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Biochar addition plays an important role in manure composting, but its driving mechanism on microbial succession and humification process of human excreta composting is still unclear. In the present study, the mechanism of biochar addition was explored by analysing the humification process and microbial succession pattern of human excreta aerobic composting without and with 10% biochar (HF and BHF). Results indicated that BHF improved composting temperature, advanced the thermophilic phase by 1 d, increased the germination index by 49.03%, promoted the growth rate of humic acid content by 17.46%, and raised the compost product with the ratio of humic acid to fulvic acid (HA/FA) by 16.19%. Biochar regulated the diversity of fungi and bacteria, increasing the relative abundance of Planifilum, Meyerozyma and Melanocarpus in the thermophilic phase, and Saccharomonospora, Flavobacterium, Thermomyces and Remersonia in the mature phase, which accelerates the humification. Bacterial communities' succession had an obvious correlation with the total carbon, total nitrogen, and temperature (P < 0.05), while the succession of fungal communities was influenced by the HA/FA and pH (P < 0.05). This study could provide a reference for the improvement of on-site human excreta harmless by extending the thermophilic phase, and facilitating the humification in human excreta compost with biochar addition. [ABSTRACT FROM AUTHOR]

Ecological sanitation involves the use of hygienized human excreta as fertilizer in agriculture. This study aimed to establish the effects of hygienized urine and feces on cocoa production in the village of Blanfla in the Bouaflé Department of Côte d'Ivoire. To this end, 539 people from 100 households were trained in the use of urine-diverting dry toilets (UDDTs) and in fertilizing cocoa plantations with hygienized excreta from UDDTs. The study ran from 2014 to 2017, during which time 6 months were spent building the TSDUs and 1.5 months were monitoring their use. For 2 years, three categories of plantations (young, mature and old) with a total surface area of 285 ha were fertilized by the application of almost 445 m³ of urine and 100 tonnes of hygienized feces. The quantity of biofertilizer applied to the three groups of plantations almost doubled the annual cocoa production (RP=1.95). In all three plantation categories, crop production was significantly associated with BF application (r = 0.993; p = 0.007/r = 0.975; p = 0.025) but not with temperature or rainfall. The use of hygienized urine and feces as biofertilizers through the ecological sanitation approach should be popularized, as it increases agricultural productivity and farmer incomes. [ABSTRACT FROM AUTHOR]

Low-quality, infectious pathogens, toxic chemicals, heavy metals, genotoxic, or radioactive particles are associated problems of biogas derived from human excreta. Most researchers had focussed solely on production optimization but with realities of pathogenic bioaerosols that may be dangerous to the users, there is a need to focus on the clean source-enhanced biogas production from human excreta. This research is designed to seek clear optimizable parameters in the clean production of biogas and its commercialization. A laboratory set-up was constructed to determine the biogas yield, bacteria mass, time of highest yield, and temperature. The surface response method was used to examine the influence of the microbial growth modifications from syntropic acetate oxidation (SAO) to a novel syntropic calcium acetate oxidation (SCAO) bacteria-using eggshell. It was observed that the human biogas production can be as high as 1020 g/ml on laboratory-scale within 30 days. More so, the biogas quality was improved by crashing the nitrogen gas content by 66%. The SCAO bacteria was observed to decompose the ammonia gas to form methane and NOx gases at a ratio of 3:1 within the first 20 days. The novel SCAO bacteria are suggested as good candidates to control ammonia and greenhouse gas emissions from human waste. It is recommended that there are still more to be done in culturing SCAO bacteria with slow growth and longer life span to make this process appreciate to industrial scale. [ABSTRACT FROM AUTHOR]

Blackwater (source-separated toilet wastewater) is highly concentrated in both organic carbon and nutrients. A consensus prevails that blackwater is a valuable resource instead of waste. Anaerobic digestion (AD), with the advantages of sanitation, energy recovery, and nutrient conservation, holds great promise as a core technology employed in blackwater management. The difficulties of blackwater AD processes lie in their poor performance and operational stability. Research in this direction has intensified to achieve comprehensive and effective blackwater recovery. This article provides critical and comprehensive insights into research achievements on blackwater AD. The characteristics of blackwater, influential factors, underlying mechanisms, and recent improvement strategies are discussed and concluded. The results showed that the high solid organic and ammonia contents in blackwater contributed most to the hindrances in AD process. Strategies including appropriate pretreatment methods, co-digestion with high-carbon-content wastes, or enrichment of hydrogenotrophic methanogens can significantly improve the methane recovery efficiency. Moreover, the fate of pathogens and pharmaceuticals during AD process and several digestate management technologies are investigated to achieve safe and reliable recycling. Taking these findings together, the recommendations for further development in blackwater AD are proposed. This work will serve as a basis for future research and chart a path toward a new paradigm of blackwater management. [ABSTRACT FROM AUTHOR]

