1,721,050 research outputs found
Long-term effect of sewage sludge application on soil humic acids
No full textSewage sludges are used in agriculture because they act as a fertilizer. Long-term studies are needed to evaluate the effect of sewage sludge on soil properties by paying particular attention to the soil organic matter. Soil plots were amended for 10 years with 1 Mg dry matter ha(-1) year(-1) of sewage sludge. Chemical parameters such as total organic carbon (TOC), N, C/N ratio and CEC were determined when this period ended. Moreover, TOC was fractionated into humified and non-humified fractions. Humic acids (HA) were isolated and studied by elemental analysis, DRIFT, H-1 NMR and CPMAS, C-13 NMR spectroscopies. At the end of the tests, compared to the control soil, the sludge-amended soil did not exhibit change in total organic C and related humified fractions. However, the HA composition of the soil treated with sludge had developed an HA composition closer to that of the HA-sludge as a result of the enrichment of recalcitrant fractions contained in the sludge. (C) 2005 Elsevier Ltd. All rights reserved
Biostabilization of municipal solid waste
No full textA mechanical-biological process for municipal solid waste (MSW) treatment was monitored for one year. Mechanical pre-treatment provided two fractions. The oversize fraction (Ø>50 mm) (yield of 600 gkg-1ww) (46 Mgday-1) was used for refuse derived fuel production, after undergoing a mechanical refining processes, because of low moisture content (200-250 gkg-1) and high calorific value (2500-2800 kcalkgww -1). The undersize fraction (Ø<50 mm) (yield 400 gkg -1ww) (30 Mgday-1) contained about 800 gkg-1 of the MSW organic matter. This fraction was biologically treated using an aerobic process with an organic waste fraction from separate collection (77 Mgday -1) and recycled stabilized material (62 Mgday-1) obtained from end-product sieve (Ø<20 mm) used as bulking agent. A retention time of three weeks was sufficient to obtain stabilized products in agreement with up-dated rules of the Lombardy Region (North Italy) regarding biostabilization and composting processes. Dynamic Respiration Index (DRI), such as required by both Lombardy Region rules and suggested by the European Community, was chosen in preference to other indices in order to assess the degree of biological stability of the end products. A mean DRI value of 1164 mg O2 kgSV-1h-1 was obtained and is in agreement with the proposed limit of 1000±200 mg O2 kgSV -1h-1. Self-heating test, potential biogas production and fermentable volatile solids were also used as parameters to describe the potential impact of treated waste, providing further useful information. Nevertheless, all of these methods revealed analytical or interpretative limits. A complete mass balance of the biological treatment section showed that, from a net input of 107 Mgday-1, only 250 gkg-1 (27 Mgday -1) of the waste needed to be landfilled, with 750 gkg-1 (80 Mgday-1) being lost as CO2 and H2O
Effect of compost application rate on carbon degradation and retention in soils
Full text linkWe investigated the effect of a single compost application at two rates (50 and 85 Mg ha-1) on carbon (C) degradation and retention in an agricultural soil cropped with maize after 150 d. We used both C mass balance and soil respiration data to trace the fate of compost C. Our results indicated that compost C accumulated in the soil after 150 d was 4.24 Mg ha-1 and 6.82 Mg C ha-1 for 50 and 85 Mg ha-1 compost rate, respectively. Compost C was sequestered at the rate of 623 and 617 g C kg-1 compost TOC for 50 and 85 Mg ha-1 compost dose, respectively. These results point to a linear response between dose of application and both C degradation and retention. The amount of C sequestered was similar to the total recalcitrant C content of compost, which was 586 g C kg-1 compost TOC, indicating that, probably, during the short experiment, the labile C pool of compost (414 g C kg-1 of compost TOC) was completely degraded. Soil respiration measured at different times during the crop growth cycle was stable for soils amended with compost (CO2 flux of 0.96 ± 0.11 g CO2 m-2 h-1 and 1.07 ± 0.10 g CO2 m-2 h-1, respectively, for 50 and 85 Mg ha-1), whereas it increased in the control. The CO2 flux due to compost degradation only, though not statistically significant, was always greatest for the highest compost doses applied (0.22 ± 0.40 g CO2 m-2 h-1 and 0.33 ± 0.25 g CO2 m-2 h-1 for the 50 and 85 Mg ha-1 compost dose, respectively). This seems to confirm the highest C degradation for the 85 Mg ha-1 compost dose as a consequence of the presence of more labile C. Unlike other studies, the results show a slight increase in the fraction of carbon retained with the increase in compost application rate. This could be due to the highly stable state of the compost prior to application, although it could also be due to sampling uncertainty. Further investigations are needed to better explain how the compost application rate affects carbon sequestration, and how characterization into labile and recalcitrant C can predict the amount of C sequestered in the soil
