The role of constructed wetlands for biomass production within the water-soil-waste nexus

Abstract

The use of constructed wetlands for water pollution control has a long standing tradition in urban, peri-urban, rural, agricultural and mining environments. The capacity of wetland plants to take up nutrients and to filter organic matter has been widely discussed and presented in diverse fora and published in hundreds of articles. In an ever increasingly complex global world, constructed wetlands not only play a role in providing safe sanitation in decentralized settings, shelter for biodiversity, and cleansing of polluted sites, in addition, they produce biomass that can be harvested and used for the production of fodder and fuel. The United Nations University Institute for Integrated Management of Material Fluxes and of Resources (UNU-FLORES) was established in December 2012 in Dresden, Germany, to assess the trade-offs between and among resources when making sustainable decisions. Against the backdrop of the Water-Energy-Food Nexus, which was introduced as a critical element for the discussions on sustainability at Rio þ20, the UNU was mandated to pay critical attention to the interconnections of the underlying resources, namely, water, soil and waste.Biomass for human consumption comes in the form of food for direct use, as fodder for livestock, and as semi-woody biomass for fuelling purposes, be it directly for heating and cooking or for the production of biogas and/or biofuel. Given the universal applicability of constructed wetlands in virtually all settings, from arid to tropical, from relatively high to low nutrient loads, and from a vast variety of pollutants, we postulate that the biomass produced in constructed wetlands can be used more extensively in order to enhance the multi-purpose use of these sites.

Research focusing on plant performance in constructed wetlands and agronomic application of treated wastewater – A set of experimental studies in Sicily (Italy)

“…In a study carried out in China on biofuel production from wetland biomass, the authors [66] explain the main aspects linked to improved bioenergy yields in CWs, such as the use of discharged waste nitrogen, the optimization of hydrologic flow patterns and the selection of productive plant species. When considering plant species, it is necessary to examine the adaptation of plants to environmental conditions, tolerance to wastewater properties, the availability of plant biomass and the energy yield of the plant species [26]. A .…”

“…australis and Typha angustifolia are considered the highest energy producers in CWs [66]; however, when evaluating the biomass yield, A . donax is the most high-yielding biomass species of those macrophytes, with an annual biomass yield of 35 t ha -1 on average, in open field conditions [26, 65, 67]. It is clear from literature that T .…”

“…australis are the most used and suited species for energy production in the world [66], whilst A . donax is relatively underused in CWs [26]. We felt it necessary in our study to ensure that a physical-energy characterization of above-ground biomass of the A .…”

“…If the use of biomass is permitted by law, it can be used as fodder for livestock, fertilizer or soil conditioner, but it can also be converted into bioenergy through direct combustion. Preliminary investigation of a number of aspects, such as the availability of plant biomass in the long term and plants energy yields, are essential, however [26]. This paper reports the main results of a set of experiments carried out on two HSSFs CWs in Sicily (Italy) between 2002 and 2016.…”

Bacteriological Quality of a Forage Grass (<i>Pennisetum purpureum Schumach</i>) Used in Constructed Wetland Removing Domestic Wastewater Pathogenic Microorganism

“…Thus, plants in constructed wetlands are not only useful for taking up nutrients, filtering organic matter, and creating an environment conducive to the proliferation of organisms to provide safe sanitation. The above-ground plant biomass can therefore be harvested and used for the production of food for direct use, fodder for livestock and for fuelling purposes [5].…”