Since the beginning of life on Earth, plants have been naturally converting sunlight into energy. This photosynthesis process that's effortless for them has been anything but for scientists who have been trying to achieve artificial photosynthesis for the last half a century with the goal of creating a carbon-neutral fuel. Such a fuel could be a gamechanger — rather than putting CO2 back into the atmosphere like traditional fuels do, it would take CO2 out of the atmosphere and convert it into usable energy.
If given the option between a carbon-neutral fuel at the gas station and a fuel that produces carbon dioxide in spades -- and if costs and effectiveness were equal --who wouldn't choose the one best for the planet? That's the endgame scientists are after. A consumer switch to clean fuel could have a huge impact on our global CO2 emissions.
Up until this point, the methods used to make liquid fuel from atmospheric CO2 have been expensive, not efficient enough to really get off the ground, and often resulted in unwanted byproducts. But now, a new technology may be the key to unlocking the full potential of artificial photosynthesis. At the very least, it's a step forward and could help make a dent in atmospheric CO2 reduction.
"It's an important breakthrough in artificial photosynthesis," says Qian Wang, a researcher in the Department of Chemistry at Cambridge University and lead author on a recent study published in Nature about an innovation she calls "photosheets."
The latest version of the artificial leaf directly produces liquid fuel, which is easier to transport and use commercially.
These photosheets convert CO2, sunlight, and water into a carbon-neutral liquid fuel called formic acid without the aid of electricity. They're made of semiconductor powders that absorb sunlight. When in the presence of water and CO2, the electrons in the powders become excited and join with the CO2 and protons from the water molecules, reducing the CO2 in the process. The chemical reaction results in the production of formic acid, which can be used directly or converted to hydrogen, another clean energy fuel.
In the past, it's been difficult to reduce CO2 without creating a lot of unwanted byproducts. According to Wang, this new conversion process achieves the reduction and fuel creation with almost no byproducts.
The Cambridge team's new technology is a first and certainly momentous, but they're far from the only team to have produced fuel from CO2 using some form of artificial photosynthesis. More and more scientists are aiming to perfect the method in hopes of producing a truly sustainable, photosynthetic fuel capable of lowering carbon emissions.
Thanks to advancements in nanoscience, which has led to better control of materials, more successes are emerging. A team at the University of Illinois at Urbana-Champaign, for example, used gold nanoparticles as the photocatalysts in their process.
"My group demonstrated that you could actually use gold nanoparticles both as a light absorber and a catalyst in the process of converting carbon dioxide to hydrocarbons such as methane, ethane and propane fuels," says professor Prashant Jain, co-author of the study. Not only are gold nanoparticles great at absorbing light, they don't degrade as quickly as other metals, which makes them more sustainable.
That said, Jain's team, like every other research team working on artificial photosynthesis including the Cambridge team, is grappling with efficiency issues. Jain says that all parts of the process need to be optimized so the reaction can happen as quickly as possible.
"You can't just improve one [aspect], because that can lead to a decrease in performance in some other aspects," Jain explains.
The Cambridge team is currently experimenting with a range of catalysts to improve their device's stability and efficiency. Virgil Andrei, who is working on an artificial leaf design that was developed at Cambridge in 2019, was recently able to improve the performance and selectivity of the device. Now the leaf's solar-to-CO2 energy conversion efficiency is 0.2%, twice its previous efficiency.
The latest version also directly produces liquid fuel, which is easier to transport and use commercially.
In determining a method of fuel production's efficiency, one must consider how sustainable it is at every stage. That involves calculating whenever excess energy is needed to complete a step. According to Jain, in order to use CO2 for fuel production, you have to condense the CO2, which takes energy. And on the fuel production side, once the chemical reaction has created your byproducts, they need to be separated, which also takes energy.
