Assessment of bioenergy production from mid-rotation thinning of hardwood plantation: life cycle assessment and cost analysis

Forestry thinning logs, a low-value by-product of the forestry industry, present an opportunity for bioenergy production. It can be converted into solid, liquid, and gaseous fuels via different conversion techniques. Comparative life cycle assessment and life cycle costing (LCC) analysis were conducted to evaluate six options: woodchip gasification for power generation; wood pellets gasification in combined heat and power plant; wood pellet combustion for domestic water and space heating; pyrolysis for power generation; pyrolysis with bio-oil upgrading to transportation fuels; and ethanol production for transportation fuel mix. The functional unit used in this study was the treatment of 1 Mg of biomass. Global warming; acidification; eutrophication; fossil depletion, human toxicity; and land use impact categories were considered. The LCC also included greenhouse gas (GHG) emissions costs. The effects of uncertainties in the system on the overall performance of the scenarios were also evaluated. The results showed that all options except for ethanol production are GHG emission negative. Woodchips gasification performed best in all environmental impact categories and had the lowest LCC ($177.6/Mg). Biomass drying consumed more than 50% of the energy requirement for all options except for production of liquid transportation fuels via upgrading of pyrolytic oil, in which case the fuel upgrading process was the most energy intensive. In terms of energy return, all options, except electricity production through pyrolysis, offered positive return. The results highlight the importance of using biomass with least possible processing in order to maximise environmental and energy return and minimise LCC.     

A life cycle assessment of biomass cofiring in a coal-fired power plant

The generation of electricity, and the consumption of energy in general, often result in adverse effects on the environment. Coal-fired power plants generate over half of the electricity used in the U.S., and therefore play a significant role in any discussion of energy and the environment. By cofiring biomass, currently operating coal plants have an opportunity to reduce the impact they have, but to what degree, and with what trade-offs? A life cycle assessment has been conducted on a coal-fired power system that cofires wood residue. The assessment was conducted in a cradle-to-grave manner to cover all processes necessary for the operation of the power plant, including raw material extraction, feed preparation, transportation, and waste disposal and recycling. Cofiring was found to significantly reduce the environmental footprint of the average coal-fired power plant. At rates of 5% and 15% by heat input, cofiring reduces greenhouse gas emissions on a CO₂-equivalent basis by 5.4% and 18.2%, respectively. Emissions of SO₂, NO _x , non-methane hydrocarbons, particulates, and carbon monoxide are also reduced with cofiring. Additionally, total system energy consumption is lowered by 3.5% and 12.4% for the 5% and 15% cofiring cases, respectively. Finally, resource consumption and solid waste generation were found to be much less for systems that cofire. Electronic Publication     

Availability analysis of integrated gasification combined cycle power plants with backup fuel and NOx reduction

Backup fuel can be utilised to improve the effectiveness (energy availability) of an integrated gasification combined cycle power plant. The gas turbine can be operated independently, also, with a backup fuel. By independent operation, the selective catalytic reduction (SCR), which is installed in the heat recovery steam generator for lower NO_x, emission is bypassed and a relatively high level of NO_x is emitted. Improving the effectiveness of a power plant by using backup fuel involves increased cost for backup fuel and higher NO_x emission.The object of this paper is to improve the effectiveness of a power plant with a minimum of backup fuel and NO_x emissions.The study shows how the application of appropriate reserve capacity (active redundancy) and a suitable repair policy can minimize the use of backup fuel and NO_x emissions, and, at the same time, improve the effectiveness of integrated gasification combined cycle power plants.     

Minimization of life cycle CO2 emissions in steam and power plants

A methodology is presented to minimize life cycle CO₂ emissions through the selection of the operating conditions of a steam and power generation plant. The battery limits of the utility plant are extended to include CO₂ emissions of: (1) extraction and transport of natural gas burned in its boilers, (2) generation of imported electricity by nuclear, hydroelectric and thermoelectric plants and (3) exploration, extraction and transport of natural gas, oil, coal and uranium consumed by thermoelectric and nuclear plants. The operating conditions of the utility plant are selected optimally to minimize the life cycle CO₂ emissions. There are continuous operating conditions such as temperature and pressure of the high, medium and low pressure steam headers and binary operating conditions to represent discrete decisions to select optional pumps drivers between electrical motors and steam turbines or whether some equipment is on or off. A Mixed Integer Nonlinear Programming problem is formulated and solved in GAMS. Significant reductions in life cycle CO₂ emissions, natural gas consumption and operating cost are achieved simultaneously in the steam and power generation system of an ethylene plant. This is an important tool to support a decision making process to reduce CO₂ emissions in a key industrial sector. An erratum to this article can be found at     

