Industrial hemp (Cannabis sativa L.) for phytoremediation: Energy and environmental life cycle assessment of using contaminated biomass as an energy resource

Abstract

The objectives of this study were to assess the environmental impacts of growing industrial hemp (Cannabis sativa L.) on the phytoremediation of heavy metal-polluted soil and using contaminated biomass as an energy resource. A life cycle assessment approach was adopted to evaluate the cumulative energy demand and climate change impact of using contaminated biomass for energy generation under 4 different scenarios. The industrial hemp supply chain scenarios include analyses of different subsystems (industrial hemp cultivation, seed processing, anaerobic digestion and biomass incineration for electricity generation) and different contaminated products harvested (seeds and straw, dried whole industrial hemp and fresh biomass for silage). As confirmed by a Monte Carlo simulation, the two scenarios that included anaerobic digestion and/or incineration of the contaminated biomass were the most energy-efficient and environmentally sustainable systems and obtained primary energy savings of 25.3 and 36.8 GJ ha−1, respectively, while avoiding emissions of 579 and 641 kg CO2e per reclaimed hectare, respectively. These results demonstrate the great potential of using contaminated areas for bioenergy (electricity) production while decreasing the exploitation of natural resources and pollutant emissions into the environment. Moreover, phytoremediation technologies combined with the energy valorization of biomass are recommended to change unproductive contaminated soils into exploitable and productive areas.