Biological treatment by activated slurry and composting of manure on straw : a farm survey

A survey carried out in 15 stations using biological treatment by activated slurry and three units for the composting of manure on straw provided data on working time, treatment cost, difficulties encountered by farmers and by-product management methods. The volume of manure processed was 23.5 and 8.3 m3/day. Station supervision and by-product management required 2.1 min of work per cubic metre of manure treated by activated slurry, against 6.6 min/m3 for composting. Running costs were 2.9 and 5.2 e/m3 for an average initial investment of 342 and 194 ke, respectively. However, this survey shows wide disparities in working time and cost within each process. The derived by-products are generally characterised by a high content of phosphorus (biological slurry, compost) or potassium (supernatant). Generally, they seem to be spread at excessive levels in terms of crop export potential.