Turning waste into climate solutions: Meta-analysis reveals how smarter composting cuts emissions and boosts fertilizer quality

Maximum Academic Press

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By analyzing data from more than a thousand experiments, researchers found that targeted composting control measures can simultaneously reduce greenhouse gas emissions, suppress odors, and improve fertilizer quality. The findings demonstrate that composting—often viewed as environmentally friendly but imperfect—can be optimized to retain nutrients while sharply lowering methane, nitrous oxide, and ammonia emissions.

Rapid growth in global consumption is generating unprecedented amounts of organic waste, projected to reach 3.4 billion tons annually by 2050. Much of this waste still ends up in landfills or open dumps, where decomposition releases methane and nitrous oxide—greenhouse gases far more potent than carbon dioxide. Composting has emerged as a key alternative because it converts waste into nutrient-rich fertilizer while reducing landfill pressure. However, poorly managed composting can release large quantities of greenhouse gases and odorous pollutants while losing valuable nutrients, limiting its environmental benefits. Although many mitigation strategies exist, their overall effectiveness has remained unclear due to fragmented and sometimes contradictory experimental results.

A study (DOI: 10.48130/ebp-0025-0022) published in Environmental and Biogeochemical Processes on 27 January 2026 by Dong Liu’s & Fuqiang Yu’s team, Chinese Academy of Sciences, provides evidence-based strategies to make composting more climate-friendly while improving fertilizer quality and resource recycling.

Using a meta-analytic framework, the researchers synthesized results across composting studies and quantified the overall effects of multiple “air-pollution control” interventions (biological, chemical, physical, and mechanical) on process conditions, fertilizer-quality indicators, and gaseous emissions. They calculated response ratios (RR) for core composting variables (temperature, C/N, TOC), maturity/quality metrics (TN, germination index, humic acid), and emissions (CH₄, N₂O, NH₃, CO₂, H₂S, VOCs), and then conducted moderator analyses to test how feedstock type, bulking agents, treatment types (e.g., pressure aeration, biochar), application rate, and composting duration shaped outcomes. The meta-synthesis showed that control measures broadly improved composting performance: temperature increased (RR = 0.48), consistent with intensified and prolonged thermophilic conditions that support pathogen suppression and faster stabilization; simultaneously, C/N decreased (RR = −0.38) and TOC declined (RR = −1.60), indicating more advanced organic matter decomposition and maturation. These process shifts translated into better fertilizer quality, with TN rising sharply (RR = 0.89), GI improving (RR = 0.73) as phytotoxicity fell, and HA increasing (RR = 0.29), reflecting enhanced humification. In parallel, emissions dropped substantially relative to unmanaged composting, including CH₄ (RR = −1.14), N₂O (RR = −1.76), NH₃ (RR = −1.53), CO₂ (RR = −1.51), H₂S (RR = −0.53), and VOCs (RR = −0.54), underscoring dual climate-and-odor benefits. Moderator results highlighted that context often mattered as much as the intervention: feedstock type significantly influenced CH₄ (e.g., sewage sludge showing strong reductions) and CO₂, while bulking agents generally reduced CH₄ (corn straw notably strong) but were less consistently significant across datasets. Treatment type affected CH₄ most clearly, with pressure aeration producing the largest reductions, whereas biochar stood out for suppressing NH₃ and N₂O. Application rate was most consistently linked to lower N₂O, while composting duration showed weaker or mixed relationships across gases. Overall, the analysis suggests optimized controls can improve maturity and nutrient retention while cutting multiple pollutants, but performance depends strongly on feedstock and operating conditions.

This study demonstrates that climate-smart composting can simultaneously reduce emissions and enhance fertilizer quality through strategic feedstock selection, targeted additives, and optimized aeration. By improving nutrient retention and minimizing environmental impacts, optimized composting supports circular bioeconomy principles, promotes soil health, and offers a scalable pathway for climate mitigation in agriculture and waste management systems.

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References

DOI

10.48130/ebp-0025-0022

Original Source URL

https://doi.org/10.48130/ebp-0025-0022

Funding Information

Partial financial support was received from the Caiyun Postdoctoral Project of Yunnan Province, the Yunnan Revitalization Talent Support Program (awarded to Dong Liu), the 'Strategic Priority Research Program' of the Chinese Academy of Sciences (Grant No. XDA26050302), and the Yunnan Technology Innovation Program (awarded to Fuqiang Yu, Grant No. 202205AD160036).

About Environmental and Biogeochemical Processes

Environmental and Biogeochemical Processes is a multidisciplinary platform for communicating advances in fundamental and applied research on the interactions and processes involving the cycling of elements and compounds between the biological, geological, and chemical components of the environment.

