Electricity from sea lettuce 02.01.2022

Researchers at the Technion - the Israel Institute of Technology - have developed a new method to generate electrical current directly from seaweed in an environmentally friendly and efficient way.

The idea, which first occurred to Technion doctoral student Yaniv Schlosberg while swimming on the beach, was brought to fruition by a team of researchers from three Technion faculties that are members of the Technion's Large Energy Program (GTEP), along with a researcher from the Israel Institute of Oceanography and Limnology in Haifa (IOLR). ).

As is known, the combustion of fossil fuels leads to the emission of greenhouse gases and other pollutants that affect climate change, and various forms of environmental pollution occur at all stages of production, transportation, processing and consumption of these fuels. The climate crisis and environmental issues are driving the research and search for alternative, clean and renewable energy sources. One of them is the use of living organisms (eg bacteria) as a current source in microbial fuel cells (MFC) and BPEC biophotovoltaic cells. Some bacteria have the ability to transfer electrons, but they need to be constantly fed, and some of them are pathogenic.

An alternative source of electricity could be photosynthetic bacteria, especially cyanobacteria (also known as blue-green algae). Cyanobacteria themselves get their food from carbon dioxide, water and sunlight, and in most cases they are harmless - some of them, such as "spirulina", are generally considered "superfoods" and are grown in large quantities.

The research teams of professors Noam Adir and Gadi Schuster have already developed methods for using cyanobacteria to generate electricity and hydrogen fuel. However, cyanobacteria also have disadvantages - they produce less current in the dark, when there is no photosynthesis, and the energy received from them is less than from conventional solar cells. Therefore, BPEC technology, although more environmentally friendly, is less commercially attractive.

In their new work, researchers from the Technion and IOLR have tried to solve this problem using a new source of photosynthesis - algae. The study was led by Prof. Noam Adir and doctoral student Yaniv Schlosberg from the Technion Department of Chemistry and GTEP. They collaborated with other Technion researchers: Dr. Tunde Toth (Department of Chemistry), Prof. Gadi Shuster, Dr. David Merii, Nimrod Krupnik and Benjamin Eichenbaum (Department of Biology), Dr. Omer Yehezkeli and Matan Meyrovic (Department of Biotechnology and Food Engineering) and Dr. Alvaro Israel from IOLR in Haifa. Many types of seaweed grow naturally on Israel's Mediterranean coast - especially ulva (also known as sea lettuce), which is grown in large quantities at IOLR for research purposes.

By developing new ways to connect algae and BPEC, the researchers have obtained a current that is 1000 times stronger than that from cyanobacteria, and is at the level of standard solar cells. Professor Adir notes that this current strength is due to the high rate of photosynthesis of algae and the ability to use algae in their natural seawater as an electrolyte in BPEC. In addition, seaweed creates current in the dark, generating about 50% of the current in the light - in the dark, the energy source is algae respiration, in which the sugars obtained during photosynthesis are used for nutrition. As with cyanobacteria, no additional chemicals are required to produce the current. "Sea lettuce" releases intermediary molecules to carry electrons to the BPEC electrode, thus creating an electrical current.

Energy production technologies based on fossil fuels are known as "carbon positive". This means that when fuel is burned, carbon is released into the atmosphere. Solar cell technologies are known as "carbon neutral" and when they extract energy from the sun, no new carbon is really released into the atmosphere. However, the production of solar cells and their transportation to the place of use is many times more carbon-positive. The new bioelectricity technology developed at the Technion is truly "carbon negative" - ​​seaweed grows by absorbing atmospheric carbon during the day and releasing oxygen, and only at night they release carbon when they breathe. At the same time, seaweeds are already being cultivated on a mass scale for the food, cosmetic and pharmaceutical industries.