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7 Posts authored by: Sam Lemonick

A nutrient-rich clay long used to treat diarrhea might help to solve a problem related to the *ahem* other end of the digestive tract. A new report shows that the mineral attapulgite could be useful as a sustainable slow-release fertilizer, a key ingredient for feeding the world’s growing population.

 

In ACS’ journal Industrial & Engineering Chemistry Research, Boli Noi and colleagues propose using the clay to release plant nutrients at a controlled rate to maximize their effect. They cite studies showing that plants take up less than half of the fertilizers applied to them.

 

This inefficiency is not only expensive, it wastes an increasingly precious resource. The world uses about 150 million tons of fertilizer each year -- enough to fill about 6.5 million semi-trucks. That number is expected to double by 2030 as the world’s population grows. What’s more, the excess fertilizer runs off into rivers, lakes and other waterways and causes pollution problems.

 

Attapulgite would control nutrient release, allowing plants to use the nutrients more efficiently and limiting their environmental impact. Slow-release fertilizers currently in use are imperfect. Some may not release all of their nutrients to the soil for plants to use. Others can make the soil more acidic or leave unwanted, lab-made compounds in the soil. Noi’s team argues that nutrient-rich attapulgite is more environmentally friendly, cheaper and more effective.

 

Before Noi and his team used it as a fertilizer, attapulgite – named for a town in southwest Georgia where the clay is abundant – was a main ingredient in a range of anti-diarrheal medicines, including Kaopectate. Although its U.S. formula changed in 2003, the over-the-counter drug still contains attapulgite in other Canada and other markets. In the digestive tract, it effectively absorbs toxins and acids.

 

They tested fertilizer pellets made from a mixture of attapulgite, humic acid from decayed plant material and guar gum, a thickener used in foods and cosmetics. The humic acid and guar gum coating helped to slow the release of nitrogen and phosphorous nutrients trapped in the clay. The coating also helped to trap water in the soil.

 

The group reports that their fertilizers were easy to make, produced less runoff, improved soil moisture and regulated soil acid and alkalinity. The authors conclude: “All of the results indicate that it may be expected to have wide applications for sustainable development of modern agriculture.”

 

Will smarter fertilizers help solve the looming food crisis brought on by the world’s population growth? Tell us your thoughts in the comments.

 

“Novel Multinutrient Fertilizer and Its Effect on Slow Release, Water Holding, and Soil Amending,”
Industrial & Engineering Chemistry Research

 

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A sustainable new farm fertilizer could include an ingredient found in some diarrhea medicines.
Credit: AbleStock.com/Thinkstock

Many Americans can still remember the high prices, long lines and rationing of the 1973 oil crisis. OPEC’s embargo only lasted five months, but the 1974 National Maximum Speed Law intended to reduce fuel consumption kept speed limits on many interstates at 55 miles per hour (mph) for decades. While the benefits of lower speed limits for cars are still up for debate, researchers say speed limits on cargo ships could help reduce the impact of marine shipping on Earth’s climate and human health.


In a study published in ACS’ journal Environmental Science & Technology, David R. Crocker III and colleagues at the University of California, Riverside, found that 14 mph speed limits on container ships sailing near ports and coastlines would cut air pollution by up to 70 percent.


Their paper explains that while marine shipping is the most efficient way to move goods around the world, it’s also a significant source of air pollutants. The more than 100,000 ships – some of them longer than three football fields – that move 90 percent of the world’s cargo burn low-grade fuels that produce large amounts of air pollutants. Among them are carbon dioxide, a greenhouse gas; nitrogen oxides and sulfur oxides that contribute to acid rain; and particulate matter that can cause respiratory and other health problems.


A ship’s speed is directly proportional to the cube of its fuel consumption, so if a ship revs up its engines to go twice as fast, it burns eight times more fuel. That means that even small reductions in speed can significantly reduce air pollution.


Crocker’s team showed that a 14 mph speed limit could reduce container ships’ emissions of carbon dioxide by about 60 percent and nitrogen oxides by 55 percent, compared to emissions at their normal cruising speeds between 25 and 29 mph. Particulate matter emissions fell by nearly 70 percent.


The group hopes that imposing these speed limits on vessels near ports and coastlines could significantly reduce their pollution and protect the health of people living in those areas.


