Greenhouse gas emissions of bioenergy from agriculture compared to fossil energy for heat and electricity supply

Increasing the use of bioenergy is one promising option to reduce greenhouse gas emissions. Hence it is important to know the greenhouse gas emissions of bioenergy systems in comparison to fossil fuel systems. A life cycle analyses of biomass and fossil fuel energy systems is made to compare the overall greenhouse gas emission of both systems for heat and electricity supply. Different bioenergy systems to supply electricity and heat from agriculture are analysed for the Austrian situation in 2000. Total emissions of greenhouse gases (CO₂, N₂O, CH₄) along the fuel chain, including land use change and by-products, are calculated. The systems taken into consideration are different conversion technologies and different fuels from agriculture. The methodology was developed within the International Energy Agency (IEA) Bioenergy Task 25 on `Greenhouse Gas Balances of Bioenergy Systems'. In this paper the results of selected bioenergy systems for heat supply and combined supply of electricity and heat shown as emission of CO₂-equivalents per kWh for bioenergy systems in comparison to fossil fuel systems, and as a percentage of CO₂-equivalent reduction. The results demonstrate that some of the bioenergy systems reduce greenhouse gas emission already because of avoided emissions of the reference biomass use and/or because of certain substitution effects of by-products. In general the greenhouse gas emissions of bioenergy systems are lower compared to the fossil systems. Therefore a significant reduction of greenhouse gases is possible by replacing fossil energy systems with bioenergy systems. This comparison should help policy makers, utilities and industry to identify effective agricultural biomass options in order to reach emission reduction targets. This revised version was published online in August 2006 with corrections to the Cover Date.     

A review of the current state of biofuels production from lignocellulosic biomass using thermochemical conversion routes

The rapid increase in energy demand, the extensive use of fossil fuels and the urgent need to reduce the carbon dioxide emissions have raised concerns in the transportation sector. Alternate renewable and sustainable sources have become the ultimate solution to overcome the expected depletion of fossil fuels.The conversion of lignocellulosic biomass to liquid(BtL) transportation fuels seems to be a promising path and presents advantages over first generation biofuels and fossil fuels. Therefore, development of BtL systems is critical to increase the potential of this resource in a sustainable and economic way.Conversion of lignocellulosic BtL transportation fuels, such as, gasoline, diesel and jet fuel can be accomplished through various thermochemical processes and processing routes. The major steps for the production of BtL fuels involve feedstock selection, physical pretreatment, production of bio-oil, upgrading of bio-oil to transportation fuels and recovery of value-added products. The present work is aiming to give a comprehensive review of the current process technologies following these major steps and the current scenarios of biomass to liquid facilities for the production of biofuels.     

Simulation of a Lignite‐Based Polygeneration System Coproducing Electricity and Tar with Carbon Capture

Lignite‐based polygeneration systems for coproducing tar and electricity with and without carbon capture and storage (CCS) were proposed and simulated. Predried lignite was pyrolyzed into coal gas, tar, and char. Coal gas was fired in a gas turbine after the cleanup process, while char was combusted in circulating fluidized‐bed (CFB) boilers. The polygeneration plant without CCS turned out to be more efficient than the conventional CFB power plant, suggesting that the former is a promising and efficient option to utilize lignite resources. Moreover, the performance and emissions of polygeneration plants with and without CCS were compared. It was shown that the more CO₂ is captured, the larger energy penalty it will cost. Therefore, a trade‐off should be made between low emissions and high efficiency.     

Combining coal gasification and natural gas reforming for efficient polygeneration

A techno-economic analysis of several process systems to convert coal and natural gas to electricity, methanol, diesel, and gasoline is presented. For these polygeneration systems, a wide range of product portfolios and market conditions are considered, including the implementation of a CO₂ emissions tax policy and optional carbon capture and sequestration technology. A new strategy is proposed in which natural gas reforming is used to cool the gasifier, rather than steam generation. Simulations along with economic analyses show that this strategy provides increased energy efficiency and can be the optimal design choice in many market scenarios.     

