First assessment of methane and carbon dioxide emissions from shallow and deep zones of boreal reservoirs upon ice break‐up

Abstract. Surface water pCO2 and pCH4 measurements were taken in the boreal zone of Québec, Canada, from summer 2006 to summer 2008 in Eastmain 1 reservoir and two nearby lakes. The goal of this follow-up was to evaluate annual greenhouse gas (GHG) emissions, including spring emissions (N.B. gross emissions for reservoir), through flux calculations using the thin boundary layer model. Our measurements underscored the winter CO2 accumulation due to ice cover and the importance of a reliable estimate of spring diffusive emissions as the ice breaks up. We clearly demonstrated that in our systems, diffusive CH4 flux (in terms of CO2 equivalent) were of minor importance in the GHG emissions (without CH4 accumulation under ice), with diffusive CO2 flux generally accounting for more than 95% of the annual diffusive flux. We also noted the extent of spring diffusive CO2 emissions (23% to 52%) in the annual carbon budget.

Estimates of GHG emissions by hydroelectric reservoirs: The Brazilian case

Recent studies indicate that greenhouse gas (GHG) emissions from agricultural drainage ditches can be significant on a per-unit area basis, but spatiotemporal investigations are still limited. Additionally, the impact of dredging - a common management in such environments - on ditch GHG emissions is largely unknown. This study presents year-round GHG emissions from nine ditches on a dairy farm in the center of the Netherlands, where each year, approximately half of the ditches are dredged in alternating cycles. We measured monthly diffusive fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), along with ebullitive CH4 emissions, supplemented by diel flux measurements (i.e., 24-h measurements) conducted in summer and winter. Our findings indicate that while diffusive GHG fluxes exhibited low spatiotemporal variation, ebullitive CH4 emissions were significantly higher during warmer periods and marginally elevated at ditch intersections. CH4 ebullition was the dominant pathway of ditch GHG emissions, accounting for 58% of the total annual emissions, followed by CO2 (39%), and N2O (3%). Approximately 80% of the total CH4 emissions occurred through ebullition during spring and summer. The average CH4 emission factor estimated for our ditches (574kgha-1 year-1) is ∼40% higher than the Tier-1 value suggested by the IPCC for ditches on mineral soils (416kgha-1 year-1). Based on two 24-h measurement campaigns, we concluded that neglecting nighttime diffusive CO2 and CH4 emissions may lead to inaccurate estimates of annual ditch GHG emissions, with ∼12% underestimation in this study. Although dredging led to subtle increases in water-to-atmosphere GHG emissions immediately after the activity, it reduced overall annual GHG emissions by ∼35%. This study highlights the importance of CH4 ebullition and of capturing diel cycles of diffusive emissions to accurately assess ditch GHG emissions and underscores the importance of considering seasonal variations and dredging practices when budgeting ditch GHG emissions.

The cumulative emissions of CO2 and CH4 had a great impact on the global climate, and the responsibility of countries around the world to achieve greenhouse gas (GHG) emission control goals should be based on the concept of fairness and sustainable development. In this paper, from the perspective of interpersonal equity, based on the annual GHG emissions per capita, using the CO2 and CH4 emissions data of 23 major countries from 1961 to 2017, the ratio for GHG emission per capita per year and the ratio for carbon dioxide emission per capita per year in various countries were calculated with 1961 and 1990 as the starting years, the countries were also sequenced and sorted to analyze the extent to which major countries occupy limited global emissions space at different time scales and GHG ranges. The results showed that the ratio of GHG emission per capita per year in developed countries such as the United States and Canada were far higher than the world average, China was significantly lower than the average, India was much lower than the average. In addition, lengthening the time scale and incorporating the methane emissions from the planting and breeding industry (agriculture activities) had a significant impact on the the ratio of GHGemission per capita and national classification. It can be more conducive to judge the world's average annual GHG emissions, reflect the global emission space occupied by each countries comprehensively and objectively, and scientifically support policymakers in formulating action plan for GHGemission reduction and control, which was of practical significance.