Multi-objective optimization of steam power plants for sustainable generation of electricity

A unified framework that combines process simulation and multi-objective optimization is presented to simultaneously maximize the annual profit, while minimizing environmental impact (i.e., greenhouse gas emissions) of steam power plants with fixed flowsheet structures. The proposed methodology includes the selection of suitable primary energy sources (i.e., fossil fuels, biomass, biofuels, and solar energy) for sustainable electricity generation. For solving the problem of optimal selection of energy sources, a linear model is developed and included within a highly nonlinear simulation model for the parameter optimization of steam power plants that is solved by using genetic algorithms. This approach is robust and avoids making discrete decisions. Life cycle assessment technique is used to quantify the greenhouse gas emissions resulting from different combinations of energy sources and operating conditions of the power plants. The thermodynamic properties for liquid water and steam are calculated rigorously using the IAPWS-IF 97 formulation. An example problem of an advanced regenerative-reheat steam power plant is presented to illustrate the proposed method, which provides the Pareto optimal solutions, the types and amounts of primary energy sources as well as the optimal values of the operating conditions of the plant that simultaneously maximize the profit while minimizing environmental impact.     

An optimization model under interval and fuzzy uncertainties for a by-product gas system of an iron and steel plant

The effective utilization of by-product gas is essential for achieving the targets of energy conservation and emission reduction of iron and steel plants in China. The application of deterministic optimization methods may lead to oversimplification and inaccurate estimation of system parameters, and even to system failure. The major contributions made by this study are the development of a gas scheduling optimization model under fuzzy and interval uncertainties and it application to the gas scheduling system of the Baotai steel plant. The integration of type-1 and type-2 fuzzy sets and interval numbers was first used to describe specific model parameters, and the reduced fuzzy chance-constrained programming algorithm and interactive two-step interval algorithm were used for model solution. Compared with practical allocation patterns, it is shown that the proposed model could offer better solutions with more outstanding performance in rapid response to production fluctuations, as well as increases in system revenue.     

生命周期内混合动力燃气热泵碳排放研究

采用生命周期评价的方法,针对一种混合动力燃气热泵系统在全生命周期的碳排放进行了评估。基于生命周期（LCA）评价理论,确定了系统边界,建立了系统生命周期内碳排放核算模型。得到了系统在生产阶段、运输安装阶段、运行阶段和回收利用阶段的碳排放当量。结果表明:系统在运行使用阶段CO2-eq排放量最大,为35387.6kg,大约占据了整个生命周期的84％,主要来源为电力和天然气的使用; 生产安装阶段CO2-eq排放量次之,约为6187kg,运输安装及废弃阶段碳排放量很小,几乎可以忽略。因此,要降低系统在全生命周期中的温室气体排放量,应重点放在对电力和天然气的合理使用和新能源的开发上。对比分析了其与单独电力驱动热泵在全生命周期内的碳排放量。分析结果表明:在全生命周期内,混合动力燃气热泵与单独电力驱动热泵相比碳减排量约为20430.9kg。最后,进一步讨论了系统的碳减排方法和减排潜力。     

Cost-effective GHG mitigation strategies for Western Australia’s housing sector: a life cycle management approach

The demand of natural resources for Western Australia’s (WA) housing sector is increasing due to economic and population growth, which will be a challenging task for Australia to achieve its GHG reduction target. This paper has assessed possible GHG mitigation options for Western Australia’s houses, where energy-intensive clay brick walls and single-glazed windows are currently being used. A life cycle management framework has been used to determine cost-effective GHG emissions mitigation strategies. This framework integrates life cycle assessment tool, energy rating tool (AccuRate), and life cycle cost (LCC) analysis in order to ascertain environmentally and economically viable alternative building envelop for constructing a house in WA. The results show that the house made of cast in situ sandwich walls, recycled core materials and double-glazed windows, and equipped with solar energy system for electricity and water heating is the best option. This option has life cycle GHG emissions and LCC saving potentials of 7 and 20 %, respectively.     

