Life cycle inventory for electricity generation in China

Background, Goal and Scope The objective of this study was to produce detailed a life cycle inventory (LCI) for the provision of 1 kWh of electricity to consumers in China in 2002 in order to identify areas of improvement in the industry. The system boundaries were processes in power stations, and the construction and operation of infrastructure were not included. The scope of this study was the consumption of fossil fuels and the emissions of air pollutants, water pollutants and solid wastes, which are listed as follows: (1) consumption of fossil fuels, including general fuels, such as raw coal, crude oil and natural gas, and the uranium used for nuclear power; (2) emissions of air pollutants from thermal power, hydropower and nuclear power plants; (3) emissions of water pollutants, including general water waste from fuel electric plants and radioactive waste fluid from nuclear power plants; (4) emissions of solid wastes, including fly ash and slag from thermal power plants and radioactive solid wastes from nuclear power plants. Methods Data were collected regarding the amount of fuel, properties of fuel and the technical parameters of the power plants. The emissions of CO₂, SO₂, NO_x, CH₄, CO, non-methane volatile organic compound (NMVOC), dust and heavy metals (As, Cd, Cr, Hg, Ni, Pb, V, Zn) from thermal power plants as well as fuel production and distribution were estimated. The emissions of CO₂ and CH₄ from hydropower plants and radioactive emissions from nuclear power plants were also investigated. Finally, the life cycle inventory for China’s electricity industry was calculated and analyzed. Results Related to 1 kWh of usable electricity in China in 2002, the consumption of coal, oil, gas and enriched uranium were 4.57E-01, 8.88E-03, 7.95E-03 and 9.03E-08 kg; the emissions of CO₂, SO₂, NO_x, CO, CH₄, NMVOC, dust, As, Cd, Cr, Hg, Ni, Pb, V, and Zn were 8.77E-01, 8.04E-03, 5.23E-03, 1.25E-03, 2.65E-03, 3.95E-04, 1.63E-02, 1.62E-06, 1.03E-08, 1.37E-07, 7.11E-08, 2.03E-07, 1.42E-06, 2.33E-06, and 1.94E-06 kg; the emissions of waste water, COD, coal fly ash, and slag were 1.31, 6.02E-05, 8.34E-02, and 1.87E-02 kg; and the emissions of inactive gas, halogen and gasoloid, tritium, non-tritium, and radioactive solid waste were 3.74E+01 Bq, 1.61E-01 Bq, 4.22E+01 Bq, 4.06E-02 Bq, and 2.68E-10 m³ respectively. Conclusions The comparison result between the LCI data of China’s electricity industry and that of Japan showed that most emission intensities of China’s electricity industry were higher than that of Japan except for NMVOC. Compared with emission intensities of the electricity industry in Japan, the emission intensities of CO₂ and Ni in China were about double; the emission intensities of NO_x, Cd, CO, Cr, Hg and SO₂ in China were more than 10 times that of Japan; and the emission intensities of CH₄, V, Pb, Zn, As and dust were more than 20 times. The reasons for such disparities were also analyzed. Recommendations and Perspectives To get better LCI for the electricity industry in China, it is important to estimate the life cycle emissions during fuel production and transportation for China. Another future improvement could be the development of LCIs for construction and operation of infrastructure such as factory buildings and dams. It would also be important to add the information about land use for hydropower.     

Estimating the Greenhouse Gas Balance of Individual Gas‐Fired and Oil‐Fired Electricity Plants on a Global Scale

Life cycle greenhouse gas (LC‐GHG) emissions from electricity generated by a specific resource, such as gas and oil, are commonly reported on a country‐by‐country basis. Estimation of variability in LC‐GHG emissions of individual power plants can, however, be particularly useful to evaluate or identify appropriate environmental policy measures. Here, we developed a regression model to predict LC‐GHG emissions per kilowatt‐hour (kWh) of electricity produced by individual gas‐ and oil‐fired power plants across the world. The regression model uses power plant characteristics as predictors, including capacity, age, fuel type (fuel oil or natural gas), and technology type (single or combined cycle) of the plant. The predictive power of the model was relatively high (R² = 81% for predictions). Fuel and technology type were identified as the most important predictors. Estimated emission factors ranged from 0.45 to 1.16 kilograms carbon dioxide equivalents per kilowatt‐hour (kg CO₂‐eq/kWh) and were clearly different between natural gas combined cycle (0.45 to 0.57 kg CO₂‐eq/kWh), natural gas single cycle (0.66 to 0.85 kg CO₂‐eq/kWh), oil combined cycle power plants (0.63 to 0.79 kg CO₂‐eq/kWh), and oil single cycle (0.94 to 1.16 kg CO₂‐eq/kWh). Our results thus indicate that emission data averaged by fuel and technology type can be profitably used to estimate the emissions of individual plants.     

