters found one of those rendering plants in Para state, called Araguaia, sourced cattle fat from at least five meatpackers that failed a May 2025 audit conducted by federal prosecutors for slaughtering 20,000 cattle from illegally deforested areas.

In 2023, Araguaia exported $4.4 million worth of beef tallow from the Amazon to Diamond Green Diesel, according to trade data from Import Genius.

In June, a Reuters journalist saw a truck with an Araguaia logo inside the Sao Francisco slaughterhouse, which failed an audit for buying cattle from farms on illegally deforested land.

The driver of the truck, who spoke on condition of anonymity, told Reuters he had been picking up carcasses at the Sao Francisco slaughterhouse and delivering them to the Araguaia plant for two years. Two other drivers and two Sao Francisco employees confirmed the slaughterhouse was an Araguaia supplier.

Sao Francisco didn’t confirm or deny that it is a supplier of the Araguaia plant. It said it has been cooperating with federal prosecutors since 2018 and that it hired an outside firm to monitor its supply chain.

Sao Francisco sources some of its cattle indirectly from Vale do Paraiso, a farm that had been blocked from grazing cattle since 2006 because 15 square miles of trees had been illegally razed, according to Brazil’s environmental protection agency, Ibama. Cattle tracking data shows that the cattle was moved from Vale do Paraiso to a farm with a clean record before it reached the slaughterhouse.

The agency unblocked Vale do Paraiso last year because a court determined that the statute of limitations had expired, but its owner Antonio Lucena Barros still owes over $3 million in fines for the deforestation there, according to government documents.

Barros’ lawyer Calebe Rocha said in a statement that his client is fighting the fines in court and has been granted an injunction that suspends the payment of the fine. He also said that no animals were sold from the part of Vale do Paraiso that Ibama had blocked due to deforestation.

Another plant owned by Darling Ingredients sourced fat from a slaughterhouse that confirmed to Reuters that it bought hundreds of cattle in 2022 and 2023 from rancher Bruno Heller, who Brazil’s Federal Police has described as possibly the Amazon’s biggest deforester in a 2023 investigation.

In a statement, Heller’s lawyer Vinicius Segatto said Brazil’s environmental law is “excessively rigorous” and that the criminal case against his client is ongoing.

Airlines have been under pressure to buy more green jet fuel, which is now produced in tiny quantities, to meet industry targets of net zero emissions by 2050.

Supporters of the use of tallow as a biofuel assert that demand for it alone is unlikely to push ranchers to clear rainforest to grow their pastures because of its economic value - less than 3% of what slaughterhouses get for each animal.

Diamonds’ imports from Brazil were certified as sustainable by the International Sustainability and Carbon Certification (ISCC), a third-party certification body that approved Diamond’s plant for CORSIA.

To be eligible, biomass used for fuel cannot come from land that was deforested after 2008 or protected areas, but the ISCC told Reuters it did not investigate Diamond’s supply chain because it considers tallow a “byproduct” of the beef industry under CORSIA.