Wealth out of Waste: Utilizing crude glycerol byproduct

 

The accelerated global warming is a direct result of burning fossil fuels. Coal, Petroleum, and Natural gas are some examples of fossil fuels. Replacing these fossil fuels with renewable energy sources helps reduce the rate at which global warming is progressing. Fuels obtained from non-fossil origin, are termed Renewable fuels, or Biofuels. Biofuels can be split into three categories:

1.    Solid Biofuels- Fuelwood, Wood Residue, Wood Pellets, etc.,

2.    Liquid Biofuels- Biogasoline, Biodiesel etc.,

3.    Biogases

In this article, our major focus is on the preparation procedure of Biodiesel and the utilization of its byproducts. Biodiesel is produced from biomass, consisting of Triglycerides as a major component. Depending on the acid value of the feed, and the type of catalyst used, the biomass is subjected to esterification, transesterification, or both. As a result of this process, we obtain the biodiesel product, and a glycerol by-product. The glycerol by-product is often termed as raw glycerol, waste glycerol, or crude glycerol. For every 10 billion gallons of biodiesel produced, 1 billion gallons of glycerol is released as a by-product.

Fig 1. Transesterification process

Glycerol is a simple, cheap, and abundant alcohol molecule. It is also known as Propane-1,2,3-triol. Glycerol is miscible in water, colorless, and is a highly viscous liquid. When the glycerol concentration is above 95% it is called glycerin. Pure glycerol is obtained from conversion actions based on vegetable oil, fat, animal tallow, and biorefineries. However, the crude glycerol obtained as a byproduct of the biodiesel production process occurs in a dark brown-colored liquid. It has a highly deteriorated pure glycerol value and is often accompanied by a faulty smell and a high pH. Crude glycerol consists of impurities such as methanol, soap, oils, and other organic materials.

Crude glycerol is subjected to a stepwise purification process, to increase its purity levels. The purification can be done by various methods such as distillation, acidification, adsorption, centrifugation, and microbial treatment before it is deemed fit for usage in the production of value-added products.

Till the year 2000, there were more than fifteen hundred end uses of glycerol in the chemical industry, particularly Soap and Detergent Industries. However, in the present, it is estimated that there are more than two thousand end uses of glycerol in industries. Some major examples of value-added products obtained from crude glycerol include ethanol, DHA, Citric Acid, Glyceric Acid, Succinic Acid, etc., 

Fig 2. Value-added products obtained from crude glycerol

 

With the increased demand for renewable fuels, the production rate of biofuels is rapidly increasing. With this increased rate, the obtained crude glycerol byproduct also increases. Utilization of crude glycerol will benefit not only the economy of the biodiesel industry but also the bio-based industries. When biodiesel industries themselves proceeded with the purification process of crude glycerol, it was found to be more economical compared to the market value of glycerol products. Also, these industries enjoy numerous benefits such as self-disposal of crude glycerol, zero liquid discharge, and elimination of risk contamination followed by legal sanctions. The technology of purifying crude glycerol, and utilizing it in the production of useful products will have a great impact on the economic and environmental sectors.

References:

S. Chozhavendhan, Kumar R, S. Elavazhagan, B. Barathiraja, Jayakumar M, Sunita Varjani. Utilization of Crude Glycerol from Biodiesel Industry for the Production of Value-Added Bioproducts. Springer eBooks. 2018 Jan 1;65–82.

Image Source:

• 1.   Cover Image: https://www.renovablesverdes.com/biometano/
• Fig 1 & Fig 2: Springer eBooks, ENESU, Waste to Wealth, https://link.springer.com/chapter/10.1007/978-981-10-7431-8_4