一种煤基多联产碳循环系统的设计及评价

将高密度三塔式循环流化床(TBCFB)应用于串并联综合型多联产系统,提出一种基于碳循环的流程与参数共优化的煤基多联产系统,促进低阶煤资源的高质高效转化。碳循环体现在两方面,一是系统以热解煤气循环作为热解气氛,提高了焦油产率,实现低阶煤高质化转化;二是在TBCFB使用富氧燃烧,提高了烟气中二氧化碳浓度,将烟气替代氮气直接用于燃气轮机发电工质,减少了氮气消耗。利用Aspen Plus对全系统进行模拟,对多联产系统进行物料、能量和?衡算,研究未反应合成气循环比和烟气注入量对过程的影响;以能量利用效率为优化目标,对煤基多联产碳循环系统的操作条件寻优。结果表明,动力单元注入气体使用烟气时,煤基多联产碳循环系统的能量利用效率达49.7%,高于用氮气作为热解气氛的传统煤基多联产系统,相比传统的单产系统,煤基多联产系统的能量可节约13%,对于年处理30万吨煤的系统,折合减少二氧化碳排放量为14.9万吨/年。     

Wind und Kohle: Die technische Photosynthese

The increasing energy demand, the associated CO₂ emissions, and the concurrently decreasing reserves of fossil fuels require new concepts for sustainable energy production. The so‐called Adam‐and‐Eve principle for CO₂‐free production of methanol from coal and nuclear energy is revisited and adapted to today's circumstances. Electrolysis of water using renewable electricity is applied for H₂ production. Simultaneously, coal and the oxygen formed during electrolysis are burned in an oxyfuel process, generating electricity and relatively pure CO₂. Hydrogen from electrolysis and CO₂ are converted to methanol, which can then be used as chemical‐ and energy feedstock.     

双气头多联产中醇醚燃料合成流程的经济评价

采用Aspen Icarus Process Evahator(Aspen IPE)软件对双气头多联产流程中关键工艺段--洁净气化煤气/焦炉煤气合成醇醚燃料单元进行了经济评价,以估算多联产系统中化工产品生产部分的经济性.经济评估计算以焦炭产能5 000 t/a的焦化厂为例,原料气按照气化煤气/焦炉煤气体积比1∶1进行输入,化学品合成工艺按一步法合成二甲醚(386 t/a),副产甲醇(242t/a).应用Aspen IPE软件计算该流程的投资费用、操作费用和利润率,并在此基础上分析了原料和产品价格变化对该项目经济性的影响.     

Optimal design and operation of a steel plant integrated with a polygeneration system

A process integration approach has been applied to integrate a traditional steelmaking plant with a polygeneration system to increase energy efficiency and suppress carbon dioxide emissions from the system. Using short‐cut models and empirical equations for different units and available technologies for gas separation, methane gasification, and methanol synthesis, a mixed integer nonlinear model is applied to find the optimal design of the polygeneration plant and operational conditions of the system. Due to the complexity of the blast furnace (BF) operation, a surrogate model technique is chosen based on an existing BF model. The results show that from an economic perspective, the pressure swing adsorption process with gas‐phase methanol unit is preferred. The results demonstrate that integration of conventional steelmaking with a polygeneration system could decrease the specific emissions by more than 20 percent. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3659–3670, 2013     

A multi‐objective optimization approach to polygeneration energy systems design

Polygeneration, typically involving co‐production of methanol and electricity, is a promising energy conversion technology which provides opportunities for high energy utilization efficiency and low/zero emissions. The optimal design of such a complex, large‐scale and highly nonlinear process system poses significant challenges. In this article, we present a multiobjective optimization model for the optimal design of a methanol/electricity polygeneration plant. Economic and environmental criteria are simultaneously optimized over a superstructure capturing a number of possible combinations of technologies and types of equipment. Aggregated models are considered, including a detailed methanol synthesis step with chemical kinetics and phase equilibrium considerations. The resulting model is formulated as a non‐convex mixed‐integer nonlinear programming problem. Global optimization and parallel computation techniques are employed to generate an optimal Pareto frontier. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Combined Decarbonization of Electrical Energy Generation and Production of Synthetic Fuels by Renewable Energies and Fossil Fuels

Power generation from renewable energy sources and fossil fuels are integrated into one system. A combination of technologies in the form of a carbon capture utilization (CCU)-combined power station is proposed. The technology is based on energy generation from fossil fuels by a coal power plant with CO₂ recovery from exhaust gases, and pyrolysis of natural gas to hydrogen and carbon, completed by reverse water-gas shift for the conversion of CO₂ to CO, which will react with hydrogen in a Fischer-Tropsch synthesis for synthetic diesel. The carbon from the pyrolysis can replace other fossil carbon or can be sequestered. This technology offers significant CO₂ savings compared to the current state of technology and makes an environmentally friendly use of fossil fuels for electricity and fuel sectors possible.     

