Researchers in the United Kingdom have developed a novel method to convert ubiquitous cardboard packaging, a byproduct of surging e-commerce, into an effective biomass fuel for large-scale electricity generation.
Engineers at the University of Nottingham conducted the pioneering study, demonstrating for the first time that used cardboard can serve as an effective biomass source in power plants.
The findings, published in the journal Biomass and Bioenergy, offer a potential solution to the global challenge of cardboard recycling, which has seen an exponential increase due to the rise of online shopping.
The team’s meticulous approach involved shredding cardboard, analyzing its morphology and chemical composition, and studying its behavior under high temperatures.
They also devised a thermogravimetric analysis method to precisely quantify calcium carbonate in samples, a compound common in printed cardboard that affects its rigidity and combustion.
The research benchmarked cardboard against eucalyptus, a widely recognized industrial biomass, examining key properties that dictate fuel efficiency.
In combustion tests simulating rapid burning of pulverized biomass, cardboard particles produced highly reactive "chars"—the carbonaceous residues from initial combustion—that possess fine, porous structures, promoting faster and more complete burning.
A second test, simulating fluidized bed or grate systems, also showed cardboard maintaining an excellent combustion profile even with extended exposure in the furnace.
Scientists characterized over one million particles per sample, noting that cardboard tends to form "spongy aggregates" when ground, which poses a handling challenge for industrial processes.
While cardboard has a lower carbon content (38%) and calorific value (15.9-16.5 megajoules per kilogram) compared to eucalyptus (46.7% and 21 megajoules per kilogram, respectively), its more reactive chars accelerate combustion.
However, cardboard also exhibits a significantly higher ash content, ranging from 8.9% to 10.6%, in stark contrast to eucalyptus’s 0.6%, a critical factor for boiler operations.
Despite its technical potential, the study identifies three fundamental hurdles for industrial-scale implementation, starting with processing and handling. Ground cardboard forms low-density, spongy agglomerates that complicate internal transport, continuous feeding, and risk clogging in boilers.
The high calcium carbonate content, particularly in printed cardboard, presents variable effects. It can beneficially raise ash melting temperatures in some conditions but may promote slag formation or alter fuel quality in others, depending on the power plant’s technology.
Finally, industrial validation remains crucial. Laboratory trials must be followed by real-world operational tests in various boiler types to assess emissions, ash accumulation, and compatibility with other biomass sources.
This research suggests that common cardboard waste, usually destined for recycling, could play a role in the energy transition by diversifying fuel sources and leveraging an abundant, local resource.