Sustainability improvement in combined electricity and freshwater generation systems via biomass: A comparative emergy analysis and multi-objective optimization

For energy systems, sustainability is a major concern that must be carefully considered when designed and established. Emergy analysis is an effective technique to scrutinize the sustainability of these systems. On the other hand, water shortage is seen to become a big problem in the close future; however, this problem can be effectively alleviated by combined electricity/water production plants, where waste heat is recovered to generate freshwater. This study applies emergy analysis to evaluate and improve the sustainability, renewability, environmental impacts, and economic aspect of such a plant, in which a multi-stage desalination (MSF) system is employed to recover the waste heat from a gas turbine (GT). The plant is fueled by biomass/natural gas (system I), natural gas (system II), and biomass (system III), and the above-mentioned features are compared for the different fuel types. To estimate chemical equilibrium state inside the gasifier, Lagrange's method of undetermined multipliers is applied. Also, considering exergy efficiency and emergy sustainability index as objective functions, biomass/natural gas-fueled system is optimized by adopting a multi-objective optimization approach based on the non-dominated sorting genetic algorithm II (NSGA II). To predict the optimized points' behavior, the Pareto optimal frontier of the system is utilized. The results reveal that using biomass as inlet fuel remarkably improves the sustainability index and reduces environmental impacts. The optimization results show that as sustainability index increases, exergy efficiency decreases. Also, the two optimized points of the system are found to have exergy efficiencies of 20.14% and 25.09% and sustainability indices of 24.67% and 13.60%.     

The policymaking process for creating competitive assets for the use of biomass energy: the Brazilian alcohol programme

Public policies are fundamental to spur the use of biomass and make it competitive to face traditional commercial fossil fuels. This article analyzes the policymaking process of the Brazilian National Alcohol Policy (Proalcool). Proalcool is one of the world's most ambitious efforts to produce a renewable biomass fuel as an oil substitute. In the 1970s, after the oil crisis and the sharp increase in fuel prices, the Brazilian government started intensifying its policy to substitute sugarcane alcohol for gasoline in automobile use. Through a set of governmental interventions to increase alcohol demand and supply, Brazil created some competitive assets that made Proalcool a relative success in terms of developing institutional and technological capabilities for using renewable energy in large scale. Several key actors influenced the policy directions, such as the central and state governments, military groups, the alcohol industry, sugarcane agricultural aristocracy, bureaucrats, researchers and the media. Instead of thinking of Proalcool as a government decision based only on economic rationale or interests of few decision-makers, the elaboration and implementation of this alcohol policy could be thought of as the result of a policymaking process where the different stakeholders involved in the process with their values, interests and knowledge interacted with each other according to the political, social, technological and economic situation.     

China's transition to green energy systems: The economics of home solar water heaters and their popularization in Dezhou city

Studying the popularization of solar water heaters (SWHs) is significant for understanding China's transition to green energy systems. Using Dezhou as a case study, this paper presents new angles on analyzing SWH deployment in China by addressing both the economic potential and the institutional dimensions at the local level. Using estimates from the demand-side of hot water for a typical three-person household in Dezhou, the paper evaluates the economic potential of a SWH in saving electricity and reducing carbon dioxide emissions. Then, expanding the analysis beyond economics, we take an institutionalist approach to study the institutional factors that contribute to Dezhou's success in SWH adoptions. By examining the five main actors in Dezhou's energy regime, we find that Dezhou's SWH deployment is driven by an urge to develop businesses and the local economy, and its success results from at least five unique factors, including the development of SWH industrial clusters in Dezhou, big manufacturers' market leadership in SWH innovations, a tight private enterprise-local government relation, geographic location within the SWH industrial belt, and the adaptive attitude of Dezhou's households towards natural resource scarcity.     

