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Creating Solar Cells and Glass From Wood and a Billion Tons of Biowaste

Researchers map out how biomass from plants could replace non-renewable resources in optical applications.

According to a 2018 report by the Organisation for Economic Co-operation and Development, around 90 gigatons of raw materials are used each year across the globe. These numbers are set to almost double to 167 gigatons as the global population grows to almost 10 billion by 2060. To accommodate our ever-increasing demand for materials and energy without placing more pressure on the environment, scientists have turned to renewable raw materials, specifically biomass. While biomass is considered to be the strongest candidate to substitute fossil fuels in many applications, an international group of researchers has shown that lignocellulose, or plant biomass, can be used for optical applications as well, potentially replacing commonly used materials such as sand and plastics.

“We wanted to map out as comprehensively as possible how lignocellulose could replace the unrenewable resources found in widely used technology, like smart devices or solar cells,” said Jaana Vapaavuori, assistant professor of functional materials at Aalto University, who carried out the analysis with colleagues at the University of Turku, RISE – Research Institute of Sweden, and the University of British Columbia.

Lignocellulose is found in nearly every plant on earth. When scientists break it down into very small parts and put it back together, they can create new, usable materials. In their extensive review of the field, the researchers assessed the various manufacturing processes and characteristics needed for optical applications such as transparency, reflectiveness, UV-light filtering, as well as structural colours.

“Through combining properties of lignocellulose, we could create light-reactive surfaces for windows or materials that react to certain chemicals or steam. We could even make UV protectors that soak up radiation, acting like a sunblock on surfaces,” explained Vapaavuori.

“We can actually add functionalities to lignocellulose and customise it more easily than glass. For instance, if we could replace the glass in solar cells with lignocellulose, we could improve light absorption and achieve better operating efficiency,” noted Kati Miettunen, professor of materials engineering at the University of Turku.

Since forest biomass is already in high demand and vast carbon sinks are crucial to the planet’s health, the researchers believe that this highly underutilised renewable resource is an attractive option to explore. Around 181.5 billion tons of lignocellulosic biomass are produced annually in the biosphere, but only 8.2 billion tons are used by humans and more than a billion tons of biomass waste is created by industrial and agricultural activities each year.

However, a major obstacle has stood in the development of lignocellulose-based innovations: its manufacturing cost. Although nanocellulose has garnered significant attention in the early 2000s, it has only been recently that the energy consumption and production cost have been lowered enough to make industrial use possible. Another ongoing challenge lies in the fact that cellulose attracts water. “To use it in optical applications, we need to find a way make it stable in humid conditions,” explained Vapaavuori.

The researchers are now analysing bio-based materials and creating prototypes. While scientists at Aalto University have developed light fibres and light-reactive fabrics, they still need to come up with a way to scale up and commercialise these innovations.

“Either we create new uses for bio-based waste through government regulations or research brings about such cool demos and breakthroughs that it drives demand for renewable alternatives for optical applications. We believe that we need both political direction and solid research,” said Vapaavuori. [APBN]

Source: Kaschuk et al. (2021). Plant-based Structures as an Opportunity to Engineer Optical Functions in next-generation Light Management. Advanced Materials, 2104473.