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Addressing Biogenic Greenhouse Gas Emissions from Hydropower in LCA
Abstract
The ability of hydropower to contribute to climate change mitigation is sometimes questioned, citing emissions of methane and carbon dioxide resulting from the degradation of biogenic carbon in hydropower reservoirs. These emissions are, however, not always addressed in life cycle assessment, leading to a bias in technology comparisons, and often misunderstood. The objective of this paper is to review and analyze the generation of greenhouse gas emissions from reservoirs for the purpose of technology assessment, relating established emission measurements to power generation. A literature review, data collection and statistical analysis of methane and CO2 emissions are conducted. In a sample of 82 measurements, methane emissions per kWh hydropower generated are log-normally distributed, ranging from micrograms to 10s of kg. A statistical multivariate regression analysis shows that the reservoir area per kWh electricity is the main most important explanatory variable. Methane emissions flux per reservoir area are correlated with the natural net primary production of the area, the age of the power plant, and the inclusion of bubbling emissions in the measurement. Even together, these factors fail to explain most of the variation in the methane flux. The global average emissions from hydropower are estimated to be 85 gCO2/kWh and 3 gCH4/kWh, with a multiplicative uncertainty factor of 2. GHG emissions from hydropower can be largely avoided by ceasing to build hydropower plants with high land use per unit of electricity generated.
... The biogenic emission that are generate due to the degradation of biogenic carbon in reservoirs was included. This is produced by oxidation of organic carbon from biomass, organic carbon matter in soil, or sediments [21]. These were estimated using the methodology presented by Hertwich [21] in the Eq. ...
... This is produced by oxidation of organic carbon from biomass, organic carbon matter in soil, or sediments [21]. These were estimated using the methodology presented by Hertwich [21] in the Eq. (1), this model calculates biogenic carbon dioxide and methane emission per 1 kWh. ...
... Where E represents the emission estimated (CO2 or CH4), land use is referring to reservoir flooded area, age is the reservoir lifetime, NPP is the net primary production. Const, BLand use, BAge, and BNPP are constants for CO2 an CH4 described in [21]. The age is 50 years, and land use is 8.67E-4 m 2 calculated for 1 kWh. ...
... The biogenic emission that are generate due to the degradation of biogenic carbon in reservoirs was included. This is produced by oxidation of organic carbon from biomass, organic carbon matter in soil, or sediments [21]. These were estimated using the methodology presented by Hertwich [21] in the Eq. ...
... This is produced by oxidation of organic carbon from biomass, organic carbon matter in soil, or sediments [21]. These were estimated using the methodology presented by Hertwich [21] in the Eq. (1), this model calculates biogenic carbon dioxide and methane emission per 1 kWh. ...
... Where E represents the emission estimated (CO2 or CH4), land use is referring to reservoir flooded area, age is the reservoir lifetime, NPP is the net primary production. Const, BLand use, BAge, and BNPP are constants for CO2 an CH4 described in [21]. The age is 50 years, and land use is 8.67E-4 m 2 calculated for 1 kWh. ...
... carbon dioxide (CO 2 ) and methane (CH 4 ) originated through biogeochemical processes and released to the atmosphere) from HP reservoirs are far higher and more geographically widespread than previously assumed (Deemer et al 2016, Rosentreter et al 2021. Yet, reported C emissions and associated CFs estimates remain uncertain, varying more than four-fold in recent analyses (Hertwich 2013, Scherer and Pfister 2016, Bertassoli et al 2021. The main reasons for this variability are: (i) the large uncertainty associated with the use of multiple approaches to assess hydropower CFs (Kumar et al 2011, Raadal et al 2011; (ii) the lack of more suitable (and standardized) definitions for size categories and limited consideration of potential descriptors of environmental impacts (e.g. ...
... Available quantifications of CFs for hydroelectric energy production are highly variable (Hertwich 2013;figure 5), including values from 0.3 (Raadal et al 2011), to values close to 53 295 gCO 2 e kWh −1 in tropical reservoirs (de Faria et al 2015, Almeida et al 2019a. For small hydroelectric energy production, results are a bit more constrained but still highly variable, ranging from 8 to 17 071 gCO 2 e kWh −1 (Hertwich 2013). ...
... Available quantifications of CFs for hydroelectric energy production are highly variable (Hertwich 2013;figure 5), including values from 0.3 (Raadal et al 2011), to values close to 53 295 gCO 2 e kWh −1 in tropical reservoirs (de Faria et al 2015, Almeida et al 2019a. For small hydroelectric energy production, results are a bit more constrained but still highly variable, ranging from 8 to 17 071 gCO 2 e kWh −1 (Hertwich 2013). Although the size-range and the methodologies used for theses estimations are diverse, to the best of our knowledge, no previous study has reported a negative CF, such as the one observed in SHP 3. CFs based on gross fluxes estimations have been obtained across climatic conditions, pre-impoundment land cover types and hydropower technologies (Kumar et al 2011, Hertwich 2013, Scherer and Pfister 2016. ...
Global assessments evaluating greenhouse gas emissions and climate benefits of hydropower rely on life cycle assessments (LCAs). However, small hydropower plants (i.e., installations with less than 10 MW; SHPs), are largely underrepresented in such schemes, despite their widespread proliferation and well known ecological concerns. Here we quantified, partitioned, and compared the net carbon (C) footprint of four temperate SHPs with different operation designs over a 100-year time horizon. In contrast with previous hydropower LCAs studies, we followed an integrative net C footprint approach accounting for all potential sources and sinks of C within the life cycle of the studied SHPs, including both biogenic and non-biogenic sources, as well as for the pre- and post-impoundment stages involved in the flooding of a reservoir. We found that the areal and system-level C emissions were mostly driven by the residence time of the impounded water, which in turn was linked to the SHP operation type. The power installed in the SHPs did not have a relevant role on the net C fluxes. Accordingly, SHPs with smaller water storage capacity were almost neutral in terms of the C footprint. In contrast, SHPs with water storage facilities prolonged the water residence time in the reservoir and either acted as a source or sink of C. The long water residence time in these SHPs promoted either emission of biogenic gases from the surface or C storage in the sediments. Our work shows that integrative net C footprint assessments accounting for different operation designs are necessary to improve our understanding of the environmental effects of SHPs.
... Over 70 % of global large rivers have been subjected to damming, resulting in extensive disruptions to river networks and altering the flow of carbon and nutrients from land to ocean (Battin et al., 2023;Grill et al., 2019;Maavara et al., 2020). This global trend has led to an increase in the total surface water area, estimated to be nearly 500,000 km 2 , highlighting the significant role of hydropower as a substantial energy resource (Deemer et al., 2016;Hertwich, 2013;Wang et al., 2022a). However, despite its potential for near-continuous energy generation, hydropower has been recognized as a substantial source of greenhouse gas emissions (GHGs) (Cole et al., 2007;Lauerwald et al., 2023). ...
... River-reservoir systems differ from river and lake systems in that the internal carbon transport and transformation are regulated by multiple factors. These factors include the geological background (Li et al., 2015;Pu et al., 2020), HRT (López et al., 2011;Tranvik et al., 2009), variation of water level (Roland et al., 2010;Rosa et al., 2004), thermal stratification intensity , land use (Hertwich, 2013;Li et al., 2018), biological functions (Abril et al., 2005;Tranvik et al., 2009), and differences in global reservoir surface areas used for scaling up local values (Li et al., 2015;Paranaiba et al., 2018). Thus, even after Lauerwald's normalizing of existing estimates by surface areas, considerable uncertainty remains due to complex potential controlling factors. ...
Carbon migration, transformation, and emissions as CO2 in reservoir and lake systems have been extensively studied. However, uncertainties persist regarding carbon cycling variations in both karst and non-karst regions within large thermal stratified river-reservoir systems. To address this knowledge gap, we combined measurements of water chemistry, isotopic compositions (δ13C), partial pressure of CO2 (pCO2), and CO2 fluxes (FCO2) to elucidate the differences, control mechanisms, and environmental effects of various carbon biogeochemical processes in the Hongjiadu reservoir (HJD, karst reservoir) and Shangyoujiang reservoir (SYJ, non-karst reservoir), Yangtze River basin, China. Our results demonstrate that key biogeochemical processes are associated with CO2 production and emissions. The stronger biological carbon pump (BCP) effect in the lentic area of the HJD reservoir limited CO2 emission (0.9 ± 5.0 mmol m−2 d−1) compared to the SYJ reservoir (50.9 ± 33.4 mmol m−2 d−1), leading to low dissolved inorganic carbon (DIC) and high saturation state of carbonate minerals in the lentic epilimnion. Although the released water from both reservoirs acted as hotspots for CO2 emissions, the results of higher Revelle factor (RF) in the HJD reservoir than SYJ reservoir suggest the greater buffer capacity and lower sensitivity of OC degradation changes in DIC. Despite the shorter hydraulic retention time (HRT) of SYJ reservoir (120 d) compared to HJD reservoir (368 d), FCO2 was 3.5 times higher than that of the HJD reservoir (652.9 mmol m−2 d−1). Moreover, upon analyzing selected reservoirs worldwide, it becomes apparent that karst reservoirs demonstrate a reduced potential for CO2 emissions. Our results indicate that the impact of varying geologic settings should be considered to minimize errors in regional and global CO2 emission estimates.
... Notably, the majority of previous studies have been conducted on the river geopotential (RG), while limited information on the river chemical potential (RCP) has been reported (Cui et al., 2011;Zhang et al., 2014;Yang, 2016;Chen et al., 2020;Liu et al., 2022). After the impoundment of HM, the chemical and biological characteristics of reservoir water undergo alterations in various dimensions, leading to changes and destruction of the ecological structure and function of the original river ecosystem (Hertwich, 2013;Fang et al., 2015). Furthermore, the RCP of the reservoir water plays a crucial role in meeting human productive, domestic, and ecological water demand and ensuring the healthy operation of the river-basin ecosystem and the water resources carrying capacity of a region (Wu et al., 2013). ...
... However, the construction of HM leads to the permanent destruction of vegetation, resulting in increased greenhouse gas content and reduced oxygen release. This, in turn, causes local climate change within the reservoir area (Hertwich, 2013;Pang et al., 2015;Chen et al., 2020). This study measures the ecological loss related to climate regulation by assessing the reduction in carbon fixation (sequestration) and oxygen release through photosynthesis in the vegetation ecosystem. ...
The sustainable development of the hydropower megaproject (HM) is one of the critical components of sustainable water resources management. Hence, an accurate assessment of the impacts of social-economic-ecological losses (SEEL) on the sustainability of the HM system is of utmost importance. This study proposes an emergy-based sustainability evaluation model incorporating the social-economic-ecological losses (ESM-SEEL), which integrated the inputs and outputs during HM's construction and operation into an emergy calculation account. The Three Gorges Project (TGP) on the Yangtze River is selected as a case study to comprehensively evaluate the HM's sustainability from 1993 to 2020. Subsequently, the emergy-based indicators of TGP are compared with several hydropower projects in China and worldwide to analyze the multi-impacts of hydropower development. The results showed that the river chemical potential (2.35 E+24sej) and the emergy losses (L) (1.39 E+24sej) are the primary emergy inflow sections (U) of the TGP system, accounting for 51.1% and 30.4% of the U, respectively. The flood control function of the TGP produced tremendous socio-economic benefits (1.24 E+24sej), accounting for 37.8% of the total emergy yield. The resettlement and compensation, water pollution during operation, fish biodiversity loss, and sediment deposition are the main L of the TGP, accounting for 77.8%, 8.4%, 5.6%, and 2.6%, respectively. Based on the enhanced emergy-based indicators, the assessment reveals that the sustainability level of the TGP falls in the middle range compared to other hydropower projects. Thus, along with maximizing the benefits of the HM system, it is necessary to minimize the SEEL of the HM system, which is a critical approach to promote the coordinated development of the hydropower and ecological environment in the Yangtze River basin. This study helps to understand the complex relationship between human and water systems and provides a novel framework that can be used as an evaluation index and insights for hydropower sustainability assessment.
... In addition to "natural" drivers, the widespread regulation of rivers for hydropower energy production exerts additional controls on carbon and GHG fluxes (Silverthorn et al., 2023). The relatively long residence time in reservoirs supports strong metabolic activity which can promote large GHG concentrations depending on nutrients and oxygen availability (Hertwich, 2013;Maavara et al., 2020). As a result, increased dissolved GHG (e.g., CO 2 , CH 4 , and N 2 O) concentrations and evasion fluxes are often observed in the rivers downstream of hydropower reservoirs (Galy-Lacaux et al., 1997;Guérin et al., 2006;Kemenes et al., 2016;Shi et al., 2023;Soued & Prairie, 2020). ...
