Converting microalgae into fuel

In most parts of the world, the food vs fuel debate and low yield per unit resource consumption have put a lid on every attempt to convert first- and second-generation energy feedstocks respectively into fuel.

This is where third generation feedstocks like microalgae assume significance.

First-generation feedstocks are those that can also be consumed as human food (e.g., corn, sugarcane, wheat); second-generation feedstocks are not normally used for human consumption (e.g., waste materials); while third-generation feedstocks take advantage of specially engineered micro-organisms such as microalgae as their energy source.

Figure 1. Processing alternatives for microalgae

Various methods have emerged to convert third generation feedstocks into fuel (see figure 1). However, no clear solutions have been found to convert microalgae into high quality and reliable gaseous fuel. This is what inspired Pratik Gholkar, a researcher with the IITB-Monash Research Academy, to try and develop a catalytic process to convert microalgae into tar- and char-free syngas.

Tar cleaning is one of the major obstacles in commercialising the microalgal gasification technology. It can be achieved using high temperature (1000°C – 1200°C) gasification; however, this is an energy-intensive process. Pratik’s preliminary results have shown that reactive flash volatilization can be used to clean tar at temperatures as low as 600°C – 700°C.

“Tar formation limits the application of gasification technology for conversion of microalgae into gaseous fuels,” he explains. “Wet processing is limited by high temperature and pressure requirements. In dry processing, however, the transesterification reaction is limited by low lipid extraction efficiency, resulting in low overall conversion. We have chosen reactive flash volatilisation because it has clear advantages like single step conversion, high space velocity, small reactor size, and tunability of the CO-to-H2 ratio. Besides, it is tar- and char-free.”

“The path we followed was difficult, and there were times we considered looking for alternatives,” he adds. “However, a small alteration in the process was the game-changer.”

Figure 2. Process Flow Diagram

“We have also filed two provisional process patents related to our work,” says Pratik excitedly, “Catalytic conversion of microalgae into hydrogen-rich syngas using reactive flash volatilisation, and Catalytic conversion of microalgae into methane-rich syngas using reactive flash volatilisation.”

Prof Murali Sastry, CEO of the IITB-Monash Research Academy, is excited as well. “Never in history has the need for clean fuel been so critical. While easily accessible crude oil reserves are depleting, ambient carbon dioxide levels have reached alarming levels due to emissions. Pratik is on to something big. Through this single-step method, microalgae can be converted into tar- and char-free syngas in less than two seconds! This has not been reported in literature, and could lead to a new conversion process that can handle competitive reaction equilibriums in a single reactor. Since whole microalgae is used as a reactant, no additional unit-operation such as extraction is required. The implications for the renewable energy sector are huge.”

The IITB-Monash Research Academy is a collaboration between India and Australia that endeavours to strengthen scientific relationships between the two countries. Graduate research scholars like Pratik study for a dually-badged PhD from both IIT Bombay and Monash University, spending time at both institutions to enrich their research experience

Pratik’s project is funded by JSW.

Research scholar: Pratik Gholkar, IITB-Monash Research Academy

Project title: Catalytic conversion of microalgae into tar free methane rich gas using reactive flash volatilization.

Supervisors: Prof Yogendra Shastri, Prof Akshat Tanksale

Contact details: pratik.gholkar@monash.edu

This story was written by Mr Krishna Warrier based on inputs from the research student, his supervisors and IITB-Monash Research Academy. Copyright IITB-Monash Research Academy.