Bioremediation of hydrocarbon contaminated soil using local organic materials and earthworms.

Bioremediation technologies have demonstrated significant success on biological quality recovery of hydrocarbon contaminated soils, employing techniques among which composting and vermiremediation stand out. The aim of this study was to evaluate the efficiency of these processes to remediate diesel-contaminated soil, employing local organic materials and earthworms. During the initial composting stage (75 days), the substrate was made up using contaminated soil, lombricompost, rice hulls and wheat stubbles (60:20:15:5% w/w). Diesel concentration in the contaminated substrate was about 5 g kg-1, equivalent to a Total Petroleum Hidrocarbons (TPH) experimental concentration of 3425 ± 50 mg kg-1. During the later vermiremediation stage (60 days), the earthworm species Eisenia fetida and Amynthas morrisi were evaluated for their hydrocarbon degradation capacity. Physicochemical and biological assays were measured at different times of each stage and ecotoxicity assays were performed at the end of the experiments. TPH concentration reduced 10.91% after composting and from 45.2 to 60.81% in the different treatments after vermiremediation. Compared with TPH degradation in the treatment without earthworms (16.05%), results indicate that earthworms, along with indigenous microorganisms, accelerate the remediation process. Vermiremediation treatments did not present phytotoxicity and reflected high substrate maturity values (>80% Germination Index) although toxic effects were observed due to E. fetida and A morrisi exposure to diesel. Vermiremediation was an efficient technology for the recovery of substrate biological quality after diesel contamination in a short period. The addition of organic materials and suitable food sources aided earthworm subsistence, promoted the decontamination process and improved the substrate quality for future productive applications.

Poultry litter stabilization by two-stage composting-vermicomposting process: Environmental, energetic and economic performance.

Poultry litter (PL) is a heterogeneous mixture that contains bedding materials, antibiotics, dead skin, feed scraps, water, feathers and the resulting microbiota from poultry production cycle. Although its treatment does not receive attention, it is an important organic resource generated in the north-east region of Santa Fe Province since animal primary production is one of the main economic activities there and in the whole country. The objective of this work was to analyse the economic and energy aspects and the environmental impact of two scenarios corresponding to treat two different mixtures of organic wastes: Eucalyptus sp. sawdust (ES), rice hulls (RH) and PL. PL was considered in two different volume proportions: 1RH:3 PL for scenario 1 and 0.5RH:1 ES:2 PL for scenario 2. The two-stage combined system of composting + vermicomposting was applied to both scenarios and compared; on one hand, the current regulated practice for waste final deposition (landfill) and on the other hand, a base line scenario, which describes the current situation, where the raw material is transported and spread over the field as fertilizer without previous stabilization. The scenario construction was based according to on-site data, lab-scale experiments previously published and software databases. The environmental study was carried out with life cycle assessment; and the energy study, using cumulative energy demand methodology and the energy balance. Based on the results, it was possible to affirm the importance of the integrated agricultural waste treatment to address environmental benefits, especially related to the base line scenario. Furthermore, there were no significant differences between the two proposed scenarios. Economic and environmental results were contradictory when no long-term socio-economic consequences are considered. Combined composting and vermicomposting strategy reduce the organic matter and nutrients content not only to avoid discharges into the environment, but also to replace the fossil fuels consumption during unsustainable techniques as sanitary landfill, producing improved substrates for agricultural use.

Microparticles based on ionic and organosolv lignins for the controlled release of atrazine.

Lignins are natural polymers of the lignocellulosic biomass. Nowadays, there is a growing interest in developing value-added products based on lignins due to their renewability, low cost and abundance. In this work, lignin microspheres from organosolv and ionic isolation processes were prepared for the controlled release of atrazine. Microspheres were prepared by the solvent extraction/evaporation technique. The controlled release of atrazine from organosolv and ionic lignins microparticles was studied in water. Mobility experiments were performed in an agricultural soil from Argentina. The results showed that microparticles prepared using dichloromethane as the dispersed phase were spherical, while lignins dispersed in ethyl acetate produce irregular microparticles. Organosolv lignin microparticles presented higher encapsulation efficiency for all herbicide loads. About 98% and 95% of atrazine was released in 24 and 48 h approximately from organosolv and ionic lignin microparticles, respectively. The release profiles of atrazine from both lignin microparticles were not affected by the herbicide load. Atrazine mobility experiments in soil showed that about 80% of free atrazine was leached in 37 days, while 65.0% and 59.7% of the herbicide was leached from ionic and organosolv lignin microparticles, respectively. Thus, atrazine-loaded microparticles could reduce leaching compared to a commercial formulation of free atrazine.