Carbon dioxide (CO2 ) fluxes in regulated Alpine rivers are driven by multiple biogeochemical and anthropogenic processes, acting on different spatiotemporal scales. We quantified the relative importance of these drivers and their effects on the dynamics of CO2 concentration and atmospheric exchange fluxes in a representative Alpine river segment regulated by a cascading hydropower system with diversion, which includes two residual flow reaches and a reach subject to hydropeaking. We combined instantaneous and time‐resolved water chemistry and hydraulic measurements at different times of the year, and quantified the main CO2 fluxes by calibrating a one‐dimensional transport‐reaction model with measured data. As a novelty compared to previous inverse modeling applications, the model also included carbonate buffering, which contributed significantly to the CO2 budget of the case study. The spatiotemporal distribution and drivers of CO2 fluxes depended on hydropower operations. Along the residual flow reaches, CO2 fluxes were directly affected by the upstream dams only in the first ∼ 2.5 km, where the supply of supersaturated water from the reservoirs was predominant. Downstream of the hydropower diversion outlets, the CO2 fluxes were dominated by systematic sub‐daily fluctuations in CO2 transport and evasion fluxes (“carbopeaking”) driven by hydropeaking. Hydropower operational patterns and regulation approaches in Alpine rivers affect CO2 fluxes and their response to biogeochemical drivers significantly across different temporal scales. Our findings highlight the importance of considering all scales of CO2 variations for accurate quantification and understanding of these impacts, to clarify the role of natural and anthropogenic drivers in global carbon cycling.
... Methane is a potent greenhouse gas, and its emissions increase significantly under these anoxic conditions. Previous studies have indicated that the construction of dams and reservoirs not only disrupts the carbon balance of aquatic ecosystems but also has the potential to contribute to global warming through carbon footprints (Hertwich, 2013;Sun et al., 2016). Dams and reservoirs influence regional carbon balance through the accumulation of organic carbon, biological and chemical transformation mechanisms, and the flow of organic carbon between upstream and downstream areas (Li et al., 2024a). ...
This study focuses on the sources of organic carbon (OC) in surface sediments of reservoirs in the mountainous regions, as well as their dynamics and contribution mechanisms in the carbon cycle. Spatial variations in organic carbon, n‐alkanes, δ¹³C, and δ¹⁵N were analyzed, and a Bayesian isotope mixing model was applied to quantify the relative contributions of different OC sources. The results indicate that the concentration range of organic carbon in sediments is 0.88%–3.72%. The average concentration of long‐chain n‐alkanes is 3.69 μg/g, accounting for 71.4%, indicating that the main source of organic carbon is allochthonous organic carbon. In addition, the Bayesian mixture model results of carbon and nitrogen isotopes also indicate that allochthonous organic carbon is the main contributor. Specifically, sewage (33.1%), C₃ plants (27.1%), and soil organic carbon (19.9%) were identified as the dominant sources. This research highlights the influence of human activities, such as urbanization and agriculture, on OC dynamics and underscores the role of reservoirs in regulating OC transport. The findings provide critical insights into the mechanisms of OC sequestration in agricultural watersheds and offer valuable guidance for water resource management and ecological protection strategies in mountainous environments.
... despite studies showing their important role in carbon budgets both naturally and when modified, can now be remedied with enhanced environmental data collection. This work is vital to inform improved Life Cycle Analysis (LCA), for example when evaluating GHG emissions from infrastructure projects such as hydropower systems (Hertwich, 2013). However, most LCA analyses currently ignore the role of the river itself, or are conducted only local to the development. ...
... No direct pollutant emission during operation, but methane emissions might occur from some reservoirs due to organic matter decomposition 155 . ...
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The energy crisis has highlighted the key role of hydropower in providing grid stability and dispatchable generation. Pumped-Storage Hydropower provides more than 90% of energy storage, and hydropower plants equipped with a reservoir can also provide water&energy storage and multi-purpose services. However, dams in freshwater and coastal water systems can cause environmental damages. As the European rivers are severely fragmented, this has led to impediment of fish migration; therefore, achieving the good status of surface waters requires for mitigation measures to also tackle the adverse impact of hydropower on aquatic environment. Sustainable hydropower needs to achieve a good balance between electricity generation and electricity grid services, impacts on ecosystems and benefits for society, supporting the achievement of the Green Deal targets and the objectives of renewable energy and water/environmental policies.
This report highlights that several sustainable hydropower options exist in the European Union, such as: modernization of the existing hydropower fleet, hydropower integration and hybridization with other energy technologies (floating photovoltaics, heat extraction from generators, batteries), exploiting hidden hydropower in water and wastewater distribution networks, hydropower in existing and non-removable barriers (e.g. water mills) and hydrokinetic turbines. New water&energy storage sustainable solutions are also possible, e.g. new pumped-storage hydropower systems created by interconnecting reservoirs or exploiting abandoned open-pit mines. Digitalisation is also emerging as a relevant strategy to mitigate impacts along rivers and to optimize hydropower generation taking into account weather, technical, market and environmental factors. Multi-purpose reservoirs are a potential solution to grapple with climate changes, increased water demand and ensure flexible energy and storage, but they come also with costs and challenges.
The report shows that the European hydropower sector plays a leading role at the global scale, holding the largest share of export and high-value inventions. The EU is very active in scientific publications, and China is the main competitor. Therefore, hydropower is a key sector to strengthen the competitiveness of the EU in an increasingly challenging world (e.g. energy crisis, climate changes, green and digital transition and the competitiveness of emerging economies). The report also tracks the trend of investments, the main EU funded research projects, and critically discusses some socio-economic and sustainability indicators, comparing them with those of the other clean energy technologies. The challenges, especially the environmental and policy ones, are also discussed in order to stimulate future researches and discussions, and to shade more light on the current state of the art of the technology.
... As shown in Figure 4, other main processes for contributing to the emissions are natural gas production, emissions occuring during the distribution, sweet gas and pipeline infrastructure for natural gas distribution. Meanwhile, the life cycle GHG emissions of hydroelectricity are significantly contributed by biogenic methane and CO 2 which are associated with bacterial processes in reservoirs [14]. Additionally, as illustrated in Figure 5, GHG emissions are also contributed by the construction of hydropower plant, particularly due to the cement used. ...
Electricity generation is a key contributor to global Greenhouse Gases emissions (GHG). The urgent need to mitigate climate change demands a transition to more sustainable ways of electricity generation. However, focusing on operational emissions without assessing their life cycle may lead to less effective decisions on energy policy and technology advancements. This study examines the life cycle of GHG of major electricity generation systems in Malaysia, employing the life cycle assessment approach. The systems are based on energy resources of coal, natural gas, hydro, and solar Photovoltaic (PV). Furthermore, five types of PV systems with different capacity range and module technologies were compared. The present study also compared the scenario of PV installation in capital cities in the country. The results demonstrated that the electricity produced by renewable energy yields substantially lower GHG emissions compared to that generated by fossil fuel energy. Throughout its lifetime, PV and hydroelectricity release GHG emissions at least 5 and 7.4 times, respectively, lower than coal and at least 3.5 and 5.2 times, respectively, lower than natural gas under the worst-case uncertainty scenario. Besides that, the GHG emissions of the PV system installed in the capital city of Malaysia range from 61.4 g to 72.5 g of CO2-eq/kWh. The current study highlights the potential of renewable energy in promoting sustainability within the energy sector, offering a viable pathway towards the decarbonization of the energy sector.
... 30 The biogenic GHG emissions from some hydroelectric reservoirs in tropical areas can reach levels comparable to those of electricity derived from fossil fuels. 30,31 Previous studies found that biogenic GHG emissions for reservoirs in tropical ecosystems can be up to 2100 g CO 2 /kWh, whereas the biogenic GHG emissions for in boreal ecosystems are 12.5 g CO 2 /kWh. 32 Due to the considerable uncertainty in both methods and results for the estimation of biogenic emissions, the presented study for hydroelectricity here does not include reservoir biogenic GHG emissions, which can be addressed in a future study. ...
Recent concerns surrounding climate change and the contribution of fossil fuels to greenhouse gas (GHG) emissions have sparked interest and advancements in renewable energy sources including wind, solar, and hydroelectricity. These energy sources, often referred to as “clean energy”, generate no operational onsite GHG emissions. They also offer the potential for clean hydrogen production through water electrolysis, presenting a viable solution to create an environmentally friendly alternative energy carrier with the potential to decarbonize industrial processes reliant on hydrogen. To conduct a full life cycle analysis, it is crucial to account for the embodied emissions associated with renewable and nuclear power generation plants as they can significantly impact the GHG emissions linked to hydrogen production and its derived products. In this work, we conducted a comprehensive analysis of the embodied emissions associated with solar photovoltaic (PV), wind, hydro, and nuclear electricity. We investigated the implications of including plant-embodied emissions in the overall emission estimates of electrolysis hydrogen production and subsequently on the production of synthetic ammonia, methanol, and Fischer–Tropsch (FT) fuels. Results show that average embodied GHG emissions of solar PV, wind, hydro, and nuclear electricity generation in the United States (U.S.) were estimated to be 37, 9.8, 7.2, and 0.3 g CO2 e/kWh, respectively. Life cycle GHG emissions of electrolytic hydrogen produced from solar PV, wind, and hydroelectricity were estimated as 2.1, 0.6, and 0.4 kg of CO2 e/kg of H2, respectively, in contrast to the zero-emissions often used when the embodied emissions in their construction were excluded. Average life cycle emission estimates (CO2 e/kg) of synthetic ammonia, methanol, and FT-fuel from solar PV electricity are increased by 5.5, 16, and 49 times, respectively, compared to the case when embodied emissions are excluded. This change also depends on the local irradiance for solar power, which can result in a further increase of GHG emissions by 35–41% in areas of low irradiance or reduce GHG emissions by 21–25% in areas with higher irradiance.
... To assess the impact of hydropower generation on GHG emissions are commonly used the carbon intensity or carbon footprint for reservoirs, which depends on net primary production, reservoir age, and the reservoir area. The average carbon intensity of CO 2 and CH 4 emissions from global reservoirs has been estimated to be 85 kg CO 2 /MWh and 3 kg CH 4 /MWh respectively [11]. ...
Although the important positive effects that lakes have ondevelopment at the regional level and beyond, they also have a negativeimpact related to the large amounts of water that they can consume byevaporation. This paper quantifies the effects that one of the largestartificial lakes in Romania (with complex use) has on the environment byestimating the blue water footprint and the carbon footprint. Thus, ananalysis is made of the evolution of the blue water footprint and carbonintensity (calculated for a 100-year life cycle) for 16 years and Pearsoncorrelation coefficients for these indicators are investigated. During the2008-2023 study period, the mean water footprint for the Vidraruhydropower plant was 5.07 m³/GJ and the carbon intensity varies between7.1 to 5.24 gCO2/kWh, with a polynomial trend. Those results are in goodagreement compared with the literature presenting results related to largereservoirs.
... In addition to considerably reducing dam-related GHG emissions, strategic planning of hydropower installations can also reduce impacts on river flow, connectivity, sediment transport, and fish diversity (Flecker et al. 2022). The removal of aboveground and belowground biomass prior to inundation (Table 1, Fig. 1b) is another important measure to decrease the GHG footprint of hydropower plants (Hertwich 2013). Given that the majority of GHG emissions from young reservoirs (<3 years) come from the decomposition of flooded terrestrial biomass after dam establishment, the anticipated removal of the to-be-flooded biomass prevents the emission of large quantities of C and N stored in soil and vegetation. ...
... In addition, a growing body of research has documented the climate effects of reservoir hydropower. As organic matter decays in reservoirs, these artificial water bodies can become non-negligible sources of carbon dioxide and methane 21,22 . The main emissions pathways in reservoirs are methane bubbling, methane and carbon dioxide diffusion, and degassing when water is released from the turbines 23,24 . ...
Around 100 GW of new hydropower projects have been proposed in continental Africa to contribute to meeting future energy demand. Yet, the future expansion of hydropower on the continent faces obstacles due to the impacts of dams on rivers, greenhouse gas emissions from reservoirs and increasingly competitive alternative renewable electricity technologies. Here we propose an integrated approach to include these considerations in energy planning. Compared with planning for least-cost energy systems, capacity expansion strategies balancing environmental and techno-economic objectives increase electricity prices and total discounted costs by at most 1.4% and 0.2%, respectively, while reducing impacts on annual hydropower emissions and river fragmentation by at least 50%. Our results demonstrate that refining techno-economic analysis in light of global and local environmental objectives can help policymakers reduce the river fragmentation and greenhouse gas emissions associated with hydropower development at marginal increases in energy costs.
... Based on 310 observational samples, Li et al. (2018) ) (Tranvik et al., 2018), and slightly higher than the average in other countries (Humborg et al., 2010;Selvam et al., 2014). At the same time, the averaged fCO 2 (28.3 mg m −2 h −1 ) in reservoirs in China also showed higher compared with global temperate reservoirs (13.1 mg m −2 h −1 ) (Hertwich, 2013). It is 2.1 times higher than the global average value (13.8 mg m −2 h −1 ) reported by Deemer et al. (2016) based on a dataset of 262 large reservoirs worldwide. ...
