Crude Glycerol as a Potential Feedstock for Future Energy via Thermochemical Conversion Processes: A Review

Abstract

Biodiesel is an emerging substitute for petroleum-based products. It is considered an ecologically safe and sustainable fuel. The high cost of biodiesel production is linearly related to its feedstock. Crude glycerol, which is a by-product of the biodiesel industry, is also a major challenge that must be addressed. A large volume of crude glycerol needs to be disposed of, and this involves processing, dumping, and land requirements. This increases the cost of biodiesel production. One way to decrease the cost of biodiesel production is to utilize its by-product to make valuable products. Crude glycerol can be processed to produce a variety of chemicals and products. The present utilization of crude glycerol is not enough to bring down its surplus availability. Thermochemical conversion processes can utilize crude glycerol as a starting feedstock and convert it into solid, liquid, and gaseous fuels. The utilization of crude glycerol through integrated thermochemical conversion processes could lead to an integrated biorefinery. This review paper highlights the research scope for areas where crude glycerol could be utilized as a feedstock or co-feedstock in thermochemical conversion technology. Various thermochemical conversion processes, namely, gasification, pyrolysis, combustion, catalytic steam reforming, liquefaction, and supercritical water reforming, are discussed and shown to be highly suitable for the use of crude glycerol as an economical feedstock. It is found that the integration of crude glycerol with other thermochemical conversion processes for energy production is a promising option to overcome the challenges related to biodiesel production costs. Hence, this paper provides all the necessary information on the present utilization status of crude glycerol in thermochemical conversion processes, as well as identifying possible research gaps that could be filled by future research studies.

Sustainability of biodiesel production using immobilized enzymes: A strategy to meet future bio‐economy challenges

“…The cost of feedstock, which accounts for 70% of the cost of biodiesel production, is the most significant barrier to commercialization of biodiesel. Feedstock availability, catalyst type and concentration, the molar ratio of oil to alcohol, reaction temperature, reaction time, mixing intensity, water content, and agitation speed are the most significant elements to consider during biodiesel production 34,62 . The accessibility of feedstocks is an important factor of biodiesel production's economic viability as it accounts for almost 80% of the overall cost of biodiesel.…”

“…The transesterification conversion process is either chemical or enzymatic. 34 At present, the transesterification process is used on a commercial scale in many countries, like Malaysia, China, Brazil, and the USA. It is also a subject of investigation at the laboratory scale for continuous research and development.…”

“…Transesterification is the most widely used method among the different synthesis processes used for the production of biodiesel. The transesterification conversion process is either chemical or enzymatic 34 . At present, the transesterification process is used on a commercial scale in many countries, like Malaysia, China, Brazil, and the USA.…”

“…Feedstock availability, catalyst type and concentration, the molar ratio of oil to alcohol, reaction temperature, reaction time, mixing intensity, water content, and agitation speed are the most significant elements to consider during biodiesel production. 34,62 The accessibility of feedstocks is an important factor of biodiesel production's economic viability as it accounts for almost 80% of the overall cost of biodiesel. Several efforts have been made in this regard to find low-cost feedstock that is available throughout the year.…”

Estimation of Carbon Metabolism in Saccharomyces cerevisiae Acclimatized to Glycerol Assimilation with Quantitative PCR

“…Additionally, the use of the crude glycerol can also be attractive because it deeply relates to carbon recycling societies. Therefore, research and development for the effective use of the promising glycerol are strongly required based on the abundance and carbon recycling [4]. Microbial utilization is one such attractive method since several microorganisms exhibit a tolerance to the contaminants in crude glycerol and an ability to utilize glycerol as an alternate carbon source for sugars [2].…”