Biomass production and energetic valorization in constructed wetlands

Constructed wetlands (CWs) are nature-based solutions for wastewater treatment, constituting an economically and environmentally sustainable alternative to conventional treatment units. CWs may provide various ecosystem services, including safe sanitation, water purification, uptake and removal of nutrients and pollutants, biodiversity promotion, regulation of climate conditions, and landscape improvement. Moreover, these systems can be considered as a bioresource providing a plethora of valuable assets, including treated water that can be reused to irrigate energy crops, and production of biomass. The biomass harvested from CWs can be composted and used as a soil amendment or can be converted into renewable and sustainable energy. This can be achieved, for instance, through direct combustion and biogas and bioethanol production. Indeed, rising attention is being given to the contribution of the biomass of plants colonizing CWs for energetic purposes, closing cycles in a circular economy. The present chapter focuses on the potential of biomass retrieved from CWs as an energetic resource. Several points are addressed, namely the type of plant species that can combine high biomass yields and water treatment efficiency, as well as the main factors that influence their growth performance in CWs. The impact of nutrient loading in influents, the time of the year, the number of harvests on plant biomass production, and its potential for valorization were also addressed.