Machine learning based modeling of households: A regionalized bottom‐up approach to investigate consumption‐induced environmental impacts

As major drivers of economy, households induce a large share of worldwide environmental impacts. The variability of local consumption patterns and associated environmental impacts needs to be quantified as an important starting point to devise targeted measures aimed at reducing household environmental footprints. The goal of this article is the development and appraisal of a comprehensive regionalized bottom‐up model that assesses realistic environmental profiles for individual households in a specific region. For this purpose, a physically based building energy model, the results of an agent‐based transport simulation, and a data‐driven household consumption model were interlinked within a new probability‐based classification framework and applied to the case of Switzerland. The resulting model predicts the demands in about 400 different consumption areas for each Swiss household by considering its particular circumstances and produces a realistic picture of variability in household environmental footprints. An analysis of the model results on a municipal level reveals per‐capita income, population density, buildings' age, and household structure as possible drivers of municipal carbon footprints. While higher‐emission municipalities are located in rural areas and tend to show higher shares of older buildings, lower‐emission communities have larger proportions of families and can be found in highly populated regions by trend. However, the opposing effects of various variables observed in this analysis confirm the importance of a model that is able to capture regional distinctions. The overall model constitutes a comprehensive information base supporting policymakers in understanding consumption patterns in their region and deriving environmental strategies tailored to their specific population.     

典型社区家庭消费碳排放特征与影响因素——以北京市为例

家庭消费碳排放是中国碳排放总量的重要组成部分,已成为碳排放增长的主要驱动力,从消费角度研究家庭碳排量特征及影响因素对家庭碳减排和低碳社区建设有重要意义。使用碳排放系数法和消费者生活方式法计算北京市5种典型社区家庭消费月均碳排量,通过最优尺度回归和多重比较分析对不同社区家庭碳排放影响因素进行探究。研究发现：北京市5种社区户均碳排放总量及构成差异显著,影响因素不一致。其中：（1）平房类社区家庭直接碳排量732.26 kgCO₂/月高于其他社区,燃煤取暖是平房社区家庭直接碳排放高的主要因素,单位社区、政策性住房社区和商品房社区家庭直接碳排量较低,约50.00 kgCO₂/月。家庭类型显著影响每个社区家庭直接碳排量,家庭积极参与节能环保活动有利于减少家庭直接碳排放;（2）商品房社区家庭间接碳排量最高,达3879.06 kgCO₂/月,平房类社区家庭最低,间接碳排量仅为商品房社区的1/3,间接碳排放是家庭生活消费碳排放的主体。食品和居住消费产生的间接碳排量较高,老龄化社区家庭医疗保健消费碳排量更高;（3）家庭类型和月总收入对所有社区家庭间接碳排量影响显著,但社区环保工作满意度、社区环境满意度、家庭节能环保活动参与度、耐用品使用年限等因素影响程度存在差异,胡同社区和平房类社区中受教育水平高的家庭产生的间接碳排量更高,需积极灌输环保理念。进一步分析了主要影响因素在不同水平下对应的家庭碳排量差异程度与变化规律,有助于社区管理者识别高碳排家庭,为社区低碳管理提供新思路。     

2004—2014年南方稻区双季稻生产碳足迹动态及其构成

南方稻作区是我国重要的粮食生产区,在国家粮食安全保障中起着至关重要的作用,探明南方不同省份双季稻生产的碳足迹差异,对促进低碳稻作农业发展具有重要意义.本研究采用2004—2014年农作物种植面积、农资投入等统计数据,运用碳足迹理论和生命周期法系统评价我国南方双季稻生产碳足迹时空分布状况及其构成.结果表明: 南方稻区各个省份早晚稻生产碳足迹大部分表现为增加趋势,早稻生产碳足迹较晚稻大.2004—2014年,安徽省双季稻平均碳足迹最高(1000 kg CO₂-eq·hm^-2),而福建、湖北和湖南省相对较小(750 kg CO₂-eq·hm^-2).碳足迹构成中以肥料的生产、运输及使用占比最大,占水稻生产总碳足迹的60%;柴油投入碳足迹贡献量次之,为26%左右.逐步回归分析表明,双季稻生产碳足迹大小与柴油、复混肥和钾肥的投入呈正相关.净利润收益纳入分析表明,湖北省为低排放-高收益省份,有利于农业低碳可持续性发展.随着农村劳动力非农化和作物生产机械化的快速递增,未来水稻生产中柴油等机械化碳投入将快速增长.因此,提升化肥利用效率、灌溉效率和机械化作业效率将是发展南方稻作区低碳农业的关键途径.     

