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Ozone Recovery Back On Track | Earth Wise

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In 2019, we reported that new emissions of chlorofluorocarbons from eastern Asia were threatening the recovery of the ozone layer in the upper atmosphere.  An unexpected spike in CFC emissions was threatening to undo the progress made under the Montreal Protocol, the international treaty under which every country in the world agreed to phase out the production and use of the ozone-eating chemicals by 2010.

In 2018, a team of scientists reported the spike in emissions of the particular formulation CFC-11 that began in 2013.  By 2019, a second team reported that a significant portion of the emissions could be traced to the Shandong and Hebie provinces in China where there were small factories using the chemical to manufacture foam insulation used in refrigerators and buildings.

Recently, in two papers published in Nature, the same two research teams reported that the global annual emissions of CFC-11 into the atmosphere have declined sharply.   They traced a substantial fraction of the global emission reductions to the very same regions of eastern China where they had previously reported the original spike. 

The results are very encouraging.   If CFC-11 emissions had continued to rise, or even just level off, there would have been real problems with ozone depletion.  Two independent global monitoring networks – one operated by the National Oceanic and Atmospheric Administration and one led by MIT called the Advanced Global Atmospheric Gases Experiment – are doing a good job of detecting threats to the world’s protective ozone layer.  However, the Chinese sources only accounted for about half of the CFC-11 entering the atmosphere.  We still don’t know where the rest of it is coming from.

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Reductions in CFC-11 emissions put ozone recovery back on track

Return of an Old Threat

Photo, posted July 29, 2015, courtesy of NASA Goddard Space Flight Center via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Superstrong Nanofibers | Earth Wise

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Self-assembly is a ubiquitous process in the natural world that leads to the formation of the DNA double helix, the creation of cell membranes, and to many other structures.   Scientists and engineers have been working to design new molecules that assemble themselves in water for the purpose of making nanostructures for biomedical applications such as drug delivery or tissue engineering.  For the most part, the materials created in this way have been chemically unstable and tended to degrade rapidly, especially when the water is removed.

A team at MIT recently published a paper describing a new class of small molecules they have designed that spontaneously assemble into nanoribbons with unprecedented strength and that retain their structure outside of water.

The material is modeled after a cell membrane.  Its outer part is hydrophilic (it likes to be in water) and its inner part is hydrophobic (it tries to avoid water.)  This configuration drives the self-assembly to create a specific nanostructure and by choosing the appropriate chemicals to form the structures, the result was nanoribbons in the form of long threads that could be dried and handled.  The resultant material in many ways resembles Kevlar.   In particular, the threads could hold 200 times their own weight and have extraordinarily high surface areas.  The fibers are stronger than steel and the high surface-to-mass ratio offers promise for miniaturizing technologies for such applications as pulling heavy-metal contaminants out of water and for use in electronic devices and batteries.

The goal of the research is to tune the internal state of matter to create exceptionally strong molecular nanostructures.  The potential for important new applications is considerable and exciting.

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Researchers construct molecular nanofibers that are stronger than steel

Photo, posted June 19, 2007, courtesy of Andrew Hitchcock via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Recycling Tough Plastics | Earth Wise

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Thermoset plastics are ones that contain polymers that cross-link together during the curing process to form an irreversible chemical bond.  This improves the material’s mechanical properties, provides chemical resistance, heat resistance, and structural integrity.  Thermosets include epoxies, polyurethanes, and rubber used for tires.  The big problem with thermosets is that they cannot be easily recycled or broken down after use.

Seventy-five percent of all plastics are thermoplastics, which can be recycled by heating them until they become liquid and can then be remolded.   Thermoset plastics, on the other hand, have such strong chemical bonds that they simply will not melt.  They will typically burn before they can be remolded.

Chemists at MIT have recently developed a way to modify thermoset plastics with a chemical linker that makes them much easier to break down, but still retain the mechanical properties that make them so useful.

In a study published in Nature, the researchers produced a degradable version of a thermoset plastic called pDCPD.  They then broke the plastic down into a powder and were able to use the powder to create more pDCPD.  The paper also proposed a theoretical model that suggests that their approach could be used for a wide range of other plastics and polymers, including rubber.

By adding a chemical called a silyl ether monomer to the liquid precursors that from pDCPD plastic, they found that the resultant material retained its mechanical strength but can be broken down into a soluble powder upon exposure to fluoride ions.

Using this approach with other thermoset materials, the researchers believe it will be possible to create recyclable versions of many of the toughest plastic materials.

