Implications For Greenhouse Gas Emissions Research Articles

Environmental spaces for palsas and peat plateaus are disappearing at a circumpolar scale

Abstract. Anthropogenic climate change threatens northern permafrost environments. This compromises the existence of permafrost landforms, such as palsas and peat plateaus, which have been assessed to be critically endangered habitats. In this study, we integrated geospatial datasets and statistical methods to model the suitable environments for palsas and peat plateaus across the Northern Hemisphere permafrost region. The models were calibrated using data from years 1950–2000. The effects of climate change on the suitable environments for the landforms were assessed by using low-, moderate-, and high-emissions scenarios (Representative Concentration Pathway climate scenarios: RCP2.6, RCP4.5, and RCP8.5, respectively) for two periods (2041–2060 and 2061–2080). Hotspots for palsa and peat plateau environments occurred in northern Europe, western Siberia, and subarctic Canada. Climate change was predicted to cause an almost complete loss (decrease of 98.2 %) of suitable environmental spaces under the high-emissions scenario by 2061–2080, while under low- and moderate-emissions scenarios the predicted loss was 76.3 % and 89.3 % respectively. Our modeling results are in line with previously published thermokarst data pointing out areas of recent degradation of palsa and peat plateau environments. Our results provide new insights into the distribution of the permafrost landforms in less studied areas such as central and eastern Siberia. In addition, the predictions provide new understanding of the changing geoecological conditions of the circumpolar region with important implications for greenhouse gas emissions.

Sustainable meat consumption: global and regional greenhouse gas emission implications and counterfactual scenario analyses

Sustainable meat consumption: global and regional greenhouse gas emission implications and counterfactual scenario analyses

Techno-economic comparison of standalone solar PV and hybrid power systems for remote outdoor telecommunication sites in northern Ghana

Telecommunication services have continued to evolve to meet the ever-changing bandwidth demand requirements. The electricity grid network of Ghana is faced with challenges, including low voltages, a lack of quick fault response teams, and the proximity to specific locations. Using diesel generators to address the shortfall in grid supply is expensive and has implications for greenhouse gas emissions. This study evaluated the technical and economic benefits of using a standalone solar photovoltaic (PV) system, hybrid (Solar PV/diesel), conventional diesel generators (DG), and grid extension to power an off-grid outdoor telecommunication site. Power solutions configurations were simulated using hybrid optimization of multiple electric renewables (HOMER). The study found the optimum design to be a standalone solar PV/battery system with 56.3 kW solar PV array and Sixty (60) pieces of 12 V SAGM batteries of 135 Ah. The optimum design had a net present cost (NPC) of US$ 88,176.00 and a cost of energy (COE) of US$ 0.321/kWh. The COE and the NPC of the optimum system were approximately 50% less than the design with DG only, which could significantly impact service tariff and improve access to digital connectivity. The COE from the solar PV/battery system is not competitive with the grid power supply (COE = US$0.12). However, considering the electric distance limit or breakeven distance of 4.51km for grid extension, the solar PV/battery is preferred. Therefore, the stakeholders in providing power solutions to off-grid locations should consider solar PV technology.

Discursive and biophysical dimensions of land sparing policies in Laos: Implications for greenhouse gas emissions and food security

Land-use competition between forest conservation and agricultural food production poses major threats to climate change mitigation and food security. Land sparing policies aim at reconciling this conundrum by intensifying agriculture while conserving forests, but scientific debates prevail about their effectiveness. To contribute to this debate, we analyze the discursive dimension of land sparing efforts and their biophysical implications for Lao PDR. Applying an interdisciplinary mixed-methods approach, we examine how Lao land-use policies legitimize land sparing at the cost of shifting cultivation and how land use changed between 2000 and 2019. We quantify ecosystem carbon fluxes and agricultural emissions and investigate trends in agricultural production and food security. We find that policy documents use both socio-economic and environmental arguments to substantiate land sparing at the expense of shifting cultivation. In biophysical terms, the stabilization of shifting cultivation enhanced the recovery of some forest areas resulting in gross carbon sequestration while ecosystems in total remained a net source of emissions. Concomitant agricultural intensification improved dietary energy supply, reduced the prevalence of undernourishment, and increased agricultural exports. However, cropland expansion and the intensification of agriculture entailed greenhouse gas emissions of similar extent as the continuing shifting cultivation, and could not prevent the prevalence of moderate or severe food insecurity in the total population until today. We conclude that the narrow focus of land-use policies on land sparing falls short in effectively balancing societal needs and ecosystem functions.

