What drives methane emissions from sanitation containment systems?

Tracking enteric pathogen contamination from on-site sanitation facilities to groundwater in selected rural areas of Vhembe District Municipality, Limpopo Province, South Africa

Greenhouse gas emissions from on-site sanitation systems: A systematic review and meta-analysis of emission rates, formation pathways and influencing factors

MotivationProper management of fecal sludge has significant positive health and environmental externalities. Most research on managing onsite sanitation so far either simulates the costs of, or the welfare effects from, managing sludge in situ in pit latrines. Thus, designing management strategies for onsite rural sanitation is challenging, because the actual costs of transporting sludge for treatment, and sources for financing these transport costs, are not well understood.MethodsIn this paper we calculate the actual cost of sludge management from onsite latrines, and identify the contributions that latrine owners are willing to make to finance the costs. A spreadsheet-based model is used to identify a cost-effective transport option, and to calculate the cost per household. Then a double-bound contingent valuation method is used to elicit from pit-latrine owners their willingness-to-pay to have sludge transported away. This methodology is employed for the case of a rural subdistrict in Bangladesh called Bhaluka, a unit of administration at which sludge management services are being piloted by the Government of Bangladesh.ResultsThe typical sludge accumulation rate in Bhaluka is calculated at 0.11 liters/person/day and a typical latrine will need to be emptied approximately once every 3 to 4 years. The costs of emptying and transport are high; approximately USD 13 per emptying event (circa 14% of average monthly income); household contributions could cover around 47% of this cost. However, if costs were spread over time, the service would cost USD 4 per year per household, or USD 0.31 per month per household—comparable to current expenditures of rural households on telecommunications.ConclusionThis is one of few research papers that brings the costs of waste management together with financing of that cost, to provide evidence for an implementable solution. This framework can be used to identify cost effective sludge management options and private contributions towards that cost in other (context-specific) administrative areas where onsite sanitation is widespread.

Sanitation coverages in selected Southeast Asian countries, namely Myanmar, Thailand and Vietnam, were increased from 1990 to 2015. The toilet coverage of 96, 100 and 99% was reported in Myanmar, Thailand and Vietnam, respectively. On contrary, incidences of waterborne disease and water pollution are still in existence. This situation is due mainly to poor design, performance and maintenance of the dominantly used on-site sanitation systems (OSS) such as septic tanks, cesspools. In addition, fecal sludge (FS), which has to be emptied from these OSS, is not properly managed. There are lacks in rules and regulation on FS management (FSM). Recent research conducted at the Asian Institute of Technology, Thailand, involved the development of innovative OSS, namely solar septic tanks, Zyclone cube toilet and septic tank effluent treatment units. The operation of solar septic tanks with increased temperatures of 40–50 °C could inactive E. coli by 4–6 logs in the effluent. The solar septic tanks enhanced the microbial degradability with increased methane gas production and reducing fecal sludge accumulation by 50%. The Zyclone cube toilet separated the toilet wastewater into solid and liquid portions, which were treated by heating and electrochemical disinfection, respectively. The septic tank effluent was further treated by a unit consisting of granular activated carbon coated with nano-silver resulting in E. coli reduction of 5–6 logs. These technologies should be applied for OSS in Southeast Asian and other developing regions for environmental improvement and public health protection.

As wastewater-based epidemiology (WBE) broadens its focus to include prevalent diseases with significant global health impact, existing surveillance systems concentrate on sewer-based infrastructure, which excludes the 2.7 billion people using non-sewered systems. To address this gap, our study explores the potential of fecal sludge treatment plants (FSTPs) for WBE, emphasizing the stability of virus RNA targets within pooled fecal sludge. We screened fecal sludge from a centralized treatment facility in Dakar, Senegal for SARS-CoV-2, human norovirus (HuNoV), and microbial source trackers (MSTs) pepper mild mottle virus (PMMoV) and tomato brown rugose fruit virus (ToBRFV). Decay kinetics of genomic RNA markers from these viruses were examined at 4 °C, 15 °C, and 30 °C over 70 days. Results indicate high persistence of viral targets in fecal sludge (T90 value of 3.3 months for exogenous SARS-CoV-2 N1 and N2, 6.2 months for ToBRFV), with all targets detected throughout the 70-day experiment under various temperatures with limited decay (<1 log10 reduction). This study addresses a crucial gap in understanding virus persistence in on-site sanitation systems by providing essential decay rate constants for effective target detection. Our results indicate that sampling at centralized facilities treating fecal sludge from on-site sanitation could facilitate localized pathogen surveillance in low-income settings.HighlightsInvestigation of the persistence of SARS-CoV-2, HuNoV, PMMoV, and ToBRFV genomic RNA in pooled fecal sludge derived from on-site sanitation systems.Novel microbial source tracker (MST), ToBRFV, exhibited comparable abundance to PMMoV, a well-established MST, in fecal sludge.No significant decay observed for HuNoV and PMMoV over 70 days at all temperature conditions (4, 15, and 30 °C).SARS-CoV-2 N1 and N2 showed T90values of 3.3 months at 30 °C.Fecal sludge treatment plants offer a centralized sampling location for wastewater-based epidemiology, providing a strategic approach for monitoring public health.Graphical Abstract

