The modern concept of “biorefinery” is dominantly based on chemical pulp mills to create more value than cellulose pulp fibres, and energy from the dissolved lignins and hemicelluloses. This concept is characterized by the conversion of biomass into various bio-based products. It includes thermochemical processes such as gasification and fast pyrolysis. In thermo-mechanical pulp (TMP) mills, the feedstock available to the gasification-based biorefinery is significant, including logging residues, bark, fibre material rejects, bio-sludges and other available fuels such as peat, recycled wood and paper products. On the other hand, mechanical pulping processes consume a great amount of electricity, which may account for up to 40% of the total pulp production cost. The huge amount of purchased electricity can be compensated for by self-production of electricity from gasification, or the involved cost can be compensated for by extra revenue from bio-transport fuel production. This work is to study co-production of bio-automotive fuels, bio-power, and steam via gasification of the waste biomass streams in the context of the mechanical pulp industry. Ethanol and substitute natural gas (SNG) are chosen to be the bio-transport fuels in the study. The production processes of biomass-to-ethanol, SNG, together with heat and power, are simulated with Aspen Plus. Based on the model, the techno-economic analysis is made to evaluate the profitability of bio-transport fuel production when the process is integrated into a TMP mill.The mathematical modelling starts from biomass gasification. Dual fluidized bed gasifier (DFBG) is chosen for syngas production. From the model, the yield and composition of the syngas and the contents of tar and char can be calculated. The model has been evaluated against the experimental results measured on a 150 KWth Mid Sweden University (MIUN) DFBG. As a reasonable result, the tar content in the syngas decreases with the gasification temperature and the steam to biomass (S/B) ratio. The biomass moisture content is a key parameter for a DFBG to be operated and maintained at a high gasification temperature. The model suggests that it is difficult to keep the gasification temperature above 850 ℃ when the biomass moisture content is higher than 15.0 wt.%. Thus, a certain amount of biomass or product gas needs to be added in the combustor to provide sufficient heat for biomass devolatilization and steam reforming.For ethanol production, a stand-alone thermo-chemical process is designed and simulated. The techno-economic assessment is made in terms of ethanol yield, synthesis selectivity, carbon and CO conversion efficiencies, and ethanol production cost. The calculated results show that major contributions to the production cost are from biomass feedstock and syngas cleaning. A biomass-to-ethanol plant should be built over 200 MW.In TMP mills, wood and biomass residues are commonly utilized for electricity and steam production through an associated CHP plant. This CHP plant is here designed to be replaced by a biomass-integrated gasification combined cycle (BIGCC) plant or a biomass-to-SNG (BtSNG) plant including an associated heat & power centre. Implementing BIGCC/BtSNG in a mechanical pulp production line might improve the profitability of a TMP mill and also help to commercialize the BIGCC/BtSNG technologies by taking into account of some key issues such as, biomass availability, heat utilization etc.. In this work, the mathematical models of TMP+BIGCC and TMP+BtSNG are respectively built up to study three cases: 1) scaling of the TMP+BtSNG mill (or adding more forest biomass logging residues in the gasifier for TMP+BIGCC); 2) adding the reject fibres in the gasifier; 3) decreasing the TMP SEC by up to 50%.The profitability from the TMP+BtSNG mill is analyzed in comparison with the TMP+BIGCC mill. As a major conclusion, the scale of the TMP+BIGCC/BtSNG mill, the prices of electricity and SNG are three strong factors for the implementation of BIGCC/BtSNG in a TMP mill. A BtSNG plant associated to a TMP mill should be built in a scale above 100 MW in biomass thermal input. Comparing to the case of TMP+BIGCC, the NR and IRR of TMP+BtSNG are much lower. Political instruments to support commercialization of bio-transport fuel are necessary. / Gasification-based Biorefinery for Mechanical Pulp Mills