Contribution of “Women’s Gold” to West African Livelihoods: The Case of Shea (<Emphasis Type="Italic">Vitellaria paradoxa</Emphasis>) in Burkina Faso

Contribution of “Women’s Gold” to West African Livelihoods: The Case of Shea ( Vitellaria paradoxa ) in Burkina Faso. This paper (i) quantifies the contribution that Vitellaria paradoxa makes to the total income of rural households belonging to different economic groups in two areas of Burkina Faso; (ii) quantifies the involvement of women in shea nuts and fruits collection and processing; and (iii) empirically verifies the “gap filling” function of shea products in Burkina Faso by quantifying the commercialization and subsistence use of shea fruits, nuts, and butter between agricultural seasons. Based on data collected from structured household surveys used on a quarterly basis during a one-year period on 536 households, we demonstrate that the reliance on shea is generally high in the sampled populations, and is at its highest for the poorest households, for which it contributes 12 % of total household income. Moreover, shea nut collection and processing was found to provide a valuable source of cash income to female household members who otherwise have very few income possibilities. Finally, due to its ecology, shea fills in an income gap during a period where human activities are at their highest while income is at its lowest. Although shea is crucial for poor people’s livelihoods and for the generation of income for women, its harvesting and processing are time-consuming activities that generate low returns per unit of labor. We argue that shea collection and processing should therefore not be considered as a remedy to poverty but instead as a way for households to diversify their livelihood strategy and decrease their vulnerability to food insecurity and climate variability.     

Capital in the American carbon,energy, and material footprint

Stocks of fixed capital play a vital role in fulfilling basic human needs and facilitating industrial production. Their build‐up requires great quantities of energy and materials, and generates greenhouse gas emissions and other pollution. Capital stocks influence economic production and environmental pollution through their construction and over subsequent decades through their use. We perform an environmental footprint analysis of total consumption, capital investment, and capital consumption in the United States for 2007 and 2012. In 2012, capital consumption accounted for 13%, 19%, and 40% of total carbon, energy, and material footprints, respectively. Housing, federal defense, state and local government education and other services (including household consumption of roads), personal transport fuels, and hospitals are the consumption sectors with largest capital footprints. These sectors provide fundamental needs of shelter, transport, education, and health, underlying the importance of capital services. Endogenizing capital causes the biggest proportional increase to footprints of sectors with low environmental multipliers. This work builds upon existing input‐output models of production and consumption in the United States, and provides a capital‐inclusive database of carbon, energy, and material footprints and multipliers for 2007 and 2012. This article met the requirements for a gold – gold JIE data openness badge described at http://jie.click/badges .     

The Importance of Bushmeat in the Livelihoods of West African Cash-Crop Farmers Living in a Faunally-Depleted Landscape

Bushmeat is an important resource in the livelihoods of many rural communities in sub-Saharan Africa and may be a crucial safety-net for the most vulnerable households, especially during times of economic hardship. However, little is known about the impacts of wildlife depletion on these functions. This study quantifies the role of bushmeat in diversified rural household economies in a wildlife depleted forest-farm landscape in Ghana, assessing its importance overall, as well as differentiated by the relative vulnerability of households. Using repeat socioeconomic questionnaires (N=787) among 63 households over a one-year period, the following hypotheses were tested: (a) vulnerable households harvest more bushmeat; (b) bushmeat contributes a greater proportion of household production in vulnerable households; (c) bushmeat is more important for cash income than consumption in vulnerable households; and (d) bushmeat sales are more important for vulnerable households. The bushmeat harvest value averaged less than US$1.0 per day for 89% of households and comprised less than 7% of household production value. Household wealth and gender of the household head had little effect on the importance of bushmeat. However, bushmeat harvest and sales were highest during the agricultural lean season. Overall, most harvested bushmeat (64%) was consumed, enabling households to spend 30% less on meat/fish purchases. These findings suggest that, despite heavily depleted wildlife and diversified livelihoods, bushmeat continues to have an important role in rural livelihoods by acting as a safety net for income smoothing and reducing household expenditure during times of economic hardship.     