Globally, agriculture is directly responsible for 14% of annual greenhouse gas(GHG) emissions and induces an additional 17% through land use change, mostlyin developing countries (Vermeulen et al 2012). Agricultural intensification andexpansion in these regions is expected to catalyze the most significant relativeincreases in agricultural GHG emissions over the next decade (Smith et al 2008,Tilman et al 2011). Farms in the developing countries of sub-Saharan Africa andAsia are predominately managed by smallholders, with 80% of land holdingssmaller than ten hectares (FAO 2012). One can therefore posit that smallholderfarming significantly impacts the GHG balance of these regions today and willcontinue to do so in the near future.However, our understanding of the effect smallholder farming has on theEarth’s climate system is remarkably limited. Data quantifying existing andreduced GHG emissions and removals of smallholder production systems areavailable for only a handful of crops, livestock, and agroecosystems (Herrero et al2008, Verchot et al 2008, Palm et al 2010). For example, fewer than fifteenstudies of nitrous oxide emissions from soils have taken place in sub-SaharanAfrica, leaving the rate of emissions virtually undocumented. Due to a scarcity ofdata on GHG sources and sinks, most developing countries currently quantifyagricultural emissions and reductions using IPCC Tier 1 emissions factors.However, current Tier 1 emissions factors are either calibrated to data primarilyderived from developed countries, where agricultural production conditions aredissimilar to that in which the majority of smallholders operate, or from data thatare sparse or of mixed quality in developing countries (IPCC 2006). For the mostpart, there are insufficient emissions data characterizing smallholder agricultureto evaluate the level of accuracy or inaccuracy of current emissions estimates.Consequentially, there is no reliable information on the agricultural GHG budgetsfor developing economies. This dearth of information constrains the capacity totransition to low-carbon agricultural development, opportunities for smallholdersto capitalize on carbon markets, and the negotiating position of developingcountries in global climate policy discourse.Concerns over the poor state of information, in terms of data availability andrepresentation, have fueled appeals for new approaches to quantifying GHGemissions and removals from smallholder agriculture, for both existing conditionsand mitigation interventions (Berry and Ryan 2013, Olander et al 2013).Considering the dependence of quantification approaches on data and the currentdata deficit for smallholder systems, it is clear that in situ measurements must bea core part of initial and future strategies to improve GHG inventories and

BackgroundPolicies to mitigate climate change by reducing greenhouse gas (GHG) emissions can yield public health benefits by also reducing emissions of hazardous co-pollutants, such as air toxics and particulate matter. Socioeconomically disadvantaged communities are typically disproportionately exposed to air pollutants, and therefore climate policy could also potentially reduce these environmental inequities. We sought to explore potential social disparities in GHG and co-pollutant emissions under an existing carbon trading program—the dominant approach to GHG regulation in the US and globally.Methods and findingsWe examined the relationship between multiple measures of neighborhood disadvantage and the location of GHG and co-pollutant emissions from facilities regulated under California’s cap-and-trade program—the world’s fourth largest operational carbon trading program. We examined temporal patterns in annual average emissions of GHGs, particulate matter (PM2.5), nitrogen oxides, sulfur oxides, volatile organic compounds, and air toxics before (January 1, 2011–December 31, 2012) and after (January 1, 2013–December 31, 2015) the initiation of carbon trading. We found that facilities regulated under California’s cap-and-trade program are disproportionately located in economically disadvantaged neighborhoods with higher proportions of residents of color, and that the quantities of co-pollutant emissions from these facilities were correlated with GHG emissions through time. Moreover, the majority (52%) of regulated facilities reported higher annual average local (in-state) GHG emissions since the initiation of trading. Neighborhoods that experienced increases in annual average GHG and co-pollutant emissions from regulated facilities nearby after trading began had higher proportions of people of color and poor, less educated, and linguistically isolated residents, compared to neighborhoods that experienced decreases in GHGs. These study results reflect preliminary emissions and social equity patterns of the first 3 years of California’s cap-and-trade program for which data are available. Due to data limitations, this analysis did not assess the emissions and equity implications of GHG reductions from transportation-related emission sources. Future emission patterns may shift, due to changes in industrial production decisions and policy initiatives that further incentivize local GHG and co-pollutant reductions in disadvantaged communities.ConclusionsTo our knowledge, this is the first study to examine social disparities in GHG and co-pollutant emissions under an existing carbon trading program. Our results indicate that, thus far, California’s cap-and-trade program has not yielded improvements in environmental equity with respect to health-damaging co-pollutant emissions. This could change, however, as the cap on GHG emissions is gradually lowered in the future. The incorporation of additional policy and regulatory elements that incentivize more local emission reductions in disadvantaged communities could enhance the local air quality and environmental equity benefits of California’s climate change mitigation efforts.