Economic risk assessment of advanced process technologies for bioethanol production in South Africa: Monte Carlo analysis

The development of ethanol industry for use as an alternative motor fuel has been steadily increasing around the world for several reasons. In South Africa, this industry is still in the early stages of development. In the National Biofuels Industrial Strategy, the South African government has made provision for support mechanisms to encourage investment in bioethanol production. There is thus an opportunity for grain-growing farmers to cultivate available or marginal lands for bioethanol crops, including triticale. This article examines the contribution of parametric uncertainty to economic feasibility studies for biomass-to-ethanol process plants. Monte Carlo (stochastic variable) simulation is employed as a tool to determine probability distributions for economic indicators (such as NPV and ROI) in the context of a proposed 200,000 tonnes per annum triticale grain ethanol plant located in the Western Cape province of South Africa. Three process technology scenarios are considered: a conventional starch-to-ethanol plant (Scenario I), an advanced starch-to-ethanol with grain fibre fractionation and energy recovery (Scenario II) and an integrated starch-cellulose plant where fractionated fibre is converted to fermentable sugars by pretreatment and enzymatic hydrolysis and then fermented to fuel alcohol (Scenario III). By modelling prices of raw materials and products stochastically, based on historical data, the concurrent fluctuations in prices are accounted for, incorporating a quantifiable measure of the associated financial risk to a typical (deterministic) economic prefeasibility analysis. Risk assessment of all processing options reveals that Scenario II is the most preferred fermentation process, achieving very high probability of economic success (98% probability of NPV > 0), suggesting that, under almost all conceivable circumstances of price fluctuation and plant availability, the investment will be successful. This is followed by Scenario III (96% probability of NPV > 0) while the least preferred option is Scenario I (93% probability of NPV > 0). The study also shows, however that without government subsidy, the plant exhibits only a 19% chance of economic success. Economic performance is shown to improve when fast-growing biomass is used to replace electricity as a fuel source for process heating. Monte Carlo simulation could assist energy planners, investors, and policy/decision makers to make a better management decision by identifying possible public policy that could be used to enhance the economic viability of the proposed ethanol plant.     

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

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 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 € MWh^?1 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.     

Biomethanol production from gasification of non-woody plant in South Africa: Optimum scale and economic performance

Methanol production from biomass is a promising carbon neutral fuel, well suited for use in fuel cell vehicles (FCVs), as transportation fuel and as chemical building block. The concept used in this study incorporates an innovative Absorption Enhanced Reforming (AER) gasification process, which enables an efficient conversion of biomass into a hydrogen-rich gas (syngas) and then, uses the Mitsubishi methanol converter (superconverter) for methanol synthesis. Technical and economic prospects for production of methanol have been evaluated. The methanol plants described have a biomass input between 10 and 2000 MW_th. The economy of the methanol production plants is very dependent on the production capacity and large-scale facilities are required to benefit from economies of scale. However, large-scale plants are likely to have higher transportation costs per unit biomass transported as a result of longer transportation distances. Analyses show that lower unit investment costs accompanying increased production scale outweighs the cost for transporting larger quantities of biomass. The unit cost of methanol production mostly depends on the capital investments. The total unit cost of methanol is found to decrease from about 10.66 R/l for a 10 MW_th to about 6.44 R/l for a 60 MW_th and 3.95 R/l for a 400 MW_th methanol plant. The unit costs stabilise (a near flat profile was observed) for plant sizes between 400 and 2000 MW_th, but the unit cost do however continue to decrease to about 2.89 R/l for a 2000 MW_th plant. Long term cost reduction mainly resides in technological learning and large-scale production. Therefore, technology development towards large-scale technology that takes into account sustainable biomass production could be a better choice due to economic reasons.     