CO2 emissions related to the electricity consumption in the european primary aluminium production a comparison of electricity supply approaches

The objective of this study is to estimate the specific CO₂ emissions related to the electricity consumption in the European primary aluminium production and to compare different choices of system boundaries of its electricity supply. The study covers all European aluminium smelters, except Russia and the Ukraine. The concepts of single power plant supply, contract mix, national mix and European grid mix are compared as alternative choices of system boundaries of the electricity supply. The calculations of the electricity consumption in the electrolysis are based on plant-specific information on technology, production and electricity supply. Detailed fuel and country-specific data on CO₂ emissions of the relevant types of electricity generation are used with a ‘from cradle to grave’ perspective. The specific emissions calculated for Europe fall into the range of 6-7 kg CO₂/kg Al depending on the choice of system boundaries.     

Life cycle assessment of cane-sugar on the island of mauritius

Goal, Scope and Background  Agricultural production includes not only crop production, but also food processing, transport, distribution, preparation, and disposal. The effects of all these must be considered and controlled if the food chain is to be made sustainable. The goal of this case study was to identify and review the significant areas of potential environmental impacts across the whole life cycle of cane sugar on the island of Mauritius. Methods  The functional unit was one tonne of exported raw sugar from the island. The life cycle investigated includes the stage of cane cultivation and harvest, cane burning, transport, fertilizer and herbicide manufacture, cane sugar manufacture and electricity generation from bagasse. Data was gathered from companies, factories, sugar statistics, databases and literature. Energy depletion, climate change, acidification, oxidant formation, nutrification, aquatic ecotoxicity and human toxicity were assessed. Results and Discussion  The inventory of the current sugar production system revealed that the production of one tonne of sugar requires, on average, a land area of 0.12 ha, the application of 0.84 kg of herbicides and 16.5 kg of N-fertilizer, use of 553 tons of water and 170 tonne-km of transport services. The total energy consumption is about 14235 MJ per tonne of sugar, of which fossil fuel consumption accounts for 1995 MJ and the rest is from renewable bagasse. 160 kg of CO₂ per tonne of sugar is released from fossil fuel energy use and the net avoided emissions of CO₂ on the island due to the use of bagasse as an energy source is 932,000 tonnes. 1.7 kg TSP, 1.21 kg SO₂,1.26 kgNO_xand 1.26 kg CO are emitted to the air per tonne of sugar produced. 1.7 kg N, 0.002 kg herbicide, 19.1 kg COD, 13.1 kgTSS and 0.37 kg PO₄ ^3- are emitted to water per tonne of sugar produced. Cane cultivation and harvest accounts for the largest environmental impact (44%) followed by fertilizer and herbicide manufacture (22%), sugar processing and electricity generation (20%), transportation (13%) and cane burning (1%). Nutrification is the main impact followed by acidification and energy depletion. Conclusions  There are a number of options for improvement of the environmental performance of the cane-sugar production chain. Cane cultivation, and fertilizer and herbicide manufacture, were hotspots for most of the impact categories investigated. Better irrigation systems, precision farming, optimal use of herbicides, centralisation of sugar factories, implementation of co-generation projects and pollution control during manufacturing and bagasse burning are measures that would considerably decrease resource use and environmental impacts. Recommendation and Outlook  LCA was shown to be a valuable tool to assess the environmental impacts throughout the food production chain and to evaluate government policies on agricultural production systems.     

中国省级火电供应生命周期清单分析

应用生命周期评价方法,建立了我国各省区的火电供应生命周期清单。清单分析结果表明,我国各省区单位火电供应的生命周期清单之间,及与全国单位火电供应的生命周期清单之间均存在一定差异,以总能源投入和全球变暖潜值为例进行了分析。在全球变暖潜值方面,我国单位火电供应的平均值为1.05kg/k Wh。云南等15个省区的单位火电全球变暖潜值与全国平均水平相差±10%以上。如果基于全国单位火电供应的平均全球变暖潜值计算各省火电总量全球变暖潜值,与基于各省单位火电全球变暖潜值计算的结果相比,也存在一定的差距。15个省区与基于全国平均值计算的结果相差±10%以上,表明了核算各省区火电清单的必要性。中国省级火电供应生命周期清单为省区级别的材料、产品、产业等生命周期评价提供数据支撑,也为各省区电力节能减排提供了理论基础。     