Abstract. This paper summarizes currently available data on greenhouse gas (GHG) emissions from African natural ecosystems and agricultural lands. The available data are used to synthesize current understanding of the drivers of change in GHG emissions, outline the knowledge gaps, and suggest future directions and strategies for GHG emission research. GHG emission data were collected from 75 studies conducted in 22 countries (n = 244) in sub-Saharan Africa (SSA). Carbon dioxide (CO2) emissions were by far the largest contributor to GHG emissions and global warming potential (GWP) in SSA natural terrestrial systems. CO2 emissions ranged from 3.3 to 57.0 Mg CO2 ha−1 yr−1, methane (CH4) emissions ranged from −4.8 to 3.5 kg ha−1 yr−1 (−0.16 to 0.12 Mg CO2 equivalent (eq.) ha−1 yr−1), and nitrous oxide (N2O) emissions ranged from −0.1 to 13.7 kg ha−1 yr−1 (−0.03 to 4.1 Mg CO2 eq. ha−1 yr−1). Soil physical and chemical properties, rewetting, vegetation type, forest management, and land-use changes were all found to be important factors affecting soil GHG emissions from natural terrestrial systems. In aquatic systems, CO2 was the largest contributor to total GHG emissions, ranging from 5.7 to 232.0 Mg CO2 ha−1 yr−1, followed by −26.3 to 2741.9 kg CH4 ha−1 yr−1 (−0.89 to 93.2 Mg CO2 eq. ha−1 yr−1) and 0.2 to 3.5 kg N2O ha−1 yr−1 (0.06 to 1.0 Mg CO2 eq. ha−1 yr−1). Rates of all GHG emissions from aquatic systems were affected by type, location, hydrological characteristics, and water quality. In croplands, soil GHG emissions were also dominated by CO2, ranging from 1.7 to 141.2 Mg CO2 ha−1 yr−1, with −1.3 to 66.7 kg CH4 ha−1 yr−1 (−0.04 to 2.3 Mg CO2 eq. ha−1 yr−1) and 0.05 to 112.0 kg N2O ha−1 yr−1 (0.015 to 33.4 Mg CO2 eq. ha−1 yr−1). N2O emission factors (EFs) ranged from 0.01 to 4.1 %. Incorporation of crop residues or manure with inorganic fertilizers invariably resulted in significant changes in GHG emissions, but results were inconsistent as the magnitude and direction of changes were differed by gas. Soil GHG emissions from vegetable gardens ranged from 73.3 to 132.0 Mg CO2 ha−1 yr−1 and 53.4 to 177.6 kg N2O ha−1 yr−1 (15.9 to 52.9 Mg CO2 eq. ha−1 yr−1) and N2O EFs ranged from 3 to 4 %. Soil CO2 and N2O emissions from agroforestry were 38.6 Mg CO2 ha−1 yr−1 and 0.2 to 26.7 kg N2O ha−1 yr−1 (0.06 to 8.0 Mg CO2 eq. ha−1 yr−1), respectively. Improving fallow with nitrogen (N)-fixing trees led to increased CO2 and N2O emissions compared to conventional croplands. The type and quality of plant residue in the fallow is an important control on how CO2 and N2O emissions are affected. Throughout agricultural lands, N2O emissions slowly increased with N inputs below 150 kg N ha−1 yr−1 and increased exponentially with N application rates up to 300 kg N ha−1 yr−1. The lowest yield-scaled N2O emissions were reported with N application rates ranging between 100 and 150 kg N ha−1. Overall, total CO2 eq. emissions from SSA natural ecosystems and agricultural lands were 56.9 ± 12.7 × 109 Mg CO2 eq. yr−1 with natural ecosystems and agricultural lands contributing 76.3 and 23.7 %, respectively. Additional GHG emission measurements are urgently required to reduce uncertainty on annual GHG emissions from the different land uses and identify major control factors and mitigation options for low-emission development. A common strategy for addressing this data gap may include identifying priorities for data acquisition, utilizing appropriate technologies, and involving international networks and collaboration.

