Microalgae-derived biogas a promising alternative to fossil fuels

Feb 24, 2014 by Jan Overney
Microalgae-derived biogas a  promising alternative to fossil fuels
Credit: Applied Science University of Zurich ZHAW – Dominik Refardt, 2013

Could microalgae fuel the future? Researchers are fine-tuning a technology that transforms wet algal biomass into a biogas that is compatible with today's natural gas infrastructure.

Microalgae derived biogas is becoming an increasingly promising alternative to fossil fuels. Over the past years, researchers at the Paul Scherrer Institute (PSI) and EPFL have been developing SunCHem, a resource and energy efficient process, to cultivate microalgae and convert them into synthetic , a biofuel that is fully compatible with today's expanding gas grid. In an article published in late January 2014, they present one of the first continuous biomass to biogas conversion technologies. The article appeared online in the journal Catalysis Today.

While it takes nature millions of years to transform biomass into biogas, it takes the SunCHem process less than an hour. The secret behind this feat is a process called . First, algae-rich water is heated under pressure to a supercritical liquid state, to almost 400 degrees Celsius. In this , the water effectively dissolves the organic matter contained in the biomass, while inorganic salts become less soluble and can be recovered as a nutrient concentrate. By gasifying the remaining solution in the presence of a catalyst, it is then split into water, CO2, and the methane rich biogas.

Although the approach is still about five to seven times too expensive to compete with natural gas, microalgae evade much of the criticism that other biofuel sources face. They can be grown in raceway ponds built on non-arable land, without competing with agricultural food production. And although the algae need water to grow in, they are not picky. Depending on the species, they can grow in freshwater or saltwater, and in the future, they could potentially even be used to treat wastewater. A study published last year estimated that, for each unit of energy spent to produce the , between 1.8 and most optimistically 5.8 units of energy could be produced.

To save resources, cut costs, and increase the overall efficiency of the process, the entire system can be run in a closed loop. "Some nutrients such as phosphate are limited resources, which we can recover when we gasify the biomass. Feeding them back into the water that we grow the algae in has a spectacular effect on their growth," says Mariluz Bagnoud, one of the two lead authors of the publication.

For the publication, the researchers proved the feasibility of running the system as a continuous process. But they also found that feeding back water and nutrients over long durations leads to a degradation of the system's performance. "We detected the deactivation of the catalyst used in the gasification process and we expect the accumulation of trace amounts of aluminum," says Bagnoud. "The toxicity of the aluminum on the microalgae depends on the pH. By cultivating the algae at a neutral pH, these toxic effects can essentially be eliminated," she says. "Now, the next steps will involve fine-tuning the process to increase the longevity of the catalyst, which is deactivated by the sulfur contained in the microalgae," she concludes.

Explore further: Wastewater treatment using microalgae enables phosphorous and nitrogen removal in darkness

More information: Mariluz Bagnoud-Velásquez, Martin Brandenberger, Frédéric Vogel, Christian Ludwig; "Continuous catalytic hydrothermal gasification of algal biomass and case study on toxicity of aluminum as a step toward effluents recycling." Catalysis Today, Volume 223, 15 March 2014

add to favorites email to friend print save as pdf

Related Stories

Synthetic natural gas from excess electricity

Jan 06, 2014

"Power to gas" is a key concept when it comes to storing alternative energy. This process converts short-term excess electricity from photovoltaic systems and wind turbines into hydrogen. Combined with the ...

Turning algae into fuel

Sep 04, 2013

Blue-green in colour, slimy and present in seas and fresh water worldwide - the presence of microalgae is not generally met with great excitement. But this may be about to change. A team of European scientists ...

Recommended for you

Future solar panels

7 minutes ago

Conventional photovoltaic technology uses large, heavy, opaque, dark silicon panels, but this could soon change. The IK4-Ikerlan research centre is working with the UPV/EHU-University of the Basque Country within the X10D ...

Storing solar energy

Sep 01, 2014

A research project conducted by Leclanché S.A., the Ecole Polytechnique Federale de Lausanne (EPFL), Romande Energie and with the financial support of the Canton of Vaud could bring a real added value in ...

Scientists get set for simulated nuclear inspection

Sep 01, 2014

Some 40 scientists and technicians from around the world will descend on Jordan in November to take part in a simulated on-site inspection of a suspected nuclear test site on the banks of the Dead Sea.

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

chaps
not rated yet Feb 24, 2014
Interesting; I'm happy to hear about new technologies being explored and such, but I have several concerns about this technology. For the most part, I believe nature knows best. All things considered, if it takes nature millions of years to produce biomass into biogas, I believe is for good reasons. I mean, at what cost are we trying to speed up such process? What energy input is going into this process. What are we going to do with the by-products!? Advertising the mass-market capabilities of this process without mentioning what will be done with the by-products is just plain foolish in my opinion. If we should strive for something remarkable, it should be something as environmentally sustainable as possible.
chaps
not rated yet Feb 24, 2014
Interesting; I'm happy to hear about new technologies being explored and such, but I have several concerns about this technology. For the most part, I believe nature knows best. All things considered, if it takes nature millions of years to produce biomass into biogas, I believe is for good reasons. I mean, at what cost are we trying to speed up such process? What energy input is going into this process. What are we going to do with the by-products!? Advertising the mass-market capabilities of this process without mentioning what will be done with the by-products is just plain foolish in my opinion. If we should strive for something remarkable, it should be something as environmentally sustainable as possible.
Eikka
not rated yet Feb 24, 2014
if it takes nature millions of years to produce biomass into biogas, I believe is for good reasons


That's just something to do with circumstances rather than "nature" having any reason to do anything.

Nature makes fossil fuels by crushing biomass and water under moving continents, because they just happen to be buried as the tectonic plates move around.

What are we going to do with the by-products!?


CO2, water and mineral salts? Make selzer water out of them and drink it.