Do you think speed limits on ships could be an effective way to limit their consequences on human health and climate? Should we think again about lower speed limits for cars and other vehicles?

 

“Greenhouse Gas and Criteria Emission Benefits through Reduction of Vessel Speed at Sea,” Environmental Science & Technology


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Speed limits on container ships near ports and coastlines could cut air pollution by up to 70 percent.
Credit: iStockphoto/Thinkstock

It’s 2012. You can travel almost anywhere in the world in a matter of hours. You’re probably carrying a miniaturized computer in your pocket. But when the next major oil spill happens, like the Deepwater Horizon accident in 2010 that spilled enough oil to fill 300 Olympic-size swimming pools, will we really clean it up with corncobs and straw, as we’ve done for decades?

 

Spill response teams are still using low-tech absorbents like those mentioned above. That could change thanks to a new superabsorbent material that can soak up 45 times its own weight in oil. It’s described in a paper in ACS’ journal Energy & Fuels.

 

Current absorbents, like plant matter, can only hold about 5 times their own weight in oil, and they tend to absorb water at the same time, unlike the new absorbent. After doing the job, the oil-soaked corncobs and straw become industrial waste that is either buried in special landfills or incinerated. That can be expensive, and the process raises additional environmental concerns.

 

Authors T.C. Mike Chung and Xuepei Yuan describe a new polymer absorbent, one pound of which can absorb about 5 gallons of crude oil. The resulting gel is stable enough that it can withstand waves and sun as it floats on the surface, and strong enough to then be picked up and collected. Afterward, a refinery can recover the absorbed oil.

 

The polymer is a network of interlinked carbon chains and rings. Crude oil contains similar shapes packed loosely together. These molecules fill in the empty spaces in the polymer web, swelling it up to 40 times in size.

 

The new technology is inexpensive, too. The authors estimate that it would cost about $2 per pound when it’s being produced on a large scale. If crude oil was selling for $100 barrel, a pound of the absorbent could sop up and deliver $15 in crude oil.

 

Finding a better way to clean up large oil spills is important because of their often disastrous consequences. In addition to killing 11 men working on the rig, the Deepwater Horizon spill killed thousands of animals living in and near the Gulf of Mexico and cost tens of billions of dollars in losses for the regional tourism and fishing industries.

 

“Novel Solution to Oil Spill Recovery: Using Thermodegradable Polyolefin Oil Superabsorbent Polymer (Oil−SAP)” Energy & Fuels

 


The polymer (a) swells as it absorbs oil from water (b). At right (c), it has been lifted from the water with tweezers.
Credit: American Chemical Society

The effects of carbon dioxide (CO2) in Earth’s atmosphere are well documented and well understood: as a greenhouse gas, it traps heat from the Sun and contributes to rising temperatures. But CO2 is also making life less comfortable beneath the waves by contributing to rising ocean acidity, which can impact marine life and fisheries that support a $183 million industry in the U.S. Now new research shows that runoff from farms and discharge from sewers is adding CO2 to waterways by feeding algal blooms.

 

Burning fossil fuels for heat, electricity and transportation is one way CO2 gets into the air and water. In the new Environmental Science & Technology paper, William G. Sunda and Wei-Jun Cai explain that since the Industrial Revolution in the 18th and 19th centuries, the amount of carbon dioxide in the atmosphere has increased 40 percent. The oceans absorb about a third of that, which means that levels of CO2 in the ocean have been rising apace.

 

When CO2 dissolves in water, it reacts with water to form a number of related compounds, including carbonic acid. This makes ocean water more acidic, which can kill shellfish, deplete food stocks for larger predators, force fish populations to migrate and make it harder for corals to grow.

 

Another source of CO2 in the oceans is algae, which range from giant kelp and seaweed to microscopic versions that float with the currents. When there is an influx of nutrients, the latter can explode in number, forming so-called algal blooms. These population booms can form a green, yellow or brown scum on the water’s surface, with hundreds or thousands of algae in each teaspoon of water. Infamous red tides are one example. Fertilizer running off fields and organic matter discharged from sewers enter major waterways and end up in the oceans, where blooms can form.

