Urban Greenhouse Gas Emissions Research Articles

Assessing urban methane emissions using column-observing portable Fourier transform infrared (FTIR) spectrometers and a novel Bayesian inversion framework

Abstract. Cities represent a large and concentrated portion of global greenhouse gas emissions, including methane. Quantifying methane emissions from urban areas is difficult, and inventories made using bottom-up accounting methods often differ greatly from top-down estimates generated from atmospheric observations. Emissions from leaks in natural gas infrastructure are difficult to predict and are therefore poorly constrained in bottom-up inventories. Natural gas infrastructure leaks and emissions from end uses can be spread throughout the city, and this diffuse source can represent a significant fraction of a city's total emissions. We investigated diffuse methane emissions of the city of Indianapolis, USA, during a field campaign in May 2016. A network of five portable solar-tracking Fourier transform infrared (FTIR) spectrometers was deployed throughout the city. These instruments measure the mole fraction of methane in a total column of air, giving them sensitivity to larger areas of the city than in situ sensors at the surface. We present an innovative inversion method to link these total column concentrations to surface fluxes. This method combines a Lagrangian transport model with a Bayesian inversion framework to estimate surface emissions and their uncertainties, together with determining the concentrations of methane in the air flowing into the city. Variations exceeding 10 ppb were observed in the inflowing air on a typical day, which is somewhat larger than the enhancements due to urban emissions (<5 ppb downwind of the city). We found diffuse methane emissions of 73(±22) mol s−1, which is about 50 % of the urban total and 68 % higher than estimated from bottom-up methods, although it is somewhat smaller than estimates from studies using tower and aircraft observations. The measurement and model techniques developed here address many of the challenges present when quantifying urban greenhouse gas emissions and will help in the design of future measurement schemes in other cities.

Circular Cities: What Are the Benefits of Circular Development?

If cities could become regenerative and adaptive urban ecosystems, in which resource loops were closed and waste was obsolete, their ecological footprint would diminish. In addition, urban resource security would increase, the health of urban populations would improve and urban greenhouse gas emissions would be reduced. These are the principle goals under-pinning the circular city. Circular cities emerge through the process of circular development. Circular development alters cities’ systems of provision to enable circular practices of inhabitants to develop. This manifests as circular food systems and construction, water and nutrient recycling; adaptive reuse of spaces and pop-up activities; bioremediation of contaminated sites and integration of blue-green infrastructure throughout cities. To transform our cities will require significant investment, political support and public engagement. If the benefits of adopting such an approach can be identified, this will begin to make the case for support. The research presented in this paper draws on an inductive and deductive content analysis of relevant literature and interviews with those implementing circular projects in European cities (London, Paris, Amsterdam and Stockholm). It provides a clear definition of the normative concept of circular development. It creates a framework of benefits which are likely to accrue from adopting this approach. It points to the synergistic benefits emerging from circular development. It also highlights problems around valuation of those benefits, the unintended consequences of circular development and the inequalities in accessing benefits across society.

Extending urban stocks and flows analysis to urban greenhouse gas emission accounting: A case of Odense, Denmark

AbstractCities generate greenhouse gas (GHG) emissions both in the construction phase of their built environment stocks and durable goods and in their operation phase with energy and material flows. Existing urban GHG accounting methods, however, focus largely on emissions related to energy and material flows and have rarely considered the role of urban stocks. In this article, we have extended urban stocks and flows analysis to urban GHG accounting, using bottom‐up and high‐resolution urban stocks and flows information for a case of Odense, Denmark. We introduced a complementary indicator of carbon replacement value (CRV) to account for emissions embodied in the urban stocks and determined the CRV of Odense as 10.7 megatons of CO2 equivalent (or 53 metric tons per capita) in 2017, equivalent to 13 years of Odense's operational emissions. The comparison between CRV and operational emissions across urban activities facilitates a better understanding of the carbon profile of the city and opportunities for decarbonization. Such urban metabolic based GHG accounting and inclusion of stocks can help to estimate the amount of GHG emissions to be expected from the further urbanization in developing countries as their urban stocks continue to increase and inform their potentials for leapfrogging in emission reduction.