To be truly sustainable, each part of the conversion system also needs to be durable. If parts need to be replaced often, or regularly maintained, that counts against it. Then you have to account for the system's reuse cycle. If you extract CO2 from the environment and convert it into fuel that's then put into a fuel cell, it's going to release CO2 at the other end. In order to create a fully green, carbon-neutral fuel source, that same amount of CO2 needs to be trapped and reintroduced back into the fuel conversion system.
"The cycle continues, and at each point, you will see a loss in efficiency, and depending on how much you [may also] see a loss in yield," says Jain. "And depending on what those efficiencies are at each one of those points will determine whether or not this process can be sustainable."
The science is at least a decade away from offering a competitive sustainable fuel option at scale. Streamlining a process to mimic what plants have perfected over billions of years is no small feat, but an ever-growing community of researchers using rapidly advancing technology is driving progress forward.
Glioblastoma is an aggressive and deadly brain cancer, causing more than 10,000 deaths in the US per year. In the last 30 years there has only been limited improvement in the survival rate despite advances in radiation therapy and chemotherapy. Today the typical survival rate is just 14 months and that extra time is spent suffering from the adverse and often brutal effects of radiation and chemotherapy.
Scientists are trying to design more effective treatments for glioblastoma with fewer side effects. Now, a team at the Department of Neurosurgery at Houston Methodist Hospital has created a magnetic helmet-based treatment called oncomagnetic therapy: a promising non-invasive treatment for shrinking cancerous tumors. In the first patient tried, the device was able to reduce the tumor of a glioblastoma patient by 31%. The researchers caution, however, that much more research is needed to determine its safety and effectiveness.
How It Works
“The whole idea originally came from a conversation I had with General Norman Schwarzkopf, a supposedly brilliant military strategist,” says Dr David Baskin, professor of neurosurgery and leader of the effort at Houston Methodist. “I asked him what is the secret to your success and he said, ‘Energy. Take out the power grid and the enemy can't communicate.’ So I thought about what supplies [energy to] cancer, especially brain cancer.”
Baskin came up with the idea of targeting the mitochondria, which process and produce energy for cancer cells.
This is the most exciting thing in glioblastoma treatment I've seen since I've been a neurosurgeon but it is very preliminary.”
The magnetic helmet creates a powerful oscillating magnetic field. At a set range of frequencies and timings, it disrupts the flow of electrons in the mitochondria of cancer cells. This leads to a release of certain chemicals called ROS (Reactive Oxygen Species). In normal cells, this excess ROS is much lower, and is neutralized by other chemicals called antioxidants.
However, cancer cells already have more ROS: they grow rapidly and uncontrollably so their mitochondria need to produce more energy which in turn generates more ROS. By using the powerful magnetic field, levels of ROS get so high that the malignant cells are torn apart.
The biggest challenge was working out the specific range of frequencies and timing parameters they needed to use to kill cancer cells. It took skill, intuition, luck and lots of experiments. The helmet could theoretically be used to treat all types of glioblastoma.
Developing the magnetic helmet was a collaborative process. Dr Santosh Helekar is a neuroscientist at Houston Methodist Research Institute and the director of oncomagnetics (magnetic cancer therapies) at the Peak Center in Houston Methodist Hospital. His previous invention with colleagues gave the team a starting point to build on. “About 7 years back I developed a portable brain magnetic stimulation device to conduct brain research,” Helekar says. “We [then] conducted a pilot clinical trial in stroke patients. The results were promising.”
Helekar presented his findings to neurosurgeons including Baskin. They decided to collaborate. With a team of scientists behind them, they modified the device to kill cancer cells.
The magnetic helmet studied for treatment of glioblastoma
Dr. David Baskin
After success in the lab, the team got FDA approval to conduct a compassionate trial in a 53-year-old man with end-stage glioblastoma. He had tried every other treatment available. But within 30 days of using the magnetic helmet his tumor shrank by 31%.
Sadly, 36 days into the treatment, the patient had an unrelated head injury due to a fall. The treatment was paused and he later died of the injury. Autopsy results of his brain highlighted the dramatic reduction in tumor cells.