Economic feasibility of algal biodiesel under alternative public policies

The motivation for this research was to determine the influence of public policies on economic feasibility of producing algal biodiesel in a system that produced all its energy needs internally. To achieve this, a steady-state mass balance/unit operation system was modeled first. Open raceway technology was assumed for the production of algal feedstock, and the residual biomass after oil extraction was assumed fermented to produce ethanol for the transesterification process. The project assumed the production of 50 million gallons of biodiesel per year and using about 14% of the diesel output to supplement internal energy requirements. It sold the remainder biodiesel and ethanol as pure biofuels to maximize the rents from the renewable fuel standards quota system. Assuming a peak daily yield of 500 kg algal biomass (dry basis)/ha, the results show that production of algal biodiesel under the foregoing constraints is only economically feasible with direct and indirect public policy intervention. For example, the renewable fuel standards' tracking RIN (Renewable fuel Identification Number) system provides a treasury-neutral value for biofuel producers as does the reinstatement of the renewable fuel tax credit. Additionally, the capital costs of an integrated system are such that some form of capital cost grant from the government would support the economic feasibility of the algal biodiesel production.     

广东省生物质发电应用的影响因素分析

中国农林生物质发电装机已超过“十三五”规划的目标,但华南地区如广东省的生物质发电装机只占全国的3.2%,发展相对落后,生物质发电利用存在区域发展不平衡的问题。本文采用德尔菲法、多标准技术筛选模型及生物质发电项目财务分析模型,以广东省为例,分析其生物质发电应用的主要影响因素并提出建议。分析结果表明,广东省生物质总资源量为3 300万t,发电潜力为1 196亿kW?h,而其中的经济潜力为174亿kW?h,全省生物质发电实际利用量仅占经济潜力的17.6%,生物质发电利用仍有巨大的发展空间。大规模的生物质发电项目的原料需求量大,收集半径过大,原料价格及收集与运输成本过高,导致发电成本超过0.8元/(kW?h),大于0.75元/(kW?h)的生物质标杆电价,致使项目折现投资回收期超过30年,内部收益率不足1%,项目财务负担过重,严重制约了生物质发电利用的发展;研究引入企业所得税收优惠以及原料处理费补贴,发现项目财务主要指标均得到显著改善。建议开发前期对周边原料市场进行调研考察,将原料种类多样化并根据气候和物流特点制定详细的原料收集规划,新建生物质电厂应控制装机规模在30 MW以内,使得原料收集范围在300 km以内,以控制原料收集与运输成本;完善税收优惠政策,政策应涵盖更多的生物质原料种类,使电厂能享受相应优惠;建立原料处理费补贴机制,以原料中生物质废物垃圾比例为指标发放补贴,实现外部环境成本内部化,提高环保效益,促进广东省生物质能利用的发展。     

Use of pyrolysis oil in a test diesel engine to study the feasibility of a diesel power plant concept

The economic viability of power production in a diesel power plant utilizing flash pyrolysis oil produced from sawmill wastes in Finland has been investigated. A combination of biomass feedstock costs, pyrolysis oil fuel properties (ignition quality, lubricating properties, combustion speed and duration, emissions, etc.) and their effect on power plant investments and maintenance will ultimately determine electricity busbar costs and the economic competitiveness of the concept. Pyrolysis oil is not a suitable fuel for a conventional diesel engine as such. The preliminary tests with additive treated pyrolysis oil demonstrated, however, that once ignition has taken place, pyrolysis oil burns rapidly. Pyrolysis oil may be a suitable primary fuel for a diesel engine with a pilot injection system, which secures the ignition of the main fuel.     

Understanding an improved cookstove program in rural Mexico: An analysis from the implementers' perspective

The adoption of innovations in rural areas depends, among many different factors, on the way development workers approach a community. Through a qualitative research methodology this study documented the adoption of a new technology, by following an improved cookstove implementation program carried out by a Mexican NGO. This technology reduces fuel consumption and addresses health impacts of indoor air pollution caused by the widespread use of traditional biomass fuels in open fires in developing countries. Different demographic and socio-economic factors have been analyzed to explain the low success rates implementation projects have faced worldwide, but there are almost no studies that examine the problem from the perspective of implementers. The aim of this study was to understand how the different visions of the individuals involved in an implementation program affect its outcome. Findings showed that the NGO work was constrained by the need to meet the commitment with sponsors. The adoption rates did not change between the first and the second stage of the project, even though the approach towards users was very different. A lack of a shared vision among the work team towards the project was found and the existence of two main perspectives among program workers—broadly described as people-centered and technology-centered—, gave place to differences in attitudes towards the program.     

