# Biodiesel (FAME): Techniques One simple reaction, and the algae dream that stalled Source page: https://www.materialinsights.org/energy/biodiesel/techniques/ What this tab covers The methods used to capture this energy: how each works, and how they compare on efficiency, cost, life-cycle emissions, maturity and scale. Two techniques are covered: making FAME biodiesel by transesterification of oils and fats, and growing algae as an oil source. Vegetable oils are projected to supply about 69% of bio-based diesel feedstock in 2035, and used cooking oil and tallow 23%. #### Comparison | Method | Efficiency | Cost | Life-cycle emissions | Maturity | Scale | |---|---|---|---|---|---| | **Transesterification of vegetable oils (FAME)**^[1](https://afdc.energy.gov/fuels/biodiesel-production)^[2](https://pure.uj.ac.za/en/publications/energy-life-cycle-assessment-of-soybean-biodiesel-revisited/)^[4](https://eur-lex.europa.eu/eli/dir/2018/2001/oj)^[5](https://www.eia.gov/biofuels/update/table1.pdf)^[6](https://www.iea.org/reports/renewables-2025/renewable-transport)^[12](https://farmdocdaily.illinois.edu/2026/03/biodiesel-production-profits-and-tax-credits.html) | About 100% mass yield; fossil energy ratio 5.54 for US soybean biodiesel | Representative Iowa soybean plant: capital USD 1.57 per gallon of annual capacity, 7.55 lb of soybean oil per gallon; average net return 2021-2026 was -USD 0.26 per gallon without tax credits and -USD 0.10 with them, so costs exceeded biodiesel prices | EU typical savings against 94 g CO2eq/MJ, excluding land-use change: rapeseed 52% (about 45 g CO2eq/MJ, calculated), soybean 55% (about 42), palm with methane capture 51% (about 46), palm with open effluent ponds 33% (about 63) | mature | US capacity 1,978 million gallons a year (September 2025); US output fell 40% from Q1 2024 to Q1 2025 as credit values fell | | **Transesterification of waste oils and animal fats**^[1](https://afdc.energy.gov/fuels/biodiesel-production)^[4](https://eur-lex.europa.eu/eli/dir/2018/2001/oj)^[7](https://www.downtoearth.org.in/agriculture/food-crops-to-remain-backbone-of-global-biofuel-production-through-2035-oecd-fao-report-finds) | Mass yield similar to virgin oils | Not quantified | EU typical saving 88% for waste cooking oil (about 11 g CO2eq/MJ, calculated) and 84% for animal fats (about 15) | mature | Used cooking oil and tallow projected at about 23% of bio-based diesel feedstock in 2035 | | **Algae cultivation**^[3](https://www.ourenergypolicy.org/wp-content/uploads/2012/07/Beal_EROIAlgae_BioEnergyResearch_OnlineFirst.pdf) | Energy return 0.00092-0.35 (below 1) | Not quantified | Not quantified | research | No commercial fuel production identified | The chemistry is cheap and well established; the feedstock decides cost and emissions. Waste cooking oil and tallow biodiesel save 84-88% of fossil diesel emissions under EU default values, while palm biodiesel from mills with open effluent ponds saves only 33% before land-use change, for which ICAO adds about 37 g CO2eq/MJ. Waste oils are limited, so most biodiesel still comes from food oils. Biodiesel increasingly competes with renewable diesel (HVO), which uses the same feedstocks but gives a fuel identical to fossil diesel. Algae remain a research topic because growing and processing them takes more energy than they yield. #### How each method works **Transesterification of vegetable oils (FAME)** Rapeseed, soybean or palm oil is mixed with methanol and a catalyst (usually sodium or potassium hydroxide). Each fat molecule splits into three methyl ester (biodiesel) molecules and one glycerin molecule, which settles out and is sold.^[1](https://afdc.energy.gov/fuels/biodiesel-production)^[2](https://pure.uj.ac.za/en/publications/energy-life-cycle-assessment-of-soybean-biodiesel-revisited/)^[4](https://eur-lex.europa.eu/eli/dir/2018/2001/oj)^[5](https://www.eia.gov/biofuels/update/table1.pdf)^[6](https://www.iea.org/reports/renewables-2025/renewable-transport)^[12](https://farmdocdaily.illinois.edu/2026/03/biodiesel-production-profits-and-tax-credits.html) **Transesterification of waste oils and animal fats** The same reaction is applied to used cooking oil or rendered animal fat, which are cheaper but more variable and need more cleaning first.