 

These blooms quickly devour all the available oxygen and can kill off other ocean life, as has happened in the infamous “dead zone” at the mouth of the Mississippi. They also produce large amounts of CO2, contributing to the growing acidification problem.

 

Sunda and Cai took all this into account to build a computer model of how ocean acidification is likely to proceed. Another piece of the puzzle that they added into their model: ocean acidity is also affected by temperature, which is changing as more CO2 enters the atmosphere. Between CO2 from the atmosphere and algal blooms, the authors’ model predicts that the oceans will get increasingly acidic.

 

The effects might be greatest for fisheries in places like the Gulf of Mexico and the Baltic Sea because of the large amount of nutrient input from coastal sources in those areas. The report singles out clams, oysters, scallops and mussels as populations that may be the most heavily impacted.

 

What other effects of ocean acidification concern you?

 

“Eutrophication Induced CO2Acidification of Subsurface Coastal Waters: Interactive Effects of Temperature, Salinity, and Atmospheric PCO2Environmental Science & Technology

 

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Credit: National Oceanic and Atmospheric Administration

Many city dwellers have a special appreciation for a tree-lined street. The trees provide much-needed summertime shade to sidewalks and houses. Chirping birds make their homes in the branches. Dappled green light filters through the trees’ leaves. A new paper reports that properly arranged greenery can also cut air pollution on city streets by up to eight times more than was previously believed.

 

Thomas Pugh and colleagues explain that “urban canyons” formed by city buildings concentrate harmful pollutants. Burning fossil fuels in car engines and power plants produces pollutants — like nitrogen dioxide (NO2) and particulate matter (PM) – which may harm our lungs. The World Health Organization estimates that outdoor air pollution kills 1.3 million people each year. The authors report that levels of these two pollutants routinely reach unsafe levels on city streets and that the situation is only getting worse in many places.

 

Their Environmental Science & Technology paper describes three basic ways to reduce pollutant levels: curbing their emission, increasing their dispersion or getting them out of the air and onto something solid. The first two are tough in a city, where constant traffic is a given and tall buildings and right-angle intersections conspire to trap polluted air.

 

Both NO2 and PM will stick to hard surfaces like concrete and asphalt, but the authors say that plants do a better job of trapping pollutants, pointing to the “stickiness” of plant leaves, the way air moves around them and their large surface areas. That’s the key to their assertion that well-placed plants can reduce street-level concentrations of NO2 by as much as 40 percent and PM by 60 percent. The researchers say that more judicious placement of grasses, shrubs and trees could go much further than previous research suggested in making the air at street level cleaner.

 

The authors suggest that climbing plants like ivy, ground-covering grasses and shrubs and vertical gardens on the sides of buildings — which they liken to “green billboards” — might be the most effective way to combat pollution. They provide a lot of surface area for pollution deposition without blocking air movement.

 

On streets with light traffic, trees can still be effective because pollution is comparatively low. But where cabs, trucks, buses and cars are spewing out a lot of NO2 and PM, they caution against using trees, which can trap polluted air underneath their canopies. The authors even say that plants in urban spaces could make city air cleaner than in the surrounding areas.

 

Greening city streets has side benefits, too; the authors point out that more plants can lower temperatures, dampen loud noises and make a neighborhood more attractive.

 

What creative ways can you think of to bring more plants onto city streets?

 

“Effectiveness of Green Infrastructure for Improvement of Air Quality in Urban Street Canyons,” Environmental Science & Technology

 

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Credit: iStock

With the temperatures we’ve had this summer here in Washington, D.C., it’s hard to think of anything but the heat. I only got as far as cranking up the AC, but researchers in Georgia have come up with a device that can make electricity from waste heat that car engines, computers, power lines or even the sun can produce.

 

 

Even more remarkable, a Greek philosopher’s discovery that he made 2,300 years ago is the basis for the “pyroelectric nanogenerator” that the researchers describe in a paper that appears in Nano Letters.

 

When machines convert fuel into electrical or mechanical energy, some of that energy goes to waste as heat. For instance, when gasoline ignites in the cylinder of a car’s engine, the explosion produces energy that pushes a piston, which drives a crankshaft, which turns the axles and the wheels. But only about 20 percent of the explosion’s energy helps to move the car; much of the remaining energy is wasted heat – that’s why cars need radiators and coolant.

