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Producing renewable hydrogen with microalgae

Australian researchers are part of an international team that has uncovered a new method of producing hydrogen and methane using renewable sources.

Researchers at Monash University’s Department of Chemical Engineering, IITB-Monash Research Academy Mumbai, and The Indian Institute of Technology’s Department of Chemical Engineering have used reactive flash volatilisation (RFV) to produce hydrogen using microalgae, giving rise to newer and cleaner forms of energy.

RFV is a gasification process that uses oxygen and steam that converts biomass or fossil fuel-based carbon materials into gases.

Hydrogen can be produced using microalgae in a practice called reactive flash volatilisation (RFV), a gasification technology. This results in 36% less greenhouse gas emissions compared to the current best-practice for hydrogen production, which involves steam reforming of methane.

Hydrogen is typically used in petroleum refining and fertiliser production, with hydrogen-fueled transport and utilities key emerging markets.

The research, published in the Journal of Cleaner Production, also shows that, with the cost of hydrogen at $10 per kilogram, by using RFV to produce the gas, the payback period on the initial investment would be just 3.78 years, with a 22% internal rate of return.

If the researchers’ process was to be used in hydro-electricity, carbon emissions could drop by as much as 87%.

While the current production of microalgae does not meet commercial demand, the researchers say that cultivation for energy applications could also provide additional revenue streams for rural communities, potentially making them self-sufficient.

“Hydrogen and methane are clean sources of fuel and green chemical synthesis only if they are produced from renewable resources," said Monash University Associate Professor Akshat Tanksale, a research co-author.

"At present, 96% of hydrogen and all methane is produced using non-renewable resources.”

Just add water

According to Tanksale, water and renewable electricity integration with microalgae harvesting can bring down the costs and increase the sustainability of hydrogen production from this process

“Microalgae as a feedstock is attractive due to its high carbon dioxide fixation efficiency, growth rate, photosynthetic efficiency, ability to grow in brackish water — like rivers and lakes — and the ability to cultivate it on land not suitable for agriculture,” he said.

Dr Yogendra Shastri from the Department of Chemical Engineering at IITB-Monash Research Academy Mumbai said that hydrogen is considered a clean fuel because it doesn’t lead to the emission of greenhouse gases when used.

“However, the production of hydrogen also needs to be sustainable,” Shastri said.

“Biodiesel production from microalgae is limited due to low lipid extraction efficiency — less than 20% — and the high cost of microalgae harvesting and drying.

“Furthermore, microalgae-based hydrogen and methane production haven’t yet been commercialised due to expensive pre-treatment, such as harvesting, drying and lipid extraction; low carbon conversion efficiency; and tar accumulation.”

Researchers performed the RFV of microalgae using temperatures ranging from 550-650°C and with steam as the gasifying agent. This meant dewatering or drying the microalgae wasn’t required, significantly reducing energy consumption.

While the costs to develop infrastructure to cultivate microalgae and then refine it into hydrogen and methane are expensive, the overall return on investment in the long-term could make hydrogen and methane cost-effective and environmentally friendly fuel sources.