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DOI

10.48130/ebp-0025-0022 

Article Title

Synthesis of air pollution patterns and nutrient composition during organic fertilizer production: a meta-analytical study

 

‘Ghost forests’ could be key to understanding coastal resilience to climate change

American Chemical Society

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Robyn O’Halloran (left) and Ryan Kim (right) collect the rainwater that travels down branches and the trunk of a sweetgum tree to study the rapid changes to coastal forests caused by rising sea levels.

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Credit: Samantha Chittakone

ATLANTA, March 26, 2026 — Rising sea levels are contributing to a phenomenon called “ghost forests,” which are groups of dead and dying standing trees that have been drowned by intruding saltwater. And all along the eastern U.S. where there used to be vibrant green trees, clusters of bare gray trunks appear. Now, researchers say studying how water cycles through ghost forests may hold the key to understanding how coastal forest ecosystems respond to climate change.

Samantha Chittakone, an undergraduate student in environmental engineering at the University of Delaware, will present the research team’s results at the spring meeting of the American Chemical Society (ACS). ACS Spring 2026 is being held March 22-26; it features nearly 11,000 presentations on a range of science topics.

Ghost forests serve as powerful, visible warnings of climate change. Encroaching ocean waters are poisoning salt-intolerant trees, leaving behind eerie skeletal remains. Researchers from the University of Delaware are wading through these surreal landscapes along the mid-Atlantic coastline to better understand the environmental impact of this climate-driven phenomenon.

“Walking through these coastal forests, surrounded by nature, is beautiful,” says Chittakone. “However, it is disheartening to see the healthy trees becoming less prevalent as you approach the shoreline and the effects of rising sea levels become apparent.”

Ghost forests mark hidden shifts in how trees process carbon and nutrients belowground. So, Chittakone, with her supervisors Robyn O’Halloran, Delphis Levia and Yu-Ping Chin, and other colleagues, chose to collect and study sweetgum tree stemflow: the rainwater that travels down branches and the trunk of this common mid-Atlantic coastal tree. They say stemflow is a useful diagnostic tool for understanding rapid changes to forest ecosystems because the water running down the trees acts like a funnel to concentrate water and mobilize nutrients near the roots.

“Stemflow is basically injecting nutrients and really important chemicals into the forest ecosystem so the microbiome there can thrive,” Chin says. He further explains that stemflow color can vary greatly, ranging from intense dark brown, like rich coffee, to pale tan, like weak tea, depending on the bark texture and concentration of nutrients and other substances picked up from the bark.

The researchers collected stemflow from healthy, dead and stressed sweetgum trees to determine if stressed trees could cause cascading impacts in forest ecosystems. For example, changes in stemflow from dead or dying trees may change the soil and consequently impact other organisms such as moss and understory vegetation. When they analyzed their samples, the researchers found significantly less stemflow made it to the forest floor from the dead trees. Another finding was unexpectedly high sugar concentrations in stemflow from dead and stressed trees.

What’s the potential cause and effect of the stemflow changes? “The stemflow’s being absorbed by the dead trees. They’re acting like sponges,” says Chin. “Suddenly you cut off water, nutrients and dissolved organic carbon to the forest floor. Not only is this changing the health of the trees, but it changes the health of the forest floor.” And Levia speculates that the high sugar transport by stemflow from dying trees could alter microbial communities in near-trunk soil.

“Our results signify that the transition from healthy trees to ghost forests changes the magnitude and chemistry of stemflow, leading to pronounced differences in dissolved carbon inputs,” shares Levia. “Further research will better contextualize these changes in stemflow chemistry on the overall cycling of carbon in coastal forests.”

These underground changes ultimately affect how coastal forests store carbon, and understanding these processes could help scientists predict which forests are most vulnerable as sea levels continue to rise.

This research is one piece of the work that the team is doing to investigate stemflow, including how stemflow is impacted by wildfires. “People are beginning to understand the role that stemflow plays in forest floor carbon cycling,” adds Chin. “We’re kind of preaching the gospel, not just to the general community, but our own scientific community.”

“Stemflow is a significant transporter of nutrients and other important chemicals in these coastal forests. It’s something that we should study more and not overlook whenever it comes to carbon cycling, especially in these vulnerable ecosystems,” says Chittakone. 

The research was funded by the U.S. National Science Foundation.

Visit the ACS Spring 2026 program to learn more about this presentation, “Linking stemflow to groundwater in ghost forests: Accessing tracers and impacts of tree health on dissolved organic carbon composition,” and other science presentations.

The quality and quantity of dissolved organic matter changes as a healthy forest transitions into a ghost forest.

