Vegetable oils, animal fats, algae oil, and waste oils can be used to make clean-burning, renewable bio-diesel. Bio-diesel can be used in place of or mixed with petroleum-derived diesel.

LeMar Industries offers complete plants for biodiesel production using ultrasound cavitation technologies. Using ultrasound, the process of making biodiesel can be made into a continuous as opposed to a batch process; this will significantly increase the production scale and the biodiesel yield can be expected to increase by 8 – 14%.

Conversion process of bio-oil to fatty acid methyl esters (FAME) – biodiesel is known as esterification. Esterification is done by mixing vegetable oils (from algae, corn, soybeans, etc) with alcohol (methanol) and using diluted caustic soda (NaOH) as a catalyst. The resulting reaction produces fatty acid methyl esters (FAME), glycerol by-product, and soap by-product.

Esterification is a mass-transfer limited process as the methanol/NaOH is relatively immiscible with the oil; the conversion of oil into FAME molecules depends on having a high surface area of interaction between these two fluids. This process normally takes 1 – 4 hours in a heated (65°C) batch reactor, however, using the assistance of ultrasound (Industrial Sonomechanics ISP-3000) this process can take as little as 10 – 40 minutes with minimal heat addition. High-intensity ultrasound thoroughly mixes extracted oil with the diluted caustic soda/methanol by creating cavitation bubbles. Temperatures and pressures within the cavitation bubbles can reach 9000°F and 1000 atmospheres within a microsecond. Upon bubble implosion, temperatures and pressures immediately drop back to ambient conditions. The instantaneous heating provides kinetic energy to initiate the esterification reaction while the bubble creation/implosion thoroughly mixes the reagents into a nanoemulsion. The two different methods are compared below:

Batch Reactor Processing  (see screenshot)

Ultrasound Assisted Processing

Low reaction rate as it is limited by limited contact area between fluids; the reaction itself can take 1 – 4 hours

High reaction rate as oil and alcohol are thoroughly mixed into a nanoemulsion; the reaction takes place in 10 – 40 minutes

Long separation time (5-10 hours) as excess methanol and glycerol mix and this makes it harder to separate excess methanol from the biodiesel (FAME molecules)

Shorter separation time (30 minutes) of methanol  and glycerol as less methanol is used

Complicated post-processing: Biodiesel must be washed of excess catalyst and by-product soap

Lower excess methanol reduces the amount of energy/capital for its washing; the amount of caustic catalyst can be reduced by 50 – 60%

Heating is necessary to initiate reaction; typical reaction temperature is around 65°C

Exposure to high-intensity cavitation provides the activation energy needed for the reaction; pre-heating becomes significantly less important or in some cases unnecessary