MUCCnet: Munich Urban Carbon Column network

Abstract. In order to mitigate climate change, it is crucial to understand urban greenhouse gas (GHG) emissions precisely, as more than two-thirds of the anthropogenic GHG emissions worldwide originate from cities. Nowadays, urban emission estimates are mainly based on bottom-up calculation approaches with high uncertainties. A reliable and long-term top-down measurement approach could reduce the uncertainty of these emission inventories significantly. We present the Munich Urban Carbon Column network (MUCCnet), the world's first urban sensor network, which has been permanently measuring GHGs, based on the principle of differential column measurements (DCMs), since summer 2019. These column measurements and column concentration differences are relatively insensitive to vertical redistribution of tracer masses and surface fluxes upwind of the city, making them a favorable input for an inversion framework and, therefore, a well-suited candidate for the quantification of GHG emissions. However, setting up such a stationary sensor network requires an automated measurement principle. We developed our own fully automated enclosure systems for measuring column-averaged CO2, CH4 and CO concentrations with a solar-tracking Fourier transform spectrometer (EM27/SUN) in a fully automated and long-term manner. This also includes software that starts and stops the measurements autonomously and can be used independently from the enclosure system. Furthermore, we demonstrate the novel applications of such a sensor network by presenting the measurement results of our five sensor systems that are deployed in and around Munich. These results include the seasonal cycle of CO2 since 2015, as well as concentration gradients between sites upwind and downwind of the city. Thanks to the automation, we were also able to continue taking measurements during the COVID-19 lockdown in spring 2020. By correlating the CO2 column concentration gradients to the traffic amount, we demonstrate that our network is capable of detecting variations in urban emissions. The measurements from our unique sensor network will be combined with an inverse modeling framework that we are currently developing in order to monitor urban GHG emissions over years, identify unknown emission sources and assess how effective the current mitigation strategies are. In summary, our achievements in automating column measurements of GHGs will allow researchers all over the world to establish this approach for long-term greenhouse gas monitoring in urban areas.

Comparing urban greenhouse gas emission inventories in Brazilian cities

The urban greenhouse gas emission (GHG) inventory is an important tool for climate change mitigation. In Brazil, 15 years after the publication of the first municipal GHG inventory, few cities have measured their emissions. It depicts the timid advance in the country's urban climate agenda. In this paper, publicly available inventories were mapped, and then methodologies, emissions and reports were compared, with the aim to identify similarities, divergences and challenges to consolidate this instrument. The results show that the municipal inventories in Brazil are not easily comparable. In many cases, it lacks transparency there are different interpretations of the methodology and gaps of information. The definition of quality criteria and the dialogue among cities may help to refine the tool. Comparative perspective allows the exchange of knowledge between localities with similar profiles, such as Latin American cities. Sustaining discussion on municipal inventories is important for its improvement as a tool to support local interventions.

Comparing urban greenhouse gas emission inventories in Brazilian cities

Comparing urban greenhouse gas emission inventories in Brazilian cities

Evaluation of Bursa metropolitan greenhouse Gas inventory and reduction targets

This study summarizes the greenhouse gas (GHG) emission levels and Sustainable Energy Action Plan (SEAP) of Bursa, where is an industrial, touristic, and historic metropolitan city with a dense population in Turkey. This study summarized direct (scope 1), indirect (scope 2), and other indirect (scope 3) GHG emissions. Urban GHG emissions including scope 1, 2, and 3 activities were determined as 14,148,597 tCO2e for 2016. Industrial fuel consumption, transportation, and residential heating activities were the main sources. GHG emission control sectors were determined according to the last consecutive workshops in 2017. Control actions, such as Energy efficiency/renewable energy applications in residential and commercial buildings, increasing the share of public transport in transportation, and reducing the number of private vehicles in traffic, were planned. Future projections for 2030 were estimated with and without reduction activities. Sectors (industry, agriculture, and animal husbandry) which are not within the jurisdiction of local governments or which cannot be intervened by local governments were excluded. It showed that with the mitigation measures to be implemented. Public transport problems, renewable energy conversion, and reduction of the green texture of the city are the main obstacles.

