Estimating greenhouse gas emissions from Iran's domestic wastewater sector and modeling the emission scenarios by 2030

Understanding the greenhouse gas emissions from China’s wastewater treatment plants: Based on life cycle assessment coupled with statistical data

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

Industrial activities are one of the most important emission sources of greenhouse gases at a global level. The process of production, transportation, electricity consumption, and industrial wastewater are the four major components in producing greenhouse gases. Industrial wastewater management (collection, treatment, and disposal) results in direct emission of greenhouse gases (including carbon dioxide, methane, and nitrous oxide). Also, energy consumption in the wastewater treatment process causes indirect carbon dioxide emissions. The present study aimed to estimate the contribution of industrial wastewater treatment plants in Iran from this emission, in addition to identifying sources of greenhouse gas emissions in the industrial wastewater treatment plant and estimating greenhouse gas emissions from the industrial wastewater sector in Iran. In this research, the emission calculations were conducted by using the methodology of Intergovernmental Panel on Climate Change (IPCC) guidelines for calculating greenhouse gases emission. Based on the estimations performed in this study, 1,305.98 kt of CH4 were emitted directly from wastewater in 2017 in the entire industrial wastewater sector. Further, the results indicated that industrial wastewater treatment plants in Iran’s industrial parks generate 46.53 kt of CH4 directly and 259.5 kt of CO2 indirectly. According to the studies, the food industry, especially the industries involved in processing agricultural products (with 48.74 % of total methane emissions) has the highest greenhouse gas emissions in the country, followed by the paper production industry (with 27.46 % of total methane emissions) in the second place. One of the best strategies for reducing greenhouse gas emissions in industrial wastewater treatment plants is energy production from methane produced in large treatment plants and implementing necessary amendments in production processes to decrease wastewater production.

Greenhouse gas (GHG) emission and energy consumption in wastewater treatment plants (WWTPs) of the pulp and paper industry were modeled and estimated. Aerobic, anaerobic, and hybrid biological processes were used for the removal of contaminants. In addition to the removal of carbonaceous compounds, anaerobic digestion of the produced sludge and the removal of excess nitrogen in the effluent of treatment plants by nitrification/denitrification processes were incorporated in the model. Carbon dioxide, methane, and nitrous oxide were the major GHGs generated during the biological treatment, combustion, energy generation, and transportation. The generated biogas from the anaerobic processes was assumed to be recovered and used as a source of energy for the treatment plant, in an effort to reduce GHG emissions while decreasing the total energy needs of the WWTP. The established kinetic relationships of wastewater treatment processes along with mass and energy balances were employed for the simulation of different treatment systems and estimation of GHG emissions. Various sources of GHG emission were divided into on-site and off-site sources to simplify the modeling and simulation procedure. The overall GHG generation in the presence of biogas recovery was equal to 1.576, 3.026, and 3.271kg CO2-equivalent/kg BOD by the three examined systems. The energy produced by the recovery and combustion of biogas could exceed the energy demands of all different treatment plants examined in this study and reduce off-site GHG emission. The generation of GHGs from aerobic and hybrid processes increased by 27% and 33.2%, respectively, when N2O emission from nitrogen removal processes was taken into consideration.

Insight into greenhouse gases emissions from the two popular treatment technologies in municipal wastewater treatment processes

Accuracy in national greenhouse gas (GHG) emissions estimation is a key element for outlining best strategies to reduce GHG emissions from various source sectors of the economy. In this study, an initial attempt has been made to estimate GHG emissions from waste sector in Rawal Town - an urban city of Rawalpindi district in Pakistan. Tier 1 approach of Revised 1996 Intergovernmental Panel on Climate Change (IPCC) Guidelines and the best available primary activity data collected for the study area were applied for the fiscal year June 2014-May 2015. Emissions of three GHGs - carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) under three waste management practices i.e. solid waste disposal sites, wastewater handling, and waste incineration were assessed. Out of the total 417.84 Gg CO2 equivalent emissions, the share of each gas (CH4, CO2 and N2O) in total emissions was found as 11.31, 0.53, and 0.58 Gg respectively. Solid waste disposal sites are identified as the largest source of CH4 emissions (10.73 Gg). To make the country's GHG emissions estimates more robust for waste sector, such type of local area based studies established on primary activity data could be advantageous for reducing uncertainties in national emission estimates.