Executive Summary: The California Climate Action Registry, which was initially established in 2000 and began operation in Fall 2002, is a voluntary registry for recording annual greenhouse gas (GHG) emissions. The purpose of the Registry is to assist California businesses and organizations in their efforts to inventory and document emissions in order to establish a baseline and to document early actions to increase energy efficiency and decrease GHG emissions. The State of California has committed to use its ''best efforts'' to ensure that entities that establish GHG emissions baselines and register their emissions will receive ''appropriate consideration under any future international, federal, or state regulatory scheme relating to greenhouse gas emissions.'' Reporting of GHG emissions involves documentation of both ''direct'' emissions from sources that are under the entity's control and indirect emissions controlled by others. Electricity generated by an off-site power source is consider ed to be an indirect GHG emission and is required to be included in the entity's report. Registry participants include businesses, non-profit organizations, municipalities, state agencies, and other entities. Participants are required to register the GHG emissions of all operations in California, and are encouraged to report nationwide. For the first three years of participation, the Registry only requires the reporting of carbon dioxide (CO2) emissions, although participants are encouraged to report the remaining five Kyoto Protocol GHGs (CH4, N2O, HFCs, PFCs, and SF6). After three years, reporting of all six Kyoto GHG emissions is required. The enabling legislation for the Registry (SB 527) requires total GHG emissions to be registered and requires reporting of ''industry-specific metrics'' once such metrics have been adopted by the Registry. The Ernest Orlando Lawrence Berkeley National Laboratory (Berkeley Lab) was asked to provide technical assistance to the California Energy Commission (Energy Commission) related to the Registry in three areas: (1) assessing the availability and usefulness of industry-specific metrics, (2) evaluating various methods for establishing baselines for calculating GHG emissions reductions related to specific actions taken by Registry participants, and (3) establishing methods for calculating electricity CO2 emission factors. The third area of research was completed in 2002 and is documented in Estimating Carbon Dioxide Emissions Factors for the California Electric Power Sector (Marnay et al., 2002). This report documents our findings related to the first areas of research. For the first area of research, the overall objective was to evaluate the metrics, such as emissions per economic unit or emissions per unit of production that can be used to report GHG emissions trends for potential Registry participants. This research began with an effort to identify methodologies, benchmarking programs, inventories, protocols, and registries that u se industry-specific metrics to track trends in energy use or GHG emissions in order to determine what types of metrics have already been developed. The next step in developing industry-specific metrics was to assess the availability of data needed to determine metric development priorities. Berkeley Lab also determined the relative importance of different potential Registry participant categories in order to asses s the availability of sectoral or industry-specific metrics and then identified industry-specific metrics in use around the world. While a plethora of metrics was identified, no one metric that adequately tracks trends in GHG emissions while maintaining confidentiality of data was identified. As a result of this review, Berkeley Lab recommends the development of a GHG intensity index as a new metric for reporting and tracking GHG emissions trends.Such an index could provide an industry-specific metric for reporting and tracking GHG emissions trends to accurately reflect year to year changes while protecting proprietary data. This GHG intensity index changes while protecting proprietary data. This GHG intensity index would provide Registry participants with a means for demonstrating improvements in their energy and GHG emissions per unit of production without divulging specific values. For the second research area, Berkeley Lab evaluated various methods used to calculate baselines for documentation of energy consumption or GHG emissions reductions, noting those that use industry-specific metrics. Accounting for actions to reduce GHGs can be done on a project-by-project basis or on an entity basis. Establishing project-related baselines for mitigation efforts has been widely discussed in the context of two of the so-called ''flexible mechanisms'' of the Kyoto Protocol to the United Nations Framework Convention on Climate Change (Kyoto Protocol) Joint Implementation (JI) and the Clean Development Mechanism (CDM).

Rising need for various renewable and non-renewable energy resources became vital for developing countries to meet their rapid economic growth under an exponentially growing population scenario. The primary goal of COP-26 for climate change mitigation is to reduce greenhouse gas (GHG) emissions from different sectors. Because of their significant contribution to global warming, GHG emissions from hydroelectric reservoirs have been a contentious topic of discussion since the pre-industrial age. However, the exact methodology for quantification of GHG and important parameters affecting emission rate is difficult due to limited equipment facilities, techniques for GHG measurement, uncertainties in GHG emissions rate, insufficient GHG database, and significant spatio-temporal variability of emission in the global reservoirs. This paper discusses the current scenario of GHG emissions from renewable energy, with a focus on hydroelectric reservoirs, methodological know-how, the interrelationship between parameters impacting GHG emissions, and mitigation techniques. Aside from that, significant methods and approaches for predicting GHG emissions from hydroelectric reservoirs, accounting for GHG emissions, life cycle assessment, uncertainty sources, and knowledge gaps, have been thoroughly discussed.

