Availability,supply technology and costs of residual forest biomass for energy – A case study in northern China

In theory, China has vast potential forest resources for production of energy, but utilization on an industrial scale has been negligible. We assessed the practical possibilities and barriers for a forest energy business in a case study in northern China. The specific objectives of the study were 1) to assess the availability of forest biomass for energy production, 2) to determine feasible supply chains, and 3) to estimate the biomass fuel supply costs. Based on the case study results, the stand-level removals of the intended feedstock were low and the supply costs were relatively high. Suggestions for increasing the raw material basis, lowering the costs and further research and development were given. We conclude that although the case study area may not be promising from the feedstock point of view, the development could be started with small steps and proven technology. In order to avoid expensive mistakes further research for transfer of know-how and technology is needed.     

Transformation of biomass into carbon nanofiber for supercapacitor application – A review

This paper starts with a review on challenges and need of improved supercapacitor application, which is then followed by advantages of biomass compared with other materials for use in supercapacitor application. The conversion of biomass into carbon nanofiber using different techniques was extensively reviewed for its advantages and limitations. It was revealed that the materials currently used are yet to be fully sustainable or feasible for energy storage application. In contrast, biomass represents a widely available and sustainable material to be converted into carbon nanofiber for energy storage application. Different techniques were employed for carbon nanofiber production to achieve different objectives, comprising high product yield, feasible diameter adjustment, low electric consumption, and shorter production time. Nevertheless, it was revealed that many key properties of the biomass-derived carbon nanofiber have yet to be fully investigated, as there are still knowledge gaps to be filled for each technique. Thus, more studies are needed to broaden the existing understanding in the key parameters of different techniques in order to develop a highly desirable carbon nanofiber from biomass for sustainable energy storage application.     

Estimation of methane production for batch technology – A new approach

In the case of agricultural biogas plants it is the living microorganisms (mainly archaea) that determine the amount of methane produced. If the conditions in the digester are not adequate or the substrates are selected incorrectly, the microorganisms will not be able to develop properly and methane production will also be low or none. Therefore, in the first place the influence of individual factors on the production of methane was analysed. Next, based on the conclusions drawn from the analysis of the factors, a mathematical model was developed that will facilitate the selection of appropriate substrates and process parameters by future investors building agricultural biogas plants. The aim of the study was to demonstrate the impact of the factors on the production of methane and to present a mathematical model for estimating methane production for batch technology used in agricultural biogas plants (this kind of production is also used in laboratories for testing specific substrates). The model presented in the paper has been developed and tested on a group of over seventy substrates of agricultural origin. The inclusion of many factors determining methane production in the model is not complicated as each of the factors is easy to measure.     

Furnace for biomass combustion – Comparison of model with experimental data

As one of the most easily accessible renewable energy resources, straw can be burned to provide heat energy. In this paper, results of theoretical and experimental research conducted under the proceedings of mathematical – numerical modeling of turbulent reacting flows has been presented. Two-dimensional turbulent flow model with homogeneous chemical reactions has been developed. The proposed model has been analyzed on the example of adiabatic combustion chamber for combustion of agricultural biomass. Turbulent flow is considered using time averaging Navier–Stokes equations that are closed by k–ε turbulence model. Calculations based on the proposed models were conducted using commercial CFD package FLUENT 6.3.26. For the purposes of experimental research, measurements of fluid flow and thermal parameters, such as continuous measurement of temperature in different points in the workspace furnace, air flow, flue gas flow, continual analysis of combustion products as well as setting heat and material balance, were carried out. Comparative analysis of the results of experiments and calculations indicate satisfactory agreement between the model and experiment.     

Burnout of pulverized biomass particles in large scale boiler – Single particle model approach

Burning of coal and biomass particles are studied and compared by measurements in an entrained flow reactor and by modelling. The results are applied to study the burning of pulverized biomass in a large scale utility boiler originally planned for coal. A simplified single particle approach, where the particle combustion model is coupled with one-dimensional equation of motion of the particle, is applied for the calculation of the burnout in the boiler. The particle size of biomass can be much larger than that of coal to reach complete burnout due to lower density and greater reactivity. The burner location and the trajectories of the particles might be optimised to maximise the residence time and burnout.     

