CO2 Emission Ratio Research Articles

Within-Field Spatial Variations in Subsoil Bulk Density Related to Crop Yield and CO2 and N2O Emissions

Subsoil compaction is an increasing problem in modern agriculture, but is not easily recognized in practice, also because of possible within-field spatial variations. This paper addresses the question of how within-field spatial variations in soil bulk density and other soil characteristics relate to within-field spatial variations in crop yield and CO2 and N2O emissions from soil. Four fields (5 to 20 ha each) were selected at the suggestion of crop farmers, and sampled using a random soil sampling design (100 samples per field). Undisturbed soil samples were taken at depth of 5-10, 30-35, and 50-55 cm and soil bulk density and CO2 and N2O emissions measured under controlled conditions. At each sampling point, also top soil (0-20 cm) samples were taken for determination of pH, texture, SOM, and (micro)nutrients, and soil penetration resistance measurements and visual assessments of soil structure were made. Wheat yields were recorded with harvesters equipped with GPS and yield recorders. Mean soil bulk density in the sub-soil (30-35 cm) ranged between fields from 1.36±0.08 to 1.60±0.11 g cm-3. Mean wheat yields ranged between fields and years from 7.6±0.6 and 11.3±2.4 Mg ha-1. Semi-variogram analyses showed that crop yields and soil properties were mostly spatially dependent; nugget-to-sill ratios were < 25% with ranges of 137 to 773 m. The ratio of CO2 emissions to N2O emissions was negatively related to soil bulk density, especially following N application.In conclusion, within-field spatial variations in subsoil bulk density were successfully related to spatial variations in crop yield and in CO2 and N2O emissions. The ratio of CO2 emissions to N2O emissions had a much greater response to spatial variations in soil bulk density than wheat yield. Our study suggests that N2O emission factors may depend on (sub)soil bulk density.

Conceptual design, environmental, and economic evaluation of direct copolymerization process of carbon dioxide and 1,4-butanediol

The routes to convert CO2 into environmentally benign materials have attracted wide attentions. In this work, an emerging process to produce poly(butylene carbonate) (or PBC) from direct copolymerization of carbon dioxide and 1,4-butanediol is firstly simulated with analyses on the CO2 emission ratio (CO2-e, in kg-CO2/kg-PBC) and yearly unit manufacturing cost of product (YUMC, in USD/kg). In order to address the issues associated with large amount of solvents used in the lab scale, two proposed scenarios including the reduction of solvent amount, and heat integration by vapor recompression cycle (VRC) were simulated. It is found that CO2-e is reduced by 82.0% (from 30.06 to 5.42) when the solvent amount is reduced to 10%, and another 19.9% reduction in CO2-e (to 4.34) when applying the VRC. YUMCs are reduced by ca. 68% for both proposed scenarios (from 5.62 to ca. 1.8). The findings reported in this study may prove informative for developing CO2 conversion technologies from lab scale to industrial scale.

Carbon Emissions in Recreation Fishing Travelling. Case of Latvia

Abstract The tourism industry holds high importance for the economy of Latvia; therefore, it is important to comply with the low-emission mobility strategy. The aim of this research is to investigate the CO2 emissions caused by a trip to Latvia’s Western coast at the Baltic Sea for recreational fishing in order to create information basis for intensifying the development of the specific tourism industry on a Baltic Sea states scope. In this research a hybrid (top-down and bottom up) and regression method was used for determination of CO2 emissions and interlinked relations. Research results: Altogether travelling forth and back to fishing destinations totalled 22 546 km, emitting 5.796 tCO2 emissions; vehicle occupation rates for vehicles vary – for car – 28.9 %, for motorhome – 50 %, for vans – 25 %. Renewal of car fleet to more fuel-economy vehicles would help comply with the CO2 95 g/km goal, would reduce the emissions by 684.49 kg, 847 kg and by 570.84 kg accordingly. The emission reduction per passenger with 60 % seat occupancy depend on the car CO2 emission ratio – 155 g/km, 147 g/km or 131 g/km, and would correspond to the cumulative effect of CO2 6.77 kg, 5.01 kg and 5.40 kg. Annual journey to fishing destinations per passenger, with 95 g/km emissions and 60 % vehicle occupancy rate with given registered CO2 emissions at 155 g/km, 147 g/km or 131 g/km: would produce CO2 297.7 kg, 322.7 kg and 280.2 kg accordingly. Use of seat-sharing of newer cars would allow for a reduction of emissions, specifically within Latvia’s Western coast of Baltic Sea recreation fishing area, where due to the scarce population, public transport is less available.

