Engineers TV

The new design extends the lifespan of plasma torches from days to years. Photo: Weiwei Zhao/CAS.

A plasma torch is a device that generates a constant flow of plasma – the fourth state of matter. In this state, matter is superheated, and electrons are ripped away from the matter, resulting in an ionised gas.

This gas can be used to cut electrically conductive materials precisely and, therefore, find use in industrial applications. 

Inert gases such as helium, neon, and argon are typically used in plasma torches. Argon mixed with hydrogen is the industry’s most common gas mixture since it is cost-effective and produces the hottest flame and clearest cuts.

How does a plasma torch work?

For the cutting process, the plasma torch forms an arc with the material to be cut. This arc is constricted by a copper nozzle, which has a fine bore.

The fine outlet facilitates an increase in the temperature and velocity of the plasma that emanates from the torch. A plasma torch can reach temperatures of 20,000 degrees Celsius.

The plasma torch’s efflux also helps remove the molten material from the surface. Unlike cutting using oxygen, plasma cutting does not oxidise the metal under process. It, therefore, can be used across a wide spectrum of materials, such as stainless steel, cast iron, aluminium, and non-ferrous alloys. 

In addition to cutting, the approach is also used in other fields, such as low-carbon metallurgy, carbon material preparation, and powder spheroidisation.

In all these applications, the cathode gets depleted and needs to be replenished. This limits the lifespan of the torch while increasing the maintenance costs associated with the equipment.

A simple continuous solution

A research team led by Zhao Peng, a professor at the Hefei Institutes of Physical Science, has found a simple and effective solution to the cathode depletion problem.

The work done under the aegis of the Chinese Academy of Sciences developed a continuous feed system for the cathode that can rapidly replenish old, worn-out ones without interrupting the plasma torch. 

The design is innovative since it helps overcome not just one but multiple obstacles and hurdles associated with using plasma torches.

“The design overcomes five major hurdles, including conductivity, thermal conductivity, sealing, water cooling, and continuous propulsion mechanism,” said LI Jun, Senior Engineer at the Hefei Institute, who was involved in the work. 

Conventional plasma torches typically run for 160 hours. However, with the cathode being continuously fed, this is the least the new plasma torch can do. With their innovation, the team has allowed plasma torches to run for long periods, thereby reducing their downtime and maintenance costs.

“The operation time for plasma torch gas been extended from several days to several years,” according to CAS.

“We have made the world’s longest-lasting plasma torch,” said Prof Zhao in a press release.

This will further improve the efficiency of the process and lead to the development of more industrialised applications of the plasma torch. 

The team behind the world's most advanced methane-monitoring satellite, MethaneSat, are keen on metaphors about cleaning. "About the size of a washing machine," was how environmental scientist Steven Wofsy, described the orbiting object at a press conference ahead of its launch. "Like a push-broom," was his phrase for its capacity to scan the surface of the Earth.

The metaphors are apt. Methane is a particularly dirty greenhouse gas, driving about 30% of the heating the planet has experienced so far. It breaks down in the atmosphere in a mere 12 years, which is much sooner than the centuries taken by CO2 – but it is also about 80 times more powerful over a 20-year time span.

With 60% of global methane emissions coming from human activities, reductions are essential to reaching the world's climate change targets. Equally, if not addressed in a timely way, it could contribute to the passing of dangerous tipping points that lead to rapid and irreversible change around the globe. 

MethaneSat aims to help by providing an independent source of methane monitoring, with a primary focus on methane leaked from oil and gas fields – such as the recent, months-long mega leak in Kazakhstan, which resulted in the release of 127,000 tonnes of the potent gas. By supplementing existing satellite data with even more precise measurements, MethaneSat hopes to provide a near-comprehensive view of global leaks. 

The new MethaneSat aims to detect methane leaked from oil and gas fields around the world. Image: BAE Systems.

Yet the oil and gas industry is also far from the only source of human-caused methane emissions. Agriculture is in fact the largest human source of methane emissions, according to the International Energy Agency, at almost 40%; energy is second at about 37%, and waste third.

Within agriculture, flooded rice fields account for 8% of total human-linked emissions, but belches and manure from livestock are the biggest contributors, with cattle the biggest single offenders. In California, the non-profit coalition Climate Trace found that one single cattle feedlot produced more methane than the state's biggest oil and gas fields.

"If we don't reduce emissions from the food system we won't meet the 1.5C target," says Mario Herrero, a professor of sustainable food systems at Cornell University in New York, who oversaw the methane calculations used in the 2015 Paris Agreement on climate change. "Animal numbers are increasing like crazy, thus methane is increasing. We have to reduce emissions from livestock."

So why is farming's methane taking the back seat in terms of global attention? And what can be done to address this climate-action blind spot?

Monitoring methane

The rationale for focusing on oil and gas activities is that easy wins should be tackled first. "If you're looking to have the biggest impact and make the biggest difference, it's reasonable to focus on oil and gas first," according to Mark Brownstein, a senior vice-president at the Environmental Defense Fund (EDF), the environmental non-profit funding MethaneSat and working in partnership with Google on the project. "There's fewer actors involved than in agriculture," he told reporters. And "there's also the resources there to solve it".

