Researchers from the Israeli Institute of Technology (Technion) have developed a new method that harvests an electrical current directly from seaweed in an environmentally friendly and efficient way. The idea, which came to the doctoral student Yaniv Shlosberg while swimming at the beach, has been developed by a consortium of researchers from three Technion faculties who are members of the Grand Technion Energy Program (GTEP), along with a researcher from the Israel Oceanographic and Limnological Research Institute (IOLR).
The problematic issues of fossil fuels are the driving force behind research into methods of alternative, clean and renewable energy sources. One of these is the use of living organisms as the source of electrical currents in microbial fuel cells (MFC). Certain bacteria can transfer electrons to electrochemical cells to produce electrical current. The bacteria need to be constantly fed and some of them are pathogenic.
A similar technology is bio-photoelectrochemical cells (BPEC). As for the MFC, the source of electrons can be from photosynthetic bacteria, especially cyanobacteria. Cyanobacteria make their own food from carbon dioxide, water and sunlight, and in most cases they are benign.
The research groups of Prof. Noam Adir, and the doctoral student Yaniv Shlosberg, previously developed technologies that used cyanobacteria for obtaining electrical current and hydrogen fuel, as published in Nature Communications and Science.
Cyanobacteria have some drawbacks, however. They produce less current in the dark, as no photosynthesis is performed. Also, the amount of current obtained is still less than that obtained from solar cell technologies, so that while more environmentally benign, the BPEC is less attractive commercially.
Switching from Cyanobacteria to Ulva
In this study, the researchers from the Technion and IOLR decided to try to solve this issue using a new photosynthetic source — seaweed. Many different species of seaweed grow naturally on the Mediterranean shore of Israel, especially Ulva (also known as sea lettuce) which is grown in large quantities at IOLR for research purposes.
The research was led by Prof. Noam Adir and Yaniv Shlosberg, from the Schulich Faculty of Chemistry and GTEP. They collaborated with additional researchers from the Technion: Dr. Tunde Toth (Schulich Faculty of Chemistry), Prof. Gadi Schuster, Dr. David Meiri, Nimrod Krupnik and Benjamin Eichenbaum (Faculty of Biology), Dr. Omer Yehezkeli and Matan Meirovich (Faculty of Biotechnology and Food Engineering) and Dr. Alvaro Israel from IOLR in Haifa.
The Technion/IOLR researchers built a prototype device that collects the current directly in the Ulva growth vat. After developing new methods to connect Ulva and BPEC, currents a thousand times greater than those from cyanobacteria were obtained — currents that are on the level of those obtained from standard solar cells. Prof. Adir notes that these increased currents are due to the high rate of seaweed photosynthesis, and the ability to use the seaweed in their natural seawater as the BPEC electrolyte — the solution that promotes electron transfer in the BPEC.
Additionally, the seaweed provides currents in the dark, about 50% of that obtained in light. The source of the dark current is from respiration — where sugars made by the photosynthetic process are used as an internal source of nutrients. In a fashion similar to the cyanobacterial BPEC, no additional chemicals are needed to obtain the current. The Ulva produce mediating electron transfer molecules that are secreted from the cells and transfer the electrons to the BPEC electrode.
The new technology is carbon negative. The seaweed absorbs carbon from the atmosphere during the day while growing and releasing oxygen. During harvesting of the currents during the day, no carbon is released. During the night, the seaweed releases the normal amount of carbon from respiration.
“By presenting our prototype device, we show that significant currents can be harvested from the seaweed,” said Prof. Adir. “We believe that the technology can be further improved leading to future green energy technologies.”
The researchers presented their new method for collecting an electrical current directly from seaweed in the journal Biosensors and Bioelectronics. The paper describes results obtained from researchers from the Schulich Faculty of Chemistry, the Faculty of Biology, the Faculty of Biotechnology and Food Engineering, GTEP and IOLR.
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