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Figuring Out Photosynthesis | Earth Wise

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Plants have been harnessing the sun’s energy for hundreds of millions of years. Algae and photosynthetic bacteria have been doing the same for even longer, all with remarkable efficiency and resiliency. 

People have used the energy of the sun in one way or another for millennia, but only recently have we gotten sophisticated about it by using devices like solar panels and sensors.  And we still have a long way to go to get anywhere close to the efficiency of plants. It’s no wonder, then, that scientists have long sought to understand exactly how photosynthesis works.

Scientists from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, and collaborators at Washington University in St. Louis, recently solved a critical part of the age-old mystery of photosynthesis, studying the initial, ultra-fast events through which photosynthetic proteins capture light and use it to initiate a series of electron transfer reactions.  Electrons in plants have two possible pathways to travel but only use one.   

But as a result of their efforts, the scientists are now closer than ever to being able to design electron transfer systems in which they can send an electron down a pathway of their choosing. 

By gaining the ability to harness the flow of energy, it may be possible to incorporate new design principles in non-biological energy systems. This could allow us to greatly improve the efficiency of many solar-powered devices, potentially making them far smaller. Understanding the intricacies of photosynthesis creates a tremendous opportunity to open up completely new disciplines of light-driven biochemical reactions, perhaps even ones that haven’t been envisioned by nature.

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Scientists unravel mystery of photosynthesis

Photo, posted June 14, 2017, courtesy of Alex Holyoake via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Clean Gas From An Artificial Leaf

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Photosynthesis is the process used by plants, algae and certain bacteria to harness energy from sunlight and turn it into chemical energy.  It is often described as the green engine of life on earth.

For quite some time, there have been extensive research efforts around the world in the area of artificial photosynthesis.  The goal is to somehow mimic the behavior of plants in order to generate clean-burning fuels using nothing more than sunlight and the carbon dioxide in the air.

Researchers at the University of Cambridge have recently demonstrated a so-called artificial leaf that can directly produce syngas using sunlight.   Syngas is a fuel gas mixture consisting primarily of hydrogen and carbon monoxide.  Most people haven’t heard of syngas, but many products are created using it.  Being able to produce it sustainably would be a critical step to a far greener chemical and fuel industry.

The artificial leaf contains two light absorbers, similar to the molecules in plants that harvest sunlight, which are combined with a catalyst made from the naturally abundant element cobalt.  When the device is immersed in water, one light absorber uses the catalyst to produce oxygen.  The other carries out the chemical reaction that reduces carbon dioxide and water into carbon monoxide and hydrogen.  The result is the syngas mixture.

It turns out that even a rainy or overcast day provides enough light to drive the process.

Previous artificial leaf devices have mostly just produced hydrogen.  The Cambridge device produces syngas thanks to the novel combination of materials and catalysts it uses.

The researchers are now focused on finding ways to use the technology to produce a sustainable gasoline substitute.

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‘Artificial leaf’ successfully produces clean gas

Photo, posted August 15, 2014, courtesy of Mike Mozart via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Dangerous Cities For Migrating Birds

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Billions of birds migrate north in the spring and south in the fall.  The majority of them fly at night. But as they pass over large cities, the birds can become disoriented by bright artificial light – so-called light pollution, causing them to crash into buildings or windows.

Researchers estimate that 600 million birds die from building collisions in the United States every year.  Now, a new paper from researchers at Cornell University reveals which metropolitan areas are most dangerous for birds and why.

The researchers ranked cities where, as a result of geography and exposure to light pollution, birds are at the greatest risk of becoming attracted to and disoriented by lights and crashing into buildings. They combined light pollution levels with bird density data in order to make their calculations.  Their paper was recently published in the journal Frontiers in Ecology and the Environment.    

Chicago, Houston, and Dallas finished as the three most dangerous cities for migrating birds.  While migration routes vary depending on the season, these three cities still topped all others during both the spring and fall migrations due to their size and geographic positioning in the heart of North America’s most trafficked aerial corridors.  

Audubon’s Lights Out program is one of several national efforts encouraging cities to reduce light pollution, particularly on heavy migration nights, in order to reduce bird mortality. 

But homeowners need to do their part as well since an estimated quarter-million birds die from collisions with residential houses every year.  The suggestion to cities and homeowners alike is the same:  If you don’t need the lights, turn them off. 

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Chicago tops list of most dangerous cities for migrating birds

Photo, posted May 18, 2017, courtesy of Pedro Szekely via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Hydrogen From Water And Sun

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There are research efforts around the world seeking ways to produce hydrogen starting from water and using clean energy.  Finding an economical and scalable way to do this is a key to the so-called hydrogen economy.

A recent study at Argonne National Laboratory makes use of a chemical reaction pathway central to plant biology to create a process that converts water into hydrogen using energy from the sun.

The process combines two membrane-bound protein complexes to perform the conversion of water molecules into hydrogen and oxygen.

The first protein complex, which the researchers call Photosystem I, is a membrane protein that uses energy from light to feed electrons to an inorganic catalyst that makes hydrogen.  But this represents only half of the overall process.

A second protein complex that they call Photosystem II uses energy from light to split water and take electrons from it.  The electrons are then fed to Photosystem I.