Credit

Samantha Chittakone, Delphis Levia and Robyn O’Halloran

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Title
Linking stemflow to groundwater in ghost forests: Accessing tracers and impacts of tree health on dissolved organic carbon composition

Abstract
Coastal margins along the Atlantic seaboard are undergoing profound transformations due to rising air temperatures, sea level rise, and saltwater intrusion. A visible consequence is the emergence of “ghost forests”, characterized by moribund and dead trees that potentially disrupt biogeochemical cycling. Such disruptions would include altering stemflow (the intercepted precipitation that is funneled over tree stems), which serves a critical yet understudied role in carbon cycling. In coastal forests, where the groundwater table is at or near the surface, stemflow may interact with groundwater more directly, possibly introducing previously unaccounted-for organic matter. This study explores the interactions between stemflow and groundwater from moribund and healthy sweetgum trees (Liquidambar styraciflua L.) within a coastal forest experiencing the effects of sea level rise. Groundwater wells were placed near tree trunks and measured water levels for trees with stemflow collection systems, where groundwater is unaffected by stemflow, and trees without collection systems, where stemflow can enter the ground and affect groundwater. Following each rain event, the water table near moribund and healthy tree trunks was consistently higher, suggesting contributions from stemflow. Dissolved organic matter (DOM) fluorescence indices (FI) for stemflow impacted groundwater (median value of 1.46) revealed the presence of allochthonous precursors, while less stemflow influenced groundwater (median of 1.90) revealed DOM that has been microbially processed. Dissolved lignin was also directly measured in these samples for use as a tracer of tree-derived organic matter. The median concentration of total dissolved lignin products in stemflow-influenced groundwater near healthy trees (0.88 µM) was greater than that of unimpacted groundwater (0.54 µM), corroborating results from the FI analysis. By defining the relationship between stemflow and groundwater, the quality and quantity of carbon entering these vulnerable ecosystems can be determined, providing insight into the effects of tree health on carbon cycling.

 

New study predicts Siberian-Arctic heatwaves a month in advance using stratospheric ozone and sea ice signals

Institute of Atmospheric Physics, Chinese Academy of Sciences

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A new study published in Advances in Atmospheric Sciences reveals a reliable method for forecasting disruptive Siberian-Arctic heatwaves (SAHs) up to one month in advance. The research identifies Arctic stratospheric ozone depletion and Kara Sea ice loss as key early-warning signals, offering a crucial tool for improving preparedness in a rapidly warming Arctic.

April heatwaves over the Siberian Arctic are becoming more frequent and intense, triggering widespread wildfires, accelerating permafrost thaw, and threatening northern communities. Accurate prediction of these extreme events is vital for mitigation efforts but remains challenging due to the complex interplay of atmospheric and cryospheric processes.

A research team led by scientists from Beijing Normal University has now developed a statistical model that successfully predicts April surface temperatures in the Siberian Arctic with a correlation skill of 0.75 for the period 1979–2022. The model uses observations from March of three key predictors: total column ozone over the Arctic, the Arctic Oscillation index, and sea ice concentration in the Kara Sea.

"Think of the atmosphere as having a memory," explains Dr. Fei Xie from Beijing Normal University, corresponding author of the study. "Extreme conditions in the stratosphere and the cryosphere in March leave an imprint that reliably shapes the weather pattern over Siberia in the following month. Our model decodes this memory to provide an early warning."

The model demonstrated strong practical utility, correctly predicting six out of the seven major SAH events since 1979. The analysis further distinguished the primary drivers behind individual events: three heatwaves (including the record 2020 event) were primarily forced by extreme ozone depletion, three others were driven mainly by severe sea ice loss, and one event resulted from a combination of both factors.

The study also uncovered a shift in the dominant long-term driver of regional warming. "From 1979 to 1997, the warming trend was almost entirely linked to human-induced ozone depletion in the Arctic stratosphere," says Yan Xia, the study's lead author. "After 1998, while ozone loss continued, the accelerating decline of Kara Sea ice has become the leading contributor to the warming trend."

This shift has critical implications for the future. While the Montreal Protocol is driving stratospheric ozone recovery, Arctic sea ice loss is projected to accelerate. "The future frequency of Siberian-Arctic heatwaves will likely hinge on the competition between these two trends," notes Dr. Xie. "Our model provides a framework to monitor these competing influences in real time."

The researchers highlight the potential for operational forecasting. By tracking March ozone and sea ice extremes, their simple yet powerful regression model could be implemented to provide actionable forecasts, giving wildfire managers, policymakers, and Arctic communities valuable lead time to prepare for impending heatwaves.

Looking ahead, the team plans to refine the model by incorporating daily-scale data for even earlier warnings and to explore its performance under future climate scenarios projected by sophisticated Earth system models.