THE IMPACT OF FOREIGN DIRECT INVESTMENT ON CO2 EMISSIONS IN ASEAN COUNTRIES

The aim associated with the present study is to examine the sector-specific foreign direct investment and CO2 emissions. This study employs panel Granger causality tests to investigate the association between sector-specific foreign direct investment and CO2 emissions. Using a sample of 5 ASEAN countries for the period of 1980 to 2018, we find causality running from foreign direct investment in polluting intensive industries (“the dirty sector”) to CO2 emissions per capita. This result is robust to controlling for other factors associated with CO2emissions and using the ratio of CO2emissions to GDP. For other sectors, we find no robust evidence that FDI causes CO2 emissions. These findings are suitable for the regulation making authorities while developing the regulation related to the FDI and carbon emissions. This study provides the guidelines to the upcoming studies who wants to investigate this area in the future and suggested that upcoming studies should add other that FDI factor to investigate the carbon emissions. Keywords: Carbon Emissions, Foreign Direct Investment, Granger Causality tests, ASEAN CountriesJEL Classifications: E22, F21DOI: https://doi.org/10.32479/ijeep.10230

Compositional data analysis of smoke emissions from debris piles with low-density polyethylene

ABSTRACT Data describing the composition of smoke are inherently multivariate and always non-negative parts of a whole. The data are relative and the information is contained in the ratios between parts of the composition. A prior analysis of smoke emissions produced from the burning of manzanita wood mixed with low-density polyethylene plastic applied traditional statistical methods to the compositional data and found no effect. The current paper applies compositional data techniques to these smoke emissions to determine if the prior analysis was accurate. Analysis of variance of the isometric log-ratios showed that LDPE significantly affected the CO2 emission ratio for 8 of the 191 trace gases; this analysis showed none of the gases identified in the previous analysis were affected by LDPE. LDPE did not affect the CO2 emission ratios for the alkanes, alkenes, alkynes, aldehydes, cycloalkanes, cycloalkenes, diolefins, ketones, MAHs, and PAHs. Compositional data analysis should be used to analyze smoke emissions data. Burning contaminant-free LDPE should produce emissions like wood. Implications Reanalysis of impact of burning LDPE plastic in silvicultural debris piles using appropriate statistical techniques confirmed previously published results from inappropriate techniques that LDPE did not change the composition of the smoke emissions. Being able to dispose of these LDPE-covered forest debris by burning can save thousands of dollars in labor costs annually. Disposal of pesticide-free agricultural LDPE plastic by burning should only produce wood-like smoke emissions. This applies to LDPE/total mass ratios of 0.25– 2.5% as studied.

