Life cycle energy consumption and CO2 emission of an office building in China

Purpose  

Building is one of the main factors of energy use and greenhouse gas emissions. Reducing energy consumption and carbon dioxide (CO₂) emission from building is urgent for environmental protection and sustainable development. The objective of this study is to develop a life cycle assessment (LCA) model for an office building in China to assess its energy consumption and CO₂ emission, determine the whole life cycle phases, and the significant environmental aspects that contribute most to the impact.     

Life Cycle Energy Assessment of Alternative Water Supply Systems (9 pp)

Goal, Scope and Background This paper discusses the merging of methodological aspects of two known methods into a hybrid on an application basis. Water shortages are imminent due to scarce supply and increasing demand in many parts of the world. In California, this is caused primarily by population growth. As readily available water is depleted, alternatives that may have larger energy and resource requirements and, therefore, environmental impacts must be considered. In order to develop a more environmentally responsible and sustainable water supply system, these environmental implications should be incorporated into planning decisions. Methods Comprehensive accounting for environmental effects requires life cycle assessment (LCA), a systematic account of resource use and environmental emissions caused by extracting raw materials, manufacturing, constructing, operating, maintaining, and decommissioning the water infrastructure. In this study, a hybrid LCA approach, combining elements of process-based and economic input-output-based LCA was used to compare three supply alternatives: importing, recycling, and desalinating water. For all three options, energy use and air emissions associated with energy generation, vehicle and equipment operation, and material production were quantified for life-cycle phases and water supply functions (supply, treatment, and distribution). The Water-Energy Sustainability Tool was developed to inform water planning decisions. It was used to evaluate the systems of a Northern and a Southern California water utility. Results and Discussion The results showed that for the two case study utilities desalination had 2–5 times larger energy demand and caused 2–18 times more emissions than importation or recycling, due primarily to the energy-intensity of the treatment process. The operation life-cycle phase created the most energy consumption with 56% to 90% for all sources and case studies. For each water source, a different life-cycle phase dominated energy consumption. For imported water, supply contributed 56% and 86% of the results for each case study; for desalination, treatment accounted for approximately 85%; for recycled water, distribution dominated with 61% and 74% of energy use. The study calculated external costs of air pollution from all three water supply systems. These costs are borne by society, but not paid by producers. The external costs were found to be 6% of desalinated water production costs for both case studies, 8% of imported water production costs in Southern California, and 1–2% for the recycled water systems and for the Northern California utility's imported water system. Conclusion Recycling water was found to be more energy intensive in Northern than in Southern California, but the results for imported water were similar. While the energy demand of water recycling was found to be larger than importation in Northern California, the two alternatives were competitive in Southern California. For all alternatives in both case studies, the energy consumed by system operation dominated the results, but maintenance was also found to be significant. Energy production was found to be the largest contributor in all water provision systems, followed by materials production. The assessment of external costs revealed that the environmental effects of energy and air emissions caused by infrastructure is measurable, and in some cases, significant relative to the economic cost of water. Recommendation and Perspective This paper advocates the necessity of LCA in water planning, and discusses the applicability of the described model to water utilities.     

Environmental impacts of implementing basket fans for heat abatement in dairy farms

Health and welfare impairments in dairy cows have been described to increase environmental impacts of milk production due to their negative effect on cow productivity. One of the welfare problems is heat stress, which is gaining importance even in temperate regions. While improving animal welfare may reduce emissions, the mitigation potential depends on the environmental costs associated with specific intervention measures. Taking abatement of heat stress as an example, the aim of the present study was to estimate the effect of implementing mechanical ventilation devices on the contribution potential of milk production to global warming (GWP), terrestrial acidification (TAP) and freshwater eutrophication (FEP). Environmental impacts of two modelled production systems located in alpine and lowland production areas of Austria were estimated before and after the implementation of basket fans, using life cycle assessment. Region-specific climate data were retrieved to determine the number of days with heat stress and to evaluate heat stress-induced productivity shortfalls in the baseline scenario (S_basic). In the intervention scenario with increased ventilation (S_vent), this decline was assumed to be eliminated due to the convective cooling effect of fans. For S_basic, mean GWP, TAP and FEP impacts were estimated at 1.2 ± 0.09 kg CO₂-, 21.1 ± 1.44 g SO₂- and 0.1 ± 0.04 g P-equivalents per kg milk, respectively. Independent from the production system, in S_vent, implementation of fans did not result in significant environmental impact changes, except for FEP of the alpine system (+5.9%). The latter reflects the comparatively high environmental costs of additional cooling regarding FEP (+2.3%) in contrast to GWP (+0.4%) and TAP (+0.1%). In conclusion, the estimated overall effects of mechanical ventilation on GWP, TAP and FEP of milk production were minor and the model calculations point to the potential of heat stress abatement to at least outweigh the environmental costs associated with fan production and operation. To confirm this trend, further assessments are needed, which should be based on primary data regarding the effectiveness of fan cooling to improve cow productivity, and on emission calculation schemes that are sensitive to environmental factors such as wind speed and temperature.     

