RESUMEN

Biomass-based slow-release fertilizers (SRFs) are a sustainable solution for addressing food scarcity, improving fertilizer efficiency, and reducing pollution, whereas they still face complex preparation, high costs, and low release characteristics. This study introduces a simple and innovative approach to producing bifunctional green SRFs with controlled release and conditioning properties for saline soils and harsh environments. The method involves a one-pot preparation of microsphere-structured amine-modified lignin slow-release fertilizer (L-UX) using biomass lignin as the starting material. The L-UX demonstrates an exceptional fertilizer loading rate (66.2 %) and extended slow-release performance (288 h), effectively enhancing the fertilizer's release ability. Compared to traditional fertilizers, the bifunctional L-UX significantly improves soil water retention capacity (824.3 %), plant growth, and germination percentage in challenging soil conditions (133 %). These findings highlight the potential of L-UX as a large-scale controlled-release fertilizer in harsh environments. A life cycle assessment (LCA) was also conducted to evaluate the environmental impact of L-UX from its production to disposal. This revealed that L-UX has a minimal environmental footprint compared to conventional inorganic fertilizers. This study further supports the widespread application of L-UX as an environmentally friendly alternative.

Asunto(s)

RESUMEN

The application of natural zeolites to improve soil quality and functioning has become highly popular, but we still miss information about the long-term effects on the soil due to its application. This study assesses the soil quality index (SQI) of three distinct agricultural soil systems 6-10 years after a single application of natural chabazite zeolite as a soil amendment. These soils exhibit different management practices: intensive arable (cereals), intensive perennial (pear) and organic perennial (olive). In the arable system, a zeolite application dosage of 5, 10 and 15 kg m-2 was tested and compared to unamended soil. In the two perennial systems, an application of 5 kg m-2 was tested against untreated reference sols. A set of 25 soil physical, chemical and biological parameters linked to soil health and quality were analysed at each experimental site. The dataset was investigated through Principal Component Analysis (PCA) to calculate the soil quality index (SQI) using linear scoring. In the arable-cereal field, the SQI doubled (0.3 to ca. 0.6 for all amendments) in chabazite-amended plots; a dose effect was not recognizable. In both perennial fields, the SQI was significantly higher in the chabazite-amended plots (5 kg m-2) with similar increases as compared to the arable-cereal field. At each site, the indicators selected by the PCA were different, indicating that chabazite addition impacted soil quality differently in each cropping system. Overall, the results highlighted a significant increase in soil quality with chabazite amendment, which confirms its potential for increasing soil health in the long-term.

Asunto(s)

RESUMEN

Phytoremediation, as a cost-effective, highly efficient, environmentally friendly, and green approach, gained attention to the removal of metals, including heavy metals, from contaminated soils. The toxic nature of heavy metals can have an adverse effect on human health and the ecosystem, and their removal remains a worldwide problem. Therefore, in this study, a field experiment was carried out to evaluate the potential of Miscanthus × giganteus for the removal of ten microelements and heavy metals (Al, Zn, Fe, Pb, Cd, Co, Cr, Cu, Mn, Ni) from contaminated soil in the territory of a Municipal Waste Rendering Plant. Moreover, the effect of the incorporation of soil improver obtained upon composting biodegradable waste as well as the addition of highly contaminated post-industrial soil on the efficiency of phytoremediation and plant growth was described. The soil improver (SK-8) was applied to the soil at a rate of 200 Mg ha-1 and 400 Mg‧ha-1. Meanwhile, in the last object, 100 Mg‧ha-1 of highly contaminated post-industrial soil was added. Herein, the research was aimed at assessing the possibility of phytoextraction of heavy metals from soils with different physicochemical properties. The results showed that plants cultivated in soil with 400 Mg‧ha-1 of soil improver exhibited the highest yield (approximately 85% mass increase compared to the soil without additives). Furthermore, the application of a single dose of SK-8 (200 Mg ha-1) increased the uptake of Al, Fe, Co, Pb, Mn, Ni, and Cd by Miscanthus × giganteus compared to the soil without additives. Additionally, the performed biotests demonstrated no or low toxicity of the investigated soils affecting the test organisms. However, in all experiments, the phytorecovery of the elements did not exceed 1% of the amount introduced to the soil, which may result from a short cultivation period and large doses of SK-8 or highly contaminated post-industrial soil.

