Pine Needles as a Biomass Resource for Phenolic Compounds: Trade-Off between Efficiency and Sustainability of the Extraction Methods by Life Cycle Assessment

Abstract

Polyphenols are natural organic compounds with many possible applications because of their unique biological activities. They can be extracted from a wide variety of waste biomasses, and a great deal of interest exists in identifying extraction processes optimized in terms of both yield and environmental impact. In this framework, we have compared three techniques, namely, maceration and extraction assisted by either ultrasounds or microwaves, for the extraction of phenolic compounds from dry pine needles, largely available and underexploited biomass. The yields in terms of total phenolic compounds and condensed tannins were assessed as a function of the extraction time, and a life cycle assessment (LCA) approach was adopted for quantifying the environmental impacts of the three techniques. Despite being time-consuming, maceration is the least-impact method, immediately followed by (much faster) ultrasound-assisted extraction. The energy intensity is mainly responsible for the overall eco-profile of the three techniques, whose hotspot resulted to be electricity consumption. Short processing time is hence crucial, as the gains in terms of yield achievable by prolonging the extraction processes bring about energy burdens that nullify the environmental advantages. Even the choice of "greener" solvents (e.g., ethanol instead of acetone) appeared questionable, as the extraction yield has an impact greater than the "greenness" of the raw materials.

The need for hotspot-driven research

“…Replacing the acetone solvent with ethanol might make the extraction step greener but it makes the total harm of the process worse because it lowers the yield of extract. 4 For indirect hotspots, improving the yield or purity is a higher priority than reducing the harm caused by the step.…”

Strategy of Coniferous Needle Biorefinery into Value-Added Products to Implement Circular Bioeconomy Concepts in Forestry Side Stream Utilization

“…From lignans in needle aqueous extracts, taxiresinol, lariciresinol, pinoresinol, secoisolariciresinol, and hydroxymataresinol have been identified [59,61,67,68]. It has also been observed that the extraction of polyphenolic compounds from coniferous needles is affected by the preparation of the raw material and extraction conditions [58,68]. Comparing freeze-drying, vacuum-drying, and natural air-drying, freeze-drying yields the highest amount of polyphenol compounds.…”

Antioxidant and Wound Healing Bioactive Potential of Extracts Obtained from Bark and Needles of Softwood Species

“…The recovery of phenolic compounds from forest waste biomass is gaining considerable attention [49][50][51], and the choice of the method and solvent used for extraction is a particularly important step [52]. Traditional extraction methods, such as maceration, Soxhlet extraction, and percolation, lead to low extraction yields, require relatively large quantities of solvents, and are often time-consuming [53].…”