Oil is clearly the devil and hydrogen is evidently the fuel of the future. Now Israeli researchers have developed a "really green" power cell that produces electricity and hydrogen, using nothing but spinach, water and sunlight.
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"We used spinach, but you can use any leaf," says Prof. Noam Adir of the interdisciplinary Technion team that designed the breakthrough bio-photo-electro-chemical cell.
Why then use a popular salad ingredient rather than hydrangea or pine needles or some other non-crop plant?
Convenience, Adir explains. Historically, botanists researched photosynthesis using spinach because while all plants generate sugar from water and sunlight, spinach does so especially well. You can drop by the supermarket and pick some up. Also, spinach keeps well after purchase, meaning that its active components remain active.
The spinach cell may not save Las Vegas' lights from going out but it could be perfect for remote villages here on earth with modest power needs - or colonies in Mars, Prof. Noam Adir tells Haaretz. This clean, green power machinelet emits no contaminants, only spinach membrane slurry, which the brave could eat, the squeamish could use to fertilize gardens in Martian craters or wherever they please, and the indifferent could pour down the sink.
A gift to the world
Asked if there are practical real-world applications, Adir explains there's a problem with intellectual property rights: "You can't patent spinach."
Six years ago, they did similar work with bacteria that they mutated to get electricity, Adir told Haaretz, and they could patent the concept because of the mutation. Now they're sticking spinach it a blender for 20 seconds to make a spinach membrane "shake", which they place by the electrodes in the cell.
Since spinach is not patentable, for now the cell remains academic. "We are at the stage of investigating its feasibility, whether it would be of applicative interest to anybody," says the professor. "Patents are only good if you can protect them," he adds, noting that anybody can drop by the grocer and buy spinach, and the other cell components are nothing special. Essentially the scientists pursued the work, funded chiefly by the Israeli government but also using grants from the American and German federal authorities, because it matters. Rather than operating in stealth mode, as one does with patentable ideas, they published. "We did it because we thought it important," Adir sums up: "We’re not hiding it. We're telling the world."
So they are: the latest findings are reported in "Hybrid bio-photo-electro-chemical cells for solar water splitting," published this month in the prestigious journal Nature. The study was conducted by doctoral students Roy I. Pinhassi, Dan Kallmann and Gadiel Saper, under the guidance of Adir of the Schulich Faculty of Chemistry, Prof. Gadi Schuster of the Faculty of Biology and Prof. Avner Rothschild of the Faculty of Material Science and Engineering.
"We proved that energy can be made really green using material at negligible cost, with no contaminating synthetics, no expensive or rare or toxic elements," Adir says.
In order to harness photosynthesis by the spinach membranes to make electricity, the researchers added a non-toxic iron-based compound to the solution in the cell. This iron juice transfers electrons from the membranes to the electrical circuit, known in English as creating a current. The electrical current can be utilized to form hydrogen gas by adding electric power from a small photovoltaic cell that absorbs the excess light. This enables solar energy to be converted into chemical energy that is stored as hydrogen gas formed inside the BPEC cell. This energy can be converted when necessary into heat and electricity by burning the hydrogen, in the same way hydrocarbon fuels are used.
Unlike oil-based fuels, which emit greenhouse gases when burned, the product of hydrogen combustion is clean water. The Technion cell is a closed cycle: it begins with water and ends with water and can be used to produce and store hydrogen gas.
Powering the house with the lawn
Centralized mass energy production is more efficient, but it creates two key problems. Vast distribution involves vast energy waste in distribution and two, not everybody lives near the grid.
This is where the cell could come in: remote places that don't need a lot of power. "Not like our society which is very energy-intensive. Sometimes all one needs is enough for light and to charge the cellphone. My dream is to get up in morning, cut the grass, put it into the machine, come back in evening and have enough power to run the home," says Adir.
One issue that may need resolving is shelf life. The membranes in the spinach slush die in 20 minutes, Adir says. "We remove the old membranes, put in new and the machine keeps working. We're talking about nearly nothing."
Another team working on nearly nothing that could save the planet is at Tel Aviv University, where Assistant Prof. Iftach Yacoby is leading research on engineering microscopic algae to cleanly produce hydrogen.
But back to our spinach cell. How much of this nearly nothing will it take to power a house? "A hundred micrograms of spinach membrane shake gives me half a milliamp per centimeter squared of electricity," he says, and elaborates: "The Israel Electric Corporation might not be impressed but on Mars, where you have to grow food and need oxygen and need hydrogen, this does it all and you can eat the membrane mush too. Or use it to fertilize the Martian soil."