Fertilisation with digested manure from biogas plants : a methodological proposal at the district scale

The 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.