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Breakthrough In Artificial Photosynthesis Lets Scientists Store The Sun's Energy As Fuel
Plants have a seemingly effortless skill – turning sunlight into energy – and scientists have been working to artificially emulate this photosynthesis process
29 AUGUST 2020
Plants have a seemingly effortless skill – turning sunlight into energy – and scientists have been working to artificially emulate this photosynthesis process. The ultimate benefits for renewable energy could be huge – and a new approach based on 'photosheets' could be the most promising attempt we've seen so far.
The new device takes CO2, water, and sunlight as its ingredients, and then produces oxygen and formic acid that can be stored as fuel. The acid can either be used directly or converted into hydrogen – another potentially clean energy fuel.
Key to the innovation is the photosheet - or photocatalyst sheet - which uses special semiconductor powders that enable electron interactions and oxidation to occur when sunlight hits the sheet in water, with the help of a cobalt-based catalyst.
No additional components are required for the reaction to occur, and it's fully self-powered.
"We were surprised how well it worked in terms of its selectivity – it produced almost no by-products," says chemist Qian Wang, from the University of Cambridge in the UK.
"Sometimes things don't work as well as you expected, but this was a rare case where it actually worked better."
The device in action. (University of Cambridge)
While the prototype photosheet only measures 20 square centimetres (3 square inches), the scientists who invented it say it should be relatively easy to scale up without incurring huge costs.
Ultimately, they think these sheets could be produced in large arrays, similar to those on solar farms. What's more, the resulting formic acid can be stored in a solution, and from there converted into different types of fuel as needed.
It achieves something that isn't always guaranteed in conversion systems like this – a clean and efficient process without any unwanted by-products. Any extra waste produced has to be dealt with, which can negate the positive effects of the initial reaction.
"It's been difficult to achieve artificial photosynthesis with a high degree of selectivity so that you're converting as much of the sunlight as possible into the fuel you want, rather than be left with a lot of waste," says Wang.
A team from the same lab was also responsible for developing an 'artificial leaf' material in 2019. While the new photosheet behaves in a similar way, it's more robust and easier to scale up – and it produces fuel that's more straightforward to store, too (last year's system created syngas).
That doesn't mean the new photosheet is ready to go commercial just yet: The researchers need to make the process a lot more efficient first; they are also experimenting with different catalysts that may be able to produce different solar fuels.
The need for a full transition to clean energy is more urgent than ever, but we're encouraged by how many projects are in the pipeline. However, as is the case with this new process, figuring out the science is just the start of producing a fuel that will work practically.
"Storage of gaseous fuels and separation of by-products can be complicated – we want to get to the point where we can cleanly produce a liquid fuel that can also be easily stored and transported," says chemist Erwin Reisner, from the University of Cambridge.
"We hope this technology will pave the way toward sustainable and practical solar fuel production."
The research has been published in Nature Energy.
Micro-Naps For Plants: Flicking The Lights On And Off Can Save Energy Without Hurting Indoor Agriculture Harvests
Growing crops under artificial light is gaining momentum , particularly in regions where produce prices can be high during seasons when sunlight is sparse
7/22/2019
Author: Kevin M. Folta
(MENAFN - The Conversation) A nighttime arrival at Amsterdam's Schiphol Airport flies you over the bright pink glow of vegetable production greenhouses. Growing crops under artificial light is gaining momentum , particularly in regions where produce prices can be high during seasons when sunlight is sparse.
The Netherlands is just one country that has rapidly adopted controlled-environment agriculture , where high-value specialty crops like herbs, fancy lettuces and tomatoes are produced in year-round illuminated greenhouses.Advocates suggest these completely enclosed buildings – or plant factories– could be a way to repurpose urban space, decrease food miles and provide local produce to city dwellers.
One of the central problems of this process is the high monetary cost of providing artificial light , usually via a combination of red and blue light-emitting diodes.Energy costs sometimes exceed 25% of the operational outlay. How can growers, particularly in the developing world,compete when the sun is free ? Higher energy use also translates to more carbon emissions, rather than the decreased carbon footprint sustainably farmed plants can provide.
I'vestudied how light affects plant growth and development for over 30 years. I recently found myself wondering: Rather than growing plants under a repeating cycle of one day of light and one night of darkness, what if the same daylight was split into pulses lasting only hours, minutes or seconds?
Indoor plants need plenty of artificial light. josefkubes/Shutterstock.com
Short bursts of light and dark
So my colleagues and I designed an experiment . We'd apply the normal amount of light in total, just break it up over different chunks of time.
Of course plants depend on light for photosynthesis, the process that in nature uses the sun's energy to merge carbon dioxide and water into sugars that fuel plant metabolism. Light also directs growth and development through its signals about day and night, and monkeying with that information stream might have disastrous results.
