Ultrasonic mixing is the superior technology for highly efficient and cost-effective biodiesel production. Ultrasonic cavitation improves mass transfer drastically, thereby reducing production costs and processing duration. At the same time, poor-quality oils and fats (e.g., waste oils) can be used and biodiesel quality is improved. Hielscher Ultrasonics supplies high-performance, robust ultrasonic mixing reactors for any production scale. Read more how your biodiesel production will benefit from sonication !

Biodiesel Production Benefits using Ultrasound

Biodiesel (fatty acid methyl ester, abrev. FAME) is the product of a transesterification reaction of lipid raw material (triglycerides, e.g., vegetable oil, spent cooking oils, animal fats, algal oil) and alcohol (methanol, ethanol) using a catalyst (e.g., potassium hydroxide KOH).
The Problem: In conventional biodiesel conversion using conventional stirring, the immiscible nature of the both reactants of the transesterification reaction of oil and alcohol leads to poor mass transfer rate resulting in an inefficient biodiesel production. This inefficiency is characterised by long reaction times, higher methanol-oil molar ratios, high catalyst requirements, high process temperatures and high stirring rates. These factors are significant cost drivers making conventional biodiesel manufacturing an expensive process.
The Solution: Ultrasonic mixing emulsifies the reactants in a highly efficient, rapid and low-cost manner so that the oil-methanol ratio can be improved, catalyst requirements are reduced, reaction time and reaction temperature are lowered. Thereby, resources (i.e., chemicals and energy) as well as time are saved, processing cost are reduced, whilst biodiesel quality and production profitability are significantly improved. These facts turn ultrasonic mixing in the preferred technology for efficacious biodiesel manufacturing.
Research and industrial biodiesel producers confirm that ultrasonic mixing is a highly cost-effective way to produce biodiesel, even when poor-quality oils and fats are used as feedstock. The ultrasonic process intensification considerably improves the conversion rate reducing the use of excess methanol and catalyst, allowing to produce biodiesel meeting the quality standard of ASTM D6751 and EN 14212 specifications. (cf. Abdullah et al., 2015)

Transesterification of triglycerides into biodiesel (FAME) using sonication results in accelerated reaction and significantly higher efficiency.

Numerous Advantages of Ultrasonic Mixing in Biodiesel Production

Ultrasonic mixing reactors can be easily integrated into any new installation as well as retro-fitted into existing biodiesel plants. The integration of a Hielscher ultrasonic mixer turns any biodiesel facility into a high-performance production plant. Simple installation, robustness and user-friendliness (no specific training for operation required) allow for the upgrade of any facility to a highly efficient biodiesel plant. Below, we present you with scientifically proven results of advantages documented by independent third parties. The numbers prove the superiority of ultrasonic biodiesel mixing over any conventional stirring technique.

The flowchart shows the biodiesel production steps including ultrasonic mixing for improved process efficiency.

Efficiency and Cost Comparison: Ultrasonics vs Mechanical Stirring

Gholami et al. (2021) present in their comparative study the advantages of ultrasonic transesterification over mechanical stirring (i.e., blade mixer, impeller, high shear mixer).
Investment costs: The ultrasonic processor and reactor UIP16000 can produce 192–384 t biodiesel/d with an footprint of only 1.2m x 0.6m. In comparison, for mechanical stirring (MS) a much larger reactor is required due to the long reaction time in the mechanical strirrng process, which causes the reactor cost to increase significantly. (cf. Gholami et al., 2020)
Processing costs: The processing costs for ultrasonic biodiesel production are 7.7% lower than those for the stirring process, mainly because of the lower total investment for the sonication process. The cost of chemicals (catalyst, methanol/alcohol) is the third-largest cost driver in both processes, sonication and mechanical stirring. However, for ultrasonic biodiesel conversion the costs for chemical are significantly lower than for the mechanical stirring. The cost fraction for chemicals accounts for approx. 5% of the final biodiesel cost. Due to the lower consumption of methanol, sodium hydroxide, and phosphoric acid, the cost for chemicals in the ultrasonic biodiesel process is 2.2% lower than that of the mechanical stirring process.
Energy costs: The energy consumed by the ultrasonic mixing reactor is approximately three times lower than that by the mechanical stirrer. This considerable reduction in energy consumption is a product of the intense micro-mixing and reduced reaction time, resulting from the production and collapse of countless cavities, which characterize the phenomenon of acoustic / ultrasonic cavitation (Gholami et al., 2018). In addition, compared to the conventional stirrer, energy consumption for methanol recovery and biodiesel purification stages during the ultrasonic mixing process is reduced by 26.5% and 1.3%, respectively. This decline is due to the lower amounts of methanol entering these two distillation columns in the ultrasonic transesterification process.
Waste disposal costs: Ultrasonic cavitation technology also remarkably reduces the cost of waste disposal. This cost in the sonication process is roughly one-fifth of that in the stirring process, resulting from the significant decrease in waste production due to higher reactor conversion and lower amounts of consumed alcohol.
Environmental-friendliness: Due to the very high overall efficiency, the reduced chemical consumption, lower energy requirements and reduced waste, ultrasonic biodiesel production is significantly more environmental-friendly than conventional biodiesel manufacturing processes.