Inland water bodies, being the most active biogeochemical cycle reactors, play a pivotal role in the global carbon cycle and CO2 budget. This study integrates existing observation dataset of CO2 flux (fCO2) in rivers, lakes and reservoirs in China, to elucidate their spatial-temporal patterns and key influencing factors and to reappraise the significance for regional carbon balance. It showed that, the fCO2 in rivers, lakes and reservoirs in China presented significant variability with large range of −379.3–4947.6, −160.1–785.0 and −74.0–1603.1 mg CO2 m−2 h−1, respectively. The median of the fCO2 in rivers was of 228.5 mg CO2 m−2 h−1, observably higher than these in lakes and reservoirs (26.0 and 28.3 mg CO2 m−2 h−1, respectively). The fCO2 in rivers and reservoirs exhibited similar decreasing trend from south to north as a result of universal climate restraint, the averaged fCO2 in Pearl River and Yangtze River basins showed much higher than that in Northeastern rivers. While, the averaged fCO2 in the Mongolia-Xinjiang lake district and the Northeast lake district were higher than other lake districts, followed by the Qinghai-Xizang lake district, and the Eastern and Yungui lake district were generally low, contradicting the climatic restriction. The water primary production enhancement resulting from human activities was the main driver of spatial variation in the fCO2 in lakes. Meanwhile, the fCO2 in rivers presented seasonal pattern with higher wet season than dry season, while opposite patterns were found in lakes and reservoirs. Seasonal temperature, precipitation and water primary production were main factors. Furthermore, it showed pH was a key factor indicating the variability of the fCO2 levels either in rivers, lakes or in reservoirs. In lakes, the fCO2 is closely linked to chlorophyll a (Chl-a) and dissolved oxygen (DO), whereas, the fCO2 in rivers is primarily associated with organic carbon (OC) and total nitrogen (TN), highlighting the diverse controlling mechanisms of fCO2 in various inland water types. In addition, we found that water body sizes play an important role in regulating the fCO2 levels, and small waters act as hotspots of CO2 flux. Additionally, widespread urbanization and agricultural activities may enhance CO2 emissions from rivers but potentially mitigating that from lakes. Nevertheless, the comprehensive impact of these factors on CO2 emissions in inland water requires further evaluation. Based on the extrapolation method, we re-estimated that the total CO2 emission of inland waters in China is approximately 117.3 Tg yr−1, which could offset 4.6%–12.8% of the total land carbon sink in China.
... In addition to "natural" drivers, the widespread regulation of rivers for hydropower energy production exerts additional controls on carbon and GHG fluxes (Silverthorn et al., 2023). The relatively long residence time in reservoirs supports strong metabolic activity which can promote large GHG concentrations depending on nutrients and oxygen availability (Hertwich, 2013;Maavara et al., 2020). As a result, increased dissolved GHG (e.g., CO 2 , CH 4 , and N 2 O) concentrations and evasion fluxes are often observed in the rivers downstream of hydropower reservoirs (Galy-Lacaux et al., 1997;Guérin et al., 2006;Kemenes et al., 2016;Shi et al., 2023;Soued & Prairie, 2020). ...
Carbon dioxide (CO2) fluxes in regulated Alpine rivers are driven by multiple biogeochemical and anthropogenic processes, acting on different spatiotemporal scales. We quantified the relative importance of these drivers and their effects on the dynamics of CO2 concentration and atmospheric exchange fluxes in a representative Alpine river segment regulated by a cascading hydropower system with diversion, which includes two residual flow reaches and a reach subject to hydropeaking. We combined instantaneous and time-resolved water chemistry and hydraulic measurements at different times of the year identifying the main CO2 pathways through a one-dimensional transport-reaction model. The spatiotemporal distribution and drivers of CO2 fluxes depended on hydropower operations. Along the residual flow reaches, CO2 fluxes were directly affected by the upstream dams only in the first 2 km downstream of each dam, where the supply of supersaturated water from the reservoirs was predominant. Downstream of the hydropower diversion outlets, the magnitude and dynamics of CO2 fluxes were dominated by systematic sub-daily peaks in CO2 transport and evasion fluxes (‘carbopeaking’) driven by hydropeaking. The additional input of CO2 released locally into the river at the hydropower diversion outlet during hydropeaking matched the amount of CO2 transported, metabolised, and exchanged with the atmosphere along the whole upstream reach. Hydropower operational patterns and regulation approaches in Alpine rivers significantly affect CO2 fluxes and their response to biogeochemical drivers across different temporal scales. This work contributes to understanding and quantifying these processes to clarify the role of natural and anthropogenic drivers in global carbon cycling.
... Methane (CH 4 ) is the second-most important greenhouse gas (GHG) in the atmosphere after carbon dioxide (CO 2 ), contributing up to 30% of the global greenhouse effect (Hertwich, 2013). Construction of artificial reservoirs has altered land use, making soils saturated by oxygen become anoxic sediments overlain by water, which results in GHG (especially CH 4 ) emission (Xiao et al., 2013a(Xiao et al., , 2013b. ...
Methane (CH4) emissions from reservoir to the atmosphere depend on the balance of microbial CH4 production and oxidation, and temperature is an important factor to both processes by influencing directly the activity of microorganism. Six sediment cores of 30 cm were collected from the Meiziya Reservoir, China, a small water conservancy project with the maximum water depth of 9.7 m. The main input of reservoir was terrigenous organic matter, and the δ¹³C of organic matter in sediments ranged from − 27.5 to − 23.3‰. Using a self-made device for monitoring CH4 production rate, we measured the CH4 production and oxidation rates in sediment cores simultaneously at the range of 6–27 °C with an interval of 3 °C. The CH4 net production rates and oxidation rates in sediment cores varied in the range of (4.2–2489.0) × 10⁻³ µmol/L·h⁻¹ and (16.0–1287.5) × 10⁻³ µmol/L·h⁻¹, respectively. Increasing temperature enhanced the CH4 production and oxidation rates, and the former increased over temperature with an exponential trend. In the Meiziya Reservoir, a large proportion of CH4 (69.7–70.6%) that originated from sediments was depleted before escaping to the surface sediments. During the mineralization of organic matter in sediments, the release of CH4 accounted for 1.1–66.8% of gaseous carbon (calculated by the mass of C).
... Barros et al. (2011) estimated that global hydroelectric reservoirs emit 176 Tg CO 2 / y. In comparison, Hertwich's estimate was higher, at about 278.7 Tg CO 2 /y (Hertwich, 2013), and Li and Zhang (2014) estimated the emissions around 301.3 Tg CO 2 /y. And the reservoir outflow area is an important source of GHGs. ...
... Moreover, the construction phase of PSH projects interferes with "nature" to the same extent as traditional dams (Harby, et al., 2013). Environmental impacts include significant greenhouse gas emissions from construction processes and decaying biota under reservoirs (Fearnside, 2016;Hertwich, 2013;Hite, 2022a;Normyle & Pittock, 2020;Song, et al., 2018). Pumped storage hydropower projects also fragment landscapes, affect species growth and lifecycles, negatively influence water quality and ice cover, and degrade the overall health of ecosystems and biodiversity, among other social and ecological consequences associated with hydropower projects (Harby, et al., 2013, p. 611;WCD, 2000;Wrobleski, et al., 2020; see also Hite, 2022b). ...
The Federal Energy Regulatory Commission (FERC) is well positioned to help advance the United States' clean energy transition through their management of energy projects. One obstacle to achieving the transition is meaningful consultation with Tribal Nations. Following decades of conflict between tribes and FERC regarding infrastructure development, the agency issued a "policy statement on consultation with Indian tribes" in 2003. The Policy acknowledges FERC's trust responsibility to tribes and seeks to work on a "government to government" basis with them, and recent amendments explicitly incorporate treaty rights into FERC's decision-making processes. Despite these interventions, tensions between FERC and tribes continue over the persistent lack of consultation and omission of government-to-government discussions regarding proposed hydropower. In this article, we question the application of FERC's decision-making powers as they intersect with tribal sovereignty via a discourse analysis of 'consultation.' The article applies an ethnographic perspective to explore the 'political' in political ecology and assess FERC's role in licensing the Big Canyon project, a proposed closed-looped pump hydropower project in Navajo Nation in Arizona. The project was proposed in 2020 without adequate consultation with the affected Diné peoples, illuminating significant gaps between FERC's stated policy on consultation and its operationalization. Compounding the situation further, the Big Canyon project would exacerbate human-water relationships by diminishing groundwaters in an area already facing aridification, thereby challenging the health of springs that feed the Little Colorado River, provide habitat for protected species, and are sacred to many Indigenous peoples. Studying the intersection of tribal rights and FERC presents a critical juncture for assessing the underlying power dynamics of decision-making processes regarding pumped storage hydropower in the United States, within the broad context of a clean energy transition.
... Hertwich [32] assessed emissions from the degradation of biogenic carbon in hydropower reservoirs and, after a literature review, estimated life cycle average GHG emissions to be 85 gCO 2eq /kWh. ...
The transformation of the energy sector, based on the development of low-carbon technologies, is essential to achieve climate neutrality. The Life Cycle Assessment (LCA) is a powerful methodology for assessing the environmental impact of energy technologies, which proves to be a useful tool for policy makers. The paper is a review of the main LCA studies of power generation systems performed over the past ten years aiming at comparing the energy technologies to identify those with the lowest impact on the environment, evaluated in terms of gCO2eq/kWh emissions. Screening criteria were established to include only studies of the highest qualitative significance. The authors decided to assign greater weight to emission values reported in more recent studies. For nuclear and renewable energy technologies, most of the emissions are related to the pre-operational phases. Notably, both nuclear and wind technologies, along with other renewable sources throughout their entire life cycle, exhibit significantly lower and less variable emissions compared with conventional gas- and coal-fired technologies.
... Another dam-based hydropower example is the planned Santiago hydropower project of 3,600 MW, located on the Amazon slope (CELEC EP 2015). Based on the evidence of similar case studies, this project will incur disrupting and affecting the water basin, life cycle, structures and functions of terrestrial and aquatic ecosystems (Briones-Hidrovo, Uche, and Martínez-Gracia 2019; Intralawan et al. 2018) and will potentially lead to greenhouse gases emissions, mainly methane (Abril et al. 2005;Demarty and Bastien 2011;Hertwich 2013). ...
... La operación y mantenimiento incluyen emisiones de metano biogénico con un valor de 0.00136 kg/kWh. Las emisiones de metano biogénico en embalses de plantas hidroeléctricas en los trópicos ya han sido descritas (Hertwich, 2013), y provienen tanto de la biomasa inundada en el embalse como de aguas residuales que llegan al embalse. ...
Este documento, coordinado por el Instituto de Investigación y Proyección sobre Ciencia y Tecnología (Incyt), se formula bajo la línea de investigación «Planeamiento, ordenamiento y gestión del territorio». Por ello, tiene como fin contribuir con conceptos, teorías y datos actualizados al análisis de las dinámicas territoriales que inciden en el fenómeno urbano guatemalteco. Las autoras realizan una exhaustiva revisión bibliográfica, complementada con información estadística, bases de datos, informes, resultados de trabajo de campo y planes de desarrollo oficiales. Sus hallazgos sobre el crecimiento urbano en Guatemala (tanto el aumento de población como la expansión del territorio) apuntan a una serie de reflexiones críticas y modelos predictivos de los cambios (de estructura, forma y función de territorios), que buscan propiciar transformaciones ambientales, sociales y económicas que favorezcan a la planificación urbana y la calidad de vida de los habitantes.
... The methodology of LCA is embodied by four analytical stages interlinked to each other. Thisinitiates defining of the goal and scope of theestimation; secondly, the LCIA; thirdly life cycle impact assessment; and finally thelife cycle impact interpretation [ 28,29 ] [ 30,31 ]. This aspect allows a proper sustained frontier definition of LCA, a robust impact assessment, and a dour analysis of inventory. ...
Compared to the increased energy demand in the 21st century, Hydropower (also known as water power) is traditionally considered one of the “Green Energy”. Some advanced researches clarifies that various renewable generations have been performed well to fight back the drastic climate impacts. Though some of them are not as suitable for clean eco-friendly production due to the impacts on eco-system. In recent researches, the Life Cycle Assessment is a great tool to investigate the impact of renewable power plants on eco-system relating upon the whole life cycle based emissions.The Main key function of the paper is to investigate and observe the environmental impacts of the “ITAIPU Hydro-electric Power Plant”, located on the Parana River, between the geographical border area of Brazil and Paraguay”. To identify the environmental impacts CML 2001 have been adapted and the investigation shows that the construction and operation phase has the greater impacts on the eco-system. Through this investigation the identification of environmental hot-spots has been recognized which will help future renewable plant developers to take scientific steps for constructing more environment friendly power plant for sustainable grren electricity production.
... Thus, sustainable hydropower production can only be achieved if, in addition to the positive synergies, biodiversity trade-off risks are considered a fundamental layer in the decision. Hence, neither technical feasibility, electricity price (Gernaat et al. 2017) or greenhouse gas emissions of hydropower electricity production alone (Hertwich 2013) should be the basis for sustainable hydropower development decisions. Compensating entirely for the significant loss of functional habitat due to hydropower would be utopian. ...