BackgroundThe carbon footprint of severe asthma and the impact of biologic therapy in this population is unknown.MethodsThis was a retrospective cohort study in adults with severe asthma, using data from the Northern Ireland Regional Severe Asthma Service (September 2015–November 2021). We calculated annual greenhouse gas (GHG) emissions (carbon dioxide equivalent) for asthma-related medications and healthcare resource utilisation, compared patient characteristics by GHG quartile, calculated GHG change post-biologic initiation, and explored the relationship between GHG change and clinical response.ResultsAmong 303 patients with severe asthma, mean±sd GHG emissions were 474±431 kg, largely driven by SABA use (50.7%) and emergency department (ED) visits/inpatient admissions (21.0%). Those with highest-quartile GHG emissions were more likely to have uncontrolled disease (Asthma Control Questionnaire-5 score 3.5 versus 2.5; p<0.001), be more deprived (46.1% versus 25.0%; p=0.029) and have depression/anxiety (35.5% versus 14.7%; p=0.002) versus those with lowest-quartile GHG emissions. Among patients who received a biologic (n=213), modest GHG reductions (−28.0±286 kg; p=0.15) were observed, largely driven by a reduction in ED/hospitalisation-related GHG emissions (−59.3±224 kg; p<0.001). SABA-related GHG emissions were relatively unchanged (−6.1±138 kg; p=0.518). Total GHG emissions were 72.4±352 kg (p=0.044) lower than baseline at 4 years post-biologic initiation. Although there was substantial clinical improvement post-biologic initiation, this was not associated with GHG reductions.ConclusionsSevere asthma is associated with substantial GHG emissions, primarily driven by SABA use and emergency care utilisation. Although GHG emissions were lower post-biologic, largely due to a reduction in emergency care, the changes in GHG emissions were modest and SABA use was relatively unchanged. An improved understanding of the factors driving elevated GHG emissions is required.

Potential of greenhouse gas emissions from sewage sludge management: a case study of Taiwan

At present, urban greenhouse gas (GHG) emissions from different wastewater treatment stages are attracting increasing attention. Based on the Guidelines of the China Greenhouse Gas List Compilation (Trial) and the IPCC National Greenhouse Gas List Guidelines in 2006, this paper evaluated urban GHG emissions from wastewater treatment in China from 2011 to 2020. The contribution rates of GHG emissions to the total GHG emissions were calculated for the different wastewater treatment stages. The variations in annual GHG emissions and differences in GHG emissions among different regions and provinces were also analyzed. The total amount of equivalent CO2 emissions reaches 1478.51 million tons, and the annual average amount of equivalent CO2 emissions from 2011 to 2020 is 147.9 million tons, which shows a trend of decreasing first and then increasing. The distribution of GHG emissions from wastewater treatment is uneven among provinces and regions; Guangdong Province has the highest emission, while the Xizang autonomous Region has the lowest. The correlation and contribution rate analysis revealed that paper production and chemical and side food production could discharge a large amount of wastewater with a high COD content, which may have an important impact on GHG emissions during the wastewater treatment stages. According to the study results, CH4 accounts for the largest proportion (63.08%) of the total GHG emissions. The most important source of CH4 comes from the industrial wastewater treatment stage. The annual average CO2 emissions account for 22.24% of the total GHG emissions, which are mainly from the power and chemical consumption stage. The annual average N2O emissions account for 14.68% of the total GHG emissions and are mainly from the wastewater collection and discharge stage. Therefore, in the future, GHG emission reduction strategies should focus on CH4 emissions in the industrial wastewater treatment stage and develop CH4 recycling and utilization technologies.

Better information on greenhouse gas (GHG) emissions and mitigation potential in the agricultural sector is necessary to manage these emissions and identify responses that are consistent with the food security and economic development priorities of countries. Critical activity data (what crops or livestock are managed in what way) are poor or lacking for many agricultural systems, especially in developing countries. In addition, the currently available methods for quantifying emissions and mitigation are often too expensive or complex or not sufficiently user friendly for widespread use.The purpose of this focus issue is to capture the state of the art in quantifying greenhouse gases from agricultural systems, with the goal of better understanding our current capabilities and near-term potential for improvement, with particular attention to quantification issues relevant to smallholders in developing countries. This work is timely in light of international discussions and negotiations around how agriculture should be included in efforts to reduce and adapt to climate change impacts, and considering that significant climate financing to developing countries in post-2012 agreements may be linked to their increased ability to identify and report GHG emissions (Murphy et al 2010, CCAFS 2011, FAO 2011).