A lifecycle-based success framework for grid-connected biomass energy projects

This paper presents a new framework to help assessing the success and its drivers of biomass energy projects. Empirical validation of the framework using data collected from operating grid-connected biomass energy plants in Thailand indicates that competencies of developer and project team members in designing biomass energy plants and conducting environment impact assessment (EIA) are significant factors for the success of the project development phase. In the construction phase, effective coordination, consultation and communication among the project team and the contractors emerge as the most significant success factors, while a competent management and O&M team is found critical to success during the operation phase. External factors such as the presence of supportive legislative, political and regulatory framework are found most instrumental for achieving overall project success. The framework demonstrates the dynamic linkage of project management success in successive lifecycle stages and phases, and thus can be used to evaluate and forecast the likelihood of success of biomass energy projects progressively over their lifecycle.     

Innovation diffusion,public policy,and local initiative: The case of wood-fuelled district heating systems in Austria

This paper comprises a three-level study on wood fuel utilisation for district heating in Austria. First, we discuss the framework conditions for the diffusion in Austria of rural biomass district heating (BDH) plants, an energy conversion plant type which constituted a real innovation in the 1980s. Second, we describe the diffusion of BDH systems in the Austrian province of Vorarlberg, where a variety of biomass energy systems have been promoted by capital grants since 1993, as part of a dedicated bioenergy promotion programme. Third, the paper contains a case study of a 2 MW BDH plant put into operation in 2000 in Rankweil, a small market town located in Vorarlberg on the east side of the Rhine Valley. Analysis of the plant history reveals that an oversupply of forest residues, caused by devastating storms and forest diseases, together with the more general need to rejuvenate severely over-aged forest stands, created strong incentives to form local actor networks and initiatives to push for the adoption and diffusion of centralised biomass heating systems in rural areas. In addition, intensive lobbying and strong political and public support were necessary to successfully combat interventions by both the natural gas industry and influential gas-supplied industrial enterprises. Finally, a capital grant of 45% of eligible investment costs as well as careful capacity expansion and other planning significantly improved and safeguarded the economic viability of the plant. These considerations, combined with a dedicated forest-restructuring programme, render the plant one of the most successful integrated forestry and BDH projects in Vorarlberg, and an important model for later adopters. Overall, the analysis sheds some light on the role of public policy, local actors, and economic and other framework conditions on the market diffusion dynamics of BDH in Austria.     

Reassessing the “energy ladder”: Household energy use in Maun,Botswana

In the context of Sub-Saharan Africa's rapid urbanization, improved insight into urban energy use is increasingly important. Based on the predictions of “energy transition” theory, a regional shift from biomass to “modern” fuels has long been expected to occur in tandem with urban growth. However, trends observed in the region's towns and cities have often not followed such patterns and fuelwood continues to be important in most areas. This paper examines the practical relevance of transition theory using a recent case study, conducted by the authors in Maun, Botswana, and results previously reported in the literature. It finds that, despite the long-term link between socio-economic development and increased modern fuel consumption at the national scale, the notion of “transition” does not accurately reflect ongoing energy-use patterns at lower levels of aggregation. This is chiefly because its model of household fuel switching largely dismisses the importance of active (and strategic) decision making by urban consumers and their responsiveness to structural factors such as relative fuel prices. As the Botswana case illustrates, this weakness can significantly distort expectations and policies around urban fuelwood use.     