Although biodiversity is crucial for Sustainable Development Goals (SDGs), following the current trajectory, we risk failing SDG 15. Using a new indicator quantifying the loss of functional habitat (habitat that is simultaneously suitable and well-connected), we show that the real impact of renewable energy is far larger than previously assumed. Specifically, we estimate that the construction of hydropower reservoirs in south Norway caused a loss of ca. 222 km 2 of functional habitat for wild reindeer (Rangifer tarandus)-which is far larger than assumed based on land inundation indices (110 km 2). Fully mitigating these impacts is challenging: scenario analyses reveal that the measures proposed by societal actors would yield only a fraction of the habitat lost (2-12 km 2) and could cause trade-off risks with other SDGs. Using indices of functional connectivity is crucial for environmental impact assessments, as entire ecological networks for several species can be affected far beyond the reservoirs.
Hydropower is a reliable source of renewable energy that can support the low-carbon energy transition, even though man-made reservoirs can be significant sources of greenhouse gas (GHG) emissions. A multitude of studies have been undertaken to examine the temporal and spatial patterns of GHG emissions from reservoirs, yet no thorough examination of the influence of reservoir hydrological conditions on these emissions has been made. In this study, GHG emissions from hydroelectric reservoirs with varying volumes of water, hydraulic retention times, and power densities were evaluated for a 100-year timescale. GHG emissions from hydropower generation over a 100-year period were significantly lower than those from thermal power generation. Notably, the post-impoundment emission rates averaged 4.27 g CO2 equivalents (CO2eq)/m2 per day, with a net rate of 3.17 g CO2eq/m2 per day. The average post-impoundment emission per unit of electricity generated was 17.22 g CO2eq/kWh, which was lower than the global average of 273 g CO2eq/kWh. Moreover, the emission rates were negatively correlated with volume (post-impoundment, r = – 0.70, p < 0.001; net, r = – 0.33, p = 0.06) and hydraulic retention time (post-impoundment, r = – 0.97, p < 0.001; net, r = – 0.46, p < 0.01). The post-impoundment (r = – 0.81, p < 0.001) and net (r = – 0.62, p < 0.001) emissions per unit of electricity produced exhibited a negative correlation with power density. Reservoirs with higher power densities, shorter hydraulic retention times and smaller capacities were demonstrated to have considerable advantages and potential for the mitigation of GHG emissions due to the their lower emissions of GHG per unit of electricity generated.
This study evaluates the life cycle costs, net present value (NPV), and greenhouse gas (GHG) emissions of three energy scenarios for the Mae Sariang microgrid system to assess the economic and environmental impacts of different energy sources. The reliance on renewable energy has become increasingly vital in addressing energy sustainability and reducing carbon footprints. The analysis reveals that Scenario I, primarily utilizing solar energy, achieved the lowest life cycle cost per kilowatt-hour (kWh) at 6.18 and the highest NPV of 226,583,036 baht, while also producing the fewest GHG emissions at 21,239 kgCO₂e/year. In contrast, Scenario II, dependent on grid electricity, incurred the highest costs and emissions at 25,180 kgCO₂e/year, reflecting its reliance on higher-carbon sources. Scenario III, which incorporates diesel generation, demonstrated moderate emissions at 22,240 kgCO₂e/year but resulted in a negative NPV of -2,690,330 baht due to high fuel expenses. The findings highlight that prioritizing renewable energy sources not only enhances financial viability but also minimizes environmental impact. Therefore, the study concludes that adopting a renewable-focused approach in microgrid systems offers substantial economic and ecological benefits. Policy recommendations include incentivizing renewable energy integration, promoting energy efficiency measures, and developing supportive frameworks to reduce reliance on high-carbon electricity, ultimately enhancing the feasibility and sustainability of energy systems.
Providing and using energy efficiently is hampered by concerns about the environment and the unpredictability of fossil fuel prices and quantities. To address these issues, energy planning is a crucial tool. The aim of the study was to prioritize renewable energy options for use in Mae Sariang’s microgrid using an analytical hierarchy process (AHP) to produce electricity. A prioritization exercise involved the use of questionnaire surveys to involve five expert groups with varying backgrounds in Thailand’s renewable energy sector. We looked at five primary criteria. The following four combinations were suggested: (1) Grid + Battery Energy Storage System (BESS); (2) Grid + BESS + Solar Photovoltaic (PV); (3) Grid + Diesel Generator (DG) + PV; and (4) Grid + DG + Hydro + PV. To meet demand for electricity, each option has the capacity to produce at least 6 MW of power. The findings indicated that production (24.7%) is the most significant criterion, closely followed by economics (24.2%), technology (18.5%), social and environmental (18.1%), and structure (14.5%). Option II is strongly advised in terms of economic and structural criteria, while option I has a considerable advantage in terms of production criteria and the impact on society and the environment. The preferences of options I, IV, and III were ranked, with option II being the most preferred choice out of the four.
This chapter presents a critical analysis of often-used approaches for dealing with uncertainty and sensitivity in life cycle assessment. It will discuss incorrect terminology (e.g., for “parameter” and “confidence interval”), undefined concepts (such as “uncertainty factors”) and the misunderstanding of concepts (like “significant differences” and “significant correlations”).
This chapter will critically analyze the role of the lognormal distribution for characterizing uncertainty in life cycle assessment. It presents the representation and properties, and discusses how authors in the LCA domain have developed unusual interpretations.
This chapter presents the basic elements of descriptive statistics, as far as needed for understanding uncertainty and sensitivity analysis of LCA. We discuss topics such as the mean, the standard deviation, geometric statistics, correlation, and the visualization in terms of, e.g., boxplots and histograms.
More information here: https://setis.ec.europa.eu/hydropower-and-pumped-hydropower-storage-european-union-0_en
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The installed hydro capacity in the EU is 152 GW, contributing to about 12 per cent of the EU’s net electricity generation. Pumped storage and
traditional hydropower reservoirs represent nearly all the EU’s electricity storage capacity and ensure flexibility to the grid. The EU’s pumped storage
turbine capacity is 46 GW. Because hydropower schemes and dams can produce hydrological and morphological alterations, and
adverse impacts on ecosystems, hydropower plays a key role in several EU Directives, including the Water Framework Directive and the
Renewable Energy Directive. Several discussions, and European assessments, have taken place to estimate the potential of various sustainable
hydropower strategies, including powerplant modernization and sustainable refurbishment, hidden opportunities in existing infrastructures
and hydropower hybridization with other energy technologies. This paper discusses hydropower at the EU level, highlighting its complex
role in some EU legislation. The new challenges and opportunities that have emerged from this debate, and their impacts on the EU
economy and on knowledge production (at the scientific, institutional and industrial level), are described.
China is ambitious to develop renewable energy for the commitment of carbon neutralization in 2060. Hydro�power has been regarded as one important solution to mitigate greenhouse gas (GHG) emissions by replacing
fossil fuels, while the related ecological impacts hinder its sustainable development. This study proposes a
framework to integrate life cycle analysis and ecosystem service assessment by evaluating 43 case hydropower
plants (HPs) in China. Combining with the super slacks-based measurement model, the ecological efficiency of
HPs is evaluated to provide optimizing pathways. The results show most environmental impacts of the whole HP
life cycle are from the preparation and construction stages of HPs. The ecosystem service losses (ESLs) are mainly
from the losses of biodiversity and water supply. The first cascade HP generally has a smaller ecological effi�ciency than downstream HPs. Furthermore, the current pricing structure of the studied HPs does not adequately
account for the associated ESLs. It suggests that consumers in transmission destinations should bear a higher cost
to address the ecological impacts of HP operations. Consequently, there is a need to revise the pricing mecha�nisms to reflect and internalize the ecological costs more accurately. Finally, based on the results, policy im�plications for achieving “co-benefit” of hydropower development and ecosystem protection were raised: (a)
conducting the comprehensive and systematic evaluation of HPs including LCA and ESL assessment before HP
planning; (b) ensuring the connectivity of natural flow and the preservation of fish areas; (c) revising the pricing
mechanisms of hydropower based on the fair price.
The European aviation sector must substantially reduce climate impacts to reach net-zero goals. This reduction, however, must not be limited to flight CO2 emissions since such a narrow focus leaves up to 80% of climate impacts unaccounted for. Based on rigorous life-cycle assessment and a time-dependent quantification of non-CO2 climate impacts, here we show that, from a technological standpoint, using electricity-based synthetic jet fuels and compensating climate impacts via direct air carbon capture and storage (DACCS) can enable climate-neutral aviation. However, with a continuous increase in air traffic, synthetic jet fuel produced with electricity from renewables would exert excessive pressure on economic and natural resources. Alternatively, compensating climate impacts of fossil jet fuel via DACCS would require massive CO2 storage volumes and prolong dependence on fossil fuels. Here, we demonstrate that a European climate-neutral aviation will fly if air traffic is reduced to limit the scale of the climate impacts to mitigate.
Carbon capture power plants (CCPPs) can effectively eliminate the carbon-locking effect of coal-fired power generation systems, which constitute one of the essential technical pathways to achieve low-carbon transformation of the power structure. Capable of decoupling CO
2
absorption and separation in terms of time, CCPPs equipped with solvent storage have stronger operational flexibility while promoting the realization of carbon emission reduction targets. Therefore, this study focuses on the generation expansion planning of power systems containing solvent-storaged carbon capture power plants (SSCCPPs). First, a mathematical model is proposed for SSCCPPs considering new operation characteristics of power generation-carbon capture. Second, the per kilowatt-hour carbon emission coefficient (kWh-CEC) of various power plants is analyzed by life cycle assessment (LCA), and a bilateral stepped carbon trading model is established to quantify power plants’ whole life cycle carbon emission effects. Third, a generation expansion planning model considering the internalization of carbon emission effects is developed to explore the benefits of planning SSCCPPs in wind-coal intensive power systems and multi-energy integrated systems. The simulation results on the modified IEEE RTS-96 system and IEEE HRP-38 system have validated the economic and low-carbon performance of planning SSCCPPs in the system.
Improving the operational effectiveness of hydropower systems is becoming more relevant considering the shift to renewable energy sources and the rising social, financial, and environmental costs associated with the construction of new hydropower facilities. This challenge is interdisciplinary as it involves technical, managerial, and institutional aspects. This paper focuses on a technical aspect, more specifically on the relationship between the quality of short-term ensemble streamflow forecasts and the energy produced by a hydropower system. A secondary objective is to measure the contribution of both the meteorological and structural uncertainties on the energy output. To achieve this, a numerical experiment comprising multiple sets of hydrologic ensemble forecasts of different quality and a suite of reservoir optimization models is developed for a case study in Canada (the hydropower system of the Gatineau River basin). These ensemble forecasts are processed by the short-term reservoir operation model in rolling-horizon mode over a planning period of 6 years. Each day, the short-term optimization model seeks to maximize the energy output over the 14-day forecast lead time considering the expected future value of the system derived from a midterm optimization model. The relationship between hydropower generation and common statistical scores characterizing the ensemble forecasts indicates that although there is a link between the quality of the forecasts and the energy production, it is not a one-to-one causal relationship. Our results also show that the diversity of hydrological models is beneficial to the production of energy, indicating that the diversity of model structures compensates the deficiencies of individuals models and adds value to the forecast.
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.
This Intergovernmental Panel on Climate Change Special Report (IPCC-SRREN) assesses the potential role of renewable energy in the mitigation of climate change. It covers the six most important renewable energy sources – bioenergy, solar, geothermal, hydropower, ocean and wind energy – as well as their integration into present and future energy systems. It considers the environmental and social consequences associated with the deployment of these technologies and presents strategies to overcome technical as well as non-technical obstacles to their application and diffusion. SRREN brings a broad spectrum of technology-specific experts together with scientists studying energy systems as a whole. Prepared following strict IPCC procedures, it presents an impartial assessment of the current state of knowledge: it is policy relevant but not policy prescriptive. SRREN is an invaluable assessment of the potential role of renewable energy for the mitigation of climate change for policymakers, the private sector and academic researchers.
Methane (CH4) emissions from the drawdown area of the Three
Gorges Reservoir (TGR) have not been thoroughly investigated even though
the drawdown area encompasses one third of the reservoir surface. In
this study, CH4 emissions from different land uses were
measured in the TGR drawdown area. The average diffusive CH4
emissions were 2.61, 0.19, 0.18, and 0.12 mg CH4
m-2 h-1 in rice paddies, fallow lands, deforested
lands, and croplands, respectively, and were positively related to the
duration of the inundated season among the latter three land uses. On
average the drawdown areas studied here (except rice paddies) were
sources in the inundated season (0.22 ± 0.26 mg CH4
m-2 h-1) and a sink in the drained season (-0.008
± 0.035 mg CH4 m-2 h-1). The
water level was the dominant factor that controlled whether the drawdown
area was either inundated or drained, which in turn determined whether
the drawdown area was a source or sink of CH4 emissions. The
average diffusive CH4 emissions from the fallow lands,
croplands, and deforested lands increased as the distance from the dam
increased from Zigui (0.10 ± 0.15 mg CH4
m-2 h-1) to Wushan (0.15 ± 0.29 mg
CH4 m-2 h-1) to Yunyang (0.24 ±
0.27 mg CH4 m-2 h-1), which could
reflect different sediment characteristics and water velocities. The
total CH4 emission from the drawdown area was estimated to
range from 1033.5 to 1333.9 Mg CH4 yr-1, which
would account for 42-54% of the total CH4 emissions from the
water surface of TGR.
