Natural Plasticizer Production from Waste Coffee

Summary

This study obtained a plasticizer—referred to as a softener that reduces carbon footprint—from waste coffee grounds. When waste coffee accumulates, it generates significant carbon footprint and produces methane gas.

Waste coffee grounds were collected from facilities, sterilized, and dried. Oil was extracted from the dried waste coffee grounds using a supercritical extraction apparatus. The extracted oils, being a natural waste product, were intended for use as a softener causing minimal environmental harm.

Keywords: Waste coffee, carbon footprint, natural, plasticizer, oil.

1. Introduction

Plasticizers, also called plastifiers, are substances that improve the rheological properties of a material, enhance processability, improve mechanical properties, and promote homogeneous over heterogeneous characteristics. Many plasticizers have been used from the past to the present.

Their primary purpose is generally to improve flexibility properties through use in specific proportions within a material [1].

Due to their general structure, polymers are hard and brittle. Plasticizers were preferred to produce soft structures and enable use in other applications. Plasticizers are of low molecular weight or oligomeric type. They have chemically and thermally stable structures and usually prevent degradation during production. While having many different types, their preference in certain specialized applications is high.

Polymers containing plasticizers can be molded in industry, surface applications can be performed, and they can be easily processed in extrusion. Plasticizer materials are selected for 80% polyvinyl chloride (PVC). Plasticizer materials are also used in cellulose-based products, polyvinyl acetate (PVAC), urethane and acrylic production [2].

Phthalates, trimellitates, benzoates and terephthalates with monomeric structure are preferred in industry as plasticizers. However, many substances have been found to be 50% or more carcinogenic. Plasticizers, used for many diverse purposes from the past to the present, have brought many health problems to our world.

Carcinogenicity is the most serious of these. Plasticizers are indispensable products. Without these substances, material integrity cannot be achieved, brittleness increases, mass production cannot be ensured, and industrial development and direct economy are disrupted. For this reason, although plasticizer use has an increasing percentage globally, market share is also growing steadily.

However, demand is increasing day by day for natural plasticizers that are cheaper and can provide the desired technical performance in materials. Coffee is a beverage prepared from roasted coffee beans. However, our society does not know how to transform its waste into products that could be beneficial, at what level and for what purposes waste coffee can be used. When waste coffee accumulates, it produces methane gas at a significant level [3-5].

This methane gas directly increases carbon footprint and negatively impacts our world. Carbon footprint directly increases climate crisis, environmental damage, and global warming. However, if we can transform waste coffee, we will contribute economically to both the environment and our country and the world, thereby providing positive contributions in terms of sustainability, health, and economy.

Coffee production in Africa will decrease by 50% by 2050. Based on this, our coffee purchases will occur at higher costs. If we can properly and systematically manage the harm waste causes to the environment and recycle these wastes with correct and systematic equipment, we will make an important contribution to polymer technologies.

In this study we conducted, we aim to raise awareness that waste materials that would harm our environment and directly humanity and industry can contain high benefit through recovery. Oil was extracted from waste coffee grounds using a supercritical extraction apparatus and polypropylene (PP) composite granule production containing waste coffee oil was carried out with a twin-screw extruder.

PP was selected as a hard polymer due to its structure and frequently used in industry, and was processed at 1%, 3%, 5%, and 8% ratios of waste coffee oil, and granules were easily obtained with the aid of a twin-screw extruder.

2. Materials and Methods

2.1 Materials

Waste coffee grounds were collected from facilities in our vicinity. PP material was obtained from recycling companies.

2.2 Methods

Waste Coffee Recycling

Coffee grounds from facilities in our vicinity were collected via a container and first washed with tap water and subsequently with distilled water. After washing, waste coffee grounds heated in an oven at 50°C were sterilized by exposure to ozone gas for 30 minutes. The sterilized waste coffee grounds were placed in a container and sent to a supercritical extraction apparatus for oil extraction.

Oil Extraction Using Supercritical Extraction Apparatus

For waste coffee grounds, supercritical fluid extraction was selected as the most effective method for separation (extraction) and purification processes of heat-sensitive compounds. Through a process containing carbon dioxide (CO2) gas, combustion was performed and distilled to extract the oil contained in the waste coffee. The other waste pulp was stored as fertilizer and distributed to gardeners in our vicinity.

Granule Production from PP with Waste Coffee Oil-Containing Plasticizer Using Twin-Screw Extruder

In the twin-screw extruder, the plasticizer was homogeneously distributed in the molten polymer to obtain granules with equal properties. PP granules containing 1%, 3%, 5%, and 8% waste coffee oil-based plasticizer were obtained. For the purpose of determining mechanical properties, tensile specimens (dogbone) were obtained from PP and waste coffee-containing PP. They were tested on a 20 KN tensile apparatus to determine mechanical properties.

3. Results and Discussion

Oil was extracted from waste coffee grounds using a supercritical extraction apparatus with 80% yield. The 20% portion was stored as pulp fertilizer. The pulp was distributed to gardeners in our vicinity. As the plasticizer ratio increased, rheological properties were adjusted and mechanical properties showed stability at a certain value in tensile properties while elongation value increased.

While the PP specimen yielded 38 MPa, tensile strengths of 45 MPa, 44 MPa, 41 MPa, and 40 MPa were achieved with plasticizer use. However, elongation values increased as the plasticizer ratio increased and an elastic PP was obtained. A homogeneous structure was achieved around the specimen.

4. Conclusions

Oil was successfully extracted from waste coffee grounds using the supercritical extraction method. Waste oils at 1%, 3%, 5%, and 8% ratios were blended in PP in a twin-screw extruder and granulated. Specimens for tensile testing were obtained from PP and waste oil-containing PP using an injection system and their mechanical properties were determined.

Mechanical properties were higher compared to virgin PP, and as plasticizer ratio increased, mechanical properties decreased in tensile strength while elongation values increased. PP exhibited more flexible structural characteristics.

With this objective, as a call on behalf of facilities in our vicinity and to humanity, if we cannot extract the feasibility of our waste, by obtaining consulting services on this matter and ensuring that waste recycling is carried out in a controlled manner, it will be possible to provide usability in areas that will make significant contributions to industry and humanity, thereby providing high-efficiency contribution to our environment, our industry, and humanity.

 

References [1] Durak Akkoyun, B. (2017). Investigation of the Effects of Different Plasticizer Types on Polyester Polyol-Based Thermoplastic Polyurethane (Doctoral dissertation, Institute of Science). [2] Karal, O. (1998). Preparation of Poly (vinyl chloride) blends: spectroscopic, thermal, viscosimetric, mechanical and surface characterizations (Doctoral dissertation, Institute of Science). [3] TEKİN, Z. (2021). SUSTAINABILITY AND GREEN OPERATIONS PRACTICES IN COFFEE PRODUCTION: EXAMPLES FROM AROUND THE WORLD. [4] Kıvrak, F. (2022). Investigation of the Applicability of Commercial Coffee Waste in Insulation Material (Master's thesis, Konya Technical University). [5] Gizem, A. T. E. Ş., & ELMACI, Y. (2017). Potential Functional Component: Coffee Bean Husk. Academic Food, 15(1), 66-74.

 

Erdi Buluş - Instructor İstanbul Arel Üniversitesi ArelPOTKAM Gülseren Sakarya Buluş - Specialist İstanbul Provincial Health Directorate Enes Özgenç - Instructor Trakya Üniversitesi School of Health Services Dr. Emine Keleş - Instructor Trakya Üniversitesi Faculty of Architecture Department of Landscape Architecture