Exergy analysis of the Mexican energy sector

This paper proposes a step-by-step, replicable methodology for analyzing the exergy characteristics of a country’s energy system. It introduces a set of indicators comparable to those commonly used to describe national energy systems: (1) exergy intensity (2) exergy destruction per capita, (3) exergy destruction per gross domestic product (GDP), (4) exergy efficiency, and (5) exergetic cost. The energy efficiency of the energy sector in Mexico was roughly 20% lower than energy efficiency, with substantially less improvement over the 15 years from 2013 to 2018. This difference arises from a strong dependency on fossil fuels and associated exergy destruction, which is not immediately apparent when taking only an energy perspective. The economic value of exergy destruction could represent 2.9 % of GDP in Mexico. A decreasing trend in the final exergy consumption is not necessarily reflected in lower exergy destruction. Those indicators provide information about the Jevons’ paradox. And it points to substantial room for efficiency improvements in the energy sector, with important implications for greenhouse gas emissions. Applying the exergy perspective will allow policymakers to understand better opportunities to unlock new efficiencies and improve the sustainability of Mexico’s energy system and those of other countries.

Life cycle energy and greenhouse gas emissions implications of polyamide 12 recycling from selective laser sintering for an injection‐molded automotive component

AbstractThe selective laser sintering (SLS) process generates waste polymer powders, which can be recycled as feedstock for producing injection‐molded components. Recycling this powder has implications on the life cycle modeling of the SLS product, as well as the subsequent injection‐molded component. This study investigates the life cycle primary energy demand (PED) and global warming potential (GWP) of an automotive fuel‐line clip produced with recycled polyamide 12 (PA12) from an SLS process in comparison to the conventional polyamide 66 (PA66) counterpart, based on real‐world industry data. In addition, the life cycle PED and GWP of an SLS part are examined, with and without recycling PA12 from the SLS process. The results indicate a strong dependence on the approach to evaluate the environmental burden of waste PA12 from the SLS process (cut‐off, mass‐based allocation, economic allocation, and substitution). Compared with the PA66 fuel‐line clip, the recycled PA12 (rPA12) clip reduces the life cycle GWP by up to 26% (cut‐off) or increases by up to 68% (mass‐based allocation). For the SLS part, recycling PA12 powder provides a 42% reduction to its life cycle GWP (mass‐based allocation). Finally, from an expanded two‐part system perspective, the recycling of PA12 from the SLS process provides an 8% reduction in life cycle GWP. Similar trends are shown for the life cycle PED profiles. This study demonstrates the importance of recycling additive manufacturing (AM) wastes within a broader cascading system to improve the environmental performance of AM and the circular economy across industrial systems.

The EU's farm‐to‐fork strategy: An assessment from the perspective of agricultural economics

AbstractThe EU Farm to Fork (F2F) strategy includes a number of policy objectives that have implications for agricultural production in the EU and beyond. This contribution discusses the possible implications from an economic perspective. We draw on economic assessments by other authors and discuss their wider implications by considering only partially quantified benefits and costs. Overall, the assessments indicate a decline in EU agricultural production in quantitative terms. The F2F strategy negatively affects aggregate consumer surplus and—depending on the assumption made—a net increase or decrease in producer surplus, thereby inducing an overall net welfare loss. Partially quantified benefits and costs include the environmental benefits and costs linked to the F2F strategy, such as implications for greenhouse gas emissions, biodiversity, or the landscape. Therefore, by launching the strategy, policy makers have implicitly concluded that the additional net benefits outweigh the losses in consumer surplus. The economic studies combined with studies on the impact of agricultural practices on biodiversity and the emission of greenhouse gases do not support this claim without further technological and institutional changes, such as supporting the application of modern biotechnology by reducing regulatory hurdles. Also, whether most consumers will share this view remains to be seen. EU policy makers have it in their hands to implement the necessary institutional changes.

