Made of sunflower pollen, the sponge is hydrophobic — it repels water — thanks to a coat of natural fatty acid on the sponge. In lab experiments, the scientists showed the sponge’s ability to absorb oil contaminants of various densities, such as gasoline and motor oil, at a rate comparable to that of commercial oil absorbents.

Oil spills are difficult to clean up, and result in severe long-lasting damage to the marine ecosystem. Conventional clean-up methods, including using chemical dispersants to break oil down into very small droplets, or absorbing it with expensive, unrecyclable materials, may worsen the damage.

So far, the researchers have engineered sponges that measure 5 cm in diameter. The research team, made up of scientists from NTU Singapore and Sungkyunkwan University in South Korea, believes that these sponges, when scaled up, could be an eco-friendly alternative to tackle marine oil spills.

Professor Cho Nam-Joon from the NTU School of Materials Science and Engineering, who led the study, said: “By finetuning the material properties of pollen, our team successfully developed a sponge that can selectively target oil in contaminated water sources and absorb it. Using a material that is found abundantly in nature also makes the sponge affordable, biodegradable, and eco-friendly.”

This study builds on NTU’s body of work on finding new uses for pollen, known as the diamond of the plant kingdom for its hard exterior, by transforming its tough shell into microgel particles. This soft, gel-like material is then used as a building block for a new category of environmentally sustainable materials.

Last year, Prof Cho, together with NTU President Professor Subra Suresh, led a research team to create a paper-like material from pollen as a greener alternative to paper created from trees. This ‘pollen paper’ also bends and curls in response to changing levels of environmental humidity, a trait that could be useful for soft robots, sensors, and artificial muscles.

Prof Cho, who also holds the Materials Research Society of Singapore Chair in Materials Science and Engineering, added: “Pollen that is not used for plant pollination is often considered biological waste. Through our work, we try to find new uses for this ‘waste’ and turn it into a natural resource that is renewable, affordable, and biodegradable. Pollen is also biocompatible. It does not cause an immunological, allergic or toxic reaction when exposed to body tissues, making it potentially suitable for applications such as wound dressing, prosthetics, and implantable electronics.”

The findings were published in the scientific journal Advanced Functional Materials in March.

Building a sponge from pollen

To form the sponge, the NTU team first transformed the ultra-tough pollen grains from sunflowers into a pliable, gel-like material through a chemical process akin to conventional soap-making.

This process includes removing the sticky oil-based pollen cement that coats the grain’s surface, before incubating the pollen in alkaline conditions for three days. The resulting gel-like material was then freeze-dried.

These processes resulted in the formation of pollen sponges with 3D porous architectures. The sponges were briefly heated to 200°C — a step that makes their form and structure stable after repeatedly absorbing and releasing liquids. Heating also led to a two-fold improvement in the sponge’s resistance to deformation, the scientists found.

To make sure the sponge selectively targets oil and does not absorb water, the scientists coated it with a layer of stearic acid, a type of fatty acid found commonly in animal and vegetable fat. This renders the sponge hydrophobic while maintaining its structural integrity.

The scientists performed oil-absorption tests on the pollen sponge with oils and organic solvents of varying densities, such as gasoline, pump oil, and n-hexane (a chemical found in crude oil).

They found that the sponge had an absorption capacity in the range of 9.7 to over 29.3 g/g.* This is comparable to commercial polypropylene absorbents, which are petroleum derivatives and have an absorption capacity range of 8.1 to 24.6 g/g.

They also tested the sponge for its durability and reusability by repeatedly soaking it in silicone oil, then squeezing the oil out. They found that this process could go on for at least 10 cycles.

In a final proof-of-concept experiment, the team tested the ability of a sponge 1.5cm in diameter and 5mm in height to absorb motor oil from a contaminated water sample. The sponge readily absorbed the motor oil in less than 2 minutes.

