Biodiesel:

Biodiesel refers to a monoalkyl ester of fatty acids that is derived from vegetable oils or animal fats. It is produced through a process known as transesterification, which involves the reaction of oils with methanol (or other alcohols) to produce biodiesel and glycerol. This process is also called alcoholysis, with a common example being the production of rape seed oil methyl ester.

Production Process:

1. Traditional Process: Biodiesel is traditionally made using vegetable oils (e.g., soybean, sunflower, or canola oil) through transesterification with methanol. In this reaction, the triglycerides (oils) are broken down into biodiesel (monoalkyl esters) and glycerol as a byproduct.
2. Microalgae Biodiesel: Microalgae are increasingly used as feedstock for biodiesel production due to their high oil productivity and very low land area requirement. Microalgae can be cultivated in bioreactors, where they grow rapidly and produce large amounts of oils suitable for biodiesel production.
3. Alcohol Substitution: Traditionally, methanol is used in transesterification, but other alcohols from microbial fermentation, such as ethanol, propanol, and butanol, can be substituted for methanol. Even a mixture of alcohols characteristic of acetone-butanol fermentation can be employed. This opens up new avenues for biodiesel production by incorporating different microbial fermentation processes.

Glycerol and Biogas Production:

During the transesterification process, glycerol is produced as a byproduct. Glycerol can be fermented into valuable products such as 1,3-propanediol (used in plastics) or methane, which can be used in biogas plants. The methane can be utilized as a co-substrate for other fuels, thus improving the overall energy efficiency.

Concerns and Issues:

Despite the promising technology for converting plant oils to biodiesel, there are some concerns regarding the microorganisms involved in biodiesel degradation. These microorganisms can cause problems, especially when water content is unavoidable during bacterial oxidation, potentially leading to corrosion issues in engines.

Biodiesel Blends in Vehicles:

In many countries, including India, most diesel vehicles are designed and licensed to use biodiesel blends. Common blends include up to 5% biodiesel mixed with traditional diesel. However, engines running on biodiesel blends may require more frequent oil changes due to the effects of biodiesel on engine components.

Future Outlook:

The potential for biodiesel from microalgae looks promising for the future due to its high oil yield and minimal land requirement. With technological advancements, the integration of biologically fermented ethanol and butanol into the biodiesel process can offer a more feasible and economical option for sustainable energy production.