Эолово-аккумулятивный способ мелиорации засоленных почв Прикаспия

The aim of the work is to study the possibility of creating a cortical humus horizon from the surface of a salt marsh from siltysandy fractions of soil with seeds of wild plant species by arranging mechanical obstacles made of wooden material that protrudes 20 cm above the soil surface. The atmospheric processes under conditions of Kizlyar pastures. The research methodology included analyzes, counts and observations of humidity, the least moisture content (HB), enzymatic activity, chemistry and degree of salinity, the study of soil morphology, species composition of phytocenoses and accumulation of their mass on the transformed saline. For 8 years, created on the surface of a salt marsh, the cortical soil layer turns into the Wael eolian-accumulative humus horizon, 5 ± 0.8 cm thick. Solonchak cortical Ccc [AJk – AJ, s – VSA, s – Cca, s] is transformed into a solonchak restricted Scw [Wael – AJ, s – BCA, s – Cca, s]. The degree of soil salinity decreases from a very strong degree in a layer of 0–5 cm to a weak one, in a layer of 6–15 cm to a moderate degree. The yield of phytomass from the saltmaker of the regraded reaches 2.06 t/ha of air-dry mass, which contains 1.85 t/ha of carbon, which leads to an improvement in the ratio of effluents and CO2 emissions, a decrease in the greenhouse effect in nature and an increase in the utilization level of HEADLIGHTS, preventing excessive overheating of the soil and air masses of the atmosphere.

Simulating the effects of soil temperature and soil moisture on CO2 and CH4 emissions in rice straw-enriched paddy soil

Paddy soil from a site in northeast China was incubated with 13C-labeled rice straw in a laboratory study, and the effects of soil temperature and moisture on CO2 and CH4 emissions were measured using stable isotope ratio mass spectrometry. Aerobic incubation experiments were conducted at three soil temperatures (−10 °C, 0 °C, and 10 °C) and two soil moistures (60% and 100% water-filled pore space (WFPS)) in a laboratory for 24 weeks to simulate the rice-fallow season. An anaerobic incubation experiment was carried out for 16 weeks under a soil temperature of 25 °C and a 1 cm submerged layer to simulate the rice-growing season. Our results showed that increases in both soil temperature and soil moisture significantly promoted the cumulative CO2 emissions from rice straw during aerobic incubation. Furthermore, during anaerobic incubation, the cumulative emissions of CO2 and CH4 from rice straw decreased with increasing aerobic incubation soil temperature and soil moisture. The CO2 and CH4 emission ratios from rice straw throughout the incubation duration ranged from 6.6–15.7% and 0.0–3.0%, respectively. The addition of rice straw promoted a priming effect on native soil organic carbon (SOC) mineralization and produced CO2 emissions, which positively impacted priming during the aerobic (rice-fallow season) and anaerobic incubation (rice-growing season). The positive priming effect of rice straw on the CO2 emission duration ranged from 75.0% to 274.3% by the end of the 40-week incubation period. Furthermore, the aforementioned effect first increased and then decreased as the aerobic incubation soil temperature increased, with the greatest effect at 0 °C and lowest at 10 °C. These results suggest that high temperature during the rice-fallow season promotes the decomposition of rice straw C and leads to a decreased positive priming effect on native SOC during the rice-fallow and rice-growing seasons under the seasonal conditions of northeast China, and that it also leads to decreased CH4 production during the rice-growing season. These results have scientific significance for rational utilization of rice straw and mitigation of greenhouse effect in northeast China.

Production Globalization Makes China’s Exports Cleaner

Summary Production globalization, which is when firms expand their supply chains across national boundaries, creates an opportunity for developing countries to engage in international production networks via trade. Described as the world's factory, China specializes in assembly manufacturing mainly through processing exports. Firms use imported intermediate inputs for production and, after processing or assembly, re-export the finished products to international markets. Here, we show that the carbon efficiency of China’s processing exports is greater than that of its ordinary exports. If the impact of trade heterogeneity is ignored, then the domestic emissions embodied in China’s exports will be overestimated by 23.4%, and the foreign emissions embodied in China’s exports will be underestimated by 29.3%. If the degree of global value chain participation, which ranges from 0 to 1, increases by 0.1, although foreign emissions embodied in China’s exports would increase, the gross carbon intensity of China’s exports will decrease by 11.7%.

