Main Sources Of Greenhouse Gas Emissions Research Articles

Excessive synthetic fertilizers elevate greenhouse gas emissions of smallholder-scale staple grain production in China

Smallholder farmers produce one-third of the world's food and over 80% of China's; therefore, they must be at the forefront of developing a sustainable food system. Greenhouse gas (GHG) emissions from these farms cannot be ignored. In this study, we created an agricultural environmental impact evaluation framework for China based on a localized database through an extensive survey. The survey was based on face-to-face interviews by 120 investigators with 1015 smallholders in 100 villages within Chinese major agricultural regions. The GHG emissions of each smallholder farmer's staple grain production was assessed on a case-by-case basis. Structural equation models were used to analyze the influence paths of production behavior. The results showed that GHG emissions from smallholder grain production exceeded average global levels. Despite some regional differences, synthetic fertilizers were the main source of GHG emissions from all farm inputs. Increased farm size can reduce nitrogen fertilizer use. The GHG emissions can be reduced by 203.59–279.90 Tg CO2eq, and profits would increase by 62.05–92.42 billion CNY in China, when all smallholders are managed in the same way as the top 25% or 10% of outstanding producers without applying higher nitrogen fertilizer application than the national recommendation. It is urgent and necessary for smallholders to change production practices to reduce their reliance on fertilizers to achieve climate goals.

Spatio-temporal Change in City-level Greenhouse Gas Emissions from Municipal Solid Waste Sector in China During the Last Decade and Its Potential Mitigation

The waste sector is a significant source of greenhouse gas(GHG) emissions and clarifying its emission trends and characteristics is the premise for formulating GHG emission reduction strategies. Using the IPCC inventory model, the GHG emissions from the municipal solid waste(MSW) sector in China during 2010 to 2020 were estimated. The results showed that GHG emissions increased from 42.5 Mt in 2010 to 75.3 Mt in 2019, then decreased to 72.1 Mt in 2020. MSW landfills were the main source of GHG emissions. Further, with the increase in the proportion of waste incineration, the proportion of GHG incineration increased rapidly from 16.5% in 2010 to 60.1% in 2020. In terms of regional distribution, East and South China were the regions with the highest emissions, and Guangdong, Shandong, Jiangsu, and Zhejiang were the provinces with the largest GHG emissions. Implementing MSW classification, changing the MSW disposal modes from landfilling to incineration, improving the LFG collection efficiency of landfills, and using biological functional materials as the cover soil to strengthen the methane oxidation efficiency are the main measures to achieve GHG emission reduction in waste sectors.

Structural characteristics and drivers of greenhouse gas emissions at county-level and long-time scales: A case study of the Anji County, China

To achieve carbon neutrality, the Chinese government needs to gain a comprehensive understanding of the sources and drivers of greenhouse gas (GHG) emissions, particularly at the county level. Anji County in eastern China is a typical example of an industrial transformation from quarrying to a low-carbon economy. This study analyzed the decoupling types and structural characteristics of GHG emissions and the driving factors of carbon dioxide (CO2) emissions in the Anji from 2006 to 2019, and explored the differences between county-level and provincial-level or city-level results. It was observed that energy-related activities are the main source of GHG emissions in Anji and that economic development is the driving factor behind the increasing CO2 emissions. However, industrial transformation and upgradation coupled with the alternative use of clean energy limit the growth of GHG emissions. This study details the GHG emissions of county during the industrial transformation stage and provides corresponding policy recommendations for county governments.

How does soil carbon sequestration affect greenhouse gas emissions from a sheep farming system? Results of a life cycle assessment case study

A life cycle assessment (LCA) study of a transition from semiintensive to semi-extensive Mediterranean dairy sheep farm suggests that the latter has a strong potential for offsetting greenhouse gas (GHG) emissions through the soil C sequestration (Cseq) in permanent grasslands. The extensification process shows clear environmental advantage when emission intensity is referred to the area-based functional unit (FU). Several LCA studies reported that extensive livestock systems have greater GHG emissions per mass of product than intensive one, due to their lower productivity. However, these studies did not account for soil Cseq of temporary and permanent grasslands, that have a strong potential to partly mitigate the GHG balance of ruminant production systems. Our LCA study was carried out considering the transition from a semiintensive (SI) towards a semi-extensive (SE) production system, adopted in a dairy sheep farm located in North-Western Sardinia (Italy). Impact scope included enteric methane emissions, feed production, on-farm energy use and transportation, infrastructures as well as the potential C sink from soil Cseq compared to emission intensity. In order to provide a more comprehensive analysis, we used the following FUs: 1 kg of fat and protein corrected milk (FPCM) and 1 ha of utilised agricultural area (UAA). We observed that the extensification of production system determined contrasting environmental effects when using different FUs accounting for soil Cseq. When soil Cseq in emission intensity estimate was included, we observed slightly lower values of GHG emissions per kg of FPCM in the SI production system (from 3.37 to 3.12 kg CO2 equivalents – CO2-eq), whereas a greater variation we observed in the SE one (from 3.54 to 2.90 kg CO2-eq). Considering 1 ha of UAA as FU and including the soil Cseq, the emission intensity in SI moved from 6257 to 5793 kg CO2-eq, whereas values varied from 4020 to 3299 kg CO2-eq in SE. These results indicated that the emission intensity from semi-extensive Mediterranean dairy sheep farms can be considerably reduced through the soil Cseq, although its measurement is influenced by the models used in the estimation. Highlights - Extensification of dairy sheep systems provides an environmental benefit when soil C sequestration is considered. - Extensification of dairy sheep systems determines lower environmental impact per hectare of utilized agricultural area. - Enteric methane emissions are the main source of GHG emissions of the sheep milk life cycle. - Carbon sequestration in permanent grasslands can considerably contribute to climate change mitigation.

