Conservation of biodiversity through agricultural activities in the Bulgarian rural areasPROGRASS: An innovative technology for a distributedbioenergy production in grassland-dominated areas. The technical concept originally designed by Professor Scheffer, University of Kassel was designed for moist biomass (i.e. ensilaged energy crops) and aims at an increase in the overall energetic efficiency in the use of energy crops. The basic principle of the technology for integrated electricity and solid fuel production from agricultural biomass, is a separation of silage in a liquid and solid fraction. The resulting press liquid feeds the biogas plant (Fig. 1) with an adapted solid-state digester. Subsequently, the biogas is used in a combined heat and power plant (CHP) to produce electricity and heat. The press cake, which is composed primarily of cellulose and lignin, is dried with the heat from CHP and processed to a solid fuel. The result is a fuel with attributes comparable to those of wood chips, which is suitable for combustion, asification and subsequent processing to e.g.synthetic fuels.Major technical advantages of this process for the use of NATURA grassland biomass are:· Improved fermentation due to a flexible conditioning of the biomass, i.e. ensiling (incipient hydrolysis of structural carbohydrates), mash pre-processing (continued decomposition of structural constituents) and pressing (removal of lignin-cellulose compounds from the fermentable organic part).· Efficient year-round utilisation of waste heat on-site for the drying of press cake.· Advantageous fuel attributes of the press cake due to low mineral content.· Reduced residue volumes to be transported compared to conventional biogas plants as much water is evaporated during biomass processing.· Reduced ash formation and need for disposal in landfill.· Efficient nutrient management through the application of digester residues on the grassland. Gaseous losses during application are expected to be low, as dry matter contents of residues and adherence to plant leaves are low.