Conversely, agriculture's methane output is more elusive. Aerial remote sensing measurements, such as those taken from aircraft or drones, can capture methane leaks, says Aaron Davitt, principal analyst on remote sensing for the non-profit WattTime, but these technologies can only be deployed in limited regions for limited amounts of time.

Plus, even knowing where to direct remote sensors or satellites to look in the first place can be fraught, adds Sam Schiller, chief executive of Carbon Yield, a firm that helps farmers adapt to climate change. "In most parts of the world, public datasets of livestock facilities are hard to come by."

New satellites

So can more precise satellites help? "In the last five years, satellites have revolutionised our knowledge and understanding of methane emissions for the better," says Antoine Halff, chief analyst and co-founder at Kayrros, an environmental intelligence company.

"Thanks to satellites, we can not only track the large emissions events known as 'super-emitters' with great accuracy, but also measure overall emissions at the basin or country level. Importantly, we can do so in a way that is completely independent and verifiable."

According to Sara Mikaloff-Fletcher, a biogeochemical scientist at National Institute of Water and Atmospheric Research in New Zealand, who is leading MethaneSat's agricultural research, that capacity will only increase in relation to agriculture too.

The new satellite's ability to map methane at a precision of 2ppb (parts per billion) means it will be the first satellite well suited to measuring agricultural emissions, she says. "That number might not mean a lot to your readers, but to me it is the same precision I could get from an instrument on the ground – which is extraordinary." 

The areas MethaneSat is targeting to provide a near-comprehensive view of global methane leaks. Image: MethaneSat.

There are still technical limitations, however. In terms of methane from livestock, small groups of animals pose problems for satellite monitoring, as do farms in places where agriculture is not the primary emissions source.

"I'm also not sure how well we will be able to do sheep, which have smaller emissions than cows," says Mikaloff-Fletcher.  On rice production, meanwhile, satellites cannot see through cloud and nearby wetlands can complicate the data: "It is going to be more challenging," she says.

Exempting agriculture

There are also limitations as a result of policy. A Global Methane Pledge to reduce emissions by at least 30% by 2030, agreed at the Cop26 climate summit in Glasgow, does not include an agriculture target. The agreement only talks about providing farmers with "incentives and partnerships", rather focusing on "all feasible reductions" that the energy industry is tasked with, says Nusa Urbanic, chief executive at Changing Markets Foundation, a campaign organisation.

This reluctance to confront agriculture's emissions problem can be seen at a national level too. The US has a provision that exempts farmers from giving detailed emissions accounts. The EU recently removed a target for agricultural methane from its new 2040 climate goal.

Why the reluctance? According to Halff, while fossil fuel companies are "treated as certified carbon villains", there is a "different aura around farming" where small family farms can sit alongside larger, corporate operations. 

What would help clean up agricultural methane?

There are some positive moves from industry to tackle the problem. A Dairy Methane Action Alliance has seen six of the world's largest dairy companies sign up to reducing their output, says Marcelo Mena, the former environment minister of Chile and now chief executive of the philanthropic Global Methane Hub. The meat sector, however, "has not shown the same level of commitment, and needs to do a lot more".

The key to further progress, Herrero emphasises, is "less but better" production of livestock. Methane from enteric fermentation – especially cow burps – is tricky to solve, but new breeding and feeding techniques could help.

Experiments with red algae in dairy-cow's feed suggest it may achieve reductions in methane, Herrero says. Meanwhile, in Japan, more than 35% of food waste is recycled as pig feed, helping create a more circular food economy.

But human diets may still be the ultimate blind spot holding up methane reduction. Of various measures that the EU could adopt to reach the UN Environment Programme's recommendation of a 40-45% reduction of global methane by 2030, a Changing Markets report found that 50% of consumers would need to eat less meat and dairy.

More information on the extent of agriculture's methane problem could help shift this reluctance, for politicians and consumers alike. And here, once again, more independent monitoring and reporting will be key, says Herrero.

Not just satellites are needed, he says, but methane sensors in individual barns. Plus a global methane observatory to coordinate the data. If contributing to the latter was part of the Paris Agreement and nations' individual pledges on climate action, it could help "ensure continuous monitoring".

Ultimately though, Herrero reflects, "we can't wait to have the perfect monitoring system to act on methane. We need to keep trying things, even though our knowledge is imperfect". 

Author: India Bourke. This article first appeared on BBC Future Planet.

Find out more about xEnergy Elite: CTA link

MIT graduate student Aditya Nandy is the lead author of the paper, which appeared recently in the journal Matter. Other authors are MIT postdoc Shuwen Yue, graduate students Changhwan Oh and Gianmarco Terrones, Chenru Duan PhD ’22, and Yongchul G Chung, an associate professor of chemical and biomolecular engineering at Pusan National University.

