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Moisture swing carbon capture

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As the world grapples with limiting the amount of carbon dioxide in the atmosphere, there is a growing need to capture the carbon dioxide that is emitted as well as preventing it from being emitted in the first place.  Carbon capture can be accomplished at the source of emissions (such as power plants) or it can be done by taking it out of the atmosphere.  The latter is called “direct air capture”.

It is not at all clear whether direct air capture can be accomplished on a scale that would really make a difference and at an acceptable cost either in dollars or energy expended.  But if it can be done that way, it would be a major tool in combatting climate change.

Direct air capture technology generally makes use of sorbent materials whose capacity to capture carbon dioxide and later release it is a function of temperature.  The process requires significant amounts of energy to release the carbon dioxide that has been captured. 

New research from Northwestern University makes use of the “moisture-swing” technique which uses materials whose ability to capture and release carbon dioxide depends on humidity rather than temperature.  While it takes some amount of energy to humidify the volume of air containing the sorbent material, it is very small compared to temperature-driven systems. 

There are many groups working with moisture-swing technology, but the Northwestern Group has identified a number of new sorbent materials with superior properties.

The fundamental questions of scalability and cost remain, but moisture-swing is a promising approach to direct air capture.  If carbon dioxide can be pulled out of the atmosphere in large volumes, it can be concentrated and stored or converted into useful products.

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Pulling carbon dioxide right out of the air

Photo, posted May 15, 2020, courtesy of James Watt via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Giant Farming Robots | Earth Wise

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Farmers are perpetually engaged in a battle against weeds, which can strangle crops and destroy their yields.  There are basically two ways to fight weeds:  spraying herbicides that are bad for the environment and human health or using human labor to pull the weeds by hand. 

Both choices are increasingly undesirable.  Herbicide resistance is a growing problem facing farms around the world and widespread labor shortages in the agricultural sector are making it increasingly difficult to use human resources to combat weeds.

A startup company called FarmWise founded by an MIT engineering alumnus is providing a third option for farmers.  The company has developed giant autonomous weeding robots that use artificial intelligence to cut out weeds without damaging crops.

The company’s first product is called the Titan.  It looks like a large tractor without a driver’s seat.  It uses machine vision to distinguish weeds from crop plants like leafy greens, cauliflower, artichokes, and tomatoes.  It snips off the weeds with sub-inch precision.

Fifteen titan robots have been roaming the fields of 30 large farms in California and Arizona for several years.  A newer robot, called the Vulcan, is more lightweight and is pulled by a tractor.  FarmWise continues to add new crops to its database so that the robots can be used to fight weeds in more and more kinds of farms.

Weed problems are especially acute for farmers of specialty crops, which grow on smaller farms than corn and soybeans, and have unique growing practices, which limit the effectiveness of chemical and technical solutions. 

The overall goal of FarmWise is to turn artificial intelligence into a tool that is as reliable and dependable as GPS is now in the farming industry.

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Titanic robots make farming more sustainable

Photo, posted August 23, 2021, courtesy of Carol VanHook via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The Living Planet Index | Earth Wise

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The World Wildlife Fund and the Zoological Society of London recently published the latest Living Planet Index, which is designed to measure how animal populations are changing through time.  The purpose is to provide an assessment of the health of ecosystems and the state of biodiversity.

The LPI only looks at the population of vertebrates:  birds, mammals, reptiles, amphibians, and fish.  The latest survey looked at how populations have changed between 1970 and 2018.  The results are that populations of these animal groups have declined by an average of 69% over that 48-year period.

This result highlights a very real and very severe crisis of biodiversity loss.  However, it does not mean that there are 2/3 fewer animals today than 48 years ago.  The way the index is calculated is to look at the changes in individual populations of over 5,000 different species.  Then these individual relative declines are averaged to get the result.  

There are shortcomings in the LPI.  For example, individual species that have seen massive population declines will bring the average down.  But even removing the outliers both of a negative and a positive impact does not dramatically change the result.