After our previous study about methane (CH4) emissions from
littoral marshes of the Three Gorges Reservoir (TGR), Chinese dams have
raised a world-wide concern. Through measurements from the surface of
the TGR, a CH4 emission rate was recorded as 0.26 ±
0.38 mg CH4 m-2 h-1 (Mean ± SD),
relatively low compared with those from other hydropower reservoirs. We
also recorded CH4 emission rate from the surface of
downstream water, which was also relatively low (0.24 ± 0.37 mg
CH4 m-2 h-1). Such result may indicate
that TGR is not a great CH4 emitter (not "CH4
menace"). One possible reason for such a low emission rate is that
measures to maintain water quality and protect environment and ecosystem
decrease the input of organic materials (for methanogenesis), which in
turn limits the CH4 production in the sediment of the TGR. We
also found that CH4 emission from the flooding drawdown area
(0.29 ± 0.37 mg CH4 m-2 h-1) was
higher than other permanently flooded sites (0.23 ± 0.38 mg
CH4 m-2 h-1). Because of annual
vegetation re-growth, the drawdown zone is the especially important
carbon source for methanogenesis in flooding season. Interestingly, we
also observed that mean CH4 emission was significantly higher
in winter than in spring and summer. This was partly due to seasonal
dynamics of hydrology. In order to estimate the net CH4
emissions caused by the reservoir and reservoir operation, the best
approach would be Life Cycle Analysis.
The export of fluvial carbon from land to the ocean is an important connection between two of the largest carbon reservoirs in the world. Previous investigations have estimated that river water annually provides 0.80–1.33 Pg of carbon to the world's oceans. This investigation combines a review of published data from 80 tropical (30°N–30°S) rivers, with supplementary, unpublished data concerning 95 additional rivers, mostly from South and Southeast Asia. These rivers deliver approximately 0.53 Pg carbon to the estuaries annually. Of this, 0.21 Pg C is dissolved inorganic carbon (DIC), 0.14 Pg C is dissolved organic carbon (DOC), 0.05 Pg C is particulate inorganic carbon (PIC), and 0.13 Pg C is particulate organic carbon (POC). Rivers in the equatorial region between 3°N and 6°S register high DOC values but low DIC values; the difference is primarily associated with type of soil. Rivers in mainland Asia have the highest specific export rates in terms of DIC, DOC and POC.
High resolution multi-annual regional climate model (RegCM3) experiments were performed to simulate the effects of the Three Gorges Reservoir (TGR) on the climate of the surrounding areas. The model was run in double nested mode. Firstly a 50 km resolution simulation was conducted over the China domain driven by the coarse resolution NCEP/NCAR re-analysis. Then the output of the simulation was used to drive the model over the Three Gorges Area (TGA) at a resolution of 10 km. SUB-BATS scheme was employed in the 10 km simulation to represent the land surface at 2 km. Two 10 km simulation, one with and the other without the inland water in TGR were conducted. Comparison of the simulations against observation were firstly carried out to validation the model performances over TGA. The 10 km sensitivity experiments with and without the TGR showed that little or negligible effects can be found except directly over the TGR. Most of the simulated effects are noisy and not statistically significant, except for cooling over the TGR water body in both June–July–August (JJA) and December–January–February (DJF). The cooling leads to an/a insignificant decrease/slight decrease of precipitation over the TGR and nearby grid points, respectively. The cooling is larger in JJA compared to DJF. As a typical river-like reservoir, the width and coverage of the TGR does not have significant influence on the local climate over the area.
Greenhouse gas budgets quantified via land-surface eddy covariance (EC) flux sites differ significantly from those obtained via inverse modeling. A possible reason for the discrepancy between methods may be our gap in quantitative knowledge of methane CH4 fluxes. In this study we carried out EC flux measurements during two intensive campaigns in summer 2008 to quantify methane flux from a hydropower reservoir and link its temporal variability to environmental driving forces: water temperature and pressure changes (atmospheric and due to changes in lake level). Methane fluxes were extremely high and highly variable, but consistently showed gas efflux from the lake when the wind was approaching the EC sensors across the open water, as confirmed by floating chamber flux measurements. The average flux was 3.76 ± 0.39 mug C m-2 s-1 (mean ± SE) with a median of 1.42 mug C m-2 s-1, which is quite high even compared to tropical reservoirs. Fluxes increased exponentially with increasing temperatures, but were decreasing exponentially with increasing atmospheric and/or lake level pressure. A multiple regression using lake surface temperatures (0.1 m depth), temperature at depth (10 m deep in front of the dam), atmospheric pressure, and lake level was able to explain 35.4 % of the overall variance. This best fit included each variable averaged over a 9-h moving window, plus the respective short-term residuals thereof. We estimate that an annual average of 3 % of the particulate organic matter (POM) input via the river is sufficient to sustain these large CH4 fluxes. To compensate the global warming potential associated with the CH4 effluxes from this hydropower reservoir a 1.3 to 3.7 times larger terrestrial area with net carbon dioxide uptake is needed, which indicates the potential relevance of temperate reservoirs and lakes in local and regional greenhouse gas budgets.
Tropical reservoirs upstream from hydroelectric dams are known to release significant amounts of methane to the atmosphere. Here we demonstrate that methane emissions downstream from hydroelectric dams can also be large. Emissions of CH4 downstream of Balbina reservoir in the central Amazon basin (Brazil) were calculated from regular measurements of degassing in the outflow of the turbines and downstream diffusive losses. Annual emissions from the reservoir surface and downstream from the dam were 34 and 39 Gg C, respectively. The downstream emission alone represented the equivalent of 3% of all methane released from central Amazon floodplain.
Hydroelectric reservoirs can release significant quantities of CO2, but very few results are available from the tropics. The objective of the present study was to estimate the emission of CO2 from the Balbina hydroelectric reservoir in the central Brazilian Amazon. Diffusive and ebullitive emissions were estimated at regular intervals, both above and below the dam, using a combination of static chambers and submerged funnels. Gas releases immediately below the dam were calculated as the difference between gas flux at the entrance and the outflow of the hydroelectric turbines. An inundation model derived from a bathymetric map and daily stage readings was used for spatial and temporal interpolation of reservoir emissions. Annual emissions of CO2, upstream and downstream of Balbina dam for 2005, were estimated as 2450 and 81 Gg C, respectively, for a total annual flux of 2531 Gg C. Upstream emissions were predominantly diffusive with only 0.02 Gg C yr-1 resulting from ebullition. On average, 51% of the downstream emission was released by degassing at the turbine outflow, and the remainder was lost by diffusion from the downstream river. The total annual greenhouse gas emission from Balbina dam, including the CO2 equivalent of previously estimated CH4 emissions, was 3 Tg C yr-1, equivalent to approximately 50% of the CO2 emissions derived from the burning of fossil fuels in the Brazilian metropolis of São Paulo.
Concentrations and fluxes of greenhouse gases methane
(CH4), carbon dioxide (CO2), and nitrous oxide
(N2O) were measured during open water conditions in two
hydroelectric reservoirs, Lokka and Porttipahta, in the northern boreal zone in
Finland. These reservoirs were located on peat and forest soils and were built in
1967 and 1970, respectively. Over 20 years after their flooding, the reservoirs were
still largely supersaturated with dissolved CH4 and
CO2. Measured with floating static chambers, the stations in Lokka
released more CH4 (means of 5.3119 mg
m2 d1) during the open
water periods in 1994 and 1995 than the stations in Porttipahta (means of
2.54.8 mg m2 d1),
measured in 1995. The mean CO2 emission rates in Lokka
(21133 mg m2 h1)
and Porttipahta (3695 mg CO2
m2 h1) were more similar.
The chamber measurements could not detect episodic CH4 ebullition
in Lokka Reservoir, indicated by generally higher CH4 fluxes (means
of 2.6660 mg m2
d1) obtained with bubble gas collectors than with the
chambers. The seasonal mean N2O fluxes were generally low, ranging
from 89 to 270 g m2
d1. There was no clear association between the
CH4 emissions and the bottom type, including mineral soils and
old peat deposits. The flooded vegetation, higher nutrient content, and primary
production in the water column rather than old peat could account for the higher
CH4 emissions from the stations in Lokka. This conclusion is
supported by the high content of modern carbon (C) in methane (percent modern C of
92104%) that was extracted from the sediment of Lokka. The results
suggested that if there is a good long-term availability of phosphorus and nitrogen,
the intensive internal C cycle associated with the primary production could maintain
high CH4 and CO2 production for decades, similar
to the situation in eutrophied natural lakes.
Hydroelectric reservoirs cover an area of 3.4× 10 5 km 2 and comprise about 20% of all reservoirs. In addition, they contain large stores of formerly terrestrial organic carbon. Significant amounts of greenhouse gases are emitted, especially in the early years following reservoir creation, but the global extent of these emissions is poorly known. Previous estimates of emissions from all types of reservoir indicate that these human-made systems emit 321Tg of carbon per year (ref.). Here we assess the emissions of carbon dioxide and methane from hydroelectric reservoirs, on the basis of data from 85 globally distributed hydroelectric reservoirs that account for 20% of the global area of these systems. We relate the emissions to reservoir age, location biome, morphometric features and chemical status. We estimate that hydroelectric reservoirs emit about 48TgC as CO 2 and 3TgC as CH 4, corresponding to 4% of global carbon emissions from inland waters. Our estimates are smaller than previous estimates on the basis of more limited data. Carbon emissions are correlated to reservoir age and latitude, with the highest emission rates from the tropical Amazon region. We conclude that future emissions will be highly dependent on the geographic location of new hydroelectric reservoirs.
We present here the first comprehensive assessment of the carbon (C) footprint associated with the creation of a boreal hydroelectric reservoir (Eastmain-1 in northern Québec, Canada). This is the result of a large-scale, interdisciplinary study that spanned over a 7-years period (2003-2009), where we quantified the major C gas (CO2 and CH 4) sources and sinks of the terrestrial and aquatic components of the pre-flood landscape, and also for the reservoir following the impoundment in 2006. The pre-flood landscape was roughly neutral in terms of C, and the balance between pre-and post-flood C sources/sinks indicates that the reservoir was initially (first year post-flood in 2006) a large net source of CO2 (2270 mg C m-2 d-1) but a much smaller source of CH 4 (0.2 mg C m-2 d-1). While net CO2 emissions declined steeply in subsequent years (down to 835 mg C m-2 d-1 in 2009), net CH4 emissions remained constant or increased slightly relative to pre-flood emissions. Our results also suggest that the reservoir will continue to emit carbon gas over the long-term at rates exceeding the carbon footprint of the pre-flood landscape, although the sources of C supporting these emissions have yet to be determined. Extrapolation of these empirical trends over the projected life span (100 years) of the reservoir yields integrated long-term net C emissions per energy generation well below the range of the natural-gas combined-cycle, which is considered the current industry standard.
We explore the role of lakes in carbon cycling and global climate, examine the mechanisms influencing carbon pools and transformations in lakes, and discuss how the metabolism of carbon in the inland waters is likely to change in response to climate. Furthermore, we project changes as global climate change in the abundance and spatial distribution of lakes in the biosphere, and we revise the estimate for the global extent of carbon transformation in inland waters. This synthesis demonstrates that the global annual emissions of carbon dioxide from inland waters to the atmosphere are similar in magnitude to the carbon dioxide uptake by the oceans and that the global burial of organic carbon in inland water sediments exceeds organic carbon sequestration on the ocean floor. The role of inland waters in global carbon cycling and climate forcing may be changed by human activities, including construction of impoundments, which accumulate large amounts of carbon in sediments and emit large amounts of methane to the atmosphere. Methane emissions are also expected from lakes on melting permafrost. The synthesis presented here indicates that (1) inland waters constitute a significant component of the global carbon cycle, (2) their contribution to this cycle has significantly changed as a result of human activities, and (3) they will continue to change in response to future climate change causing decreased as well as increased abundance of lakes as well as increases in the number of aquatic impoundments. © 2009, by the American Society of Limnology and Oceanography, Inc.
We performed a series of gas exchange measurements in 12 diverse aquatic systems to develop the direct relationship between near-surface turbulence and gas transfer velocity. The relationship was log-linear, explained 78% of the variation in instantaneous gas transfer velocities, and was valid over a range of turbulent energy dissipation rates spanning about two orders of magnitude. Unlike wind-based relationships, our model is applicable to systems ranging in size from less than 1 km2 to over 600 km2. Gas fluxes measured with our specific model of floating chambers can be grossly overestimated (by up to 1000%), particularly in low-turbulence conditions. In high-turbulence regimes, flux overestimation decreases to within 50%. Direct measurements of turbulent energy dissipation rate provide reliable estimation of the associated gas transfer velocity even at short temporal and spatial scales.
Emissions from tropical hydropower are often underestimated and can
exceed those of fossil fuel for decades.