On-site sanitation systems, the commonest sanitation technologies in low-income countries, are central to the elimination of open defecation in such countries. Nevertheless, their selection and application in the physical and socio-economic environment of low-income settings could be a complex and challenging task. Poorly designed and constructed facilities could pollute groundwater resources and create nuisances to the user and the general public. Meanwhile, local authorities in these countries often lack the human resource with the requisite technical capacity to analyse situations and recommend appropriate solutions. This calls for guidance in the most crucial technical decisions that affect the safe usage and environmental sustainability of on-site sanitation technologies. This Chapter reviews salient standards and guidelines for the selection of appropriate technologies, prevention of groundwater pollution, control of odor and fly nuisance, structural stability and safety of the latrine user.

Abstract. Due to ongoing climate change, methane (CH4) emissions from vegetated wetlands are projected to increase during the 21st century, challenging climate mitigation efforts aimed at limiting global warming. However, despite reports of rising emission trends, a comprehensive evaluation and attribution of recent changes remains limited. Here we assessed global wetland CH4 emissions from 2000–2020 based on an ensemble of 16 process-based wetland models. Our results estimated global average wetland CH4 emissions at 158 ± 24 (mean ± 1σ) Tg CH4 yr−1 over a total annual average wetland area of 8.0 ± 2.0×106 km2 for the period 2010–2020, with an average increase of 6–7 Tg CH4 yr−1 in 2010–2019 compared to the average for 2000–2009. The increases in the four latitudinal bands of 90–30° S, 30° S–30° N, 30–60° N, and 60–90° N were 0.1–0.2, 3.6–3.7, 1.8–2.4, and 0.6–0.8 Tg CH4 yr−1, respectively, over the 2 decades. The modeled CH4 sensitivities to temperature show reasonable consistency with eddy-covariance-based measurements from 34 sites. Rising temperature was the primary driver of the increase, while precipitation and rising atmospheric CO2 concentrations played secondary roles with high levels of uncertainty. These modeled results suggest that climate change is driving increased wetland CH4 emissions and that direct and sustained measurements are needed to monitor developments.

The Sustainable Development Goals (SDGs) targets for the improvement of drinking water, sanitation, and hygiene (WASH) makes the development of wastewater infrastructure in many countries is increasing. In Indonesia, the development of sewer connections remained limited nationally, most households still rely on on-site sanitation systems that mainly use septic tanks technology. Septic tank as watertight containment itself cannot provide the treatment to comply with the effluent standard of domestic wastewater, while a lot of application of septic tank do not follow by suggested technology for further treatment. That makes the need of septic tank improvement as modified septic tank (MST) system. One of parameters removed by MST better is microbial content. This research aims to identify Escherichia coli inactivation in MST, how the process along the treatment impact E. coli concentration and identification the effectiveness of trichloroisocyanuric acid (TCCA) tablet application as disinfectant in E. coli inactivation, and concurrently safe to environment. This research was conducted in laboratory using MST reactor set-up consists of pre-sedimentation chamber, fixed bed anoxic chamber, and MBBR chamber to treat synthetic wastewater. The synthetic wastewater, composed by C6H12O6, NH4Cl, KH2PO4 and E. coli culture is used. With influent E. coli concentration was 108-109, it was reduced to 108 in pre sedimentation chamber, 106-107 in fixed bed anoxic chamber, 105-106 in MBBR chamber and final effluent, all in MPN/100 ml unit. E. coli was inactivated 99.84% along MST process but with relative high concentration to be discharged. Application of TCCA tablet 90% active chlorine with contact time 15 minutes is adequate to inactivate E. coli completely but generates high concentration of chlorine residual.