Land use conversion influences soil respiration across a desert-oasis ecoregion in Northwest China, with consideration of cold season CO2 efflux and its significance

Quantifying annual soil CO2 emissions and the effects of physical and geochemical factors on soil CO2 efflux will improve the carbon budget estimates, as well as enhance predictions of how soil CO2 emission will response to climate change in arid areas. To data, variability in soil respiration rates caused by land use conversion in the desert-oasis ecoregion of Northwest China remains poorly characterized, especially the contribution of cold season (November-February) CO2 emission. Soil respiration was measured in a Haloxylon ammodendron desert shrubland, a Zea mays cropland, a Populus gansuensis forest, and a Tamarix chinensis Lour wetland using a LI-COR 8100 Soil Respiration Observation System from April 2016 to March 2019. Annual soil CO2 emissions totaled 176, 778, 918, and 397 g C m−2 in the desert shrubland, cropland, forest, and wetland, respectively. The ratio of cold season CO2 emissions to the annual varied from 6 to 15% across ecosystems. Therefore, ignoring cold season CO2 emissions would lead to underestimates of carbon losses in the desert-oasis ecoregion. The soil respiration rate at 10 °C was influenced by soil organic carbon content in all four ecosystems. In the cropland and forest, soil respiration rate was affected by the interaction of soil moisture and soil temperature, while in the wetland and desert shrubland, soil respiration was sensitive to a single factor, soil temperature. Land use conversion induced differences in organic matter accumulation, soil temperature, and soil moisture, and as a consequence, produced variability in soil respiration rates across the desert-oasis ecoregion.

A methodology to constrain carbon dioxide emissions from coal-fired power plants using satellite observations of co-emitted nitrogen dioxide

Abstract. We present a method to infer CO2 emissions from individual power plants based on satellite observations of co-emitted nitrogen dioxide (NO2), which could serve as complementary verification of bottom-up inventories or be used to supplement these inventories. We demonstrate its utility on eight large and isolated US power plants, where accurate stack emission estimates of both gases are available for comparison. In the first step of our methodology, we infer nitrogen oxides (NOx) emissions from US power plants using Ozone Monitoring Instrument (OMI) NO2 tropospheric vertical column densities (VCDs) averaged over the ozone season (May–September) and a “top-down” approach that we previously developed. Second, we determine the relationship between NOx and CO2 emissions based on the direct stack emissions measurements reported by continuous emissions monitoring system (CEMS) programs, accounting for coal quality, boiler firing technology, NOx emission control device type, and any change in operating conditions. Third, we estimate CO2 emissions for power plants using the OMI-estimated NOx emissions and the CEMS NOx∕CO2 emission ratio. We find that the CO2 emissions estimated by our satellite-based method during 2005–2017 are in reasonable agreement with the US CEMS measurements, with a relative difference of 8 %±41 % (mean ± standard deviation). The broader implication of our methodology is that it has the potential to provide an additional constraint on CO2 emissions from power plants in regions of the world without reliable emissions accounting. We explore the feasibility by comparing the derived NOx∕CO2 emission ratios for the US with those from a bottom-up emission inventory for other countries and applying our methodology to a power plant in South Africa, where the satellite-based emission estimates show reasonable consistency with other independent estimates. Though our analysis is limited to a few power plants, we expect to be able to apply our method to more US (and world) power plants when multi-year data records become available from new OMI-like sensors with improved capabilities, such as the TROPOspheric Monitoring Instrument (TROPOMI), and upcoming geostationary satellites, such as the Tropospheric Emissions: Monitoring Pollution (TEMPO) instrument.

Detectability of CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; emission plumes of cities and power plants with the Copernicus Anthropogenic CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Monitoring (CO2M) mission

