1,721,078 research outputs found
Treatment and enhancement of digestate liquid fraction from animal waste and biomasses anaerobic digestion.
No full textGreenhouse gas emissions from constructed wetlands and agronomic management of urban wastewater and digestate
Full text linkThe awareness of and interest in human activities environmental impact, in the framework of the ongoing climate change, has imposed the need to evaluate waste disposal in terms of greenhouse gases emission, in addition to the productive processes.
Constructed wetlands (CW) are a low environmental impact technology to treat wastewater with little or no energy input, increasingly used as a natural-like treatment system that is applicable in urban and/or production contexts. CW systems reproduce the physical, chemical and biological self-purification process of the soil-plant-microorganism systems that characterize aquatic habitats and natural wetlands.
Depuration processes, largely operated in these systems by rhizosphere microorganisms that contribute to the reduction of organic and nitrogen wastewater load, determine gaseous compounds release into the atmosphere, some of which act as greenhouse gases, in particular carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The evaluation of greenhouse gases (GHG) emission from CWs, influenced by CW and wastewater types and vegetation and species presence in the beds, has been investigated for about 15 years in CWs in central-northern European Countries, while few experiments, and mostly at laboratory scale, have been conducted in the Mediterranean Basin, and none in Italian CWs.
With this in mind, the main aim of this PhD thesis was to evaluate the role of the main components used in the construction of CWs on GHGs emission in the more widespread (full scale or pilot plants) Italian CW systems. For this purpose in two different Italian bioclimatic contexts, Sicily and Veneto, two CW sites were selected that treated urban wastewater and digestate fluid fraction respectively. Particular attention was paid in the research to the role of vegetation on CWs GHGs emission studying different species (Arundo donax L., Phragmites australis (Cav.) Trin. Ex Steud., Cyperus papyrus L., Chrysopogon zizanioides (L.) Roberty and Mischantus x giganteus Greef et Deu.).
The results obtained in the Sicilian context showed a species specific effect on CO2 and CH4 emissions. Significantly higher CO2 emissions (median value 16.5 g m-2 d-1) were monitored in the beds vegetated with A. donax, M. giganteus and P. australis, than those vegetated with C. papyrus and C. zizanioides and the unvegetated bed (median value 5.2 g m-2 d-1). The M. giganteus presence in the bed and the absence of vegetation both determined significantly higher CH4 emissions than those monitored with C. papyrus. At the end of the two trial years all vegetated beds showed a CO2(eq) positive balance with better values calculated for A. donax (21.4 kg CO2(eq) m-2), whereas the unvegetated bed showed a net emission into the atmosphere of 5.5 kg CO2(eq) m-2.
The CW system in Veneto that treated digestate fluid fraction coming from an anaerobic digester for biogas production fed with livestock slurry and energy crops biomass, showed no significant depuration performance differences between P. australis and A. donax vegetation, but the latter did not regrow in the second year, thus determining a significant increase in CH4 emissions.
The digestate fluid fraction, characterized by a high organic matter and nitrogen content, can also be considered as an agronomic resource in a region where land availability is not a limiting factor and considering the limit on its spreading imposed by Directive 91/676/EEC of 12 December 1991. In fact, the intensive mineral fertilization and deep soil tillage that were typical of Italian agriculture in the second half of last century, have caused some problems in the agro-ecosystems, including the loss of organic carbon. The addition of soil organic matter and the use of agricultural techniques to directly or indirectly reduce CO2 emissions, may be a response to soil organic carbon loss with a positive effect on the environment.
Taking this into account, an additional investigation topic of the PhD research has been to evaluate the effect exerted by the digestate fluid fraction application on agricultural soil CO2 emissions by: 1) soil texture (sandy loam vs. clay loam) and preparatory tillage (plowing vs ripping) after splash-plate spreading; 2) the digestate fluid fraction injection depth into the soil (10, 25 and 35 cm).
The results have shown a CO2 emission peak one hour after digestate distribution and emission values reaching those of un-amended soils after 3 days, using both application methods. Considering the splash-plate technique in the two weeks following spreading, significantly higher CO2 emissions were found in sandy loam than clay loam soil, the preparatory soil tillage showed no significant effect. Digestate fluid fraction soil injection determined after one hour of application, an opposite trend with injection depth, with lower emissions at increasing depth
Lolium multiflorum Lam. cvs germination under simulated olive mill wastewater salinity and pH stress
No full textThe agronomic use of olive mill wastewaters (OMWs) is limited by some constraints, such as high salinity, acidity, and phenolic compounds that exert phytotoxic and antimicrobial effects. Many researches have been focused on OMW polyphenol effects on germination, but only few on the combined effects of salinity and acidity. In this paper, on Lolium multiflorum Lam., the effects on germination of pH and osmotic potentials similar or higher to those found in OMWs have been investigated. The studied salinity and pH levels did not affect final germination of L. multiflorum, but in some cultivars they significantly enhanced T50 and consequently reduced initial root growth. Thus, in this species moderately tolerant to salinity, the reduction of germination determined by OMWs cannot be attributed to the osmotic stress and/or to the low pH, but mainly to polyphenols. This research emphasizes the possibility of obtaining good crop establishments after spreading OMWs on soil, choosing herbaceous species tolerant to salinity once polyphenols have been inactivated
Digestato su mais ceroso: effetti su emissioni di CO2 e resa.