Greenhouse gas emissions and affecting factors in forests with undrained and drained nutrient-rich organic soil. LSFRI “Silava” and Latvia University of Life Sciences and Technologies, 2023. Butlers A., supervisor Dr. silv. A. Lazdiņš. The volume of thesis: 105 pages, 19 tables, 39 figures, 5 annexes, and 296 references. The doctoral thesis has been elaborated at the Latvian State Forest Research Institute “Silava” and Latvia University of Life Sciences and Technologies, Forest Faculty, Department of forestry from 2019 to 2023. The topicality of this study is determined by the Paris Agreement and related international regulatory acts, which stipulate that after 2050, the land use, land use change, and forestry (LULUCF) sector must compensate for Latvia's total greenhouse gas (GHG) emissions. Organic forest soils, particularly peat and peaty soils in Latvia, are a significant source of GHG emissions in the country, and one of the most effective climate change mitigation measures in the LULUCF sector is related to their management. However, there is currently a lack of knowledge on the potential contribution of forests with different nutrient availability organic soil management scenarios to mitigating climate change. In the national GHG inventory, a single carbon dioxide (CO2) emission factor (EF) obtained from national studies is applied to calculate the CO2 emissions from drained organic soil, regardless of its nutrient availability. For the calculation of methane (CH4) and nitrous oxide (N2O) emissions, unverified EFs developed in studies in a temperate climate zone are used in the national inventory. This study aims to develop GHG EFs for drained and undrained nutrient-rich organic forest soils and to estimate the net GHG emissions of the forest ecosystem with such soils. The acquired knowledge can be used to improve the national GHG inventory methodology and to plan climate change mitigation measures. Empirical material for characterizing soil GHG emissions and soil C input was collected during a 12-month monitoring period in 31 forest compartments with clearcuts and forest stands in various stages of development. Measurements of soil CO2, CH4, and N2O emissions, as well as soil C input by foliar litter, were carried out in five replicates in each plot with an interval of four weeks. Simultaneously with the GHG measurements, soil and air temperature, as well as groundwater level, were also determined. Soil C input by ground vegetation and fine roots of trees was estimated by biomass measurements at the end of the growing season. Changes in soil C stock were calculated by summing the estimated annual cumulative soil CO2-C emissions and C input. The evaluated relationships between soil GHG emissions, C input, and affecting factors were used to quantify the dynamics of the ecosystem’s annual net GHG emissions in managed forests, by taking into account also the annual C sequestration in living biomass and deadwood, harvested wood products, and the biofuel replacement effect. The estimated annual gross soil CO2 emissions in clearcuts (7.70 ± 0.53 t C ha–1 year–1) are significantly higher than in forest stands (6.14 ± 0.15 t C ha–1 year–1). During the forest management cycle, the annual net CO2 sequestration by nutrient-rich drained and undrained forest soils is on average 0.28 ± 0.66 t C ha–1 year–1 and 0.42 ± 0.43 t C ha–1 year–1, respectively. In forest stands, the main sources of soil C input are ground vegetation and foliar litter, providing an average of 41 ± 8 % and 43 ± 6 % of the total soil C input estimated in the study, respectively. Managed forests with undrained and drained nutrient-rich soil sequester an average of 0.2 ± 9.7 and 2.9 ± 14.4 t CO2 eq year–1, respectively.

This paper presents a preliminary assessment of greenhouse gas (GHG) emissions from all major hydropower reservoirs in Malaysia from the period of 1930–2017. The GHG emissions are calculated based on the Tier 1 method as recommended in International Government Panel on Climate Change (IPCC) guidelines. The results showed that approximately 151.64 Gg of annual methane emission released from hydropower dams in Peninsular Malaysia. While in East Malaysia, hydropower dams release 235.7 Gg of methane emission annually. Bakun dam contributes the most 41.26% of total annual methane emission from hydropower dams in Malaysia. Ulu Jelai hydroelectric dam with design power capacity of 372 MW contributes the least CH4 emission of 0.02 Gg CH4 yr−1. It is seen that high head hydroelectric dam with small reservoir surface area is the most sustainable hydropower dam in reducing the GHG emission. However, long-term measurements must be made in order to clarify the net GHG emissions from reservoir surface, turbines, spillway and downstream river of hydropower dams in Malaysia.