This method works well if you need a max of a few liters of oil, like for a science fair project or small scale set-up.
All Steps based on 3 gallons of algae solution/culture. Algae content within culture varies, depending on thickness and opaque-ness of culture before oil extraction begins.
Algae oil is harvested in a variety of ways, but this is the easiest way for small scale biodiesel production, or algae oil harvesting.
Algae oil is called lipid oil, and it is found within the algae cell itself. You must break the resilient cell wall to release the oil. Some strains can contain around 60-70% oil, while others contain very little. Picking a stain is dependent on 3 factors: Time it takes to grow, hardy-ness or easiness of growing it, and the percentage of oil within each algae cell. I prefer the following strains: Chlorella vulgaris, Scenedesmus quadricauta, and Nannochloropsis oculata. There are a few places online I have found to be convenient in buying algae, listed later in this instructable.
Comment for questions---This is the brief version of how to do this, instructables crashed and did not save my work first time around.
Step 1: Vegetable Oil Biodiesel
Time: should take 1-2 hours
****MUST wait 2 days to let the biodiesel settle/separate before burning.****
This can be scaled down using ratios of desired amount of oil: NaOH and oil: Methanol
The below process is called a transesterification reaction.
1. Warm 100ml of oil (pick one) on a hot plate 50 degrees centigrade (10-15min)
2. Use a mortar and pestle to ground sodium hydroxide pellets into a fine powder
3. Measure out 0.35 grams of sodium hydroxide
4. Use a graduated cylinder to measure 20ml of methanol
5. Pour the methanol and the sodium hydroxide into 250ml (or larger) Erlenmeyer flask with a magnetic stirrer bar inside
6. Place solution on a magnetic stirrer plate and wait for the sodium hydroxide to completely dissolve into the methanol (5-10 min)
7. Cover solution to avoid dilution (Sodium Hydroxide + Methanol = Methoxide Solution)
8. Pour warm oil into the methoxide solution while it is still on the magnetic stirrer plate.
9. Keep stirrer on medium for 30 minutes
10. Place solution on a hot plate at 50 degrees centigrade (while stirring)(If using a digital hotplate, it should be set to ~65 C)
11. Wait two days for the glycerin to separate from the oil
12. Remove Glycerine with a pipette from the bottom of the beaker (the glycerine is a dense, darker, thin, layer that appears at the bottom of the beaker after allowing the solution to settle for 2 days)
13. What is left is biodiesel.
If the oil you use is mainly saturated (very thick or even solid at room temp.), there will be more than 2 layer after two days of waiting/sattling od solution. The very bottom think/dark layer should always be removed. Any other layers can be re-mixed, or you can just use the least sense layers, either way, all layers (except the bottom gycerine layer) are part of the biodiesel and will burn. The issue of including/mixing the layers of biodiesel is that they are of different density, so if the fuel sits for too long it will stratify again and the densest layer will require the most energy to combust. Another thing to consider, you don't want fuel the consistency of honey in your car.