Domestic fuel energy consumption in an Indian urban ecosystem

Berhampur is one of the oldest and biggest towns of Orissa State where 93% of people earn their living from non-primary economic activities. The fuel consumption structure reveals an element of rural bias since the domestic sector derives 49% of its energy used for cooking and heating from biomass sources. Firewood is the only fuel used by all income groups and almost all occupations. Other traditional fuels such as dungcake, agricultural waste and leaf litter are used in the town with different degrees of dominance in various occupation groups and income classes. The inequality of income distribution is reflected in the fuel consumption structure of the rich and poor with greater dependence on non-biomass in the high income group and biomass in the low income group. Family size is an important determinant of biomass fuel use. For the urban poor, there is a relationship between income and fuel consumption. There exists scope for enlarging the biomass base by utilising the available bio-wastes and developing a green belt around the town. This requires some rural features in the urban area using new technologies.     

Potential availability of urban wood biomass in Michigan: Implications for energy production,carbon sequestration and sustainable forest management in the U.S.A.

Tree and wood biomass from urban areas is a potentially large, underutilized resource viewed in the broader social context of biomass production and utilization. Here, data and analysis from a regional study in a 13-county area of Michigan, U.S.A. are combined with data and analysis from several other studies to examine this potential. The results suggest that urban trees and wood waste offer a modest amount of biomass that could contribute significantly more to regional and national bio-economies than it does at present. Better utilization of biomass from urban trees and wood waste could offer new sources of locally generated wood products and bio-based fuels for power and heat generation, reduce fossil fuel consumption, reduce waste disposal costs and reduce pressure on forests. Although wood biomass generally constitutes a “carbon-neutral” fuel, burning rather than burying urban wood waste may not have a net positive effect on reducing atmospheric CO₂ levels, because it may reduce a significant long term carbon storage pool. Using urban wood residues for wood products may provide the best balance of economic and environmental values for utilization.     

Assessment of coal and biomass to liquid fuels in central Appalachia,USA

Liquid fuels from coal and biomass have the potential to reduce petroleum fuel consumption and CO₂ emissions. A multi‐equation model was developed to assess the economics of a potential coal/biomass‐to‐liquids (CBTL) fuel plant in the central Appalachian hardwood region, USA. The model minimizes the total annual production cost subject to a series of regional supply, demand, and other constraints. Model inputs include coal and biomass availability, biomass handling system, plant investment, production capacity, transportation logistics, and project financing. The outputs include the required selling price (RSP) and the optimal logistical decision‐making associated with feedstock requirement, collection, delivery, and liquid fuel production. Results showed that the RSP of Fischer–Tropsch (FT) diesel for a 40 000 barrel‐per‐day CBTL plant with coal/biomass ratio (by weight) of 85/15 was $86.45–87.25 bbl^?1 using different biomass handling systems. The RSP would vary between $86.45 and $89.81 per barrel according to different coal/biomass mix ratios. In consideration of the carbon offset credits due to the addition of biomass, the RSP was adjusted to $84.19–86.74 with respect to four levels of carbon prices. Sensitivity analyses indicated that the RSP of FT diesel was mostly affected by plant capacity, capital cost, coal price, and liquid fuel yield. The crude‐oil‐equivalent price of FT fuels must be above $66 bbl^?1 for a CBTL plant to be profitable in central Appalachia for the long run. These results can help investors/decision‐makers evaluate future CBTL developments in the region. Copyright © 2011 John Wiley & Sons, Ltd.     

Project ARBRE: Lessons for bio-energy developers and policy-makers

Project Arable Biomass Renewable Energy (ARBRE) was a ‘flagship’ project in the UK to demonstrate electricity generation from dedicated energy crops, employing the high efficiency of gasification combined cycle technology while also contributing to the waste management problem of sewage disposal. The plant never reached commercial operation and this paper provides the first detailed public account of the reasons, drawing on interviews with the main actors. Project ARBRE failed due to three unfortunate developments: the withdrawal for reasons of commercial strategy of the main company that initiated and financed the project; bankruptcy of the turnkey contractor appointed to oversee the project; and technical problems with the gasification technology, which could not be resolved within the financial and time constraints. All these factors acted in reinforcing manner and they were individually preventable: documenting the process of failure is a learning experience that can prevent their recurrence.     