Despite its global significance, soil-atmosphere carbon (C) exchange under the impact of soil redistribution remains an unquantified component of the global C budget. Here we use radionuclide and soil organic carbon (SOC) data for two agricultural fields in Europe to undertake a spatial analysis of sediment and SOC fate during erosion and deposition in agricultural uplands. C fluxes induced by soil redistribution are quantified by incorporating C dynamics in a spatially distributed model including both water- and tillage-induced soil redistribution (SPEROS-C). The SOC patterns predicted by SPEROS-C are in good agreement with field observations and show that in upland areas, tillage erosion and deposition exerts a large influence on SOC redistribution and soil profile evolution at a timescale of a few decades. The formation of new SOC at eroding sites and the burial of eroded SOC below plough depth provide an important mechanism for C sequestration on sloping arable land in the order of 3-10 g C m(-2) yr(-1). Any attempt to manage agricultural land to maximize sequestration must fully account for erosion, burial and fate of eroded and buried SOC across the landscape and must also account for the correlation between tillage and erosion.
In a critique of my paper on ‘greenhouse’ gas (GHG) emissions from Amazonian reservoirs (Fearnside 1995), Rosa et al. (1996) suggest that I have reached overly pessimistic conclusions because the reservoirs on which my calculations are based are unrepresentative and because methods based on the Intergovernmental Panel on Climate Change's (IPCC) global warming potentials (GWPs) are unfair for comparing hydroelectric and fossil fuel options. I rush to defend my analysis.
1] Methane (CH 4) and carbon dioxide (CO 2) concentrations and water-air fluxes were measured in three tropical reservoirs and their respective rivers downstream of the dams. From reservoirs, CH 4 and CO 2 flux were in the range of 3 ± 2 and 254 ± 392 mmol.m À2 .d À1 , respectively. Rivers downstream of dams were significantly enriched in CH 4 and CO 2 originating from reservoir hypolimnions. From rivers, CH 4 and CO 2 flux were in the range of 60 ± 38 and 859 ± 400 mmol.m À2 .d À1 , respectively. Despite their relatively small surfaces, rivers downstream of dams accounted for a significant fraction (9– 33% for CH 4 and 7–25% for CO 2) of the emissions across the reservoir surfaces classically taken into account for reservoirs. A significant fraction of CH 4 appeared to degas at the vicinity of the dam (turbines and spillways), although it could not be quantified.
Several studies over the last decade have shown that tropical reservoirs may constitute an appreciable source of methane (CH4) to the atmosphere. Here, we show that the use of low-cost, innovative mitigation and recovery strategies is able not only
to reduce these emissions, but also to transform existing biogenic methane stocks into a renewable energy source. Recovered
gas may be pumped to large consuming centers or stored locally and burned by gas turbines to generate electricity during high-demand
periods, or even purified for transport applications. Our analysis shows that the use of biogenic methane may increase considerably
the energy supply in countries, like Brazil, which possess large tropical reservoirs.
Greenhouse gas emissions from hydroelectric dams are oftenportrayed as nonexistent by the hydropower industry, and havebeen largely ignored in global calculations of emissions fromland-use change. Brazils Tucuru Dam provides an example with important lessons for policy debates on Amazonian development and on how to assess the global warming impact ofdifferent energy options. Tucuru is better from the pointof view of power density, and hence greenhouse gas emissions per unit of electricity, than both the average for existing dams in Amazonia and the planned dams that, if all built, wouldflood 3% of Brazils Amazon forest. Tucurus emission of greenhouse gases in 1990 is equivalent to 7.0–10.1 106 tons of CO2-equivalent carbon, an amount substantially greater than the fossil fuel emission of Brazils biggest city, So Paulo. Emissions need to beproperly weighed in decisions on dam construction. Althoughmany proposed dams in Amazonia are expected to have positivebalances as compared to fossil fuels, substantial emissionsindicated by the present study reduce the benefits often attributed to the planned dams.
Hydroelectric dams in tropical forest areas emit greenhouse gases, as illustrated by the Curuá-Una Dam in the Amazonian portion
of Brazil. Emissions include carbon dioxide from decay of the above-water portions of trees that are left standing in the
reservoir and methane from soft vegetation that decays under anaerobic conditions on the bottom of the reservoir, especially
macrophytes (water weeds) and vegetation that grows in the drawdown zone and is flooded when the reservoir water level rises.
Some methane is released from the reservoir surface through bubbling and diffusion, but larger amounts are released from water
passing through the turbines and spillway. Methane concentration in the water increases with depth, and the turbines and spillway
draw water from sufficient depth to have substantial methane content. In 1990 (13 years after filling), the Curuá-Una Dam
emitted 3.6 times more greenhouse gases than would have been emitted by generating the same amount of electricity from oil.
Because freshwater covers such a small fraction of the Earth’s surface area, inland freshwater ecosystems (particularly lakes,
rivers, and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at
either global or regional scales. By taking published estimates of gas exchange, sediment accumulation, and carbon transport
for a variety of aquatic systems, we have constructed a budget for the role of inland water ecosystems in the global carbon
cycle. Our analysis conservatively estimates that inland waters annually receive, from a combination of background and anthropogenically
altered sources, on the order of 1.9PgCy−1 from the terrestrial landscape, of which about 0.2 is buried in aquatic sediments, at least 0.8 (possibly much more) is returned
to the atmosphere as gas exchange while the remaining 0.9Pgy−1 is delivered to the oceans, roughly equally as inorganic and organic carbon. Thus, roughly twice as much C enters inland
aquatic systems from land as is exported from land to the sea. Over prolonged time net carbon fluxes in aquatic systems tend
to be greater per unit area than in much of the surrounding land. Although their area is small, these freshwater aquatic systems
can affect regional C balances. Further, the inclusion of inland, freshwater ecosystems provides useful insight about the
storage, oxidation and transport of terrestrial C, and may warrant a revision of how the modern net C sink on land is described.
Goal, Scope and BackgroundA consequential life cycle assessment (LCA) is designed to generate information on the consequences of decisions. This paper
includes a comprehensive presentation of the consequential approach to system boundaries, allocation and data selection. It
is based on a text produced within the SETAC-Europe working group on scenarios in LCA. For most of the methodological problems,
we describe ideal methodological solutions as well as simplifications intended to make the method feasible in practice.
MethodWe compile, summarize and refine descriptions of consequential methodology elements that have been presented in separate papers,
in addition to methodological elements and general conclusions that have not previously been published.
Results and ConclusionsA consequential LCA ideally includes activities within and outside the life cycle that are affected by a change within the
life cycle of the product under investigation. In many cases this implies the use of marginal data and that allocation is
typically avoided through system expansion. The model resulting from a consequential life cycle inventory (LCI) also includes
the alternative use of constrained production factors as well as the marginal supply and demand on affected markets. As a
result, the consequential LCI model does not resemble the traditional LCI model, where the main material flows are described
from raw material extraction to waste management. Instead, it is a model of causal relationships originating at the decision
at hand or the decision-maker that the LCI is intended to inform.
Tropical reservoirs have been identified as important methane (CH(4)) sources to the atmosphere, primarily through turbine and downstream degassing. However, the importance of ebullition (gas bubbling) remains unclear. We hypothesized that ebullition is a disproportionately large CH(4) source from reservoirs with dendritic littoral zones because of ebullition hot spots occurring where rivers supply allochthonous organic material. We explored this hypothesis in Lake Kariba (Zambia/Zimbabwe; surface area >5000 km(2)) by surveying ebullition in bays with and without river inputs using an echosounder and traditional surface chambers. The two techniques yielded similar results, and revealed substantially higher fluxes in river deltas (∼10(3) mg CH(4) m(-2) d(-1)) compared to nonriver bays (<100 mg CH(4) m(-2) d(-1)). Hydroacoustic measurements resolved at 5 m intervals showed that flux events varied over several orders of magnitude (up to 10(5) mg CH(4) m(-2) d(-1)), and also identified strong differences in ebullition frequency. Both factors contributed to emission differences between all sites. A CH(4) mass balance for the deepest basin of Lake Kariba indicated that hot spot ebullition was the largest atmospheric emission pathway, suggesting that future greenhouse gas budgets for tropical reservoirs should include a spatially well-resolved analysis of ebullition hot spots.
Inland waters (lakes, reservoirs, streams, and rivers) are often substantial methane (CH4) sources in the terrestrial landscape. They are, however, not yet well integrated in global greenhouse gas (GHG) budgets.
Data from 474 freshwater ecosystems and the most recent global water area estimates indicate that freshwaters emit at least
103 teragrams of CH4 year−1, corresponding to 0.65 petagrams of C as carbon dioxide (CO2) equivalents year−1, offsetting 25% of the estimated land carbon sink. Thus, the continental GHG sink may be considerably overestimated, and
freshwaters need to be recognized as important in the global carbon cycle.
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.
Hydroelectric energy is widely accepted as a clean energy, with almost no impact on greenhouse effect compared to thermal energy production. However, many studies have found that reservoirs were significant emissioivsources of greenhouse gases.-The flooding of forest, soilsrrivers and lakes generated by the creation of reservoir modifies, which influence the greenhouse gases dynamics ofthat new environment. The water-level-fluctuating zone and sediment of the reservoir is the important junction of connecting the exchange of energy and matter, which may be the important areas of greenhouse gases production and releasing. There were many pathways in greenhouse gases emission and the greenhouse gases emission influenced by many factors, and also obviously appeared temporal and spatial differences among reservoirs. To quantify the greenhouse gases emissions from reservoirs, it is necessary to consider each emission pathways of greenhouse gases including diffusive flux, bubbling, degassing and river downstream. Published data from tropical reservoirs indicates that emission of greenhouse gases vary not only among reservoirs, but also within each reservoir, as a function of many aspects, including: season change, wind speed, water temperature, water level, water pH, nitrogen and phosphorus concentrations, the age of reservoir, and oxygen concentration. In this paper, we summarized and discussed the achievements associated with greenhouse gases emission so as to obtain more detail information about the emission of greenhouse gases from reservoirs. Finally, the current insufficient of research on greenhouse gases emission and expecting to provide the reference for the correlative research in future have been analyzed.
Sediment movement during erosion, transport and deposition greatly affects the ecosystem of river basins. However, there is presently no consensus as to whether particular river basins act as carbon dioxide (CO2) sources or sinks related to these processes. This paper introduces a rule‐of‐thumb coordinate system based on sediment delivery ratio (SDR) and soil humin content (SHC) in order to evaluate the net effect of soil erosion, sediment transport and deposition on CO2 flux in river basins. The SDR–SHC system delineates CO2 source and sink areas, and further divides the sink into strong and weak areas according to the world‐average line. The Yellow River Basin, most severely suffering soil erosion in the world, only appears to be a weak erosion‐induced CO2 sink in this system. The average annual CO2 sequestration is ~0·235 Mt from 1960 to 2008, a relatively small value considering its 3·1% contribution to the World's sediment discharge. The temporal analysis shows that the Yellow River Basin was once a source in the 1960s, but changed its role to become a weak sink in the past 40 years due to both anthropogenic and climatic influences. The spatial analysis identifies the middle sub‐basin as the main source region, and the lower as the main sink. For comparison, sediment‐movement‐related CO2 fluxes of eight other major basins in four continents are examined. It is found that the six basins considered in the Northern Hemisphere appear to be sinks, while the other two in the Southern Hemisphere act as sources. Copyright © 2012 John Wiley & Sons, Ltd.
Anthropogenic greenhouse gas (GHG) emissions have substantially contributed to intensification of heavy precipitation and thus the risk of flood occurrence, and this anthropogenic climate change is now likely to continue for many centuries. Thus, precise quantification of human-induced GHG emissions is urgently required for modeling future global warming and precipitation changes, which is strongly linked to flood disasters. Recently, GHG evasion from hydroelectric reservoirs was estimated to be 48 Tg C as CO2 and 3 Tg C as CH4 annually, lower than earlier estimate (published in Nature Geoscience; 2011). Here, we analyzed the uncertainties of GHG emissions from hydroelectric reservoirs, that is, reservoir surface area, data paucity and carbon emission relating to ecological zone, and argued that GHG evasion from global hydroelectric reservoirs has been largely under-estimated. Our study hopes to improve the quantification for future researches.
This paper presents for the first time a Life Cycle Assessment (LCA) study of electricity generation in Mexico. The electricity mix in Mexico is dominated by fossil fuels, which contribute around 79% to the total primary energy; renewable energies contribute 16.5% (hydropower 13.5%, geothermal 3% and wind 0.02%) and the remaining 4.8% is from nuclear power. The LCA results show that 225 TWh of electricity generate about 129 million tonnes of CO2 eq. per year, of which the majority (87%) is due to the combustion of fossil fuels. The renewables and nuclear contribute only 1.1% to the total CO2 eq. Most of the other LCA impacts are also attributed to the fossil fuel options. The results have been compared with values reported for other countries with similar electricity mix, including Italy, Portugal and the UK, showing good agreement.