模拟SO42-沉降对闽江口淡水感潮野慈姑湿地甲烷排放通量的影响

2015年12月—2016年10月,每月小潮日原位定期向闽江口塔礁洲淡水感潮野慈姑(Sagittaria trifolia L.)湿地施加剂量为60、120 kg S hm~(-2)a~(-1)的K_2SO_4溶液(分别记做S-60和S-120),探讨模拟硫酸根(SO_4~(2-))沉降对河口淡水感潮湿地甲烷(CH4)排放通量及间隙水SO_4~(2-)浓度的影响。对照、S-60和S-120处理组CH_4排放通量年均值分别为(7.88±1.00)mg h~(-1)m~(-2)、(6.55±0.97)mg h~(-1)m~(-2)和(6.66±1.49)mg h~(-1)m~(-2)。在年尺度上,两个高强度模拟SO_4~(2-)沉降处理组均未显著降低闽江口淡水感潮野慈姑湿地CH_4排放通量(P0.05),即高强度SO_4~(2-)沉降不会对河口淡水感潮湿地CH_4排放通量产生类似于其对泥炭湿地和水稻田的显著抑制效应。在年尺度以及秋、冬季,两个施加K_2SO_4溶液处理显著增加了野慈姑湿地10 cm深度土壤间隙水SO_4~(2-)浓度。对于各个处理组,温度较高的夏、秋季CH_4排放通量均显著高于温度相对较低的冬、春季(P0.05)。不同处理组CH_4排放通量均与土壤温度呈显著正相关关系,温度仍然是影响亚热带河口淡水感潮湿地CH_4排放通量的重要环境因子。     

Trends in cation, nitrogen, sulfate and hydrogen ion concentrations in precipitation in the United States and Europe from 1978 to 2010: a new look at an old problem

Industrial emissions of SO₂ and NO_x, resulting in the formation and deposition of sulfuric and nitric acids, affect the health of both terrestrial and aquatic ecosystems. Since the mid-late 20th century, legislation to control acid rain precursors in both Europe and the US has led to significant declines in both SO₄–S and H⁺ in precipitation and streams. However, several authors noted that declines in streamwater SO₄–S did not result in stoichiometric reductions in stream H⁺, and suggested that observed reductions in base cation inputs in precipitation could lessen the effect of air pollution control on improving stream pH. We examined long-term precipitation chemistry (1978–2010) from nearly 30 sites in the US and Europe that are variably affected by acid deposition and that have a variety of industrial and land-use histories to (1) quantify trends in SO₄–S, H⁺, NH₄–N, Ca, and NO₃–N, (2) assess stoichiometry between H⁺ and SO₄–S before and after 1990, and (3) examine regional synchrony of trends. We expected that although the overall efforts of developed countries to reduce air pollution and acid rain by the mid-late 20th century would tend to synchronize precipitation chemistry among regions, geographically varied patterns of fossil fuel use and pollution control measures would produce important asynchronies among European countries and the United States. We also expected that control of particulate versus gaseous emission, along with trends in NH₃ emissions, would be the two most significant factors affecting the stoichiometry between SO₄–S and H⁺. Relationships among H⁺, SO₄–S, NH₄–N, and cations differed markedly between the US and Europe. Controlling for SO₄–S levels, H⁺ in precipitation was significantly lower in Europe than in the US, because (1) alkaline dust loading from the Sahara/Sahel was greater in Europe than the US, and (2) emission of NH₃, which neutralizes acidity upon conversion to NH₄ ⁺, is generally significantly higher in Europe than in the US. Trends in SO₄–S and H⁺ in precipitation were close to stoichometric in the US throughout the period of record, but not in Europe, especially eastern Europe. Ca in precipitation declined significantly before, but not after 1990 in most of the US, but Ca declined in eastern Europe even after 1990. SO₄–S in precipitation was only weakly related to fossil fuel consumption. The stoichiometry of SO₄–S and H⁺ may be explained in part by emission controls, which varied over time and among regions. Control of particulate emissions reduces alkaline particles that neutralize acid precursors as well as S-containing particulates, reducing SO₄–S and Ca more steeply than H⁺, consistent with trends in the northeastern US and Europe before 1990. In contrast, control of gaseous SO₂ emissions results in a stoichiometric relationship between SO₄–S and H⁺, consistent with trends in the US and many western European countries, especially after 1991. However, in many European countries, declining NH₃ emissions contributed to the lack of stoichiometry between SO₄–S and H⁺.Recent reductions in NO_x emissions have also contributed to declines in H⁺ in precipitation. Future changes in precipitation acidity are likely to depend on multiple factors including trends in NO_x and NH₃ emission controls, naturally occurring dust, and fossil fuel use, with significant implications for the health of both terrestrial and aquatic ecosystems.     

