The agricultural utilization of sewage sludge imposes a high level of sanitation and stabilization of organic matter in order to maintain soil, water and air qualities and to effectively use such bioresidues as a soil amendment and as a source of nutrients for plants. Improper sanitation poses a serious threat to human and animal health. Stabilization and sanitation of sewage sludge have the advantage of coupling safe sewage sludge recycling in agriculture with its disposal, as many economic and environmental constraints make discharging strategies more and more difficult to apply. This article reviews the various biological methods to sanitize sewage sludge and the efficiency and efficacy of these methods in eliminating pathogens and parasites. Available monitoring techniques are also discussed. Finally, a conceptual approach is presented on the basis of epidemiological and ecological studies in order to assess the environmental and health impacts of recycling sewage sludge through land application.

Upgrading consists of a range of purification processes aimed at increasing the methane content of biogas to reach specifications similar to natural gas. In this perspective, an environmental assessment, based on the Life Cycle Assessment (LCA) method, of different upgrading technologies is helpful to identify the environmental characteristics of biomethane and the critical steps for improvement. The aim of this work is to conduct an LCA of biomethane production from waste feedstock, using the SimaPro software. The study focuses on the comparison of several upgrading technologies (namely, membrane separation, cryogenic separation, pressure swing adsorption, chemical scrubbing, high pressure water scrubbing) and the on-site cogeneration of electricity and heat, including the environmental benefits deriving from the substitution of fossil-based products. The results show a better environmental performance of the cogeneration option in most of the impact categories. The Fossil resource scarcity is the impact category which is mainly benefited by the avoided production of natural gas, with savings of about 0.5 kg oil eq/m³ of biogas for all the investigated technologies, with an average improvement of about 76% compared to conventional cogeneration. The results show that the membrane upgrading technology is slightly more environmentally convenient than the other upgrading technologies.