川西亚高山5种森林生态系统的碳格局

采用样方法研究了川西亚高山白桦(Betula platyphylla)林(BF)、针阔混交林(MF)、岷江冷杉(Abies faxoniana)林(FF)、紫果云杉(Picea purpurea)林(SF)和方枝柏(Sabina saltuaria)林(CF)的碳贮量、组成及其分布格局。结果表明: 1)在5种森林生态系统中, 土壤碳含量和碳贮量都随土壤深度的增加而极显著地降低, 且与土壤深度之间有较好的线性关系; 2)地被物碳贮量分别为SF(23.97±1.77)>FF(21.35±3.64)>MF(11.78±1.21)>CF(9.09±0.91) >BF(8.16±1.34) 10³kgC·hm^-2, 对生态系统总碳贮量的贡献率差异不显著, 约占3%~4%; 3)乔木层对植物碳贮量贡献最多, 根系碳贮量占植物碳贮量的比例在13%~19%之间; 4)SF和FF的碳贮存以植物为主, MF、BF和CF的碳贮存则以土壤为主; 5)整个生态系统的碳贮量依次为SF(729.92±43.49)>FF(618.86±53.97)>MF(353.88±21.76)>BF(247.79± 17.15)>CF(244.52±18.70) 10³ kgC·hm^-2, 差异显著, 对应的短期碳固定能力则依次为2.97、3.80、5.15、3.33和4.84 10³ kgC·hm^-2·a^-1。在没有破坏性干扰前提下, 川西亚高山次生林恢复是大气中碳沉降的潜在碳汇。合适的树种及其搭配比例、造林模式和森林生态系统管理对策, 是促进该区域植被快速恢复和增加碳贮存的关键。     

Effect of land‐use and land‐cover change on mangrove blue carbon: A systematic review

Mangroves shift from carbon sinks to sources when affected by anthropogenic land‐use and land‐cover change (LULCC). Yet, the magnitude and temporal scale of these impacts are largely unknown. We undertook a systematic review to examine the influence of LULCC on mangrove carbon stocks and soil greenhouse gas (GHG) effluxes. A search of 478 data points from the peer‐reviewed literature revealed a substantial reduction of biomass (82% ± 35%) and soil (54% ± 13%) carbon stocks due to LULCC. The relative loss depended on LULCC type, time since LULCC and geographical and climatic conditions of sites. We also observed that the loss of soil carbon stocks was linked to the decreased soil carbon content and increased soil bulk density over the first 100 cm depth. We found no significant effect of LULCC on soil GHG effluxes. Regeneration efforts (i.e. restoration, rehabilitation and afforestation) led to biomass recovery after ~40 years. However, we found no clear patterns of mangrove soil carbon stock re‐establishment following biomass recovery. Our findings suggest that regeneration may help restore carbon stocks back to pre‐disturbed levels over decadal to century time scales only, with a faster rate for biomass recovery than for soil carbon stocks. Therefore, improved mangrove ecosystem management by preventing further LULCC and promoting rehabilitation is fundamental for effective climate change mitigation policy.     