Decomposition and decoupling analysis of electricity consumption carbon emissions in China

Electricity consumption is one of the major contributors to greenhouse gas emissions. In this study, we build a power consumption carbon emission measurement model based on the operating margin factor. We use the decomposition and decoupling technology of logarithmic mean Divisia index method to quantify six effects (i.e., emission intensity, power generation structure, consumption electricity intensity, economic scale, population structure, and population scale) and comprehensively reflect the degree of dependence of electricity consumption carbon emissions on China’s economic development and population changes. Moreover, we utilize the decoupling model to analyze the decoupling state between carbon emissions and economic growth and identify corresponding energy efficiency policies. The results of this study provide a new perspective to understand carbon emission reduction potentials in the electricity use of China.     

Regional demand-pull scenarios and cost-effective emission mitigation

All Organizations including Kyoto Protocol (KP), the United Nations Framework Convention on Climate Change (UNFCCC), etc. advocate for clean technologies of low-, non-, and zero-emissions as key to the cost-effective emission mitigation from the regional energy system. Under the aforementioned premise, this work developed and tested some demand-pull scenarios for India and China on its most emission intensive sectors (i.e., electricity, iron and steel, and cement productions). DNE21+ model is used to carry out this research on least cost approach for a time period of 30 years (2000–2030). We found that the demand-pull scenarios are not cost-effective for abating the emissions of a regional energy system inside a multi-regional global energy system model. This article elaborates the ineffectiveness of technology pull in addressing cost-effective emission mitigation and provides broader outlook to overcome the problems of higher mitigation costs above the average value.     

Emission constrained power system planning: a pinch analysis based study of Indian electricity sector

In the light of rising electricity demands and a need to curb carbon dioxide emissions, this article investigates the problem of power system planning with emission targeting. A pinch analysis based approach is utilised here. The key aspect of this study is investigating the parameters that decide the priority of one type of power plant over another. For this, a quantity called prioritised cost, a trade off between cost incurred and emission from a new power plant is identified. In addition to cost and emission factor of a power plant, a third parameter, the present state of the system, also plays a significant role in deciding a power plant’s prioritised cost. The analysis done proves that new power plants can be added to the system in the order of their prioritised cost. This methodology is applied to Indian power sector as a case study. Two different problems, involving minimisation of investment and annualised cost, are considered. It is observed that renewables are slightly more favoured when the objective is to minimise overall cost and not just the capital investment. In both cases, the energy mix is still dominated by coal-based power generation. The share of renewables was seen to increase with more stringent emission targets when the objective was to minimise overall cost.     

Coping with carbon: a near-term strategy to limit carbon dioxide emissions from power stations

Burning coal to generate electricity is one of the key sources of atmospheric carbon dioxide emissions; so, targeting coal-fired power plants offers one of the easiest ways of reducing global carbon emissions. Given that the world's largest economies all rely heavily on coal for electricity production, eliminating coal combustion is not an option. Indeed, coal consumption is likely to increase over the next 20-30 years. However, the introduction of more efficient steam cycles will improve the emission performance of these plants over the short term. To achieve a reduction in carbon emissions from coal-fired plant, however, it will be necessary to develop and introduce carbon capture and sequestration technologies. Given adequate investment, these technologies should be capable of commercial development by ca 2020.     

A systematic technique for cost-effective CO<Subscript>2</Subscript> emission reduction in process plants

There has been growing interests to reduce the environmental impact caused by greenhouse gas emissions from process plants through various energy conservation strategies. CO₂ emissions are closely linked to energy generation, conversion, transmission and utilisation. Various studies on the design of energy-efficient processes, optimal mix of renewable energy and hybrid power system are driven to reduce reliance on fossil fuel as well as CO₂ emissions reduction. This paper presents a systematic technique in the form of graphical visualisation tool for cost-effective CO₂ emission reduction strategies in industry. The methodology is performed in four steps. The first step involves calculating the energy consumption of a process plant. This is followed by identification of potential strategies to reduce CO₂ emissions using the CO₂ management hierarchy as a guide. In the third step, the development of “Investment” versus “CO₂ Reduction” (ICO₂) plot is constructed to measure the optimal CO₂ emission reductions achieved from the implementation of possible CO₂ reduction strategies. The Systematic Hierarchical Approach for Resilient Process Screening (Wan Alwi and Manan in AIChE J 11:3981–3988, 2006) method is used in the fourth step via substitution or partial implementation of the various CO₂ reduction options in order to meet the cost-effective emission reduction within the desired investment limit or payback period (PP). An illustrative case study on a palm oil refinery plant has been used to demonstrate the implementation of the method in reduction of CO₂ emissions. The developed graphical tool provides an insight-based approach for systematic CO₂ emission reduction in the palm oil refinery considering both heat and power energy sources. Result shows that 31.2 % reduction in CO₂ emissions can be achieved with an investment of USD 38,212 and PP of 10 months based on the present energy prices in Malaysia.     

