Biodiesel vs Renewable Diesel: The Decision Guide

These two products share a feedstock pool and often share a facility block diagram, but they are chemically different fuels produced by different processes. Confusing them is common and expensive. This guide separates them by process, product spec, capex, and business model.

Bottom line: biodiesel (FAME) is a simpler, cheaper retrofit of esterification chemistry with finished-product blending limits. Renewable diesel (HVO) is a hydrogenation refinery process that makes a drop-in diesel replacement and a coproduct SAF, at roughly 3-4x the capex and an order of magnitude more hydrogen demand.

The Chemistry, Stated Plainly

Biodiesel (FAME - Fatty Acid Methyl Ester)

Transesterification. Feedstock triglycerides react with methanol and a sodium/potassium methoxide catalyst at 60-70 degC, 1 atm. Products: FAME (biodiesel) + glycerin byproduct. Simple, low-pressure, low hydrogen demand.

Triglyceride + 3 CH3OH ⟶ 3 R-COO-CH3 + Glycerin
(with NaOH/KOH catalyst, ~60 degC)

Renewable Diesel (HVO - Hydroprocessed Esters and Fatty Acids)

Hydrotreating. Feedstock is deoxygenated (decarbonylation, decarboxylation, and hydrodeoxygenation) at 300-400 degC and 600-2000 psig H2 over a supported sulfided NiMo or CoMo catalyst. Products: straight-chain paraffins (n-alkanes) that are then isomerized to branched paraffins in a separate reactor.

R-COOH + 3 H2 ⟶ R-CH3 + 2 H2O   (HDO route)
R-COOH     ⟶ R-H + CO2           (DCO route)

Specification Comparison

Property	Biodiesel B100	Renewable Diesel (HVO)	Petro-Diesel (ULSD)
Standard	ASTM D6751 / EN 14214	ASTM D975 (drop-in)	ASTM D975
Oxygen content	~11 wt%	0 wt%	0 wt%
Cetane number	48-55	70-90	40-55
Energy (BTU/gal)	119,500	122,500	129,000
Cold filter plug point	Poor (feedstock dependent)	Excellent (after isom)	Good
Oxidation stability	Poor (needs anti-oxidant)	Excellent	Good
Blending limit	ASTM D975 allows B5 (5%) without labeling	100% drop-in	-
Sulfur	<15 ppm	<10 ppm	<15 ppm

Process & Capex Comparison

Attribute	Biodiesel (FAME)	Renewable Diesel (HVO)
Scale (typical)	10-100 MMgal/yr	200-1,000+ MMgal/yr
Capex ($/gal/yr, recent)	$0.80-1.50	$3.00-6.00
Capex ($/bbl/day)	$10k-20k	$40k-80k
Unit ops	Esterification, phase sep, wash, distillation	Pretreatment, hydrotreating, isomerization, fractionation, H2 plant
Pressure	~1 atm	600-2,000 psig
Temperature	60-80 degC	300-400 degC
H2 consumption	Zero	1,500-2,500 scf/bbl
Yield (vol %)	95-100% (1:1 roughly)	85-92% (feedstock dependent)
Byproduct	Crude glycerin (10 wt%)	Light ends, propane, naphtha, water
Permitting complexity	Lower - Part 70 minor source typically	Refinery PSM / Title V / NSR major source

When to Pick Each

Pick Biodiesel (FAME) if:

You have a small-to-mid feedstock stream (under 50 MMgal/yr capacity) - the HVO economics break below this.
Capex budget is under $50M and you can't justify a hydrotreater.
You have cheap access to methanol and a market for glycerin.
Feedstock is very high FFA (brown grease, trap grease) - esterification handles FFAs fine.
End-use is blended diesel (B5-B20), not drop-in replacement.
You want to be cash-flow positive in 18-24 months.

Pick Renewable Diesel (HVO) if:

You need a drop-in diesel replacement with no blend-wall limit.
You have feedstock at scale (> 200 MMgal/yr finished product).
You have access to hydrogen (existing refinery, SMR, or contracted supply).
You want to coproduce SAF. HVO units with a hydrocracker downstream make SAF via the HEFA pathway (ASTM D7566 Annex A2) for essentially capex and yield-fraction trade-off.
Your business model monetizes LCFS credits + RINs D4 + Federal BTC. Current Clean Fuel Production Credit (45Z) also favors low-CI HVO.
You can carry capex of $500M-$2B.

Feedstock Economics Crossover

Both processes consume the same feedstocks (soy, UCO, tallow, DCO, etc.). The economics crossover happens at these typical breakpoints:

Small biodiesel (< 20 MMgal/yr): FAME wins on capex.
Mid-scale (20-50 MMgal/yr): FAME wins if already in operation; HVO wins on greenfield if you have H2.
Large (> 100 MMgal/yr): HVO clearly wins on opex per gallon due to higher product value and blend-wall-free markets.
Co-processing at existing refinery: HVO via existing hydrotreater is often the cheapest route, but catalyst and metallurgy must be checked for feedstock contaminants (phosphorus, metals, FFA).

What Kills These Projects

Biodiesel

Glycerin market collapse (oversupply crushed pricing in 2023)
Feedstock cost - waste oils command a premium because of HVO demand
Cold-flow / oxidation stability field complaints require extensive additization
B20 ceiling with diesel engine OEM warranties

Renewable Diesel

Hydrogen cost (gray H2 embeds CI; green H2 is 2-3x more expensive)
Pretreatment complexity - phosphorus, metals, FFA, chlorides all poison hydrotreating catalyst
Feedstock bidding war - RD capacity has outpaced feedstock availability
LCFS credit price volatility ($70/ton to under $30/ton in 2023-2024)
Scope 3 scrutiny on indirect land-use change (ILUC)

Decision Matrix Quick Reference

Criterion	Biodiesel	Renewable Diesel
Capex	Low	High
H2 required	No	Yes, lots
Product quality	Blend limited	Drop-in
Yield	95-100%	85-92%
Byproduct market risk	Glycerin	Minimal (LPG, naphtha)
Feedstock flex	Limited by FFA	Better with pretreatment
Cold flow	Poor	Excellent
Regulatory tailwind	RFS RIN D6/D4	LCFS, 45Z, CORSIA SAF

References

ASTM D6751, Standard Specification for Biodiesel Fuel (B100)
ASTM D975, Standard Specification for Diesel Fuel Oils
ASTM D7566, Aviation Turbine Fuel Containing Synthesized Hydrocarbons
EN 14214, Automotive Fuels - Fatty Acid Methyl Esters (FAME) for Diesel Engines
NREL/TP-5100-83916, Techno-Economic Analysis of Renewable Diesel Production (2023)
EIA Monthly Biodiesel Production Report
California ARB LCFS Lookup Tables
IRS Section 45Z Clean Fuel Production Credit guidance