The defensible thesis is narrow. It is not that 45Z removed a domestic substitute or knocked tallow out of the oleochemical supply chain. North American tallow is eligible and favored under 45Z. The point is that 45Z and broader renewable diesel policy may bid up North American tallow costs, which creates a record issue about whether the fatty acids industry cost-price squeeze is better explained by a feedstock cost shock that subject imports did not cause.
What Section 45Z actually changed
The Clean Fuel Production Credit is codified at 26 U.S.C. § 45Z. The Inflation Reduction Act created it for clean transportation fuel, and Public Law 119-21 amended it to condition the credit on fuel being exclusively derived from feedstock produced or grown in the United States, Mexico, or Canada, effective for fuel produced after December 31, 2025. The amendment also extended eligibility through December 31, 2029 and added statutory foreign-entity restrictions for certain taxpayers and feedstock pathways. Treasury and IRS proposed the regulations on February 4, 2026, with written comments due April 6, 2026 and an initial hearing date of May 28. A later hearing notice expanded the hearing to May 27 through May 29, and the May 8, 2026 notice changed all three days to a telephonic-only format. The proposed regulations confirm that transportation fuel produced after December 31, 2025 must be derived exclusively from feedstock produced or grown in the United States, Mexico, or Canada, and the cited rulemaking record stands as a proposed rule through the May 2026 hearing notices.
The mechanism needs to stay narrow. The rule does not ban foreign feedstocks. It limits the credit-eligible fuel pathway, because transportation fuel produced after December 31, 2025 must be derived exclusively from feedstock produced or grown in the United States, Mexico, or Canada. On the rationale, Treasury flagged the difficulty of reliably distinguishing imported used cooking oil from palm oil and the risk of credits attaching to ineligible fuel, and it requested comment on substantiation and recordkeeping for feedstock imported from Canada and Mexico. The rule restricts foreign feedstock pathways, including imported used cooking oil. It is less precise to assert that blocking Chinese used cooking oil was the rule single stated purpose.
Why tallow sits on the contested side of the line
Tallow has shifted from a low-value rendering byproduct to a contested renewable feedstock. U.S. renewable diesel and other biofuels capacity has expanded sharply since 2021, which pulled animal fats into fuel use and bid up rendered fat prices. USDA Economic Research Service data place biomass-based diesel feedstock demand at a record 37.2 billion pounds in marketing year 2023 to 2024, and tie that demand to rising imports of tallow, used cooking oil, and processed oils and to higher domestic feedstock prices. EIA monthly feedstock data show tallow as the dominant disclosed waste oil, fat, and grease input to U.S. biofuel production in early 2025, running well above yellow grease and white grease.
Because tallow produced in the United States, Canada, or Mexico sits on the favored side of the 45Z line while non-North American waste oils and offshore fats fall off the credit-eligible pathway after 2025, competition between fuel and oleochemical buyers for a constrained North American tallow pool may intensify. The mechanism is demand reallocation and bid-up, not exclusion of tallow. Supply is the binding limit, because tallow output is capped by cattle slaughter volumes and cannot expand quickly, so fuel demand and oleochemical demand compete directly for a fixed pool.
One empirical caution belongs here. Early 2026 feedstock data do not yet establish a clear post-2025 increase in tallow use, and any monthly figure should be used only if the underlying EIA monthly series is linked directly and the calculation is reproducible. Without that table, the safer point is that the bid-up theory remains prospective and record-dependent unless price data, purchaser testimony, or proprietary cost evidence supports it. EIA monthly feedstock data and USDA series are the authoritative basis for any quantified claim, and trade-press and market-research numbers should be treated as indicative only.
The case is real and advancing
Vantage Specialty Chemicals filed the antidumping and countervailing duty petitions on certain fatty acids from Indonesia and Malaysia on January 28, 2026. The matter sits at the International Trade Commission as Investigation Nos. 701-TA-785-786 on the countervailing duty side and 731-TA-1773-1774 on the antidumping side. The scope covers certain fatty acids separated from animal fat or vegetable oil sources, with carbon chain lengths from C6 to C18, an iodine value below 105 grams per 100 grams, and a degree of split of at least 97 percent. The Commission notice enumerates eight HTSUS subheadings, 2915.70.01, 2915.90.10, 2916.15.10, 2916.15.51, 3823.11.00, 3823.12.00, 3823.19.20, and 3823.19.40, with 3824.99.4190 appearing in Commerce scope appendix. The written scope description is dispositive and also addresses third-country processing and blending, so importers should classify against the written scope rather than the HTS list alone.
Commerce initiated both the less-than-fair-value and the countervailing duty investigations on March 9, 2026, published March 13, 2026, after polling for industry support. Its initiation-stage estimated dumping margins are 18.38 to 69.56 percent for Indonesia and 59.56 to 170.49 percent for Malaysia, and those are the current official figures. The petition alleged separate ranges that differ from Commerce calculations, particularly at the Malaysia ceiling, and they should be cited apart if at all. The Commission instituted the preliminary phase effective January 28, 2026, published the institution notice on February 2, 2026, and filed its affirmative preliminary injury determinations on April 3, 2026, with the views set out in USITC Publication 5723. The period of investigation is the 2025 calendar year.
The schedule is the practitioner clock. Commerce postponed the countervailing duty preliminary determination to July 17, 2026. Unless postponed, the antidumping preliminary determination is due 140 days after the March 9, 2026 initiation, which places the default deadline on July 27, 2026, and any later, fully postponed date should be stated only with a Commerce postponement notice or statutory citation. Cash-deposit liability would attach only on publication of affirmative Commerce preliminary determinations in the Federal Register.