“Collectively, these results demonstrate that the pollen sponge can selectively absorb and release oil contaminants and has similar performance levels to commercial oil absorbents while demonstrating compelling properties such as low cost, biocompatibility, and sustainable production,” said Prof Cho, the corresponding author of this study.

Going forward, the researchers plan to scale up the size of pollen sponges to meet industry needs. They are also looking to collaborate with non-governmental organisations and international partners to conduct pilot tests with pollen sponges in real-life environments.

“We hope our innovative pollen materials can one day replace widely-used plastics and help to curb the global issue of plastic pollution,” said Prof Cho.

*g/gis a unit of measurementfor absorption capacity. It refers to how many grams of the contaminant can adhere to per gram of the material that absorbs

Michigan State University community ecologist Phoebe Zarnetske is co-lead of the Climate Intervention Biology Working Group, a team of internationally recognized experts in climate science and ecology that is bringing science to bear on the question and consequences of geoengineering a cooler Earth.

The group’s paper, “Potential ecological impacts of climate intervention by reflecting sunlight to cool Earth,” was published in the most recent issue of Proceedings of the National Academy of Sciences, or PNAS.

“There is a dearth of knowledge about the effects of climate intervention on ecology,” said Zarnetske, associate professor in the Department of Integrative Biology in the MSU College of Natural Science and the paper’s lead author. “As scientists, we need to understand and predict the positive and negative effects it could have on the natural world, identify key knowledge gaps and begin to predict what impacts it may have on terrestrial, marine and freshwater species and ecosystems if it were adopted in the future.”

Conversations in 2018 between Jessica Gurevitch, Distinguished Professor in the Department of Ecology and Evolution at Stony Brook University and working group co-lead, and Alan Robock, Distinguished Professor in the Department of Environmental Sciences at Rutgers University, gave rise to the pioneering group, which is more aware than most that geoengineering Earth’s atmosphere is more than just a science fiction scenario.

The costs and technology needed to reflect the sun’s heat back into space are currently more attainable than other climate intervention ideas like absorbing carbon dioxide from the air. The working group anticipates its discussions and open access paper will encourage an explosion of scientific investigation into how a climate intervention strategy known as solar radiation modification, or SRM, in tandem with greenhouse gas emissions reduction, would affect the natural world.

The feasibility of planetary wide SRM efforts hinge on accurate predictions of its myriad outcomes provided by the well-established computer simulations of the Geoengineering Model Intercomparison Project, or GeoMIP. The PNAS paper lays the foundation for expanding GeoMIP’s scope to include the incredible range and diversity of Earth’s ecosystems.

“While climate models have become quite advanced in predicting climate outcomes of various geoengineering scenarios, we have very little understanding of what the possible risks of these scenarios might be for species and natural systems,” Gurevitch said. “Are the risks for extinction, species community change and the need for organisms to migrate to survive under SRM greater than those of climate change, or does SRM reduce the risks caused by climate change?”

“Most of the GeoMIP models only simulate abiotic variables, but what about all of the living things that are affected by climate and rely on energy from the sun?” Zarnetske said, who is also a faculty member of MSU’s Ecology, Evolution and Behavior Program. “We need to better understand the possible impacts of SRM on everything from soil microorganisms to monarch butterfly migrations to marine systems.”

Zarnetske’s Spatial and Community Ecology Lab, or SpaCE Lab, specializes in predicting how ecological communities respond to climate change across scales from the microcosm to the global, making it uniquely poised to assist the working group in illuminating vital data for future SRM scenarios such as stratospheric aerosol intervention, or SAI, the focus of the paper.

SAI would reduce some of the sun’s incoming radiation by reflecting sunlight back into space, such as what happens after large volcanic eruptions. Theoretically, it would be possible to continuously replenish the cloud and control its thickness and location to achieve a desired target temperature.

But the paper reveals the under researched complexity of cascading relationships between ecosystem function and climate under different SAI scenarios. In fact, the scientists argue that climate change mitigation must continue regardless of whether SRM is adopted, and the question remains whether some or any SRM can be beneficial in addition to decarbonization efforts.