No full textL’impiego della frazione liquida del digestato per la concimazione del mais ha effetti positivi sulle rese, ma per limitare l’emissione di CO2 è necessario rispettare alcune regole agronomiche, tra cui evitare la distribuzione superficiale su suoli con tessitura franco-sabbiosa
CO2 emissions and maize biomass production using digestate liquid fraction in two soil texture types
No full textThe aim of this work was to evaluate the effects of soil texture and primary tillage type on soil CO2 emission and maize biomass production after digestate liquid fraction (DLF) spreading. The study was conducted in 2014 in two open fields at Terrasa Padovana (farm 1) and Bovolenta (farm 2) in the Veneto Region of Italy. Soil CO2 emission after digestate spreading was evaluated by comparing the effect of soil texture (sandy loam vs. clay loam) at farm 1 and the effect of long-term primary tillage management (> 10 years) (ripping vs. plowing) in clay loam soil at farm 2. Unamended soil was considered the control at both farms. DLF was supplied before maize (Zea mays L.) sowing at a dose equal to 170 kg total nitrogen ha(-1) using a splash-plate technique. DLF spreading determined a CO2 emission peak 1 h after spreading at both farms, with median emission values of 8.93 and 4.35 g m(-2) h(-1), respectively, from the sandy loam and clay loam soils at farm 1. At farm 2, primary tillage type did not exert a significant effect on CO2 emission peak, with a median value of 5.85 g m(-2) h(-1). About three days after DLF distribution, soil CO2 fluxes were less than 1 g m(-2) h(-1). The first soil harrowing and the first rainfall event after spreading determined significantly higher CO2 emissions from amended plots than from unamended plots for a few hours. At farm 1, soil CO2 emission during the maize growing season was significantly higher in the amended plots (+ 1.7 times) than in the unamended plots, which showed a median emission value of 0.29 g m(-2) h(-1); soil texture and tillage exerted no significant influence. Maize yield at dough stage was not significantly influenced by DLF at farm 1, with 22.7 +/- 1.6 Mg ha(-1) and 18.7 +/- 2.8 Mg ha(-1) in the clay loam and sandy loam soils, respectively. At farm 2, the distribution of DLF increased maize biomass production by +17% with respect to the unamended treatment that produced 18.0 +/- 2.4 Mg ha(-1). Although the results reported in this article concern data from only one year, and further long-term experiments are needed to confirm our findings, they indicate that CO2 emissions after digestate distribution are lower in a clay loam soil than in a sandy loam soil and are not affected by primary tillage type
Composition and potential second generation ethanol production of 14 species suitable for phytoremediation.
No full textBiomass production and soil organic carbon accumulation in a free water surface constructed wetland treating agricultural wastewater in North Eastern Italy
No full textFree water surface constructed wetlands (FWSs) play an important role in wastewater pollutants removal and, at the same time, vegetated wetlands can act as carbon sinks. In this study we measured biomass production and soil carbon content variations over five years in a FWS with fluctuating hydroperiod treating agricultural drainage water to evaluate its role in the carbon dioxide cycle. During the study flooding occurred with a yearly average of 28 days. Annual dry matter production, from 2008 to 2011, ranged between 50 and 60 Mg ha−1. The highest C storage was concentrated in the belowground biomass. 83% of total belowground biomass was measured in the 0–20 cm soil layer. During the 2007–2012 period the organic carbon (OC) concentration in the 0–20 cm soil layer slightly increased from 12.3 to 13.1 g kg−1 and bulk density from 1.38 to 1.66 Mg m−3. In the 20–50 cm soil layer, monitored only in 2009 and 2012, OC concentration was lower and steady (8.8 g kg−1). The total soil C accumulation in the five years was 110.73 Mg ha−1 of equivalent CO2(eq). Given the positive C balance FWSs can be considered a CO2 sink
Effects of mycorrhization on biomass plant species fertilized with digestate liquid fraction.
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