Modelling MOFs

Scientists are interested in MOFs because they have a porous structure that makes them well-suited to applications involving gases, such as gas storage, separating similar gases from each other, or converting one gas to another. Recently, scientists have also begun to explore using them to deliver drugs or imaging agents within the body.

The two main components of MOFs are secondary building units – organic molecules that incorporate metal atoms such as zinc or copper – and organic molecules called linkers, which connect the secondary building units. These parts can be combined together in many different ways, just like LEGO building blocks, says Kulik.

“Because there are so many different types of LEGO blocks and ways you can assemble them, it gives rise to a combinatorial explosion of different possible metal organic framework materials,” she says. “You can really control the overall structure of the metal organic framework by picking and choosing how you assemble different components.”

Currently, the most common way to design MOFs is through trial and error. More recently, researchers have begun to try computational approaches to designing these materials. Most such studies have been based on predictions of how well the material will work for a particular application, but they don’t always take into account the stability of the resulting material.

“A really good MOF material for catalysis or for gas storage would have a very open structure, but once you have this open structure, it may be really hard to make sure that that material is also stable under long-term use,” says Kulik.

In a 2021 study, Kulik reported a new model that she created by mining a few thousand papers on MOFs to find data on the temperature at which a given MOF would break down and whether particular MOFs can withstand the conditions needed to remove solvents used to synthesise them. She trained the computer model to predict those two features – known as thermal stability and activation stability – based on the molecules’ structure. 

In the new study, Kulik and her students used that model to identify about 500 MOFs with very high stability. Then, they broke those MOFs down into their most common building blocks – 120 secondary building units and 16 linkers.

By recombining these building blocks using about 750 different types of architectures, including many that are not usually included in such models, the researchers generated about 50,000 new MOF structures.

“One of the things that was unique about our set was that we looked at a lot more diverse crystal symmetries than had ever been looked at before, but [we did so] using these building blocks that had only come from experimentally synthesised highly stable MOFs,” says Kulik.

Ultrastability

The researchers then used their computational models to predict how stable each of these 50,000 structures would be, and identified about 10,000 that they deemed ultrastable, both for thermal stability and activation stability.

They also screened the structures for their 'deliverable capacity' – a measure of a material’s ability to store and release gases. For this analysis, the researchers used methane gas, because capturing methane could be useful for removing it from the atmosphere or converting it to methanol.

They found that the 10,000 ultrastable materials they identified had good deliverable capacities for methane and they were also mechanically stable, as measured by their predicted elastic modulus.

“Designing a MOF requires consideration of many types of stability, but our models enable a near-zero-cost prediction of thermal and activation stability,” says Nandy. “By also understanding the mechanical stability of these materials, we provide a new way to identify promising materials.”

The researchers also identified certain building blocks that tend to produce more stable materials. One of the secondary building units with the best stability was a molecule that contains gadolinium, a rare-earth metal. Another was a cobalt-containing porphyrin – a large organic molecule made of four interconnected rings.

Students in Kulik’s lab are now working on synthesising some of these MOF structures and testing them in the lab for their stability and potential catalytic ability and gas separation ability. The researchers have also made their database of ultrastable materials available for researchers interested in testing them for their own scientific applications.

“The database of MOF structures developed in this work will be highly useful for researchers who are using computational screening to find new MOFs for targeted applications," says Randall Snurr, a professor of chemical and biological engineering at Northwestern University, who was not involved in the study.

“Using machine learning methods they had previously developed, they were able to focus on generating MOF structures likely to have high stability, which is an important consideration for practical applications.”

As countries look to reduce their carbon footprint, a lot of work is being put into developing and building the next generation of power generation tools that can tap into wind, solar, or tidal energies.

While these are noteworthy efforts, addressing the current energy demand with available sources of power is also necessary, and companies like NET Power are working to reduce emissions from these processes.

How does a near-zero emission plant work?

Headquartered in Durham, North Carolina, NET Power invents and develops clean power generation technologies and licenses them. The 'near-zero' emission gas-powered plant is also among its patented technology for clean power generation.

The plant burns natural gas with oxygen to drive a turbine, much like a regular gas plant. However, the combustion of natural gas occurs in a 'supercritical CO2 cycle' following a carbon capture system deployed to trap carbon dioxide from being released into the atmosphere.

The captured carbon is then taken to an underground sequestration facility, making it a 'near-zero' emissions gas plant. NET Power has already developed a proof of concept for the plant at its demonstration facility in La Porte, Texas. 

How near-zero emission gas plant works. NET Power 

The technology has now been licensed to the Zachary Group, which is looking into the front-end engineering design (FEED), expected to be completed by the end of the year. Following this, the engineering firm will take up the responsibility of constructing the power plant near Odessa, Texas. Come 2026, the 300MW power plant is expected to go online as well.

NET Power is looking at a standard modularised utility-scale design approach to keep the costs of construction down, paving the way for the construction of more plants in the future.

While the approach does not completely negate carbon emissions, it does help in delaying their release. Such an approach can help in meeting energy demand using fossil fuels until a time when bottlenecks in renewable energy generation and storage are solved and zero-carbon technologies are ready to power the grid 24/7.