基于全生命周期地热发电系统的环境影响评价

为明确不同类型地热发电系统"获取、转化"环节的钻井、建设、运行、退役等不同过程对地热发电系统的环境影响贡献,建立了基于热力学优化模型的闪蒸/双工质地热发电系统全生命周期环境影响评价模型。针对西藏羊八井、广东丰顺、华北油田及青海共和四种典型地热热储,调研了我国地热发电系统的环境影响全生命周期的环境影响清单,分析地热发电站六个不同过程对地热电站酸化潜值、全球变暖潜值和富营养化潜值三个主要环境影响评价指标的影响规律。发现钻井完井过程分别平均占到地热电站酸化潜值、全球变暖潜值和富营养化潜值的46.28%、45.90%和27.52%,地下系统和地上系统的环境影响贡献相当;地热梯度与地热电站的全生命周期环境影响潜值呈现负相关关系。     

生物质快速热裂解系统生命周期评估

以流化床快速热裂解制取生物油系统为研究对象,确立系统边界,对其进行全生命周期评估,讨论整个系统在全生命周期中的能耗、全球变暖潜值、酸化潜能及其他环境影响潜值。计算得到系统制取生物油在生命周期中的净能量值为0.68 MJ/MJ,全球变暖潜值为0.0565 CO2-Equiv.kg/MJ,与其他液体燃料相比更具环境友好性;对环境影响潜值进行标准化和加权结果计算,全面显示系统不同部分对环境的影响。     

不同生物质原料的气化合成制航煤的环境影响评价

采用生命周期评价方法对玉米秸秆、稻壳和杨木3种生物质的气化合成航空煤油工艺路线进行环境影响评价。选取全球变暖、酸化、富营养化、光化学污染、人体毒性和固体废弃物6种环境影响类型，对3种工艺路线的全生命周期进行环境影响潜值计算。计算结果表明：系统全生命周期中生产阶段排放最多的是CO2，占比为69.13%～74.36%；运输阶段环境影响最小，在各环境影响潜值中占比不足7%；玉米秸秆是3种生物质中环境影响最小的原料，减少费托合成反应器的耗电量可降低玉米秸秆工艺的环境影响。     

唐山市畜禽粪便产沼气发电生命周期评价

为探究唐山市某畜禽粪便厌氧发酵沼气项目的减排潜力,通过项目案例的实际生产数据,运用生命周期评价方法分析唐山市某畜禽粪便产沼气发电项目和传统火力发电项目不同阶段的环境影响表现。结果表明：火力发电各阶段的污染物排放差异较大,主要集中在燃煤发电阶段;沼气发电各阶段污染物排放量除SO2、CO2、CH4外无明显差异。沼气发电全生命周期过程的环境表现均优于火力发电,具有更高的减排能力,其中沼气发电加权后的环境酸化潜势比火力发电低96.64%,其次分别是人体毒性潜势（77.32%）、全球变暖潜势（67.78%）和富营养化潜势（5.71%）。     

典型生物质发酵制取燃料乙醇环境影响分析

结合生命周期评价方法与层次分析方法对杨木、玉米秸秆、甘蔗渣3种典型纤维素生物质的发酵制取燃料乙醇工艺进行环境影响评价。针对酸化、富营养化、全球变暖、化石能源消耗、光化学污染、人体毒性6种环境类型进行分析对比,并选取3个不同视角分析生物质发酵工艺所带来的环境影响。结果表明：农业阶段和生产阶段所产生的温室效应在全生命周期过程中占比最高;全球性视角下,全球变暖影响占比较高;区域性和局地性视角下,工艺的酸化影响最严重。     

生物质电转气技术的生命周期评价

为了研究生物质电转气技术的环境影响,选用玉米杆、稻秸这2种生物质,采用生命周期评价(LCA)模型全面评价了生物质电转气技术的全生命周期过程,利用SimaPro软件对生物质的获取、生物质直燃发电、CH₄和H₂的生产、CH₄的运输及利用等阶段进行生命周期评价,得到各阶段主要的环境影响类型,并对比分析了玉米秆和稻秸的环境影响潜值。结果表明：海洋水生毒性、全球暖化、淡水水生毒性以及酸化是表现较为突出的环境影响类型;在海洋水生毒性这一环境指标上,稻秸电转气技术是玉米杆电转气技术的2.8倍;在全球暖化、人体毒性、酸化等环境影响类型上,玉米秆和稻秸的影响程度较为相似。     

