Capítulo 18: ELECTRONIC SOIL THAT INCREASES EFFICIENCY
Electronic Soil That Increases Efficiency
In today's world where food security is becoming increasingly important, a study conducted at Linköping University has shed light on the solution to the problem.
The research uses an innovative approach called "electronic soil" or "eSoil", a conductive growing medium for soilless agriculture (hydroponics). Hydroponics, a closed system based on water and nutrients, is already used to grow crops such as lettuce, herbs and some vegetables. This method is particularly advantageous in areas where arable land is limited or where environmental conditions are difficult. Eleni Stavrinidou and her team, who continue their research at the Laboratory of Organic Electronics at Linköping University, see the development of electronic soil as a significant advance in the field of hydroponics.
Electronic soil is not only environmentally friendly. It is also a safe alternative to previous methods that require low energy and contain high voltage and non-biodegradable materials, as it is made of cellulose and a conductive polymer called PEDOT. The findings of the study published in the journal PNAS are remarkable. Barley seedlings, which have not been traditionally grown in hydroponic systems, showed a 50% increase in growth in 15 days when their roots were electrically stimulated using eToprak. This discovery not only expands the range of products suitable for hydroponic cultivation, but also opens up the potential for more efficient growth with fewer resources. Stavrinidou emphasizes the urgency of finding new agricultural methods due to global population growth and the effects of climate change, and says that food demand cannot be met solely by existing agricultural methods.
While the results are promising, Stavrinidou acknowledges that there are fundamental biological mechanisms that are not yet fully understood. Thanks to this study, researchers now know that seeds use nitrogen more effectively, but they do not have clear information about how electrical stimulation affects this process. Stating that it is possible to make seeds grow faster with fewer resources, Stavrinidou believes that her work is an important step towards developing urban agriculture and hopes that it will open the door to more research and innovation in sustainable agriculture.
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The Role of Fertilizer in Microplastic Pollution
A long-running study in the UK has shown that fertilisers are a major source of microplastic pollution in agricultural soils, and that this pollution has increased significantly over the last 50 years.
Samuel Cusworth and colleagues from Lancaster University, UK, examined soil samples collected and archived at Rothamsted Research in a study that has been ongoing since 1843. They divided the samples into three groups: unfertilised soil, soil treated with organic fertilisers such as manure or compost, and soil treated with conventional fertilisers.
The researchers found little or no traces of microplastics in samples collected before 1966. However, they found a significant increase in microplastic concentrations in all three groups in samples from the past 50 years, meaning that even soils not treated with fertilizers were contaminated. However, soils treated with organic or inorganic fertilizers contained more microplastics, which increased the soil pollution of fertilizers.
It has been noted that inorganic fertilizers can spread microplastics because many are coated with polymers to ensure that nutrients are slowly released into the soil. A 2022 study found that large amounts of microplastics were being filtered from wastewater and concentrated in sewage sludge sold as agricultural fertilizer. It is estimated that between 31,000 and 42,000 tonnes of microplastics enter agricultural soils in Europe each year. Lettuce and wheat plants in particular have roots that can absorb microplastics from the surrounding soil and water. These can then pass from the roots into the edible parts of the plant.
Other studies have shown that microplastics can alter the physical, chemical and microbiological properties of soil, affecting its fertility and ultimately agricultural production.
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Polar Bear Fur-Inspired Sweater
According to a study published in the journal Science, a sweater knitted from fiber is much warmer than a jacket made of goose down, despite being one-fifth as thick. This fiber, made of a lightweight synthetic material called aerogel, retains its heat-trapping properties even after being stretched, washed and dyed. Previous studies have shown that aerogels are one of the best heat-trapping materials, and aerogel materials have been used for insulation in buildings. On the other hand, it was known that fibers made from aerogels were generally too brittle and delicate to be used in clothing weaving, and tended to lose their insulating properties after being washed or in humid environments.
Materials scientist Weiwel Gao from Zhejiang University in China and his team were inspired by polar bear (Ursus maritimus) fur when developing the aerogel fibre. Each strand of this fur has dozens of air pockets in the middle that prevent heat transfer. These air pockets keep the polar bear warm in the harsh Arctic climate. This porous structure is surrounded by a waterproof, flexible and tough outer shell. Gao and his colleagues used a method called "freeze-spinning", which they had previously used to make the fibre from a solution derived from silkworms, to create an aerogel fibre that mimics the porous inner structure of polar bear fur. They then coated the aerogel fibre with thermoplastic polyurethane, a flexible material commonly used in sportswear and equipment, to create a structure similar to the outer shell of fur hair. The aerogel was not damaged when stretched beyond 2% of its original length, but the developed fibre returned to its original length after being stretched to 1,000%. This showed that the aerogel fibre was stronger and more flexible than its predecessors, thanks to its flexible coating. The fibre retained its insulating properties after being stretched to twice its length 10,000 times. The fibre's structure and shape did not change when it was soaked in water, dried, or dyed.
The researchers then knitted a sweater made of aerogel fibre and compared its thermal insulation performance to a down jacket, wool, and long-sleeved cotton top. The team recruited a volunteer to wear each garment and measured the surface temperature of the garments in a room cooled to -20°C to assess how well they retained heat. The aerogel sweater was found to have the best insulation of all garments.
The average surface temperature of the sweater was 3.5°C, while the down jacket was 3.8°C, and it emitted slightly more heat than the sweater. The average surface temperature of cotton and wool tops was the least insulating, at 10.8 °C and 7.2 °C, respectively. The aerogel sweater did not lose its insulating properties after being washed in the washing machine several times. This suggests that the sweater could be durable enough to be worn frequently. Gao says the material they developed could one day be used to produce lightweight and durable clothing, such as sportswear, military uniforms and space suits, without the need for animal fur or feathers. Shu-Hong Yu, a materials scientist at the University of Science and Technology of China in Hefei, said the work is an important step toward developing thin thermal clothing.
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