Historical and future global burned area with changing climate and human demography

Summary Wildfires influence terrestrial carbon cycling and represent a safety risk, and yet a process-based understanding of their frequency and spatial distributions remains elusive. We combine satellite-based observations with an enhanced dynamic global vegetation model to make regionally resolved global assessments of burned area (BA) responses to changing climate, derived from 34 Earth system models and human demographics for 1860–2100. Limited by climate and socioeconomics, recent BA has decreased, especially in central South America and mesic African savannas. However, future simulations predict increasing BA due to changing climate, rapid population density growth, and urbanization. BA increases are especially notable at high latitudes, due to accelerated warming, and over the tropics and subtropics, due to drying and human ignitions. Conversely, rapid urbanization also limits BA via enhanced fire suppression in the immediate vicinity of settlements, offsetting the potential for dramatic future increases, depending on warming extent. Our analysis provides further insight into regional and global BA trends, highlighting the importance of including human demographic change in models for wildfire under changing climate.

Interactive effects of temperature and redox on soil carbon and iron cycling

Shifts in temperature and rainfall regimes with climate change can feed back on redox dynamics and associated biogeochemical cycling in humid environments. This has global implications for greenhouse gas emissions and ecosystem carbon (C) storage and loss. Though aerobic carbon dioxide (CO2) production is generally understood to follow an Arrhenius-type temperature dependence, the temperature sensitivity of anaerobic metabolisms such as iron (Fe) reduction and methane (CH4) fluxes, both processes affecting C cycling in soils, remains unclear in upland soils. We used a fully factorial incubation experiment to examine the interactive effects of temperature (8, 26, and 35 °C) and redox (oxic and anoxic) conditions on CO2 production, CH4 fluxes, Fe reduction, microbial biomass C, and the microbial metabolic quotient (MMQ) in upland soils from two contrasting climate regimes and redox environments: a tropical forest in Puerto Rico (PR) and a temperate peatland in California (CA). Under oxic conditions, we found that CO2 production increased across both temperature gradients (8–26 °C and 26–35 °C). In contrast, under anoxic conditions, net CH4 fluxes and Fe reduction exhibited a greater temperature sensitivity between 26 and 35 °C than 8–26 °C in both PR and CA soils. We also observed coupling between Fe reduction and net CH4 fluxes in PR and CA soils consistent with competition for acetate. The anoxic MMQ increased in PR soils at high temperature, but not in CA soils, suggesting that the native PR environment may favor the development of more efficient microbial communities better able to tolerate warmer, wetter conditions. Together, our results suggest that anaerobic microbial metabolisms may be much more sensitive to higher temperature than aerobic ones, possibly due to proportionally greater anaerobic microbial activity at high temperature. Our results suggest that increased global temperatures combined with higher rainfall regimes may significantly increase anaerobic greenhouse gas production in humid environments.

Co-development of East African regional water scenarios for 2050

Summary The development of and access to freshwater resources in East Africa is fundamental to the region's sustainable development goals. Following vision documents for regional development and working with local stakeholders, we developed water scenarios up to 2050 that inform the hydro-economic modeling analysis of the extended Lake Victoria Basin, the headwaters of the Nile River. Water scenarios that take an integrated approach to assessing the combined effects of climate change, land use, and increasing human water use suggest that the flow regime of the Nile may remain relatively stable. However, if this stability is to be achieved, while at the same time sufficient water is preserved for healthy freshwater ecosystems, a large fraction of water infrastructure must rely on advanced, often costly technologies and management. Interconnected analyses of both upstream and downstream water resources over time, guided by co-developed scenarios, are indispensable for planning sustainable water-development pathways.

