Efficient production of automotive biofuels; Effektiv produktion av biodrivmedel

The report describes opportunities and consequences associated with biomass polygeneration plants, in particular the role that heat plants (HP) or combined heat and power plants (CHP) in district heating systems can play in the production of automotive biofuels. The aim of the report is to provide a knowledge base to stakeholders to help assess energy and environmental benefits associated with collaborative approaches in planning, constructing and operating energy plants. Several configurations are possible for an energy polygeneration plant, but this report focuses on configurations in which a plant for automotive biofuel production and a district heating system with HPs or CHPs have been integrated in some way in order to achieve added value. The modes of integration are several, e.g.: - Supply of process steam from the CHP to the fuel plant, by which the time of operation for the CHP can be extended; Supply of surplus heat from the fuel plant to the district heating system; Material exchange between the systems, by use of residue streams from the fuel plant as fuel in the HP/CHP; Surplus heat from the fuel plant used for drying of the solid fuel to the HP/CHP or for drying of raw material for pellets production; Co-location providing opportunities for shared infrastructure for raw material handling, service systems, utilities and/or logistics. The report principally addresses integration options of the first three types, but describes briefly also pellets production. The starting point for the analysis of integration options is the description of technologies of interest for the production of automotive biofuels. Commercially available technologies are of prime interest, but also a couple of technologies under development are included in this part of the study. In addition to outlining the process characteristics for these processes, surrounding conditions and system requirements are briefly outlined. The results are summarized in Table S1. Ethanol fermentation, production of fatty acid methyl ester (FAME), pellets production and in some cases treatment with hydrogen gas, catalytic depolymerisation and anaerobic digestion can increase the use of steam and heat from district heating. This new 'offset' for heat can increase operational hours for the CHP. Conversely, biomass gasification produces a greater proportion of the necessary process energy internally and the waste heat produced in the process leads to a lower load for heat production in the CHP. These conclusions are illustrated in the form of a diagram of heat output distribution, both for the hypothetical polygeneration plant of ethanol production and for the hypothetical biomass gasification polygeneration plant with production of synthetic natural gas. The calculations are based on a district heating network where the heat is produced from a biofuel driven CHP (89 MW{sub e}, 173 MW{sub heat} and 230 MW{sub fuel}) and a biofuel driven HP. Since the prerequisites for each specific polygeneration plant are different, the effect of integrations in reality would differ from the results of these calculations--but the results give an overview of the consequences of the choice of energy polygeneration plant. Several interesting combinations in the form of biofuel polygeneration plants are already in operation or in the planning stage. Several conceivable alternatives are: - Ethanol production, anaerobic digestion/feed production, heat and power. - Ethanol production, pellets production, greenhouse, heat and power. - Gasification including fuel production, district heating network and pellets production. - Oilseed rape production, RME production, heat and power. - NExBTL production, refinery, district heating network/heat and power. In most cases the overall efficiency of biofuel production is lower than if biomass is used directly in heat and power production as shown in the system analysis. This is, however, in conflict with the increasing demand for biofuels. A biomass polygeneration plant can level out the difference in efficiency rates and provide electricity, heat and biofuel. A biomass polygeneration plant can give a better total energy utilisation than if production is not integrated. Whether integration is profitable or not is dependant on the value of the different products and the alternative production costs. The energy polygeneration plant concept gives individual plants the opportunity to widen their area of operation. But it is important that the planning process carefully considers a number of factors with regard to local and regional conditions: - The possibility of increasing the demand for heat for existing or new CHPs; Availability of raw materials; The market for products and by-products; The market for waste heat; Possibilities for integration with existing or new plants; The existing infrastructure. A carefully prepared design for energy integration can lead to energy savings although the capital investment may be higher.