Empirical study on carbon emission measurement and influencing factors of urban traffic based on “Population-Economy-Environment”

Economic growth, urban expansion, traffic dependence, and urban lifestyle have caused a large amount of energy consumption and greenhouse gas emissions in cities. The issue of urban greenhouse gas emissions has become a global focus and a research hotspot. This paper analysed the causality of driving factors and identified the key elements such as urban population, economy, energy and motor vehicles through system dynamics (SD) and econometric model. Then, it conducted empirical analysis and explored the impact of factors on urban transportation carbon emissions taking Beijing as an example. The research results showed that in addition to energy consumption, other factors were positively correlated with traffic carbon emissions. It believed that in order to control urban traffic carbon emissions, we must control the urban population, economy and the number of vehicles rationally. With the optimization of energy structure, the structural adjustment of traffic energy consumption is conducive to energy conservation and emission reduction in the transportation industry, and the decoupling of the total energy consumption of traffic and the carbon emissions from transportation.

Co-benefits of reducing CO2 and air pollutant emissions in the urban transport sector: A case of Guangzhou

The transport sector has become an important source of urban greenhouse gas (GHG) and air pollutant emissions, with the continuous growth of transportation demand. The co-benefits of reducing GHG and air pollutant emissions in the transport sector are receiving more and more attention. Taking Guangzhou as the case study city, this study quantitatively analyzed the co-benefits of reducing CO2 and air pollutant emissions under the sustainable scenario in the transport sector by developing a quantitative analysis model based on the Long-range Energy Alternatives Planning (LEAP) framework. The co-benefits quantitative parameter and the co-benefits radar chart analysis method are used to identify and evaluate the generated co-benefits, and then the co-benefits generated by implementing the sustainable measures are discussed. The results show that adjusting transport modes and increasing the application of electricity are the two most effective measures for achieving the co-benefits of reducing CO2 and air pollutant emissions in the Guangzhou transport sector. Thus, these two measures are highly preferential for mitigating CO2 and air pollutant emissions. In addition, increasing the application of biofuel and hydrogen energy also has good co-benefits. However, increasing the application of Liquefied Natural Gas (LNG) has poor co-benefits. Promoting the utilization of LNG intercity buses, trucks, and cargo ships will lead to emission increases of CO and HC compared to the current policy scenario, and small emission reductions of CO2 and other air pollutants. Therefore, to promote the utilization of LNG vehicles and ships, it is necessary to cooperate with the use of air pollutant end removal devices and high-pressure direct injection (HPDI) gas engines.

Impacts of policy on urban energy metabolism at tackling climate change: The case of Lisbon

Urbanisation and the associated growing climate change burdens pose risks to urban and global climate resilience. Urban greenhouse gas emissions fluctuate over time in response to energy demand, which is influenced by government programmes, economic activity, and demographics. In this research, we investigate the influence of policy on urban energy demand and its consequences on mitigating climate change impacts. Using a case study of Lisbon, Portugal from 2008 to 2016, we illustrate a combined use of an urban energy metabolism assessment coupled with a logarithmic mean Divisia index to isolate the changes in energy-related carbon emissions associated with policy changes. We then link these energy flows to life cycle emissions factors to build a multi-level assessment between local and non-local global warming potential. We find that in 2016 Lisbon’s energy flows generated more than 2 Mt of CO2-equivalent emissions over their life cycles, 48% of which were direct emissions within the city. This corresponds to a decrease of around 37% in greenhouse gas emissions from 2008. Additionally, we estimate the potential of Lisbon’s urban forests to sequester these emissions to understand the potential for climate change mitigation. Results show that Lisbon’s urban forest can meet less than 1% of the emissions throughout the assessment period. We discuss the changes, concluding that urban forests are insufficient in size to meet the sequestration demands of the urban energy metabolism, and therefore the focus must be more attuned to reducing fossil fuel use in the urban trade and transport activities.