Short-chained oxygenated VOC emissions in <Emphasis Type="Italic">Pinus halepensis</Emphasis> in response to changes in water availability

Short-chained oxygenated VOC (oxVOCs) emissions from Pinus halepensis saplings were monitored in response to changes in water availability. Online measurements were made with a proton transfer reaction—mass spectrometer under controlled conditions, together with CO₂ and H₂O exchange measurements. Masses corresponding to methanol and acetone were the most emitted oxVOCs. All the oxVOC exchanges, except that of acetone (M59), were significantly related to stomatal conductance and transpiration. Acetaldehyde (M45) emission showed, moreover, a strong dependence on the concentration of acetaldehyde in the ambient: stomatal opening (stomatal conductance above 75 mmol m⁻² s⁻¹) only allowed increased emissions when external concentration were below 6 ppb. Acetone (M59) presented an important peak of emission following light and stomatal opening in the morning when plants were water stressed. Thus, the alterations in oxVOC emissions in P. halepensis caused by the water deficit seem to be mainly driven by water stress effect on stomatal closure and oxVOC air concentrations.     

An Analysis of Costs and Health Co-Benefits for a U.S. Power Plant Carbon Standard

Reducing carbon dioxide (CO₂) emissions from power plants can have important “co-benefits” for public health by reducing emissions of air pollutants. Here, we examine the costs and health co-benefits, in monetary terms, for a policy that resembles the U.S. Environmental Protection Agency’s Clean Power Plan. We then examine the spatial distribution of the co-benefits and costs, and the implications of a range of cost assumptions in the implementation year of 2020. Nationwide, the total health co-benefits were $29 billion 2010 USD (95% CI: $2.3 to $68 billion), and net co-benefits under our central cost case were $12 billion (95% CI: -$15 billion to $51 billion). Net co-benefits for this case in the implementation year were positive in 10 of the 14 regions studied. The results for our central case suggest that all but one region should experience positive net benefits within 5 years after implementation.     

Land use planning in Ireland—a life cycle energy analysis of recent residential development in the Greater Dublin Area