The two protein complexes are embedded in thylakoid membranes, which are like those found inside the oxygen-creating chloroplasts in plants.  This membrane is an essential part of pairing the two photosystems.  It supports both of the photosystems and provides a pathway for transferring electrons between the proteins.

The researchers also make use of a synthetic catalyst made from nickel or cobalt that replaces expensive platinum catalysts used in conventional water-splitting schemes.  Combining the light-triggered transport of electrons with the synthetic catalyst results in what the researchers call the “Z-scheme”, an adaptation of photosynthesis to produce hydrogen.

The next step is to incorporate the scheme into a living system which the researchers hope will lead to a practical system for hydrogen production.

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Discovery adapts natural membrane to make hydrogen fuel from water

Photo, posted December 25, 2017, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Liquid Fuel From The Sun

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Most forms of energy we use ultimately come from the sun in one way or another.  Even fossil fuels are the end product of millions of years of plant life that captured solar energy.  The advantage fossil fuels have over direct solar power is that they are, in fact, fuels and therefore can be stored for use when needed.

Scientists in Sweden have now developed a specialized fluid that absorbs some of the sun’s energy, holds it for months or even years, and then releases it when needed.  This solar thermal fuel is like a rechargeable battery for heat rather than electricity.

The special fluid is pumped through transparent tubes where ultraviolet light from the sun excites its molecules into an energized state.  A compound called norbornadiene is converted into quadricyclane. The quadricyclane is a quite stable substance until it is passed over a cobalt-based catalyst, which causes it to turn back into norbornadiene and release copious amounts of heat.

Such a solar thermal fuel could be stored in uninsulated tanks in homes or factories or piped or trucked to where it was needed.  It could then be used for water heaters, dishwashers, or clothes driers.  The room temperature fluid quickly warms to about 183 degrees when passed over the catalyst, plenty warm enough for heating a home or office.  Both the fuel and the catalyst are damaged very little by the reactions, so the process can be recycled many times.

There is much development work needed to optimize shelf life, energy density, good recyclability and other properties before this technology can be commercialized but there are at least 15 groups around the world now studying this intriguing way to get liquid fuel from the sun.

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Scientists transform sunlight into a liquid fuel that can be stored for 18 years

Photo, posted August 17, 2009, courtesy of Hiromichi Torihara via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Bacteria-Powered Solar Cell

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Commercially-available solar panels are composed of solar cells that are most often made from various forms of silicon.  Some panels use thin-film cells made from other semiconductor materials.  Solar cells utilize a property of semiconductors that allows them to convert light energy into electrical energy.

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Carbon And The Dark Ocean

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Sunlight entering the water can travel as much as 3,000 feet into the ocean depths under the right conditions, but ordinarily there is no significant light that penetrates beyond about 650 feet down.  That upper 650 feet is called the euphotic or “sunlight” zone and is home to most familiar marine life.  The “dark ocean”, everything below that depth, makes up 90% of the ocean and remarkably little is known about it.

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Better Zinc-Air Batteries

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Zinc-air batteries are metal-air batteries powered by oxidizing zinc with the oxygen from the air.  They have high energy densities (as much as five times more energy than lithium-ion batteries) and are more environmentally friendly.  Since they are based on abundant zinc, they are potentially much cheaper to produce than the lithium-ion batteries that are used in so many current applications.  But because it is difficult and expensive to produce rechargeable versions of these batteries, they have only found limited use in hearing aids, in some film cameras, and in large form to power navigation instruments, oceanographic experiments and railway signals. 

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A Better Way To Farm Algae

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Microalgae biofuels may provide a viable alternative to fossil fuels.  Algae efficiently use CO2 and can produce biomass very quickly.  Some species can double their mass in as little as 6 hours.   Such single-celled organisms are amenable to high-throughput techniques to evolve new strains, unlike terrestrial biomass sources like corn which can take years to modify.

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Disruptive Light Bulb Technology

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Investment companies like to talk about the disruptive nature of technologies and how they change industries while simultaneously changing our lives.  The growing emphasis on a low-carbon economy has spotlighted a number of technologies as being disruptive in their industry sectors.  One hears this frequently when discussing wind and solar power.  Clearly, these two technologies are changing the face of the utility industry, but at least at present, they still represent a fairly small fraction of the overall business.

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Light Pollution And Early Spring

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We have talked about the impact of light pollution on our ability to see stars and the Milky Way.  We have also discussed its impact on our circadian rhythms.   Recently, scientists in Great Britain published a report on the relationship between light pollution and the timing of when trees produce their buds.  The results of the study suggest that light pollution is causing plants to jump the gun on spring.

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Light Pollution

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The luminous glow of the Milky Way, the galaxy that contains our Solar System, has inspired everything from stories and songs to paintings and poems for centuries.  But now one third of the people on the planet – including 80% of Americans and 60% of Europeans – cannot see the Milky Way at night because of light pollution.  Nighttime light pollution now covers nearly 80% of the globe.   

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Keeping Up With Light Bulbs

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Light bulbs entered people’s lives in the 1880s.  Tungsten filament lightbulbs have been around for about 100 years.  Fluorescent lamps were invented in the 1920s.   These two mainstays dominated most lighting applications for most of the twentieth century.

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