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Orzi V.,University of Milan | Scaglia B.,University of Milan | Lonati S.,University of Milan | Riva C.,University of Milan | And 3 more authors.
Science of the Total Environment | Year: 2015

Mesophilic anaerobic digestion (MAD) produces renewable energy, but it also plays a role in reducing the impact of digestates, both by reducing odor and pathogen content. Ten full-scale biogas plants characterized by different plant designs (e.g. single digesters, parallel or serial digesters), plant powers (ranging from 180 to 999kWe), hydraulic retention time (HRT) (ranging between 20 to 70days) and feed mixes were monitored and odors and pathogens were observed in both ingestates and digestates. Results obtained indicated that MAD reduced odors (OU) from, on average, OUingestate=99,106±149,173OUm-2h-1 (n=15) to OUdigestate=1106±771OUm-2h-1 (n=15).Pathogens were also reduced during MAD both because of ammonia production during the process and competition for substrate between pathogens and indigenous microflora, i.e. Enterobacteriaceae from 6.85*103±1.8*101 to 1.82*101±3.82*101; fecal Coliform from 1.82*104±9.09 to 2.45*101±3.8*101; Escherichia coli from 8.72*103±2.4*101 to 1.8*101±2.94*101; Clostridium perfringens from 6.4*104±7.7 to 5.2*103±8.1 (all data are expressed as CFUg-1ww).Plants showed different abilities to reduce pathogen indicators, depending on the pH value and toxic ammonia content. © 2015 Elsevier B.V.


PubMed | DG Agricoltura, Instituto Zooprofilattico Sperimentale della Lombardia e dellEmilia Romagna and University of Milan
Type: | Journal: The Science of the total environment | Year: 2015

Mesophilic anaerobic digestion (MAD) produces renewable energy, but it also plays a role in reducing the impact of digestates, both by reducing odor and pathogen content. Ten full-scale biogas plants characterized by different plant designs (e.g. single digesters, parallel or serial digesters), plant powers (ranging from 180 to 999 kWe), hydraulic retention time (HRT) (ranging between 20 to 70 days) and feed mixes were monitored and odors and pathogens were observed in both ingestates and digestates. Results obtained indicated that MAD reduced odors (OU) from, on average, OUingestate=99,106149,173 OU m(-2) h(-1) (n=15) to OU digestate=1106771 OU m(-2) h(-1) (n=15). Pathogens were also reduced during MAD both because of ammonia production during the process and competition for substrate between pathogens and indigenous microflora, i.e. Enterobacteriaceae from 6.8510(3)1.810(1) to 1.8210(1)3.8210(1); fecal Coliform from 1.8210(4)9.09 to 2.4510(1)3.810(1); Escherichia coli from 8.7210(3)2.410(1) to 1.810(1)2.9410(1); Clostridium perfringens from 6.410(4)7.7 to 5.210(3)8.1 (all data are expressed as CFU g(-1) ww). Plants showed different abilities to reduce pathogen indicators, depending on the pH value and toxic ammonia content.


Riva C.,University of Milan | Orzi V.,University of Milan | Carozzi M.,University of Milan | Acutis M.,University of Milan | And 5 more authors.
Science of the Total Environment | Year: 2016

Anaerobic digestion produces a biologically stable and high-value fertilizer product, the digestate, which can be used as an alternative to mineral fertilizers on crops. However, misuse of digestate can lead to annoyance for the public (odours) and to environmental problems such as nitrate leaching and ammonia emissions into the air. Full field experimental data are needed to support the use of digestate in agriculture, promoting its correct management. In this work, short-term experiments were performed to substitute mineral N fertilizers (urea) with digestate and products derived from it to the crop silage maize. Digestate and the liquid fraction of digestate were applied to soil at pre-sowing and as topdressing fertilizers in comparison with urea, both by surface application and subsurface injection during the cropping seasons 2012 and 2013. After each fertilizer application, both odours and ammonia emissions were measured, giving data about digestate and derived products' impacts.The AD products could substitute for urea without reducing crop yields, apart from the surface application of AD-derived fertilizers. Digestate and derived products, because of high biological stability acquired during the AD, had greatly reduced olfactometry impact, above all when they were injected into soils (82-88% less odours than the untreated biomass, i.e. cattle slurry). Ammonia emission data indicated, as expected, that the correct use of digestate and derived products required their injection into the soil avoiding, ammonia volatilization into the air and preserving fertilizer value. Sub-surface injection allowed ammonia emissions to be reduced by 69% and 77% compared with surface application during the 2012 and 2013 campaigns. © 2015 Elsevier B.V.


PubMed | DG Agricoltura and University of Milan
Type: | Journal: The Science of the total environment | Year: 2016

Anaerobic digestion produces a biologically stable and high-value fertilizer product, the digestate, which can be used as an alternative to mineral fertilizers on crops. However, misuse of digestate can lead to annoyance for the public (odours) and to environmental problems such as nitrate leaching and ammonia emissions into the air. Full field experimental data are needed to support the use of digestate in agriculture, promoting its correct management. In this work, short-term experiments were performed to substitute mineral N fertilizers (urea) with digestate and products derived from it to the crop silage maize. Digestate and the liquid fraction of digestate were applied to soil at pre-sowing and as topdressing fertilizers in comparison with urea, both by surface application and subsurface injection during the cropping seasons 2012 and 2013. After each fertilizer application, both odours and ammonia emissions were measured, giving data about digestate and derived products impacts. The AD products could substitute for urea without reducing crop yields, apart from the surface application of AD-derived fertilizers. Digestate and derived products, because of high biological stability acquired during the AD, had greatly reduced olfactometry impact, above all when they were injected into soils (82-88% less odours than the untreated biomass, i.e. cattle slurry). Ammonia emission data indicated, as expected, that the correct use of digestate and derived products required their injection into the soil avoiding, ammonia volatilization into the air and preserving fertilizer value. Sub-surface injection allowed ammonia emissions to be reduced by 69% and 77% compared with surface application during the 2012 and 2013 campaigns.

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