A land-based approach for climate change mitigation in the livestock sector

Greenhouse gas (GHG) emissions from agriculture, forestry and other land uses (AFOLU sector) cover the 24% of global emissions, representing the second hot spot in the contribution to climate change after the energy sector. Thus, the land sector plays a crucial role in the context of climate change, being both a contributor to the problem and part of its solution, particularly thanks to the capacity of soils and biomass to sequester atmospheric carbon. The challenge of this paper is to understand the extent to which sustainable land management can be a valuable solution for increasing the mitigation potential of the land sector, particularly at small-scale rural landscape level.The paper presents and tests a land-based approach to be applied at small-scale rural landscape level, aiming at reducing and offsetting GHG emissions from the livestock activities, one of the main sources of GHG emissions of the whole agricultural sector. The proposed land-based approach builds on an ensemble of methodologies, including Geographic Information System (GIS) elaboration, Life Cycle Assessment (LCA) and methodologies from the Intergovernmental Panel on Climate Change (IPCC), that allow estimating livestock GHG emissions and the mitigation potential of sustainable land-use options applied in the same small-scale rural landscape.Results from a case study in Italy show that land-based mitigation options applied at small-scale rural landscape level can reduce and completely offset the GHG livestock emissions of the same area, leading to carbon neutral livestock systems. Thus, this study confirms that the land sector can strongly contribute to climate change mitigation if sustainable land-use options are applied.

Energy Balances and Greenhouse Gas Emissions of Agriculture in the Shihezi Oasis of China

The objective of this study was to evaluate the difference of crop and livestock products regarding energy balances, greenhouse gas (GHG) emissions, carbon economic efficiency, and water use efficiency using a life cycle assessment (LCA) methodology on farms in three sub-oases within the Shihezi Oasis of China. The three sub-oases were selected within the Gobi Desert, at Shizongchang (SZC), Xiayedi (XYD), and Mosuowan (MSW), to represent the various local oasis types: i. Oasis; ii. overlapping oasis-desert; and iii. Gobi oasis. The results indicated that crop production in XYD Oasis had higher energy balances (221.47 GJ/ha), and a net energy ratio (5.39), than in the other two oases (p < 0.01). The production of 1 kg CW of sheep in XYD Oasis resulted in significantly higher energy balances (18.31 MJ/kg CW), and an energy ratio (2.21), than in the other two oases (p < 0.01). The water use efficiency of crop production in the SZC Oasis was lower than that of the XYD and MSW oases (p < 0.05). Alfalfa production generated the lowest CO2-eq emissions (8.09 Mg CO2-eq/ha. year) and had the highest water use efficiency (45.82 MJ/m3). Alfalfa (1.18 ¥/kg CO2-eq) and maize (1.14 ¥/kg CO2-eq) had a higher carbon economic efficiency than other crops (p < 0.01). The main sources of GHG emissions for crop production were fertilizer and irrigation. The structural equation modelling (SEM) of agricultural systems in the Shihezi Oasis showed that the livestock category significantly influenced the economic income, energy, and carbon balances.

