Tag Archives: phosphorous

We’re going to need more fertilizer if we want to feed the world – much more

According to a new study, we have to increase our phosphorus-based fertilizer production 4 times if we want to satisfy global food needs by 2050.

Photo by Lynn Betts.

As human population continues to increase, so do the challenges on global food production. Fertilizers especially are a point of focus, and phosphorous is a key component of many fertilizers. However, like many other nutrients, phosphorous can be depleted, especially when manure is collected and then used to fertilize arable cropland. The phosphorous (in the manure) is basically relocated from grasslands to agricultural lands, creating an imbalance. If grasslands phosphorous is depleted, then the productivity will be severely compromised. Many meat and dairy products depend on this productivity, and this disruption could affect global food production, authors argue.

Martin van Ittersum and colleagues use data collected between the years 1975 and 2005 by the Food and Agriculture Organisation of the United Nations (FAO) in order to build the first global model of phosphorus budgets in grasslands. They found that most grasslands in the world have a negative phosphorous balance – which means they lose more phosphorous than they gain. At some point in the future, the phosphorous reserves will simply become insufficient.

According to their findings, in addition to the fertilizers we’re using on agricultural lands, we’re also going to need fertilizers for grasslands.

So far, the largest negative balance is in Asia, while the only areas with a neutral or positive phosphorous balance are North America and Eastern Europe.

Dust from the Sahara Desert Fertilizes the Amazon’s Forests

The Sahara Desert and the Amazon area have few things in common – one is a dry, barren wasteland, while the other is the most fertile area on Earth. But according to a new NASA study, there may be more than meets the eye when it comes to the two – dust from the Saharan area makes the trans-Atlantic journey, fertilizing the Amazonian rainforest with phosphorus.

The Sahara Desert actually “sends” dust to the Amazon rainforest, via global winds. Image via Wiki Commons.

Sahara is basically an uninterrupted brown band of sand stretching across the entire northern Africa. The Amazon rainforest covers 5,500,000 square kilometres of rainforest in South America, representing over half of the planet’s remaining rainforests, and comprising the largest and most biodiverse environment in the world. But strong winds connect the two areas – the winds sweep across the Sahara, rising dust particles in the air and bringing them all the way to the Amazon, where they help make the area even more fertile with the embedded phosphorous.

A new paper published in Geophysical Research Letters, a journal of the American Geophysical Union, provides the first description of how this happens. Hongbin Yu, associate research scientist at the Earth System Science Interdisciplinary Center (ESSIC) at the University of Maryland and his team estimated how this phosphorous affects the rainforest. In January, he and his team already published a paper which used satellite data to see how much sand reaches the Amazon. Using data collected by a lidar instrument on NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite from 2007 through 2013, the team estimates that roughly 22,000 tons of phosphorus make the trans-Atlantic journey each year – that’s very similar to the quantity of phosphorous lost through flooding and water runoff.

This is very important because nutrients, like the ones found in commercial fertilizers, come in short supply in the Amazon – because they are locked in the plants themselves. While decomposing leaves for example do provide nutrients to the soil, phosphorous is generally washed away by rainfall into streams and rivers. In a way, the Amazon basin acts like a “giant leaky bathtub”.

This is where the dust steps in, to compensate that deficit – and it also has an impact on the climate.

“We know that dust is very important in many ways. It is an essential component of the Earth system. Dust will affect climate and, at the same time, climate change will affect dust,” said Yu in a recent statement.

The lidar instrument aboard the CALIPSO satellite sends out pulses of light that bounce off particles in the atmosphere and back to the satellite. It distinguishes dust from other particles based on optical properties.
Image Credit: NASA Goddard’s Scientific Visualization Studio

The data showed that wind and weather pick up on average 182 million tons of dust each year and carry it past the western edge of the Sahara – that’s the equivalent of almost 700,000 trucks filled with sand. 132 million tons remain in the air, while 27.7 million tons (the equivalent of over 100,000 trucks) reach the Amazon. Most of that is phosphorous. What’s interesting is that 43 million tons of dust travel farther to settle out over the Caribbean Sea, in Central America.

Researchers underline the fact that this dust might have a huge impact on the climate and nutrient cycle of many areas, due to the huge quantities involved. However, we can’t establish long term trends based on only this seven year observation, so we need to pay more attention to this cycle, over a longer period of time.

“We need a record of measurements to understand whether or not there is a fairly robust, fairly consistent pattern to this aerosol transport,” he said.

Even within this period, there was significant variation – there was an 86 percent change between the highest amount of dust transported in 2007 and the lowest in 2011, Yu said. It’s not clear why this happens, nor is it clear what impact the dust has on a larger scale, in terms of affecting the climate. But knowing that the Amazonian forest and the Caribbean is affected by something as remote as the Sahara desert is definitely exciting.

“This is a small world,” Yu said, “and we’re all connected together.”


Sewage Sludge Contains Millions of Dollars in Gold

There are millions of dollars in gold and other metals in the sewage sludge in major cities. A new study has found that in a city with 1 million inhabitats, there’s as much as $13 million worth of valuable metals, including gold and silver.

