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Abstract Agriculture contributes to a significant proportion of global emissions of greenhouse gases (GHG) but can also participate in climate change mitigation. The introduction of legumes in crop rotations reduces the dependence on N fertilizers and may mitigate the carbon (C) footprint of cropping systems. The aim of this study was to quantify the C footprint of six low-input arable cropping systems resulting from the combination of three levels of grain legumes introduction in a 3-yr rotation (GL0: no grain legumes, GL1: 1 grain legume, GL2: 2 grain legumes) and the use of cover crops (CC) or bare fallow (BF) between cash crops, covering two rotation cycles (6 years). The approach considered external emissions, on-site emissions and soil organic carbon (SOC) stock changes, and prioritized (i) field observations and (ii) simulation of non-measured variables with the STICS model, rather than default emission factors. As expected, fertilizers accounted for 80–90% of external emissions, being reduced by 50% and 102% with grain legumes introduction in GL1-BF and GL2-BF, compared to the cereal-based rotation (GL0-BF). Cover crops management increased machinery emissions by 24–35% compared to BF. Soil nitrous oxide (N 2 O) emissions were low, ranging between 205 and 333 kg CO 2 eq. ha−1 yr−1 in GL1-BF and GL0-BF, respectively. Nitrate leaching represented the indirect emission of 11.6 to 27.2 kg CO 2 eq. ha−1 yr−1 in the BF treatments and 8.2 to 10.7 kg CO 2 eq. ha−1 yr−1 in the CC treatments. Indirect emissions due to ammonia volatilization ranged between 8.4 and 41.8 kg CO 2 eq. ha−1 yr−1. The introduction of grain legumes strongly influenced SOC changes and, consequently, the C footprint. In the BF systems, grain legumes introduction in the rotations led to a significant increase in the C footprint, because of higher SOC losses. Contrarily, the use of cover crops mitigated SOC losses, and lowered the C footprint. These results indicated the need of CC when increasing the number of grain legumes in cereal-based rotations. Despite the multiple known benefits of introducing grain legumes in cropping systems our research highlights the need to consider soil organic carbon changes in environmental assessments. Highlights • Need to include soil organic carbon (SOC) in the cropping system assessment • External emissions of cropping systems with 1 and 2 grain legume (GL) crops were reduced by 50 and 102%. • Cover crops management increased machinery emissions by 24–35% compared to bare fallow. • Cover crops insertion in rotations with GL reduced SOC losses and reduced C footprint. [ABSTRACT FROM AUTHOR]

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.

Wastewater treatment plants (WWTPs) are one of the important sources of greenhouse gas (GHG) emission. There is a need for systematical tool that can be used to analyze GHG emission from WWTPs, and to evaluate the associated reduction strategies. In this paper, a systematic analysis methodology, called the greenhouse emission pinch analysis (GEPA), is developed for this purpose. GEPA is graphical in nature, and can be used to analyze the on-site and off-site GHG emissions of the WWTP. Furthermore, three GHG reduction strategies, i.e., increased aeration capacity, external carbon source controller, and reuse of biogas, are evaluated for their environmental load and operational cost reduction using the GEPA. A case study is used to elucidate the proposed method. In this study, the third strategy which reuses biogas from anaerobic digestion shows the largest reduction of GHG emissions. [ABSTRACT FROM AUTHOR]

An elaborate model was developed to estimate on-site and off-site greenhouse gases (GHGs) generated from wastewater treatment plants (WWTPs). The model was applied to a hybrid treatment system (five-stage Bardenpho processes) treating 5500 m 3 d −1 of municipal wastewater with 200 mg L −1 influent biochemical oxygen demand (BOD). A sensitivity analysis was performed to predict the potential variability of GHG emissions from the WWTP. On-site GHG emissions related to biochemical reactions at the system were estimated to be 8264 ± 678kgCO 2 e d −1 . The major source of on-site GHG emissions was the first aeration tank, and these were caused by the release of dissolved and accumulated GHGs by air-blowing. Off-site GHG emissions related to electricity consumption, chemical production, and transportation were estimated to be 4591 ± 576 kgCO 2 e d −1 . Off-site production of chemicals to be used on-site was identified as the primary source of the off-site GHG emissions. The recovery of biogas and its reuse as electricity reduced the overall GHG emissions. The results obtained from the newly developed model (10.6 kgCO 2 e·kg −1 BOD) were 2.83–4.24 times greater than those obtained from previous studies. From the results of this study, an appropriate methodology is proposed to accurately estimate GHG emissions from WWTPs and tactics are outlined for reducing GHG emissions without reducing the quality of treated wastewater. [ABSTRACT FROM AUTHOR]

The overall on-site and off-site greenhouse gas emissions by wastewater treatment plants (WWTPs) of food processing industry were estimated by using an elaborate mathematical model. Three different types of treatment processes including aerobic, anaerobic and hybrid anaerobic/aerobic processes were examined in this study. The overall on-site emissions were 1952, 1992, and 2435 kg CO2e/d while the off-site emissions were 1313, 4631, and 5205 kg CO2e/d for the aerobic, anaerobic and hybrid treatment systems, respectively, when treating a wastewater at 2000 kg BOD/d. The on-site biological processes made the highest contribution to GHG emissions in the aerobic treatment system while the highest emissions in anaerobic and hybrid treatment systems were obtained by off-site GHG emissions, mainly due to on-site material usage. Biogas recovery and reuse as fuel cover the total energy needs of the treatment plants for aeration, heating and electricity for all three types of operations, and considerably reduce GHG emissions by 512, 673, and 988 kg CO2e/d from a total of 3265, 6625, and 7640 kg CO2e/d for aerobic, anaerobic, and hybrid treatment systems, respectively. Considering the off-site GHG emissions, aerobic treatment is the least GHG producing type of treatment contrary to what has been reported in the literature. [Copyright &y& Elsevier]