This study aims to determine the effect of greenhouse gas (GHG) emissions on economic performance in terms of energy costs for an industrial wastewater treatment plant. Also, the mitigation of GHG emissions aimed at using process modification to obtain possible reductions in energy costs. Optimum energy consumptions were reported for the minimum GHG emission using the Data Envelopment Analysis (DEA) and Monte Carlo simulation model. In this paper, a new empirical approach has been developed depending on the GHG emissions for estimating the economic performance of the wastewater treatment plants. The results revealed that nitrous oxide (N2O) emissions led to the highest energy costs among direct emissions. In the second stage of the study, the effects of design conditions on GHG emissions and energy costs were investigated. If the aeration tank is operated at 24 h of hydraulic retention time (HRT) and 22 days of solid retention time (SRT), then, on average, 27, 27.9, and 30.7% of reduction in energy costs in terms of direct carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions, respectively, is observed in the plant. These reductions corresponded to approximately 17.33 €/kWh of cost-saving in this plant.

Simple SummaryLivestock manure management is one of the main sources of greenhouse gas (GHG) emissions in South Africa producing mainly methane and nitrous oxide. The emissions from this sub-category are dependent on how manure is stored. Liquid-stored manure predominantly produces methane while dry-based manure enhances mainly production of nitrous oxide. Intergovernmental Panel on Climate Change (IPCC) guidelines were utilized at different tier levels in estimating GHG emissions from manure management. The results show that methane emissions are relatively higher than nitrous oxide emissions with 3104 Gg and 2272 Gg respectively in carbon dioxide global warming equivalent.Manure management in livestock makes a significant contribution towards greenhouse gas emissions in the Agriculture; Forestry and Other Land Use category in South Africa. Methane and nitrous oxide emissions are prevalent in contrasting manure management systems; promoting anaerobic and aerobic conditions respectively. In this paper; both Tier 1 and modified Tier 2 approaches of the IPCC guidelines are utilized to estimate the emissions from South African livestock manure management. Activity data (animal population, animal weights, manure management systems, etc.) were sourced from various resources for estimation of both emissions factors and emissions of methane and nitrous oxide. The results show relatively high methane emissions factors from manure management for mature female dairy cattle (40.98 kg/year/animal), sows (25.23 kg/year/animal) and boars (25.23 kg/year/animal). Hence, contributions for pig farming and dairy cattle are the highest at 54.50 Gg and 32.01 Gg respectively, with total emissions of 134.97 Gg (3104 Gg CO2 Equivalent). Total nitrous oxide emissions are estimated at 7.10 Gg (2272 Gg CO2 Equivalent) and the three main contributors are commercial beef cattle; poultry and small-scale beef farming at 1.80 Gg; 1.72 Gg and 1.69 Gg respectively. Mitigation options from manure management must be taken with care due to divergent conducive requirements of methane and nitrous oxide emissions requirements.

Wastewater treatment plants (WWTPs) using membrane bioreactor (MBR) technology have been considered a significant source of greenhouse gas (GHG) emissions. This study chose a small-scale wastewater treatment plant using MBR technology to estimate its potential for GHG emissions. The total GHG emissions from this wastewater treatment plant ranged from 2,802 to 11,946kg CO2 -eq/month within the 4-year study period, and they were mainly attributable to electricity consumption (79.94%) followed by chemical usages (17.13%) and on-site GHG emissions (2.93%). The on-site GHG emissions varied monthly, but most of them ranged from 80 to 160kg CO2 -eq/month. The aeration tank was an important operating unit for GHG emissions. Off-site GHG emissions mainly came from carbon dioxide (CO2 ) emissions resulting from electricity consumption. The results of this study provide useful information about the potential of GHG emissions from WWTPs using MBR technology and indicate that WWTPs can be sustainably managed. PRACTITIONER POINTS: Wastewater treatment plants have been considered a source of greenhouse gas emissions. Total greenhouse gas emissions from the wastewater treatment plants using membrane bioreactor were mainly attributable to electricity consumption. On-site greenhouse gas emissions were relatively insignificant in this study.

Wastewater treatment systems contribute significantly to anthropogenic greenhouse gas emissions. The main greenhouse gases emitted during the wastewater treatment processes are methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2). Sequential batch reactor (SBR) is a type of an activated sludge process, and due to its high efficiency, currently, this is the preferred technology for the construction of new wastewater treatment plants (WWTPs). This study presents the estimation of greenhouse gas (GHG) emissions from SBR domestic wastewater treatment plants in Navi Mumbai, Maharashtra. We estimated direct emissions from wastewater treatment processes as well as indirect emissions due to energy usage during the treatment process. A total emission of ~35 kt CO2-eq/year was estimated for six SBR-based WWTPs having combined treatment capacity of 474 MLD. All except one of these plants were well managed. In the case of not so well-managed SBR plants, significant methane production occurs during the treatment process. In the long run, if these plants are not well managed, the emission could increase by three to fourfolds for the same treatment capacity. In either case, major GHG emissions are due to CH4 emission during the treatment process. The contribution of N2O is negligible towards total GHG emissions.