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Journal

Advances in Atmospheric Sciences

DOI

10.1007/s00376-025-5256-1 

Article Title

Subseasonal Prediction of April Siberian-Arctic Heatwaves Using a Dynamical–Statistical Approach

Europe could completely replace fossil fuels in road transport

KIT study shows how much liquid fuel can be produced in the EU from residual and waste materials

Karlsruher Institut für Technologie (KIT)

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Combustion engines for all applications can run with the reFuels (renewable fuels produced using various processes) developed at KIT. (Photo: Markus Breig and Amadeus Bramsiepe, KIT) 

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Credit: Photo: Markus Breig and Amadeus Bramsiepe, KIT

“Europe has enough renewable resources to be mobile without fossil fuels in the long term,” said Professor Thomas Hirth, Vice President Transfer and International Affairs at KIT. “That’s good news given the current uncertainties in international energy markets. If we use residual and waste materials efficiently, we can make road traffic less dependent on energy imports while reducing CO₂ emissions.”

 

Diversity of Renewable Raw Materials Makes Europe More Independent

The study, commissioned by BMW AG, was based on a set of conditions for aggressive implementation of the Paris Agreement. It relates to a favorable scenario whose preconditions are still to be established by government and the public. The study shows that especially large amounts of residual and waste materials can be used, e.g. straw from agriculture, wood scraps from forestry, or organic waste. Also available are catch crops (plants that are grown between two main crops) and energy crops that grow on low-yield land and do not compete with food production.

 

This diversity ensures that the raw material base remains stable and is not dependent on a single material. “Many people think used cooking oil is the main source of renewable fuels, but it actually amounts to around one percent of the raw material portfolio,” said Professor Thomas Koch from KIT’s Institute of Internal Combustion Engines (IFKM). “The really great potential is in materials like plant residues and wood fiber, which are produced in many processes anyway and can provide sufficiently climate-friendly fuels. But that can only be successful if the production of advanced reFuel biofuels is given the necessary priority by government and the public.”

 

From Residues to Fuels

The researchers investigated several ways to produce useful fuels from biomass, including the HVO (hydrotreated vegetable oil) process, in which oil-bearing residual materials are hydrogenated to produce a diesel substitute, and methanol-based processes. In the latter, a gas is produced from plant residues as an intermediate product that is then processed to produce gasoline or diesel substitutes.

 

“We can produce high-quality fuels from a wide range of residual materials with these processes,” said Professor Nicolaus Dahmen from KIT’s Institute of Catalysis Research and Technology. “That’s important because Europe has many kinds of biomass. Even if the raw material mix changes, the technologies still work.”

 

While HVO is already available at the pump, fuels from other processes are still in development. They are being produced at KIT and tested in vehicles. Fuel can also be produced in large quantities with the tested processes. The study also shows that yield can be further boosted by adding more hydrogen.

 

Liquid Fuels to Remain Important Despite Electromobility

According to the IFKM’s Dr. Olaf Toedter, there will still be significant demand for liquid fuels in spite of Europe’s ambitious electrification plans. “Many vehicles will remain in service for a long time,” Toedter said. “Renewable fuels offer a way for this fleet of existing vehicles to directly avoid CO₂ emissions.“

 

What the Study Investigated

The study investigated which renewable raw materials are available in Europe, how they can be converted in various processes to renewable fuels, and what quantities can be produced. It was based on a set of conditions for aggressive implementation of the Paris Agreement. In the study, the researchers focus on a favorable scenario whose preconditions are still to be established by government and the public. The study also considers how vehicle fleets will develop in the years ahead, the fraction of traffic for which renewable fuels can replace conventional ones, and competition from sectors such as industry, energy, aviation, and shipping.

 

KIT conducted the study in cooperation with the Deutsches Biomasseforschungszentrum (a biomass research institute), Freyberger engineering GmbH, and BMW AG; the study was commissioned by BMW AG. (mex)

 

Original publication

Toedter, Olaf; Heinz, Alexander; Koch, Thomas; Glaser, Manuel; Dahmen, Nicolaus; Cyffka, Karl-Friedrich; Karras, Tom; Görsch, Kati; Lentjes, Christoph; Wittmann, Jan-Hubert; Rausch, Benjamin; Menger, Lars: From raw material to fossil-free mobility: Europe's potential for a renewable fuel market. KITopen 2026. DOI: 10.5445/IR/1000191586 

 

More about reFuels

 

In close partnership with society, KIT develops solutions for urgent challenges – from climate change, energy transition and sustainable use of natural resources to artificial intelligence, sovereignty and an aging population. As The University in the Helmholtz Association, KIT unites scientific excellence from insight to application-driven research under one roof – and is thus in a unique position to drive this transformation. As a University of Excellence, KIT offers its more than 10,000 employees and 22,800 students outstanding opportunities to shape a sustainable and resilient future. KIT – Science for Impact.

 

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DOI

10.5445/IR/1000191586 

Article Title

From raw material to fossilfree mobility: Europe's potential for a renewable fuel market

Article Publication Date

23-Mar-2026