CH4 release rates from rice paddies were measured in Vercelli, Italy, in 1983 during a complete vegetation period, using a static box system. The rice paddies were found to be a source of atmospheric methane during the time of flooding. The CH4 release rates range between a few milligrams of CH4 per square meter per hour and 51 mg CH4 m−2 h−1 and show a seasonal variation with maximum emission rates between tillering and flowering. Averaged over the complete vegetation period, the CH4 release rate accounts for 16 mg m−2 h−1. Significant differences in the CH4 release rates of unfertilized field plots and plots fertilized with mineral fertilizer (CaCN2) were not observed. The CH4 release rates show strong diurnal variations, with highest values in the late afternoon and lowest values in the early morning, which coincides with the temperature variation in the upper soil layer (1–10 cm). These variations must be taken into account in estimating reliable global CH4 emission rates from rice paddies. CH4 is almost exclusively emitted into the atmosphere by gas bubbles during the first 6 weeks after flooding the rice paddies, that is, on fields without vegetation. Afterwards, 80% of the observed CH4 transport from the paddy soil into the atmosphere was due to diffusion through the stems of the rice plants. Transport by diffusion through the paddy water appeared to be of minor importance. The global annual CH4 emission from rice paddies is estimated to be of the order of 39–94 Tg yr−1 (Tg = 1012 g) for 1940 conditions and 70–170 Tg yr−1 for 1979 conditions, indicating a secular trend of the CH4 emission by rice paddies of about 1.6% per year during the last 35 years.

To characterize the relationship between child faeces disposal and child growth in low- and middle-income countries. We analysed caregiver responses and anthropometric data from Demographic and Health Surveys (2005-2014) for 202614 children under five and 82949 children under two to examine the association between child faeces disposal and child growth. Child faeces disposal in an improved toilet was associated with reduced stunting for children under five [adjusted prevalence ratio (aPR)=0.90, 95% confidence interval (CI) 0.89-0.92] and a 0.12 increase in height-for-age z-score (HAZ; 95% CI: 0.10-0.15) among all households. Among households with improved sanitation access, practicing improved child faeces disposal was still associated with a decrease in stunting (aPR=0.94, 95% CI: 0.91-0.96) and a 0.09 increase in HAZ (95% CI: 0.06-0.13). Improved child faeces disposal was also associated with reductions in underweight and wasting, and an increase in weight-for-age z-score (WAZ), but not an increase in weight-for-height z-score (WHZ). Community coverage level of improved child faeces disposal was also associated with stunting, with 75-100% coverage associated with the greatest reduction in stunting. Child faeces disposal in an unimproved toilet was associated with reductions in underweight and wasting, but not stunting. Improved child faeces disposal practices could achieve greater reductions in child undernutrition than improving toilet access alone. Additionally, the common classification of child faeces disposal as 'safe' regardless of the type of toilet used for disposal may underestimate the benefits of disposal in an improved toilet and overestimate the benefits of disposal in an unimproved toilet.

Monitoring methane (CH4) emissions from terrestrial ecosystems is essential for assessing the relative contributions of natural and anthropogenic factors leading to climate change and shaping global climate goals. Fires are a significant source of atmospheric CH4, with the increasing frequency of megafires amplifying their impact. Global fire emissions exhibit large spatiotemporal variations, making the magnitude and dynamics difficult to characterize accurately. In this study, we reconstruct global fire CH4 emissions by integrating satellite carbon monoxide (CO)-based atmospheric inversion with well-constrained fire CH4 to CO emission ratio maps. Here we show that global fire CH4 emissions averaged 24.0 (17.7–30.4) Tg yr−1 from 2003 to 2020, approximately 27% higher (equivalent to 5.1 Tg yr−1) than average estimates from four widely used fire emission models. This discrepancy likely stems from undetected small fires and underrepresented emission intensities in coarse-resolution data. Our study highlights the value of atmospheric inversion based on fire tracers like CO to track fire-carbon-climate feedback.

