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Fertilisation with digested manure from biogas plants : a methodological proposal at the district scale
No full textThe hypothesis described in this paper is that the manures obtained as a
by-product from large anaerobic digestion (AD) plants are best managed
at the district scale. We envisaged a management scheme for digested
manures that maximises agronomic, environmental, and economic benefits.
We also described the research steps required to put it into practice.
In our hypothesis, the digestion plant and the machinery for manure
distribution are managed by a central entity. A nutrient management
plan is set up using the information contained in a geographic information
system incorporating all relevant information about cropping systems
and animal production systems in the district. Using manure nitrogen
concentrations estimated with near infrared spectroscopy (NIRS) sensors, the results of the plan are translated into amounts of manure to be distributed. Field application of manure (with soil incorporation) is
then carried out using machinery equipped with sensors that update the
information system with data about the operation carried out. We finally
describe the operational, agronomic, economic, and environmental
advantages of this management scheme
The role of biological processes in reducing both odor impact and pathogen content during mesophilic anaerobic digestion
No full textMesophilic 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
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