Image via Water Desalination Plants.

It’s been known for quite a while that sewage sludge contains significant quantities of valuable metals, but this is the first study I could find which quantifies that amount. For every 1 million people, on average, you’ll find over $2.5 million worth of gold and silver, plus other metals worth millions more.

“For a community of 1 million people, metals in biosolids were valued at up to US$13 million annually,” they conclude in a paper published in Environmental Science & Technology. “A model incorporating a parameter to capture the relative potential for economic value from biosolids revealed the identity of the 13 most lucrative elements with a combined value of US $280/ton [907 kg] of sludge.” That equates to about $8 million in a hypothetical city of 1 million people.

Furthermore, these metals are actually costing governments good money; from a point of view, they’re a pollutant. If they reach a high enough quantity, then the sludge can’t be used as a fertilizer and instead has to be deposited as landfill – turning it into a cost, from an asset (60 percent of sludge produced in America ends up feeding its farms).

The amount won’t shake the world markets, but it can be a way for cities to get some extra value. The city of Suwa in Japan is already working on extracting the gold. They installed a treatment plant near a large number of precision equipment manufacturers reportedly collected nearly 2 kilograms of gold in every metric ton of ash left from burning sludge, making it more gold-rich than the ore in many mines.

Image via Discover Magazine.

Still, before we get to excited, it has to be said that there is no practical way of recovering every bit of gold, but still, scientists argue that the extraction of gold and silver from sludge can be quite profitable. Jordan Peccia from Yale University in the US, who was not involved in the study agrees.

“We’re not going to get rid of this sewage sludge. We need to make this push where we stop thinking about it as a liability and instead we think about it as a resource. And anything we can find in sewage sludge that’s valuable, it’s good.”

But gold and silver are not the only things of value from the sludge. A small number of sewage plants are already removing phosphorous and nitrogen, which can be sold as fertilizer. Sweden, which recycles most of its waste is testing the feasibility of making bioplastics from wastewater. A model sewage incinerator that generates electricity and drinking water was just promoted by the Bill & Melinda Gates Foundation, which helped fund its construction.

All in all, there’s big money in sewage sludge – we just have to find a way to get it.

Scientific Reference: Science| DOI: 10.1126/science.aaa6359


New Paint-on, See-through bandage Emits Phosphorescent Glow for Healing Below

Credit: Li/Wellman Center for Photomedicine.

An interdisciplinary  team of researchers has created a paint-on, see-through, “smart” bandage that glows to indicate a wound’s tissue oxygenation concentration. Oxygenation plays a crucial role in healing, so mapping it in severe wounds and burns can help to significantly improve the success of surgeries to restore limbs and physical functions.

“Information about tissue oxygenation is clinically relevant but is often inaccessible due to a lack of accurate or noninvasive measurements,” explained lead author Zongxi Li, an HMS research fellow on Evans’ team.

This bandage doesn’t only enable this in a non-invasive way, but does so three simple, compact and inexpensive components:

  • – a bright sensor molecule with a long phosphorescence lifetime and appropriate dynamic range;
  • – a bandage material compatible with the sensor molecule that conforms to the skin’s surface to form an airtight seal;
  • – an imaging device capable of capturing the oxygen-dependent signals from the bandage with high signal-to-noise ratio.

Furthermore, the bandage is quite easy and painless to take off.

“The bandage comes off easily – the liquid bandage dries into a tacky gel underneath a plastic layer; the entire bandage comes off with simple peeling. We experimented on 20/1000 of an inch skin grafts, which are almost see-through and very fragile, and found that the bandage could be applied and removed without causing any damage”, team leader Conor L. Evans at the Wellman Center for Photomedicine of Massachusetts General Hospital (MGH) and Harvard Medical School (HMS) said on Reddit.

How the smart bandage works

Conor Evans.

The bandage is applied like a viscous liquid which then solidifies in less then a minute. After it has dried, a transparent barrier layer is then applied atop it to protect the film and slow the rate of oxygen exchange between the bandage and room air, making the bandage sensitive to oxygen coming from only inside the skin. Oxygenation is very important in dealing with wounds.

“Oxygen plays an important role in wound healing, as it is essential to biological functions such as cell proliferation, immune responses and collagen synthesis. Poor oxygenation is directly associated with the development of chronic ischemic wounds, which affect more than 6 million people each year in the United States alone at an estimated cost of $25 billion”, the authors write.

The key to the glow is phosphorous – an element which can absorb light wavelengths and then release them, glowing. The more oxygenation, the stronger they glow.

“How brightly our phosphorescent molecules emit light depends on how much oxygen is present,” said Li. “As the concentration of oxygen is reduced, the phosphors glow both longer and more brightly.”

The last element is a camera-based readout device which does two things: triggers the emission of the phosphors inside the bandage and then monitors the phosphorous emission.

“Depending on the camera’s configuration, we can measure either the brightness or color of the emitted light across the bandage or the change in brightness over time,” Li said. “Both of these signals can be used to create an oxygenation map.”

