Integrated pyrolysis and biorefinery strategies for valorising forest biomass for calcium acetate production

Forest biomass represents a promising resource within the bioeconomy, with significant potential for conversion into high-value chemicals and bioproducts. This work proposes an innovative pyrolysis oil biorefining pathway to valorise two types of underutilised forest biomass: Aleppo pine (Pinus halepensis) and Holm oak (Quercus ilex), transforming them into a value-added bioproduct that can provide an economic incentive for sustainable forest management. A targeted biorefining methodology was developed, incorporating vacuum distillation, a phenolic adsorption resin, neutralisation with calcium oxide, and purification by acetone recrystallisation, to selectively isolate and purify acetic acid—the predominant component of bio-oil—in the form of calcium acetate (CaAc2). Holm oak consistently produced higher yields from the aqueous phase (AP) bio-oil compared to Aleppo pine, underscoring its superior suitability for this valorisation pathway. This methodology demonstrated high efficiency in recovering calcium acetate from bio-oil, yielding for Holm oak 34.4 g CaAc2 kg-1 of biomass (or 111.1 g CaAc2 kg-1 of AP bio-oil), with a 70.5 wt% recovery of the acid content of the bio-oil, and a 99.6 wt% removal of phenolic compounds. Calcium acetate from Holm oak was produced with a 93.5 wt% purity, increased through acetone recrystallisation. Overall, this work significantly advances pyrolysis oil biorefining by introducing a novel and effective approach for acetic acid extraction via calcium acetate production, a valuable industrial chemical.