title: Is phytoremediation without biomass valorization sustainable? - comparative LCA of landfilling vs. anaerobic co-digestion.
abstract: This study examines the sustainability of phytoremediation for soils contaminated with heavy metals, especially the influence of management of the produced metal-enriched biomass on the environmental performance of the complete system. We examine a case study in Asturias (north of Spain), where the land was polluted with Pb by diffuse emissions from an adjacent steelmaking factory. A Phytoremediation scenario based on this case was assessed by performing a comparative life cycle assessment and by applying the multi-impact assessment method ReCiPe. Our Baseline scenario used the produced biomass as feedstock for an anaerobic digester that produces biogas, which is later upgraded cryogenically. The Baseline scenario was compared with two alternative scenarios: one considers depositing the produced biomass into landfill, and the other considers excavating the contaminated soil, disposing it in a landfill, and refilling the site with pristine soil. A sensitivity analysis was performed using different yields of biomass and biogas, and using different distances between site and biomass valorization/disposal center. Our results show that the impacts caused during agricultural activities and biomass valorization were compensated by the production of synthetic natural gas and the avoided impact of natural gas production. In addition, it was found that if the produced biomass was not valorized, the sustainability of phytoremediation is questionable. The distance between the site and the biomass processing center is not a major factor for determining the technology's sustainability, providing distances are less than 200-300 km. However, distance to landfill or to the source of pristine soil is a key factor when deciding to use phytoremediation or other ex-situ conventional remediation techniques.
authors.affiliation: Área de Proyectos de Ingeniería, Departamento de Explotación y Prospección de Minas, Universidad de Oviedo, Calle Independencia 13, 33004 Oviedo, Spain. Electronic address: miguel.vigil@api.uniovi.es.
authors.forename: Miguel
authors.initials: M
authors.lastname: Vigil
authors.affiliation: Universidad de Santiago de Compostela, Escuela Politécnica Superior, R/Benigno Ledo, Campus Universitario, 27002 Lugo, Spain.
authors.forename: Manuel F
authors.initials: MF
authors.lastname: Marey-Pérez
authors.affiliation: Área de Proyectos de Ingeniería, Departamento de Explotación y Prospección de Minas, Universidad de Oviedo, Calle Independencia 13, 33004 Oviedo, Spain.
authors.forename: Gemma
authors.initials: G
authors.lastname: Martinez Huerta
authors.affiliation: Área de Proyectos de Ingeniería, Departamento de Explotación y Prospección de Minas, Universidad de Oviedo, Calle Independencia 13, 33004 Oviedo, Spain.
authors.forename: Valeriano
authors.initials: V
authors.lastname: Álvarez Cabal
mesh_terms: D000383:Agriculture; D001673:Biodegradation, Environmental; D056804:Biofuels; D018533:Biomass; D004777:Environment; D004787:Environmental Pollution; D019216:Metals, Heavy; D012987:Soil; D013030:Spain; D018505:Waste Management / Q000379:methods*
chemical_list: D056804:Biofuels; D019216:Metals, Heavy; D012987:Soil
keywords: Biogas; Contaminated soil; Life cycle assessment (LCA); Melilotus alba; Phytoremediation; Remediation