Abstract. High-resolution atmospheric transport simulations were used to investigate the potential for detecting carbon dioxide (CO2) plumes of the city of Berlin and neighboring power stations with the Copernicus Anthropogenic Carbon Dioxide Monitoring (CO2M) mission, which is a proposed constellation of CO2 satellites with imaging capabilities. The potential for detecting plumes was studied for satellite images of CO2 alone or in combination with images of nitrogen dioxide (NO2) and carbon monoxide (CO) to investigate the added value of measurements of other gases coemitted with CO2 that have better signal-to-noise ratios. The additional NO2 and CO images were either generated for instruments on the same CO2M satellites (2 km× 2 km resolution) or for the Sentinel-5 instrument (7.5 km× 7.5 km) assumed to fly 2 h earlier than CO2M. Realistic CO2, CO and NOX(=NO+NO2) fields were simulated at 1 km× 1 km horizontal resolution with the Consortium for Small-scale Modeling model extended with a module for the simulation of greenhouse gases (COSMO-GHG) for the year 2015, and they were used as input for an orbit simulator to generate synthetic observations of columns of CO2, CO and NO2 for constellations of up to six satellites. A simple plume detection algorithm was applied to detect coherent structures in the images of CO2, NO2 or CO against instrument noise and variability in background levels. Although six satellites with an assumed swath of 250 km were sufficient to overpass Berlin on a daily basis, only about 50 out of 365 plumes per year could be observed in conditions suitable for emission estimation due to frequent cloud cover. With the CO2 instrument only 6 and 16 of these 50 plumes could be detected assuming a high-noise (σVEG50=1.0 ppm) and low-noise (σVEG50=0.5 ppm) scenario, respectively, because the CO2 signals were often too weak. A CO instrument with specifications similar to the Sentinel-5 mission performed worse than the CO2 instrument, while the number of detectable plumes could be significantly increased to about 35 plumes with an NO2 instrument. CO2 and NO2 plumes were found to overlap to a large extent, although NOX had a limited lifetime (assumed to be 4 h) and although CO2 and NOX were emitted with different NOX:CO2 emission ratios by different source types with different temporal and vertical emission profiles. Using NO2 observations from the Sentinel-5 platform instead resulted in a significant spatial mismatch between NO2 and CO2 plumes due to the 2 h time difference between Sentinel-5 and CO2M. The plumes of the coal-fired power plant Jänschwalde were easier to detect with the CO2 instrument (about 40–45 plumes per year), but, again, an NO2 instrument could detect significantly more plumes (about 70). Auxiliary measurements of NO2 were thus found to greatly enhance the capability of detecting the location of CO2 plumes, which will be invaluable for the quantification of CO2 emissions from large point sources.

A feasibility study to evaluate the potential replication of an energy positive house in the UK

This paper presents an evaluation of the economic and technical feasibility of a renewable-led low carbon house in the UK. A holistic systems-based approach to achieve energy positive house has been taken. Long-term economic and technical feasibility analysis have been carried out based on a validated thermal and energy model of the house. The economic analysis employs the Return on Investment (ROI) method and considers changes to government financial support and technology progress over time. Results show that the extra investment on the house, compared with that for building a standard social house of similar size, can be paid back within the system lifespan under both the old Feed-in Tariff and its proposed replacement with reduced financial support. Variants examined in the technical feasibility analysis include housing type, orientation and location. Results show that the house can be replicated to achieve an energy positive performance for all variant combinations. Among the variants, location has the highest impact on building performance including annual electricity import, CO2 emission and electricity self-sufficient ratio, with South UK performing better than North UK. This implies that more efficient or advanced technologies would be needed to achieve similar building or system performance in areas of unfavourable climate. The outcome of the research has demonstrated the affordability of the energy positive house, and the technical feasibility of its replication with different housing types, orientations and locations in the UK. This study supports the wide scale replication of this affordable systems-based approach in domestic building design and construction when incorporating appropriate technologies.

An improved estimate for the &amp;lt;i&amp;gt;δ&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C and &amp;lt;i&amp;gt;δ&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O signatures of carbon monoxide produced from atmospheric oxidation of volatile organic compounds