 

Zhong Lin Wang and the other authors of the Nano Letters paper report that the U.S. loses more than 50 percent of the energy that it produces each year—much of it becomes wasted heat.

 

They found a possible solution for that inefficiency in something called the pyroelectric effect, a phenomenon that the Greek philosopher Theophrastus first described in 314 B.C. Theophrastus was a student and successor of Aristotle at his school in Athens, where he studied and wrote about everything from biology to ethics. In “On Stones” he noted that the semi-precious stone tourmaline attracted small bits of straw when heated.

 

It wasn’t until the late 19th century that scientists began to understand why that happened. When someone heats tourmaline or other pyroelectric materials, the arrangement of the atoms within the material’s crystal structure changes. This rearrangement creates an imbalance of electrons, just like the static charge that builds up when you rub a balloon against your hair – and it attracts stray hairs or straw for the same reasons.

 

To ease that imbalance, electrons will flow from one part of the material to another. Moving electrons create an electrical current, one which Wang and his colleagues realized they could harness.

 

 

To do that, they made a sort of forest of nanowires standing on their ends, each about twice as tall as the pits etched into a CD. The researchers made the wires from zinc oxide, a white compound with pyroelectric properties. It’s also used in paints, plastics, electronics, food and maybe most famously as one of the original sunscreens.

 

 

The researchers report that when they heated or cooled the nanogenerator, it produced electricity. It could conceivably take advantage of regular heating and cooling cycles, like when someone powers cars or computers on or off. Wang even suggested the devices could make electricity from daily fluctuations in temperature from day to night.

How would you use a pyroelectric nanogenerator?


“Pyroelectric Nanogenerators for Harvesting Thermoelectric Energy,” Nano Letters.


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Credit: iStock

What should I do with that old bottle of seasickness medication rattling around in a drawer in my bathroom? The expiration date passed long ago, and it’s been at the bottom of the drawer for so long that the label is illegible.


By some estimates, more than 200 million pounds of pharmaceuticals go unused in the U.S. each year, including everything from Tylenol to arthritis medications. Keeping these pills around the house isn’t a good idea, and not only because you’re sick of moving the bottle to find your nail clippers, like I am. Getting leftover drugs out of the medicine cabinet can reduce the risks of abuse and accidental poisoning.


Should I toss the pills in the trash? Flush them down the toilet? Drive to a local pharmacy with a take-back program to have them incinerated with other medical waste? A new study in Environmental Science & Technology says dropping them in the waste bin might be best.


Steven J. Skerlos and his colleagues write in ES&T that the hard part of getting rid of unwanted drugs is finding a good balance between release of APIs (“active pharmaceutical ingredients,” the compounds that make medicines work), which could harm people and animals out in the environment, and non-API releases like air pollution produced by transportation and incineration.


On one end of the spectrum, they found that flushing leftover pills is the best way to reduce non-API releases, because it doesn’t even require a garbage truck to carry the drugs to the landfill. It does, however, produce the most drug-related releases, because many of the compounds in the medicines go through wastewater treatment plants into rivers and lakes.


On the other end of the spectrum, the group says the best way to keep active ingredients out of the environment is incineration, at the cost of more air pollution. However, they cite studies showing participation rates in take-back programs, which incinerate the drugs, are usually less than 50 percent. The group says a national participation rate of 50 percent in a take-back program, considered to be a high level, would reduce releases of drugs by 93 percent. Besides a low participation rate and more air pollution, another downside of take-back programs is the expense of putting these programs into place at a national scale (about $2 billion each year).


An all-trash disposal program on its own would reduce API releases by 88 percent because most of the compounds are absorbed and retained in landfills. It produces more air pollution than flushing, from the garbage trucks that haul our trash, but much less than take-back programs.


The group says since 60 percent of Americans already put their pills in the trash, that’s probably the best option for reducing the numbers of drug compounds that make into the environment while keeping other pollution and costs low.


What do you do with your unwanted medications? Have you ever used a take-back program? Are you comfortable with trashing your meds, even though they might make it into the environment?


“Life Cycle Comparison of Environmental Emissions from Unused Pharmaceutical Disposal Options” Environmental Science & Technology

 

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Credit: iStock