Life cycle energy and greenhouse gas emissions implications of using carbon fiber reinforced polymers in automotive components: Front subframe case study

Vehicle lightweighting benefits consumers through fuel savings, manufacturers through a more fuel-efficient vehicle portfolio, and the environment through reduced fossil fuel use and lower emissions. Vehicle components can be lightweighted by replacing conventional materials with alternatives such as aluminum or composites. However, lightweight materials come with their own set of environmental and economic challenges. Often, manufacturing of lightweight materials requires more energy than for conventional materials such as steel. Understanding the net energy and environmental benefits of lightweighting requires life cycle assessment with a large enough system boundary to prevent shifting of impacts and to ensure a fair comparison between different material options. Life cycle assessments of carbon fiber composite parts are hampered by substantial uncertainties in the energy needed for their production and recycling and the vehicle fuel consumption benefits. The present study addresses these deficiencies using a detailed vehicle fuel consumption model and industrially relevant carbon fiber production data and component design. The front subframe case study considered illustrates the challenges associated with achieving life cycle energy and greenhouse gas savings using carbon fiber. The base case with no powertrain resizing, secondary weight savings, or recycled carbon fiber and with 160,000 miles vehicle lifetime has no energy or emission benefits. When powertrain resizing, secondary weight savings, carbon fiber recycling, and increased vehicle lifetime travel were considered, energy and greenhouse gas benefits were found.

Greenhouse gas emissions associated with food packaging for online food delivery services in Australia

The food service industry has seen the advent of online food delivery services (OFDS) due to the development of online retailing and a rise in mobile phone usage. OFDS are growing in popularity around the world and are increasing the use of take-away food packaging and the subsequent environmental implications from its production and disposal. While a large number of studies have considered packaging-related environmental effects, there has been limited focus on the effect of OFDS-related packaging demand on the environment, particularly in relation to greenhouse gas emissions. This study quantifies the packaging-related greenhouse gas emissions associated with OFDS orders. Data on food packaging for a range of the most popular cuisines delivered by OFDS in Australia were collected from restaurants. The assessment was performed using the Packaging Impact Quick Evaluation Tool, which showed that the packaging-related greenhouse gas emissions for a single order ranges from 0.15 to 0.29 kg CO2e, depending on packaging type. Of this, production of packaging raw materials contributes at least 50%. With the expansion of the OFDS sector, the annual greenhouse gas emissions associated with OFDS food packaging in Australia is predicted to grow by 132% by 2024. This preliminary examination of the greenhouse gas emissions implications of food packaging production and disposal associated with the Australian OFDS industry adds to the limited knowledge in this area and provides valuable insights into the greenhouse gas emissions implications of the emerging global OFDS industry.

Could Cryoturbic Diapirs Be Key for Understanding Ecological Feedbacks to Climate Change in High Arctic Polar Deserts?

AbstractHigh Arctic polar deserts cover 26% of the Arctic. Increasing temperatures are predicted to significantly alter polar desert freeze‐thaw and biogeochemical cycles, with important implications for greenhouse gas emissions. However, the mechanisms underlying these changing cycles are still highly uncertain. Cryoturbic, carbon‐rich Bhy horizons (diapirs) in frost boils are key nutrient sources for Salix arctica. We hypothesized that diapirism leads to organic carbon characteristics that alter microbial pathways, which then control root foraging and greenhouse gas production. During July and August 2013, we characterized soil properties and examined gross nitrogen transformation rates in frost boils both with and without diapirs in two High Arctic polar deserts (dolomite and granite) near Alexandra Fjord (78°51′N 75°54′W), Ellesmere Island, Nunavut, Canada. Diapiric frost boils had 18% higher soil organic carbon in the dolomitic and 9% higher in the granitic deserts, and 29% higher total dissolved nitrogen in the dolomitic desert. However, diapirs decreased gross nitrogen mineralization rates by 30% in the dolomitic and by 48% in the granitic deserts. Attenuated total reflectance Fourier transformed mid‐infrared spectroscopy revealed greater concentrations of polysaccharides and recalcitrant carbon in diapiric versus nondiapiric frost boils. These increased polysaccharide concentrations likely facilitate diapirism as soil viscosity increases with polysaccharides. Lower microbial activity or ectomycorrhizae that are known to colonize S. arctica may accumulate total dissolved nitrogen in diapirs. Our results suggest geomorphologic‐plant‐microbe interactions may underlie important patterns of geochemical cycling in arctic systems. Thus, polar desert frost boils should represent a key focus of future investigations of climate change in arctic systems.