Renewable Energy from Willow Biomass Crops: Life Cycle Energy,Environmental and Economic Performance

Short-rotation woody crops (SRWC) along with other woody biomass feedstocks will play a significant role in a more secure and sustainable energy future for the United States and around the world. In temperate regions, shrub willows are being developed as a SRWC because of their potential for high biomass production in short time periods, ease of vegetative propagation, broad genetic base, and ability to resprout after multiple harvests. Understanding and working with willow's biology is important for the agricultural and economic success of the system.

The energy, environmental, and economic performance of willow biomass production and conversion to electricity is evaluated using life cycle modeling methods. The net energy ratio (electricity generated/life cycle fossil fuel consumed) for willow ranges from 10 to 13 for direct firing and gasification processes. Reductions of 70 to 98 percent (compared to U.S. grid generated electricity) in greenhouse gas emissions as well as NO_x, SO₂, and particulate emissions are achieved.

Despite willow's multiple environmental and rural development benefits, its high cost of production has limited deployment. Costs will be lowered by significant improvements in yields and production efficiency and by valuing the system's environmental and rural development benefits. Policies like the Conservation Reserve Program (CRP), federal biomass tax credits and renewable portfolio standards will make willow cost competitive in the near term.

The avoided air pollution from the substitution of willow for conventional fossil fuel generated electricity has an estimated damage cost of $0.02 to $0.06 kWh^?1. The land intensity of about 4.9 × 10^?5 ha-yr/kWh is greater than other renewable energy sources. This may be considered the most significant limitation of willow, but unlike other biomass crops such as corn it can be cultivated on the millions of hectares of marginal agricultural lands, improving site conditions, soil quality and landscape diversity. A clear advantage of willow biomass compared to other renewables is that it is a stock resource whereas wind and PV are intermittent. With only 6 percent of the current U.S. energy consumption met by renewable sources the accelerated development of willow biomass and other renewable energy sources is critical to address concerns of energy security and environmental impacts associated with fossil fuels.     

Increased power generation from primary sludge in microbial fuel cells coupled with prefermentation

Raw primary sludge and the prefermentation liquor (PL) of primary sludge were used to generate electricity in single-chambered air-cathode microbial fuel cells (MFCs). The MFCs treating the primary sludge produced 0.53 V and 370 mW/m² for the maximum potential and power density, respectively. In the primary sludge-fed MFCs, only 5 % of the total energy production was produced from direct electricity generation, whereas 95 % of that resulted from the conversion of methane to electricity. MFCs treating the PL generated the maximum potential of 0.58 V and maximum power density of 885 mW/m², respectively. In the energy production analysis, direct electricity production (1,921 Wh/kg TCOD_rem) in the MFCs treating the PL was much higher than that of the primary sludge-fed MFC (138 Wh/kg TCOD_rem). Volatile suspended solids during 10 days were reduced to 18.3 and 38 % in the primary sludge-fed MFCs and prefermentation reactor, respectively. These findings suggest that a two-stage process including prefermentation and MFCs is of great benefit on sludge reduction and higher electricity generation from primary sludge.     

Life cycle inventory analysis of co<Subscript>2</Subscript> emissions manufacturing commodity plastics in japan

The goal of this study was to calculate the average CO₂ emissions for manufacturing three commodity plastics, polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) in Japan. The CO₂ emissions were calculated from cradle to gate, excluding the calcination processes after use. As the results, the followings were observed: 1) The gross CO₂ emissions for the manufacture of plastics in Japan were 1.3, 1.4, and 1.7 kg-CO₂/kg-PE, PP, and PVC, respectively. These mainly reflected the difference of CO₂ emissions for the in-house electricity generation. 2) The CO₂ emissions for the electricity used for manufacturing PVC were higher than that used for PE and PP, because additional electricity was required for the electrolysis to produce chlorine. The gross electricity consumption for manufacturing PVC was 1.3 kWh/kg-PVC, and the other plastics consumed 0.5 kWh/kg-Products. In addition, the effects of energy saving were studied using a projected gas-diffusion electrode for the electrolysis of salt on the reduction of CO₂ emissions. It was estimated that the reduction in CO₂ emissions was 7% compared with the present PVC manufacturing processes.     

Life cycle assessment of wind farms in Ethiopia

Purpose

The overall aim of this study is to contribute to the creation of LCA database on electricity generation systems in Ethiopia. This study specifically estimates the environmental impacts associated with wind power systems supplying high voltage electricity to the national grid. The study has regional significance as the Ethiopian electric system is already supplying electricity to Sudan and Djibouti and envisioned to supply to other countries in the region.

Materials and methods

Three different grid-connected wind power systems consisting of four different models of wind turbines with power rates between 1 and 1.67 MW were analyzed for the situation in Ethiopia. The assessment takes into account all the life cycle stages of the total system, cradle to grave, considering all the processes related to the wind farms: raw material acquisition, manufacturing of main components, transporting to the wind farm, construction, operation and maintenance, and the final dismantling and waste treatment. The study has been developed in line with the main principles of the ISO 14040 and ISO 14044 standard procedures. The analysis is done using SimaPro software 8.0.3.14 multi-user, Ecoinvent database version 3.01, and ReCiPe 2008 impact assessment method. The assumed operational lifetime as a baseline is 20 years.

