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BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

24 2 Biofuels under

24 2 Biofuels under study 2.5.3 Biogas from swine excrements Figure 2-10 shows the life cycle of biogas from swine excrements. The utilisation of the biogas is for energy production (both heat and electricity). The corresponding conventional energy source is natural gas. The left hand side of the diagram shows the various steps of conventional fuel production, whereas the right hand column represents the biofuel chain. In the case of the biofuel production the fermented slurry can be sprayed onto the field as fertiliser as would happen in the case of fossil fuel production. The difference in the environmental impact would in this case be mainly due to transport. Natural gas production Exploitation of natural gas Desulphurisation Transport (Pipeline) Combustion Biogas production Manure transport Fermentation & spraying of fermented manure Combustion Credits Spraying of unfermented manure Figure 2-10 Schematic life cycle comparison of biogas from swine excrements versus energy production from natural gas Details of the life cycle steps Fossil fuel chain: Natural gas is assumed to be extracted in Norway and the Confederation of Independent States respectively and transported from there with shares of 50 % each. It is then processed and transported to the combustion plants. These assumptions are based on expert judgements and are considered to represent the marginal technology. Biofuel chain: Since swine manure is a by-product of food production, the agricultural effects are in this case not taken into account. The reference system in this case is the utilisation of the manure as a fertiliser. Therefore only the additional processes associated with biogas production are considered, such as its fermentation. The spraying of the fermented slurry as manure and associated differences in transportation are also considered. Utilisation: Both fuels are balanced with regard to combustion in a combined heat and power plant on the basis of MJ heat output.

2.6 Novel production line: electricity from hemp 25 2.6 Novel production line: electricity from hemp Figure 2-11 shows the life cycle of power from hemp. The corresponding fossil fuel is hard coal. The utilisation of the hemp is the gasification and combustion of the stems for electricity production. The left hand side of the diagram shows the various steps of conventional fuel production, whereas the middle column represents the biofuel chain. On the right hand side the agricultural reference system is shown which is replaced by the hemp production. In this case the maintenance of fallow land is no longer necessary, as instead hemp is cultivated. These factors are described in some more detail below. Hard coal production Exploitation of hard coal Transport Combustion for electricity generation Hemp production Machines Fuel Fertiliser Seeds Agricultural Production Harvest and drying Chipping Storing and drying Transport to gasification plant Gasification and combustion for electricity generation Figure 2-11 Schematic life cycle comparison of hemp versus hard coal Details of the life cycle steps Credits Fallow maintenance Fossil fuel chain: The coal is exploited in USA, Canada, Australia and S. Africa (in equal shares) and transported to Europe using average distances. In Europe it is combusted for electricity generation. These assumptions are based on expert judgements and are considered to represent the marginal technology. Biofuel chain: The production, application and partial leaching of agrochemicals such as chemical fertiliser and herbicides are taken into account, assuming good agricultural practice. No plant protection measures are carried out. The use of tractors for field preparation, planting, harvest etc. is included. The stems are dried in the field, chipped and transported to the gasification plant where they are stored before gasification and combustion for electricity production. The effects of the disposal of ash are also taken into account. Utilisation: Both fuels are balanced with regard to combustion (with prior gasification in the case of hemp) for electricity generation on the basis of kWh electricity output.

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