Waste meets poor soils: perspectives on sewage sludge recycling

L'abstract è presente nell'allegato / the abstract is in the attachmen

Biorefarmeries: Milking ethanol from algae for the mobility of tomorrow

The idea of this project is to fully exploit microalgae to the best of its potential, possibly proposing a sort of fourth generation fuel based on a continuous milking of macro- and microorganisms (as cows in a milk farm), which produce fuel by photosynthetic reactions. This project proposes a new transportation concept supported by a new socio-economic approach, in which biofuel production is based on biorefarmeries delivering fourth generation fuels which also have decarbonization capabilities, potential negative CO2 emissions plus positive impacts on mobility, the automotive Industry, health and environment and the econom

Recovery of humic acids from anaerobic sewage sludge: Extraction, characterization and encapsulation in alginate beads

Wastewater production is rising all over the world and one of the most difficult problems is the disposal of sewage sludge (SS). It is known that SS contains certain quantities of added-value compounds, such as humic acids (HA) which in turn have beneficial effects on soil quality and plant growth. On the other hand, SS can retain many pollutants, such as heavy metals. The present work aimed to implement an HA alkaline extraction protocol from anaerobic sewage sludge (ASS). Subsequently, the HA were quantified in ASS, in HA extract and in commercial HA, used as a benchmark, which gave results of 12.53%, 26.87% and 77.87% (on dry matter basis), respectively. FESEM and EDX analyses on lyophilized HA extract confirmed that no heavy metals had passed into the extract. Afterwards, in order to allow controlled release of the HA in soils, alginate beads containing the HA extract were created. Finally, a pot experiment in a greenhouse was performed using Chilean lettuce plants (Lactuca sativa L.) treated with alginate-HA extract beads. At the end of the greenhouse experiments, the hypogean dry biomass of the treated plants was significantly higher than for non-treated plants. The relevance of this study relies not only on the exploitation of green chemistry principles, by converting a waste stream into a high-value product, but also on the application of an approach following a circular economy model

Anaerobic digestates from sewage sludge used as fertilizer on a poor alkaline sandy soil and on a peat substrate: Effects on tomato plants growth and on soil properties

Anaerobic digestates from sewage sludge (SSADs) are a by-product of the wastewater treatment process that still preserves a certain agronomic interest for its richness in plant nutrients and organic matter. Fertilizing properties of two liquid and two dewatered SSADs were tested on tomato plants (Solanum lycopersicum L.). Pot experiments were performed on sandy soil and peat substrate under greenhouse conditions with a SSADs application rate of 170 kg N/ha over a period of three months. Beneficial effects of SSADs were reported on different growth parameters, revealing an increase in biomass and height up to 37.5 and 6-folds over untreated control. No phytotoxic effect occurred on SSAD-exposed plants. Chemical analysis of soils treated with SSADs showed enrichment of macro- and micro-nutrients as well as organic matter. In some cases, the chemical characterization of leaves revealed an enhancement of uptaken macronutrients. This study contributed in general to deepen the knowledge on the short-term growing season fertilizing effects of SSAD. Despite the treatment dosage was calculated only on nitrogen requirements, the study highlighted the importance of the other nutrients and organic matter on plant growth

Is anaerobic digestate from sewage sludge a potential solution for improvement of poor soils?

Sewage sludge is the principal waste coming from wastewater treatment and its production in Europe has rather increased in last twenty years. Nowadays, anaerobic digestion (AD) is the most diffused technique to stabilize SS and achieve energy recovery. Anaerobic digestate from sewage sludge (SSAD) is the principal by-product of this process. In the present work, one of the SSAD destinations (i.e. agricultural use) is reprised and challenged, evaluating the fertilizing effects of SSAD on a soil depleted of organic matter and plant nutrients. To this aim, four different SSADs (two liquid and two dewatered) were characterized and used to set up pot experiments with cucumber (Cucumis sativus L.), grown on two different substrates: a poor and sandy soil, and an organic substrate. SSADs and a mineral fertilizer were utilised at three different dosages: 85, 170, 255 kg of nitrogen per hectare (kg N/ha). Different plant parameters were measured such as germination, dry biomass, chlorophyll content index (CCI), net photosynthesis, stomatal conductance, CO2 concentration in substomatal cavity and root development. Results showed that the evaluated parameters were in general significantly similar or higher than untreated control. Moreover, the 170 kg N/ha dosage generally showed the best results compared to other dosages, especially for dewatered SSADs. All these results were much more evident for cucumber plants grown on sandy soil than on peat substrate, assessing the desired fertilizing effect on a poor soil