Background, aim, and scope  One third of the total housing stock in the Republic of Ireland has been built in 10 years up to and including 2006 and of this approximately 34% was built in the Greater Dublin Area (GDA). Much of the housing was low-density with poor public transport links leading to doubts over its sustainability—particularly in terms of energy use. Although the country is committed to reducing greenhouse gas emissions to 13% above 1990 levels by the period 2008–2012, by 2005, emissions were already 25.4% higher than the baseline and current projections are that this figure will rise to 37% over the period. The residential sector is estimated to contribute to approximately 24.5% of energy-related CO₂ emissions. This paper estimates total emissions from residential developments in the GDA constructed between 1997 and 2006. Materials and methods  Carbon dioxide equivalent (CO₂) emissions are estimated using a life cycle assessment approach over a 100-year building lifespan and employing process, input–output and hybrid energy techniques. Life cycle stages include: construction, operation, transport, maintenance and demolition. The main data sources include: national population and industry census data, household travel survey data, residential energy performance surveys and national accounts. The GDA was split into four zones each encompassing development at increasing radii from Dublin’s city centre, namely: city centre, suburbs, exurbs and commuter towns. Results  Per capita CO₂ life cycle emissions in the GDA were found to be approximately 50–55% greater in the exurbs and commuter towns than in the city centre. Of the five life cycle stages studied, operational energy requirements (predominantly space heating and hot water, but including power) contributed most significantly to emissions (68%), followed by transport (17%), construction (9%) and maintenance/renovation (6%). Discussion  Operating emissions from dwellings in the commuter town and extra-urban zones were almost twice those in the city centre both due to larger dwelling sizes and the predominance of detached and semi-detached dwellings (with large amounts of exposed walls) in the former and the prevalence of smaller apartments in the latter. Car use was most pronounced in the zones furthest from the city centre where per capita emissions were almost twice those of residents in the city centre. Despite their smaller size, the per capita construction CO₂ emissions of apartments were approximately one third greater than for low-rise dwellings due to the greater energy intensity of the structure. However, this difference was more than compensated for by the significantly lower operational emissions referred to above. Conclusions  In 2006, recurrent CO₂ emissions (operational, transport and maintenance) from dwellings built in the GDA over the ten preceding years were 2,108 kt while construction-related emissions in that year were 1,325 kt giving a total contribution from the residential sector of 3,434 kt CO₂/annum—representing 4.9% of national emissions for that year. Had the development policy prescribed ‘city centre’-type development and transport modes, then emissions for the year 2006 would have been 2,892 kt CO₂—a reduction of almost 16% over the actual figure. However, in this scenario recurrent emissions would have been reduced to 1,417 kt CO₂—a reduction of 33% over actual levels. Recommendations and perspectives  This study supports Irish and international governments’ policies aimed at curbing CO₂ emissions from the domestic sector which focus primarily on reducing operational emissions from new and existing housing through design and construction improvements. However, it demonstrates that significant reductions in operational emissions are associated with high-density residential development with modest floor areas. Furthermore, it highlights the scope for transport emissions’ reductions through better spatial planning leading to reduced car travel.     

Utilization of woody biomass in Singapore: technological options for carbonization and economic comparison with incineration

Background, aim and scope  The interest in the use of biomass as a renewable energy resource has rapidly grown over the past few years. In Singapore, biomass resources are mostly from waste wood. This article presents a few technological options, namely carbonization, for the conversion of woody biomass into a solid fuel, charcoal. Materials and methods  In the first stage, a life cycle assessment (LCA) ‘gate-to-gate’ system was developed for a conventional carbonizer system, a modern carbonizer from Japan, and a proposed four-stage partial furnace carbonizer from Tunisia. The potential environmental impacts were generated for global warming potential, acidification, human toxicity and photochemical oxidant potential. Based on the first set of results, the second LCA investigation was carried out comparing the selected carbonizer from Japan and an existing incinerator in Singapore. The second LCA adopted a unique approach combining social costs of pollution with the economic factors of the two biomass conversion technologies. Results  The carbonizer from Japan resulted in approximately 85% less greenhouse gases than the conventional carbonization system and 54% less than the proposed four-stage carbonizer from Tunisia. In terms of acidification and human toxicity, the carbonizers from Japan and Tunisia display nearly similar results—both were considerably lower than the conventional carbonizer. For photochemical oxidant potential, very minimal emissions are generated from the four-stage carbonizer and nearly zero impact is realized for the carbonization technology from Japan. Discussion  From the first set of LCA results, the Japanese carbonizer is favored in terms of its environmental results. The highest environmental impacts from the conventional carbonizer were due to large and uncontrolled emissions of acidic gases, greenhouse gases (particularly CO₂ and CH₄), particulates, and non-methane volatile organic compounds from both fugitive sources and energy requirements. The second LCA addressed the performance of the carbonizer from Japan against an existing incinerator in terms of environmental as well as cost performances. This unique approach translated pollution emissions into monetary costs to highlight the impacts of social health. Conclusions  For the first LCA, the accumulated impacts from the Japanese carbonizer proved to display significantly lower environmental impacts, especially for global warming potential. The overall environmental performance of the four-stage carbonizer from Tunisia ranked slightly lower than the one from Japan and much higher than the conventional carbonizer. The second LCA results displayed a noteworthy improvement of 90% for human health from the modern Japanese carbonizer technology—when compared against conventional incinerators. Without considering health issues or social costs, the total value per ton of wood treated is nearly similar for both incinerator and carbonizer. Recommendations and perspectives  The interest in biomass as raw material for producing energy has emerged rapidly in many countries. However, careful analysis and comparison of technologies are necessary to ensure favorable environmental outcomes. A full life cycle study, along with costs and the impact of pollution on society, should be performed before any large-scale biomass conversion technology is implemented. LCA can be applied to quantify and verify the overall environmental performance of a particular technology of interest as well as further explore the proposed technology in terms of costs and social implications.     