“Although SAI may cool Earth’s surface to a global temperature target, the cooling may be unevenly distributed, affecting many ecosystem functions and biodiversity,” Zarnetske said. “Rainfall and surface ultraviolet radiation would change, and SAI would increase acid rain and would not mitigate ocean acidification.”

In other words, SRM is not a magic bullet for solving climate change. Until the working group’s efforts inspire new research into the effects of different climate intervention scenarios, SRM is more akin to a shot in the dark.

“Participating in this working group has been quite eye-opening for me,” said Peter Groffman, ecosystem ecologist and professor at the Advanced Science Research Center at the CUNY Graduate Center and the Cary Institute of Ecosystem Studies. “I was unaware that modeling climate intervention was so advanced, and I think that climate modelers were unaware of the complexities of the ecological systems being affected. It is a strong reminder of the importance of the need for multidisciplinary analysis of complex problems in environmental science.”

“We hope that this paper will spark a lot more attention to this issue and greater cooperation between scientists in the fields of climate science and ecology,” Gurevitch said.

Against the backdrop of steadily warming temperatures and decreasing total yearly rainfall, rain has been falling in fewer and sometimes larger storms, with longer dry intervals between. Total yearly rainfall has decreased by an average of four inches over the last half century, while the longest dry period in each year increased from 20 to 32 days across the West, explained co-senior author Joel Biederman, a research hydrologist with the ARS Southwest Watershed Research Center in Tucson, Arizona.

“The greatest changes in drought length have taken place in the desert Southwest. The average dry period between storms in the 1970s was about 30 days; now that has grown to 45 days,” Biederman said.

Extreme droughts are also occurring more often in the majority of the West according to historical weather data as there has been an increase in the year-to-year variation of both total rainfall amounts and the duration of dry periods.

Biederman emphasized the growing fluctuations in drought and rain patterns as the most significant change.

“Consistency of rainfall, or the lack of it, is often more important than the total amount of rain when it comes to forage continuing to grow for livestock and wildlife, for dryland farmers to produce crops, and for the mitigation of wildfire risks,” Biederman said.

The rate of increasing variability of rainfall within each year and between years also appears to be accelerating, with greater portions of the West showing longer drought intervals since 2000 compared to previous years.

Notable exceptions to these drought patterns were seen in Washington, Oregon and Idaho and the Northern Plains region of Montana, Wyoming, and the most western parts of North and South Dakota. In these regions, the researchers found some increases in total annual rainfall and decreases in drought intervals. Together, these changes support what models have predicted as a consequence of climate change: a northward shift in the mid-latitude jet stream, which brings moisture from the Pacific Ocean to the western United States, according to Biederman.

A critical aspect of this study is the use of actual rainfall data from 337 weather stations spread across the western United States. Biederman contrasted this with the more common use of “gridded” data, which relies on interpolations between reporting stations and tends to smooth out some of the variability revealed by this work.

“Fangyue Zhang, lead author of the manuscript and a post-doctoral researcher on our team, did the hard, painstaking work of compiling and analyzing data from more than 300 weather stations with complete daily records to reveal these changing drought and rainfall patterns,” Biederman said.

“We were surprised to find widespread changes in precipitation have already occurred across large regions of the West. For regions such as the desert Southwest, where changes clearly indicate a trend towards longer, more erratic droughts, research is urgently needed to help mitigate detrimental impacts on ecosystem carbon uptake, forage availability, wildfire activity, and water availability for people,” said co-senior author William K. Smith, assistant professor, University of Arizona.

A research team led by Colorado State University (CSU) and funded by the Climate and Land Use Alliance found that widespread use of improved ranching management practices in two distinct areas of beef production would lead to substantial emissions reductions. This includes increased efficiency to produce more beef per unit of GHG emitted — growing bigger cows at a faster rate — and enhanced land management strategies to increase soil and plant carbon sequestration on grazed lands.

