Engineers turn cow manure into cellulose
Horizontal nozzle-pressurized spinning technique has potential to create manufacturing-grade cellulose from cow manure more efficiently.
A new technique to extract tiny cellulose strands from cow dung and turn them into manufacturing-grade cellulose, which is used to make everything from surgical masks to food packaging, has been developed by researchers from University College London (UCL), Edinburgh Napier University and Teesside University.
The study, published in The Journal of Cleaner Production, describes the new “pressurized spinning” innovation and its potential to create cellulose materials more cheaply and cleanly than some current manufacturing methods using a waste product from the dairy farming industry, cow manure, as the raw material.
The advance is the first time that manufacturing-grade cellulose has been derived from animal waste and is a prime example of circular economy, which aims to minimize waste and pollution by reusing and repurposing resources wherever possible.
The researchers said implementing the technology would be a win-win situation for manufacturers, dairy farmers and the environment.
Cellulose is one of the world’s most commonly used manufacturing materials. Found naturally in the cell walls of plants, it was first used to create synthetic materials in the mid-19th century, including celluloid, the original material used in photographic film.
Today it can be found in everything from cling film to surgical masks, paper products, textiles, foods and pharmaceuticals. Though it can be extracted organically, it is also often produced synthetically using toxic chemicals.
Pressurized spinning (or pressurized gyration) is a manufacturing technology that uses the forces of pressure and rotation simultaneously to spin fibers, beads, ribbons, meshes and films from a liquid jet of soft matter. The technology was invented in 2013 by a team from UCL Mechanical Engineering led by professor Mohan Edirisinghe.
“Our initial question was whether it could be possible to extract the tiny fragments of cellulose present in cow manure, which is left over from the plants the animals have eaten, and fashion it into manufacturing-grade cellulose materials,” Edirisinghe, senior author of the study, said.
“Extracting the fragments from dung was relatively straightforward using mild chemical reactions and homogenization, which we then turned into a liquid solution. But when we tried to turn the fragments into fibers using pressurized spinning technology, it didn’t work,” Edirisinghe continued. “By a process of trial and error, we figured out that using a horizontal rather than a vertical vessel containing surface nozzles and injecting the jet of liquid into still or flowing water caused cellulose fibers to form. We were then able to change the consistency of the liquid to create other forms, such as meshes, films and ribbons, each of which have different manufacturing applications.”
The new technique, called horizontal nozzle-pressurized spinning, is an energy-efficient process that doesn’t require the high voltages of other fiber production techniques such as electrospinning.
The team said adapting existing pressurized spinning machines to the new process should be relatively straightforward. The greater challenge is likely to be the logistics of sourcing and transporting the raw material, cow manure, but the environmental and commercial benefits of doing so would be significant.
Research in 2019 estimated that the amount of animal waste is due to increase by 40% between 2003 and 2030 to at least 5 billion tons, with many farms producing more manure than they can legitimately use as fertilizer.
“Horizontal nozzle-pressurized spinning could be a huge boost to the global dairy farming industry by putting this problematic waste product to good use and perhaps creating a new source of income,” Yanqi Dai, first author of the study from UCL Mechanical Engineering, said.
The research team is currently seeking opportunities to work with dairy farmers to take advantage of the technology and scale it up.
Core pressurized spinning research at UCL was made possible by grants awarded by UK Research & Innovation.