Domestic water versus imported virtual blue water for agricultural production: A comparison based on energy consumption and related greenhouse gas emissions

The supply of water, food, and energy in our global economy is highly interlinked. Virtual blue water embedded into internationally traded food crops has therefore been extensively researched in recent years. This study focuses on the often neglected energy needed to supply this blue irrigation water. It provides a globally applicable and spatially explicit approach to the watershed level for water source specific quantification of energy consumption and related greenhouse gas (GHG) emissions of irrigation water supply. The approach is applied to Israel's total domestic and imported food crop supply of 105 crops by additionally including import-related transportation energy and emissions. Total energy use and related emissions of domestic crop production were much lower (551 GWh/422 kt CO₂-equivalents [CO₂e]) than those embedded into crop imports (1639 GWh/649 kt CO₂e). Domestic energy and emissions were mainly attributable to the irrigation water supply with artificial water sources (treated domestic wastewater and desalinated water, 84%). Transport accounted for 79% and 66% of virtually imported energy and emissions, respectively. Despite transport, specific GHG emissions (CO₂e per ton of crop) were significantly lower for several crops (e.g., olives, almonds, chickpeas) compared to domestic production. This could be attributed to the high share of energy-intensive artificial water supply in combination with higher irrigation water demands in Israel. In the course of an increasing demand for artificial water supply in arid and semi-arid regions, our findings point to the importance of including “energy for water” into comparative environmental assessment of crop supply to support decision-making related to the water–energy–food nexus.     

Effect of cooling strategies on overall performance of a hybrid personal cooling system incorporated with phase change materials (PCMs) and electric fans

The effect of four cooling strategies on cooling performance of a hybrid personal cooling system (HPCS) incorporated with phase change materials (PCMs) and electric fans in a hot environment (i.e., T_air = 36 ± 0.5 °C, RH = 59 ± 5%) was investigated. Twelve healthy young male participants underwent four 90-min trials comprising 70 min walking and 20 min resting periods. Cooling strategies adopted in this work were CON (control), PCM-control (PCMs were removed at the end of exercise), Fan-control (fans were switched OFF during the initial 20 min) and PCM&Fan-control (fans were turned ON after 20 min exercising and PCMs were removed after the 70-min exercise). Results demonstrated that the control of electric fans could suppress the mean skin temperature rise to 34.0 °C by over 15 min and also cut down the energy consumption of the HPCS from 15.6 W h to 12.1 W h over the entire 90-min trials. Thus, it is recommended that fans should be turned off at the beginning of hot exposure and switched on once participants felt warm. Our findings also showed that the removal of fully melted PCM packs from the HPCS could enhance the evaporative cooling effect brought about by air circulation. The removal of melted PCMs significantly reduced the physical load by 37.3% and ratings of perceived exertion (RPE) were decreased by 3.5–4.2 RPE units. This could also help quickly restore the PCM energy for future usage. In summary, cooling strategies demonstrated in this work could improve HPCS's overall cooling performance on workers while working in the studied hot environment.     

Including albedo in time‐dependent LCA of bioenergy

Albedo change during feedstock production can substantially alter the life cycle climate impact of bioenergy. Life cycle assessment (LCA) studies have compared the effects of albedo and greenhouse gases (GHGs) based on global warming potential (GWP). However, using GWP leads to unequal weighting of climate forcers that act on different timescales. In this study, albedo was included in the time‐dependent LCA, which accounts for the timing of emissions and their impacts. We employed field‐measured albedo and life cycle emissions data along with time‐dependent models of radiative transfer, biogenic carbon fluxes and nitrous oxide emissions from soil. Climate impacts were expressed as global mean surface temperature change over time (?T) and as GWP. The bioenergy system analysed was heat and power production from short‐rotation willow grown on former fallow land in Sweden. We found a net cooling effect in terms of ?T per hectare (?3.8 × 10^–11 K in year 100) and GWP₁₀₀ per MJ fuel (?12.2 g CO₂e), as a result of soil carbon sequestration via high inputs of carbon from willow roots and litter. Albedo was higher under willow than fallow, contributing to the cooling effect and accounting for 34% of GWP₁₀₀, 36% of ?T in year 50 and 6% of ?T in year 100. Albedo dominated the short‐term temperature response (10–20 years) but became, in relative terms, less important over time, owing to accumulation of soil carbon under sustained production and the longer perturbation lifetime of GHGs. The timing of impacts was explicit with ?T, which improves the relevance of LCA results to climate targets. Our method can be used to quantify the first‐order radiative effect of albedo change on the global climate and relate it to the climate impact of GHG emissions in LCA of bioenergy, alternative energy sources or land uses.     

