Turning Plastic Waste into a Valuable Soil Additive

Since 1950, there have been more than 8 billion tons of plastic waste in the world. Plastic is a hazardous material for both the environment and living things. The impact of plastic on the environment is a negative consequence. This impact turned out to be very significant. It is estimated that there are 500 million to 1 billion plastic bags used by the world's population in one year. This means that there are about 1 million plastic bags per minute. To make it, it takes 12 million barrels of oil per year, and 14 million trees are cut down.

Recycling Plastic as One of The Plastics Waste Solution

Plastic is essentially a solid type of oil. It accumulates in the environment, is dirty, lingering, suffering and killing, fishing, birds and other animals. Plastics are also decomposed to enter our body and damage cells that damage cells or induce inflammation and immune response. Unfortunately, it costs more to recycle used plastic than it costs to make new plastic from petroleum. Abdul-Aziz's laboratory takes a different approach to recycling. It is committed to recycling waste (such as plastic and plant biomass) by incorporating them into valuable products.

Scientists at the University of California, Riverside, use a step of millions and tons of plastic waste produced per year, which are usually blocking streams and rivers, not to mention our ocean, causing pollution to occur.

Plastic Used as A Valuable Soil Additive (Source: https://scitechdaily.com/scientists-transform-plastic-waste-into-a-valuable-soil-additive/)

Converting Plastic Waste into a Highly Porous Form of Charcoal

The method to turn plastic waste into char involves mixing one of two common types of plastic (polystyrene, the plastic used for Styrofoam packaging, and polyethylene terephthalate or PET) with corn waste (the leftover stalks, leaves, husks, and cobs) known as corn stover. This mix was then cooked with highly compressed hot water (hydrothermal carbonisation).

The UCR chemistry and environmental technology assistant professor Kandis Leslie Abdul-Aziz and her colleagues provided a kind of plastic into a porous (permeable) form of charcoal. Such charcoal records carbon can be added to the soil to improve the falling water and ventilation of cultivated land. If the soil collapses naturally, it may also fertilize.

Plastic Waste are Recyclable

(Source: https://www.cnnindonesia.com/teknologi/20191127074615-199-451822/sampah-plastik-dilema-krisis-lingkungan-atau-cuan-ekonomi)

Char as a Soil Additive Increases Plant Production

The physical properties of the soil can increase the stability of soil aggregates, thereby creating a stable and ideal soil structure for plant growth which results in a good level of porosity and reduces the level of soil density. Improving the function of organic matter on soil chemical properties is to increase the cation exchange capacity which is the location and center of nutrients before being used by plants. Return of residues or crop residues combined with manure can improve soil physical conditions such as a good level of soil aggregation, increased soil permeability, reduced soil density, good soil porosity which results in increased root development.

Char as Soil Additive Increases Plant Production (Source: https://www.livescience.com/51720-photosynthesis.html)

Main Material and Processes Used in Making Char as a Soil Additive to Increases Plant Production

Activated carbon from charcoal produced from co-pyrolysis of corn stover and polystyrene or corn stover and polyethylene terephthalate removed 45% and 46% vanillin after 2 hours, respectively. The findings show that plastics have a synergistic relationship in producing charcoal precursors with increased porosity but antagonistically affect the adsorbent properties of activated carbon.

The materials and methods used are slow pyrolysis and co-pyrolysis, chemical activation of char, thermal degradation pyrolysis studies, surface area analysis, scanning electron microscopy, XRD and XPS, fourier transform infrared spectroscopy, batch adsorption study of vanillin. This finding shows that the properties of co-pyrolysis char can be influenced by the interaction between the plastic and the biomass during the process. The addition of plastics promotes side reactions that produce hydrogen or acids, contributing to a higher yield of the formed solid residue char.

SEM images of select AC samples as a function of the char obtained from the pyrolysis of CS and plastics in various mass ratios (Source: https://pubs.acs.org/doi/10.1021/acsomega.2c04815#)

Hypothesis of Activated Carbon on The Ability to Regulate Water

Abdul-Aziz and her colleagues want to know whether activated carbon can also be an effective water treatment medium for corn furnaces and plastic combinations. In this case, plastic waste can be implemented to remove water pollution. However, the activated charcoal from the mixture only absorbs about 45 % vanilla protein in the test of water sample - this makes it invalid to regulate water. Assistant Professor Kandis Leslie Abdul-Aziz theorized that there could be still some residual plastic on the surface of the materials, which is preventing the absorption of some of the vanillin molecules on the surface.

Activated Carbon Making Process (Source: https://scitechdaily.com/scientists-transform-plastic-waste-into-a-valuable-soil-additive/)

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References

1. University of California. (2023). Turning Plastic Waste into a Valuable Soil Additive [online]. Available at: https://scitechdaily.com/scientists-transform-plastic-waste-into-a-valuable-soil-additive/

2. University of California. (2023). Turning Plastic Waste into a Valuable Soil Additive [online]. Available at: https://www.sciencedaily.com/releases/2023/01/230109083450.htm

3. Mark Gale, Peter M. Nguyen, and Kandis Leslie Gilliard-Abdul Aziz. (2023). Synergistic and Antagonistic Effects of the Co-Pyrolysis of Plastics and Corn Stover to Produce Char and Activated Carbon [online]. Available at: https://pubs.acs.org/doi/10.1021/acsomega.2c04815#