农户生计与生态系统服务关系的区域差异及驱动机制——以密云水库上游流域为例

深入揭示生态系统与农户福祉之间的关系,对实现农户差异化管理及区域可持续发展具有重要意义。本研究以密云水库上游流域(包括北京市和河北省的部分区域)为研究区域,基于1754份农户调查问卷数据,通过统计计量方法对比分析了流域内北京市、河北省农户福祉水平(以家庭总收入表示)与生态系统服务依赖性(以生态系统依赖性指数表示)的关系。结果表明: 流域内京冀农户生计与生态系统的互作模式均可分为4类,但京冀两地不同模式占比差异较大。北京农户样本中,占比最高的是高福祉-低依赖模式(33.9%),农户人均年收入显著高于河北农户,农户的各项生计资本也较河北省农户高;河北农户中,不提倡的低福祉-高依赖模式仍占比39.1%,对提升农户福祉水平至关重要的人力资本素质、社会资本、金融资本等均显著低于北京农户;河北农户主要依赖农业生产收入(41.2%),对土地的开发利用程度显著较高;相对于北京农户,河北农户的自然资源条件、人力资本素质对农户生计的影响更加显著。保持适当家庭规模、不断提高劳动力教育水平、提高低收入家庭的生态补偿标准是形成农户与生态系统良好互动关系(高福祉-低依赖型)的关键因素。     

Conservation and human livelihoods at the crossroads: Local needs and knowledge in the management of Arabuko Sokoke Forest

Arabuko Sokoke Forest is the largest remaining single block of indigenous dry coastal tropical forest in Eastern Africa. Households within a 5 km buffer zone depend heavily on the forest for their livelihood needs, and the pressure on forest resources is on the increase. In May 2015, 109 households were interviewed on resources they obtain from the forest, in terms of the self‐reported level of monthly income. We found household income and farm size significantly positively correlated with benefits from the forest, highlighting the possible influence of household wealth in exploiting forest resources. A large proportion of households (32%) had limited knowledge of local birds, while human–bird conflict was reported by 44% of the households. While many households were keen to participate in conservation projects that maintain the forest, 44% had no knowledge of the forest management plan, and 60% of those interviewed had no idea of how forest zones were designated for particular activities. Drivers for local community participation in conservation projects appear to be sustainable income and fulfilment of basic household needs.     

A Carbon Footprint of High‐Speed Railways in China: A Case Study of the Beijing‐Shanghai Line

A carbon footprint (CF) assessment of Chinese high‐speed railways (HSRs) can help guide further development of the world's longest HSR network. In this research, a hybrid economic input‐output and life cycle assessment (EIO‐LCA) method was applied to estimate the CF of the Beijing‐Shanghai HSR line. Specific CFs were analyzed of different subsystems of the line, different stages of production, and three calculation scopes. Results showed that the annual CF of the Beijing‐Shanghai HSR is increasing, whereas the per‐passenger CF constantly declined between 2011 and 2014. Scope 1 emissions account for an average of 4% of the total annual CF, Scope 2 contribute 71%, and Scope 3 comprise 25%. Among the different stages, operation contributes the largest (71%), followed by construction (20%) and maintenance (9%). In the construction stage, the bridges have the largest CF, followed by trains, and then rails. A trade‐off exists between the increase in carbon emissions due to construction of bridges and the reduction in operation emissions affected by leveling changes in terrain. The Beijing‐Shanghai HSR line has a relatively higher per‐passenger CF than eight other HSR lines, which is largely due to China's coal‐based carbon‐intensive energy mix of electricity generation, high proportion of bridges, higher operating speed, and heavier train body. In the future, cleaner electricity supply options, more efficient raw material production, and improvement of trains are keys to reducing the CF of Chinese HSRs.     

2004—2013年东北三省主要粮食作物生产碳足迹

东北是我国重要的粮食主产区,在国家粮食安全保障中起着至关重要的作用.作物生产是主要的碳排放源,探明不同作物生产的碳足迹差异,对促进低碳农业发展具有重要意义.本研究利用2004—2013年东北三省主要粮食作物(水稻、玉米和大豆)的产量、播种面积、农田生产投入等统计数据,估算了该区粮食生产碳足迹.结果表明: 2004—2013年,东北地区3种主要粮食作物中,水稻生产单位面积碳足迹最高,平均达到(2463±56) kg CE·hm^-2,玉米次之.玉米的碳足迹上升趋势最明显,从2004年的1164 kg CE·hm^-2增加到2013年的1768 kg CE·hm^-2,增速为67 kg CE·hm^-2·a^-1.在碳足迹构成中,化肥贡献最大,分别占水稻、玉米、大豆总碳投入的45%、90%、83%.水稻生产中灌溉用电所占比例为29%~42%,远高于玉米和大豆.东北三省碳足迹差异显著,3种作物的单位产量碳足迹均在吉林省最高,单位面积碳足迹均在黑龙江省最低.随着农村劳动力非农化和作物生产机械化的快速递增,未来粮食生产中柴油等机械化碳投入将快速增长.提升化肥利用效率、灌溉效率和机械化作业效率将是发展东北地区低碳农业的关键途径.     

