Study of volatile organic compounds (VOCs) emitted by orange bagasse drying process

Orange juice industries produce essential oils (d-limonene) and citrus pulp. The citrus pulp corresponds to 49 kg per 100 kg of orange processed and it is the bagasse of processed fruit after pressing, milling, pelleting and drying operations. However, bagasse drying process causes emission of volatile organic compounds (VOCs) because albedo and flavedo are present in the bagasse containing a residual amount of d-limonene and volatile oils unrecovered in other process steps. These compounds are a primary source of air pollution and it cause problems related to tropospheric ozone formation, photochemical pollution and human health problems, when being into the atmosphere. In this context, the emission of VOCs was studied, exposing particles of albedo and flavedo (Citrus sinensis L. Osbeck) to airflows with constant velocity at different exposure times and at seven temperatures. The experiments were conducted in an experimental module, where gas samples at the airflow outlet were collected for the quantification of furfural, α-pinene, β-pinene, 3-carene, p-cymene and d-limonene by gas chromatography with detector of flame ionization (GC-FID). The results showed that the main compounds emitted were d-limonene, 3-carene and α-pinene from the flavedo with a tendency to increase the emission with the increase of the temperature. The emission of VOCs occurred by steam distillation process predominating between room temperature and 160 °C, and by steam distillation followed by evaporation by thermal degradation effect due to the exposure time at temperatures between 160 and 250 °C.