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Techno-Economic Analysis of a Straw-Based Biorefinery System for Power, Heat, Pellet and Bioethanol Production
Mälardalen University, School of Sustainable Development of Society and Technology. (Bioenergy group)
Mälardalen University, School of Sustainable Development of Society and Technology.ORCID iD: 0000-0001-9230-1596
Mälardalen University, School of Sustainable Development of Society and Technology.ORCID iD: 0000-0002-3485-5440
School of Chemical Science, Royal Institute of Technology, Stockholm, Sweden.ORCID iD: 0000-0003-0300-0762
(English)In: Energy, ISSN 0360-5442Article in journal (Refereed) Submitted
Abstract [en]

Abstract: Bioethanol is considered an alternative to fossil fuels in the transportation sector. The use of pellets for heating is another efficient way to mitigate greenhouse gas emissions. This paper evaluates the techno-economic performance of a biorefinery system in which an existing combined heat and power plant integrates with the productions of bioethanol and pellets using straw as feedstock. A two-stage acid hydrolysis process for bioethanol production is used, and two different drying technologies are chosen for drying hydrolysis solid residues. A sensitivity analysis on critical parameters, such as the bioethanol selling price and feedstock price, is performed. The bioethanol production cost is also calculated for two cases at the conditions of ten-year and five-year payback time. The results show that the first case is a more feasible economic configuration at present, having an over 30% production cost reduction compared with the conventional cogeneration plants of bioethanol and solid fuel.

Keyword [en]
combined heat and power, pellet, biorefinery, drying, bioethanol, straw.
National Category
Engineering and Technology
Research subject
Biotechnology/Chemical Engineering
URN: urn:nbn:se:mdh:diva-13187OAI: diva2:451936
Available from: 2011-10-27 Created: 2011-10-27 Last updated: 2014-01-07Bibliographically approved
In thesis
1. Retrofitting CHP Plant and Optimization of Regional Energy System
Open this publication in new window or tab >>Retrofitting CHP Plant and Optimization of Regional Energy System
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The use of biomass-based combined heat and power (CHP) plants is considered by the EU administration to be an effective way to increase the use of renewables in the energy system, to reduce greenhouse gas emissions and to alleviate the dependency on imported fossil fuels. At present in Sweden, most of the CHP plants are operated in part-load mode because of variations in heat demand. Further use of the potential heat capacity from CHP plants is an opportunity for integration with other heat-demanding processes. Retrofitting the conventional CHP plants by integration with bioethanol and pellet production processes is considered a feasible and efficient way to improve the plants’ performances.


Modeling and simulation of the CHP plant integrated with feedstock upgrading, bioethanol production and pellet production is performed to analyze the technical and economic feasibility. When integrating with bioethanol production, the exhaust flue gas from the CHP plant is used to dry the hydrolysis solid residues (HSR) instead of direct condensation in the flue gas condenser (FGC). This drying process not only increases the overall energy efficiency (OEE) of the CHP plant but also increases the power output relative to the system using only a FGC. Furthermore, if steam is extracted from the turbine of the CHP plant and if it is used to dry the HSR together with the exhaust flue gas, pellets can be produced and the bioethanol production costs can be reduced by 30% compared with ethanol cogeneration plants.


Three optional pellet production processes integrated with an existing biomass-based CHP plant using different raw materials are studied to determine their annual performance. The option of pellet production integrated with the existing CHP plant using exhaust flue gas and superheated steam for drying allows for a low specific pellet production cost, short payback time and significant CO2 reduction. A common advantage of the three options is a dramatic increase in the total annual power production and a significant CO2 reduction, in spite of a decrease in power efficiency.


The retrofitted biomass-based CHP plants play a crucial role in the present and future regional energy system. The total costs are minimized for the studied energy system by using wastes as energy sources. Analyses of scenarios for the coming decades are performed to describe how to achieve a regional fossil fuel-free energy system. It is possible to achieve the target by upgrading and retrofitting the present energy plants and constructing new ones. The conditions and obstacles have also been presented and discussed through optimizing the locations for proposed new energy plants and planting energy crops.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2011
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 144
annual performance, combined heat and power, drying, ethanol, integration, part-load., årliga prestation, kraftvärme, torkning, etanol, integration, del-last.
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
urn:nbn:se:mdh:diva-13185 (URN)978-91-7485-045-1 (ISBN)
2011-11-28, Kappa, Mälardalen University, Västerås, 13:30 (English)
Available from: 2011-10-27 Created: 2011-10-27 Last updated: 2011-11-09Bibliographically approved

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