The modern concept of "biorefinery" is dominantly based on chemical pulp mills to create more value than cellulose pulp fibres, and energy from the dissolved lignins and hemicelluloses. This concept is characterized by the conversion of biomass into various biobased products. It includes thermochemical processes such as gasification and fast pyrolysis. In mechanical pulp mills, the feedstock available to the gasification-based biorefinery is significant, including logging residues, bark, fibre material rejects, biosludges and other available fuels such as peat, recycled wood, and paper products. This work is to study co-production of bio-automotive fuels, biopower, and steam via gasification in the context of the mechanical pulp industry.   Biomass gasification with steam in a dual-fluidized bed gasifier (DFBG) was simulated with ASPEN Plus. From the model, the yield and composition of the syngas and the contents of tar and char can be calculated. The model has been evaluated against the experimental results measured on a 150 KWth Mid Sweden University (MIUN) DFBG. The model predicts that the content of char transferred from the gasifier to the combustor decreases from 22.5 wt.% of the dry and ash-free biomass at gasification temperature 750 ℃ to 11.5 wt.% at 950 ℃, but is insensitive to the mass ratio of steam to biomass (S/B). The H2 concentration is higher than that of CO under normal DFBG operating conditions, but they will change positions when the gasification temperature is too high above about 950 ℃, or the S/B ratio is too far below about 0.15. The biomass moisture content is a key parameter for a DFBG to be operated and maintained at a high gasification temperature. The model suggests that it is difficult to keep the gasification temperature above 850 ℃ when the biomass moisture content is higher than 15.0 wt.%. Thus, a certain amount of biomass needs to be added in the combustor to provide sufficient heat for biomass devolatilization and steam reforming. Tar content in the syngas can also be predicted from the model, which shows a decreasing trend of the tar with the gasification temperature and the S/B ratio. The tar content in the syngas decreases significantly with gasification residence time which is a key parameter.   Mechanical pulping processes, as Thermomechanical pulp (TMP), Groundwood (SGW and PGW), and Chemithermomechanical pulp (CTMP) processes have very high wood-to-pulp yields. Producing pulp products by means of these processes is a prerequisite for the production of printing paper and paperboard products due especially to their important functional properties such as printability and stiffness. However, mechanical pulping processes consume a great amount of electricity, which may account for up to 40% of the total pulp production cost. In mechanical pulping mills, wood (biomass) residues are commonly utilized for electricity production through an associated combined heat and power (CHP) plant. This techno-economic evaluation deals with the possibility of utilizing a biomass integrated gasification combined cycle (BIGCC) plant in place of the CHP plant. Integration of a BIGCC plant into a mechanical pulp production line might greatly improve the overall energy efficiency and cost-effectiveness, especially when the flow of biomass (such as branches and tree tops) from the forest is increased. When the fibre material that negatively affects pulp properties is utilized as a bioenergy resource, the overall efficiency of the system is further improved. A TMP+BIGCC mathematic model is developed based on ASPEN Plus. By means of this model, three cases are studied:   1) adding more forest biomass logging residues in the gasifier, 2) adding a reject fraction of low quality pulp fibers to the gasifier, and 3) decreasing the TMP-specific electricity consumption (SEC) by up to 50%.   For the TMP+BIGCC mill, the energy supply and consumption are analyzed in comparison with a TMP+CHP mill. The production profit and the internal rate of return (IRR) are calculated. The results quantify the economic benefit from the TMP+BIGCC mill.   Bio-ethanol has received considerable attention as a basic chemical and fuel additive. It is currently produced from sugar/starch materials, but can also be produced from lignocellulosic biomass via a hydrolysis--fermentation or thermo-chemical route. In terms of the thermo-chemical route, a few pilot plants ranging from 0.3 to 67 MW have been built and operated for alcohols synthesis. However, commercial success has not been achieved. In order to realize cost-competitive commercial ethanol production from lignocellulosic biomass through a thermo-chemical pathway, a techno-economic analysis needs to be done.   In this work, a thermo-chemical process is designed, simulated, and optimized mainly with ASPEN Plus. The techno-economic assessment is made in terms of ethanol yield, synthesis selectivity, carbon and CO conversion efficiencies, and ethanol production cost.   Calculated results show that major contributions to the production cost are from biomass feedstock and syngas cleaning. A biomass-to-ethanol plant should be built at around 200 MW. Cost-competitive ethanol production can be realized with efficient equipments, optimized operation, cost-effective syngas cleaning technology, inexpensive raw material with low pretreatment cost, high-performance catalysts, off-gas and methanol recycling, optimal systematic configuration and heat integration, and a high-value byproduct.