Implementation of the biomass gasification project for community empowerment at Melani village, Eastern Cape, South Africa

Eskom and the University of Fort Hare are engaged in a biomass gasification project using the System Johansson Biomass gasifier (SJBG). The SJBG installed at Melani village in the Eastern Cape province of South Africa is used to assess the viability and affordability of biomass gasification in South Africa. A community needs assessment study was undertaken at the village before the installation of the plant. The study revealed the need for low-cost electricity for small businesses including growing of crops, chicken broilers, manufacturing of windows and door frames, sewing of clothing, bakery etc. It was also found that the community had a problem with the socio-environmental aspects of burning biomass waste from the sawmill furnace as a means of waste management. The SJBG uses the excess biomass materials (waste) to generate low-cost electricity to drive community economic development initiatives. A study on the properties and suitability of the biomass materials resulting from sawmill operation and their suitability for gasification using the SJBG was undertaken. The study established that the biomass materials meet the requirements for the SJBG. A 300 Nm³/h SJBG was then manufactured and installed at the village.     

An applied methodology for assessment of the sustainability of biomass district heating systems

In order to maximise the share of biomass in the energy supplying system, the designers should adopt the appropriate changes to the traditional systems and become more familiar with the design details of the biomass heating systems. The aim of this study is to present the development of methodology and its associated implementation in software that is useful for the design of biomass thermal conversion systems linked with district heating (DH) systems, taking into consideration the types of building structures and urban settlement layout around the plant. The methodology is based on a completely parametric logic, providing an impact assessment of variations in one or more technical and/or economic parameters and thus, facilitating a quick conclusion on the viability of this particular energy system. The essential energy parameters are presented and discussed for the design of biomass power and heat production system which are in connection with DH network, as well as for its environmental and economic evaluation (i.e. selectivity and viability of the relevant investment). Emphasis has been placed upon the technical parameters of biomass logistics, energy system's design, the economic details of the selected technology (integrated cogeneration combined cycle or direct combustion boiler), the DH network and peripheral equipment (thermal substations) and the greenhouse gas emissions. The purpose of this implementation is the assessment of the pertinent investment financial viability taking into account the available biomass feedstock, the economical and market conditions, and the capital/operating costs. As long as biomass resources (forest wood and cultivation products) are available and close to the settlement, disposal and transportation costs of biomass, remain low assuring the sustainability of such energy systems.     

Assessment of integration of different biomass gasification alternatives in a district-heating system

With increasingly stringent CO₂ emission reduction targets, incentives for efficient use of limited biomass resources increase. Technologies for gasification of biomass may then play a key role given their potential for high electrical efficiency and multiple outputs; not only electricity but also bio transport fuels and district heat. The aim of this study is to assess the economic consequences and the potential for CO₂ reduction of integration of a biomass gasification plant into a district-heating (DH) system. The study focuses on co-location with an existing natural gas combined cycle heat and power plant in the municipal DH system of Göteborg, Sweden. The analysis is carried out using a systems modelling approach. The so-called MARTES model is used. MARTES is a simulating, DH systems supply model with a detailed time slice division. The economic robustness of different solutions is investigated by using different sets of parameters for electricity price, fuel prices and policy tools. In this study, it is assumed that not only tradable green certificates for electricity but also tradable green certificates for transport fuels exist. The economic results show strong dependence on the technical solutions and scenario assumptions but in most cases a stand-alone SNG-polygeneration plant with district-heat delivery is the cost-optimal solution. Its profitability is strongly dependent on policy tools and the price relation between biomass and fossil fuels. Finally, the results show that operation of the biomass gasification plants reduces the (DH) system's net emissions of CO₂.