Steel mill slags energy potential: the case of the steel factory of Arcelor-Mittal in Asturias (Spain)

Slag accounts for most of the residuals or by-products of the steel manufacturing process and represents a not inconsiderable amount of energy waste and CO₂ emissions. Energy recovery from steel mill slags is not actually performed because of the difficulty of the industrial implementation, but the actual demand and the incentives for new electricity generation plants based on renewable energies and on industrial waste heat recovery offer a new opportunity to evaluate the feasibility of this process. This article presents a review of the slag energy potential on a global scale, and a proposal for a recovery plant in the factories of Arcelor-Mittal in Asturias (Spain), based on a steam Rankine cycle for electricity production in a turbine. The plant production and viability have been analyzed using the typical technical and economic values for this kind of plant. Also, a parametric study has been performed on the heat recuperator efficiency and investment rate.     

Impact of renewable energy on rural electrification in Malaysia: a review

Malaysia is rich in renewable energy (RE) resources. Hybrid systems of these resources can contribute strongly to the electrification and sustainable development of rural areas that do not have access to electricity grids. The integration of the generation of hybrid renewable power in remote and rural areas supplies the required power demand and mitigates emissions. Thus, this study reviews the latest literature (theses, journals articles, and conference proceedings) on the need for electricity in remote rural communities, on hybrid RE systems, on environmental impact, and on economic regulation in Malaysia. Power in this country is mainly generated by fossil fuels that emit high concentrations of greenhouse gases. Thus, RE is a potential alternative for to electrify rural areas, to meet current and future energy demands, and to mitigate emissions. Moreover, Malaysia has pledged to reduce its carbon-emission intensity by a maximum of 40 % (2005 level) by the year 2020. Therefore, the implementation of RE technologies in this country is significantly aided by RE projects, research and development activities, technologies, energy policies, and future direction. This review concludes that solar, wind, hydro, and biomass energy, as well as a hybrid of these, can effectively electrify rural areas.     

Impact of including land-use change emissions from biofuels on meeting GHG emissions reduction targets: the example of Ireland

The greenhouse gases (GHG) emissions from land-use change are of particular concern for land-based biofuels. Emissions avoided by substituting fossil fuels with biofuels may be offset by emissions from direct and indirect land-use changes (LUC). There is an urgent need to investigate what impact land-use change emissions may have on the expansion of bioenergy and biofuels, in the context of EU mitigation policies. This paper focuses on Ireland, which faces a number of challenges in delivering its renewable energy and GHG reduction targets. The Irish TIMES energy systems model was used to assess the impact of a range of land-use change emissions’ levels on the evolution of Ireland’s low-carbon energy system. A reference scenario was developed where LUC is ignored and Ireland achieves a least-cost low-carbon energy system by 2050. If high indirect land-use change (ILUC) emissions are included, this results in a decrease by 30 % in bioenergy and a 68 % increase in marginal abatement costs by 2050. Hydrogen is used instead of bioenergy in the freight sector in this scenario, while private cars are fuelled by renewable electricity. If GHG emissions from ILUC were considered less severe, indigenous grass biomethane becomes the key biofuel representing 31 % of total bioenergy consumption. This is in line with recent research in Ireland of the key role that grass biomethane can play.     

基于Agent-CET模型的电力企业碳减排交易机制研究

研究电力行业碳排放交易有利于解决电力市场交易的协调和模拟问题,有助于完善和指导我国碳排放交易（CET）制度。分析了CET制度对电力企业碳排放量的影响,定义了电力市场和碳排放权交易市场各交易商Agent的角色和功能,并构建了基于Agent的CET模型,从发电技术转化、碳排放权交易和相关市场模拟3方面开展了CET模型的实施研究。结果表明,基于Agent的CET模型比传统的建模方法更具优势,通过综合考量市场参与者的风险偏好、期望、参与时间等要素,能够将单一的电力市场和碳排放权交易市场联系起来形成多市场、多代理模拟,从而促进电力企业科学评估电力市场各主体策略的动态调整和碳交易状况。     

Life cycle assessment framework for asphalt pavements: methods to calculate and allocate energy of binder and additives