Generation of skeletal and reduced reaction mechanisms for bio-derived syngas generated from biomass gasification – Experimental and numerical approach

Skeletal and reduced reaction mechanisms replicate the behavior of full reaction mechanism within the band/regime of optimization criteria and provide specific computational advantages for resource-intense multi-physics domain analysis. The current work reports on the development of skeletal and reduced mechanisms for bio-derived Producer gas and Hydrogen-rich Syngas by using GRI Mech 3.0 mechanism. The mechanisms are generated adopting graph-based approach, and timescale analysis are validated for laminar flame speed based on experiments in the equivalence ratios regime of 0.6–1.6 adopting a flame tube apparatus built in-house to mimic a freely propagating double infinity domain premixed reactor. Extending the analysis, the reduced/skeletal mechanisms are numerically validated for ignition delay time, major species profile, and volumetric heat release rate with validity established within the 5% tolerance limit. The current work is a first of its kind to propose optimized mechanism for compositions typical of bio-derived Producer gas and Syngas.     

Macro-economic impact of large-scale deployment of biomass resources for energy and materials on a national level—A combined approach for the Netherlands

Biomass is considered one of the most important options in the transition to a sustainable energy system with reduced greenhouse gas (GHG) emissions and increased security of enegry supply. In order to facilitate this transition with targeted policies and implementation strategies, it is of vital importance to understand the economic benefits, uncertainties and risks of this transition. This article presents a quantification of the economic impacts on value added, employment shares and the trade balance as well as required biomass and avoided primary energy and greenhouse gases related to large scale biomass deployment on a country level (the Netherlands) for different future scenarios to 2030. This is done by using the macro-economic computable general equilibrium (CGE) model LEITAP, capable of quantifying direct and indirect effects of a bio-based economy combined with a spread sheet tool to address underlying technological details. Although the combined approach has limitations, the results of the projections show that substitution of fossil energy carriers by biomass, could have positive economic effects, as well as reducing GHG emissions and fossil energy requirement. Key factors to achieve these targets are enhanced technological development and the import of sustainable biomass resources to the Netherlands.     

Multi-scale complexities of solid acid catalysts in the catalytic fast pyrolysis of biomass for bio-oil production – A review

Despite remarkable progress in catalytic fast pyrolysis, bio-oil production is far from commercialization because of multi-scale challenges, and major constraints lie with catalysts. This review aims to introduce major constraints of acid catalysts and simultaneously to find out possible solutions for the production of fuel-grade bio-oil in biomass catalytic fast pyrolysis. The catalytic activities of several materials which act as acid catalysts and the impacts of Bronsted and Lewis acid site on the formation of aromatic hydrocarbons are discussed. Considering the complexity of catalytic fast pyrolysis of biomass with acid catalysts, in-depth understandings of cracking, deoxygenation, carbon-carbon coupling, and aromatization for both in-situ and ex-situ configurations are emphasized. The limitation of diffusion along with coke formation, active site poisoning, thermal/hydrothermal deactivation, sintering, and low aromatics in bio-oil are process complexities with solid acid catalysts. The economic viability of large-scale bio-oil production demands progress in catalyst modification or/and developing new catalysts. The potential of different catalyst modification strategies for an adequate amount of acid sites and pore size confinement is discussed. By critically evaluating the challenges and potential of catalyst modification techniques, multi-functional catalysts may be an effective approach for selective conversion of biomass to bio-oil and chemicals through catalytic fast pyrolysis. This review offers a scientific reference for the research and development of catalytic fast pyrolysis of biomass.     