Effects of biodrying process on municipal solid waste properties
No full textIn this paper, the effect of biodrying process on municipal solid waste (MSW) properties was studied. The results obtained indicated that after 14d, biodrying reduced the water content of waste, allowing the production of biodried waste with a net heating value (NHV) of 16,779±2,074kJkg -1 wet weight, i.e. 41% higher than that of untreated waste. The low moisture content of the biodried material reduced, also, the potential impacts of the waste, i.e. potential self-ignition and potential odors production. Low waste impacts suggest to landfill the biodried material obtaining energy via biogas production by waste re-moistening, i.e. bioreactor. Nevertheless, results of this work indicate that biodrying process because of the partial degradation of the organic fraction contained in the waste (losses of 290gkg -1 VS), reduced of about 28% the total producible biogas
The effects of short-term compost application on soil chemical properties and plant nutritional status
No full textCompost may improve the soil quality and contribute to C sequestration. The short-term effects of compost application on soil properties of soil cropped with maize are reported here. Soil plots to which mature compost was added (at 50 Mg ha-1 and 85 Mg ha-1) were analyzed for total organic carbon (TOC), nutrients, heavy metals and other soil properties. In addition, maize plants were weighed at the end of the trial and analyzed for carbon (C), nitrogen (N), phosphorus (P) and heavy metals. The results demonstrate that soil amended with compost has an increased TOC content. The increase was proportional to the amount of compost used. At the highest dose used, compost also increased soil N and P content and the pH. Moreover, after compost application, the total heavy metal contents in soils did not increase. There was no difference between the maize yield from compost treated plots and the control plots. However, maize grains were found to be C, N and P enriched due to the increased nutrient status of the amended soil. In conclusion, the addition of mature compost improves soil properties by increasing the soil TOC content and this depends on the characteristics and the amount of compost used
Cr(VI) reduction capability of humic acid extracted from the organic component of municipal solid waste
No full textThe capacity of humic acid extracted from organic waste (HAw) to reduce Cr(VI) was tested at pH 2.5, 4 and 6 and compared with coal-derived humic acid (HAc). HAw was more effective than HAc in reducing Cr(VI). The kinetics of Cr(VI) reductions depended strongly on pH. The calculation of the apparent rate coefficients indicated that HAw was more efficient at reducing Cr(VI) than HAc, but was also more efficient than HAs from soil and peat. The reduction capability of HAs depends on the type of functional groups (i.e., thiols and phenols) present, rather than the free radicals. HAw was more efficient at reducing Cr(VI) than HAc because more reactive phenols were present, i.e., methoxy- and methyl-phenols
Nitrogen mineralization from digestate in comparison to sewage sludge, compost and urea in a laboratory incubated soil experiment
Full text linkThis paper evaluated, in a laboratory incubated soil, the properties of digestate as a nitrogen fertilizer in comparison with sewage sludge, compost and urea, this last as a typical mineral fertilizer. The incubation period lasted for 90 d and during this time, pH, CO2 and NO3 - evolution were measured. The maximum concentration of nitrate was reached in the incubated microcosm fertilized by urea (133 mg kg-1 after 62 d), and that of digestate was very similar (113 mg kg-1). Soil treated with compost showed a slower nitrate evolution. A significantly negative correlation was detected between cumulative nitrogen nitrified at the end of the trial, and the values of the C:N ratio of the biomasses used (compost, sludge and digestate) (mg kg-1 N - NO3 - vs. C:N, r=-0.94, n = 3, p < 0.05), and between the alkyl-C content at the end of the experiment (mg kg-1 N - NO3 - vs. alkyl-C, r = -0.95, n = 3, p < 0.05). As expected, pH decreases and soil respiration (CO2 evolution) were also well correlated with the content of nitrate. Considering that about 90% of the nitrogen content in the digestate is short acting, the results obtained indicate that the nitrogen rate of mineralization in digestate is very similar to that of urea, confirming that digestate could replace traditional mineral fertilizers
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