Wastewater collection systems (WCSs) not only play an indispensable role in urban life but also significantly contribute to greenhouse gas (GHG) emissions. Based on extensive literature research, this study (1) summarizes current research on the production mechanisms, influencing factors, control techniques, and quantitative estimates of GHGs emitted from WCSs and (2) presents initial estimates of total GHG emissions from WCSs in China. A variety of factors affect GHG production, but standard methods are still lacking to quantify GHG emissions from WCSs. China’s WCSs emit approximately 3.86–15.35 Mt of CO2eq annually (equivalent to 5.1–20.2% of the GHG emissions from wastewater treatment). Thus, GHG emissions from WCSs are significant and deserve attention. Control of GHGs in WCSs can be achieved through the application of chemical agents, while the construction of a green stormwater infrastructure can further facilitate GHG reductions. This review provides valuable insights for policymakers to consider in future policy planning related to GHG reduction and the improved operation of WCSs. Future research should focus on quantifying the impacts of various factors and accumulating field data on GHGs in various regions to facilitate the development of standardized calculation methods.

Carbon footprint analysis is a method to quantify the life cycle Greenhouse Gases (GHGs) emissions and identify the measure to reduce climate change impacts. The Intergovernmental Panel on Climate Change (IPCC) has identified that the global warming and climate change which is one of the most important issues in the domain of environment are caused by the excessive emission of Greenhouse Gases (GHG) mainly constituting Carbon dioxide (CO2), Methane (CH4) and Nitrous oxide (N2O). The municipal wastewater treatment plant receives wastewater for treatment and finally discharges the treated effluent. The emissions of GHG during the treatment of wastewater as well as during the treatment process of sludge and also for energy generation are known to be on-site GHG emissions. Off-site GHG emissions are generated due to transportation and disposal of sludge, off-site energy and chemical production. In Puducherry, the municipal wastewater is being treated using oxidation ponds, Upflow Anaerobic Sludge Blanket (UASB) and Sequencing Batch Reactor (SBR). Wastewater treatment using Sequencing Batch Reactor (SBR) technology is one of the state-of-the art wastewater management systems. In this technology equalization, biological treatment and secondary clarification are performed in a single reactor in a time control sequence. The emissions of GHG from the Oxidation ponds of 12.5 MLD, UASB reactor of 2.5 MLD and SBR of 17 MLD were assessed based on the IPCC guidelines and the total emissions of GHG in terms of equivalent of CO2 were compared. The performance of the SBR is more efficient and the emissions of GHG are less than the emissions in the UASB as well as in oxidation ponds. The emission of GHG in SBR is about 60% of the existing treatment systems of oxidation ponds and UASB thus a reduction of 40% GHG emission could be achieved.

Blue revolution for food security under carbon neutrality: A case from the water-saving and drought-resistance rice

The increasing attention paid to the environment has led to a reduction in the emissions from wastewater treatment plants (WWTPs). Moreover, the increasing interest in the greenhouse gas (GHG) emissions from WWTPs suggests that we reconsider the traditional tools used for designing and managing WWTPs. Indeed, nitrous oxide, carbon dioxide and methane can be emitted from wastewater treatment, significantly contributing to the greenhouse gas (GHG) footprint. The reduction of energy consumption as well as GHG emission are of particular concern for large WWTPs which treat the majority of wastewater in terms of both volume and pollution load. Nowadays, there is an increasing need to develop new tools that include additional performance indicators related to GHG emissions and energy consumption as well as traditional effluent quality parameters. Energy consumption, in fact, can be considered as an indirect source of GHGs. This paper presents the development of an ongoing research project aiming at setting-up an innovative mathematical model platform for the design and management of WWTPs. The final goal of the project by means of this platform is to minimize the environmental impact of WWTPs through their optimization in terms of energy consumptions and emissions, which can be regarded as discharged pollutants, sludge and GHGs.

Greenhouse gas emission by centralized wastewater treatment plants in Chinese industrial parks: Inventory and mitigation measures