Life-cycle assessment and cost analysis of residential buildings in South East of Turkey: part 2—a case study

Purpose

Residential buildings play an important role in consumption of energy resources. About 40 % of all primary energy is used in buildings all over the world. This paper is the second part of the study on the life-cycle energy (LCEA), emissions (LCCO₂A) and cost (LCCA) assessment of two residential buildings constructed in urban and rural areas.

Methods

In the first part, the methodology, formulations and procedure for such a comprehensive analysis are provided, while this paper provides an application of the methodology that considers two actual buildings located in Gaziantep, Turkey. The proposed model focused on building construction, operation and demolition phases to estimate energy use, carbon emissions and costs per square meter over a 50-year lifespan. The optimum thickness of insulation used to reduce energy consumption and emissions per square meter is determined.

Results and discussion

It is found that the operating phase is dominant in both urban and rural residential buildings and contributes 87–85 % of the primary energy requirements and 88–82 % of CO₂ emissions, respectively. Life-cycle greenhouse gas emissions were 5.8 and 3.9 tons CO₂ eqv. for BT1 and BT2, respectively. It is calculated that the life-cycle energy consumption and CO₂ emissions of the residential buildings can be reduced by up to 22.8 and 23.4 %, respectively, by using a proper insulation material for the external walls. The life-cycle cost, consisting of mortgage, energy, maintenance, service and demolition payments are calculated to be 7.28 and 1.72 million USD for BT1 and BT2, respectively.

Conclusions

Building envelope developments, such as better wall insulation, provide noteworthy potential energy savings and contribute to the reductions from cooling and space heating. Therefore, primary strategies and technologies needed for efficient buildings include optimal insulation of external walls. The economic insulation thickness of the residential buildings in Gaziantep is determined to be 80 mm by using a life-cycle cost analysis. The results show that because of the differences in building structures and living standards, life-cycle energy intensity and CO₂ emissions in urban residential buildings are 29 and 25 % higher than in rural conditions.

     

Global ammonia emissions from synthetic nitrogen fertilizer applications in agricultural systems: Empirical and process‐based estimates and uncertainty

Excessive ammonia (NH₃) emitted from nitrogen (N) fertilizer applications in global croplands plays an important role in atmospheric aerosol production, resulting in visibility reduction and regional haze. However, large uncertainty exists in the estimates of NH₃ emissions from global and regional croplands, which utilize different data and methods. In this study, we have coupled a process‐based Dynamic Land Ecosystem Model (DLEM) with the bidirectional NH₃ exchange module in the Community Multiscale Air‐Quality (CMAQ) model (DLEM‐Bi‐NH₃) to quantify NH₃ emissions at the global and regional scale, and crop‐specific NH₃ emissions globally at a spatial resolution of 0.5° × 0.5° during 1961–2010. Results indicate that global NH₃ emissions from N fertilizer use have increased from 1.9 ± 0.03 to 16.7 ± 0.5 Tg N/year between 1961 and 2010. The annual increase of NH₃ emissions shows large spatial variations across the global land surface. Southern Asia, including China and India, has accounted for more than 50% of total global NH₃ emissions since the 1980s, followed by North America and Europe. Rice cultivation has been the largest contributor to total global NH₃ emissions since the 1990s, followed by corn and wheat. In addition, results show that empirical methods without considering environmental factors (constant emission factor in the IPCC Tier 1 guideline) could underestimate NH₃ emissions in context of climate change, with the highest difference (i.e., 6.9 Tg N/year) occurring in 2010. This study provides a robust estimate on global and regional NH₃ emissions over the past 50 years, which offers a reference for assessing air quality consequences of future nitrogen enrichment as well as nitrogen use efficiency improvement.     