Review: Fifty years of research on rumen methanogenesis: lessons learned and future challenges for mitigation

Abstract. To track progress towards keeping global warming well below 2 ∘C or even 1.5 ∘C, as agreed in the Paris Agreement, comprehensive up-to-date and reliable information on anthropogenic emissions and removals of greenhouse gas (GHG) emissions is required. Here we compile a new synthetic dataset on anthropogenic GHG emissions for 1970–2018 with a fast-track extension to 2019. Our dataset is global in coverage and includes CO2 emissions, CH4 emissions, N2O emissions, as well as those from fluorinated gases (F-gases: HFCs, PFCs, SF6, NF3) and provides country and sector details. We build this dataset from the version 6 release of the Emissions Database for Global Atmospheric Research (EDGAR v6) and three bookkeeping models for CO2 emissions from land use, land-use change, and forestry (LULUCF). We assess the uncertainties of global greenhouse gases at the 90 % confidence interval (5th–95th percentile range) by combining statistical analysis and comparisons of global emissions inventories and top-down atmospheric measurements with an expert judgement informed by the relevant scientific literature. We identify important data gaps for F-gas emissions. The agreement between our bottom-up inventory estimates and top-down atmospheric-based emissions estimates is relatively close for some F-gas species (∼ 10 % or less), but estimates can differ by an order of magnitude or more for others. Our aggregated F-gas estimate is about 10 % lower than top-down estimates in recent years. However, emissions from excluded F-gas species such as chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs) are cumulatively larger than the sum of the reported species. Using global warming potential values with a 100-year time horizon from the Sixth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), global GHG emissions in 2018 amounted to 58 ± 6.1 GtCO2 eq. consisting of CO2 from fossil fuel combustion and industry (FFI) 38 ± 3.0 GtCO2, CO2-LULUCF 5.7 ± 4.0 GtCO2, CH4 10 ± 3.1 GtCO2 eq., N2O 2.6 ± 1.6 GtCO2 eq., and F-gases 1.3 ± 0.40 GtCO2 eq. Initial estimates suggest further growth of 1.3 GtCO2 eq. in GHG emissions to reach 59 ± 6.6 GtCO2 eq. by 2019. Our analysis of global trends in anthropogenic GHG emissions over the past 5 decades (1970–2018) highlights a pattern of varied but sustained emissions growth. There is high confidence that global anthropogenic GHG emissions have increased every decade, and emissions growth has been persistent across the different (groups of) gases. There is also high confidence that global anthropogenic GHG emissions levels were higher in 2009–2018 than in any previous decade and that GHG emissions levels grew throughout the most recent decade. While the average annual GHG emissions growth rate slowed between 2009 and 2018 (1.2 % yr−1) compared to 2000–2009 (2.4 % yr−1), the absolute increase in average annual GHG emissions by decade was never larger than between 2000–2009 and 2009–2018. Our analysis further reveals that there are no global sectors that show sustained reductions in GHG emissions. There are a number of countries that have reduced GHG emissions over the past decade, but these reductions are comparatively modest and outgrown by much larger emissions growth in some developing countries such as China, India, and Indonesia. There is a need to further develop independent, robust, and timely emissions estimates across all gases. As such, tracking progress in climate policy requires substantial investments in independent GHG emissions accounting and monitoring as well as in national and international statistical infrastructures. The data associated with this article (Minx et al., 2021) can be found at https://doi.org/10.5281/zenodo.5566761.

Synthesis of recent ground-level methane emission measurements from the U.S. natural gas supply chain

Acknowledging the resources in human excreta provides new options to address future challenges for fertilizer availability and nutrient management in a sustainable way. In dry on-site sanitation systems, the high nutrient concentration and low volume of the waste provides an opportunity for low-tech recycling, while the product can be a valuable input to the local agro-ecological system. However, successful recycling requires balanced fertilization with a low environmental impact. The aim of this study was therefore, to evaluate and compare the nutritional content and fertilizer potential of different organic amendments derived from human excreta. Nine amendments were obtained previously by treating human excreta from a dry toilet through composting or fermentation at 7°C, 20°C or 38°C, followed by a secondary vermicomposting. We evaluated the fertilizer potential of the amendments by conducting a soil incubation study to determine nitrogen and phosphorus mineralization, and by a pot experiment with barley. For all amendments, the nitrogen mineralization was slow and the available nitrogen determined the yield. The treatment method had a significant effect on the availability of nitrogen and the amendments obtained by active composting at 38°C had significantly higher levels of total and mineral nitrogen than those composted/fermented at 7°C and 20°C. These amendments also led to the highest barley yields, which were equivalent to a mineral nitrogen fertilization of 30 to 60 kg N ha−1. These findings contribute towards better agronomic value quantification of products from on-site dry sanitation systems and the effect of treatment method on the availability of nitrogen.