The timing mismatch is structural
The period of investigation is calendar year 2025. The North American feedstock restriction applies to fuel produced after December 31, 2025. Any direct claim that the restriction caused 2025 injury is vulnerable on its face, because a 2026 rule cannot explain a 2025 record. The disciplined sequence keeps the two periods apart. For the 2025 period, attribute cost pressure to renewable diesel expansion, existing biofuel demand, and broader feedstock inflation, all of which were in force during the period of investigation. Reserve the post-2025 feedstock restriction for final-phase current-conditions and threat analysis, where it can be argued to intensify competition for a constrained North American tallow pool going forward. Keeping the periods separate forecloses the obvious rebuttal.
Why this is new
The new point is not that renewable diesel demand matters to tallow. That was already a market condition before the petitions. The new point is that Section 45Z now gives respondents a narrower way to connect post-2025 feedstock policy to final-phase threat and non-subject causation without overclaiming that the rule caused the 2025 injury record. The credit-eligibility line drawn after December 31, 2025 is what converts a general feedstock-inflation story into a specific, forward-looking conditions-of-competition argument that a respondent can build with record evidence.
Frame 45Z as a non-subject cause, not an affordability plea
The ITC injury analysis is not a consumer-affordability balancing test. It turns on subject-import volume effects, price effects through underselling, price depression, and price suppression, impact on the domestic industry, non-attribution of injury caused by other known factors, and conditions of competition. The downstream affordability message belongs in external policy communication. Inside the record, the same facts have to be argued as a raw-material cost shock, a non-subject cause, and a condition of competition. Separate downstream-affordability advocacy may develop around the case, but unless a filing appears in EDIS, that advocacy should not be treated as establishing a 45Z or tallow non-subject-causation argument on the Commission record.
The same mechanism matters for causation. 45Z does not disqualify tallow. It favors North American tallow, and by excluding foreign feedstocks from credit-eligible fuel after 2025 it may redirect fuel producers toward a constrained domestic tallow pool, which raises feedstock costs for oleochemical producers such as Vantage. The argument is strongest on causation and threat, where the Commission must separate injury caused by subject imports from injury caused by other factors.
What respondents and importers should do
The first task is to build the 45Z and tallow record rather than assume it is before the Commission. The conditions-of-competition and non-attribution portions of a final-phase submission should carry EIA monthly feedstock-consumption data, USDA animal-fat price series, Census import data on tallow, used cooking oil, and palm-derived inputs, and the 45Z rulemaking record. The benchmark that decides the argument is documented, quantified tallow-cost movement tied where possible to Vantage own cost structure through proprietary discovery. If Vantage tallow share is low, the argument weakens, which makes that single fact the most important one to develop.
The second task is to model exposure now. The countervailing duty preliminary determination is due July 17, 2026, and the antidumping preliminary determination is due 140 days after the March 9, 2026 initiation unless Commerce postpones it. Given initiation-stage margins that reach 170.49 percent for Malaysia in Commerce own calculation, importers should quantify duty exposure immediately and consider securing supply or alternative sourcing before cash-deposit liability attaches.
What petitioner-side counsel should pre-empt
Petitioner-side counsel can blunt the 45Z argument on three fronts. Argue that feedstock flexibility within the domestic like product cuts against treating tallow cost as a decisive driver, since the in-scope fatty acids can be separated from vegetable oil as well as animal fat. Emphasize that 2025 injury cannot be explained by a 2026 feedstock rule. And argue that any tallow price pressure is an industry-wide condition that does not excuse subject-import underselling, market-share gains, lost sales, or utilization decline. Commerce summarized the petitioner injury allegations as a significant increase in subject imports, reduced market share, underselling, price depression or suppression, lost sales and revenues, and negative financial performance, and that record of subject-import effects is what the 45Z argument has to overcome rather than sidestep.
What would change the calculus
If USITC Publication 5723 or any final-phase brief is shown to contain a 45Z or tallow argument, the thesis moves from inferred to documented. If Commerce issues negative preliminary determinations, immediate cash-deposit exposure would be deferred while the investigations continue, and duty exposure becomes moot only on negative final Commerce determinations, a negative final ITC injury determination, or termination. If a downstream-user coalition files an entry of appearance or a brief, the non-subject-cause argument gains an institutional sponsor on the record.
Caveats
The record-status point is central. The public sources reviewed for this draft do not establish that a 45Z or tallow theory has been presented on the Commission record, and that point should remain provisional until the EDIS docket, including entries of appearance, briefs, questionnaire comments, and final-phase submissions, is reviewed directly. The timing mismatch is structural, because the period of investigation is 2025 while the North American feedstock restriction applies to fuel produced after December 31, 2025. Phrases such as removed the domestic substitute or knocked tallow out overstate the mechanism, which runs through demand reallocation and bid-up, not exclusion. On the margins, use Commerce initiation-stage figures of 18.38 to 69.56 percent for Indonesia and 59.56 to 170.49 percent for Malaysia as the current official numbers and cite petition allegations separately if at all. The degree of tallow reliance in the domestic industry is a plausible record issue rather than a proven cost driver, because the tallow share of total feedstock cost is not public, and any claim about a 2024 tallow-capacity expansion is secondary-source reporting unless corroborated by the petition or questionnaire responses. The antidumping preliminary determination date is set by the 140-day rule from the March 9, 2026 initiation unless Commerce postpones it, and any postponed date should be stated only with a postponement notice.