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Chemists make tough plastics recyclable

Photo, posted September 1, 2019, courtesy of Luke McKernan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Side Effects Of Geoengineering | Earth Wise

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As the world struggles to reduce the greenhouse gas emissions that are warming the global climate, some researchers are exploring proposals to deliberately engineer climate changes to counteract the warming trend.  One of the most widely discussed approaches is to shade the Earth from a portion of the sun’s heat by injecting the stratosphere with reflective aerosol particles.  Proponents of this idea point out that volcanoes do essentially the same thing, although generally for only a limited amount of time.  Particularly large eruptions, such as the Krakatowa eruption of 1883, wreaked havoc with weather around the world for an entire year.

Schemes to launch reflective aerosols – using planes, balloons, and even blimps – appear to be quite feasible from the standpoint of physically accomplishing them. But this says nothing about the political, ethical, and societal issues involved.  The point is that such an approach could indeed lower global temperatures and thereby potentially offset the warming effects of greenhouse gases.

A study by scientists at MIT looked at what other effects such a solar geoengineering project might have on the climate.  Their modeling concluded that it would significantly change storm tracks in the middle and high latitudes.  These tracks give rise to cyclones, hurricanes, and many more ordinary weather phenomena.

According to the study, the northern hemisphere would have weakened storm tracks, leading to less powerful winter storms, but also stagnant conditions in summer and less wind to clear away air pollution.  In the southern hemisphere, there would be more powerful storm tracks.

Aside from turning the world’s weather patterns inside out, solar geoengineering would do nothing to address the serious issue of ocean acidification caused by increasing carbon dioxide levels.

As many have pointed out, playing the geoengineering game would have many unintended consequences.

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Study: Reflecting sunlight to cool the planet will cause other global changes

Photo courtesy of MIT.

Earth Wise is a production of WAMC Northeast Public Radio.

Solar-Powered Desalination | Earth Wise

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About 1% of the world’s population is dependent on desalinated water to meet daily needs, but water scarcity is a growing problem that experts believe will affect 14% of the world’s population within the next five years.

Desalination takes much more energy than, for example, transporting fresh water over large distances.  In general, desalination costs are much higher than those associated with fresh water, but beyond costs, freshwater is simply not always available.

Researchers at MIT and Shanghai Jiao Tong University in China have developed a completely passive solar-powered desalination system that could provide more than 1.5 gallons of fresh drinking water per hour for every square meter of solar collecting area.   Such a system could provide an efficient, low-cost water source for coastal areas that are off the grid.

The system uses multiple layers of flat solar evaporators and condensers topped with transparent aerogel insulation.  The key to its efficiency is the way it uses each of its multiple stages to desalinate water.  At each stage, heat released by the previous stage is harnessed instead of wasted.  The proof-of-concept device, which was tested on an MIT building rooftop, produced more than twice as much water as the record amount produced by any previous passive solar-powered desalination system.

The researchers plan further experiments aimed at optimizing the choice of materials and configurations and to test the system under realistic conditions.  The hope is to have a technology that can play a role in alleviating water scarcity in parts of the world where electricity is scarce, but seawater and sunlight are abundant.

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Simple, solar-powered water desalination

Photo courtesy of MIT/researchers.

Earth Wise is a production of WAMC Northeast Public Radio.

Emissions-Free Cement

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The production of cement – which is the world’s leading construction material – is a major source of greenhouse gas emissions, accounting for about 8% of global man-made emissions. 

Cement production produces carbon dioxide in two ways:  from a key chemical process and from burning fuel to produce the cement.  The process of making “clinker” – the key constituent of cement – emits the largest amount of CO2.  Raw materials, mainly limestone and clay – are fed into huge kilns and heated to over 2,500 degrees Fahrenheit, requiring lots of fossil fuel.  This calcination process splits the material into calcium oxide and CO2.  The so-called clinker is then mixed with gypsum and limestone to produce cement.

A team of researchers at MIT has come up with a new way of manufacturing cement that greatly reduces the carbon emissions.  The new process makes use of an electrolyzer, where a battery is hooked up to two electrodes in water producing oxygen at one electrode and hydrogen at the other.  The oxygen-evolving electrode produces acid and the hydrogen-evolving electrode produces a base.  In the new process, pulverized limestone is dissolved in the acid at one electrode and calcium hydroxide precipitates out as a solid at the other.

High-purity carbon dioxide is released at the acid electrode, but it can be easily captured for further use such as the production of liquid fuels or even in carbonated beverages and dry ice.  The new approach could eliminate the use of fossil fuels in the heating process, substituting electricity generated from renewable sources. 

The process looks to be scalable and represents a possible approach to greatly reducing one of the perhaps lesser known but nevertheless very significant sources of greenhouse gas emissions.