Forest Carbon Resilience of Eastern Spruce Budworm (Choristoneura fumiferana) Salvage Harvesting in the Northeastern United States

The next major eastern spruce budworm (Choristoneura fumiferana) outbreak is likely to begin impacting the forests of the northeastern US over the next few years. More than 4.7 million ha of forest and 94.8 million Mg of carbon in spruce (Picea spp.) and balsam fir (Abies balsamea) are at risk. Vegetation shifts in at-risk forest stands are likely to occur as a direct result of mortality caused by spruce budworm and through post-outbreak salvage harvest operations designed to minimize economic impact. Management interventions have short-term and long-term consequences for the terrestrial carbon budget and have significant implications for the role of the region’s forests as a natural climate solution. We used regional forest inventory data and 40-year growth and harvest simulations from the USDA Forest Service Forest Vegetation Simulator to quantify a range of forest carbon outcomes for alternative silvicultural interventions in the northeastern US. We performed a life cycle assessment of harvested wood products, including bioenergy, to evaluate the full greenhouse gas (GHG) emissions consequences of salvage and business as usual silvicultural scenarios across a range of stand risk profiles in the presence and absence of spruce budworm attack. Salvaging dead trees in the most at-risk stands tends to produce net emissions of carbon dioxide for at least ten years compared to a baseline where dead trees are left standing. In most scenarios, GHG emissions reached parity with the baseline by year 20. Changes in forest carbon stocks were the biggest driver of net emission differences between salvage and no salvage scenarios. A benchmark scenario without timber harvesting or the occurrence of a spruce budworm outbreak had the greatest net carbon sequestration profile after 40 years compared to all other scenarios. Salvaging trees killed by a severe and widespread insect infestation has potential negative short-term implications for GHG emissions, but long-term resilience of these climate benefits is possible in the absence of future outbreaks or subsequent harvest activities. The results provide guidance on silvicultural interventions to minimize the impact of spruce budworm on forest carbon.

How to increase sustainability in the Finnish wine supply chain? Insights from a country of origin based greenhouse gas emissions analysis

As wine supply chains become increasingly globalized, sustainability issues take on ever greater importance. This is the first study to analyse the environmental sustainability aspect of greenhouse gas (GHG) emissions from a global wine supply chain perspective, covering just over 90% of Finland's wine imports. Lacking substantial domestic production capacity, virtually all wine consumed in Finland is imported. Finland is comparable to its Nordic neighbours, Sweden and Norway, in this respect.The Life Cycle Assessment (LCA) methodology was combined with sensitivity and scenario analyses to investigate GHG emissions implications from prospective policy changes. Our results spotlight differences related to wine production in the eight main wine producing countries for the Finnish market (Australia, Chile, France, Germany, Italy, Spain, South Africa, and the United States), related logistics, and all packaging types for wine used in Finland (glass bottle, Bag-in-Box, PET bottle, beverage carton, and pouch). We found an average value of 1.23 kg CO2e for 0.75 L wine consumed in Finland, ranging from 0.59 kg CO2e for French wine in a bag-in-box packaging to 1.92 kg CO2e for Australian wine in a glass bottle. After identifying the main GHG emission hotspots in the wine supply chain, our scenario analyses highlight the effects of reducing glass bottle weight, moving away from glass packaging toward bag-in-box, increasing bulk wine export volumes to Finland, and following the European Commission's Energy 2020 strategy which targets increasing energy efficiency by 20 percent.

