Artificial photosynthesis produces 'green methane'

A new device shows promising results in its ability to convert CO2 and water into useful fuels.

Photo by Maros Misove on Unsplash
  • Artificial photosynthesis devices have long been touted as a way to remove carbon dioxide from the atmosphere and turn it into useful products.
  • New research describes a highly efficient and cheap device that could be used to turn waste carbon dioxide into methane.
  • Natural gas, which mainly consists of methane, is a cleaner fuel than coal and has been characterized as a "bridge fuel" prior to transitioning to renewable energy sources, but not everyone thinks it's a good idea to burn yet more hydrocarbons.

A great many human inventions are inspired by nature. Velcro, for instance, was inspired by the hooked barbs of thistle, sonar was inspired by bats and dolphins, and flight was, of course, inspired by birds. To solve climate change, arguably the world's most pressing challenge, we've once again turned to nature for solutions.

That's why researchers have been working on building devices modeled on plant life's ability to photosynthesize CO2 and water and, using sunlight as an energy source, transform these molecules into carbohydrates and oxygen.

The field of artificial photosynthesis has long looked into how best to implement and adapt this process for our own needs. Now, recent research has uncovered a cheap and efficient means of photosynthesizing useful fuel out of waste CO2 and water.

Scalable and efficient

Artificial photosynthesis

An electron microscope image shows the semiconductor nanowires. These deliver electrons to metal nanoparticles, which turn carbon dioxide and water into methane.

Baowen Zhou

The new method, described in Proceedings of the National Academy of Sciences, uses solar power to produce methane, which can be used as natural gas.

In the context of climate change, many environmentalists are probably groaning over the idea that the production and burning of yet more greenhouse gases should be portrayed as a good thing, but it's important to remember the practical benefits of devices such as this. Attached to the smokestacks of power plants, this artificial photosynthesis device can capture CO2 that would otherwise pollute the atmosphere and transform it into a far more efficient fuel that remains carbon neutral — so-called "green" methane.

Since our current infrastructure already supports the use of hydrocarbons for fuel, implementing tools such as these is an important first step to transitioning towards a more advanced but as-of-yet incomplete renewable energy infrastructure.

"Thirty percent of the energy in the U.S. comes from natural gas," said co-author Zetian Mi in a statement. "If we can generate green methane, it's a big deal."

Most importantly, the device makes use of low-cost and easily manufactured components, meaning that it will be scalable. The fatal flaw of many magic bullet climate change solutions is that they are expensive or difficult to make and implement, preventing them from being used at the scale necessary to combat climate change.

The device itself can be characterized as a solar panel studded with nanoparticles of iron and copper. The copper and iron nanoparticles hang onto molecules of CO2 and H2O by their carbon and hydrogen atoms. Using the sun's energy or an electrical current, the bonds between atoms in the CO2 and H2O are broken down, enabling the water's hydrogen atoms to connect to the carbon dioxide's carbon atom. The end result is one carbon atom bonded with four hydrogen atoms — methane. What's more, the new device does this work far more efficiently than other artificial photosynthesis systems.

"Previous artificial photosynthesis devices often operate at a small fraction of the maximum current density of a silicon device, whereas here we operate at 80 or 90 percent of the theoretical maximum using industry-ready materials and earth abundant catalysts," said Baowen Zhou, a postdoctoral researcher on this project.

Methane is merely one of the more useful products this device can produce; it can also be configured to produce syngas — a fuel consisting of hydrogen, carbon monoxide, and some carbon dioxide — or formic acid, which is used as a preservative in livestock feed.

A bridge too far?

The use of natural gas is on the rise in the U.S., but not everybody sees this as a positive. It's a cleaner fuel than coal, for instance, or diesel. It's been characterized as a bridge fuel that economies can lean on while waiting for the renewable energy sector to mature. Then again, its advantages make it awfully attractive, so much so that critics claim we may pay too much attention to it when we ought to be pivoting to renewable energy in a more focused fashion.

Nearly everyone (except for certain politicians and industry leaders) are on the same page regarding the ultimate fate of the world's energy sources — renewable energy like solar and wind power are going to be the main way we generate power in the future. In the meantime, however, the next-best thing is to implement CO2-scrubbing technology like the artificial photosynthesis device described in this article. Burning natural gas that we've sucked out of the Earth will certainly trash the atmosphere, but converting existing emissions into carbon-neutral fuels is far more practical, regardless of whether natural gas should be considered a bridge fuel or a barrier.

New membrane enables us to harvest 'osmotic' energy from water

You've likely heard of solar energy, but what is osmotic energy?