Asunto(s)

RESUMEN

This research was carried out to evaluate a local biogas plant's solid fraction digestate spreading in a citrus orchard and vineyard. Three spreaders were tested: a broadcast manure spreader in the citrus orchard, and two cylindrical-shaped spreaders in the vineyard; the first one working in broadcast configuration, the second one in localised configuration. Experimental tests assessed effective work time, mean work speed, digestate flow rate and longitudinal and transverse spreading uniformity. In the citrus orchard, the digestate was mainly spread in the centre of the inter-row (around 66%), with low variability between inter-rows (coefficient of variation (CV) equal to 2.7%) and much higher variability within inter-rows (CV = 31.4%). The effective work time was about 28% of total field time and real work capacity was about 0.96 ha h-1. In the vineyard, broadcast spreading released more on the right compared to the left (ratio 1.74) due to distributor disc rotation, whereas localised spreading was more uniform. Overall, variability between inter-rows had CV = 15.1% and within inter-rows CV = 33.3%. Real work capacity was about 0.16 ha h-1 for broadcast spreading and 0.26 ha h-1 for localised spreading. A preliminary economic evaluation, based on sub-contractor tariffs, produced the mean tariff for transaction and spreading costs of digestate in farms near the biogas plant.

RESUMEN

Sewage sludge production in European countries has widely raised in the last decade and its fate is currently landfilling, incinerators, composting or land application. To explore its agronomic potential, the main target of this work is to understand the effects of anaerobic digestates from sewage sludge (SSAD). To this aim, four different SSADs (two liquids and two dewatered) were characterized. On the liquid ones, Germination Index was evaluated through a plate bioassay with Lepidium sativum L. seeds; low concentrations of SSAD (2.5%) improved GI in one case, while at higher concentrations phytotoxic effects occurred in both. Then, pot experiments were set in climate chamber with Cucumis sativus L. grown for 30 days on two different substrates: a sandy, alkaline and poor soil, and peat substrate. All SSADs and a mineral fertilizer were used at three increasing dosages: 85, 170, 255 kg of nitrogen per hectare (kg N/ha). Results in terms of germination, dry biomass, chlorophyll content, net photosynthesis, stomatal conductance, CO2 concentration in substomatal cavity and root development were compared to a not treated control. All treatments gave results significantly higher or similar to control on all the parameters evaluated. Moreover, the intermediate nitrogen dosage (170 kg N/ha) generally showed the highest results compared to other dosages, especially for dewatered SSADs. All these results were much more evident for cucumber plants grown on an the alkaline, sandy and poor soil than on peat substrate, such demonstrating that SSADs have a fertilizing effect for plants growing on this kind of soil.

Asunto(s)

RESUMEN

An olive waste stream mixture, coming from a three phase-continuous centrifugation olive oil mill industry, with a typical wet basis mass composition of olive pulp 39 wt%, kernels 5 wt% and olive mill waste water 56 wt%, was subjected to hydrothermal carbonisation (HTC) at 180, 220 and 250 °C for a 3-hour residence time in a 2-litre stainless steel electrically heated batch reactor. The raw feedstock and corresponding hydrochars were characterised in terms of proximate and ultimate analyses, higher heating values and energy properties. Results showed an increase in carbonisation of samples with increasing HTC severity and an energy densification ratio up to 142% (at 250 °C). Hydrochar obtained at 250 °C was successfully pelletised using a lab scale pelletiser without binders or expensive drying procedures. Energy characterisation (HHV, TGA), ATR-FTIR analysis, fouling index evaluation and pelletisation results suggested that olive mill waste hydrochars could be used as energy dense and mechanical stable bio-fuels. Characterisation of HTC residues in terms of mineral content via induced coupled plasma optical emission spectroscopy (ICP-OES) as well as Total and Dissolved Organic Carbon enabled to evaluate their potential use as soil improvers. Nutrients and polyphenolic compounds in HTC liquid fractions were evaluated for the estimation of their potential use as liquid fertilisers. Results showed that HTC could represent a viable route for the valorisation of olive mill industry waste streams.

Asunto(s)

RESUMEN

Industrial eggshell waste (ES) is classified as an animal by-product not intended to human consumption. For reducing pathogen spreading risk due to soil incorporation of ES, sanitation by composting is a pre-treatment option. This work aims to evaluate eggshell waste recycling in self-heating composting reactors and investigate ES effect on process evolution and end product quality. Potato peel, grass clippings and rice husks were the starting organic materials considered. The incorporation of 30% (w/w) ES in a composting mixture did not affect mixture biodegradability, nor its capacity to reach sanitizing temperatures. After 25 days of composting, ES addition caused a nitrogen loss of about 10 g N kg(-1) of initial volatile solids, thus reducing nitrogen nutritional potential of the finished compost. This study showed that a composting mixture with a significant proportion of ES (30% w/w) may be converted into calcium-rich marketable compost to neutralize soil acidity and/or calcium deficiencies.

Asunto(s)