Greenhouse Gas Implications of Peri-Urban Land Use Change in a Developed City under Four Future Climate Scenarios

Present decisions about urbanization of peri-urban (PU) areas may contribute to the capacity of cities to mitigate future climate change. Comprehensive mitigative responses to PU development should require integration of urban form and food production to realise potential trade-offs. Despite this, few studies examine greenhouse gas (GHG) implications of future urban development combined with impacts on PU food production. In this paper, four future scenarios, at 2050 and 2100 time horizons, were developed to evaluate the potential GHG emissions implications of feeding and housing a growing urban population in Sydney, Australia. The scenarios were thematically downscaled from the four relative concentration pathways. Central to the scenarios were differences in population, technology, energy, housing form, transportation, temperature, food production and land use change (LUC). A life cycle assessment approach was used within the scenarios to evaluate differences in GHG impacts. Differences in GHG emissions between scenarios at the 2100 time horizon, per area of PU land transformed, approximated 0.7 Mt CO2-e per year. Per additional resident this equated to 0.7 to 6.1 t CO2-e per year. Indirect LUC has the potential to be significant. Interventions such as carbon capture and storage technology, renewables and urban form markedly reduced emissions. However, incorporating cross-sectoral energy saving measures within urban planning at the regional scale requires a paradigmatic shift.

The Shared Socioeconomic Pathways and their energy, land use, and greenhouse gas emissions implications: An overview

Abstract This paper presents the overview of the Shared Socioeconomic Pathways (SSPs) and their energy, land use, and emissions implications. The SSPs are part of a new scenario framework, established by the climate change research community in order to facilitate the integrated analysis of future climate impacts, vulnerabilities, adaptation, and mitigation. The pathways were developed over the last years as a joint community effort and describe plausible major global developments that together would lead in the future to different challenges for mitigation and adaptation to climate change. The SSPs are based on five narratives describing alternative socio-economic developments, including sustainable development, regional rivalry, inequality, fossil-fueled development, and middle-of-the-road development. The long-term demographic and economic projections of the SSPs depict a wide uncertainty range consistent with the scenario literature. A multi-model approach was used for the elaboration of the energy, land-use and the emissions trajectories of SSP-based scenarios. The baseline scenarios lead to global energy consumption of 400–1200 EJ in 2100, and feature vastly different land-use dynamics, ranging from a possible reduction in cropland area up to a massive expansion by more than 700 million hectares by 2100. The associated annual CO 2 emissions of the baseline scenarios range from about 25 GtCO 2 to more than 120 GtCO 2 per year by 2100. With respect to mitigation, we find that associated costs strongly depend on three factors: (1) the policy assumptions, (2) the socio-economic narrative, and (3) the stringency of the target. The carbon price for reaching the target of 2.6 W/m 2 that is consistent with a temperature change limit of 2 °C, differs in our analysis thus by about a factor of three across the SSP marker scenarios. Moreover, many models could not reach this target from the SSPs with high mitigation challenges. While the SSPs were designed to represent different mitigation and adaptation challenges, the resulting narratives and quantifications span a wide range of different futures broadly representative of the current literature. This allows their subsequent use and development in new assessments and research projects. Critical next steps for the community scenario process will, among others, involve regional and sectoral extensions, further elaboration of the adaptation and impacts dimension, as well as employing the SSP scenarios with the new generation of earth system models as part of the 6th climate model intercomparison project (CMIP6).

Comparison of integration options for gasification-based biofuel production systems – Economic and greenhouse gas emission implications

The impact of different integration options for gasification-based biofuel production systems producing synthetic natural gas, methanol and FT (Fischer-Tropsch) fuels on the NAP (net annual profit), FPC (fuel production cost) and the GHG (greenhouse gas) emission reduction potential are analysed. The considered integration options are heat deliveries to DH (district heating) systems or to nearby industries and integration with infrastructure for CO2 storage. The comparison is made to stand-alone configurations in which the excess heat is used for power production. The analysis considers future energy market scenarios and case studies in southwestern Sweden. The results show that integration with DH systems has small impacts on the NAP and the FPC and diverging (positive or negative) impacts on the GHG emissions. Integration with industries has positive effects on the economic and GHG performances in all scenarios. The FPCs are reduced by 7–8% in the methanol case and by 12–13% in the FT production case. The GHG emission reductions are strongly dependent on the reference power production. The storage of separated CO2 shows an increase in the GHG emission reduction potential of 70–100% for all systems, whereas the impacts on the economic performances are strongly dependent on the CO2e-charge.

