F. Richter

Integrated generation of solid fuel and biogas from green cut material from landscape conservation and private households

Green cut material is a potential source of renewable energy which is not fully exploited through conventional energy recovery systems. A new energy conversion process, the integrated generation of solid fuel and biogas from biomass (IFBB), which includes mechanical separation after hydro-thermal conditioning, was investigated. Ash softening temperature and lower heating value of the solid fuel were increased through the IFFB process in comparison to the untreated raw material. The net energy yield of IFBB at 40 °C conditioning temperature ranged between 1.96 and 2.85 kWh kg(-1) dry matter (DM) and for the direct combustion between 1.75 and 2.65 kWh kg(-1) DM. Conversion efficiencies for the IFBB system were 0.42-0.68 and for direct combustion 0.42-0.63. The IFBB system produces storable energy from material which is nowadays not used for energy conversion.

Influence of sward maturity and pre-conditioning temperature on the energy production from grass silage through the integrated generation of solid fuel and biogas from biomass (IFBB): 1. The fate of mineral compounds

The IFBB process, which separates biomass into a press fluid for biogas production and a press cake for combustion, is aimed at converting low-input high-diversity grasslands into energy, which is problematic with conventional conversion techniques. Herbage from a lowland hay meadow (Arrhenaterion) was sampled on eight dates between 24 April and 21 June 2007. Silage from each date was processed in six treatments without and with hydrothermal conditioning at different temperatures. The impact on mass flows of plant compounds and on elemental concentrations in the press cake was investigated. Elements detrimental for combustion were significantly reduced in the press cake compared to the silage. Mass flows and elemental concentrations in the press cake were strongly influenced by conditioning temperature as well as concentration of neutral detergent fiber and dry matter in the silage (R(2) from 0.70 to 0.99). Press cakes of late sampling dates were considered best suitable for combustion.

Influence of sward maturity and pre-conditioning temperature on the energy production from grass silage through the integrated generation of solid fuel and biogas from biomass (IFBB): 2. Properties of energy carriers and energy yield.

In order to determine influencing parameters on energy production of the IFBB process, herbage from a lowland hay meadow (Arrhenaterion) was sampled and ensiled at eight dates between 27 April and 21 June 2007. The silage from each date was processed in six IFBB treatments with and without hydrothermal conditioning at different temperatures. Methane yields and higher heating values were determined and an energy balance was calculated with whole-crop digestion (WCD) of the silage as reference system. Maximum net energy yields were 10.2 MWh ha(-1) for the IFBB treatment without hydrothermal conditioning and 9.0 MWh ha(-1) for the treatment with hydrothermal conditioning at 50 °C. WCD achieved a maximum net energy yield of 3.7 MWh ha(-1). Energy conversion efficiency ranged from 0.24 to 0.54 and was predicted with high accuracy by temperature of hydrothermal conditioning as well as concentration of neutral detergent fibre and dry matter in the silage (R(2)=0.90).