There is no perfect indicator for biodiversity and ecosystem health.  The Living Planet Index is nonetheless a useful metric and indicates that many species around the world are in decline.  Policymakers and environmental advocates need to make decisions about conservation and protection measures and this index is one tool they can use.

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There’s a frightening new report about wildlife declines. But many are getting the story wrong.

Photo, posted October 12, 2019, courtesy of Visit Rwanda via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

A Better Way To Capture Carbon | Earth Wise

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The goal of carbon capture and storage technology is to remove carbon dioxide from the atmosphere and safely store it for the indefinite future.  There are existing industrial facilities that capture carbon dioxide from concentrated sources – like the emissions from power plants.  The technology currently captures and stores only about a tenth of a percent of global carbon emissions.

Most existing CCS technologies use chemical binders to trap carbon dioxide quickly and efficiently, but they are extraordinarily energy intensive as well as expensive.

Researchers at the University of Colorado Boulder have developed a new tool that could lead to more efficient and cheaper ways to capture carbon dioxide directly out of the air.  The tool predicts how strong the bond will be between carbon dioxide and a candidate molecule for trapping it – that is, a binder.  This new electrochemical diagnostic tool can be used to identify suitable molecular candidates for capturing carbon dioxide from everyday air.

Current carbon capture technologies are very expensive at the scale required to be able to turn the captured CO2 into useful substances, such as carbonates – which are an ingredient in cement – or formaldehyde or methanol, which can be used as fuels.  Making useful materials out of the captured CO2 is an important way to offset the cost of capturing it that merely storing it away does not permit.

The new electrochemical analytical tool developed by the Colorado researchers offers the potential for identifying binders that will be more efficient and less expensive, thereby making direct air carbon capture a realistic part of the efforts to address climate change.

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New method could lead to cheaper, more efficient ways to capture carbon

Photo, posted October 25, 2015, courtesy of Frans Berkelaar via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Training Corals To Tolerate Heat | Earth Wise

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When ocean water is too warm, corals expel the algae that lives in their tissues, which causes the coral to turn completely white.  This is called coral bleaching.   When this happens, the coral is not dead.  However, corals are dependent upon the symbiotic relationship with algae and if conditions don’t improve, they don’t let the algae back in and the corals will die.

According to the National Oceanic and Atmospheric Administration, between 2014 and 2017, around 75% of the world’s tropical coral reefs experienced heat stress severe enough to trigger bleaching.  For 30% of the world’s reefs, the heat stress was enough to kill the coral.

According to new research by the University of Miami published in the journal Coral Reefs, corals subjected to a stressful regimen of very warm water in the laboratory came to be more tolerant of high temperatures, offering a potential tool for preserving ailing coral reefs.

In the study, some corals were kept in water at a constant temperature of 82 degrees while others saw water temperatures fluctuating between 82 degrees and 88 degrees.  After 90 days of this treatment, the corals exposed to variable temperatures were able to tolerate high heat for longer periods before bleaching.  This training regime is akin to an athlete preparing for a race.

The findings suggest a possible approach for restoring coral reefs.  Nursery-raised corals that are “trained” to tolerate heat could be planted onto reefs endangered by warming waters.  Reefs populated by corals with boosted stamina to heat stress could have a greater chance of surviving the warming waters of the oceans.

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Some Corals Can Be Conditioned to Tolerate Heat, Study Finds

Photo, posted December 16, 2015, courtesy of Big Cypress National Preserve via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Fighting Zombie Fires | Earth Wise

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Peat fires are a global threat to both economies and the environment.  They generally burn a smaller area than fast-moving forest fires, but they can burn up to ten times more fuel matter per acre, producing far more smoke and far more carbon emissions.  They ignite very easily, are notoriously difficult to put out, all while releasing as much as 100 times more carbon into the atmosphere than flaming fires.  Some smoldering peat megafires are the largest and longest burning fires on Earth and are responsible for as much as 15% of annual global greenhouse gas emissions.

Peat fires are known as “zombie fires” because of their ability to hide and smolder underground and then reemerge as new flames days or weeks after they were supposedly extinguished.

