1. Introduction
Natural fibers play a predominant role in the development of sustainable composites and in the movement towards sustainable development goals. Abundant availability with cheap or no cost, less density, less energy requirements for processing are some of the propitious points considered in the selection of natural materials against conventional materials[
1,
2,
3]. Biodegradability is a major phenomenon that adds merit to the naturally available materials. The agricultural by-products like wheat straw, rice straw, corn husks, soya bean straw, oat husks and leaves, sugarcane bagasse have been studied as potential fiber sources similar to coir, kenaf, jute, hemp and sisal [
4,
5]. Many research groups are meticulously searching for new fiber sources to meet the increasing demand for natural products and to reduce the usage of synthetic fibers produced from petroleum resources. On the other hand, reducing the wastages produced after primary consumption and or exploring an alternative usage for discarded agricultural residues is also on the rise [
6]. Of course, this is now important so that any future demand can be easily met.
Stepping towards sustainable goals is not always related to find new materials but lies in judicious use of available materials, even waste or discarded ones through primary or secondary applications or by recycling them [
7]. The process of recycling from waste starts with identification of waste, collection, separation, cleaning and using them as per requirements. The present work too focuses on utilizing such a waste in the fabrication of usable fiber reinforced polymer composites.
India's arable land area is approximately 159.7 million hectares (394.6 million acres). This does not include the unaccounted land used for self and local consumption. Indian Council of Agricultural Research (ICAR), India reported that the country generates around 350 million tonnes of agro waste every year. The major agricultural residues include rice straw, paddy straw, husk, leaves, pods, pseudo-stems and sugar bagasse. These wastes are simply dumped and or incinerated causing ecological problems. Agricultural and Processed Food Products Development Authority (APEDA) says that poultry products exports rose to USD 137 million in 2022-23 from USD 71 million compared to previous fiscal. Egg production in India increased to 126.53 billion during 2021-22 according to an official release. This shows that India is rich in livestock and has vast resources of poultry. It was reported that the poultry industry produces 8.5 Billion tons of poultry waste worldwide and India generates poultry waste of 3.3 million tons annually which is valued as USD 28.13 Billion in 2023 and is expected to reach USD 44.97 Billion by 2032 due to booming livestock sector [
8]. Environmental Assessment reports that India ranks fourth in the Mismanaged Waste Index (MWI) with 98.55 per cent of generated waste being mismanaged. This shows the pervasive nature of the problem and the huge potential left for exploration. Based on this scenario, the discarded wastes namely rice straw and chicken feather are considered as the subject of this present study.
Oriza sativa L. commonly called as Rice is one of the primary foods for Asians and in particular Indian subcontinent, the second largest producer of rice globally. Harvesting of rice produces residue called rice husk and rice straw which are used as cattle feed, making domestic shelters, fuel etc. Other uses include pulp and papermaking, production of bio-fuels and activated carbon [
9]. Fabrication of chip boards, furniture and medium density boards are some of the other commercial applications of straw fibers [
10]. As per a report, about 45 - 60% of rice straw is incinerated causing pollution and the remaining is used for the above mentioned applications [
9]. The applications of straw now expand and since they do not cause any harm to the environment during and after use, they may be considered as sustainable materials. Previous studies show that fibers can be extracted from rice straw. Rice straw contains cellulose (30- 36%), hemicellulose (19 – 32%), lignin (28 – 30) and Silicon (5.5%) [
11]. Many studies have reported the use of these fibers in the manufacture of fiber reinforced composites [
8,
9,
10].
In addition to the plants, animals too remain as a source of fiber. Wool and silk are some traditionally used fiber materials obtained from animals. Chicken, ducks, guinea fowls and geese are some sources of avian fibers [
11,
12]. Chicken feather were found to contain 92% keratin, 7% water and 1% lipid. Keratin is a complex protein structure with rachis, and quill [
13,
14]. Chicken feathers possess very low density as compared to synthetic and other natural fibers. Also, they are non-abrasive, hydrophobic with high thermal and sound insulating capacity [
15]. The morphological structure of the chicken feather fibers shows that it consists of many voids resembling the lumen or lacuna present in the plant fibers [
15]. Chicken feathers are the wastes produced in poultry farm and according to a study 10% weight of a chicken is occupied by its feathers [
11,
12]. They are to be disposed off without any damage to the environment. Typically, they are burnt or thrown off as garbage in some dilapidated areas causing pollution and environmental damage affecting mankind and other living things [
16,
17]. At this juncture, it would be imperative in transforming these wastes into some useful products. It would not only tackle the environmental issue to a certain extent, but also will be a source of income for villagers.
A proper mechanism need to be devised so that these enormous wastes do not cause any problem to the environment, if not they would affect both the underground water and land. Effective utilization of these resources can surely improve the socio-economic conditions of peasants and rural masses. From the view point of engineers, materials need to be replaced and refined to suit a variety of applications. The search for new materials is never ending and novel applications of prevalent materials are being found and tested. The use of fiber reinforced polymer composites are increasing and natural fibers reinforced composites are gaining momentum due to their positive aspects like light weight, bio-degradability and cost-effective nature. Keeping this scope and the available resources in hand, this study was conducted.
The objective of this present study was to disclose an auxiliary application of waste agricultural remnants and poultry litter by converting them into value added materials. Polymer composites were made using epoxy resin and varying vol% (5, 15, 25, 35 and 45%) of rice straw fibers and chicken feather fibers. The influence of these fibers on the flexural and impact strength of the composites and the effect of hybridization of these materials was studied. In addition, the effect of mercerization of these fibers and their implication on the flexural and impact strength of the composites was also studied.