甘南高原不同生计方式农户的碳足迹分析

二氧化碳增加导致的全球气候变暖已成为当前人类社会面临的最严峻挑战,减少碳排放迫在眉睫。以地处青藏高原东缘的甘南高原为研究区,基于农户调查数据,采用生命周期评价法估算了甘南高原不同生计方式农户的生活直接能源消费碳足迹和间接能源消费碳足迹,并运用最小二乘法分析了影响农户碳足迹的关键因素。结果发现:(1)甘南高原农户年人均碳足迹达2.67 t CO2,其中,生活直接能源消费碳足迹比例达76.53%,间接能源消费碳足迹比例仅占23.47%;(2)随着非农化水平的提高,甘南高原农户的碳足迹依次下降,其中,纯农户人均碳足迹达4.32 t,兼业户与非农户分别为2.37 t和1.07 t;(3)随着农户家庭规模的增大、收入水平的提高、距县城距离的增加和消费水平的提高,农户碳足迹不断增加;随着劳动力受教育程度的提高、恩格尔系数的增加和非农化程度的提高,农户碳足迹不断减少。     

Spatial analysis of urban material stock with clustering algorithms: A Northern European case study

A large share of construction material stock (MS) accumulates in urban built environments. To attain a more sustainable use of resources, knowledge about the spatial distribution of urban MS is needed. In this article, an innovative spatial analysis approach to urban MS is proposed. Within this scope, MS indicators are defined at neighborhood level and clustered with k‐mean algorithms. The MS is estimated bottom‐up with (a) material‐intensity coefficients and (b) spatial data for three built environment components: buildings, road transportation, and pipes, using seven material categories. The city of Gothenburg, Sweden is used as a case study. Moreover, being the first case study in Northern Europe, the results are explored through various aspects (material composition, age distribution, material density), and, finally, contrasted on a per capita basis with other studies worldwide. The stock is estimated at circa 84 million metric tons. Buildings account for 73% of the stock, road transport 26%, and pipes 1%. Mineral‐binding materials take the largest share of the stock, followed by aggregates, brick, asphalt, steel, and wood. Per capita, the MS is estimated at 153 metric tons; 62 metric tons are residential, which, in an international context, is a medium estimate. Denser neighborhoods with a mix of nonresidential and residential buildings have a lower proportion of MS in roads and pipes than low‐density single‐family residential neighborhoods. Furthermore, single‐family residential neighborhoods cluster in mixed‐age classes and show the largest content of wood. Multifamily buildings cluster in three distinct age classes, and each represent a specific material composition of brick, mineral binding, and steel. Future work should focus on megacities and contrasting multiple urban areas and, methodologically, should concentrate on algorithms, MS indicators, and spatial divisions of urban stock.     

FoodPrints of households

Purpose

Food consumption is one of the main drivers of environmental impacts. To develop meaningful strategies for the reduction of impacts, food consumption patterns need to be understood on the household level, as purchasing decisions are taken on this level. The goals of this study were to develop a model that estimates food demand and environmental impact as a function of household characteristics, to assess variability between households, and to provide a basis for the development of consumer-targeted political interventions. We titled the study “FoodPrints of households,” as we assessed food consumption in terms of carbon footprint (in analogy to (Stoessel et al. Environ Sci Technol 46(6):3253–3262 2012)).