北方农村复合颗粒燃料取暖全生命周期评价研究

以秸秆和煤为原料制备复合颗粒燃料,利用全生命周期评价方法,研究颗粒燃烧取暖全生命周期过程中的能源消耗和环境影响。结果表明：颗粒燃料取暖全生命周期过程中能量投入为908 MJ/t,燃烧释放热量15490 MJ/t,能量产出投入比为17.1,能源转化效率较高。颗粒燃料的能量投入主要来自玉米种植,种植过程中的氮肥使用消耗较多能量。对气候变化（GWP）和酸化（AP）贡献较大的清单数据为颗粒燃料的燃烧,其中燃烧污染物排放的直接贡献最大,贡献率分别为53.22%和46.08%;对水资源消耗（WU）贡献较大的清单数据为颗粒燃料的压制,贡献率为71.56%;对富营养化潜值（EP）贡献较大的清单数据为颗粒燃料燃烧后的废渣排放,贡献率为43.40%。     

厨余垃圾厌氧消化与微生物电解池耦合产甲烷全生命周期评价

厌氧消化（AD）是厨余垃圾清洁能源化的主流工艺，通过构建AD与微生物电解池（MEC）耦合工艺（AD-MEC），基于全生命周期评价（LCA）对比AD与AD-MEC耦合工艺处理厨余垃圾产甲烷的环境影响，解析各功能单元的环境影响贡献，并提出优化方案。结果表明，与传统AD工艺相比，新型AD-MEC耦合工艺在富营养化、气候变化、水资源消耗、酸化和初级能源消耗的环境影响潜值均低于AD工艺，削减比例分别为70.28%、39.53%、92.29%、49.68%和41.2%。贡献源解析发现，AD-MEC耦合工艺的预处理和污水处理单元为环境影响的主要贡献源，MEC和AD单元影响较小。基于此，对AD-MEC耦合工艺进行优化，将废水处理单元的出水回用至预处理单元，水资源消耗的环境影响潜值进一步削减61.48%。可见，采用AD-MEC耦合工艺进行厨余垃圾厌氧产沼，通过沼液的深度利用、沼气净化提质和废水回用，可有效减少厨余垃圾处理工艺对环境的影响和资源消耗，具有显著的经济效益和生态环境价值。     

微藻气化发电生命周期评价及碳循环分析

运用ICA的方法,对4MW的微藻气化发电系统进行分析,计算出全生命周期的资源消耗和环境影响潜值.结果表明干微藻气化能产生气体的热值是17.7MJ/kg,每生产1MW·h的电能需消耗908.41kg微藻,产生的总环境影响负荷是2.175人当量,资源消耗系数是1.455毫人当量.由于微藻的光合作用能固定尾气中的CO2,若将烟道尾气用于微藻的养殖,将尾气中50%的CO2的吸收用于自身的生长,大大降低了CO2的排放量.全球变暖潜值(GW)由原来的0.196降低至0.141,下降了28%,由于CO2的减排使环境总负荷也下降了3%,表明尾气的循环利用对减轻环境负荷具有十分重要的意义.     

村镇秸秆废弃物资源化环境评价模型及案例分析

文章在借鉴生命周期影响评价方法的基础上构造出一种定量的废弃物资源化环境评价模型。首先根据秸秆气化发电等典型废弃物资源化技术,总结出常见的能源消耗与环境排放污染物;然后根据这些环境因子全面考虑可能造成的环境影响类型(化石燃料耗竭、全球气候变暖、酸化、光化学烟雾、富营养化、烟粉尘以及人体毒性);最后借鉴生命周期影响评价方法依次进行特征化、标准化及权重赋值;最终构建适用于评价分析村镇废弃物资源化技术的环境评价模型。选取马庄村秸秆太阳能沼气集中供气工程作为实际案例分析,结果表明,村镇居民使用秸秆制沼产生的沼气比使用天然气具有更高的节能减排效益。     

