Apricot Seed Shells and Walnut Shells as Unconventional Sugars and Lignin Sources

Abstract

The present study focuses on using apricot seeds shells and walnut shells as a potential renewable material for biorefinery in Ukraine. The goal of the research work was to determine the relationship between the chemical composition of solid residues from biomass after acid pretreatment with H2SO4, alkaline pretreatment with NaOH, and a steam explosion pretreatment and the recovery of sugars and lignin after further enzymatic hydrolysis with the application of an industrial cellulase Cellic CTec2. Apricot seeds shells and walnut shells consist of lots of cellulose (35.01 and 24.19%, respectively), lignin (44.55% and 44.63%, respectively), hemicelluloses (10.77% and 26.68%, respectively), and extractives (9.97% and 11.41%, respectively), which affect the efficiency of the bioconversion of polysaccharides to sugars. The alkaline pretreatment was found to be more efficient in terms of glucose yield in comparison with that of acid and steam explosion, and the maximum enzymatic conversions of cellulose reached were 99.7% and 94.6% for the solids from the apricot seeds shells and the walnut shells, respectively. The maximum amount of lignin (82%) in the residual solid was obtained during the processing of apricot seed shells submitted to the acid pretreatment. The amount of lignin in the solids interferes with the efficiency of enzymatic hydrolysis. The results pave the way for the efficient and perspective utilization of shells through the use of inexpensive, simple and affordable chemical technologies, obtaining value-added products, and thus, reducing the amount of environmental pollution (compared to the usual disposal practice of direct burning) and energy and material external dependency (by taking advantage of these renewable, low-cost materials).

Agricultural Waste Valorization: Exploring Environmentally Friendly Approaches to Bioenergy Conversion

“…In Vietnam, various types of agricultural waste, including plant debris, food waste, plant waste, and animal waste, can be utilized for biochar production through physical steam-assisted reforming, improving plant productivity, agricultural profitability, and reducing airborne GHGs, fluid retention, and the soil's acidity [37]. Furthermore, different countries use walnut shells and apricot kernels to produce biosorbents and liquid fertilizers through an aqueous ammonia soaking biomass processing technique, where biosorbents show a high exchange capacity and cost savings, and the byproduct liquid fertilizer enhances wheat's and other crops' growth intensity [38].…”

Special Issue “Lignocellulosic Biomass II”

“…The authors concluded that both Tygra and Rajan varieties are promising raw materials for bioethanol production. Halysh et al [5] evaluated apricot seed husks and walnut shells as potential raw materials for biorefineries in Ukraine. Both materials were pretreated with either H 2 SO 4 , NaOH, or by steam explosion, and then subjected to enzymatic saccharification with commercial cellulases.…”

Unveiling the Potential of Apricot Residues: From Nutraceuticals to Bioenergy

“…The need for new materials that can aid in energy conservation has increased due to the worldwide crisis concerning energy resources [22]. As a by-product of processing apricots, apricot kernel shells (AKS) can be recovered and utilized again in different fields [23]. Here are a few instances of how AKS can be utilized: as a biomass fuel with a high calorific value to produce heat and electricity, as animal feed, as a highly porous material made of carbon added as a soil amendment to enhance the quality of the soil, as a lightweight building content, etc.…”