Evaporator modeling – A hybrid approach

In this paper, a hybrid modeling approach is proposed to model two-phase flow evaporators. The main procedures for hybrid modeling includes: (1) Based on the energy and material balance, and thermodynamic principles to formulate the process fundamental governing equations; (2) Select input/output (I/O) variables responsible to the system performance which can be measured and controlled; (3) Represent those variables existing in the original equations but are not measurable as simple functions of selected I/Os or constants; (4) Obtaining a single equation which can correlate system inputs and outputs; and (5) Identify unknown parameters by linear or nonlinear least-squares methods. The method takes advantages of both physical and empirical modeling approaches and can accurately predict performance in wide operating range and in real-time, which can significantly reduce the computational burden and increase the prediction accuracy. The model is verified with the experimental data taken from a testing system. The testing results show that the proposed model can predict accurately the performance of the real-time operating evaporator with the maximum error of ±8%. The developed models will have wide applications in operational optimization, performance assessment, fault detection and diagnosis.     

Urban lignocellulosic biomass can significantly contribute to energy production in municipal wastewater treatment plants – A GIS-based approach for a metropolitan area

The common fermentation of biogenic wastes and sewage sludge in digesters of municipal wastewater treatment plants is a technically feasible and economically viable approach. As the number of rural biogas production sites is steadily increasing, the question has been raised which biomass feedstocks are left available in sufficient quantities to be used for energy generation at wastewater treatment plant level. The contribution of lignocellulosic biomass collected from urban areas is generally neglected within this context. In the present study, 24 urban substrates have been analyzed for their theoretical methane potential, while 13 of them were tested in batch assays for the determination of their practical achievable methane yield. The theoretical evaluation of the methane potential yielded values ranging between 0.393 and 0.576 Nm³ kgVS⁻¹. The methane yields obtained by batch assays showed significantly lower yields, which depends on the individual composition of the substrates in terms of lignin, hemicellulose and cellulose. A GIS spatial analysis for the Rhine-Ruhr metropolitan area was performed to evaluate the feasible capacity of urban biomass as co-fermentation feedstock in digesters of municipal wastewater treatment plants. The analysis revealed that green urban areas provide a significant quantity of biomass of 377 t_FM d⁻¹ that could cover 67% of the annual energy demand of twelve typical wastewater treatment plants located in the metropolis.     

The baseline in bottom-up energy efficiency and saving calculations – A concept for its formalisation and a discussion of relevant options

One of the central variables in bottom-up energy efficiency and saving calculations is the energy consumption baseline. In the evaluation of energy efficiency measures, developing this baseline is a challenging task, which may involve serious problems, especially if the energy service of the analysed subject has changed while the energy efficiency measure was being implemented. In this paper we present a formalised concept of the process of developing the baseline that is flexible enough to deal with various difficulties, such as changes in the levels of the energy services involved. We also discuss the most relevant options for deriving the necessary variables.     

Estimating future costs of power-to-gas – a component-based approach for technological learning

Technological learning is a major aspect in the assessment of potential cost reductions for emerging energy technologies. Since the evaluation of experience curves requires the observation of production costs over several magnitudes of produced units, an early estimation of potential future technology implementation costs often presumes a certain degree of maturity. In this paper, we propose a calculation model for learning curves on the component or production process level, which allows to incorporate experience and knowledge on cost reduction potentials on a low level. This allows interchangeability between similar technologies, which is less feasible on a macro level. Additionally, the model is able to consider spill-over effects from concurrent technology usages for the inclusion of peripheral standard components for the assessment in an overall system view. The application of the model to the power-to-gas technology, especially water electrolysis, has shown, that the results are comparable to conventional approaches at the stack level, while providing transferability between different cell designs. In addition, the investigations made at the system level illustrate that the consideration of spill-over effects can be a relevant factor in the evaluation of cost reduction potentials, especially for technologies in an early commercial state with low numbers of cumulative productions.     

