Scientific Basis¶
Biowaste¶
The key component of the biomaterial investigated was plant biomass, responsible for the durability, and flexibility of the developed formulations.
Biowaste, a common term for food and garden waste, represents the major component of municipal waste in Europe reaching up to 34% [European Environment Agency, 2020a]. Industrial food waste is produced at every step of production and varies between 10% to 50% of each preceding step or the initial mass based on different studies [Girotto et al., 2015].
US Environmental Protection Agency (EPA) suggested Food Recovery Hierarchy to contribute to circular economy principles. One of the principles of the inverse pyramid is the increase of carbon footprint moving downside through triers. Starting from (i) source reduction and (ii) donation of the surplus of food to poor people, towards (iii) application of food waste as an animal food supplement or (iv) for industrial purposes.
The least alternative to direct dumping in the landfill is (v) composting or (vi) incineration [US Environmental Protection Agency, 2021]. Seeing the perspective of transforming my project from single piece production to industrial scale, my project aimed to potentially recover the biomass produced by industries. Instead of going to a landfill/incinerator, I propose to embed them into a polymeric matrix to enhance properties of the latter.
Phytoremediation¶
Phytoremediation is a cost-effective plant-based environment clean-up technique from inorganic and organic pollutants based on plant ability to extract, concentrate and transport hazardous chemical compounds from soils. Based on the compound physicochemical parameters and plant metabolic capability to metabolize the compound, 5 different types of phytoremediation are distinguished.
Phytostabilization is a process of metal mobility restriction by their precipitation in the root zone by symbiotic plant-microorganism interaction. Rhizofiltration is a process of pollutant adsorption inside the root. In case the pollutant is translocated after adsorption, phytoextraction is distinguished. Phytotransformation is related to the enzymatic metabolization of organic pollutants exclusively. Phytovolatilization is distinguished in case the pollutant was transformed into volatile compounds and transferred into air, which is true for organic, as well as inorganic pollutants.
Root vegetables are well known for their ability to accumulate pollutants, which threaten the health of the consumers [Meharg, 2016; Zhang et al., 2017; Gao et al., 2021] and impose importance on heavy metal and pesticide content control in agricultural products [European Environment Agency, 2020b].
On the other hand, the phytoextraction ability of root vegetables, particularly carrots, was assessed by different scientific groups and came up with promising results [Babaeian et al., 2016; Szabò, Czellér, 2009; Ding et al., 2014]. However, there is limited literature addressing the final fate of plant biomass after the phytoremediation cycle is finished. A number of studies addressed possibilities of maximizing profit from the harvested contaminated plants by processing them [Cozma et al., 2021], but to my knowledge nobody focused on heavy metal recovery and plant residues application in a separate product.
Heavy metal recovery¶
Traditional phytoremediation techniques end up with the recovery of metals from incinerated biomass [Fedje et al., 2021; Novo et al., 2017]. Such techniques require an extra amount of energy and produce carbon dioxide. Alternative treatments of heavy metal biomass include biochemical conversion for biodiesel production or composting [Cozma et al., 2021]. A contrasting technique that I suggest includes full utilization of the biomass produced after the remediation cycle. Metals can be extracted using sequential solvent extraction [Pavlíková et al., 2005], while the residual plant biomass will be utilized for biofabrication.
The technique suggested by Pavlìková et al (2005) is unique allegedly being the only one preserving the biomass in form of plant cytoskeleton residues, a colourless fibrous mass. The study focused on substance extractions that bind heavy metals in spinach consisting of 7 sequential steps and utilizing 5 solvents, which can be optimized and shortened based on the necessities of the current project. It also states a significant decrease in heavy metal content (As, Cd, Cu, Zn) proved by the results of atomic absorption spectrometry. The final biomass in our project can be assessed with a similar technique proving to have hazardous compound levels below the 1 mg/kg thresholds in the final product according to the REACH legislation [REACH; Annexe XVII].
Here I show you a case where phytoremediation has been carried out successfully
Bibliography¶
I have based my research on these articles, where I have been able to verify that a future recovery and obtaining a stable biomass is possible.
Babaeian, E., Homaee, M., & Rahnemaie, R. (2015). Chelate-enhanced phytoextraction and phytostabilization of lead-contaminated soils by carrot Daucus carota, 62(3), 339–358
Cozma, P., Hlihor, R. M., Rosca, M., Minut, M., DIaconu, M., & Gavrilescu, M. (2021). Coupling Phytoremediation with Plant Biomass Valorisation and Metal Recovery: An Overview. 2021 9th E-Health and Bioengineering Conference, EHB 2021
Ding, C., Li, X., Zhang, T., Ma, Y., & Wang, X. (2014). Phytotoxicity and accumulation of chromium in carrot plants and the derivation of soil thresholds for Chinese soils. Ecotoxicology and Environmental Safety, 108, 179–186.
European Environment Agency (2020a). Bio-waste in Europe — turning challenges into opportunities.
European Environment Agency. (2020b). Water and agriculture: towards sustainable solutions.
Fedje, K. K., Edvardsson, V., & Dalek, D. (2021). Initial Study on Phytoextraction for Recovery of Metals from Sorted and Aged Waste-to-Energy Bottom Ash. Soil Systems 2021, Vol. 5, Page 53, 5(3), 53.
Gao, J., Zhang, D., Proshad, R., Uwiringiyimana, E., & Wang, Z. (2021). Assessment of the pollution levels of potential toxic elements in urban vegetable gardens in southwest China. Scientific Reports 2021 11:1, 11(1), 1–13
Girotto, F., Alibardi, L., & Cossu, R. (2015). Food waste generation and industrial uses: A review. Waste Management, 45, 32–41. Meharg, A. A. (2016). Perspective: City farming needs monitoring. Nature 2016 531:7594, 531(7594), S60–S60.
US Environmental Protection Agency. (2021). Industrial Uses for Wasted Food | US EPA.