Life cycle assessment of three types of hydrogen production methods using solar energy

A comprehensive life cycle assessment (LCA) is carried out for three methods of hydrogen production by solar energy: hydrogen production by PEM water electrolysis coupling photothermal power generation, hydrogen production by PEM water electrolysis coupling photovoltaic power generation, and hydrogen production by thermochemical water splitting method using S–I cycle coupling solar photothermal technology. The assessment also contains an evaluation of four environmental factors which are global warming potential, acidification potential, ozone depletion potential, and nutrient enrichment potential. After conducting a quantitative analysis of all three methods with environmental factors being considered, a conclusion has been drawn: The global warming potential and the acidification potential of the thermochemical water splitting by S–I cycle coupling solar photothermal technology are 1.02 kg CO₂-eq and 6.56E-3 kg SO₂-eq. And this method has significant advantages in the environmental impact of the whole ecosystem.     

Life cycle assessment of hydrogen-based electricity generation in place of conventional fuels for residential buildings

In the current study, environmental impact evaluation of electricity generation from hydrogen instead of conventional fuels is investigated with a life cycle impact assessment for residential usage. For this purpose, lignite, natural gas, and hydrogen are utilized to a power plant to generate electricity in Istanbul, Turkey throughout the year. The utilized method for life cycle analysis is the CML 2001 which considers the impacts of global warming, acidification, abiotic fossil depletion, photochemical ozone creation, ionising radiation, human toxicity potential, land use, eutrophication potential, ozone layer depletion, freshwater aquatic ecotoxicity, ecotoxicity of marine aquatic, ecotoxicity of marine sediment, and terrestrial ecotoxicity. The results of the present study illustrate that the generation with hydrogen is the best option for the environment in terms of all impact category. The global warming potentials with the 500 years time horizon for each option of electricity generation are found as 1.4 × 10⁶ ton CO₂ eq, 6 × 10⁵ ton CO₂ eq and 4.6 × 10⁴ ton CO₂ eq, respectively in the month of January.     

Life cycle assessment of various cropping systems utilized for producing biofuels: Bioethanol and biodiesel

A life cycle assessment of different cropping systems emphasizing corn and soybean production was performed, assuming that biomass from the cropping systems is utilized for producing biofuels (i.e., ethanol and biodiesel). The functional unit is defined as 1 ha of arable land producing biomass for biofuels to compare the environmental performance of the different cropping systems. The external functions are allocated by introducing alternative product systems (the system expansion allocation approach). Nonrenewable energy consumption, global warming impact, acidification and eutrophication are considered as potential environmental impacts and estimated by characterization factors given by the United States Environmental Protection Agency (EPA-TRACI). The benefits of corn stover removal are (1) lower nitrogen related environmental burdens from the soil, (2) higher ethanol production rate per unit arable land, and (3) energy recovery from lignin-rich fermentation residues, while the disadvantages of corn stover removal are a lower accumulation rate of soil organic carbon and higher fuel consumption in harvesting corn stover. Planting winter cover crops can compensate for some disadvantages (i.e., soil organic carbon levels and soil erosion) of removing corn stover. Cover crops also permit more corn stover to be harvested. Thus, utilization of corn stover and winter cover crops can improve the eco-efficiency of the cropping systems. When biomass from the cropping systems is utilized for biofuel production, all the cropping systems studied here offer environmental benefits in terms of nonrenewable energy consumption and global warming impact. Therefore utilizing biomass for biofuels would save nonrenewable energy, and reduce greenhouse gases. However, unless additional measures such as planting cover crops were taken, utilization of biomass for biofuels would also tend to increase acidification and eutrophication, primarily because large nitrogen (and phosphorus)-related environmental burdens are released from the soil during cultivation.     