Bio-pretreatment of municipal solid waste prior to landfilling and its kinetics

The conventional landfilling does not promote sustainable waste management due to uncontrolled emissions which potentially degrade the environment. Pretreatment of municipal solid waste prior to landfilling significantly enhances waste stabilization, reduces the emissions and provides many advantages. Therefore, pretreatment of municipal solid waste methods were investigated. The major objectives of biological pretreatment are to degrade most easily degradable organic matters of MSW in a short duration under controlled conditions so as to produce desired quality for landfill. To investigate the suitable pretreatment method prior to landfilling for developing countries four pretreatment simulators were developed in the laboratory: (i) anaerobic simulator (R₁), (ii) aerobic pretreatment simulator by natural convection of air (R₂), (iii) aerobic pretreatment simulator by natural convection of air with leachate recirculation (R₃) and (iv) forced aeration and leachate recirculation (R₄). During the pretreatment organic matter, elemental composition, i.e., carbon, hydrogen, nitrogen and settlement were determined for bench scale experiments. A two-component kinetic model is proposed for the biodegradation of organic matter. Biodegradation kinetic constants were determined for readily and slowly degradable organic matter. The biodegradation of organic matter efficiency in terms of kinetic rate constants for the pretreatment simulators was observed as R₄ > R₃ > R₂ > R₁. Biodegradation rate constants for readily degradable matter in simulators R₄ and R₃ were 0.225 and 0.222 per day. R₃ and R₄ simulators were more effective in reducing methane emissions about 45% and 55%, respectively, as compared to anaerobic simulator R₁. Pretreatment of MSW, by natural convection of air with leachate recirculation R₃ is sustainable method to reduce the emissions and to stabilize the waste prior to landfilling.     

Temporal Aspects in Evaluating the Greenhouse Gas Mitigation Benefits of Using Residues from Forest Products Manufacturing Facilities for Energy Production

Methods for carbon footprinting typically combine all emissions into a single result, representing the emissions of greenhouse gases (GHGs) over the life cycle. The timing of GHG impacts, however, has become a matter of significant interest. In this study, two approaches are used to characterize the timing of GHG emission impacts associated with the production of energy from various biomass residues produced by the forest products industry. The first approach accounts for the timing of emissions and characterizes the impact using Intergovernmental Panel on Climate Change (IPCC) 100‐year global warming potentials (GWPs). The second is a dynamic carbon footprint approach that considers the timing of the GHG emissions, their fate in the atmosphere, and the associated radiative forcing as a function of time. The two approaches generally yield estimates of cumulative impacts over 100 years that differ by less than 5%. The timing of impacts, however, can be significantly affected by the approach used to characterize radiative forcing. For instance, the time required to see net benefits from a system using woody mill residues (e.g., bark and sawdust) is estimated to be 1.2 years when using a fully dynamic approach, compared to 7.5 years when using 100‐year GWPs, with the differences being primarily attributable to methane (CH₄). The results obtained for a number of different biomass residue types from forest products manufacturing highlight the importance of using a fully dynamic approach when studying the timing of emissions impacts in cases where emissions are distributed over time or where CH₄ is a significant contributor to the emissions.     

The Environmental Foodprint of Obesity

Emissions of greenhouse gases (GHG) are linked to global warming and adverse climate changes. Meeting the needs of the increasing number of people on the planet presents a challenge for reducing total GHG burden. A further challenge may be the size of the average person on the planet and the increasing number of people with excess body weight. We used data on GHG emissions from various sources and estimated that obesity is associated with ~20% greater GHG emissions compared with the normal‐weight state. On a global scale, obesity contributes to an extra GHG emissions of ~49 megatons per year of CO₂ equivalent (CO₂eq) from oxidative metabolism due to greater metabolic demands, ~361 megatons per year of CO₂eq from food production processes due to increased food intake, and ~290 megatons per year of CO₂eq from automobile and air transportation due to greater body weight. Therefore, the total impact of obesity may be extra emissions of ~700 megatons per year of CO₂eq, which is about 1.6% of worldwide GHG emissions. Inasmuch as obesity is an important contributor to global GHG burden, strategies to reduce its prevalence should prioritize efforts to reduce GHG emissions. Accordingly, reducing obesity may have considerable benefits for both public health and the environment.     