Abstract. Atmospheric carbon monoxide (CO) is a key player in global atmospheric chemistry and a regulated pollutant in urban areas. Oxidation of volatile organic compounds (VOCs) is an important component of the global CO budget and has also been hypothesized to contribute substantially to the summertime urban CO budget. In principle, stable isotopic analysis of CO could constrain the magnitude of this source. However, the isotopic signature of VOC-produced CO has not been well quantified, especially for the oxygen isotopes. We performed measurements of CO stable isotopes on air samples from two sites around Indianapolis, US, over three summers to investigate the isotopic signature of VOC-produced CO. One of the sites is located upwind of the city, allowing us to quantitatively remove the background air signal and isolate the urban CO enhancements. as well as the isotopic signature of these enhancements. In addition, we use measurements of Δ14CO2 in combination with the CO:CO2 emission ratio from fossil fuels to constrain the fossil-fuel-derived CO and thereby isolate the VOC-derived component of the CO enhancement. Combining these measurements and analyses, we are able to determine the carbon and oxygen isotopic signatures of CO derived from VOC oxidation as -32.8‰±0.5‰ and 3.6 ‰±1.2 ‰, respectively. Additionally, we analyzed CO stable isotopes for 1 year at Beech Island, South Carolina, US, a site thought to have large VOC-derived contributions to the summertime CO budget. The Beech Island results are consistent with isotopic signatures of VOC-derived CO determined from the Indianapolis data. This study represents the first direct determination of the isotopic signatures of VOC-derived CO and will allow for improved use of isotopes in constraining the global and regional CO budgets.

Zero-energy penalty carbon capture and utilization for liquid fuel and power cogeneration with chemical looping combustion

Abstract The utilization of captured CO2 for fuel, chemicals and materials is currently a focus of significant research effort as a method that can simultaneously mitigate greenhouse gas effect while reduce fossil fuel depletion. In this work, CO2 source is provided by a desirable three-stage Fe-based chemical looping combustion power system that can achieve zero-energy-penalty CO2 capture while simultaneously obtain pure H2 source. The aim of this study is to present this designed process for the first time with demonstrating it as an energy-efficient and environmental-friendly CO2-to-liquid fuel pathway. Within this context, the liquid fuels energy output and carbon emissions are compared with different CO2 utilization ratios to the thermodynamic assessment, intending to disclose the insufficiency location within system. With conceivable improvements in an optimum condition, the fuel energy saving ratio and CO2 emission ratio of this process are projected to be 12.19% and 98.46%, respectively in relative to separate production system. The maximal exergy destruction, though projected to be located in chemical looping hydrogen generation unit (as represented by 37.56% of total exergy destruction), still has opportunities to reduce in some extent by elevating oxygen carries high-temperature resistance along with future research needs. Finally the sensitivity analysis is also projected to assess the strong influencing parameters that affect the system performance.

Carbon Footprint Analysis of Bamboo Scrimber Flooring—Implications for Carbon Sequestration of Bamboo Forests and Its Products

Bamboo forest is characterized by large carbon sequestration capability and it plays an important role in mitigating climate change and global carbon cycling. Previous studies have mostly focused on carbon cycling and carbon stocks in bamboo forest ecosystems, whereas the carbon footprints of bamboo products have not received attention. China is the largest exporting country of bamboo flooring in the world. Estimating the carbon footprint of bamboo flooring is of essential importance for the involved enterprises and consumers to evaluate their own carbon footprints. In this study, we investigated the production processes of bamboo scrimber flooring for outdoor use, a typical bamboo flooring in China. Based on business-to-business (B2B) evaluation method, we assessed CO2 emission and carbon transfer ratio in each step of the production process, including transporting bamboo culms and producing and packing the products. We found that to produce 1 m3 of bamboo scrimber flooring, direct carbon emissions from fossil fuels during transporting raw materials/semi-finished products, from power consumptions during production, and indirect emissions from applying additives were 30.94 kg CO2 eq, 143.37 kg CO2 eq, and 78.34 kg CO2 eq, respectively. After subtracting the 267.54 kg CO2 eq carbon stocks in the product from the 252.65 kg CO2 eq carbon emissions derived within the defined boundary, we found that the carbon footprint of 1 m3 bamboo scrimber flooring was −14.89 kg CO2 eq. Our results indicated that the bamboo scrimber flooring is a negative carbon-emission product. Finally, we discussed factors that influence the carbon footprint of the bamboo flooring and gave suggestions on carbon emission reduction during production processes. This study provided a scientific basis for estimating carbon stocks and carbon footprints of bamboo products and further expanded knowledge on carbon cycling and lifespan of carbon in the bamboo forest ecosystem.