The net greenhouse gas impact of the Jubilee line extension in London, UK

As cities work to reduce their total greenhouse gas (GHG) emissions, the transportation sector is lagging, accounting for a growing percentage of total emissions in many cities. The provision of public transit, and specifically urban rail transit, is widely seen as a useful tool for reducing urban transportation GHG emissions. More research, however, is needed to understand the net impact of new metro rail infrastructure on urban emissions and guide efforts to maximise the GHG savings through rail investments. This paper examines the net GHG emissions of the Jubilee line extension (JLE) in London, UK. The GHG emissions associated with construction, operation, ridership and changes in urban density associated with the provision of the new metro rail infrastructure are assessed. These components are then combined and compared to calculate the net GHG impact across the study period, which extends from opening in 1999 through 2011. The capital GHG emissions from construction of the JLE are calculated as 530 kilotonnes carbon dioxide equivalent (CO2e). The initial mode shift from other rail lines and long-term mode change from automobiles result in yearly GHG savings from riders on the JLE. A quasi-experimental analysis of land-use change near the JLE finds no calculable GHG saving from increased residential density. The GHG payback period is calculated between 13 and 19 years.

The GHG emission determinants research for waste disposal process at city-scale in Baoding

Current research on greenhouse gas(GHG) inventories supports the view that waste disposal is an important source of urban GHG emissions. Studying the driving factors behind the changes in greenhouse gas emissions from municipal waste treatment can provide better information support for emission reduction. This paper systematically evaluates the city-scale GHG emission determinants in waste disposal process using a system dynamics model. Subsequently, an empirical analysis was conducted on Baoding City. This research brings some interesting results: (1) The impact of the population is paramount. The emission reduction effect of controlling the size of the city and improving the quality of the population is remarkable. (2) Policy is another key factor. Comprehensive and appropriate policies are more effective than introducing and applying advanced technologies. Including urban land management, waste separation and metering and charging can be used for it. (3) It is necessary to formulate appropriate emission reduction policies for different industrial sectors by focusing on GHG generated from solid waste. Because the combined effect of factors is not equal to the simple sum of each factor. Policy implications in terms of our study results are discussed.

Urban greenhouse gas emissions from the Berlin area: A case study using airborne CO2 and CH4 in situ observations in summer 2018

Urban areas are recognised as a significant source of greenhouse gas emissions (GHG), such as carbon dioxide (CO2) and methane (CH4). The total amount of urban GHG emissions, especially for CH4, however, is not well quantified. Here we report on airborne in situ measurements using a Picarro G1301-m analyser aboard the DLR Cessna Grand Caravan to study GHG emissions downwind of the German capital Berlin. In total, five aircraft-based mass balance experiments were conducted in July 2018 within the Urban Climate Under Change [UC]2 project. The detection and isolation of the Berlin plume was often challenging because of comparatively small GHG signals above variable atmospheric background concentrations. However, on July 20th enhancements of up to 4 ppm CO2 and 21 ppb CH4 were observed over a horizontal extent of roughly 45 to 65 km downwind of Berlin. These enhanced mixing ratios are clearly distinguishable from the background and can partly be assigned to city emissions. The estimated CO2 emission flux of 1.39 ± 0.76 t s–1 is in agreement with current inventories, while the CH4 emission flux of 5.20 ± 1.70 kg s–1 is almost two times larger than the highest reported value in the inventories. We localized the source area with HYSPLIT trajectory calculations and the global/regional nested chemistry climate model MECO(n) (down to ~1 km), and investigated the contribution from sewage-treatment plants and waste deposition to CH4, which are treated differently by the emission inventories. Our work highlights the importance of strong CH4 sources in the vicinity of Berlin and shows, that there is limited understanding of CH4 emissions from urban regions, even for major cities in highly developed countries like Germany. Furthermore, we show that a detailed knowledge of GHG inflow mixing ratios is necessary to suitably estimate emission rates for Berlin.