The construction, maintenance and disposal of asphalt pavements may lead to considerable environmental impacts, in terms of energy use and emissions during the life of the pavement. In order to enable quantification of the potential environmental impacts due to construction, maintenance and disposal of roads, an open life cycle assessment (LCA) framework for the asphalt pavements is presented in this paper. Emphasis was placed on the calculation and allocation of energy used for binder and additives at the project level. It was concluded from this study that when progressing from LCA to its corresponding life cycle cost, the feedstock energy of the binder becomes highly relevant as the cost of the binder will be reflected in its alternative value as fuel. Regarding additives like wax, a framework for energy allocation was suggested. The suggested project level LCA framework was demonstrated in a limited case study of a Swedish asphalt pavement. It was concluded that the asphalt production and transporting materials were the two most energy-consuming processes, emitting most greenhouse gases depending on the fuel type and electricity mix.     

Electricity generation: options for reduction in carbon emissions

Historically, the bulk production of electricity has been achieved by burning fossil fuels, with unavoidable gaseous emissions, including large quantities of carbon dioxide: an average-sized modern coal-burning power station is responsible for more than 10 Mt of CO(2) each year. This paper details typical emissions from present-day power stations and discusses the options for their reduction. Acknowledging that the cuts achieved in the past decade in the UK CO(2) emissions have been achieved largely by fuel switching, the remaining possibilities offered by this method are discussed. Switching to less-polluting fossil fuels will achieve some measure of reduction, but the basic problem of CO(2) emissions continues. Of the alternatives to fossil fuels, only nuclear power represents a zero-carbon large-scale energy source. Unfortunately, public concerns over safety and radioactive waste have still to be assuaged. Other approaches include the application of improved combustion technology, the removal of harmful gases from power-station flues and the use of waste heat to improve overall power-station efficiency. These all have a part to play, but many consider our best hope for emissions reduction to be the use of renewable energy. The main renewable energy contenders are assessed in this paper and realistic estimates of the contribution that each could provide are indicated. It appears that, in the time-scale envisaged by planners for reduction in CO(2) emission, in many countries renewable energy will be unlikely to deliver. At the same time, it is worth commenting that, again in many countries, the level of penetration of renewable energy will fall short of the present somewhat optimistic targets. Of renewable options, wind energy could be used in the short to medium term to cover for thermal plant closures, but for wind energy to be successful, the network will have to be modified to cope with wind's intermittent nature. Globally, hydroelectricity is currently the largest developed source of renewable electricity, but future large-scale projects will probably be limited to the less-developed world: the best schemes in the developed countries have already been exploited. Wave and tidal can be looked on as medium- to long-term generators of electricity, as their respective industries are not as mature as competing renewable resources. Municipal solid-waste combustion and landfill gas technologies can also be seen as short term, as can their rural equivalents, agriculture and forestry waste. Any widespread exploitation of renewable energy will depend on being able to transmit the energy from source to point of use, so the implications for the electrical network from the penetration of substantial levels of renewable energy are presented. Effective management of renewable energy installations will require technical assessment of the range of exploitation strategies, to compare local production of, say, hydrogen and the more traditional transmission of electricity. Such resources will have to compete with others in any national, or grid, system and detailed economic analysis will be necessary to determine the deployment that best fits the trading regime under which the energy will be sold. Consideration will also be necessary to determine how best to control the introduction of this radically new resource such that it does not attract punitive cost overheads until it is mature enough to cope. Finally, it is inescapable that nuclear power is a proven technology that could take its place in any future generation portfolio. Unfortunately, suspicion and mistrust surround waste management and radioactivity release. Unless this is overcome, the lack of confidence engendered by this public mistrust may result in few, if any, new nuclear power stations being built. In the event of that decision, it is difficult to see how CO(2) levels can be significantly reduced: the irony is that nuclear energy may emerge as environmentally essential.     

On the activation strategy of the chiller in water-loop self-contained refrigeration systems: An experimental analysis

Supermarkets require considerable amount of electricity and gas for refrigeration and maintenance of comfortable retail environment conditions. They are also responsible for a large amount of both direct and indirect CO₂ emissions. Nowadays advanced refrigeration systems for supermarkets can reduce both annual energy consumption and total equivalent warming impact. One of these advanced solutions is the water-loop self-contained refrigeration system, where the thermal power of each cabinet is rejected to a fluid-loop, refrigerated either by a dry-cooler or by a central chiller. In this study the performances of a real water-loop self-contained plant are analyzed to establish whether the activation of the water-loop chiller is energy effective or not varying the external air temperature. The activation strategy of the chiller is a crucial issue, which dramatically affects the energy performances of the whole system.