双气头多联产系统的Aspen Plus实现及工艺过程优化(Ⅰ) 模拟流程的建立及验证

通过流程模拟对煤基多联产系统进行过程优化是一种低成本、高效率的研究方法。通过稳态流程模拟软件Aspen Plus建立了二甲醚和电力为主要目标产品并副产甲醇的煤基多联产系统流程。采用气化煤气与焦炉煤气混合气作为气头,以达到利用焦炉煤气中高浓度甲烷、下一步工艺调整氢碳比并实现温室气体减排的目的。模拟流程中包括了空分、煤气化及净化、CH4/CO2重整、产品合成、燃气轮机联合循环发电等多联产系统中的5个主要工艺单元,涉及化学反应的CH4/CO2重整单元和二甲醚合成单元通过嵌入包含特定反应动力学参数的动力学子程序进行模拟。多联产系统综合考虑了化学反应的动力学和热力学,系统总体及各工艺单元物料、能量衡算一致,各个单元模拟数据与文献实验数据吻合。在建立流程的基础上,计算比较了热值加和效率与当量发电效率,发现考虑能量品质的当量发电效率更适合联产液体燃料和电能的多联产系统的评价。     

Economic viability of the use of olive tree pruning as fuel for heating systems in public institutions in South Spain

Biomass from olive tree pruning could be used as fuel for heating systems in boiler, thus helping to mitigate CO₂ emissions and reducing the dependence on fossil fuels. It also helps to reap secondary benefits, such as the creation of employment in rural areas. In the present study, an economic viability analysis about the use of olive tree pruning as fuel for heating systems in public schools of Lucena (Andalusia, Spain) have been carried out. This town has been selected due to its proximity to olive tree plantations. The heat cost calculations were based on the standard VDI 2067. Eventually, a sensitivity analysis to assess the effect of prices variation over the time needed to recover the investment has been carried out. It can be concluded that, in many cases, subsidies are needed to promote modern biomass technologies, to compensate for non-internalized external costs of fossil fuel systems. In case a subsidy up to 50% of the investment is applied, payback is reduced, thus biomass boiler using olive tree chips is strongly recommended. Energy cost using olive tree chips is highly dependent on the high variability of the boilers working period. In all case studies, based on the sensitivity analysis, a maximum radius of 5 km of olive trees cuttings is enough to feed the public school boilers of the town. Also, it can be seen that the cost of energy considering either olive tree chips or olive pits is similar.     

Thermogravimetric study of the pyrolysis of biomass residues from tomato processing industry

There is an increasing concern with the environmental problems associated with the increasing CO₂, NO_x and SO_x emissions resulting from the rising use of fossil fuels. Renewable energy, mainly biomass, can contribute to reduce the fossil fuels consumption. Biomass is a renewable resource with a widespread world distribution. Tomato processing industry produces a high amount of biomass residue (peel and seeds) that could be used for thermal energy and electricity. A characterization and thermogravimetric study has been carried out. The residue has a high HHV and volatile content, and a low ash, and S contents. A kinetic model has been developed based on the degradation of hemicellulose, cellulose, lignin and oil that describe the pyrolysis of peel, seeds and peel and seeds residues.     

中国化石能源生产的生命周期清单(Ⅰ)--能源消耗与直接排放

化石能源生产的生命周期清单不仅是开展化工产业及其产品生命周期分析的基础,也能阐明化石能源生产的基本环境行为.通过计算得到了2002年我国原煤、原油和天然气开采过程中直接相关的能源消耗和污染物排放,涉及到的污染物排放包括液态污染物、固体废弃物和CO2、SO2、NOx、CO、CH4、烟尘等气态排放物.     

Linking renewables and fossil fuels with carbon capture via energy storage for a sustainable energy future

Renewable energy sources and low-carbon power generation systems with carbon capture and storage (CCS) are expected to be key contributors towards the decarbonisation of the energy sector and to ensure sustainable energy supply in the future. However, the variable nature of wind and solar power generation systems may affect the operation of the electricity system grid. Deployment of energy storage is expected to increase grid stability and renewable energy utilisation. The power sector of the future, therefore, needs to seek a synergy between renewable energy sources and low-carbon fossil fuel power generation. This can be achieved via wide deployment of CCS linked with energy storage. Interestingly, recent progress in both the CCS and energy storage fields reveals that technologies such as calcium looping are technically viable and promising options in both cases. Novel integrated systems can be achieved by integrating these applications into CCS with inherent energy storage capacity, as well as linking other CCS technologies with renewable energy sources via energy storage technologies, which will maximise the profit from electricity production, mitigate efficiency and economic penalties related to CCS, and improve renewable energy utilisation.     