Methods

We used data from the Swiss household budget survey and applied multiple linear regressions based on generalized linear models to quantify food and beverage demand of individual households. Seven household characteristics, such as size, income, and educational level, served as input variables for the regressions. In a case study, food and beverage demand of 3238 individual households of a Swiss municipality was environmentally assessed with life cycle assessment, and scenarios for different reduction strategies were evaluated.

Results and discussion

We found that the carbon footprints of in-home food consumption per household member and year vary from 0.08 t CO₂ eq. to 5 t CO₂ eq. with a median value of 1 t CO₂ eq. This variability is significantly smaller than the carbon footprint variability for the consumption areas of housing and mobility, where 25 % of the people are responsible for 50 % of the environmental impacts. Differences between high- and low-impact households can be primarily explained by differences in meat and dairy consumption.

Conclusions

This paper presents a model for quantifying food demand and impacts on a household level in Switzerland and represents a basis for developing targeted political measures to mitigate food consumption impacts. Household budget data is also available for many other countries, and the methods presented in this paper could therefore also be applied to other geographical regions.

     

Labor Embodied in Trade

Global production chains carry environmental and socioeconomic impacts embodied in each traded good and service. Even though labor and energy productivities tend to be higher for domestic production in high‐income countries than those in emerging economies, this difference is significantly reduced for consumption, when including imported products to satisfy national demand. The analysis of socioeconomic and environmental aspects embodied in consumption can shed a light on the real level of productivity of an economy, as well as the effects of rising imports and offshoring. This research introduces a consumption‐based metric for productivity, in which we evaluate the loss of productivity of developed nations resulting from imports from less‐developed economies and offshoring of labor‐intensive production. We measure the labor, energy, and greenhouse gas emissions footprints in the European Union's trade with the rest of the world through a multiregional input‐output model. We confirm that the labor footprint of European imports is significantly higher than the one of exports, mainly from low‐skilled, labor‐intensive primary sectors. A high share of labor embodied in exports is commonly associated with low energy productivities in domestic industries. Hence, this reconfirms that the offshoring of production to cheaper and low‐skilled, labor‐abundant countries offsets, or even reverts, energy efficiency gains and climate‐change mitigation actions in developed countries.     

A method for calculating a land‐use change carbon footprint (LUC‐CFP) for agricultural commodities – applications to Brazilian beef and soy,Indonesian palm oil

The world's agricultural system has come under increasing scrutiny recently as an important driver of global climate change, creating a demand for indicators that estimate the climatic impacts of agricultural commodities. Such carbon footprints, however, have in most cases excluded emissions from land‐use change and the proposed methodologies for including this significant emissions source suffer from different shortcomings. Here, we propose a new methodology for calculating land‐use change carbon footprints for agricultural commodities and illustrate this methodology by applying it to three of the most prominent agricultural commodities driving tropical deforestation: Brazilian beef and soybeans, and Indonesian palm oil. We estimate land‐use change carbon footprints in 2010 to be 66 tCO₂/t meat (carcass weight) for Brazilian beef, 0.89 tCO₂/t for Brazilian soybeans, and 7.5 tCO₂/t for Indonesian palm oil, using a 10 year amortization period. The main advantage of the proposed methodology is its flexibility: it can be applied in a tiered approach, using detailed data where it is available while still allowing for estimation of footprints for a broad set of countries and agricultural commodities; it can be applied at different scales, estimating both national and subnational footprints; it can be adopted to account both for direct (proximate) and indirect drivers of land‐use change. It is argued that with an increasing commercialization and globalization of the drivers of land‐use change, the proposed carbon footprint methodology could help leverage the power needed to alter environmentally destructive land‐use practices within the global agricultural system by providing a tool for assessing the environmental impacts of production, thereby informing consumers about the impacts of consumption and incentivizing producers to become more environmentally responsible.     

Household Transmission of Vibrio cholerae in Bangladesh

Background

Vibrio cholerae infections cluster in households. This study''s objective was to quantify the relative contribution of direct, within-household exposure (for example, via contamination of household food, water, or surfaces) to endemic cholera transmission. Quantifying the relative contribution of direct exposure is important for planning effective prevention and control measures.

