Biodiesel Production

Biodiesel is a direct replacement for petroleum diesel, made from vegetable oil or animal fat through a chemical process called transesterification. Unlike wood gas, biodiesel is a liquid fuel that stores easily, requires no engine modifications beyond fuel line material changes, and can be produced in batches from scavenged or farm-grown feedstock. Any diesel engine — generator, tractor, truck, pump — can run on properly made biodiesel.

Chemistry of Transesterification

The Reaction

Vegetable oil and animal fat are triglycerides — three fatty acid chains attached to a glycerol backbone. They are too viscous to burn well in a diesel engine. Transesterification breaks the triglyceride apart:

Triglyceride + 3 Methanol → 3 FAME (biodiesel) + Glycerol

• FAME = Fatty Acid Methyl Ester — this is biodiesel
• The reaction requires a catalyst (lye: sodium hydroxide NaOH or potassium hydroxide KOH)
• The reaction is reversible, so you need excess methanol to push it to completion

Catalyst: Lye

• Sodium hydroxide (NaOH): The standard catalyst. Produces solid glycerin that separates easily. Use 3.5 g per liter of oil (for clean, fresh oil)
• Potassium hydroxide (KOH): Alternative catalyst. Produces liquid glycerin. Easier to dissolve in methanol. Use 7 g per liter of oil
• Sourcing lye: Drain cleaner (check label: must be 100% NaOH or KOH, no additives). Or produce from wood ash — more labor-intensive but fully renewable

Free Fatty Acid Problem

Used cooking oil and rancid fat contain free fatty acids (FFA) — loose fatty acid molecules not attached to glycerol. FFA reacts with lye to form soap instead of biodiesel. This ruins the batch.

Solution: Perform a titration test (described below) to determine how much extra lye is needed to neutralize the FFA before the transesterification reaction begins. Fresh oil has minimal FFA; heavily used oil can have 5-15% FFA.

Feedstock Sources

Waste Cooking Oil

The most accessible feedstock in a post-collapse world — any settlement that fries food produces waste oil:

• Filter through cloth to remove food particles
• Heat to 120°C briefly to drive off water (water causes soap formation)
• Dark color is fine; rancid smell is fine
• The worse the oil smells, the more lye you will need (higher FFA)

Animal Fats

Tallow (beef/mutton) and lard (pork) make excellent biodiesel:

• Must be rendered and filtered (same process as for lamp fuel)
• Higher melting point means the biodiesel may gel in cold weather
• Mix 50/50 with vegetable oil biodiesel for better cold performance

Oilseed Crops

For sustainable, long-term production:

• Sunflower: 40-50% oil by weight. Easy to grow. 400-600 liters of oil per hectare
• Rapeseed / canola: 38-44% oil. Cold-tolerant. 500-700 liters/hectare
• Soybeans: 18-20% oil. Lower yield but nitrogen-fixing
• Flax / linseed: 35-45% oil. Cold climate crop

Extracting oil requires a seed press — a screw press or hydraulic press capable of 200+ kg/cm² pressure.

Production Process

Step 1: Titration (For Used Oil Only)

Determine how much extra lye is needed:

1. Dissolve 1 g NaOH in 1 liter of water (0.1% solution)
2. Dissolve 1 ml of your oil in 10 ml of isopropyl alcohol (rubbing alcohol)
3. Add drops of the NaOH solution to the oil/alcohol mix, stirring after each drop
4. Use phenolphthalein indicator (if available) or pH strips — you are looking for the point where the solution turns and stays pink (pH 8-9)
5. Count the ml of NaOH solution used. This number plus 3.5 = total grams of NaOH per liter of oil

Example: If titration uses 2 ml, you need 2 + 3.5 = 5.5 g NaOH per liter of oil.

Fresh, unused oil can skip titration — use the base amount (3.5 g NaOH or 7 g KOH per liter).

Step 2: Prepare the Methoxide

WARNING: Methanol is toxic (blindness, death if ingested). Lye is caustic. Methoxide (methanol + lye) is both. Wear gloves, eye protection, and work outdoors or in a well-ventilated area.