That's because breaking something good into smaller bits sometimes creates new problems. Imagine how happy you'd be to receive a US$100 bill – but not as thrilled with the equivalent 10,000 pennies. We suspected a plant's internal clock wouldn't accept the same luminous currency when broken into smaller denominations.
And that's exactly what we demonstrated in our experiments . Kale, turnip or beet seedlings exposed to cycles of 12 hours of light, 12 hours dark for four days grew normally, accumulating pigments and growing larger. When we decreased the frequency of light-dark cycles to 6 hours, 3 hours, 1 hour or 30 minutes, the plants revolted. We delivered the same amount of light, just applied in different-sized chunks, and the seedlings did not appreciate the treatment.
The same amount of light applied in shorter intervals over the day caused plants to grow more like they were in darkness. We suspect the light pulses conflicted with aplant's internal clock , and the seedlings had no idea what time of day it was. Stems stretched taller in an attempt to find more light, and processes like pigment production were put on hold.
But when we applied light in much, much shorter bursts, something remarkable happened. Plants grown under five-second on/off cycles appeared to be almost identical to those grown under the normal light/dark period. It's almost like the internal clock can't get started properly when sunrise comes every five seconds, so the plants don't seem to mind a day that is a few seconds long.
Just as we prepared to publish, undergraduate collaborator Paul Kusuma found that our discovery was not so novel. We soon realized we'd actually rediscovered something already known for 88 years. Scientists at the U.S. Department of Agriculture saw this same phenomenon in 1931 when they grew plants under light pulses of various durations. Their work in mature plants matches what we observed in seedlings with remarkable similarity.
A 1931 study by Garner and Allard tracked the growth of Yellow Cosmos flowers under light pulses of various durations.
J. Agri. Res. 42: National Agricultural Library, Agricultural Research Service, U.S. Department of Agriculture.,CC BY
Not only was all of this a retread of an old idea, but pulses of light do not save any energy. Five seconds on and off uses the same amount of energy as the lights being on for 12 hours; the lights are still on for half the day.
But what would happen if we extended the dark period? Five seconds on. Six seconds off. Or 10 seconds off. Or 20 seconds off. Maybe 80 seconds off? They didn't try that in 1931.
Building in extra downtime
It turns out that the plants don't mind a little downtime. After applying light for five seconds to activate photosynthesis and biological processes like pigment accumulation, we turned the light off for 10, or sometimes 20 seconds. Under these extended dark periods, the seedlings grew just as well as they had when the light and dark periods were equal. If this could be done on the scale of an indoor farm, it might translate to a significant energy savings, at least 30% and maybe more.
Recent yet-to-be published work in our lab has shown that the same concept works in leaf lettuces; they also don't mind an extended dark time between pulses. In some cases, the lettuces are green instead of purple and have larger leaves. That means a grower can produce a diversity of products, and with higher marketable product weight, by turning the lights off.
One variety of lettuce grew purple when given a 10-second dark period. They look similar to those grown with a five-second dark period, yet use 33% less energy. Extending the dark period to 20 seconds yielded green plants with more biomass.
J. Feng, K. Folta
Learning that plants can be grown under bursts of light rather than continuous illumination provides a way to potentially trim the expensive energy budget of indoor agriculture. More fresh vegetables could be grown with less energy, making the process more sustainable. My colleagues and I think this innovation could ultimately help drive new business and feed more people – and do so with less environmental impact.
Hacking Photosynthesis
Artificial photosynthesis: can we harness the energy of the sun as well as plants?
13 January, 2019
We will all be dead without the Sun. That we all know. But even if the sun shone 24 hours a day, we will all be dead without plants. Really. Plants keep the world going. We eat a lot of plants – and the animals from which we obtain meat for consumption also consume plants. Furthermore, plants inhale Carbon Dioxide and produce healthier air. The process through which plants get the energy for sustenance (and all other stuff) is called Photosynthesis which means something like ‘producing with light’.
This is fundamental to the life cycle on Earth. But how does photosynthesis work? There’s a big molecule, a protein, inside the leaves of most plants. It is called Rubisco. It is probably the most abundant protein in the world. Rubisco has one job.
It picks up carbon dioxide from the air, and it uses the carbon to make sugar molecules. It gets the energy to do this from the Sun. This is photosynthesis, the process by which plants use sunlight to make food, the foundation of life on Earth.
But Rubisco is not perfect. It has one almost fatal flaw. Unfortunately, Rubisco does not know how to grab only Carbon Dioxide from the air. It also picks up oxygen. But this poses a huge problem for the plant as this leads to the formation of a toxic compound in the plant. It has to do extra work and spend extra energy for detoxification, a process called Photorespiration. This has in fact been called ‘one of the biggest mistakes’ of evolution.