Results and discussion

The average midpoint environmental impact of Ethiopian wind power system per kWh electricity generated is for climate change: 33.6 g CO₂ eq., fossil depletion: 8 g oil eq., freshwater ecotoxicity: 0.023 g 1,4-DCB eq., freshwater eutrophication: 0.005 g N eq., human toxicity: 9.9 g 1,4-DCB eq., metal depletion: 18.7 g Fe eq., marine ecotoxicity: 0.098 g 1,4-DCB eq., particulate matter formation: 0.097 g PM10 eq., photochemical oxidant formation: 0.144 g NMVOC, and terrestrial acidification: 0.21 g SO₂ eq. The pre-operation phase that includes the upstream life cycle stage is the largest contributor to all the environmental impacts, with shares ranging between 82 and 96%. The values of cumulative energy demand (CED) and energy return on investment (EROI) for the wind power system are 0.393 MJ and 9.2, respectively.

Conclusion

The pre-operation phase is the largest contributor to all the environmental impact categories. The sensitivity and scenario analyses indicate that changes in wind turbine lifespans, capacity factors, exchange rates for parts, transport routes, and treatment activities would result in significant changes in the LCA results.

     

Environmental impact of two aerobic composting technologies using life cycle assessment

Background, aim, and scope  Composting is a viable technology to treat the organic fraction of municipal solid waste (OFMSW) because it stabilizes biodegradable organic matter and contributes to reduce the quantity of municipal solid waste to be incinerated or land-filled. However, the composting process generates environmental impacts such as atmospheric emissions and resources consumption that should be studied. This work presents the inventory data and the study of the environmental impact of two real composting plants using different technologies, tunnels (CT) and confined windrows (CCW). Materials and methods  Inventory data of the two composting facilities studied were obtained from field measurements and from plant managers. Next, life cycle assessment (LCA) methodology was used to calculate the environmental impacts. Composting facilities were located in Catalonia (Spain) and were evaluated during 2007. Both studied plants treat source separated organic fraction of municipal solid waste. In both installations the analysis includes environmental impact from fuel, water, and electricity consumption and the main gaseous emissions from the composting process itself (ammonia and volatile organic compounds). Results and discussion  Inventory analysis permitted the calculation of different ratios corresponding to resources consumption or plant performance and process yield with respect to 1 t of OFMSW. Among them, it can be highlighted that in both studied plants total energy consumption necessary to treat the OFMSW and transform it into compost was between 130 and 160 kWh/t OFMSW. Environmental impact was evaluated in terms of global warming potential (around 60 kg CO₂/t OFMSW for both plants), acidification potential (7.13 and 3.69 kg SO₂ eq/t OFMSW for CT and CCW plant respectively), photochemical oxidation potential (0.1 and 3.11 kg C₂H₄ eq/t OFMSW for CT and CCW plant, respectively), eutrophication (1.51 and 0.77 kg /t OFMSW for CT and CCW plant, respectively), human toxicity (around 15 kg 1,4-DB eq/t OFMSW for both plants) and ozone layer depletion (1.66 × 10⁻⁵ and 2.77 × 10⁻⁵ kg CFC⁻¹¹ eq/t OFMSW for CT and CCW plant, respectively). Conclusions  This work reflects that the life cycle perspective is a useful tool to analyze a composting process since it permits the comparison among different technologies. According to our results total energy consumption required for composting OFMSW is dependent on the technology used (ranging from 130 to 160 kWh/t OFMSW) as water consumption is (from 0.02 to 0.33 m³ of water/t OFMSW). Gaseous emissions from the composting process represent the main contribution to eutrophication, acidification and photochemical oxidation potentials, while those contributions related to energy consumption are the principal responsible for global warming. Recommendations and perspectives  This work provides the evaluation of environmental impacts of two composting technologies that can be useful for its application to composting plants with similar characteristics. In addition, this study can also be part of future works to compare composting with other OFMSW treatments from a LCA perspective. Likewise, the results can be used for the elaboration of a greenhouse gasses emissions inventory in Catalonia and Spain.     

Development of human health damage factors for tropospheric ozone considering transboundary transport on a global scale

Purpose

Air pollutants such as tropospheric ozone and PM_2.5 travel through large areas. The damage factors (DFs) presented by existing researches in life cycle impact assessment do not take into consideration transboundary movement. A previous study used a global chemistry transport model (CTM), to develop health damage factors for ten different regions around the world by considering the transboundary movement of PM_2.5. Under the same assessment procedure, this research is designed to calculate the ozone DFs by region and to find the effects of wide range movement on the DFs.

