Heat, Electricity, or Transportation? The Optimal Use of Residual and Waste Biomass in Europe from an Environmental Perspective

The optimal use of forest energy wood, industrial wood residues, waste wood, agricultural residues, animal manure, biowaste, and sewage sludge in 2010 and 2030 was assessed for Europe. An energy system model was developed comprising 13 principal fossil technologies for the production of heat, electricity, and transport and 173 bioenergy conversion routes. The net environmental benefits of substituting fossil energy with bioenergy were calculated for all approximately 1500 combinations based on life cycle assessment (LCA) results. An optimization model determines the best use of biomass for different environmental indicators within the quantified EU-27 context of biomass availability and fossil energy utilization. Key factors determining the optimal use of biomass are the conversion efficiencies of bioenergy technologies and the kind and quantity of fossil energy technologies that can be substituted. Provided that heat can be used efficiently, optimizations for different environmental indicators almost always indicate that woody biomass is best used for combined heat and power generation, if coal, oil, or fuel oil based technologies can be substituted. The benefits of its conversion to SNG or ethanol are significantly lower. For non-woody biomass electricity generation, transportation, and heating yield almost comparable benefits as long as high conversion efficiencies and optimal substitutions are assured. The shares of fossil heat, electricity, and transportation that could be replaced with bioenergy are also provided.

Analysis of the Availability of Bioenergy and Assessment of its Optimal Use from an Environmental Perspective

Bernhard Steubing

This thesis addresses the availability and environmentally optimal use of bioenergy. A life cycle perspective is adopted to consider the supply, the technical conversion, and the final use of bioenergy as well as its use for the substitution of fossil energy. In order to determine the sustainable energetic biomass potential in Switzerland, which is the geographic focus of this thesis, a bioenergy potential assessment is conducted using a sustainability constraints approach. Life cycle assessment (LCA) is performed to analyse the suitability of the conversion of wood to synthetic natural gas (SNG). However, individual technology LCAs are not sufficient to provide answers to the question of "how energetically available biomass resources can be used optimally for bioenergy from an environmental perspective". Instead, more comprehensive trans-sectoral assessments are required including all relevant bioenergy technologies and end-uses, as well as fossil energy technologies that can be substituted. To enable such analyses, an LCA-based system optimization (LCA-SO) framework is developed and applied to the Swiss and European cases. Finally, also spatial aspects need to be considered to determine optimal plant sizes. Therefore, a spatially explicit bioenergy value chain model was developed for the case of SNG plants in Switzerland. One of the main findings of this thesis is that 82 PJ of biomass is available in Switzerland, which corresponds to approximately 7% of its primary energy demand. Half of this potential has yet to be realized. By 2035, when optimally used in the business as usual scenario defined by the Swiss Energy Perspectives, biomass could mitigate about 5 megatons of CO2, which would be equal to 13% of Switzerland's total emissions. Simultaneously, the demand of fossil energy for heat, electricity, and transportation would be reduced by 13%, 3%, and 2%, respectively. In the European Reference Scenario (2030) 9%, 13%, and 1%, respectively, of fossil heat, electricity, and transportation could be replaced and 600 Mt of CO2, equal to about 15% of the EU's total emissions, could be avoided. To achieve these goals, woody biomass should be used mainly for heating and combined heat and power (CHP) generation. The production of SNG from wood to substitute fossil energy has been found environmentally beneficial from the GHG, Ecological Scarcity, and Eco-indicator 99 perspectives. However, the production of transportation fuel from woody biomass is, at the current technological development state, associated with important efficiency losses and is therefore not considered an optimal solution. For non-woody biomass (by which we refer to agricultural residues, manure, bio- and food industry wastes, and sewage sludge) the optimal use is to a large degree determined by the substitution of fossil energy and varies according to the environmental indicator applied. For all biomass, it is vital that a high substitution efficiency is achieved, which implies an efficient conversion of biomass and the choice of optimal substitutions. Finally, the spatially explicit bioenergy modelling conducted in this work indicates that smaller bioenergy plant sizes are slightly preferable in terms of overall environmental benefits, mainly due to reduced transportation distances. However, further analyses would be required to generalise this finding.

EPFL2011

Next generation cogeneration system for industry - Combined heat and fuel plant using biomass resources

Ayse Dilan Celebi, François Maréchal, Adriano Viana Ensinas

The requirement for sustainable development has prompted the researchers to explore solutions for better utilization of renewable energy resources in the future. Biomass is a promising resource and it can be converted to multiple products and services including fuels, chemicals, heat and electricity via different conversion routes. Hence, replacement of fossil-based services with biomass-based services is critical to mitigate fossil CO2 emissions, and innovative design of new and efficient energy conversion systems is necessary. Different industries need heat for their operations at different temperature levels. Today, these demands are satisfied using conventional natural gas boilers by imposing a CO2 tax to account for their emissions. In this study, we discuss the potential of replacing conventional boilers with a combined heat and fuel (CHF) plant design which utilizes lignocellulosic biomass in thermochemical conversion to generate heat for different industrial sectors together with biofuels cogeneration. Heat is generated due to the exothermic nature of the thermochemical conversion processes that operate at high temperatures. Gasification process produces syngas which is converted into fuels such as synthetic natural gas, Fischer-Tropsch crude, methanol and dimethyl ether and electricity. Different scenarios are evaluated considering the CO2 produced via this system is either released, sequestrated, or stored and used in a co-electrolysis unit in which surplus renewable electricity available during summer is converted into additional syngas. A parametric analysis has been performed considering type and size of plants, CO2 tax, and purchase and transportation costs of wood to compare the price of heat for the industrial sectors. Natural gas and wood boilers are used as the basis to calculate the breakeven CO2 tax values for the same heat prices for the proposed CHF systems. The results of this study present a state-of-the-art renewable energy system as an alternative to conventional boilers. (C) 2019 Elsevier Ltd. All rights reserved.

2019

Thermochemical production of liquid fuels from biomass: Thermo-economic modeling, process design and process integration analysis

Martin Gassner, François Maréchal, Laurence Tock

A detailed thermo-economic model combining thermodynamics with economic analysis and considering different technological alternatives for the thermochemical production of liquid fuels from lignocellulosic biomass is presented. Energetic and economic models for the production of Fischer-Tropsch fuel (FT), methanol (MeOH) and dimethyl ether (DME) by the means of biomass drying with steam or flue gas, directly or indirectly heated fluidized bed or entrained flow gasification, hot or cold gas cleaning, fuel synthesis and upgrading are reviewed and developed. The process is integrated and the optimal utility system is computed. The competitiveness of the different process options is compared systematically with regard to energetic, economic and environmental considerations. At several examples, it is highlighted that process integration is a key element that allows for considerably increasing the performance by optimal utility integration and energy conversion. The performance computations of some exemplary technology scenarios of integrated plants yield overall energy efficiencies of 59.8% (crude FT-fuel), 52.5% (MeOH) and 53.5% (DME), and production costs of 89, 128 and 113 EUR/MWh on fuel basis. The applied process design approach allows to evaluate the economic competitiveness compared to fossil fuels, to study the influence of the biomass and electricity price and to project for different plant capacities. Process integration reveals in particular potential energy savings and waste heat valorization. Based on this work, the most promising options for the polygeneration of fuel, power and heat will be determined in a future thermo-economic optimization.