Reducing cooling load and lifecycle cost for residential buildings: a case of Lahore,Pakistan

Purpose

Buildings consume a large amount of energy for space cooling during the summer season, creating an overall sustainability concern. The upfront cost associated with sustainability repels the decision-makers to often end up adopting solutions that have huge operations and maintenance costs. Therefore, the purpose of this study is to assess the lifecycle cost (LCC) implications of optimum configurations of active and passive strategies for reducing the cooling load in buildings.

Methods

Several green building active and passive strategies and technologies were assimilated and their thermal performance in a hot semi-arid climate of Lahore in Pakistan using DesignBuilder V6.1 was simulated to obtain the most optimum cooling load configuration. Furthermore, LCC is estimated, and overall efficiency is evaluated to identify the most effective space cooling configuration.

Results and discussion

The results suggest that a configuration of EPS for external wall insulation, vertical louvers for external shading, 6 mm blue HRG (low-E soft coated)?+?12 mm air space?+?6 mm clear glass for windows, polystyrene as roof insulation, cross ventilation through windows, and LED lighting system has the best performance. This is the first-of-its-kind study in the hot semi-arid climate of South Asia with the city of Lahore in Pakistan as the test case and can be generalized for places with similar conditions. The findings will help the decision-makers in selecting the most load-efficient and cost-effective green building technologies to help improve overall sustainability.

Conclusion

The implementation of the proposed strategies not only aids in providing user-friendly and effective decision-making but also promotes the adoption of sustainability in buildings by leveraging the existing green building technologies to enhance the environmental and economic aspects. This is a promising approach to facilitate the spread of green building construction in developing countries. It is recommended to utilize the strategies grouped in Scenario 8 to achieve a reduced cooling load and LCC of a residential building throughout its lifecycle.

     

Bat thermoregulation in the heat: Limits to evaporative cooling capacity in three southern African bats

High environmental temperatures pose significant physiological challenges related to energy and water balance for small endotherms. Although there is a growing literature on the effect of high temperatures on birds, comparable data are scarcer for bats. Those data that do exist suggest that roost microsite may predict tolerance of high air temperatures. To examine this possibility further, we quantified the upper limits to heat tolerance and evaporative cooling capacity in three southern African bat species inhabiting the same hot environment but using different roost types (crevice, foliage or cave). We used flow-through respirometry and compared heat tolerance limits (highest air temperature (T_a) tolerated before the onset of severe hyperthermia), body temperature (T_b), evaporative water loss, metabolic rate, and maximum cooling capacity (i.e., evaporative heat loss/metabolic heat production). Heat tolerance limits for the two bats roosting in more exposed sites, Taphozous mauritianus (foliage-roosting) and Eptesicus hottentotus (crevice-roosting), were T_a = ~44 °C and those individuals defended maximum T_b between 41 °C and 43 °C. The heat tolerance limit for the bat roosting in a more buffered site, Rousettus aegyptiacus (cave-roosting), was T_a = ~38 °C with a corresponding T_b of ~38 °C. These interspecific differences, together with a similar trend for higher evaporative cooling efficiency in species occupying warmer roost microsites, add further support to the notion that ecological factors like roost choice may have profound influences on physiological traits related to thermoregulation.     

High manoeuvring costs force narrow-winged molossid bats to forage in open space

Molossid bats are specialised aerial-hawkers that, like their diurnal ecological counterparts, swallows and swifts, hunt for insects in open spaces. The long and narrow wings of molossids are considered energetically adapted to fast flight between resource patches, but less suited for manoeuvring in more confined spaces, such as between tree-tops or in forest gaps. To understand whether a potential increase in metabolic costs of manoeuvring excludes molossids from foraging in more confined spaces, we measured energy costs and speed of manoeuvring flight in two tropical molossids, 18 g Molossus currentium and 23 g Molossus sinaloae, when flying in a ~500 m³ hexagonal enclosure (~120 m² area), which is of similar dimensions as typical forest gaps. Flight metabolism averaged 10.21 ± 3.00 and 11.32 ± 3.54 ml CO₂ min⁻¹, and flight speeds 5.65 ± 0.47 and 6.27 ± 0.68 m s⁻¹ for M. currentium and M. sinaloae respectively. Metabolic rate during flight was higher for the M. currentium than for the similar-sized, but broader-winged frugivore Carollia sowelli, corroborating that broad-winged bats are better adapted to flying in confined spaces. These higher metabolic costs of manoeuvring flight may be caused by having to fly slower than the optimal foraging speed, and by the additional metabolic costs for centripetal acceleration in curves. This may preclude molossids from foraging efficiently between canopy trees or in forest gaps. The surprisingly brief burst of foraging activity at dusk of many molossids might be related to the cooling of the air column after sunset, which drives airborne insects to lower strata. Accordingly, foraging activity of molossids may quickly turn unprofitable when the abundance of insects decreases above the canopy.     