Моделирование объёмов выбросов парниковых газов в городах с использованием данных различной детальности

A comparative analysis of the original methods of modeling urban greenhouse gas emissions caused by communal and transport sectors was carried out. These methods provide information at the level of urban-planning areas limited by the elements of the transport network and characterized by relatively similar buildings. These methods make possible to calculate greenhouse gas emissions from sources of the public sector, such as electricity and heat generation, gas burning for domestic needs. Calculation of emissions from sources of the transport sector includes differentiation by individual street segments. The described methods correspond to different accuracy levels including: the transition from aggregated values to the amount of emissions of individual areas of the city (downscaling); calculations using energy standards; calculations using actual energy consumption data. The considered methods have been tested on the example of the city of Nur-Sultan, that is one of the largest in the Republic of Kazakhstan. The calculation results are close to the actual values of Nur-Sultan's emission. The advantages and disadvantages of the considered methods are described. The factors leading to inaccurate results are considered. It was confirmed that the considered methods can be used for planning climate policy measures, since they allow to identify areas of the city and fields of activity that make the maximum contribution to the formation of greenhouse gas emissions. The considered methods are significant of for the cities of the former Soviet Union, which are characterized by the absence of developed systems for monitoring greenhouse gas emissions, is described, and it becomes necessary to calculate greenhouse gas emissions using indirect sources.

Understanding interactions between urban development policies and GHG emissions: A case study in Stockholm\xa0Region

Human-induced urban growth and sprawl have implications for greenhouse gas (GHG) emissions that may not be included in conventional GHG accounting methods. Improved understanding of this issue requires use of interactive, spatial-explicit social–ecological systems modeling. This paper develops a comprehensive approach to modeling GHG emissions from urban developments, considering Stockholm County, Sweden as a case study. GHG projections to 2040 with a social–ecological system model yield overall greater emissions than simple extrapolations in official climate action planning. The most pronounced difference in emissions (39% higher) from energy use single-residence buildings resulting from urban sprawl. And this difference is not accounted for in the simple extrapolations. Scenario results indicate that a zoning policy, restricting urban development in certain areas, can mitigate 72% of the total emission effects of the model-projected urban sprawl. The study outcomes include a decision support interface for communicating results and policy implications with policymakers.

Mining urban sustainable performance: Millions of GPS data reveal high-emission travel attraction in Tokyo

Abstract Sustainable performance assessment has received extensive attention in the fields of transportation, energy management, and urban planning. Given that transportation has become a leading component of urban greenhouse gas emissions, combining sustainable performance assessment with transportation emissions is crucial to urban sustainability. In this study, pointed at the unbalance between urban development and transportation accessibility among urban central activities zones, a metric named potential traffic attraction is proposed based on improved gravitational model to measure urban sustainable performance. Meanwhile, the correlation between the traffic attraction and the high-emission traffic is generated via GPS trajectories, which could ensure the credibility of high-emission travel mode for the correlation model. Based on the obtained urban sustainable performance, the status of the central activities zones development in Tokyo(Japan) was analyzed, finally, several corresponding strategies in different sustainable development status were proposed. Our study demonstrated that the integration of both urban development and transportation owns tremendous capabilities for reducing vehicle emissions, and it could provide specific guidelines for urban planning and transportation policies on urban sustainable development.