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New approach suggests path to emissions-free cement

Photo, posted March 26, 2014, courtesy of Michael Coghlan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Other Ways To Cut Vehicle Emissions

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It is pretty clear that the way to drastically reduce vehicle greenhouse gas emissions is to switch as many vehicles as possible to electric power.  As a result, more and more localities are putting in place policies that encourage electrification.

While there is no doubt that electrification is the long-term solution to vehicle emissions, a recent study by MIT and the Ford Motor Company found that, in the short term, there are some places in the US where electric cars are not the best way to reduce emissions.

The study looked at a variety of factors that affect the relative performance of vehicles.  These include the role of low temperatures in reducing battery performance, regional differences in the average number of miles driven annually, and significant differences in the way electricity is generated in different parts of the US.

The results showed that electric vehicles definitely provide the greatest impact in reducing greenhouse gas emissions for most of the country – and particularly on both coasts and in the south – but that there are some places in the upper Midwest where the greatest reduction would be achieved by the use of lightweight gasoline-powered vehicles.

In places like parts of Wisconsin and Michigan, it is mostly rural, there are cold winters, and electricity is predominantly generated by coal-powered plants.  In these places, if gas-powered lightweight cars were to be used, the overall benefit would be greater than that of electric cars.  Unfortunately, there are no high-volume lightweight gasoline-powered mid-sized cars on the market in the US.  Ironically, the only cars of that class using lightweight aluminum construction are Teslas.

While electric cars are truly the long-term solution, the study does demonstrate the benefits of reducing the weight of vehicles.

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What’s the best way to cut vehicle greenhouse-gas emissions?

Photo, posted February 9, 2018, courtesy of Dave Field via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Hundred-Year Floods Becoming One-Year Floods

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By definition, 100-year floods are intense flooding events that historically tend to happen once every 100 years.  Put another way, a 100-year flood has a 1 percent chance of happening in any given year.

According to new research published in the journal Nature Communications, rising global temperatures may turn 100-year floods into annual occurrences in parts of the United States.  The increase in severe coastal flooding events by the end of this century will be a result of rising sea levels and stronger, more frequent tropical storms and hurricanes.

The study, led by researchers at Princeton University and MIT, examined flood risk for 171 counties along the US East Coast and the Gulf of Mexico.  Their analysis concluded that 100-year floods will become annual events in New England.  In the US Southeast and Gulf of Mexico, counties could experience such floods as often as every year up to as seldom as every 30 years.

Previously, most analysis of coastal flooding has looked only at the impact of sea level rise on flood risk.  This new research combined the risk of rising seas with projected changes in coastal storms over the course of this century.  Data from the Gulf of Mexico revealed that the effect of stronger storms is comparable with or even more significant than the effect of sea level change for 40% of the counties studied.  So, neglecting the effects of storm climatology change is likely to significantly underestimate the impact of climate change in many places.

The hope is that more comprehensive flood risk data can be used to create more effective climate resiliency strategies all the way down to the county level.

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100-Year Floods Could Soon Happen Annually in Parts of U.S., Study Finds

Photo, posted August 31, 2017, courtesy of the U.S. Department of Agriculture via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Protecting Vulnerable Shorelines

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Global climate change is having noticeable effects on the environment. For example, glaciers are shrinking.  Plant and animal ranges are shifting and populations decreasing.  And droughts, floods, and wildfires are becoming more frequent and more intense.  According to the Intergovernmental Panel on Climate Change, the evidence indicates that the net damage costs of climate change are likely to be significant and to increase over time. 

Our coastal shorelines, which are already stressed by human activity, pollution, storms, and invasive species, are one of many areas expected to be further threatened by climate change.  Sea level rise and more intense and frequent storms are expected to erode and inundate coastal ecosystems and eliminate wetlands.  Ocean acidification is also projected to disrupt marine environments. 

But according to scientists at the Massachusetts Institute of Technology, seagrasses could play a key role in protecting these vulnerable shorelines from this onslaught.  The MIT research team demonstrated how the ubiquitous marine plants dissipate wave energy and help protect against erosion, which could help mitigate damage from rising seas. 

Using mathematical modelling and experiments, the MIT researchers were able to quantify for the first time how large and dense a continuous meadow of seagrass must be in order to provide adequate damping of waves in a given setting.  They also found that seagrasses offer significant environmental benefits, including preventing beach erosion, protecting seawalls and coastal structures, improving water quality, and sequestering carbon. 

Submerged aquatic vegetation, including seagrasses, provides an ecosystem service exceeding $4 trillion annually.  Hopefully these findings can help provide useful guidance for seagrass restoration efforts.