^[1](https://afdc.energy.gov/fuels/biodiesel-production)^[4](https://eur-lex.europa.eu/eli/dir/2018/2001/oj)^[7](https://www.downtoearth.org.in/agriculture/food-crops-to-remain-backbone-of-global-biofuel-production-through-2035-oecd-fao-report-finds) **Algae cultivation** Microalgae grow in ponds or closed tubes with sunlight, CO2 and nutrients. The cells are harvested, dewatered and their lipids extracted and converted to fuel; leftover biomass can be digested to methane.^[3](https://www.ourenergypolicy.org/wp-content/uploads/2012/07/Beal_EROIAlgae_BioEnergyResearch_OnlineFirst.pdf) #### Sources 1. [Biodiesel Production and Distribution](https://afdc.energy.gov/fuels/biodiesel-production) US Department of Energy, Alternative Fuels Data Center, 2025 2. [Energy life-cycle assessment of soybean biodiesel revisited (Pradhan et al., Transactions of the ASABE 54(3))](https://pure.uj.ac.za/en/publications/energy-life-cycle-assessment-of-soybean-biodiesel-revisited/) ASABE (abstract, University of Johannesburg repository), 2011 3. [The Energy Return on Investment for Algal Biocrude: Results for a Research Production Facility (Beal et al., BioEnergy Research)](https://www.ourenergypolicy.org/wp-content/uploads/2012/07/Beal_EROIAlgae_BioEnergyResearch_OnlineFirst.pdf) Springer (author copy, OurEnergyPolicy), 2011 4. [Directive (EU) 2018/2001 (Renewable Energy Directive II), Annex V: typical and default greenhouse gas savings for biofuels (Parts A and B); fossil comparator 94 g CO2eq/MJ. Default values not changed by amending Directive (EU) 2023/2413 (RED III); a Commission revision was in draft in 2026](https://eur-lex.europa.eu/eli/dir/2018/2001/oj) European Union (EUR-Lex), 2018 5. [Monthly Biofuels Capacity and Feedstocks Update, Table 1: U.S. biofuels operable production capacity](https://www.eia.gov/biofuels/update/table1.pdf) US Energy Information Administration, 2025 6. [Renewables 2025: Renewable transport](https://www.iea.org/reports/renewables-2025/renewable-transport) International Energy Agency, 2025 7. [Food crops to remain backbone of global biofuel production through 2035 (summary of OECD-FAO Agricultural Outlook 2026-2035; feedstock shares are 2035 projections)](https://www.downtoearth.org.in/agriculture/food-crops-to-remain-backbone-of-global-biofuel-production-through-2035-oecd-fao-report-finds) Down To Earth, 2026 8. [Biodiesel Production Profits and Tax Credits (Irwin, farmdoc daily 16:46; representative Iowa soybean-oil FAME plant model)](https://farmdocdaily.illinois.edu/2026/03/biodiesel-production-profits-and-tax-credits.html) University of Illinois, farmdoc daily, 2026 ## Other sections - [Summary](https://www.materialinsights.org/energy/biodiesel/index.md) - [Energy overview](https://www.materialinsights.org/energy/biodiesel/energy/index.md) - [Correlation](https://www.materialinsights.org/energy/biodiesel/correlation/index.md) - [Efficiency](https://www.materialinsights.org/energy/biodiesel/efficiency/index.md) - [Resources and labour](https://www.materialinsights.org/energy/biodiesel/resources/index.md) - [Impact on the biosphere](https://www.materialinsights.org/energy/biodiesel/biosphere/index.md) - [Overview](https://www.materialinsights.org/energy/biodiesel/overview/index.md) - [Production route](https://www.materialinsights.org/energy/biodiesel/routes/index.md) - [Production](https://www.materialinsights.org/energy/biodiesel/production/index.md) - [Feedstocks](https://www.materialinsights.org/energy/biodiesel/feedstocks/index.md) - [Cycles](https://www.materialinsights.org/energy/biodiesel/cycles/index.md) - [Trading](https://www.materialinsights.org/energy/biodiesel/trading/index.md) - [Movement](https://www.materialinsights.org/energy/biodiesel/movement/index.md) - [Regulation](https://www.materialinsights.org/energy/biodiesel/regulation/index.md) - [Characteristics](https://www.materialinsights.org/energy/biodiesel/characteristics/index.md) - [Emissions](https://www.materialinsights.org/energy/biodiesel/emissions/index.md) - [Relationships](https://www.materialinsights.org/energy/biodiesel/links/index.md)