Methods

The DFs by regions are defined as changes in disability-adjusted life years (DALYs) derived from changes in tropospheric ozone concentration around the world which is induced by an increase in emissions of the unit amount of nitrogen oxides (NO_x) and non-methane volatile organic compounds (NMVOC). DFs for ten regions are calculated as follows. Firstly, the concentration change of worldwide ozone caused by a change in emission of a substance from one region is estimated with a global scale CTM for both NO_x and NMVOC. Secondly, DALY changes on the world due to a change in concentration of ozone are estimated by using population data and epidemiological concentration-response functions for mortality and morbidity. Finally, the above calculations are done for all targeted ten regions.

Results and discussion

DFs of NO_x and NMVOC for ten regions were calculated as 0.3–4.2?×?10^?5 DALY/kg and 0.2–5.6?×?10^?6 DALY/kg, respectively. It was found DFs might be underestimated around 10 to 70 % by region if the transboundary movement is not taken into consideration. In many regions in the northern hemisphere, about 60 % of damage occurs outside the emission area, which is larger than that of southern hemispheric regions due to a larger population exposed to downwind places. In regions of China and India, however, the influence on other regions accounted for only 10 % because these regions involve larger influences in the source region. The impact of NO titration effect can be seen in cold seasons in many regions, but it was found that the effect is remarkable on an annual average only in Europe, a cold region with large emissions.

Conclusions

The human health DFs of NO_x and NMVOC considering effects of transboundary movement of tropospheric ozone are estimated for ten regions by using a global CTM. As a future work, it is important to show the interannual sensitivity of the DFs through chronological assessments.

     

Lifecycle climate impact and primary energy use of electric and biofuel cargo trucks

Heavy trucks contribute significantly to climate change, and in 2020 were responsible for 7% of total Swedish GHG emissions and 5% of total global CO₂ emissions. Here we study the full lifecycle of cargo trucks powered by different energy pathways, comparing their biomass feedstock use, primary energy use, net biogenic and fossil CO₂ emission and cumulative radiative forcing. We analyse battery electric trucks with bioelectricity from stand-alone or combined heat and power (CHP) plants, and pathways where bioelectricity is integrated with wind and solar electricity. We analyse trucks operated on fossil diesel fuel and on dimethyl ether (DME). All energy pathways are analysed with and without carbon capture and storage (CCS). Bioelectricity and DME are produced from forest harvest residues. Forest biomass is a limited resource, so in a scenario analysis we allocate a fixed amount of biomass to power Swedish truck transport. Battery lifespan and chemistry, the technology level of energy supply, and the biomass source and transport distance are all varied to understand how sensitive the results are to these parameters. We find that pathways using electricity to power battery electric trucks have much lower climate impacts and primary energy use, compared to diesel- and DME-based pathways. The pathways using bioelectricity with CCS result in negative emissions leading to global cooling of the earth. The pathways using diesel and DME have significant and very similar climate impact, even with CCS. The robust results show that truck electrification and increased renewable electricity production is a much better strategy to reduce the climate impact of cargo transport than the adoption of DME trucks, and much more primary energy efficient. This climate impact analysis includes all fossil and net biogenic CO₂ emissions as well as the timing of these emissions. Considering only fossil emissions is incomplete and could be misleading.     

Climate change mitigation potential of local use of harvest residues for bioenergy in Canada

We estimate the mitigation potential of local use of bioenergy from harvest residues for the 2.3 × 10⁶ km² (232 Mha) of Canada's managed forests from 2017 to 2050 using three models: Carbon Budget Model of the Canadian Forest Sector (CBM‐CFS3), a harvested wood products (HWP) model that estimates bioenergy emissions, and a model of emission substitution benefits from the use of bioenergy. We compare the use of harvest residues for local heat and electricity production relative to a base case scenario and estimate the climate change mitigation potential at the forest management unit level. Results demonstrate large differences between and within provinces and territories across Canada. We identify regions with increasing benefits to the atmosphere for many decades into the future and regions where no net benefit would occur over the 33‐year study horizon. The cumulative mitigation potential for regions with positive mitigation was predicted to be 429 Tg CO₂e in 2050, with 7.1 TgC yr ^?1 of harvest residues producing bioenergy that met 3.1% of the heat demand and 2.9% of the electricity demand for 32.1 million people living within these regions. Our results show that regions with positive mitigation produced bioenergy, mainly from combined heat and power facilities, with emissions intensities that ranged from roughly 90 to 500 kg CO₂e MWh^?1. Roughly 40% of the total captured harvest residue was associated with regions that were predicted to have a negative cumulative mitigation potential in 2050 of ?152 Tg CO₂e. We conclude that the capture of harvest residues to produce local bioenergy can reduce GHG emissions in populated regions where bioenergy, mainly from combined heat and power facilities, offsets fossil fuel sources (fuel oil, coal and petcoke, and natural gas).     

