Christmas trees on curbs symbolize the end of the season of giving, but they’re not quite done giving: pine trees have always been a treasure trove of sustainable, biodegradable materials. John Dyer reports.
Some communities use them as barriers against beach and soil erosion. Others cut them up for mulch. Still others use them to construct or maintain forest trails.
But recent research has found that the trees can also provide the raw materials to manufacture paint and food sweeteners, a potential use that would lower greenhouse gas emissions that contribute to climate change.
“In the future, the tree that decorated your house over the festive period could be turned into paint to decorate your house once again,” said Cynthia Kartey, a PhD candidate studying biochemical engineering at the University of Sheffield in the United Kingdom, in a press release.
New method to recycle pine needles
The problem with Christmas trees is their pine needles, said Kartey. Each tree has hundreds of thousands of needles that emit carbon dioxide as they rot, a process that takes much longer than when deciduous tree leaves decompose.
While Christmas tree trunks and limbs are recyclable, the pine needles are not. A complex polymer known called lignocellulose that prevents their use as bioenergy or industrial applications composes around 85 per cent of their structure.
But heat and cheap and environmentally safe solvents like glycerol can break down lignocellulose. The by-product of that breakdown includes oils and charcoal. The oils contain edible, sugary glucose, acetic acid that’s used in paint, adhesives and vinegar, and phenol, a chemical with numerous applications. The charcoal stores carbon.
“My research has been focused on the breakdown of this complex structure into simple, high-valued industrial chemical feedstocks such as sugars and phenolics, which are used in products like household cleaners and mouthwash,” said Kartey. “Bio-refineries would be able to use a relatively simple but unexplored process to break down the pine needles.”
She added that the pine needles could be a sustainable replacement for synthetic sweeteners, acids and other chemicals.
Biomass could replace fossil resources
Britain alone consumes around 9 million Christmas trees annually. Around 7 million are thrown away in landfills. A campaign to promote their useful after-lives could also put an end to the importation of plastic Christmas trees that further emit greenhouse gases.
“The use of biomass – materials derived from plants – to produce fuels and chemicals currently manufactured from fossil resources will play a key role in the future global economy,” said James McGregor, a chemical engineer and senior lecturer at the University of Sheffield. “If we can utilize materials that would otherwise go to waste in such processes, thereby recycling them, then there are further benefits.”
McGregor and his students are seeking to discover the benefits of other products that now often fill dumps.
“We are currently investigating the production of valuable products from a variety of organic wastes, including forestry sources, spent grain from the brewing industry and food waste alongside investigating processes for the conversion on carbon dioxide into useful hydrocarbon compounds,” he said.
Finding sustainability in hitherto unknown places
McGregor’s work is part of a new trend of finding sustainability in hitherto unknown places.
Princeton University scientists documented how an orange juice company revived a barren portion of the Costa Rican jungle after dumping tons of orange peels in the area for years. Researchers have also looked into how to recycle olive pits and other waste from stone fruits in Greece. Scientists in Texas have identified the medicinal and industrial ingredients in avocado food husks.
Those revelations showed how natural ingredients that now represent no economic value could replace expensive chemicals that require or release carbon, said Debasish Bandyopadhyay, a chemist at the University of Texas Rio Grande Valley.
“It could very well be that avocado seed husks, which most people consider as the waste of wastes, are actually the gem of gems because the medicinal compounds within them could eventually be used to treat cancer, heart disease and other conditions,” Bandyopadhyay said. “Our results also suggest that the seed husks are a potential source of chemicals used in plastics and other industrial products.”