La combustion de résidus de biomasse, généralement peu valorisés, pourrait apporter une solution d’approvisionnement intéressante pour la production d’énergie, allégeant la pression sur les ressources forestières. Toutefois, la composition chimique de ces résidus est à l’origine de problèmes techniques autant qu’environnementaux dans les procédés de combustion existants, ce qui limite leur utilisation. Deux de ces problèmes ont été traités dans cette thèse : les émissions de NOX et la quantité de potassium volatilisée lors de la combustion de différents résidus. Des essais de combustion ont été menés dans des réacteurs à l’échelle du laboratoire, sur des granulés de biomasse pure ou en mélange. Contrairement à la volatilisation du potassium, qui est liée à la teneur en différents éléments inorganiques, une relation linéaire forte (R² = 0,98) entre les émissions de NOX et la teneur en azote du combustible a été établie pour les granulés de biomasse pure. Des écarts par rapport à cette relation linéaire ont été observés dans le cas des essais menés sur des granulés de mélange, mettant en relief que la teneur en azote n’est pas le seul paramètre impliqué. Les travaux menés ont ainsi permis d’établir de manière originale que des synergies peuvent exister dans les granulés de mélange de résidus de biomasse, conduisant à des comportements différant de l’additivité directe des comportements des biomasses prises séparément. Ces synergies permettraient d’atténuer les problèmes causés par l’utilisation de ces résidus dans des chaudières en agissant de manière ingénieuse directement sur les propriétés des combustibles sans modification du procédé. / Combustion of biomass residues, which are generally poorly valued, could provide an attractive supply solution for energy production, alleviating pressure on forest resources. However, the chemical composition of these residues is causing both technical and environmental problems in existing combustion processes, which limits their use. Two of these problems have been addressed in this thesis: the amount of volatilized potassium and NOX emissions, when burning different residues. Combustion tests have been conducted in laboratory-scale reactors on pure and mixed biomass pellets. Variations in the amount of volatilized potassium was found to be linked to the content of multiple chemical elements for pure biomass pellets. In the case of NOx emissions, a strong correlation (R² = 0.98) with the nitrogen content of the fuel was found for pure biomass pellets. However, deviations from this linear relationship were observed for trials conducted on mixed biomass pellets, highlighting that the nitrogen content is not the only parameter involved. The work carried out thus made it possible to establish in an original way that synergies can exist in the pellets made of a mixture of biomass residues, leading to beneficial behaviors differing from the direct additivity of the biomass behaviors taken separately. These synergies could allow to mitigate the problems caused by the use of these residues in boilers by ingeniously acting directly on the properties of the fuels without modification of the process.

The cornerstone of our production system is based on the concept “take, make, waste”. Moreover, the manufacture of a product requires the input of energy and raw materials which produce waste and products. The latter ultimately end up becoming wastes. In other words, the root problem of this production system is that is designed on a linear, one-way cradle-to grave model (McDonough, W. and Braungart, M., 2002). This approach coupled with the population explosion and our thirst for growth has led to an unprecedented pressure to the environment. The consequences are multiple; climate change, dwindling energy resources and waste generation. This study lies in two pillars: the concept of sustainable development and the waste management hierarchy. The idea was how these two fundamental concerns (energy generation and waste production) could be tackled. This study assesses the availability of biomass residues and wastes in the off-grid island of Crete with the aim to ‘close the loop’ by converting waste to an energy resource. In addition, the exploration of the most sustainable energy generation solutions was attempted in order to drive forward the synergies between biomass waste production and energy generation. The collected information was extracted from the literature about agricultural, livestock, Municipal Solid Waste (MSW) and Industrial & Commercial (I&C) waste. It is also based on numerous interviews to waste management associations, the Greek Ministry of Rural Development & Food and all the Waste Water Treatment Plants in the island were analysed in order to shed light on the potential energy generation from all the aforementioned biomass sources and its contribution to the electric energy production system of Crete. It is considered that the biomass potential in Crete is a sleeping giant. There is considerable potential for biomass-to-energy technologies in Crete providing improved rural energy services based on agricultural residues. From the findings of this study it appears that the biomass potential is more than estimated in previous papers. Based on the findings it is concluded that the largest portion of Crete’s biomass potential is agricultural residues and animal wastes. The utilisation of low-cost biomass power in Crete could help provide cleaner, more efficient energy services and to reduce the island’s economic and environmental vulnerability. Biomass can provide both base load power and turn into liquid transportation fuels and contributes to reducing energy dependence due to import fuel from the mainland. In terms of the study’s goal to select the most sustainably viable biomass-to-energy technologies, that was based on the multi-criteria methodology. A number of integrated biomass-to-energy alternatives were assessed against technical, environmental, financial and social criteria with the aim to assist the regional authority’s decision making process of energy generation planning. From the final screening of the integrated biomass-to-energy alternatives it was concluded that the best in a descending order technologies from the regional authority’s standpoint are: F - Anaerobic digestion & Fuel cell; E – Anaerobic digestion & Gas engine; C - Gasification & Gas engine; A – Combustion & Steam turbine; and B – Gasification & Steam turbine.