Firefighters use billions of gallons of water to tackle a peat fire.  For example, fighting the 2008 Evans Road peat fire in North Carolina used up 2 billion gallons of water.  When water alone is used to extinguish peat fires, it tends to create large channels in the soil, which diverts water from nearby smoldering hotspots.  This is one reason that it is so difficult to extinguish a peat fire.

Researchers at Imperial College London have combined water with an environmentally friendly fire suppressant – one already used on flaming wildfires – and tested its use on peat fires.  They found that adding the suppressant to water helped them put out peat fires nearly twice as fast as using water alone, while using only a third to half of the usual amount of water.  The suppressant reduces the surface tension of the liquid, making it less likely to create large channels.  Instead, the liquid flows uniformly through the soil.  This could be an important tool in battling peat fires.

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‘Magical’ fire suppressant kills zombie fires 40% faster than water alone

Photo, posted in August, 2011, courtesy of Chris Lowie / USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Transmission Lines And Wildlife Habitat Connectivity | Earth Wise

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Electrical transmission lines and their support towers tend to be a blight on the landscape but are something modern society cannot avoid.  Power transmission networks – with towers every 200 meters or so of line – are in place throughout the world’s developed nations.  Another common feature of developed nations is the fragmentation of animal species caused by human activity breaking up their natural habitats.

It is important for biodiversity conservation for animals to get their environments connected.   It turns out that transmission line infrastructure can provide an important tool for reconnecting wildlife habitats.

In a study conducted in Spain’s Andalusia region, scientists planted native shrubs and seedlings under six towers along power lines running through cereal cropland.  The area of each tower base was 100 square meters.

Compared to four control sites, the researchers measured increased population density and diversity among arthropods and small mammals observed in the four-year study. 

Enhancing connectivity through networks of habitat corridors or stepping-stone patches has become a key concept in conservation biology and landscape ecology.  Renting or buying large parcels of land to connect protected natural areas to one another would be cost prohibitive but planting suitable native shrubs and other flora under existing transmission line networks can provide many of the same benefits.

In general, power companies pay rent to landowners – often farmers or agribusinesses – for the rights to place towers on their land.  Because it is difficult to work the areas under towers with farm equipment, that space is typically unused, which opens the door to low-cost efforts by environmentalists.

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Electrical transmission lines have power to enhance habitat connectivity for wildlife

Photo, posted April 29, 2018, courtesy of Georgi Todorov/digitalnovas.com via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A New Way To Remove CO2 From The Air

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Researchers at MIT have developed a new way of removing carbon dioxide from a stream of air that could be a powerful tool in the battle against climate change.  The new system can pull carbon dioxide out of almost any concentration level of the gas, even including the roughly 400 parts per million level currently found in the atmosphere.

The technique is described in a new paper in the journal Energy and Environmental Science and is based on passing air through a stack of electrochemical plates. The device is essentially a large battery that absorbs carbon dioxide from the air passing over its electrodes as it is being charged up, and then releases the gas as it is being discharged.

To use it, the device would simply alternate between charging and discharging.  Fresh air or some other feed gas would be blown through the system during the charging cycle and then pure, concentrated carbon dioxide would be blown out during discharging.

The specialized battery uses electrodes coated with a compound called polyanthraquinone, which is composited with carbon nanotubes.  These unique electrodes have a binary affinity to carbon dioxide, which means that they either strongly want to capture carbon dioxide or not at all, depending upon whether the device is charging or discharging.

Carbon dioxide is important in many industries such as soft drinks and greenhouse agriculture.  With this device, the stuff could literally be pulled out of the air.  And, of course, in power plants where exhaust gas is dumped into the air, these novel electrochemical cells could be used to prevent the emission of CO2 into the atmosphere.  At the right price, this could be a game changer.

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MIT engineers develop a new way to remove carbon dioxide from air

Photo, posted August 9, 2007, courtesy of William Clifford via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

WAMC Northeast Public Radio

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