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Seagrass’ strong potential for curbing erosion

The Effects of Climate Change

Photo, posted October 13, 2010, courtesy of the NOAA Photo Library via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Another Way To Make Solar Cells

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Millions of rooftops now contain solar panels and the majority of the solar cells that make up those panels today are made from silicon.  Silicon solar cells require expensive, multi-step processing conducted at very high temperatures in special clean room facilities.  Despite these complications, the price of solar panels has continued to drop dramatically over the years.

But even as the price of solar cells gets lower and lower, there are still widespread efforts to find even better ways to make them.   One of those ways is with perovskite solar cells.  Perovskites are materials with a characteristic crystal structure and are quite common in nature.  Perovskites can be formed with a wide range of elements and can exhibit a variety of properties.

They were first used to make solar cells about 10 years ago and those first cells were unimpressive in most respects.  However, there has been steady progress since that time.  The potential advantages of perovskite solar cells are that they can be made from low-cost materials and can be manufactured using liquid chemistry, a far cheaper process than what is used to make silicon cells.

Researchers at MIT and several other institutions have recently published the results of research on how to tailor the composition of perovskite solar cells to optimize their properties.   What used to be a trial-and-error process can now become much more engineered and should lead to perovskite solar cells with performance that could exceed that of silicon cells.

Silicon solar panels are a huge, worldwide industry and displacing them in favor of an alternative technology is a tall order.  But if perovskite cells can be optimized for large-scale manufacturability, efficiency and durability, they could definitely give silicon a run for its money.

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Unleashing perovskites’ potential for solar cells

Photo courtesy of Ken Richardson/MIT.

Earth Wise is a production of WAMC Northeast Public Radio.

A See-Through Heat Shield

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It is estimated that air conditioners use about 6% of all the electricity produced in the United States for an annual cost of $29 billion.  With rising temperatures, this expense is only going to get larger.

A significant part of the heat load in buildings arises from heat coming through windows.  It turns out that for every square meter of window, about 500 watts of heat energy can be brought in by sunlight, equivalent to 5 old-fashioned light bulbs.

Researchers at MIT and the University of Hong Kong have developed a heat-rejecting film that can applied to a building’s windows that will reflect 70% of the sun’s incoming heat.  The film is similar to transparent plastic wrap. It remains highly transparent at temperatures below 89 degrees Fahrenheit.  Above that temperature, tiny microparticles embedded in the film shrink and the film becomes more translucent or frosted, still letting in a good amount of light, but rejecting a lot of heat.

There are already so-called smart windows on the market, similar to the electrochromic mirrors in cars that darken to prevent trailing headlights from blinding drivers.  But that technology is not very effective in rejecting heat and it requires power to operate, which means you would have to pay to turn windows opaque.

Tests of the new film demonstrated its ability to reject heat and lower temperatures.  The researchers estimate that if every exterior-facing window in a building were covered in the heat-rejecting film, the building’s air conditioning and energy costs could drop by 10%.  Saving ten percent of tens of billions of dollars is no minor matter.

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See-through film rejects 70 percent of incoming solar heat

Photo courtesy of MIT researchers/MIT. 

Earth Wise is a production of WAMC Northeast Public Radio.

A Battery That Eats Carbon Dioxide

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Fossil fuel-based power plants are increasingly considering the use of carbon capture technologies as a way to reduce emissions.  The biggest challenge to the wide-spread adoption of such technology is its energy cost, which of course equates to economic cost.  Present-day power plants equipped with carbon capture systems can use up to 30% of the electricity they generate just to power the capture, release, and storage of carbon dioxide.

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Diesel Is Dirty

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Three years ago, Volkswagen was found to have illegally cheated federal emissions tests in the US using devious programming of emission control devices.  The subterfuge enabled 11 million passenger cars to meet U.S. emissions standards in the laboratory despite that fact that they actually produced up to 40 times higher emissions than the legal limit in real-world driving.

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Using The Sun To Remove Ice

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Ice buildup can cause all sorts of problems ranging from performance issues to catastrophic failures.  For example, ice buildup can negatively impact things like airplanes, power lines, wind turbines, and the like.  Preventing this ice buildup typically requires energy-intensive heating systems or environmentally-harmful chemical sprays.

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A Robot Fish

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Scientists studying marine life have to figure out ways to get cameras into areas that are too dense or dangerous for people to enter.   This often means sending delicate equipment into places where collisions are both likely and damaging and that equipment is generally tethered to ships or other objects.  To really see what is going on in the underwater world, a better approach is needed.

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Turning Heat Into Electricity

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Many of our technologies produce waste heat.  Internal combustion engines are a prime example, but all our industrial processes, motors, electronics and other machinery turn some (and, in many cases, most) of the energy it takes to run them into heat that just goes into the environment.

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