Sustainability assessment of wood-based bioenergy – A methodological framework and a case-study

The sustainability of the utilization of wood biomass for energy and other purposes has been widely assessed in different studies. Especially discrete methods from the family of Multi-Criteria Decision Analysis (MCDA), such as Outranking methods, Multi-Attribute Utility Theory, and Analytic Hierarchy Process (AHP) are often applied. AHP is considered one of the most promising options to be used in sustainability assessments, because it is comprehensible to apply and it incorporates the preferences of decision-makers in an advanced manner. In this study, we present a theoretical multi-dimensional framework based on a modified version of AHP for assessing sustainability and apply it in a case of wood-based bioenergy production in eastern Finland. The framework includes four dimensions of sustainability and life cycle phases from the acquisition of raw material to manufacturing the final product. The production systems used in the empirical sustainability assessments are a local heat production plant, a combined heat and power production plant, and a wood pellet processing plant. Local sustainability experts identified indicators relevant at the regional scale. The impact assessment data were obtained from literature, by interviewing the managers of the bioenergy plants, and from a postal survey administered to local people. The local heat provider received the highest sustainability index; however, there were no considerable differences between the sustainability indexes. None of the bioenergy production systems can be considered the most sustainable regardless of the assumptions employed in the framework. The framework provided the basis for a quantitative, interdisciplinary approach to assess sustainability.     

Systematic approach for recognizing limiting factors for growth of biomethane use in transportation sector – A case study in Finland

In this paper, limiting factors for increased use of biomethane as a transportation fuel are studied. The aim of this research is to recognize and estimate the limiting factors for biomethane utilization in the transportation sector. The limiting factors are studied by using calculation models from Life cycle perspective and literature reviews. According to the results, the main limiting factors can be classified into the following categories: production potential, technology, economy or policy. For biomethane utilization in Finland, the main limiting factors seem to be the lack of distribution infrastructure in northern parts of the country and the uncertain economical feasibility for agricultural biomass producers and for vehicle owners. From the political perspective, the external costs for petrol operated vehicles are higher than for biomethane operated vehicles. Reductions from the external costs could be used by political decisions as a base to support the growth of biomethane in the transportation sector which could lead to GHG emission reductions. A similar systematic approach can also be used to study limiting factors for other transportation energy systems.     

Scenarios for biofuel demands,biomass production and land use – The case of Denmark

The land potential for producing biomass for bioenergy purposes has been highly debated in recent years. The present paper analyses the possibilities and consequences for land use and agricultural production of biofuel production in Denmark based on domestic wheat and rape under specific scenario conditions for the period 2010–2030. The potential is assessed for a situation where policy targets for renewable energy carriers in the transport sector is reached using biofuels, and where second generation ethanol increasingly substitutes first generation ethanol.Three scenarios are developed and evaluated: a baseline, an alternative scenario allowing continuous growth in the now dominant livestock branch and a biofuel scenario assuming that efforts to achieve self-sufficiency in biofuel displaces part of the domestic production of fodder.Results show that the biofuel demand could be met in 2020; but only if current rape oil production is used to satisfy local bio-diesel demand. It would also imply that the Danish bio-diesel export currently supplying a minor part of the German fuel market would seize. In 2030, however, only about 60 percent of the biofuel demand would be covered by self-sufficiency. If biofuels were to displace animal production to make up for this, a reduction of the pig production between 10 and 20 percent would result. Efficiency increases across production branches would allow the animal production to continue un-affected if about half of the rape oil produced for other purposes is utilized.     

Integrated drying and gasification of wet microalgae biomass to produce H2 rich syngas – A thermodynamic approach by considering in-situ energy supply

A novel integrated drying and gasification of microalgae wet biomass process, involving a chemical-looping combustion (CLC) option to supply energy, is developed using Aspen Plus. The integrated gasification system consists of four primary units, including (i) a wet biomass drying unit, (ii) the gasification system, (iii) the CLC section, and (iv) the gas purification process. The model shows a good accuracy (relative error < 10%) in predicting the product compositions as compared to the experimental results under consistent operating conditions. The performance of the integrated gasification system is evaluated using Spirulina microalgae at various moisture contents (0–45 wt%). The effect of gasifying agents O₂/steam and the fraction of the produced char used in the CLC section on the gasification performance is also evaluated. The tar is successfully reformed into syngas in the pyrolysis stage by adjusting the O₂ flow rate. The C (char) to CLC provides to a positive effect on the syngas composition, particularly for gasification of wet biomass, but brings an adverse impact on the yield of the syngas product. The integration of the CLC process and CO₂ absorber in the gasification system provides high-quality syngas by removing CO₂. The separated pure CO₂ can be used as a feedstock for other chemical industries.     