春玉米-晚稻与早稻-晚稻种植模式碳足迹比较

量化作物生产的碳足迹有助于为农业生态系统温室气体减排提供理论依据。利用生命周期法研究了我国南方地区稻田春玉米-晚稻水旱轮作种植模式和早稻-晚稻连作种植模式下粮食生产的碳足迹,并定量分析粮食生产过程中各种碳排放源的相对贡献。结果表明,与早稻-晚稻的连作模式相比,春玉米-晚稻轮作模式的单位面积碳排放降低了6724 kg CO₂-eq/hm²,单位产量的碳足迹降低了0.56 kg CO₂-eq/kg。春玉米比早稻少排放6228 kg CO₂-eq/hm²;与早稻-晚稻模式中晚稻碳排放相比,春玉米-晚稻轮作模式晚稻碳排放降低了497 kg CO₂-eq/hm²。早稻-晚稻种植模式的碳足迹主要来源于甲烷（CH₄）,其碳排放为9776 kg CO₂-eq/hm²（54.8%）,氮肥生产和施用的碳排放为2871 kg CO₂-eq/hm²（16.1%）,灌溉电力消耗的碳排放2849 kg CO₂-eq/hm²（16.0%）。春玉米-晚稻轮作模式的碳足迹主要来源于CH₄的碳排放4442 kg CO₂-eq/hm²（39.9%）,氮肥生产和施用的碳排放2871 kg CO₂-eq/hm²（25.8%）,灌溉电力消耗的碳排放1508 kg CO₂-eq/hm²（13.6%）。该模式中晚稻的碳足迹组成情况与春玉米-晚稻模式的碳足迹相似。但是,对于春玉米而言,其碳足迹主要来源氮肥生产和施用的碳排放1436 CO₂-eq/hm²（50.1%）,氧化亚氮（N₂O）的碳排放为579 kg CO₂-eq/hm²（20.2%）,CH₄的碳排放为378 CO₂-eq/hm²（13.2%）。同时,相比于早稻-晚稻中晚稻的产量（6333 kg/hm²）,春玉米-晚稻轮作模式下的晚稻产量（7270 kg/hm²）提高了14.8%。因此,引入春玉米-晚稻轮作模式有利于提升稻田生产力,降低稻田连作系统碳排放和碳足迹。     

Are the benefits of yield responses to nitrogen fertilizer application in the bioenergy crop Miscanthus × giganteus offset by increased soil emissions of nitrous oxide?

A field trial was carried out on a 15 year old Miscanthus stand, subject to nitrogen fertilizer treatments of 0, 63 and 125 kg‐N ha^?1, measuring N₂O emissions, as well as annual crop yield over a full year. N₂O emission intensity (N₂O emissions calculated as a function of above‐ground biomass) was significantly affected by fertilizer application, with values of 52.2 and 59.4 g N₂O‐N t^?1 observed at 63 and 125 kg‐N ha^?1, respectively, compared to 31.3 g N₂O‐N t^?1 in the zero fertilizer control. A life cycle analyses approach was applied to calculate the increase in yield required to offset N₂O emissions from Miscanthus through fossil fuel substitution in the fuel chain. For the conditions observed during the field trial yield increases of 0.33 and 0.39 t ha^?1 were found to be required to offset N₂O emissions from the 63 kg‐N ha^?1 treatment, when replacing peat and coal, respectively, while increases of 0.71 and 0.83 t ha^?1 were required for the 125 kg‐N ha^?1 treatment, for each fuel. These values are considerably less than the mean above‐ground biomass yield increases observed here of 1.57 and 2.79 t ha^?1 at fertilization rates 63 and 125 kg‐N ha^?1 respectively. Extending this analysis to include a range of fertilizer application rates and N₂O emission factors found increases in yield necessary to offset soil N₂O emissions ranging from 0.26 to 2.54 t ha^?1. These relatively low yield increase requirements indicate that where nitrogen fertilizer application improves yield, the benefits of such a response will not be offset by soil N₂O emissions.     

Emission payback periods for increased residential insulation using marginal electricity modeling: a life cycle approach

Purpose

Increases in residential insulation can reduce energy consumption and corresponding life cycle emissions, but with increased manufacturing and transportation of insulation and the associated impacts. In this study, we conducted life cycle analyses of residential insulation and estimated payback periods for carbon dioxide (CO₂), nitrogen oxides (NOx), and sulfur dioxide (SO₂) emissions, using modeling techniques that account for regional variability in climate, fuel utilization, and marginal power plant emissions.