  • Osmotic power plants harvest energy from the difference in pressure or salinity between salt and freshwater using a semi-permeable membrane.
  • One of the major challenges for this kind of renewable energy, however, has been developing effective and durable membranes.
  • Now, new research demonstrates a durable and effective membrane that could significantly improve osmotic energy collection.
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Rolls-Royce to launch all-electric plane in 2020

The racing plane is hoped to be the fastest electric plane in existence.

  • The electric aircraft industry is just starting to get off the ground, with Siemens breaking the world record for the fastest electric aircraft in 2017.
  • With ACCEL (Accelerating the Electrification of Flight), Rolls-Royce intends to beat that record in the spring of 2020.
  • While these are existing developments, the field of electric aviation has significant challenges to face before we can expect to see electric long-distance passenger planes.
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Green jobs now employ 10x more people than fossil fuel

The green market is growing exponentially. But will the U.S. seize the economic opportunity?

Photo credit: aaaaimages / Getty Images
  • The United States green economy now employs 10 times more people than the fossil fuel industry, providing nearly 9.5 million jobs.
  • In the face of a global climate catastrophe, the green economy is destined to keep rising at an exponential rate over the next decade.
  • Rather than seize this golden economic opportunity, the Trump administration has promised to protect coal and mining jobs while eviscerating funds from green energy.
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Top 6 ways to suck greenhouse gases out of the atmosphere

Researchers evaluated the best and worst ways to remove greenhouse gases from the atmosphere in a recent report.

Photo by Michal Ico on Unsplash
  • A recent report from International Institute for Applied Systems Science evaluated six land-based methods for removing greenhouse gases from the atmosphere.
  • Though they concluded that every technique would be a net positive for the world, some were riskier or costlier than others.
  • Among the safest, cheapest, and overall best approaches were restoring the wetlands and soil carbon sequestration.

In 2016, the Paris Climate Agreement set out the ambitious goal of limiting the rise in global temperature to below 2°C above its preindustrial levels, preferably to 1.5°C. These numbers might seem small, but the amount of energy needed to transform the entire world's average temperature is tremendous, and so too are its effects. If, for instance, the global temperature blasts past that 2°C mark and reaches 4°C, then nearly all of the U.S. will turn into an uninhabitable desert.

But focusing too much on the doom-and-gloom that climate change discussions so often revolve around can be pretty exhausting. So, let's focus instead on possible solutions. If we're to stay below 2°C, we'll need to deploy a multifaceted strategy. Part of that has to be finding ways to remove the greenhouse gases already in our atmosphere.

Recently, researchers at the International Institute for Applied Systems Science looked at the top six land-based methods for sucking greenhouse gases out of the atmosphere to evaluate their costs, their benefits, and which might be our best options going forward. While some of them are more risky or higher cost than others, all of them were found to contribute in some way and to effectively remove greenhouse gases from out of atmosphere.

1. Afforestation and reforestation

Between 1990 and 2015, the world lost 290 million hectares of forest. Restoring these depleted reserves (reforestation) and planting in previously un-forested areas (afforestation) is a fairly simple, common-sense approach to fighting climate change. Trees suck CO2 out of the air and store it in their timber — not only that, but they also contribute to food production, help to regulate freshwater, offer habitats to animals, and provide jobs and recreation among other benefits.

On the other hand, afforestation and reforestation require a lot of water usage and take up land that could otherwise be used for farming. Despite this, the researchers estimated that this strategy could remove between 0.5 to 7 gigatons (that's a billion tons) of CO2 from the atmosphere. To put that into context, one estimate provided by Carbon Brief suggests that human beings have released 1,374 gigatons of CO2 into the atmosphere since the Industrial Revolution. We don't have to get rid of all of this extra CO2, fortunately; just enough to keep warming within acceptable bounds.

2. Wetland restoration

Wetlands

Photo by Eric Muhr on Unsplash

Wetlands might seem like an odd candidate for being one of the most beneficial features of the planet, but they have the potential to scrub another 2.7 gigatons of CO2 from the air. In fact, although wetlands cover 9 percent of the planet, they're estimated to deliver 23 percent of the total value offered by the globe's ecosystems.

For instance, wetlands are the best regulators of water resources out there—they're even sometimes intentionally developed near sewage plants to help filter out pollutants. They also provide habitats for keystone species, can help to produce certain crops (e.g., rice or cranberries), and are extremely resilient to rising sea levels.