Hydrogen production from steam gasification of biomass: Influence of process parameters on hydrogen yield – A review

Steam gasification is considered one of the most effective and efficient techniques of generating hydrogen from biomass. Of all the thermochemical processes, steam gasification offers the highest stoichiometric yield of hydrogen. There are several factors which influence the yield of hydrogen in steam gasification. Some of the prominent factors are: biomass type, biomass feed particle size, reaction temperature, steam to biomass ratio, addition of catalyst, sorbent to biomass ratio. This review article focuses on the hydrogen production from biomass via steam gasification and the influence of process parameters on hydrogen yield.     

Can hydrogen or natural gas be alternatives for aviation? – A life cycle assessment

Between 1989 and 2011 the aviation traffic has been growing 4.6% per year. The increase on aviation traffic had consequences in terms of greenhouse gases (GHGs) and local pollutant emissions (e.g. carbon monoxide – CO, hydrocarbons – HC, nitrogen oxides – NO_x). In order to minimize this problem, the evaluation of sustainable alternatives to current fuel (jet fuel A) has been discussed but their impact on emissions is still unclear. The main research goals of this paper are: (i) to evaluate if the well-to-wake energy consumption in aviation can be reduced with alternative fuels as liquid natural gas (LNG) and/or liquid hydrogen (LH₂) and (ii) to assess if alternative fuels can be used in aviation to minimize carbon dioxide emissions and local pollutants.     

Prospects for solar cooling – An economic and environmental assessment

Producing refrigeration and/or air conditioning from solar energy remains an inviting prospect, given that a typical building’s cooling load peaks within 2 or 3 h of the time of maximum solar irradiation. The attractiveness of “free” cooling obtained from the sun has spawned a wealth of research over the last several decades, as summarized in a number of review articles. Obstacles—especially high initial costs—remain to the widespread commercialization of solar cooling technologies. It is not clear at the present time if thermally driven systems will prove to be more competitive than electrically driven systems. We therefore describe a technical and economic comparison of existing solar cooling approaches, including both thermally and electrically driven. We compare the initial costs of each technology, including projections about future costs of solar electric and solar thermal systems. Additionally we include estimates of the environmental impacts of the key components in each solar cooling system presented. One measure of particular importance for social acceptance of solar cooling technologies is the required “footprint,” or collector area, necessary for a given cooling capacity. We conclude with recommendations for future research and development to stimulate broader acceptance of solar cooling. The projections made show that solar electric cooling will require the lowest capital investment in 2030 due to the high COPs of vapor compression refrigeration and strong cost reduction targets for PV technology.     

Analytical model of a solarium for cold climate—A new approach

In this present communication, a new approach has been evolved for analysing the thermal performance of a solarium useful in a cold climate. So as to trap the maximum solar radiation, the concept of glass windows (with movable insulation) in both the east and west walls of the sun space, besides in its south facing will and with the roof made of glass, has been introduced. Considering the ground temperature constant over a day, an overall heat transfer coefficient has been incorporated for the estimation of the heat flux transferred from the floor of the solarium to the ground. The introduction of this heat transfer coefficient eliminates the need of solving the conductivity equation for the heat flux conducted from the floor of the solarium to the ground. On account of the almost insulating behaviour of wood, an overall heat transfer coefficient has been taken for an all wooden structure of the solarium. Carrying out a transient analysis, explicit expressions for the temperatures of the sun space, the blackened absorbing surface of the water wall, the water itself, the living space and the isothermal masses have been developed as a function of time. These temperatures are required for the evaluation of the thermal energy taken in by the water wall, the heat flux entering the sun space and living space and the thermal energy distributed over the isothermal masses lying in the living space.