Life cycle assessment of Jatropha biodiesel as transportation fuel in rural India

Since 2003 India has been actively promoting the cultivation of Jatropha on unproductive and degraded lands (wastelands) for the production of biodiesel suitable as transportation fuel. In this paper the life cycle energy balance, global warming potential, acidification potential, eutrophication potential and land use impact on ecosystem quality is evaluated for a small scale, low-input Jatropha biodiesel system established on wasteland in rural India. In addition to the life cycle assessment of the case at hand, the environmental performance of the same system expanded with a biogas installation digesting seed cake was quantified. The environmental impacts were compared to the life cycle impacts of a fossil fuel reference system delivering the same amount of products and functions as the Jatropha biodiesel system under research. The results show that the production and use of Jatropha biodiesel triggers an 82% decrease in non-renewable energy requirement (Net Energy Ratio, NER = 1.85) and a 55% reduction in global warming potential (GWP) compared to the reference fossil-fuel based system. However, there is an increase in acidification (49%) and eutrophication (430%) from the Jatropha system relative to the reference case. Although adding biogas production to the system boosts the energy efficiency of the system (NER = 3.40), the GWP reduction would not increase (51%) due to additional CH₄ emissions. For the land use impact, Jatropha improved the structural ecosystem quality when planted on wasteland, but reduced the functional ecosystem quality. Fertilizer application (mainly N) is an important contributor to most negative impact categories. Optimizing fertilization, agronomic practices and genetics are the major system improvement options.     

Exergetic life cycle assessment of a hydrogen production process

Exergetic life cycle assessment (ExLCA) is applied with life cycle assessment (LCA) to a hydrogen production process. This comparative environmental study examines a nuclear-based hydrogen production via thermochemical water splitting using a copper–chlorine cycle. LCA, which is an analytical tool to identify, quantify and decrease the overall environmental impact of a system or a product, is extended to ExLCA. Exergy efficiencies and air pollution emissions are evaluated for all process steps, including the uranium processing, nuclear and hydrogen production plants. LCA results are presented in four categories: acidification potential, eutrophication potential, global warming potential and ozone depletion potential. A parametric study is performed for various plant lifetimes. The ExLCA results indicate that the greatest irreversibility is caused by uranium processing. The primary contributor of the life cycle irreversibility of the nuclear-based hydrogen production process is fuel (uranium) processing, for which the exergy efficiency is 26.7% and the exergy destruction is 2916.3 MJ. The lowest global warming potential per megajoule exergy of hydrogen is 5.65 g CO₂-eq achieved a plant capacity of 125,000 kg H₂/day. The corresponding value for a plant capacity of 62,500 kg H₂/day is 5.75 g CO₂-eq.     

Life cycle assessment of SNG from wood for heating, electricity, and transportation

The conversion of wood to synthetic natural gas (SNG) via gasification and catalytic methanation is a renewable close to commercialization technology that could substitute fossil fuels and alleviate global warming. In order to assure that it is beneficial from the environmental perspective, a cradle to grave life cycle assessment (LCA) of SNG from a first-of-its-kind polygeneration unit for heating, electricity generation, and transportation was conducted. These SNG systems were compared to fossil and conventional wood reference systems and environmental benefits from their substitution evaluated. Finally, we conduct sensitivity analysis for expected technological improvements and factors that could decrease environmental performance.It is shown that substituting fossil technologies with SNG systems is environmentally beneficial with regard to global warming and for selected technologies also with regard to aggregated environmental impacts. On the condition that process heat is used efficiently, technological improvements such as increased efficiency and denitrification could further increase this advantage. On the other hand, lower GHG emissions and aggregated impacts are partly compensated by other environmental effects, e.g. eutrophication, ecotoxicity, and respiratory disease caused by inorganics. Since more efficient alternatives exist for the generation of heat and electricity from wood, it is argued that SNG is best used for transportation. In the light of a growing demand for renewable transportation fuels and commercial scale technological development being only in its initial stage, the production of SNG from wood seems to be a promising technology for the near future.     