Comparative life cycle assessment of station-based and dock-less bike sharing systems

Bike sharing system (BSS) is growing worldwide. Although bike sharing is viewed as a sustainable transportation mode, it still has environmental footprints from its operation (e.g., bike rebalancing using automobiles) and upstream impacts (e.g., bike manufacturing). Thus, evaluating the environmental impacts of BSS from the life cycle perspective is vital to inform decision making for the system design and operation. In this study, we conducted a comparative life cycle assessment (LCA) of station-based and dock-less BSS in the U.S. The results show that dock-less BSS has a greenhouse gas (GHG) emissions factor of 118 g CO2-eq/bike-km in the base scenario, which is 82% higher than the station-based system. Bike rebalancing is the main source of GHG emissions, accounting for 36% and 73% of the station-based and dock-less systems, respectively. However, station-based BSS has 54% higher total normalized environmental impacts (TNEI), compared to dock-less BSS. The dock manufacturing dominants the TNEI (61%) of station-based BSS and the bike manufacturing contributes 52% of TNEI in dock-less BSS. BSS can also bring environmental benefits through substituting different transportation modes. Car trip replacement rate is the most important factor. The results suggest four key approaches to improve BSS environmental performance: 1) optimizing the bike distribution and rebalancing route or repositioning bikes using more sustainable approaches, 2) incentivizing more private car users to switch to using BSSs, 3) prolonging lifespans of docking infrastructure to significantly reduce the TNEI of station-based systems, and 4) increasing the bike utilization efficiency to improve the environmental performance of dock-less systems.

Contrasted seasonal balances in a Sahelian pastoral ecosystem result in a neutral annual carbon balance

This paper explores an original approach in which greenhouse gas (GHG) emissions and carbon (C) accumulation are assessed monthly and at landscape scale to account for the highly seasonal monsoon climate and the mobility of pastoral herds that characterize West African pastoral ecosystems.The study was conducted in northern Senegal, in the service area of the Widou Thiengoly borehole, a circular zone of 706 km2 centered on the borehole. The C balance was calculated using an ecosystem approach, i.e. taking all main sources of GHG emissions and C sinks of the ecosystem, not only anthropogenic sources, into account.The annual C balance of the pastoral ecosystem was −0.04 ± 0.01 tC-eq.ha−1.year−1, showing that total GHG emissions were mitigated by C accumulation in trees, soil and livestock. The C balance varied considerably with the seasons, with a positive monthly balance in the wet season, from July to October (+0.58 tC-eq.ha−1.month−1) and a negative monthly balance in the cold dry season from November to February and the hot dry season from March to June (−0.57 and −0.05 tC-eq.ha−1.month−1 respectively).Care should be taken when generalizing these results, which were obtained in a dry year, because of strong inter-annual variations in rainfall.

Energy usage and greenhouse gas emissions associated with tea and rubber manufacturing processes in Sri Lanka

The objective of this study was to analyze the greenhouse gas (GHG) emissions associated with energy usage in tea and rubber industries in Sri Lanka. The scope of the study covered GHG inventory analysis of carbon dioxide, methane and nitrous oxide emissions associated with tea and rubber products, considering a life cycle approach starting from the plantations to the processed products. The functional units of tea and rubber products were ‘one metric ton of tea’ and ‘one metric ton of dry rubber content (DRC)’ respectively. Total GHG emission ranged from 514.27 ± 68.66 (high-grown) to 603.10 ± 191.58 (Uva) kg CO2e ton−1 of made tea and the emissions were not statistically significant (p > 0.05; ANOVA and Tukey's multiple comparison tests) among the four tea growing regions, namely, high-grown, mid-grown, low-grown and Uva regions. The electricity consumption contributed 63% of the GHG emissions in tea industry and the rest of the emissions were from fossil fuel (23%) and biomass (14%) usage. GHG emissions associated with rubber plantations were 155.6 ± 47.4 kg CO2e per ton of DRC. GHG emissions in raw rubber processing factories of crepe and ribbed smoked sheet (RSS), centrifuged latex and technically specified rubber (TSR) were 168.6 ± 44.1, 125.1 ± 24.8 and 375.60 kg CO2e per ton of DRC respectively. GHG emissions associated with latex based and dry rubber based industries were 1472.1 ± 1011.8 and 1801.23 ± 360.26 kg CO2e per ton of DRC respectively. The main source of GHG emissions in rubber industry was the use of grid electricity. GHG emissions associated with electricity usage in rubber plantations, crepe and RSS, centrifuged latex, TSR, latex based and dry rubber based industries were 15%, 80%, 42%, 53%, 75% and 52% respectively and the remaining emissions were from diesel, biomass, and fuel oil usage. Fuel switching in the manufacture of dry rubber based products has contributed to mitigation of GHG emissions by about 80%.

Greenhouse gas emissions from agricultural food production to supply Indian diets: Implications for climate change mitigation

Agriculture is a major source of greenhouse gas (GHG) emissions globally. The growing global population is putting pressure on agricultural production systems that aim to secure food production while minimising GHG emissions. In this study, the GHG emissions associated with the production of major food commodities in India are calculated using the Cool Farm Tool. GHG emissions, based on farm management for major crops (including cereals like wheat and rice, pulses, potatoes, fruits and vegetables) and livestock-based products (milk, eggs, chicken and mutton meat), are quantified and compared. Livestock and rice production were found to be the main sources of GHG emissions in Indian agriculture with a country average of 5.65kg CO2eq kg−1 rice, 45.54kg CO2eq kg−1 mutton meat and 2.4kg CO2eq kg−1 milk. Production of cereals (except rice), fruits and vegetables in India emits comparatively less GHGs with <1kg CO2eq kg−1 product. These findings suggest that a shift towards dietary patterns with greater consumption of animal source foods could greatly increase GHG emissions from Indian agriculture. A range of mitigation options are available that could reduce emissions from current levels and may be compatible with increased future food production and consumption demands in India.

