Estimation of greenhouse gas (GHG) emission from wastewater treatment plants and effect of biogas reuse on GHG mitigation

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.

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

Domestic wastewater management in Greece: Greenhouse gas emissions estimation at country scale

Impact of process design on greenhouse gas (GHG) generation by wastewater treatment plants

Greenhouse gases (GHGs) emissions have been increasing, recently. One of the greenhouse gas emission resources is the anaerobic wastewater treatment process. The up flow anaerobic sludge bed (UASB) reactor is the anaerobic treatment unit located in a dairy wastewater treatment plant (WWTP) in Turkey. Greenhouse gases (GHGs) emission emits from the anaerobic reactor due to the biogas generation. In this study, the on-site greenhouse gas emissions from the anaerobic reactor with and without biogas recovery were estimated from biogas amount and content using a developed model based on IPCC approach. Then, the off-site GHGs emissions were estimated from electricity consumption and chemical use. The biogas recovery reduced the greenhouse gas emissions. The highest reduction of the on-site GHGs emissions was 97%. Chemical use was the major source of the off-site GHGs emissions in this study. The main emission resource was chemical consumption for a UASB reactor located in a dairy WWTP.

Options to reduce greenhouse gas emissions during wastewater treatment for agricultural use

It is urgent for the wastewater treatment sector to respond to global climate change. Although studies related to the water–energy–carbon (WEC) nexus have been widely conducted, the application of the coupling coordination indicator is still limited in the wastewater treatment sector. This study fills such a research gap by linking water footprint (WF), energy footprint (EF), and carbon footprint (CF) together and testing these indicators in 140 wastewater treatment plants (WWTPs) in Shandong province, China. Both the EF and CF of these WWTPs were calculated by conducting hybrid life cycle assessments, while WF was calculated by using a WF method. The results show that gray WF generated from 1 m3 of wastewater ranged from 9.58 to 12.90 m3, while EF generated from 1 m3 of wastewater ranged from 9.42 × 10−2 to 0.22 kg oil eq and CF generated from 1 m3 of wastewater ranged from 0.58 to 1.27 kg CO2 eq. Also, the total WF, EF, and CF of these WWTPs in Shandong were 4.26 × 1010 m3, 5.32 × 108 kg oil, and 3.35 × 109 CO2 eq in 2021, respectively. Key factors contributing to the overall greenhouse gas (GHG) emissions were the on-site GHG emissions and off-site electricity-based GHG emissions. Meanwhile, total nitrogen was the dominant contributor to the gray WF. In addition, the coupling coordination indicators of WF, EF, and CF ranged from 0.7571 to 0.9293. Finally, this study proposed several policy recommendations to improve the overall sustainability of this wastewater treatment sector by considering local realities, including adopting multi-dimensional indicators, decarbonizing current electricity grids, promoting the utilization of renewable energy, and initiating various capacity building efforts.

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

Greenhouse gas emissions and net carbon sequestration of the Beijing-Tianjin Sand Source Control Project in China

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).

The process of removing organic components from wastewater as BOD5 through wastewater treatment plants has been proven to be a significant source of greenhouse gas emissions, mainly methane CH4, carbon dioxide CO2 and nitrous oxide N2O. The reduction of these emissions has attracted more interest given their major contribution to global warming. This study was able to identify and estimate the amount of methane and CO2 emissions on a monthly basis by a simple modeling approach and an empirical method (IPCC) for N2O emissions, in the case of Ain-Taoujdate wastewater treatment plant, throughout the years 2013, 2018 and 2019. The results showed that anaerobic ponds were the main source of on-site emissions with 66% of total contribution and 33% for facultative ponds, followed by the energy consumption of the pumping station as off-site GHG emissions.

The factor required for estimating greenhouse gas emission, i.e. the fossil carbon fraction, excludes the biomass fraction of incinerated waste and can be applied as a major factor in estimating greenhouse gas emissions. In Korea, the amount of greenhouse gases emitted from waste incineration facilities is calculated by using a solid waste incinerated amount default values (biomass fraction, content of dry matter, etc.) provided by the Intergovernmental Panel on Climate Chang (IPCC). However, this method cannot reflect the characteristics of Korea. This method is likely to overestimate or underestimate the amount of greenhouse gas emissions. This study aims to investigate the difference in emissions between the actual values of the biomass content based on the exhaust gas standard and the IPCC defaults applied in the calculation of the national emissions. The comparative result indicates that the amount of greenhouse gas emissions calculated using the solid waste composition method is 70.71 tons CO2/day and using the flue gas analysis is 56.92 tons CO2/day. This verifies that the former method overestimates the amount of greenhouse gas emissions compared with the latter method. The difference is caused by applying both factors in estimating greenhouse gas emissions and the basic values provided in the IPCC guideline. In addition, although the IPCC reported 10% of biomass content, it is 41.06% as a result of actual analysis, and hence, it is considered that there will be a difference depending on the biomass content. Thus, to increase the reliability of the calculated greenhouse gas emissions, these should be estimated by considering national characteristics.

One of the greenhouse gas (GHG) emission resources is industrial wastewater treatment plants. In this study, on-site and off-site greenhouse gas emissions of an extended aeration activated sludge process in a meat processing wastewater treatment plant were estimated using a new developed approach based on the IPCC method. On-site emissions were regarded as the emissions related to the biochemical treatment process and microbial activity in the wastewater. On-site emissions were estimated from organic materials removal from wastewater and microbial mass activity. Biological oxygen demand (BOD) and chemical oxygen demand (COD) removal were considered as pollutant resources of carbon dioxide (CO2) and methane (CH4), respectively. Off-site emission was estimated from electricity consumption, chemical use and the sludge stabilization process. This paper aimed to determine and reduce on-site and off-site emissions for the extended aeration process in an industrial wastewater treatment plant. Modification of operating conditions was applied to reduce GHG emissions. The results revealed that electricity consumption was the major source of the greenhouse gas emissions for this process with a value of 6,002.77 kg CO2e/d. The minimization of total GHG emissions reached up to 17.1% by modifying the treatment process conditions.

Estimation of greenhouse gas emissions from a hybrid wastewater treatment plant

Global warming and the greenhouse effect are two of the most important environmental problems. Carbon dioxide, methane, and nitrous oxide emissions are the main greenhouse gas emissions in wastewater treatment plants. In this study, the greenhouse gas emission sources in a wastewater treatment plant were determined. Direct (from fossil fuel combustion, methane emissions, and process emissions of the other greenhouse gases) and indirect emissions (primarily from electricity use) in the plant were monitored. The optimum influent characteristics and operating conditions have been defined by using Monte Carlo simulation to minimize the emissions. The results revealed that the highest direct greenhouse gas emission was observed in August with the value of 23.328 kg CO2‐eq d–1 and the lowest emission was 7.56 kg CO2‐eq d–1 measured in January. The aeration tank is a major source of greenhouse gas emissions. Indirect emission has occurred because of the anaerobic digester but the biogas has been cogenerated in the plant, so it has been ignored for the calculation. According to the simulation study, if the plant is operated under optimum operating conditions, it can emit the lowest amount of greenhouse gas emissions. The optimum removal values required for the minimum greenhouse gas emissions are 79% for chemical oxygen demand, 75% for biochemical oxygen demand, and 82% for total suspended solid. The optimum operating conditions for the aeration tank, which is the major source of emission, are 5.33 h of hydraulic retention time, 0.215 d of solid retention time, and 0.999 for food/microorganisms. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.