Life cycle GHG assessment of fossil fuel power plants with carbon capture and storage

The evaluation of life cycle greenhouse gas emissions from power generation with carbon capture and storage (CCS) is a critical factor in energy and policy analysis. The current paper examines life cycle emissions from three types of fossil-fuel-based power plants, namely supercritical pulverized coal (super-PC), natural gas combined cycle (NGCC) and integrated gasification combined cycle (IGCC), with and without CCS. Results show that, for a 90% CO₂ capture efficiency, life cycle GHG emissions are reduced by 75–84% depending on what technology is used. With GHG emissions less than 170 g/kWh, IGCC technology is found to be favorable to NGCC with CCS. Sensitivity analysis reveals that, for coal power plants, varying the CO₂ capture efficiency and the coal transport distance has a more pronounced effect on life cycle GHG emissions than changing the length of CO₂ transport pipeline. Finally, it is concluded from the current study that while the global warming potential is reduced when MEA-based CO₂ capture is employed, the increase in other air pollutants such as NO_x and NH₃ leads to higher eutrophication and acidification potentials.     

Life-cycle assessment of diesel, natural gas and hydrogen fuel cell bus transportation systems

The Sustainable Transport Energy Programme (STEP) is an initiative of the Government of Western Australia, to explore hydrogen fuel cell technology as an alternative to the existing diesel and natural gas public transit infrastructure in Perth. This project includes three buses manufactured by DaimlerChrysler with Ballard fuel cell power sources operating in regular service alongside the existing natural gas and diesel bus fleets. The life-cycle assessment (LCA) of the fuel cell bus trial in Perth determines the overall environmental footprint and energy demand by studying all phases of the complete transportation system, including the hydrogen infrastructure, bus manufacturing, operation, and end-of-life disposal. The LCAs of the existing diesel and natural gas transportation systems are developed in parallel. The findings show that the trial is competitive with the diesel and natural gas bus systems in terms of global warming potential and eutrophication. Emissions that contribute to acidification and photochemical ozone are greater for the fuel cell buses. Scenario analysis quantifies the improvements that can be expected in future generations of fuel cell vehicles and shows that a reduction of greater than 50% is achievable in the greenhouse gas, photochemical ozone creation and primary energy demand impact categories.     

Clean fuel options with hydrogen for sea transportation: A life cycle approach

In this study, two potential fuels, namely hydrogen and ammonia, are alternatively proposed to replace heavy fuel oils in the engines of sea transportation vehicles. A comparative life cycle assessments of different types of sea transportation vehicles are performed to investigate the impacts of fuel switching on the environment. The entire transport life cycle is considered in the life cycle analyses consisting of production of freight ship and tanker; operation of freight ship and tanker; construction and land use of port; operation, maintenance and disposal of port; production and transportation of these clean fuels. Various environmental impact categories, such as global warming, marine sediment ecotoxicity, marine aquatic ecotoxicity, acidification and ozone layer depletion are selected in order to examine the diverse effects of switching to clean fuels in maritime transportation. As a carbon-free fuel for marine vehicle engines, ammonia and hydrogen, yield considerably lower global warming impact during the operation. Furthermore, numerous production methods of alternative fuels are evaluated to comparatively show environmentally benign options. The results of this study demonstrate that if ammonia is even partially utilized in the engines of ocean tankers as dual fuel (with heavy fuel oils), overall life cycle greenhouse gas emissions per tonne-kilometer can be decreased about 27% whereas it can be decreased by about 40% when hydrogen is used as dual fuel.     

Life cycle GHG emission analysis of power generation systems: Japanese case

This study presents the results of a life cycle analysis (LCA) of greenhouse gas emissions from power generation systems in order to understand the characteristics of these systems from the perspective of global warming. Nine different types of power generation systems were examined: coal-fired, oil-fired, LNG-fired, LNG-combined cycle, nuclear, hydropower, geothermal, wind power and solar-photovoltaic (PV). Life cycle greenhouse gas (GHG) emission per kW h of electricity generated was estimated for the systems using a combined method of process analysis and input–output analysis. First, average power generation systems reflecting the current status in Japan were examined as base cases. Second, the impacts of emerging and future nuclear, wind power and PV technologies were analyzed. Finally, uncertainties associated with some assumptions were examined to help clarify interpretation of the results.