XCO<sub>2</sub> in an emission hot-spot region: the COCCON Paris campaign 2015

Abstract. Providing timely information on urban greenhouse gas (GHG) emissions and their trends to stakeholders relies on reliable measurements of atmospheric concentrations and the understanding of how local emissions and atmospheric transport influence these observations. Portable Fourier transform infrared (FTIR) spectrometers were deployed at five stations in the Paris metropolitan area to provide column-averaged concentrations of CO2 (XCO2) during a field campaign in spring of 2015, as part of the Collaborative Carbon Column Observing Network (COCCON). Here, we describe and analyze the variations of XCO2 observed at different sites and how they changed over time. We find that observations upwind and downwind of the city centre differ significantly in their XCO2 concentrations, while the overall variability of the daily cycle is similar, i.e. increasing during night-time with a strong decrease (typically 2–3 ppm) during the afternoon. An atmospheric transport model framework (CHIMERE-CAMS) was used to simulate XCO2 and predict the same behaviour seen in the observations, which supports key findings, e.g. that even in a densely populated region like Paris (over 12 million people), biospheric uptake of CO2 can be of major influence on daily XCO2 variations. Despite a general offset between modelled and observed XCO2, the model correctly predicts the impact of the meteorological parameters (e.g. wind direction and speed) on the concentration gradients between different stations. When analyzing local gradients of XCO2 for upwind and downwind station pairs, those local gradients are found to be less sensitive to changes in XCO2 boundary conditions and biogenic fluxes within the domain and we find the model–data agreement further improves. Our modelling framework indicates that the local XCO2 gradient between the stations is dominated by the fossil fuel CO2 signal of the Paris metropolitan area. This further highlights the potential usefulness of XCO2 observations to help optimize future urban GHG emission estimates.

Framework for Assessing Public Transportation Sustainability in Planning and Policy-Making

Transportation plays a key role in urban sustainability planning and urban greenhouse gas emission reductions. Globally, cities have established sustainability agendas and policies to guide the shift from traditional private automobile dependent transportation systems towards an increased use of public transportation, cycling, and walking. While the surrounding physical urban form and governance structures condition public transportation services, there are also many other factors to consider when discussing sustainability. As such, comprehensive planning and policy-oriented assessment frameworks that are independent of local conditions are still largely missing in literature. This paper presents a Public Transportation Sustainability Indicator List (PTSIL) that provides a platform for an integrated assessment of environmental, economic, and social dimensions of sustainability through an indicator-based approach. To demonstrate its use, the PTSIL is applied to analyze the policy documents of public transportation agencies in Helsinki, Finland, and Toronto, Canada. The results show that while both cities achieve relatively high scores in all dimensions, there is still high variability among individual indicators. The PTSIL presents a missed stepping stone between descriptive definitions of transportation sustainability and case specific sustainability performance assessments, offering an opportunity within the planning and policy-making sectors to review, assess, and develop public transportation services comprehensively.

Temporal Assessment of the Embodied Greenhouse Gas Emissions of a Toronto Streetcar Line

AbstractTransportation greenhouse gas (GHG) emissions often account for the largest share of urban GHG emissions. Consequently, large-scale reductions in urban GHG emissions will not be possible wi...

Lawn mowing frequency and its effects on biogenic and anthropogenic carbon dioxide emissions

Decision makers in urban areas actively pursue strategies to decrease carbon dioxide (CO2) emissions and other greenhouse gases. Lawns dominate urban lands in the U.S. and require intensive management, including frequent mowing, which may influence CO2 emissions from both biogenic and anthropogenic sources. We tested whether different lawn mowing frequencies (every one, two or three weeks) affected soil respiration (i.e., biogenic CO2 emissions), by changing soil moisture and temperature, and the gasoline emissions associated with lawn maintenance via lawn mowing (i.e., anthropogenic CO2 emissions). Sixteen yards in Springfield, Massachusetts USA were assigned a mowing frequency for two seasons (2013–2014). We measured grass height, air and soil temperature, soil moisture, soil CO2 flux, lawn mower emissions, tree canopy coverage and precipitation. We used a mixed effects modeling approach to test how these variables interacted with each other and responded to mowing frequency. Lawn-mowing frequency did not influence soil temperature, moisture, or biogenic soil CO2 fluxes. Soil microclimate and soil respiration varied more with ambient climatic fluctuations and tree canopy cover. By contrast, anthropogenic emissions increased with more frequent mowing due to emissions associated with the mower. When scaled to the entire mowing season, biogenic CO2 fluxes far exceeded the anthropogenic fluxes, thus requiring consideration for accurate accounting of urban greenhouse gas emissions. The interplay between biogenic (e.g., increasing tree canopy in lawn-dominated yards) and anthropogenic (i.e., mowing less frequently) methods of reducing CO2 emissions in cities highlights the need for more rigorous accounting processes for cities to meet climate action goals.