Green computing: Optimize design of solar based power supply unit for IOT

Objectives: To design a solar based power supply unit that can replace normal power supply in Internet of Things (IoT) devices specifically computers without compromising the efficiency of the devices. It also helps to minimize the ratio of Co2 emission of digital devices which is a big threat now days for environment. Statistical Analysis: Basically, a circuit of DC power supply unit is design for desktop computers. These computers can work on 12 volts DC power supply in green computing environment. Moreover, 5 and 3 volts are generated for initial power and internal components of the computer. Moreover, the statistical analysis is carried out on the bases of energy consumption of the user in Pakistan. Findings: The solar power can save our energy cost up to 208 volts because normal power supply works on 220 volts and new designed power supply can work on 12 volts which are too less than 220. This research work provides a potential technique for green IoT environment. Application: the proposed DC power supply unit will be very helpful to run the IoT components directly on solar systems. Moreover, because of minimum power consumption of IoT it also reduces the carbon emissions that would be good for environment. Keywords: DC Power Supply Unit, Energy Consumption, Green Computing, Internet of Things (IoT), Solar Based Power Supply

An Estimate of Natural Gas Methane Emissions from California Homes.

We estimate postmeter methane (CH4) emissions from California's residential natural gas (NG) system using measurements and analysis from a sample of homes and appliances. Quiescent whole-house emissions (i.e., pipe leaks and pilot lights) were measured using a mass balance method in 75 California homes, while CH4 to CO2 emission ratios were measured for steady operation of individual combustion appliances and, separately, for transient operation of three tankless water heaters. Measured quiescent whole-house emissions are typically <1 g CH4/day, though they exhibit long-tailed gamma distributions containing values >10 g CH4/day. Most operating appliances yield undetectable CH4 to CO2 enhancements in steady operation (<0.01% of gas consumed), though storage water heaters and stovetops exhibit long-tailed gamma distributions containing high values (∼1-3% of gas consumed), and transients are observed for the tankless heaters. Extrapolating results to the state-level using Bayesian Markov chain Monte Carlo sampling combined with California housing statistics and gas use information suggests quiescent house leakage of 23.4 (13.7-45.6, at 95% confidence) Gg CH4, with pilot lights contributing ∼30%. Emissions from steady operation of appliances and their pilots are 13.3 (6.6-37.1) Gg CH4/yr, an order of magnitude larger than current inventory estimates, with transients likely increasing appliance emissions further. Together, emissions from residential NG are 35.7 (21.7-64.0) Gg CH4/yr, equivalent to ∼15% of California's NG CH4 emissions, suggesting leak repair, improvement of combustion appliances, and adoption of nonfossil energy heating sources can help California meet its 2050 climate goals.

Large methane emissions from natural gas vehicles in Chinese cities

In recent years, cities in developing countries have become more and more reliant on natural gas as a clean energy source for transportation to reduce air pollution. In this study, we used street-level measurement of atmospheric CH4 and CO2 concentrations to quantify CH4 emissions from natural gas vehicles (NGVs) in China. These measurements were made in eight cities (Chengdu, Urumqi, Jinan, Nanjing, Lanzhou, Harbin, Guangzhou) with varying sizes of NGV fleet. A traffic CH4:CO2 emission ratio (TER) was determined via linear regression of CH4 versus CO2 concentration data obtained from each street transect. The TER value was combined with the ratio of NGVs in the street traffic in a mathematical model to obtain the CH4 emission factor for NGVs. Results show that the TER increases with increasing NGV ratio and decreases with increasing traffic speed. Overall, the NGV CH4 emission factor in these cities is 0.022 ± 0.0033 kg m−3, about 8 times the Intergovernmental Panel on Climate Change (IPCC) default factor for NGVs and is more than 100% higher than the mean NGV tailpipe emission factor found in the published literature. That the overall emission factor is much larger than the tailpipe emission factor indicates that on-road vehicle gas leakage is a widespread problem. A business-as-usual scenario suggests that NGVs may emit 1.23 Tg CH4 yr−1 in 2030, or about 3% of China's current total anthropogenic emission. Our study suggest that curbing the emissions from this sector should be a high priority for global climate mitigation efforts.

