Castor cake is an organic byproduct derived from the seeds of the castor oil plant (Ricinus communis). After extracting castor oil from the seeds, the remaining solid material is processed into castor cake, which is rich in nutrients and used primarily as a natural fertilizer and soil amendment in agriculture. Castor cake is a granular or powdered material with a light brown to dark color. It has a distinct odor due to the residual oil content.