Assessment of Natural and Post-Extraction Biomass from Acrocomia totai leaves: a Renewable Source of Energy

The search for cleaner production technologies and sustainable development tools has prompted increasing interest in the use of new, renewable raw materials for biorefineries and energy production. Thus, biodiesel production from the pulp oil (fruit oil) of Acrocomia totai Mart., a species of palm tree, is currently being investigated. However, the bioenergy potential of biomass from different parts of this species is still unknown, and may not be limited to oil from the pulp. Therefore, the aim of this work was to evaluate the leaves of A. totai as a secondary source of lipids and energy. Deciduous and fresh leaves were submitted to the Soxhlet and Bligh & Dyer extractions, and the presence of 1.0 to 5.8% of unsaturated fatty acids was observed by GC-FID analyses. The crude extract (CE) of the leaves was obtained by exhaustive extraction with methanol and then partitioned with different solvents. CE and its fractions were characterized by 1H nuclear magnetic resonance (NMR) spectroscopy, and the thermal properties were determined. The average specific heat of the grease fractions was 2.0 J g−1 K−1 and the calorific value of the polar and non-polar fractions varied from 15.7 to 34.1 MJ kg−1. For the whole leaves, the calorific value of the deciduous leaves was higher than that of the fresh leaves due to their lower water content, as determined by thermogravimetric-differential thermal analyses (TG-DTA) and infrared (IR) spectroscopy. The residual pies from the Soxhlet extractions of the deciduous and fresh leaves were characterized by TGA-DTA and scanning electron microscopy (SEM), revealing a lignocellulosic fibrous material with calorific values of 14.2 MJ kg−1 and 9.3 MJ kg−1, respectively, and an average specific heat of 1.6 J g−1 K−1. These thermal properties are comparable to those of sugarcane bagasse, a widely used type of biomass for industrial large-scale bioenergy production in Brazil. Therefore, these results indicated that it may be possible to harvest the deciduous leaves, a residue from the “macauba” cultivation, for energy cogeneration in biodiesel refineries.