Determinants of GHG emissions for a municipal economy: Structural decomposition analysis of Chongqing

The prefecture-level municipality of Chongqing, in western China, is the largest and most populous city in China. Chongqing’s uniqueness presents multiple challenges, including that greenhouse gas (GHG) emissions abetment requirement of the city is greater than that of other Chinese cities. This paper explores factors behind change in aggregate greenhouse gas (GHG) emissions in Chongqing, including differences at the sector level. We use a structure decomposition analysis (SDA) method to quantify sources of emissions growth. Results indicate that the crucial factors that drive GHG emissions reduction relate to intensities and input-output structure; and that the main driver of emissions growth was increasing final demand. The analysis also reveals that the mining and coal-washing sector and the metals melting and rolling sector were the main sources of GHG emissions in Chongqing.

Energy-related GHG emissions of the textile industry in China

As the sixth largest energy consuming industry sector in China, the textile industry is encountering great challenges in reducing Greenhouse Gas (GHG) emissions. Considering the existing studies have the limitation of lacking updated data and include limited energy sources, this study will conduct a comprehensive analysis of the GHG emissions in China's textile industry and analyze the emission characteristics. The results show that coal consumption is the main source of GHG emissions in China's textile industry. The second largest GHG emission source is electricity consumption, which is primarily from the Eastern China, Central China and Northern China Power Grids. A driving force factor analysis reveals that the order of intensity for the driving forces is the production scale, the energy intensity, the energy structure and the emission factors. In particular, the increasing scale of production is the main factor driving increasing GHG emissions; however, energy intensity reduction and energy structure optimization can effectively reduce GHG emissions. This study also summarizes the main energy saving measures being used by the textile industry in China. The measures used in the spinning, weaving and wetting processes are found to have high energy saving potential and a short payback period. Scenario analysis indicates that under the optimal technology application scenario, GHG emissions would be 34.3% less than emissions under the baseline scenario in 2030. Furthermore, GHG emissions per unit output value would be 0.18t/million RMB, which approaches the advanced international level of 0.14t/million RMB. Corresponding polices for reducing GHG emission in the textile industry need to be considered based on the implications indicated in this study.

Mountain forest wood fuel supply chains: comparative studies between Norway and Italy

Case studies of mountain forest wood fuel supply chains from Norway and Italy are presented and compared. Results from previous studies in which greenhouse gas emissions and costs were evaluated using life cycle assessment and cost analysis respectively, are compared. The supply chain is more mechanized in Norway than Italy. Steeper terrain and low road density partly explain the persistence of motor-manual felling in the Italian case. Mechanized forest harvesting can increase productivity and reduce costs, but generates more greenhouse gas (GHG) emissions than motor-manual harvesting. In both cases, the main sources of GHG emissions are truck transportation and chipping. The total emissions are 22.9 kg CO2/m3s.o.b. (Norway) and 13.2 kg CO2/m3s.o.b. (Italy). The Norwegian case has higher costs than the Italian one, 64 €/m3s.o.b. and 41 €/m3s.o.b. respectively, for the overall supply chain. The study shows that mountain forests constitute an interesting source for fuel biomass in both areas, but are a rather costly source, particularly in Norway. The study also exemplifies the care needed in transferring LCA results between regions and countries, particularly where forest biomass is involved.

Greenhouse gas emissions from hydropower: The state of research in 1996

This paper reports on the findings of a recent IAEA expert meeting on the assessment of greenhouse gas (GHG) emissions from the full ‘lifecycle’ of hydropower. It discusses the different categories of hydropower plants in view of the two main sources of GHG emissions: first, direct and indirect emissions associated with the construction of the plants; second, emissions from decaying biomass from land flooded by hydro reservoirs. In terms of GHG emissions, this paper shows that, in most cases, hydropower is a good alternative to fossil fuelled power generation. For hydropower plants in cold climate, a typical GHG emission factor is 15 g CO 2 equivalent/kWh, which is 30–60 times less than the factors of usual fossil fuel generation. For some hydropower plants in tropical climates, theoretical calculations have shown that reservoir emissions could be very high. However, no measurements of emissions were taken from tropical reservoirs and the current level of research does not allow for a reliable evaluation. Research is urgently needed in humid tropical climates.