Methods

We simulated the increased production of insulation and energy savings if all single-family homes in the USA increased insulation levels to the 2012 International Energy Conservation Code, using an energy simulation model (EnergyPlus) applied to a representative set of home templates. We estimated hourly marginal changes in electricity production and emissions using the Avoided Emissions and Generation Tool (AVERT), and we estimated emissions related to direct residential combustion. We determined changes in upstream emissions for both insulation and energy using openLCA and ecoinvent. Payback periods were estimated by pollutant and region. In sensitivity analyses, we considered the importance of marginal versus average power plant emissions, transportation emissions, emission factors for fiberglass insulation, and sensitivity of emission factors to the magnitude of electricity reduction.

Results and discussion

Combining the life cycle emissions associated with both increased insulation manufacturing and decreased energy consumption, the payback period for increased residential insulation is 1.9 years for CO₂ (regional range 1.4–2.9), 2.5 years for NOx (regional range 1.8–3.9), and 2.7 years for SO₂ (regional range 1.9–4.8). For insulation, transportation emissions are limited in comparison with manufacturing emissions. Emission benefits displayed strong regional patterns consistent with relative demands for heating versus cooling and the dominant fuels used. Payback periods were generally longer using average instead of marginal emissions and were insensitive to the magnitude of electricity savings, which reflects the structure of the intermediate complexity electricity dispatch model.

Conclusions

The life cycle benefits of increased residential insulation greatly exceed the adverse impacts related to increased production across all regions, given insulation lifetimes of multiple decades. The strong regionality in benefits and the influence of a marginal modeling approach reinforce the importance of site-specific attributes and time-dynamic modeling within LCA.

     

钾肥类型对菜心(菜薹)生长、细胞保护酶和内源激素的影响

为探讨钾肥类型对菜心(Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee)的作用效应,研究了不同钾肥类型和水平对菜心生长、细胞保护酶和内源激素的影响。结果表明,氯化钾或硫酸钾处理可提高菜心叶片的POD 和CAT 活性、IAA 和GA₃ 含量,降低MDA 含量,提高菜薹产量。随着钾水平的提高,叶片IAA 和GA₃ 含量、POD 和CAT 活性以及菜薹质量明显提高,MDA 含量降低。当施钾90 kg hm^-2 时,叶片的GA₃ 和IAA 含量显著下降,而POD 活性和菜薹产量没有显著变化。在相同水平下,氯化钾与硫酸钾对植株生长、菜薹产量、叶片GA₃ 含量的影响不显著。当施钾0~90 kg hm^-2 时,氯化钾处理的叶片POD 活性显著高于硫酸钾处理;而施钾135~180 kg hm^-2 时,氯化钾处理的叶片POD 活性则显著低于硫酸钾处理。除了90 kg hm^-2 氯化钾处理的CAT 活性和45 kg hm^-2 氯化钾处理的MDA 含量低于硫酸钾处理以及90 kg hm^-2 和180 kg hm^-2 氯化钾处理的IAA 含量高于硫酸钾处理的外,相同水平氯化钾和硫酸钾处理的CAT 活性、MDA 含量和IAA 含量没有显著差异。可见,钾肥类型对菜心的活性氧代谢系统及内源激素含量有一定的影响,但氯化钾与硫酸钾对菜心的施用效果相当,生产上可采用氯化钾代替硫酸钾以节约肥料成本,K₂O 施用量以90 kg hm^-2 为宜。     

煤电一体化开发对锡林郭勒盟环境经济的影响

国家“十二五”规划确定将在内蒙古锡林郭勒盟建设国家重点大型煤电基地.煤电一体化开发将大大地推动锡盟的区域经济发展,但也可能会对这一典型草原地区和重要生态屏障地区的生态环境造成不利影响.采用物料平衡法和指数增长模型对2001-2009年锡林郭勒盟SO2排放量与人均GDP做了相关性分析,发现二者关系基本符合环境库兹涅茨曲线,呈较缓和倒U型曲线,拐点在人均GDP35000-40000元,目前已过曲线拐点,SO2排放量缓步下降.对锡盟煤电一体化开发情景下(2012-2020)的SO2排放及人均GDP进行预测,结果显示SO2排放量将随经济发展呈上升趋势,表明煤电一体化开发会使环境库兹涅茨曲线的拐点后延,虽然到2020年SO2排放量仍然没有超出区域大气环境容量,但将接近环境容量极限,会给当地环境带来明显压力;基于以上判断,进而从制度、技术、市场三方面出发,探讨了促进锡盟煤电一体化产业建设与环境保护协调发展的对策.