In this research work a heterogeneous (solid base) nanocatalyst, originating from calcium waste materials, was produced. Firstly, calcium oxide (CaO) obtained by calcination (850 ⁰C for three hours) of chicken eggshells was used as a benchmark catalyst in the transesterification reaction of soybean oil. This catalyst was characterised using several techniques: Scanning Electron Spectroscopy (SEM), Infra-Red Spectroscopy (FTIR), and Particle Size Distribution (PSD), that are adequate for determining the specific surface area and volume of micro- and mesopores. The structure of the obtained CaO consisted of several agglomerates of white granular solids, with particles ranging from 50 to 332 nm (average of 117 nm) in size and having a specific surface area of 15.3 m²/g. Three different catalyst loadings were tested with regard to catalytic activity of calcium oxide under the same reaction conditions. Then, a nanocatalyst precursor, calcium acetate, was produced from the same eggshells used before. This precursor was then applied in a supercritical antisolvent (SAS) precipitation apparatus to control its particle size. After the precipitation, the precursor was calcined to convert it into nano-structured calcium oxide. This Nano-CaO was also characterised by the techniques used for the earlier referred benchmark catalyst and by Energy Dispersive X-ray spectroscopy (EDS) to identify the chemical elements present. The observed structure of this solid very much resembles the benchmark catalyst. However, the particle sizes are smaller, ranging from 23 to 453 nm (average of 77 nm) and have a specific area of 315.7 m²/g, which meant that an increase in specific surface area was achieved by decreasing the particle size. Regarding catalyst activity, a small amount of Nano-CaO was tested at the same conditions as before, and the best results showed an increase of 9% in transesterification reaction yield.