1. Measure 200 ml of methanol per liter of oil (20% by volume)
2. Add the calculated amount of lye to the methanol in a sealed container
3. Shake/stir until the lye dissolves completely (5-10 minutes for NaOH, faster for KOH)
4. This solution is sodium methoxide — extremely corrosive. Handle with care

Step 3: Reaction

1. Heat your oil to 55-60°C (not higher — methanol boils at 64.7°C)
2. Pour the methoxide into the warm oil
3. Stir vigorously for 1 hour (a paint mixer on a drill works well, or mechanical stirrer)
4. Consistent, thorough mixing is critical — the reaction happens at the interface between methanol and oil

Step 4: Settling & Separation

1. Pour the mixture into a tall, narrow container (a clear water cooler jug is ideal)
2. Let sit undisturbed for 8-24 hours
3. Glycerin sinks to the bottom — dark brown, thick, viscous
4. Biodiesel floats on top — amber/golden, much thinner than the original oil
5. Drain the glycerin from the bottom (a valve at the bottom of the container helps)
6. If no clear separation occurs, the reaction failed — likely too much water or insufficient lye

Step 5: Washing

Raw biodiesel contains residual methanol, lye, soap, and glycerin that must be removed:

1. Gently add water equal to 1/3 the biodiesel volume (warm water, 40-50°C)
2. Stir very gently — vigorous stirring creates an emulsion that takes days to settle
3. Let separate for 2-4 hours. Drain the milky water from the bottom
4. Repeat 3-4 times until the wash water runs clear
5. After final wash, heat biodiesel to 100°C for 15 minutes to evaporate residual water

Step 6: Quality Check

Good biodiesel:

• Clear — no cloudiness or haze (haze = water content)
• Golden amber color (from vegetable oil) or pale yellow (from tallow)
• Thin — noticeably less viscous than the original oil
• Burns cleanly — put a small amount in an oil lamp: should burn with a clean, bright flame and minimal smoke

The 3/27 conversion test: Mix 3 ml of biodiesel with 27 ml of methanol. If it dissolves completely (clear solution), the conversion was successful. If it turns cloudy or separates, unconverted oil remains — re-process with fresh methoxide.

Cold Weather Performance

Biodiesel gels at higher temperatures than petroleum diesel:

Feedstock	Cloud Point (°C)	Pour Point (°C)
Rapeseed/canola	-3 to 0	-9 to -15
Sunflower	0 to 2	-6 to -12
Soybean	0 to 2	-4 to -8
Tallow	12 to 16	8 to 12
Lard	8 to 12	4 to 8

Solutions for cold weather:

• Blend with petroleum diesel (B50 = 50% biodiesel) if available
• Use canola/rapeseed feedstock (lowest gel point)
• Insulate fuel lines and tank
• Keep engine warm between uses

Glycerin Byproduct

Every 10 liters of biodiesel produces roughly 1-1.5 liters of glycerin:

• Soap making: Crude glycerin with residual lye is already halfway to soap. Add water and heat gently — the soap separates. See soap-making
• Composting: Raw glycerin is a carbon source for compost piles
• Fire starting: Dried glycerin burns hot — useful as a fire starter
• Do not dump into waterways — glycerin depletes dissolved oxygen and kills aquatic life

Yield & Scale

• 1 liter of vegetable oil → ~1 liter of biodiesel (yields are near 1:1 by volume)
• 1 hectare of sunflowers → 400-600 liters of biodiesel per year
• A diesel generator consuming 2 liters/hour running 4 hours/day needs ~3,000 liters/year — requiring 5-7 hectares of dedicated oilseed crop
• This is a community-scale operation (Phase 3-4), not individual homestead

See Also

• ethanol-fuel-production — Alternative liquid fuel from fermentation
• biomass-gasification — Gaseous fuel from wood
• wood-gas-vehicles — Another option for powering vehicles

Equipment List

Minimum equipment for a small-scale biodiesel operation (20-50 liters per batch):

Item	Source	Purpose
Large pot or drum (60+ liters)	Salvage	Reaction vessel
Thermometer (0-120°C)	Salvage/lab	Temperature monitoring
Drill with paint mixer attachment	Salvage	Stirring
Clear container with drain valve	Build from jug + tap	Settling/separation
pH strips or phenolphthalein	Pharmacy/lab salvage	Titration
Safety gear (gloves, goggles)	Salvage	Protection from lye and methanol
Methanol (5 liters per 25L oil)	Salvage from fuel/solvent stores	Reactant
NaOH or KOH	Drain cleaner aisle	Catalyst
Cloth for filtering	Any cotton fabric	Oil pre-filtering

Batch Record Keeping

Keep a log for every batch. Over time, you will dial in the exact lye amount for your local oil sources:

• Date: When processed
• Oil source: Type and origin (e.g., “restaurant fryer oil, sunflower, heavily used”)
• Titration result: ml of NaOH solution used
• Lye amount used: Total grams per liter
• Methanol amount: ml per liter of oil
• Reaction temperature and time: °C and hours of mixing
• Separation quality: Did glycerin separate cleanly? How many hours?
• Wash cycles: Number of washes before water ran clear
• Final quality: Clear/cloudy, burn test result, 3/27 test pass/fail
• Yield: Liters of finished biodiesel from liters of input oil