Potential volatile organic compounds emission in indoor urban farming: a case study

A possible solution to cope with climate change and food insecurity is city greening, through extensive adoption of green infrastructures and urban agriculture. Little consideration is given to potential impacts that could be derived from elevated biogenic volatile organic compounds (BVOCs) released by plants. BVOCs can account for up to 90% of global VOC emissions. In indoor spaces, their levels are still unknown, although they may raise as much concern as for GHGs. The study presents the monitoring BVOCs emitted by a mature crop of green beans (Phaseolus vulgaris L. ‘Pongo’) cultivated inside an integrated rooftop greenhouse (i-RTG) in the Mediterranean area. Long-term air measurements were taken by passively sampling the atmosphere inside the i-RTG and in an inner open chamber hosting plants to monitor physiological emissions, as well as from the external outdoor environment, as control. An additional short measurement was taken on four plants in static-head space conditions to check detected BVOCs. Among a wide range of different volatiles terpenes, methanol and acetic acid were always found (including in the control), suggesting that their origin should not be associated with i-RTG plants. However, the detected signals were below the analytical procedures’ LLOQ (lower limit of quantitation). In the static-head space sample, most GC-MS signals could be identified as terpenoid compounds based on their MS spectra and by comparison of their chromatographic retention times with standards; though signals were faint, estimated values were below ppb. Accordingly, the results suggested passive sampling as a practical and easy-to-implement method to produce preliminary tracking of BVOC emissions. However, active sampling may improve the quantitative assessment of their levels inside the i-RTG.