Comparative Study on Aquaponic and Hydroponic Systems for Sustainable Hemp Production in a Controlled Environment

Optimizing nutrient usage and controlling environmental parameters are crucial for improved crop growth and yield in the cultivation of <i>Cannabis sativa</i>, commonly known as hemp, using controlled-environment agriculture (CEA) systems. Although hemp cultivation in CEA is rapidly growing, the effects of different light-intensity treatments on early vegetative stages of hemp grown in hydroponic and aquaponic systems, along with the impacts on the environment and human health remains limited. This study employed a split-plot design, consisting of two layers of plant grow beds where each layer was exposed to different light intensities (LIs): approximately 752 µmol/m²/s (high light intensity) on the upper layer and 141 µmol/m²/s (low light intensity) on the lower layer. To assess the influence of two different LIs on plant growth indicators, specifically plant length and leaf area, the environmental parameters, including dissolved oxygen (DO), electrical conductivity (EC), pH, and water temperature (WT) were maintained within the same range for both systems. Additionally, the study incorporated a cradle-to-gate life cycle assessment (LCA) to precisely evaluate the environmental performance of both systems. Under the specific environmental and design conditions of this study, hemp plants grown in aquaponics showed greater growth performance in plant length compared to hydroponics (more than 42% higher for both LIs) and leaf area (28.3% greater under 141 µmol/m²/s), although the leaf area was 2.1% lower under 752 µmol/m²/s compared to plants grown in hydroponics. The LCA demonstrated that the aquaponic system provided an efficient and sustainable approach by integrating fish with hemp cultivation. The LCA results showed that aquaponics had a 22% reduction in midpoint and a 15% reduction in endpoint impact in contrast to the hydroponics system for hemp leaf cultivation. This research highlights the potential of aquaponic systems as a viable and sustainable alternative to hydroponic systems for hemp leaf cultivation in CEA under uncertain future climates.