Applications and further development

The applications of such a bandage are pretty straightforward – they could monitor the developments of severe wound and burns, especially in ischemic (restricted blood supply) conditions, postoperative monitoring of skin grafts or flaps, and burn-depth determination. The fact that this can be done cheaply and in a non-invasive way make it all the more betteer.

“The need for a reliable, accurate and easy-to-use method of rapid assessment of blood flow to the skin for patients remains a clinical necessity,” said co-author Samuel Lin, an HMS associate professor of surgery at Beth Israel Deaconess Medical Center. “Plastic surgeons continuously monitor the state of blood flow to the skin, so the liquid-bandage oxygenation sensor is an exciting step toward improving patient care within the realm of vascular blood flow examination of the skin.”

But even though the achievement is remarkable in itself, the team is already working on future developments.

“We’re developing brighter sensor molecules to improve the bandage’s oxygen sensing efficiency,” said Emmanuel Roussakis, another research fellow in Evans’ laboratory and co-author, who is leading the sensor development effort.

They are also working on revealing other parameters aside for oxygenation – such as pH, bacterial level and specific disease markers.

“In the future, our goal for the bandage is to incorporate therapeutic release capabilities that allow for on-demand drug administration at a desired location,” says Evans. “It allows for the visual assessment of the wound bed, so treatment-related wound parameters are readily accessible without the need for bandage removal—preventing unnecessary wound disruption and reducing the chance for bacterial infection.”

It’s also important to note that this bandage has a shelf life of over a year – so it’s quite likely that we’ll be seeing it in practice in the near future.

Journal Reference: Zongxi Li, Emmanuel Roussakis, Pieter G. L. Koolen, Ahmed M. S. Ibrahim, Kuylhee Kim, Lloyd F. Rose, Jesse Wu, Alexander J. Nichols, Yunjung Baek, Reginald Birngruber, Gabriela Apiou-Sbirlea, Robina Matyal, Thomas Huang, Rodney Chan, Samuel J. Lin, and Conor L. Evans. Non-invasive transdermal two-dimensional mapping of cutaneous oxygenation with a rapid-drying liquid bandage. Biomedical Optics Express, Vol. 5, Issue 11, pp. 3748-3764 (2014). http://dx.doi.org/10.1364/BOE.5.003748


Ecosystems still feel the pain of ancient extinctions

The more researchers study ecosystems, the more we learn that an ecosystem behaves, in many ways, just like a living organism: thousands of years after human hunters wiped out big land animals like giant ground sloths, the ecosystems they lived in are still suffering from the effects, much like a body suffers from past trauma.

The giant sloth, imagined in happier days. Image: Jaime Chirinos/SPL

The giant sloth, imagined in happier days. Image: Jaime Chirinos/SPL

Humans wiping out species (directly through hunting or indirectly through habitat destruction) is not really a new thing. Early human hunters have posed a stress on environments for thousands if not tens of thousands of years, because they were so successful and the prey didn’t have enough time to adapt.

Most ecosystems rely on big animals to supply them with nutrients (read: dung fertilizing).

“If you remove the big animals from an ecosystem, you pretty much stop nutrients moving,” says Chris Doughty of the University of Oxford.

In order to understand the impact of this extinction, Doughty and his colleagues studied the distribution of phosphorous – a nutrient that plants need to grow; he analyzed the Amazon basin in South America, an area which was once the home of fantastically large animals, such as elephant-like gomphotheres and giant ground sloths.

Unfortunately for these spectacular animals though, some 12.500 years ago, humans moved to South America, and shortly after this, these animals went extinct due to extensive hunting and climate change. Today, the Amazon basin is home to a huge biodiversity, but there are no more truly big animals – and their extinction still has a massive effect on the distribution of phosphorous throughout the basin.

Using the relationship between animal size and phosphorous distribution, Doughty estimated how much phosphorus South America’s larger extinct animals would have transported 15,000 years ago. His model concluded that megafauna would have spread nutrients 50 times faster than today’s fauna. This happens because big animals carry more food around in their bellies and they also travel more searching for food. It’s just like blood vessels in the body:

When you get rid of big animals, it’s like severing the nutrient arteries.”, says Doughty. He thinks the same thing happened in North America, Europe and Australia, where most big animals have also been wiped out. “The idea that herbivores redistribute nutrients is not new, but the scale of this thinking is much, much bigger,” says Tim Baker at the University of Leeds in the UK.

If his model is correct, than it’s quite safe to assume that the Amazon is still recovering from this drastic event which severely altered the circuit of nutrients. With large herbivores gone from the area, it’s up to the humans to take their role – but we’re doing the complete opposite of what they’re doing.

amazon basin

“These megafauna would disperse nutrients, whereas humans concentrate them,” says Doughty. We spread fertiliser on small plots of productive farmland, and keep large animals like cows fenced rather than letting them roam freely. “There are probably more nutrients because of people, but they are very poorly distributed.”