Globally, cattle produce about 78% of total livestock GHG emissions. Yet, there are many known management solutions that, if adopted broadly, can reduce, but not totally eliminate, the beef industry’s climate change footprint, according to lead author Daniela Cusack, an assistant professor in the Department of Ecosystem Science and Sustainability at CSU.

Overall, the research team found a 46% reduction in net GHG emissions per unit of beef was achieved at sites using carbon sequestration management strategies on grazed lands, including using organic soil amendments and restoring trees and perennial vegetation to areas of degraded forests, woodlands and riverbanks. Additionally, researchers found an overall 8% reduction in net GHGs was achieved at sites using growth efficiency strategies. Net-zero emissions, however, were only achieved in 2% of studies.

“Our analysis shows that we can improve the efficiency and sustainability of beef production, which would significantly reduce the industry’s climate impact,” said Cusack, also a research associate at the Smithsonian Tropical Research Institute in Panama. “But at the same time, we will never reach net-zero emissions without further innovation and strategies beyond land management and increased growth efficiency. There’s a lot of room, globally, for improvement.”

Global analysis

Researchers analyzed 292 comparisons of “improved” versus “conventional” beef production systems across Asia, Australia, Brazil, Canada, Latin America and the U.S. The analysis revealed that Brazilian beef production holds the most potential for emissions reductions.

In the studies analyzed, researchers found a 57% GHG emission reduction through improved management strategies for both carbon sequestration and production efficiency in Brazil. Specific strategies include improved feed quality, better breed selections and enhanced fertilizer management.

The biggest impact was found in integrated field management, including intensive rotational grazing schemes, adding soil compost, reforestation of degraded areas and selectively planting forage plants bred for sequestering carbon in soils.

“My home country of Brazil has more than 52 million hectares of degraded pastureland — larger than the state of California,” said Amanda Cordeiro, co-author and a graduate student at CSU. “If we can aim for a large-scale regeneration of degraded pastures, implementation of silvo-agro-forestry systems and adoption of other diversified local management strategies to cattle production, Brazil can drastically decrease carbon emissions.”

In the U.S., researchers found that carbon sequestration strategies such as integrated field management and intensive rotational grazing reduced beef GHG emissions by more than 100% — or net-zero emissions — in a few grazing systems. But efficiency strategies were not as successful in the U.S. studies, possibly because of a high use of the strategies in the region already.

“Our research shows the important role that ranchers can play in combatting the global climate crisis, while ensuring their livelihoods and way of life,” said Clare Kazanski, co-author and North America region scientist with The Nature Conservancy. “By analyzing management strategies in the U.S. and around the world, our research reinforces that ranchers are in a key position to reduce emissions in beef production through various management strategies tailored to their local conditions.”

Darrell Wood, a northern California rancher, is an example of a producer leading the way on climate-friendly practices. Wood’s family participates in the California Healthy Soils program, which incentivizes practices with a demonstrated climate benefit.

“As a sixth-generation cattle rancher, I see nothing but upside potential from using our cattle as a tool for reducing greenhouse gas emissions,” Wood said. “Taking good care of our grasslands not only benefits climate, but also wildlife and the whole ecosystem that generates clean air and water. It’ll help the next generation continue our business, too.”

Next steps

Although the research shows a significant reduction in the GHG footprints of beef production using improved management strategies, scientists don’t yet know the full potential of shifting to these emission-reducing practices because there are very few data on practice adoption levels around the world.

“Asia, for example, is one of the most rapidly growing beef markets, but there is an imbalance between the amount of research focus on improving beef production and the growing demand for beef,” Cusack said. “We know with the right land management and efficiency strategies in place, it’s possible to have large reductions in emissions across geographic regions, but we need to keep pushing for additional innovations to create a truly transformation shift in the way the global beef system operates to ensure a secure food supply and a healthy environment.”

Additional co-authors on the paper include Alexandra Hedgpeth, Kenyon Chow and Jason Karpman (University of California, Los Angeles); and Rebecca Ryals (University of California, Merced).