From Coop to Carbon Capture
What if one of agriculture’s most stubborn waste streams could be looped back into the climate solution? NTU research suggests that chicken manure ash can be upcycled into a durable material for carbon capture.
Chicken manure rarely features in scientific headlines. It smells, it is costly to manage, and in land-scarce, population-dense Singapore, it presents a stubborn waste challenge for the country’s growing poultry sector.
Yet for researchers at from NTU’s School of Civil and Environmental Engineering, that unglamorous starting point has led to a surprising discovery. Chicken manure ash can perform as a stable, low-cost material for capturing carbon dioxide, retaining its capacity more effectively over repeated cycles than conventionally used calcium-based sorbents.
The finding, published in September 2025 in Chemical Engineering Journal, opens a new pathway for waste upcycling and carbon mitigation, transforming a problematic agricultural residue into a potential climate solution.
Managing the realities of farming
The team, led by Professor Grzegorz Lisak, didn’t set out looking for a new carbon capture method, but rather waste management.
“Chicken manure is a largely unaddressed waste stream in Singapore and will only grow as the nation seeks to ramp up domestic food production,” explained Lisak. “Farms pay significant costs to dispose of it, and many conventional treatment options simply don’t work well.”
The issue extends well beyond Singapore. First author and PhD student Jiahui Bu notes that in major poultry-producing countries such as China, the United States and Brazil, annual chicken manure generation reaches hundreds of millions of tonnes, making its management a critical global challenge for preventing pollution and disease.
Working with local agencies, the research team began by characterising chicken manure from different farms to understanding its composition and identify potential reuse routes.
Study authors Chan Wei Ping, Grzegorz Lisak and Jiahui Bu in the lab
Green potential
“When we analysed the waste, we found it contained a lot of calcium thanks to the additives in the hen’s feed,” recalled Bu. “That immediately suggested it might have potential for carbon dioxide capture.”
Carbon dioxide is a major contributor to global warming, and carbon capture is widely viewed as a necessary tool for limiting its impact, particularly in industries where emissions are difficult to eliminate entirely. At its most basic, carbon capture involves separating the carbon dioxide from industrial exhaust gases, concentrating it, and then either storing it securely or reusing it in other processes.
Despite its promise, carbon capture is not yet widely adopted. Many existing technologies remain costly, energy intensive, or prone to performance degradation. This limits large scale deployment and underscores the need for continued scientific work to improve efficiency and durability.
There are several approaches to carbon capture. For their work, Bu and Lisak made use of the chicken waste’s high calcium content and focused on calcium looping, a high-temperature carbon capture technology in which calcium oxide reacts with carbon dioxide to form a solid calcium carbonate. When heated again, the reaction reverses, releasing a concentrated stream of carbon dioxide for storage or reuse.
Out of the ashes
The researchers collected the chicken by-product from three separate farms, dried and ground it, then incinerated it at temperatures between 750 °C and 900 °C. This turned their 12 total samples into ash, a necessary step to make the calcium chemically reactive for carbon capture.
The team then used thermogravimetric analysis (TVA), a laboratory technique that measures how a material’s mass changes as it is heated, to track how the ash reacts with carbon dioxide and forms solid carbonates.
Interestingly, not each farm’s byproduct performed the same.
“It turns out that some of the manure can work very well for carbon capture, and some do not,” assessed Lisak. “It is dependent on a few factors, including the feed used in the chicken farms, as well as incineration temperature and whether anything was mixed into the waste before heated.”
Ash derived from one farm achieved a maximum carbon dioxide uptake of nearly 390 milligrams per gram. While, a high value for a waste-derived calcium sorbent, this uptake rate it is far below the 500-700 milligrams per gram typically achieved by the most common calcium looping material, limestone.
However, when the best-performing samples were tested in a fluidised bed reactor (FBR), a setup closer to real industrial conditions, they showed something limestone often does not: resistance to performance degradation.
“After 20 cycles, the chicken waste ash retained 70 to 80 percent of its carbon capture capacity using TGA testing,” explained Bu. “By comparison, limestone retained around 30 percent. This shows the ash perfoms better for long-term use.”
Counterintuitively, the “impurities” in the chicken product are likely what gave it durability.
“Limestone is a relatively pure calcium carbonate,” commented Lisak. “That makes it highly reactive at first when calcined to calcium oxide, but also very prone to sintering. Chicken manure ash contains other minerals like phosphates and silica which help stabilise the material’s structure.”
These so-called impurities act as thermal scaffolding, slowing pore collapse and preserving reactive surfaces during repeated high-temperature cycling. Advanced characterisation confirmed that while calcium oxide drives the carbon dioxide capture reaction, other mineral phases remain structurally stable and reduce degradation.
Chicken manure, in three forms
Limestone remains, for now
Does this mean chicken waste will replace limestone as the default benchmark material when it comes to calcium looping carbon capture? That’s unlikely at this moment given so many variables on its performance and the need for processes to first scale to industrial levels.
“Although it could make sense in local or niche systems, our goal is not to completely replace limestone,” concluded Lisak. “It’s to show that waste-derived materials can perform just as well or better over the long term, while avoiding further extraction of natural resources.”
The team is now testing whether adding eggshell-derived calcium to chicken manure ash can make the material more durable, helping it retain its carbon-capture capacity over repeated cycles. Like limestone, eggshells are composed largely of calcium carbonate, but previous studies suggest they behave differently under repeated high-temperature cycling.
By blending eggshell-derived material with chicken manure ash, the researchers hope to combine the strengths of both. This includes the high initial capture capacity associated with purer calcium sources and the long-term stability observed in manure ash.
Story by Laura Dobberstein, NTU College of Engineering