Although they tend to release some methane, the amount of CO2 they suck up is well worth it. Regrettably, however, half of the globe's wetlands have been lost, making their restoration a top priority. In addition to being a cheap venture, the researchers also identified virtually no downsides to restoring wetlands.

3. Soil carbon sequestration

Like wetland restoration, soil carbon sequestration — storing carbon in the soil over the long term — presents few downsides. This can take place through a variety of mechanisms, the biggest one being the photosynthesis of plants. But smart crop management, like rotating crops, planting perennial crops (those that don't need to be replanted every year), and so on, can increase how much carbon is stored in the soil. So too can optimizing fertilizer usage, tilling less intensely, improving water management, and many other techniques. Implementing these techniques could result in a reduction of between 2 and 5 gigatons of CO2.

By farming with the conscious goal of sequestering more carbon in the soil, we also gain the benefit of having more useful soil for use in building materials, pharmaceuticals, electronics, and other industrial applications. Plus, it helps to prevent erosion, preserves the landscape, and increases crop yields.

4. Biochar

Biochar

Biochar

Flickr user Oregon Department of Forestry

Biochar is the result of biomass pyrolysis; simply put, it's charcoal. When biomass is burned in a low- or no-oxygen environment, it becomes carbonized, locking that carbon into the material and preventing its transference to the atmosphere. Biochar stores carbon in a long-term, durable fashion. Typically, biochar is distributed in soil, where it can help improve food production and balance the pH of acidic soil. Microorganisms in soils also emit nitrous oxide, another greenhouse gas, but adding small amounts of biochar significantly reduces these emissions, along with other greenhouse gases other than CO2. Plus, producing biochar can also generate electricity.

However, biochar production has to be done carefully. If produced without following clean guidelines, biochar can actually release more greenhouse gases into the atmosphere. But if done correctly, producing biochar could reduce greenhouse gases by up to 2 gigatons of CO2 a year.

5. Terrestrial enhanced weathering

A considerable amount of chemistry is slowly but consistently being conducted beneath our feet. In particular, weathering plays an important role in soil chemistry. As the soil's minerals break down over time, they release nutrients and form secondary minerals, like clay. We can improve this process and encourage desirable soil chemistry by adding crushed silicate rocks rich in calcium and magnesium and low in metal ions like nickel or chromium. Basalt, for instance, would be a good candidate.

Doing so could reduce soil acidity and encourage the transformation of CO2 into bicarbonate ions, or HCO3-. As an added benefit, run-off HCO3- could increase ocean alkalinity, making the ocean more resistant to pH changes. Although it would have some positive effect, the researchers noted that field-scale assessments of this technique's interactions with other approaches — like reforestation — would be necessary to determine exactly how much terrestrial enhanced weathering could contribute to reducing greenhouse gas emissions.

6. Bioenergy carbon capture and storage (BECCS)

Bioenergy

An engineer walks through the Bailey Bioenergy Facility in Washington, D.C.

Katherine Frey/The Washington Post via Getty Images

The use of BECCS is something of a one-two punch; it provides energy, avoiding the need to use fossil fuels, and as feedstocks grow for later use as fuel, they suck CO2 out of the atmosphere. Plants like switchgrass or giant reedgrass make for excellent BECCS feedstocks.

Generally, regular bioenergy is a carbon-zero product, since the fuel sequesters CO2 as it grows and releases CO2 as it's burned for energy. But incorporating carbon capture and storage (CCS) technology in this process results in negative emissions. This beats adding CCS technology to fossil fuel processes, since burning fossil fuels starts off by adding emissions to the atmosphere — existing CCS tech can therefore only reduce fossil fuel emissions, rather than turning them negative as is the case with bioenergy.

If BECCS were implemented at a large scale by the year 2100, it could remove 15 gigatons of CO2 per year. However, doing so would be expensive, and the land taken up to grow bioenergy feedstocks could be used instead to grow food. It would also require a greater use of fertilizers and would require a good amount of water to grow.

With the exception of wetland restoration and soil carbon sequestration, all of these approaches for greenhouse gas removal present some kind of downside that we would need to mitigate. The most challenging approaches would be afforestation/reforestation, BECCS, and biochar production, primarily due to their use of land that could otherwise grow food and their water requirements.

However, the researchers found that all of these methods for greenhouse gas removal would not only reduce greenhouse gases in the atmosphere, but, on balance, they would also make our lives better, either by creating jobs, reducing pollution, contributing food, promoting ecological diversity, or other ancillary benefits. Combating climate change is often presented as a costly venture, but in reality, it's more of an investment. By assessing the costs and benefits of approaches such as these six, we can get a better picture of what our return will be.