Environmental effects from a recycling rate increase of cardboard of aseptic packaging system for milk using life cycle approach

Goal, Scope and Background  Despite the well-known advantages of recycling materials to reduce solid waste or save natural resources, the recycling stage is an additional process within the life cycle that has its own energy and input requirements, as well as specific emissions. The objective of the present paper is to analyze the life cycle inventory associated with the increase in recycling rate (from 2% up to 22% at present) of the cardboard contained in the aseptic packaging for long-life milk. The main aspects of the manufacturing of the Tetra Pak aseptic package, including the filling of the product, the distribution of the conditioned product, up to the final disposal and recycling rates, were considered. Materials and Methods  This study was conducted in accordance with the general directives of the ISO 14040 series. The packaging material system was assessed using 1000 liters of milk as a functional unit, in a packaging system containing 12 units of 1 L cartons each, placed on a corrugated paperboard tray wrapped in polyethylene shrink film and arranged onto one-way wooden pallets. Brazilian inventories for energy, carton, corrugated paperboard and aluminum, based on site-collected data were employed. The final disposal of used packages was modeled using the Average Brazilian Municipal Solid Waste Management data collected for the purpose of the census of the year 2000. Results  Comparison of the total energy consumption throughout the whole life cycle of two recycling scenarios (i.e. different recycling rates) analyzed shows that the higher recycling rate led to a 6% reduction of the total energy requirement for the long-life milk package material system. The most significant reductions in the consumption of natural resources were: 8% water, 11% wood and 10% land use savings. Greenhouse gases were the main reduced air emissions and contributed with a reduction of 9.7% in GWP. Most water emissions were reduced: 10% COD, 9% BOD and 6% TSS. A unique drawback directly caused by the increase of the recycling rate was an increase of 14.4 g in TDS emissions (57%). Discussion  The reduction in energy requirements are related and limited to the proportionality among the different materials that make up the packaging system. Most emission reductions result from the replacement of virgin materials with recycled materials in the packaging system. Although the average balance of water emissions is positive, the need to improve wastewater treatment processes in the paper recycling plants to reduce TDS is highlighted as a key issue. Conclusions  It may be concluded that the increase in the recycling rate brings about a series of benefits in terms of reduction of energy and natural resource consumption, air pollutants and most water emissions. In this case, the increase of the recycling rate improved the overall environmental performance of the aseptic Tetra Pak system for milk. Recommendations and Perspectives  The authors are currently analyzing alternative recycling scenarios that will enable one to evaluate maximum reduction in GWP. Further studies could include the agriculture stages, livestock and consumer phase to broaden the environmental evaluation. ESS-Submission Editor: Dr. Andreas A. Detzel (andreas.detzel@ifeu.de)     

No significant nitrous oxide emissions during spring thaw under grazing and nitrogen addition in an alpine grassland

A recent study (Wolf et al., 2010) suggests that short—lived pulses of N₂O emission during spring thaw dominate the annual N₂O budget and that grazing decreases N₂O emissions during the spring thaw. To verify this we conducted year—round N₂O flux measurements from June 2010 to May 2011 in Tianshan alpine grassland in central Asia. No pulse emissions of N₂O were found at grazing management sites and nitrogen addition sites during the spring thaw. The contribution of the spring thaw to the total annual N₂O budget was small and accounted for only 6.6% of the annual fluxes, with winter emissions accounting for 16.7% and growing season emissions accounting for 76.7%. The difference in N₂O emissions attributable to grazing management was not significant (P > 0.05). Nitrogen input tended to increase N₂O emissions at N addition sites during the grass growing season compared with those at unfertilized sites. N₂O fluxes showed a significant correlation with air temperature and also with both soil temperature and soil water content at 10 cm depth.