Uncertainty in projected climate change arising from uncertain fossil-fuel emission factors

Emission inventories are widely used by the climate community, but their uncertainties are rarely accounted for. In this study, we evaluate the uncertainty in projected climate change induced by uncertainties in fossil-fuel emissions, accounting for non-CO2 species co-emitted with the combustion of fossil-fuels and their use in industrial processes. Using consistent historical reconstructions and three contrasted future projections of fossil-fuel extraction from Mohr et al we calculate CO2 emissions and their uncertainties stemming from estimates of fuel carbon content, net calorific value and oxidation fraction. Our historical reconstructions of fossil-fuel CO2 emissions are consistent with other inventories in terms of average and range. The uncertainties sum up to a ±15% relative uncertainty in cumulative CO2 emissions by 2300. Uncertainties in the emissions of non-CO2 species associated with the use of fossil fuels are estimated using co-emission ratios varying with time. Using these inputs, we use the compact Earth system model OSCAR v2.2 and a Monte Carlo setup, in order to attribute the uncertainty in projected global surface temperature change (∆T) to three sources of uncertainty, namely on the Earth system’s response, on fossil-fuel CO2 emission and on non-CO2 co-emissions. Under the three future fuel extraction scenarios, we simulate the median ∆T to be 1.9, 2.7 or 4.0 °C in 2300, with an associated 90% confidence interval of about 65%, 52% and 42%. We show that virtually all of the total uncertainty is attributable to the uncertainty in the future Earth system’s response to the anthropogenic perturbation. We conclude that the uncertainty in emission estimates can be neglected for global temperature projections in the face of the large uncertainty in the Earth system response to the forcing of emissions. We show that this result does not hold for all variables of the climate system, such as the atmospheric partial pressure of CO2 and the radiative forcing of tropospheric ozone, that have an emissions-induced uncertainty representing more than 40% of the uncertainty in the Earth system’s response.

The Wintertime Covariation of CO2 and Criteria Pollutants in an Urban Valley of the Western United States

AbstractNumerous mountain valleys experience wintertime particulate pollution events, when persistent cold air pools (PCAPs) develop and inhibit atmospheric mixing, leading to the accumulation of pollutants. Here we examine the relationships between trace gases and criteria pollutants during winter in Utah's Salt Lake Valley, in an effort to better understand the roles of transport versus chemical processes during differing meteorological conditions as well as insights into how targeted reductions in greenhouse gases will impact local air quality in varying meteorological conditions. CO2 is a chemically inert gas that is coemitted during fossil fuel combustion with pollutants. Many of these coemitted pollutants are precursors that react chemically to form secondary particulate matter. Thus, CO2 can serve as a stable tracer and potentially help distinguish transport versus chemical influences on pollutants. During the winter of 2015–2016, we isolated enhancements in CO2 over baseline levels due to urban emissions (“CO2ex”). CO2ex was paired with similar excesses in other pollutant concentrations. These relationships were examined during different wintertime conditions and stages of pollution episodes: (a) Non‐PCAP, (b) beginning, and (c) latter stages of an episode. We found that CO2ex is a good indicator of the presence of gaseous criteria pollutants and a reasonable indicator of PM2.5. Additionally, the relationships between CO2ex and criteria pollutants differ during different phases of PCAP events which provide insight into meteorological and transport processes. Lastly, we found a slight overestimation of CO:CO2 emission ratios and a considerable overestimation of NOx:CO2 by existing inventories for the Salt Lake Valley.