Baskin says, “This is the most exciting thing in glioblastoma treatment I've seen since I've been a neurosurgeon but it is very preliminary.”
The helmet is part of a growing number of non-invasive cancer treatments. One device that is currently being used by glioblastoma patients is Optune. It uses electric fields called tumor treating fields to slow down cell division and has been through a successful phase 3 clinical trial.
The magnetic helmet has the promise to be another useful non-invasive treatment according to Professor Gabriel Zada, a neurosurgeon and director of the USC Brain Tumor Center. “We're learning that various electromagnetic fields and tumor treating fields appear to play a role in glioblastoma. So there is some precedent for this though the tumor treating fields work a little differently. I think there is major potential for it to be effective but of course it will require some trials.”
Professor Jonathan Sherman, a neurosurgeon and director of neuro-oncology at West Virginia University, reiterates the need for further testing. “It sounds interesting but it’s too early to tell what kind of long-term efficacy you get. We do not have enough data. Also if you’re disrupting [the magnetic field] you could negatively impact a patient. You could be affecting the normal conduction of electromagnetic activity in the brain.”
The team is currently extending their research. They are now testing the treatment in two other patients with end-stage glioblastoma. The immediate challenge is getting FDA approval for those at an earlier stage of the disease who are more likely to benefit.
Baskin and the team are designing a clinical trial in the U.S., .U.K. and Germany. After positive results in cell cultures, they’re in negotiations to collaborate with other researchers in using the technology for lung and breast cancer. With breast cancer, the soft tissue is easier to access so a magnetic device could be worn over the breast.
“My hope is to develop a treatment to treat and hopefully cure glioblastoma without radiation or chemotherapy,” Baskin says. “We're onto a strategy that could make a huge difference for patients with this disease and probably for patients with many other forms of cancer.”
Astronauts at the International Space Station today depend on pre-packaged, freeze-dried food, plus some fresh produce thanks to regular resupply missions. This supply chain, however, will not be available on trips further out, such as the moon or Mars. So what are astronauts on long missions going to eat?
Going by the options available now, says Christel Paille, an engineer at the European Space Agency, a lunar expedition is likely to have only dehydrated foods. “So no more fresh product, and a limited amount of already hydrated product in cans.”
For the Mars mission, the situation is a bit more complex, she says. Prepackaged food could still constitute most of their food, “but combined with [on site] production of certain food products…to get them fresh.” A Mars mission isn’t right around the corner, but scientists are currently working on solutions for how to feed those astronauts. A number of boundary-pushing efforts are now underway.
The logistics of growing plants in space, of course, are very different from Earth. There is no gravity, sunlight, or atmosphere. High levels of ionizing radiation stunt plant growth. Plus, plants take up a lot of space, something that is, ironically, at a premium up there. These and special nutritional requirements of spacefarers have given scientists some specific and challenging problems.
To study fresh food production systems, NASA runs the Vegetable Production System (Veggie) on the ISS. Deployed in 2014, Veggie has been growing salad-type plants on “plant pillows” filled with growth media, including a special clay and controlled-release fertilizer, and a passive wicking watering system. They have had some success growing leafy greens and even flowers.
"Ideally, we would like a system which has zero waste and, therefore, needs zero input, zero additional resources."
A larger farming facility run by NASA on the ISS is the Advanced Plant Habitat to study how plants grow in space. This fully-automated, closed-loop system has an environmentally controlled growth chamber and is equipped with sensors that relay real-time information about temperature, oxygen content, and moisture levels back to the ground team at Kennedy Space Center in Florida. In December 2020, the ISS crew feasted on radishes grown in the APH.
“But salad doesn’t give you any calories,” says Erik Seedhouse, a researcher at the Applied Aviation Sciences Department at Embry-Riddle Aeronautical University in Florida. “It gives you some minerals, but it doesn’t give you a lot of carbohydrates.” Seedhouse also noted in his 2020 book Life Support Systems for Humans in Space: “Integrating the growing of plants into a life support system is a fiendishly difficult enterprise.” As a case point, he referred to the ESA’s Micro-Ecological Life Support System Alternative (MELiSSA) program that has been running since 1989 to integrate growing of plants in a closed life support system such as a spacecraft.
