Cattle grazing on pastures can meet some of their mineral requirement by drinking water and eating dirt. However, forages are the primary source of minerals (McDowell, 1996). Natural pastures, on the other hand, are typically mineral deficient since some soils’ are deficient in certain minerals especially with regard to phosphorus (P) and therefore insufficient to support appropriate Phosphorus content in pastures (
Chardon and Koopmans, 2005).
According to
Solomon and Mlambo (2017), in South Africa, animals, particularly cattle and goats, play a vital economical role. However, the adequacy and availability of important mineral elements from pastures and soil impact the performance and health of grazing ruminants
Islam et al., 2003) and herbage minerals affect the performance of grazing cattle
(Gao et al., 2016).
Mineral levels vary with species of pasture and mineral imbalances exist in different parts of the plant
(Fardous et al., 2010). Deficiencies, of the major minerals such as calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na) and sulphur (S), as well as the trace elements cobalt (Co), copper (Cu), iodine (I), manganese (Mn), selenium (Se) and zinc (Zn) can affect the production of livestock that depend on pasture grazing in most parts of the world
(Goswami et al., 2005). This compromises the health of animals and as a result, farmers’ income
(Dermauw et al., 2013).
Groundnut shells (GNS) are considered to be an agriculture waste in places where groundnuts are harvested and processed and if they are not used productively, they can become an environmental concern. According to
Nwofor and Sule (2012), groundnut shells are considered a waste product during and after harvest and when gathered in significant amounts in one location, they pose an environmental threat. Furthermore, groundnut shells make up around 20% of the weight of a dried peanut pod, implying that there is a substantial quantity of shell residue after groundnut processing (
Pratha and Prabakar 2020). The use of groundnut shell as a cattle feed source would help to reduce the number of shells accumulated in huge amounts
(Mokolopi et al., 2021). As a result, adopting the use of GNS as animal feed would not only solve waste disposal issues but also provide low-cost cattle feed, especially for community farmers.
Ground nut shells are effective and inexpensive feed supplement for improving the performance of communally grazed animals and they are inexpensive and widely available for both commercial and communal farmers in South Africa and other countries. Therefore, the aim of this review is to emphasise the relevance of groundnut shells as a feed supplement ruminant on pasture and its use in other industries.
Groundnut shells as a feed supplement
Groundnut shells could be used by some farmers to feed some of their animals
(Ikumapayi et al., 2021). Furthermore, according to the study conducted by
Abdulrazak et al., (2014), the relatively high value of crude protein and carbohydrates found on GNS during their experiment, indicated the need for use of them as agricultural feed for herbivores. GNS are also source of roughages for ruminants
(Varma et al., 2020).
According to
Akinfemi et al., (2012), the tropical agricultural waste and by-products (including GNS) showed a great variation in chemical composition and mineral content during their experiment. According to them the use of GNS in animal feeding is a common practice in tropical countries. GNS can also be used as animal feed due to its nutritional value and can well be tailored into advanced synthetic fibers
(Jubu et al., 2018). Ruminants in such in areas where GNS are readily available, largely depend on such crop residues for maintenance and production
(Millan et al., 2020). Aregheore (2000) considered crop residues, which includes GNS as suitable for feeding livestock.
Groundnut shells as a by-product
Worldwide, roughly 45.6 million tons of peanuts are produced each year
(Dahunsi et al., 2017). According to
Sorita et al., (2020), from the Food and Agriculture Organization of the United Nations the global peanut output in September 2019 was over 46 million tons. Peanuts are the most important food legume crop, with recent increases in global output and are now farmed in China, India, Africa, Japan, South America and the United States, with over 300 varieties planted globally
(Jayaprakash et al., 2019). According to
Ge et al., (2020), groundnuts are a significant grain legume that is widely farmed and enjoyed across the world, with shell, skin and peanut meal as by-products of industrial processing. According to the same authors, about 230-300 g of shells is generated per kilogram of peanut, with an anticipated global production of 10.7-14 million tons of peanut shell trash in 2017 and 2018.
Duc et al., (2019) regarded groundnut shells as a plentiful agro-industrial waste product that degrade extremely slowly under natural circumstances.
After the groundnut seeds have been extracted from their pods, GNS are the remnants and when the groundnut kernel is separated from its husk, they are considered as plentiful agricultural wastes
(Duc et al., 2019). Furthermore, they are low-cost agricultural by products that are plentiful (up to 30 million tons per year) across the world (
Sawe, 2018).
Groundnut shells are widely available and are so cheap that even the poorest can afford to buy. Furthermore, they account for around 20% of the weight of a dried peanut pod, showing that groundnut processing leaves a substantial quantity of shell residue. As a result of increasing groundnut productivity, groundnut shells are collected and are either burned or buried since they are not used. They are available plentiful throughout the world.
Characteristics of groundnut shells
Like other lignocellulosic wastes, GNS are complex substances made up of an interconnected net of cellulose, hemicelluloses and lignin. The functional groups of these components, namely carboxyl and phenolic hydroxyl groups, can act as physical and chemical bonding sites for biosorption in these materials
(Rangabhashiyam et al., 2014).
The presence of significant amounts of lignin (41%), cellulose (37%) and hemicelluloses (9%) distinguishes this agricultural waste
(Anike et al., 2016) and according to
Ramrez-López et al., (2003), they also have a pH of about 6.8, a significant surface area of at least 260 m2/m3 and a high porosity of at least 115, 74 per cent.
Groundnut shells that have been thermally or chemically altered have mostly been evaluated in adsorption batch studies to remove organic (
e.g., dyes) pollutants, with findings indicating that 60 percent of nitrogen has been removed
(Duc et al., 2019).
Groundnut shells make up about 20-30% of the weight of dried groundnut pods
(Vyas et al., 2016). Proteins, lipids, sugars, minerals, lignin and carbohydrates with lignocellulosic compositions such as hemicellulose and cellulose may be found in peanut shells, according to
Adhikari et al., (2018). According to them, they also contain numerous bioactive and useful chemicals that are safe for human ingestion (polyphenols, flavonoids, luteolin and carotene).
Importance of GNS
Ground nut shells can be utilised in a variety of sectors, including the food, feed and paper industries
(Bharthare et al., 2014). GNS have been explored for a variety of purposes over the years, including, adding them to animal feed, particularly for cattle (
Gary, 2002) and as dietary fiber for humans
(Sorita et al., 2020). They are considered to be agro-waste that are common in nature and degrade slowly in natural conditions
(Bharthare et al., 2014). According to
Vyas et al., (2016), plastic manufacturing, charcoal production, wastewater treatment, metal casting, gasifiers, composting of wet materials and usage as manure to improve soil conditions are all viable applications for ground nut shells.
The GNS residue is a good feedstock for bioconversion into biofuel since it contains around 38% cellulose, 36% hemicelluloses and 16% lignin
(Nyachaka et al., 2013). They further explained that GNS are potential substrate for commercial biofuel generation in industries like agricultural lignocellulosic wastes since they are renewable and inexpensive. They have the highest biomass production potential among diverse agricultural wastes, according to
Deeba et al., (2017) and are thus regarded as promising lignocellulosic biomass for the creation of biological energy. GNS may also be used to make biofuels
(Duc et al., 2019).
According to
Malawade et al., (2021), GNS bio-residues are utilised to generate biofuel, as adsorbents and in other uses. They are also an excellent biosorbent for the adsorption of heavy metals from industrial effluents
(Duc et al., 2019).