Purpose The conversion of electricity in Thailand is mainly based on fossil fuels that account more than 90% of electricity generated
in the country. The use of fossil fuels has large environmental impacts, and being largely imported, also affects the energy
security of the country. From the oil shock situation in 1970s, there has been interest in renewable energy in Thailand resulting
in the policy goal for the year 2020 to increase the portion of renewable energy to 20% of energy used in the country. Now,
hydropower contributes a significant portion of the renewable energy in Thailand, and mini-hydropower (run-of-river type with
capacity between 200 to 6000 kW) tends to be most attractive. This is particularly suitable for Thailand, and it is being
applied at several locations. Thus, the overall life cycle assessment (LCA), from cradle to gate, of mini-hydropower plants
needs to be assessed for quantitative evaluation.
Materials and methods There are five mini-hydropower plants in this study. The inputs and outputs of materials and energy used since before construction
stage to demolition stage are inventoried and assessed via LCA using the CML 2001 baseline methodology for impact assessment.
The impact categories considered in this study are global warming (GWP), abiotic depletion (ADP), acidification (ACP), fresh
water aquatic toxicity (FWAP), human toxicology (HTP), photochemical oxidation (POP), and fossil fuel resource depletion (FRP)
potential. The functional unit used is 1 MWh electricity produced from mini-hydropower plants in Thailand, and the life span
of the power plants is 50 years.
Results For each of the environmental impact categories considered, the impact potentials were evaluated for each of the five mini-hydropower
plants; 76.39–151.55 g Sb eq/MWh for ADP, 57.28–116.94 g SO2 eq/MWh for ACP, 11.01–23.01 kg CO2 eq/MWh for GWP, 23.01–52.05 kg 1,4-DB eq/MWh for HTP, 4.58–9.08 kg 1,4-DB eq/MWh for FWAP, 2.93–7.47 g C2H4 eq/MWh for POP, and 35.11–79.13 g Sb eq/MWh for FRP.
Results and discussion The main contributors to the impacts are the huge amount of materials used for construction of the mini-hydropower plant;
sand, gravel, cement, reinforcement steel, pressure pipeline steel, iron, copper, and electric equipment and energy used for
construction activities, construction equipment, and transportation. The remoteness of the mini-hydropower plants and the
requirement of importing electric equipment technology from overseas are significant contributors to the environmental impacts.
Conclusions and perspectives The environmental “hot spots” are construction and transportation stage because of remoteness, huge amount of materials and
energy use in construction period, and the use of imported equipment. Mini-hydropower plants do not only generate power, but
being in hilly regions that are often quite scenic, can serve as public knowledge centers for renewable energy. Thus, the
multiple purposes of mini-hydropower power plants should be utilized in the future. The proper management of environmental
and social issues throughout the project cycle is essential taking into consideration the hydrological cycle and seasonal
variations. Fresh water is a necessary resource for many living things and hence necessary to be managed wisely. These study
results would serve as basic information for decision makers, environmentalists, and all stakeholders and provide a general
picture of environmental impacts from mini-hydropower plants in Thailand.
Representative Life-Cycle Inventories (LCIs) are essential for Life-Cycle Assessments (LCAs) quality and readiness. Because energy is such an important element of LCAs, appropriate LCIs on energy are crucial, and due to the prevalence of hydropower on Brazilian electricity mix, the frequently used LCIs are not representative of the Brazilian conditions. The present study developed a LCI of the Itaipu Hydropower Plant, the major hydropower plant in the world, responsible for producing 23.8% of Brazil's electricity consumption. Focused on the capital investments to construct and operate the dam, the LCI was designed to serve as a database for the LCAs of Brazilian hydroelectricity production. The life-cycle boundaries encompass the construction and operation of the dam, as well as the life-cycles of the most important material and energy consumptions (cement, steel, copper, diesel oil, lubricant oil), as well as construction site operation, emissions from reservoir flooding, material and workers transportation, and earthworks. As a result, besides the presented inventory, it was possible to determine the following processes, and respective environmental burdens as the most important life-cycle hotspots: reservoir filling (CO2 and CH4 emission; land use); steel life-cycle (water and energy consumption; CO, particulates, SOx and NOx emissions); cement life-cycle (water and energy consumption; CO2 and particulate emissions); and operation of civil construction machines (diesel consumption; NOx emissions). Compared with another hydropower studies, the LCI showed magnitude adequacy, with better results than small hydropower, which reveals a scale economy for material and energy exchanges in the case of Itaipu Power Plant.
Inland waters transport and transform substantial amounts of carbon and account for ~18% of global methane emissions. Large reservoirs with higher areal methane release rates than natural waters contribute significantly to freshwater emissions. However, there are millions of small dams worldwide that receive and trap high loads of organic carbon and can therefore potentially emit significant amounts of methane to the atmosphere. We evaluated the effect of damming on methane emissions in a central European impounded river. Direct comparison of riverine and reservoir reaches, where sedimentation in the latter is increased due to trapping by dams, revealed that the reservoir reaches are the major source of methane emissions (~ 0.23 mmol CH4 m(-2) d(-1) vs. ~19.7 mmol CH4 m(-2) d(-1) respectively), and that areal emission rates far exceed previous estimates for temperate reservoirs or rivers. We show that sediment accumulation correlates with methane production and subsequent ebullitive release rates and may therefore be an excellent proxy for estimating methane emissions from small reservoirs. Our results suggest that sedimentation-driven methane emissions from dammed river hotspot sites can potentially increase global freshwater emissions by up to 7%.
Reliable quantitative data on the extent and rates of soil erosion are needed to understand the global significance of soil-erosion induced carbon exchange and to underpin the development of science-based mitigation strategies, but large uncertainties remain. Existing estimates of agricultural soil and soil organic carbon (SOC) erosion are very divergent and span two orders of magnitude. The main objective of this study was to test the assumptions underlying existing assessments and to reduce the uncertainty associated with global estimates of agricultural soil and SOC erosion. We parameterized a simplified erosion model driven by coarse global databases using an empirical database that covers the conterminous USA. The good agreement between our model results and empirical estimates indicate that the approach presented here captures the essence of agricultural erosion at the scales of continents and that it may be used to predict the significance of erosion for the global carbon cycle and its impact on soil functions. We obtained a global soil erosion rate of 10.5 Mg ha-1 y-1 for cropland and 1.7 Mg ha-1 y-1 for pastures. This corresponds to SOC erosion rates of 193 kg C ha-1 y-1 for cropland and 40.4 kg C ha-1 y-1 for eroding pastures and results in a global flux of 20.5 (±10.3) Pg y-1 of soil and 403.5 (±201.8) Tg C y-1. Although it is difficult to accurately assess the uncertainty associated with our estimates of global agricultural erosion, mainly due to the lack of model testing in (sub-)tropical regions, our estimates are significantly lower than former assessments based on the extrapolation of plot experiments or global application of erosion models. Our approach has the potential to quantify the rate and spatial signature of the erosion-induced disturbance at continental and global scales: by linking our model with a global soil profile database, we estimated soil profile modifications induced by agriculture. This showed that erosion-induced changes in topsoil SOC content are significant at a global scale (an average SOC loss of 22% in 50 years) and agricultural soils should therefore be considered as dynamic systems that can change rapidly.
Carbon dioxide (CO2) emissions from biomass combustion are traditionally assumed climate neutral if the bioenergy system is carbon (C) flux neutral, i.e. the CO2 released from biofuel combustion approximately equals the amount of CO2 sequestered in biomass. This convention, widely adopted in life cycle assessment (LCA) studies of bioenergy systems, underestimates the climate impact of bioenergy. Besides CO2 emissions from permanent C losses, CO2 emissions from C flux neutral systems (that is from temporary C losses) also contribute to climate change: before being captured by biomass regrowth, CO2 molecules spend time in the atmosphere and contribute to global warming. In this paper, a method to estimate the climate impact of CO2 emissions from biomass combustion is proposed. Our method uses CO2 impulse response functions (IRF) from C cycle models in the elaboration of atmospheric decay functions for biomass-derived CO2 emissions. Their contributions to global warming are then quantified with a unit-based index, the GWPbio. Since this index is expressed as a function of the rotation period of the biomass, our results can be applied to CO2 emissions from combustion of all the different biomass species, from annual row crops to slower growing boreal forest.
Rural electrification and the provision of low cost, low emission technology in developing countries require decision makers to be well informed on the costs, appropriateness and environmental credentials of all available options. While cost and appropriateness are often shaped by observable local considerations, environmental considerations are increasingly influenced by global concerns which are more difficult to identify and convey to all stakeholders.Life cycle assessment is an iterative process used to analyse a product or system. This study iteratively applies life cycle assessment (LCA) to a 3 kW community hydroelectric system located in Huai Kra Thing (HKT) village in rural Thailand. The cradle to grave analysis models the hydropower scheme’s construction, operation and end of life phases over a period of twenty years and includes all relevant equipment, materials and transportation.The study results in the enumeration of the environmental credentials of the HKT hydropower system and highlights the need to place environmental performance, and LCA itself, in a proper context. In the broadest sense, LCA results for the HKT hydropower system are found to reflect a common trend reported in hydropower LCA literature, namely that smaller hydropower systems have a greater environmentally impact per kWh – perform less well environmentally - than larger systems. Placed within a rural electrification context, however, the HKT hydropower system yields better environmental and financial outcomes than diesel generator and grid connection alternatives.Highlights► We apply life cycle assessment to a 3 kW community hydropower system in rural Thailand. ► The system shows greater environmental impacts per kW h than larger hydropower systems. ► The system has less environmental impacts than diesel or Thai grid alternatives. ► The system has a lower 20yr net present cost than diesel or Thai grid alternatives.
The significance of organic carbon (C) burial in fluvial reservoirs on the global C cycle and atmosphere composition remains debatable. While the entrapment of eroded C in these systems could represent an important C sequestration mechanism, this must be weighed against the emission of greenhouse gases (GHG) that may evolve in anoxic reservoir sediment. Over a 4-year period (2005-2008), dissolved concentrations and fluxes of carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2O) were monitored at a Central Indiana fluvial reservoir (built in 1967) fed by streams draining a predominantly agricultural watershed. Analysis of sediment cores revealed an annual sedimentation rate of 1.6cm and C burial rate of 2.3-2.9MgCha -1. Reservoir waters were supersaturated with CO 2 (mean: 2.55mgCO 2L -1) and CH 4 (9.44μgCO 2L -1). In the sediment, concentrations were 4-250 times higher reaching values up to 14,533μgCH 4L -1. The δ 13C profile of CH 4 (-57.7% at the bottom, -48.26% near the surface) indicated active CH 4 oxidation during diffusive transport through the water column. Instances of N 2O under-saturation were occasionally noted in mid-summers when NO 3- level was <1mgNL -1. Over the study period, GHG emission averaged 2.01gCO 2m -2d -1, 10.49mgCH 4m -2d -1 and 2.01mgN 2Om -2d -1. These means were heavily influenced by the high CH 4 and N 2O fluxes (6 times the average) recorded during a mixing event that was triggered by a large discharge event that followed an extended dry period (discharge: 67% below normal). Based on their global warming potential, diffusive GHG fluxes averaged 2.82gCO 2equivalentsm -2d -1 (range: 2.4-3.36) and completely offset reservoir C burial (2.61gCO 2m -2d -1). These results underscore the sensitivity of the C budget of fluvial reservoirs to major hydrologic events that, through enhancement of GHG fluxes, can easily tip the reservoir C balance from sink to source.
1] The emissions of carbon dioxide (CO 2) and methane (CH 4) from the Petit Saut hydroelectric reservoir (Sinnamary River, French Guiana) to the atmosphere were quantified for 10 years since impounding in 1994. Diffusive emissions from the reservoir surface were computed from direct flux measurements in 1994, 1995, and 2003 and from surface concentrations monitoring. Bubbling emissions, which occur only at water depths lower than 10 m, were interpolated from funnel measurements in 1994, 1997, and 2003. Degassing at the outlet of the dam downstream of the turbines was calculated from the difference in gas concentrations upstream and downstream of the dam and the turbined discharge. Diffusive emissions from the Sinnamary tidal river and estuary were quantified from direct flux measurements in 2003 and concentrations monitoring. Total carbon emissions were 0.37 ± 0.01 Mt yr À1 C (CO 2 emissions, 0.30 ± 0.02; CH 4 emissions, 0.07 ± 0.01) the first 3 years after impounding (1994–1996) and then decreased to 0.12 ± 0.01 Mt yr À1 C (CO 2 , 0.10 ± 0.01; CH 4 , 0.016 ± 0.006) since 2000. On average over the 10 years, 61% of the CO 2 emissions occurred by diffusion from the reservoir surface, 31% from the estuary, 7% by degassing at the outlet of the dam, and a negligible fraction by bubbling. CH 4 diffusion and bubbling from the reservoir surface were predominant (40% and 44%, respectively) only the first year after impounding. Since 1995, degassing at an aerating weir downstream of the turbines has become the major pathway for CH 4 emissions, reaching 70% of the total CH 4 flux. In 2003, river carbon inputs were balanced by carbon outputs to the ocean and were about 3 times lower than the atmospheric flux, which suggests that 10 years after impounding, the flooded terrestrial carbon is still the predominant contributor to the gaseous emissions. In 10 years, about 22% of the 10 Mt C flooded was lost to the atmosphere. Our results confirm the significance of greenhouse gas emissions from tropical reservoir but stress the importance of: (1) considering all the gas pathways upstream and downstream of the dams and (2) taking into account the reservoir age when upscaling emissions rates at the global scale. (2005), Carbon dioxide and methane emissions and the carbon budget of a 10-year old tropical reservoir (Petit Saut, French Guiana), Global Biogeochem. Cycles, 19, GB4007, doi:10.1029/2005GB002457.
