Metabolomics for Agricultural Waste Valorization: Shifting Toward a Sustainable Bioeconomy

Abstract

Agriculture has been considered as a fundamental industry for human survival since ancient times. Local and traditional agriculture are based on circular sustainability models, which produce practically no waste. However, owing to population growth and current market demands, modern agriculture is based on linear and large-scale production systems, generating tons of organic agricultural waste (OAW), such as rejected or inedible plant tissues (shells, peels, stalks, etc.). Generally, this waste accumulates in landfills and creates negative environmental impacts. The plant kingdom is rich in metabolic diversity, harboring over 200,000 structurally distinct metabolites that are naturally present in plants. Hence, OAW is considered to be a rich source of bioactive compounds, including phenolic compounds and secondary metabolites that exert a wide range of health benefits. Accordingly, OAW can be used as extraction material for the discovery and recovery of novel functional compounds that can be reinserted into the production system. This approach would alleviate the undesired environmental impacts of OAW accumulation in landfills, while providing added value to food, pharmaceutical, cosmetic, and nutraceutical products and introducing a circular economic model in the modern agricultural industry. In this regard, metabolomics-based approaches have gained increasing interest in the agri-food sector for a variety of applications, including the rediscovery of bioactive compounds, owing to advances in analytical instrumentation and data analytics platforms. This mini review summarizes the major aspects regarding the identification of novel bioactive compounds from agricultural waste, focusing on metabolomics as the main tool.

Agro-Industrial Waste Management: The Circular and Bioeconomic Perspective

“…Traditional (subsistence) agriculture is based on circular sustainability model, which ensures practically nil waste as residues are recycled or used for various purposes including maintenance of soil fertility [46,47]. Rise in global population, however, necessitated the intensification of agricultural production, linear-agricultural production system, globalization of food distribution, extensive storage, and agro-industrial processing, all of which generate extensive quantities and varieties of agro-industrial and food wastes [47,48].…”

“…Traditional (subsistence) agriculture is based on circular sustainability model, which ensures practically nil waste as residues are recycled or used for various purposes including maintenance of soil fertility [46,47]. Rise in global population, however, necessitated the intensification of agricultural production, linear-agricultural production system, globalization of food distribution, extensive storage, and agro-industrial processing, all of which generate extensive quantities and varieties of agro-industrial and food wastes [47,48]. Previously considered of little or no economic value, harvest leftovers, crop residues, animal wastes (bones, carcasses, blood, fat, feathers, hair, cartilages, skins, viscera, and dung), and food wastes (household, food service, and retail wastes) are today viewed as valuable resources of significant economic value such that they have become co-products or raw materials from agro-industrial processing, crop, forestry, and animal production [49].…”

“…biopesticides, single cell proteins, and animal proteins [13,67], and extraction of bioactive molecules and functional groups for varied applications [47,48,67]. Obviously, the potential availability and sustainability of feedstock supply for particular industry would depend on alternative or competing uses, cost of production and supply, crop yield and revenue from crops to farmers, and scale of crop farming enterprise [1,11,68].…”

“…Valorization of agro-industrial residues into food and feed ingredients, dietary supplements, novel bio-components, nutraceuticals, and pharmaceuticals is a potential huge industry and a vital component of the bio-economic and circular model of agricultural residue management. Bioactive molecules from agricultural and food residues include phenols, polyphenols, non-starch polysaccharides (cellulose, hemi-cellulose, and lignin), oligosaccharides, carotenoids, soluble fibers, terpenoids, proteins, tocopherols, and phytosterols [47,48,120,121]. Animal wastes and residues (dairy waste, sea food waste, slaughter wastes) have high levels of proteins, lipids, and minerals [48,122,123].…”

“…Khaksar et al [47] suggested the integration of metabolomics approaches into extraction of bioactive compounds from organic agricultural wastes to gain deeper understanding of the metabolic profile of agro-industrial wastes and enhance their The main classes of bioactive compounds [133]. [120].…”