Commuters’ behavior towards upgraded bus services in Greater Beirut: Implications for greenhouse gas emissions, social welfare and transport policy

Climate change is one of the most critical environmental challenges faced in the world today. The transportation sector alone contributes to 22% of carbon emissions, of which 80% are contributed by road transportation. In this paper we investigate the potential private car greenhouse gas (GHG) emissions reduction and social welfare gains resulting from upgrading the bus service in the Greater Beirut Area. To this end, a stated preference (SP) survey on mode switching from private car to bus was conducted in this area and analyzed by means of a mixed logit model. We then used the model outputs to simulate aggregate switching behavior in the study area and the attendant welfare and environmental gains and private car GHG emissions reductions under various alternative scenarios of bus service upgrade. We recommend a bundle of realistic bus service improvements in the short term that will result in a reasonable shift to buses and measurable reduction in private car emissions. We argue that such improvements will need to be comprehensive in scope and include both improvements in bus level of service attributes (access/egress time, headway, in-vehicle travel time, and number of transfers) and the provision of amenities, including air-conditioning and Wi-Fi. Moreover, such a service needs to be cheaply priced to achieve reasonably high levels of switching behavior. With a comprehensively overhauled bus service, one would expect that bus ridership would increase for commuting purposes at first, and once the habit for it is formed, for travel purposes other than commuting, hence dramatically broadening the scope of private car GHG emissions reduction. This said, this study demonstrates the limits of focused sectorial policies in targeting and reducing private car GHG emissions, and highlights the need for combining behavioral interventions with other measures, most notably technological innovations, in order for the contribution of this sector to GHG emissions mitigation to be sizable.

Economic and environmental analysis of five Chinese rural toilet technologies based on the economic input–output life cycle assessment

Building toilets are critical infrastructure to promote public health. The current sanitation technology in developed countries is based on diluting human excreta with large volumes of centrally provided potable water. This approach is a poor use of water resources and is also inefficient and energy intensive, which is not suitable for water-shortage rural areas of northern China. Therefore, comprehensive schemes of Chinese rural toilets, including standard flushing, rainwater harvesting flushing systems, urine separation and composting systems, were considered in this study by means of five scenarios simulation. Economic net present value method was adopted for economic analysis and economic input–output life cycle assessment model based on Chinese economic input–output table and life cycle database was developed for comparing energy consumption and greenhouse gas emission implications, aiming to guide the selection of toilet schemes. A mountainous village in Mentougou District of Beijing was taken as the example. Based on total cost and net present value method, the results showed that scenario 5, namely urine diverting composting systems, outweighed the other four alternatives on the cost even in the different discount rates ranging from 0% to 10%; scenario 3, namely urine-diversion and potable water flushing toilet, was sub-optimal economic solution which net present value was negative when discount rate was over 8%. This study also present scenario 3's environmental superiority to scenario 5 on energy consumption and greenhouse gas emission. These two technologies were proved viable options for standard flushing toilet. Nevertheless, for another two scenarios of rainwater harvesting flushing toilets, they had higher amounts of investment, energy consumption and greenhouse gas emission due to the high investment on rainwater tank construction. Moreover, the vast majority of construction materials required high energy consumption and were carbon intensive sectors in China. Finally, some suggestions were given for the implementation of urine separation toilets and composting toilets in the practical application. Meanwhile, impact of the rising water price in selecting alternative technologies and tradeoff about the priority consideration for rural toilet technologies were analyzed in this study. Considering the great significance of rainwater harvesting toilet technology to save the water resources, measures of how much government should subsidize for guarantee its extension and motivation was discussed as well.