1. Dissolved organic carbon (DOC) plays a central role in the dynamics of stream and river ecosystems, affecting processes such as metabolism, the balance between autotrophy and heterotrophy, acidity, nutrient uptake and bioavailability of toxic compounds. However, despite its importance to stream processes, restoration and management activities rarely incorporate DOC as a major management criterion.
2. Lotic DOC pools reflect terrestrial organic carbon accumulation, transfer to the river channel and aquatic processing. In pristine landscapes, characteristics such as topography, climate, and landscape composition are strong predictors of terrestrial accumulation and transfer. Within aquatic systems, the quantity and form of DOC are altered by a variety of processes including primary production, microbial breakdown, sorption to particles and photodegradation.
3. Terrestrial accumulation, transfer and aquatic processing of DOC in agricultural and other human‐dominated landscapes are all subject to substantial change. Consequently, DOC pools in agricultural streams likely differ from historic conditions and now include more labile material and low concentrations of a variety of ubiquitous synthetic organic compounds (e.g. pesticides, antibiotics).
4. Although DOC change in agricultural streams and associated ecological consequences are expected to be widespread, current understanding and relevant data needed to manage affected systems are surprisingly scarce.
5. Wetland and riparian restoration projects have variable effects on fluvial DOC regimes, but management at this intermediate scale is a realistic compromise between the small extent of most restoration projects and the large spatial scale over which organic carbon impairment occurs.
This paper presents a comprehensive overview of the life cycle GHG emissions from wind and hydro power generation, based on relevant published studies. Comparisons with conventional fossil, nuclear and other renewable generation systems are also presented, in order to put the GHG emissions of wind and hydro power in perspective. Studies on GHG emissions from wind and hydro power show large variations in GHG emissions, varying from 0.2 to 152Â g CO2-equivalents per kWÂ h. The main parameters affecting GHG emissions are also discussed in this article, in relation to these variations. The wide ranging results indicate a need for stricter standardised rules and requirements for life-cycle assessments (LCAs), in order to differentiate between variations due to methodological disparities and those due to real differences in performance of the plants. Since LCAs are resource- and time-intensive, development of generic GHG results for each technology could be an alternative to developing specific data for each plant. This would require the definition of typical parameters for each technology, for example a typical capacity factor for wind power. Such generic data would be useful in documenting GHG emissions from electricity generation for electricity trading purposes.
Greenhouse gas (GHG) emissions from reservoirs have been under the microscope for more a decade now. In particular, the high CH4 emissions reported in warm systems have tarnished the green credentials of hydroelectricity in terms of GHG emissions. Reliable estimates of CH4 emissions are crucial, since CH4 has a greenhouse warming potential of 25 and because, unlike CO2, CH4 emissions should be counted for the entire life cycle of a reservoir. Up to now, the highest CH4 emissions from reservoirs have been measured in warm latitudes, thus adding an argument against the use of hydroelectricity in these regions. However, to our knowledge, GHG emissions have been measured for only 18 of the 741 large dams (>10Â MW, according to the ICOLD register) listed in the tropics. This article reviews the limited scientific information available and concludes that, at this time, no global position can be taken regarding the importance and extent of GHG emissions in warm latitudes.
Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) gross fluxes were measured at the air-water interface of 205 aquatic ecosystems in the Canadian boreal region from 1993
to 2003. Fluxes were obtained with a floating chamber connected to an automated NDIR or a FTIR instrument. The results show
a temporary increase in CO2 and CH4 fluxes, followed by a gradual return to values comparable to those observed in natural aquatic ecosystems (lakes, rivers
and estuaries). Mean values for CO2 and CH4 measured in Québec's reservoirs older than 10 years were 1508±1771 mg CO2·m−2·d−1 and 8.8±12 mg CH4·m−2·d−1. Our results showed a strong similarity between lakes, rivers, and old reservoirs across a 5000 km transect from the west
coast to the east cost of Canada. These values are comparable to those observed in Finland or in the sub-tropical semi-arid
western USA. Although several limnological parameters can influence these fluxes, none showed a statistical relationship.
However, levels of CO2 or CH4 fluxes are influenced by pH, wind speed, depth at sampling stations and latitude.
Greenhouse gas (GHG) emissions from hydroelectric dams are often portrayed as nonexistent by the hydropower industry and have
been largely ignored in global comparisons of different sources of electricity. However, the life cycle assessment (LCA) of
any hydroelectric plant shows that GHG emissions occur at different phases of the power plant’s life. This work examines the
role of decommissioning hydroelectric dams in greenhouse gas emissions. Accumulated sediments in reservoirs contain noticeable
levels of carbon, which may be released to the atmosphere upon decommissioning of the dam. The rate of sediment accumulation
and the sediment volume for six of the ten largest United States hydroelectric power plants is surveyed. The amount of sediments
and the respective carbon content at the moment of dam decommissioning (100years after construction) was estimated. The released
carbon is partitioned into CO2 and CH4 emissions and converted to CO2 equivalent emissions using the global warming potential (GWP) method. The global warming effect (GWE) due to dam decommissioning
is normalized to the total electricity produced over the lifetime of each power plant. The estimated GWE of the power plants
range from 128–380g of CO2eq./kWh when 11% of the total available sediment organic carbon (SOC) is mineralized and between 35 and 104g of CO2eq./kWh when 3% of the total SOC is mineralized. Though these values are below emission factors for coal power plants (890g
of CO2eq./kWh), the amount of greenhouse gases emitted by the sediments upon dam decommissioning is a notable amount that should
not be ignored and must be taken into account when considering construction and relicensing of hydroelectric dams.
Methane is the most important greenhouse gas after carbon dioxide, with particular influence on near-term climate change. It poses increasing risk in the future from both direct anthropogenic sources and potential rapid release from the Arctic. A range of mitigation (emissions control) technologies have been developed for anthropogenic sources that can be developed for further application, including to Arctic sources. Significant gaps in understanding remain of the mechanisms, magnitude, and likelihood of rapid methane release from the Arctic. Methane may be released by several pathways, including lakes, wetlands, and oceans, and may be either uniform over large areas or concentrated in patches. Across Arctic sources, bubbles originating in the sediment are the most important mechanism for methane to reach the atmosphere. Most known technologies operate on confined gas streams of 0.1% methane or more, and may be applicable to limited Arctic sources where methane is concentrated in pockets. However, some mitigation strategies developed for rice paddies and agricultural soils are promising for Arctic wetlands and thawing permafrost. Other mitigation strategies specific to the Arctic have been proposed but have yet to be studied. Overall, we identify four avenues of research and development that can serve the dual purposes of addressing current methane sources and potential Arctic sources: (1) methane release detection and quantification, (2) mitigation units for small and remote methane streams, (3) mitigation methods for dilute (<1000 ppm) methane streams, and (4) understanding methanotroph and methanogen ecology.
As the demand for renewable energy increases, it becomes important to critically examine the environmental impacts of renewable energy production. Often, the approach has been trial and error in renewable energy with respect to its impact on the environment. Hydrokinetic Energy Extraction (HEE) has been seen as a potentially “benign” form of renewable hydropower. This paper provides a benchmark for initial measurement of HEE environmental impacts, since negative outcomes have been present with previously assumed “benign” renewable hydropower. A Gorlov system was used to represent a HEE system. Life Cycle Assessment (LCA) was utilized to compare the environmental impacts of HEE with small hydropower, coal, natural gas and nuclear power. Environmental Protection Agency (EPA) criteria air emissions were quantified and compared over the life cycle of the systems. Life cycle air emissions were used in combination with TRACI to compare the systems. The Gorlov system was found to have the lowest life cycle impact with a system lifetime comparison, and did compare closely with small hydropower.
Global NEWS is a global, spatially explicit, multi-element and multi-form model of nutrient exports by rivers. Here we present NEWS 2, the new version of Global NEWS developed as part of a Millennium Ecosystem Assessment scenario implementation from hindcast (1970) to contemporary (2000) and future scenario trajectories (2030 & 2050). We provide a detailed model description and present an overview of enhancements to input datasets, emphasizing an integrated view of nutrient form sub-models and contrasts with previous NEWS models (NEWS 1). An important difference with NEWS 1 is our unified model framework (multi-element, multi-form) that facilitates detailed watershed comparisons regionally and by element or form. NEWS 2 performs approximately as well as NEWS 1 while incorporating previously uncharacterized factors. Although contemporary global river export estimates for dissolved inorganic nitrogen (DIN) and particulates show notable reductions, they are within the range of previous studies; global exports for other nutrient forms are comparable to NEWS 1. NEWS 2 can be used as an effective tool to examine the impact of polices to reduce coastal eutrophication at regional to global scales. Continued enhancements will focus on the incorporation of other forms and sub-basin spatial variability in drivers and retention processes.
This paper presents the findings of gross carbon dioxide and methane emissions measurements in several Brazilian hydro-reservoirs, compared to thermo power generation.The term ‘gross emissions’ means gas flux measurements from the reservoir surface without natural pre-impoundment emissions by natural bodies such as the river channel, seasonal flooding and terrestrial ecosystems. The net emissions result from deducting pre-existing emissions by the reservoir.A power dam emits biogenic gases such as CO2 and CH4. However, studies comparing gas emissions (gross emissions) from the reservoir surface with emissions by thermo-power generation technologies show that the hydro-based option presents better results in most cases analyzed.In this study, measurements were carried in the Miranda, Barra Bonita, Segredo, Três Marias, Xingó, and Samuel and Tucuruí reservoirs, located in two different climatological regimes. Additional data were used here from measurements taken at the Itaipu and Serra da Mesa reservoirs.Comparisons were also made between emissions from hydro-power plants and their thermo-based equivalents. Bearing in mind that the estimated values for hydro-power plants include emissions that are not totally anthropogenic, the hydro-power plants studied generally posted lower emissions than their equivalent thermo-based counterparts.Hydro-power complexes with greater power densities (capacity/area flooded—W/m2), such as Itaipu, Xingó, Segredo and Miranda, have the best performance, well above thermo-power plants using state-of-the-art technology: combined cycle fueled by natural gas, with 50% efficiency.On the other hand, some hydro-power complexes with low-power density perform only slightly better or even worse than their thermo-power counterparts.
Lakes are large sources of methane, held to be responsible for 18% of the radiative forcing, to the atmosphere. Periods of lake overturn (during fall/winter) are short and therefore difficult to capture with field campaigns but potentially one of the most important periods for methane emissions. We studied methane emissions using four different methods, including eddy covariance measurements, floating chambers, anchored funnels, and boundary model calculations. Whereas the first three methods agreed rather well, boundary model estimates were 5-30 times lower leading to a strong underestimation of methane fluxes from aquatic systems. These results show the importance of ebullition as the most important flux pathway and the need for continuous measurements with a large footprint covering also shallow parts of lakes. Although fluxes were high, on average 4 mmol m(-2) d(-1) during the overturn period, water column microbial methane oxidation removed 75% of the methane and only 25% of potential emissions were released to the atmosphere. Hence, this study illustrates second the importance of considering methane oxidation when estimating the flux of methane from lakes during overturn periods.
Gross CO2 and CH4 emissions (degassing and diffusion from the reservoir) and the carbon balance were assessed in 2009-2010 in two Southeast Asian sub-tropical reservoirs: the Nam Ngum and Nam Leuk Reservoirs (Lao PDR). These two reservoirs are within the same climatic area but differ mainly in age, size, residence time and initial biomass stock. The Nam Leuk Reservoir was impounded in 1999 after partial vegetation clearance and burning. However, GHG emissions are still significant 10 years after impoundment. CH4 diffusive flux ranged from 0.8 (January 2010) to 11.9 mmol m(-2) d(-1) (April 2009) and CO2 diffusive flux ranged from -10.6 (October 2009) to 38.2 mmol m(-2) d(-1) (April 2009). These values are comparable to other tropical reservoirs. Moreover, degassing fluxes at the outlet of the powerhouse downstream of the turbines were very low. The tentative annual carbon balance calculation indicates that this reservoir was a carbon source with an annual carbon export (atmosphere+downstream river) of about 2.2±1.0 GgC yr(-1). The Nam Ngum Reservoir was impounded in 1971 without any significant biomass removal. Diffusive and degassing CO2 and CH4 fluxes were lower than for other tropical reservoirs. Particularly, CO2 diffusive fluxes were always negative with values ranging from -21.2 (April 2009) to -2.7 mmol m(-2) d(-1) (January 2010). CH4 diffusive flux ranged from 0.1 (October 2009) to 0.6 mmol m(-2) d(-1) (April 2009) and no degassing downstream of the turbines was measured. As a consequence of these low values, the reservoir was a carbon sink with an estimated annual uptake of - 53±35 GgC yr(-1).