Methodology/Principal Findings

Symptom histories and multiple blood and fecal specimens were prospectively collected from household members of hospital-ascertained cholera cases in Bangladesh from 2001–2006. We estimated the probabilities of cholera transmission through 1) direct exposure within the household and 2) contact with community-based sources of infection. The natural history of cholera infection and covariate effects on transmission were considered. Significant direct transmission (p-value<0.0001) occurred among 1414 members of 364 households. Fecal shedding of O1 El Tor Ogawa was associated with a 4.9% (95% confidence interval: 0.9%–22.8%) risk of infection among household contacts through direct exposure during an 11-day infectious period (mean length). The estimated 11-day risk of O1 El Tor Ogawa infection through exposure to community-based sources was 2.5% (0.8%–8.0%). The corresponding estimated risks for O1 El Tor Inaba and O139 infection were 3.7% (0.7%–16.6%) and 8.2% (2.1%–27.1%) through direct exposure, and 3.4% (1.7%–6.7%) and 2.0% (0.5%–7.3%) through community-based exposure. Children under 5 years-old were at elevated risk of infection. Limitations of the study may have led to an underestimation of the true risk of cholera infection. For instance, available covariate data may have incompletely characterized levels of pre-existing immunity to cholera infection. Transmission via direct exposure occurring outside of the household was not considered.

Conclusions

Direct exposure contributes substantially to endemic transmission of symptomatic cholera in an urban setting. We provide the first estimate of the transmissibility of endemic cholera within prospectively-followed members of households. The role of direct transmission must be considered when planning cholera control activities.     

Greenhouse Gas Emissions Quantification and Reduction Efforts in a Rural Municipality

The present article aims to determine the current carbon footprint (CF) of Zernez, a Swiss mountain village, and to identify reduction potentials of greenhouse gas (GHG) emissions. For this purpose, material and energy flows were assessed mainly based on detailed household surveys, interviews, and energy bills, but also by means of other information sources, for example, national statistics, traffic censuses, and literature values. To set up the GHG balance, special attention was paid to the consistent definition of system boundaries by adopting two fundamentally different perspectives: purely geographical accounting (PGA) and the consumption‐based footprint (CBF) method. Each of these two perspectives total approximately 10 tonnes of carbon dioxide equivalents per capita per year. The PGA revealed that 70% of the direct emissions in Zernez are caused by agricultural activities, whereas no consumption area dominated the consumption‐induced CF. For the identification of targeted measures, both perspectives were considered in a complementary manner. The building stock and its underlying energy supply system showed a GHG reduction potential of 80%. The building sector was thus detected as a reasonable first step for the municipality to adopt GHG mitigation strategies. In the case of Zernez, building‐stock‐related measures are predicted to decrease the current CF by 13% (CBF) and 17% (PGA), respectively.     

Biotransformation of carbon tetrachloride by various acetate‐ and nitrate‐limited denitrifying consortia

Fed‐batch experiments were performed to determine the carbon tetrachloride (CT)‐degrading ability of three denitrifying consortia cultured from sites not contaminated with CT. A mathematical model was used to quantify the rates of CT transformation by the consortia under both acetate‐limiting and nitrate‐limiting conditions. A rate constant for CT transformation on a cellular protein basis and the fraction of degraded CT transformed to chloroform (CF) were determined for each consortium by optimizing the model to fit the experimental data. The parameters for these experiments were statistically compared to those obtained for previous experiments with a denitrifying consortium cultured from an aquifer soil sample from the US Department of Energy Hanford site in southeastern Washington state. Results of F‐test analysis indicated the rate of CT transformation and the production of CF both were functions of the limiting nutrient. Under nitrate‐limited conditions, the rate constant for CT transformation for all four consortia was about 30 L/gmol/min and approximately 50% of the CT transformed was converted to CF. When acetate was the limiting nutrient, the rate constant for CT transformation was approximately 8 L/gmol/min and the CF yield decreased to about 25%. These results imply the ability to degrade CT may be inherent to some denitrifying organisms, regardless of previous exposure to CT. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 342–348, 1999.