Paille, one of the scientists running MELiSSA, says that the system aims to recycle the metabolic waste produced by crew members back into the metabolic resources required by them: “The aim is…to come [up with] a closed, sustainable system which does not [need] any logistics resupply.” MELiSSA uses microorganisms to process human excretions in order to harvest carbon dioxide and nitrate to grow plants. “Ideally, we would like a system which has zero waste and, therefore, needs zero input, zero additional resources,” Paille adds.
Microorganisms play a big role as “fuel” in food production in extreme places, including in space. Last year, researchers discovered Methylobacterium strains on the ISS, including some never-seen-before species. Kasthuri Venkateswaran of NASA’s Jet Propulsion Laboratory, one of the researchers involved in the study, says, “[The] isolation of novel microbes that help to promote the plant growth under stressful conditions is very essential… Certain bacteria can decompose complex matter into a simple nutrient [that] the plants can absorb.” These microbes, which have already adapted to space conditions—such as the absence of gravity and increased radiation—boost various plant growth processes and help withstand the harsh physical environment.
MELiSSA, says Paille, has demonstrated that it is possible to grow plants in space. “This is important information because…we didn’t know whether the space environment was affecting the biological cycle of the plant…[and of] cyanobacteria.” With the scientific and engineering aspects of a closed, self-sustaining life support system becoming clearer, she says, the next stage is to find out if it works in space. They plan to run tests recycling human urine into useful components, including those that promote plant growth.
The MELiSSA pilot plant uses rats currently, and needs to be translated for human subjects for further studies. “Demonstrating the process and well-being of a rat in terms of providing water, sufficient oxygen, and recycling sufficient carbon dioxide, in a non-stressful manner, is one thing,” Paille says, “but then, having a human in the loop [means] you also need to integrate user interfaces from the operational point of view.”
Growing food in space comes with an additional caveat that underscores its high stakes. Barbara Demmig-Adams from the Department of Ecology and Evolutionary Biology at the University of Colorado Boulder explains, “There are conditions that actually will hurt your health more than just living here on earth. And so the need for nutritious food and micronutrients is even greater for an astronaut than for [you and] me.”
Demmig-Adams, who has worked on increasing the nutritional quality of plants for long-duration spaceflight missions, also adds that there is no need to reinvent the wheel. Her work has focused on duckweed, a rather unappealingly named aquatic plant. “It is 100 percent edible, grows very fast, it’s very small, and like some other floating aquatic plants, also produces a lot of protein,” she says. “And here on Earth, studies have shown that the amount of protein you get from the same area of these floating aquatic plants is 20 times higher compared to soybeans.”
Aquatic plants also tend to grow well in microgravity: “Plants that float on water, they don’t respond to gravity, they just hug the water film… They don’t need to know what’s up and what’s down.” On top of that, she adds, “They also produce higher concentrations of really important micronutrients, antioxidants that humans need, especially under space radiation.” In fact, duckweed, when subjected to high amounts of radiation, makes nutrients called carotenoids that are crucial for fighting radiation damage. “We’ve looked at dozens and dozens of plants, and the duckweed makes more of this radiation fighter…than anything I’ve seen before.”
Despite all the scientific advances and promising leads, no one really knows what the conditions so far out in space will be and what new challenges they will bring. As Paille says, “There are known unknowns and unknown unknowns.”
One definite “known” for astronauts is that growing their food is the ideal scenario for space travel in the long term since “[taking] all your food along with you, for best part of two years, that’s a lot of space and a lot of weight,” as Seedhouse says. That said, once they land on Mars, they’d have to think about what to eat all over again. “Then you probably want to start building a greenhouse and growing food there [as well],” he adds.
And that is a whole different challenge altogether.