Reduction of greenhouse gas emissions via flexible operation of cross-sector integrated energy systems under uncertainties in demand,fuel prices,and solar irradiation

This work investigates how the flexible operation of the light industrial plants integrated in a cross-sector energy cluster with community energy systems can achieve further greenhouse gas (GHG) reductions under uncertainties associated with natural gas prices, solar irradiation, as well as heating, cooling, and electricity demand. The optimal flexible operation and design of a cross-sector integrated cluster comprising a bakery plant, a brewery, a confectionery plant, a residential building, and a supermarket under uncertainties are compared to the operation and design of systems without uncertainties. When uncertainties are considered, the overall GHG emissions of the integrated system with steady industrial production rates for all uncertainty scenarios are over 4% higher than the integrated system in the deterministic scenario (a single scenario). Flexible operation of the industrial plants, whereby production rates are varied throughout the day, contributes an additional 3% reduction in GHG emissions under uncertainties, where the GHG emissions are only 1% higher than the deterministic scenario. Additionally, the system with flexible production rates purchases over 14.3% less electricity from the grid and uses over 72.2% less natural gas for operating the backup boiler, which relies less on supplementary energy resources. This shows that optimally designed integrated systems with flexible industry production schedules are resilient to uncertainties in energy demands, daily weather fluctuations, and fuel prices.     

500t/d预燃炉系统在水泥厂的应用实践

为响应国家推进循环经济发展和节能减排的相关政策，我公司决定对现有水泥生产线进行节能降碳，采用500 t/d空气脉动预燃炉技术将生活垃圾的水泥资源化系统改造升级，提高替代燃料使用量，进一步降低生产成本、减少碳排放，提高公司绿色发展能力。实践证明，系统改造后在处理500 t/d替代燃料的情况下，烧成系统的标煤耗可下降至83.73 kg/t，且对水泥窑生产无其它不利影响，实现了经济效益和社会效益双丰收。     

Cogeneration in integrated first and second generation ethanol from sugarcane

Sugarcane bagasse and trash are used as fuels in cogeneration systems for bioethanol production, supplying steam and electricity, but may also be used as feedstock for second generation ethanol. The amount of surplus lignocellulosic material used as feedstock depends on the energy consumption of the production process; residues of the pretreatment and hydrolysis operations (residual cellulose, lignin and eventually biogas from pentoses biodigestion) may be used as fuels and increase the amount of lignocellulosic material available as feedstock in hydrolysis. The configuration of the cogeneration system (boiler pressure, lignocellulosic material consumption and steam production, turbines efficiencies, among others) has a significant impact on consumption of fuel and electricity output; in the integrated first and second generation, it also affects overall ethanol production. Simulations of the integrated first and second generation ethanol production processes were carried out using Aspen Plus, comparing different configurations of the cogeneration systems and pentoses use (biodigestion and fermentation). Economic analysis shows that electricity sale can benefit second generation ethanol, even in relatively small amounts. Environmental analysis shows that the integrated first and second generation process has higher environmental impacts in most of the categories evaluated than first generation.     

Process analysis for polygeneration of Fischer-Tropsch liquids and power with CO2 capture based on coal gasification

This paper designs four cases to investigate the performances of the polygeneration processes, which depend on the commercially ready technology to convert coal to liquid fuels (CTL) and electricity with CO₂ sequestration. With Excel-Aspen Plus based models, mass and energy conversion are calculated in detail. The simulation shows that the thermal efficiency is down with the synfuels yield decrease though the electricity generation is increased. It also suggests that the largest low heat value (LHV) loss of coal occurs in the gasification unit. From the comparison of the four cases, prominent differences of coal energy transition appear in water-gas shift (WGS) units, Fischer-Tropsch (FT) synthesis and combined cycle processes. CO₂ capture and vent are discussed and the results show that the vent amount of CO₂ increases with the increase of percentage of the syngas going to produce electricity. The results also show that the ratio of carbon captured to total carbon increases from 58% to 93% which is an important contribution to cutting down the greenhouse gas vent.