Ripe
Plants have a complicated ‘chemical assembly line’ in their cells to carry out this detoxification, but the process uses up a lot of energy. This means the plant has less energy for actually making food. However, some crops including corn and sugar cane have developed a workaround for Rubisco, making them much more productive. Photorespiration is anti-photosynthesis in the sense that it costs the plant precious energy and resources that it could have invested in photosynthesis to produce more growth and yield.
Many scientists around the world have been trying to ‘hack’ photosynthesis for years, but a team from the University of Illinois has emerged first. There, a research program called Realizing Increased Photosynthetic Efficiency (RIPE), has run for the last five years trying to fix Rubisco’s problem.
They first experimented with tobacco plants, because tobacco is easy to work with. The researchers inserted some new genes into these plants, which shut down the existing detoxification assembly line and set up a new one that is much more efficient.
Photorespiration normally takes a complicated route through three compartments in the plant cell. Scientists engineered alternate pathways to reroute the process, drastically shortening the trip and saving enough resources to boost plant growth.
This resulted in super tobacco plants that grow faster and up to 40 percent bigger than normal tobacco plants. And yes, this was not confined to the laboratory.
These measurements were done both in greenhouses and open-air farm plots. Their research has been published in the prestigious Science magazine.
These scientists now are trying to repeat the process with plants that people rely on for food, such as, tomatoes and soybeans.
They will also be working with cowpea, or black-eyed pea, which is a staple food crop for a lot of farmers in sub-Saharan Africa. One can indeed imagine the effects of more efficient photosynthesis in the poorest regions of the world. The funders of this project include the U.S. Department of Agriculture and the Bill and Melinda Gates Foundation.
It will be many years, though, before any farmer anywhere in the world plant crops with this new version of photosynthesis. Researchers will have to find out whether it means that a food crop actually produces a bigger harvest, while convincing Government regulators and consumers that the crops are safe to grow and eat.
There is an irrational fear regarding Genetically Modified Organism (GMO) food, even though there is no conclusive evidence that they cause disease or deformities. The public however should be assured that the plants with the photosynthesis hack pose no danger to people and animals.
Precision Agriculture
In any case, photosynthesis is just one component of a plant’s needs. Plant growth, in man-made fields or in the wild, depends on the availability of water, nitrogen and phosphorus, not on photosynthetic capacity alone. Farmers generally add water and NPK fertiliser to their crops, though wild plants have to find these on their own. And lest someone think that the sun is essential for photosynthesis for all plants, plenty of plants grow well under artificial light. In fact, indoor agriculture has been proposed as one solution to the impending food crisis in some parts of the world. Moreover, soil-less and artificial light plant growth will be essential for future manned space missions being planned for Mars.
Agriculture is ripe for modernisation in many developing parts of the world where crop yields are still low compared to those of the developed world. Boosting crop yields is essential with the world predicted to have 10 billion people by 2050.
That is three billion extra mouths to feed and a possible 70 percent extra demand for food, but arable land is not getting any bigger. The solution is to improve crop yields and also adopt innovative methods of agriculture such as vertical farming, soil-less farming and indoor farming.
And there is a whole new revolution coming to traditional agriculture too – including self-driving tractors and harvesters, crop-spraying drones, robots, Artificial Intelligence and satellite sensing. There is even a name for agriculture that combines the best elements of technology - precision agriculture.
Internet of Things
The goal is to use automated driving technology, computer vision, telematics, and cloud-based mobile applications to help farmers double or triple their yields—a feat that will be key to keeping up with global food demands as the Earth’s population grows over the next 30 years.
The Internet of Things (IOT) will also help agriculture. Some machines are stuffed with sensors and software that gather data, process it with machine learning, and beam it into mobile apps. The sensors are the eyes of the machine. The software and mobile apps bring the data to life.
The other major challenge is Climate Change, which has the potential to cause a severe disruption to our crop cycles. A Recent analysis that looked into the climate impact on crop yields produced sobering results.
The study’s authors said that for each 1° Celsius rise in global mean temperature there would be a 7.4% decrease in yields of corn, a 6% decrease in yields of wheat, and a 3% yield decrease in rice. It is thus vital to keep Climate Change in check as other advances could be nullified if it reaches unmanageable levels.
Video: Scientists Soup Up Photosynthesis
Oceanographer Penny Chisholm introduces us to an amazing little being: Prochlorococcus, the most abundant photosynthetic species on the planet. A marine microbe that has existed for millions of years, Prochlorococcus wasn't discovered until the mid-1980s -- but its ancient genetic code may hold clues to how we can reduce our dependence on fossil fuels.
Penny Chisholm · Microbial oceanographer, author
Penny Chisholm studies an extremely tiny microorganism that plays an enormous role in ocean ecosystems. Discovered only three decades ago, it has defined her career and inspired her to think differently about life on Earth.