Sustainable Pistachio Dehulling Waste Management and Its Valorization Approaches: A Review

Abstract

Purpose of Review In countries such the USA, Iran, and Turkey, pistachio nut is considered one of the most economically valuable agricultural products. Pistachio production and related dehulling processes generate a large quantity of organic waste, containing green hull, cluster woody part, shells, and leaves. The inadequate conventional management of such wastes calls for sustainable and economical strategies not only to enhance resource efficiency but also to create value. Recent Findings Pistachio residues have a high content of total extractives and essential oils and a considerable amount of phenolic compounds that explain their good antioxidant activities and other potential human health benefits. Furthermore, considering the generation volume (about 660,000 tons) and lignocellulosic structure, pistachio residues can also be sustainably used to produce value-added products, such as biofuels, phytochemicals, activated carbon, and other potential bioproducts such as filamentous fungi as protein enriched biomass, single-cell protein (SCP), and volatile fatty acids. In general, recent studies have not comprehensively investigated all value-added potential products. Summary This review provides a thourough insight into the present pistachio processing industries, and pistachio waste chemical composition and characteristics. Furthermore, the applications of pistachio residues as a renewable source for the production of potential value-added products by various thermochemical (pyrolysis, gasification, and liquefaction), physicochemical (solvent extraction, ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and extraction by pressurized liquids (PLE)), and biological (anaerobic digestion (AD) and fermentation (solid-state and submerged)) processes are presented including an analysis of the advantages and disadvantages of such methods. In this regard, production of new products such as edible filamentous fungi and antioxidant, and their market appeal has been briefly considered.

Direct biomass valorisation to γ-valerolactone by Ru-PNP catalysed hydrogenation in acid

“…Taking into consideration the generation volume (approximately 660 000 tons) and lignocellulosic structure, pistachio residues can also be sustainably utilized to yield value-added compounds. 34 Therefore, pistachio shells have been employed for this transformation as well, and a 12 wt% yield of GVL is obtained after 48 hours (26% yield 35 ).…”

Direct valorization of biomass waste to gamma-valerolactone

“…Pistachio production and related dehulling processes generate large quantities of agricultural waste. Taking into consideration the generation volume (approximately 660,000 tons) and lignocellulosic structure, pistachio residues can also be sustainably utilized to yield value-added compounds 40 . Therefore, pistachio shells have been employed for this transformation as well, and a 12 wt% yield of GVL is obtained after 48 hours (26% 41 ).…”

Role of advanced oxidation processes in lignocellulose pretreatment towards biorefinery applications: a review on emerging trends and economic considerations

“…The use of catalysts and promoters can further facilitate these reactions, allowing a reduction in the high pressure and temperature conditions normally required for the process. 7 The chemical transformations involve all three key components within biomass. Through solubilization and hydrolysis, hemicelluloses are fragmented into monomeric sugars, such as xylose and arabinose, which are characteristic products of this degradation and typically found in the liquid phase.…”

“…Some physico-chemical pretreatments have the benefit of avoiding the use of chemicals or catalysts, such as liquid hot water pretreatment; 6 however, in general, they eventually generate inhibitory byproducts, require high investment and operating costs for high-pressure systems, and use chemical agents. 7 Alternatively, biological pretreatments, which employ lignocellulolytic microorganisms such as fungi and bacteria to break down the structure of biomass, are characterized by low energy demand and environmental impact, mild conditions, and no inhibitor generation during the process, but they are not still viable on a large scale due to their high cost. 8 Thus, in parallel with these pretreatments, the scientific community is also considering the possibility of lignin valorisation to produce chemicals or fuels by using ionic liquids and deep eutectic solvents.…”