Conclusion – Ultrasonics Improves Biodiesel Production Efficiency

The scientific assessment shows the clear advantages of ultrasonic mixing over conventional mechanical stirring for biodiesel production. The advantages of ultrasonic biodiesel processing include total capital investment, total product cost, net present value and internal rate of return. The amount of total investment in the ultrasonic cavitation process was found to be lower than that of other by approximately 20.8%. Using ultrasonic reactors reduced the product costs by 5.2% – using virgin canola oil. Since sonication allows to process also spent oils (e.g., used cooking oils), the production costs can be reduced significantly further. Gholami et al. (2021) come to the conclusion that due to a positive net present value, the ultrasonic cavitation process is the better choice of mixing technology for biodiesel production.
From the technical point of view, the most important effects of ultrasonic cavitation span the significant process efficiency and reduction in reaction time. The formation and collapse of numerous vacuum bubbles – known as acoustic / ultrasonic cavitation – reduce the reaction time from several hours in the stirred-tank reactor to a few seconds in the ultrasonic cavitation reactor. This short residence time allows biodiesel production in a flow-through reactor with a small footprint. The ultrasonic cavitation reactor also shows beneficial effects on energy and material requirements, reducing the energy consumption to nearly one-third of that consumed by a stirred-tank reactor and methanol and catalyst consumption by 25%.
From the economic perspective, the ultrasonic cavitation process’s total investment is lower than that of the mechanical stirring process, mainly due to nearly 50% and 11.6% reduction in the reactor cost and the methanol distillation column cost, respectively. The ultrasonic cavitation process also reduces biodiesel production cost due to a 4% reduction in canola oil consumption, lower total investment, 2.2% lower chemicals consumption, and 23.8% lower utility requirements. Unlike the mechanically stirred process, the ultrasonic processing is an acceptable investment due to its positive net present value, shorter payback time, and a higher internal rate of return. In addition to the techno-economic benefits associated with the ultrasonic cavitation process, it is more environmentally-friendly than the mechanical stirring process. Ultrasonic cavitation results in an 80% reduction in waste streams due to the higher conversion in the reactor and reduced alcohol consumption in this process. (cf. Gholami et al., 2021)

Use the Catalyst of Your Choice

Ultrasonic transesterification process of biodiesel has been proven as efficient using both alkaline or basic catalysts. Forinstance, Shinde and Kaliaguine (2019) compared the efficiency of ultrasonic and mechnical blade mixing using various catalysts, namely sodium hydroxide (NaOH), potassium hydroxide (KOH), (CH₃ONa), tetramethyl ammonium hydroxide and four guanidines (Propyl-2,3-dicyclohexyl guanidine (PCHG), 1,3-dicyclohexyl 2 n-octyl guanidine (DCOG), 1,1,3,3-tetramethyl guanidine(TMG), 1,3-diphenyl guanidine (DPG)). Ultrasonic mixing (at 35º) as shown superior for biodiesel production excelling mechanical mixing (at 65º) by higher yields and conversion rate. The efficiency of mass transfer in the ultrasound field enhanced the rate of transesterification reaction as compared with mechanical stirring. Sonication outperformed mechanical stirring for all tested catalysts. Running the transesterification reaction with ultrasonic cavitation is an energy efficient and industrially viable alternative for biodiesel production. Besides the widely used catalysts KOH and NaOH, both guanidine catalysts, propyl-2,3 dicyclohexylguanidine (PCHG) and 1,3-dicyclohexyl 2 n-octylguanidine (DCOG), have both been shown as interesting altrnatives for biodiesel conversion.
Mootabadi et al. (2010) investigated ultrasonic-assisted biodiesel synthesis from palm oil using diverse alkaline metal oxide catalysts such as CaO, BaO and SrO. The activity of the catalyst in ultrasonic-assisted biodiesel synthesis was compared with the traditional magnetic stirring process, and it was found that the ultrasonic process showed 95.2% of yield using BaO within 60 min reaction time, which otherwise take 3–4 h in the conventional stirring process. For ultrasonically-assisted transesterification at optimum conditions, 60 min was required to achieve 95% yield compared to 2–4 h with conventional stirring. Also, the yields achieved with ultrasound in 60 min increased from 5.5% to 77.3% using CaO as catalysts, 48.2% to 95.2% using SrO as catalysts, and 67.3% to 95.2 using BaO as catalysts.

Biodiesel production using various guanidines (3% mol) as catalyst. (A) Mechanical stirring batchreactor: (methanol:canola oil) 4:1, temperature 65ºC; (B) Ultrasound batch reactor: ultrasonicator UP200St, (methanol:canola oil) 4:1, 60% US amplitude, temperature 35ºC. Ultrasound-driven mixing outperforms mechanical stirring by far.
(Study and graphs: Shinde and Kaliaguine, 2019)

High Performance Ultrasonic Reactors for Superior Biodiesel Processing

Hielscher Ultrasonics offers high-performance ultrasonic processors and reactors for improved biodiesel production resulting in higher yields, improved quality, reduced processing time and lower production costs.

Small and Medium Scale Biodiesel Reactors

For small and medium size biodiesel production of up to 9ton/hr (2900 gal/hr), Hielscher offers you the UIP500hdT (500 watts), UIP1000hdT (1000 watts), UIP1500hdT (1500 watts), and UIP2000hdT (2000 watts) ultrasonic high-shear mixer models. These four ultrasonic reactors are very compact, easy to integrate or retro-fit. They are built for heavy duty operation in harsh environments. Below you will find recommended reactor setups for a range of production rates.

Very Large-Throughput Industrial Biodiesel Reactors

For industrial processing biodiesel production plants Hielscher offers the UIP4000hdT (4kW), UIP6000hdT (6kW), UIP10000 (10kW) and UIP16000hdT (16kW) ultrasonic homogenizers! These ultrasonic processors are designed for the continuous processing of high flow rates. The UIP4000hdT, UIP6000hdT and UIP10000 can be integrated into standard sea freight containers. Alternatively, all four processor models are available in stainless steel cabinets. An upright installation requires minimal space. Below you find recommended setups for typical industrial processing rates.