Substituting biogas for Liquefied Petroleum Gas (LPG) in households is a long-awaited sustainable solution for the increasing cost of energy and large amounts of household human-generated waste. Nevertheless, a study of the characteristics of feedstocks is essential to maximise their energy potential. Consequently, this study examined the physico-chemical properties of Human Excreta (HE), Food Leftovers (FLO), Kitchen Residue (KR) and Cow Dung (CD) of Ghanaian origin adhering to recommended standards. Results for volatile to total solid ratios (VS/TS) were 0.81 ± 0.001, 0.97 ± 0.001,0.89 ± 0.001 and 0.85 ± 0.001 for HE, FLO, KR and CD, respectively. The results showed that all feedstocks had high biodegradable content, making them desirable for biogas production. The carbon-to-nitrogen (C/N) ratios determined from the elemental compositions were 8.29 ± 0.09, 22.14 ± 0.26, 23.34 ± 0.25 and 26.19 ± 0.47 for HE, FLO, KR and CD, respectively. Although the C/N ratios for FLO, KR and CD were within the optimal range, that of HE was significantly low. With a mean alkalinity of 1219.67 ± 1.53, 630.00 ± 0.58, 590.00 ± 2.08 and 15,730.00 ± 6.00 mg CaCO3 eq./L for HE, FLO, KR and CD, it was observed that only CD has the optimal alkalinity value for anaerobic digestion. This brings into perspective the need for co-digestion and the choice of potential co-substrates for household biogas production.

Ecological sanitation involves the use of hygienized human excreta as fertilizer in agriculture. This study aimed to establish the effects of hygienized urine and feces on cocoa production in the village of Blanfla in the Bouaflé Department of Côte d'Ivoire. To this end, 539 people from 100 households were trained in the use of urine-diverting dry toilets (UDDTs) and in fertilizing cocoa plantations with hygienized excreta from UDDTs. The study ran from 2014 to 2017, during which time 6 months were spent building the TSDUs and 1.5 months were monitoring their use. For 2 years, three categories of plantations (young, mature and old) with a total surface area of 285 ha were fertilized by the application of almost 445 m3 of urine and 100 tonnes of hygienized feces. The quantity of biofertilizer applied to the three groups of plantations almost doubled the annual cocoa production (RP=1.95). In all three plantation categories, crop production was significantly associated with BF application (r = 0.993; p = 0.007/r = 0.975; p = 0.025) but not with temperature or rainfall. The use of hygienized urine and feces as biofertilizers through the ecological sanitation approach should be popularized, as it increases agricultural productivity and farmer incomes.

Anaerobic digestion of multiple substrates can generate more biogas while remaining stable, if positive synergistic effects are achieved. The type of co-digested substrates and the mixing ratio used, are the most important variables as each substrate has unique set of characteristics. Optimizing the volume ratios by testing various substrate mixing ratios is a popular method for determining the best-performing ratio of substrate mixture. The ternary mixture design has reportedly been found to quicken the process of testing different mixing ratios with high accuracy without running several experiments. Therefore, a ternary mixture design and a response surface approach are used in this work to ascertain the relationship between substrate mix and responses (biogas yield, methane yield, and synergy). The findings of the experiment revealed that R9 comprising 78.8 % human excreta, 11.8 % food leftovers and 9.4 % kitchen residue, had the highest methane production of 764.79 mLCH4/gVS and a synergistic index of 3.26. Additionally, the 3D response surface plots from the response surface model showed important and shared interactions between Human Excreta, (HE), Food Leftovers (FLO), and Kitchen Residue (KR). HE and KR had a similar positive synergistic effect on biogas yield, methane yield, and synergy, which was not the case for FLO. The response surface plots showed that the predicted responses (methane yield, biogas yield and synergy) increased with increasing HE and KR fractions and decreased with increasing FLO fractions in the substrate mixtures.

Biogas toilets are one of the most resource-efficient sanitation technologies. The technology has dual purposes of generating energy and stabilizing waste-producing biofertilizers. In Ethiopia, knowledge of human feces' energy potential is limited to optimize the development of biogas toilet facilities. Therefore, this study was aimed to evaluate the biogas and biofertilizer potential of human feces in Jimma City, Ethiopia, which may contribute to the development of sustainable sanitation technologies. The study was lab-based experimental design. In the lab-scale batch experiment, fresh human excreta samples were collected using a urine diversion raised toilet. Using ultimate and proximate laboratory analyses, the theoretical yield of biogas was predicted. Then a series of anaerobic digestion batch experiments were conducted to determine the practical energy yield. The bio-fertilizer potential of human feces was determined by analyzing the nutrient contents of human feces. The findings of this study showed that the bio-methane yield from the experimental results has a mean of 0.393 m3 kg−1, which is 14.16 MJ kg−1. The bio-methane meter cube per capita per head per year were 28.71 (28.03–29.27) from the experimental result and 45.26 for the theoretical yield of methane. In this study, the bio-fertilizer potential of human feces was evaluated using nutrient analysis, specifically the NPK (nitrogen, phosphorus, and potassium). Accordingly, human feces contain potassium (2.29 mg kg−1), phosphorus (1.12 mg kg−1), and nitrogen (3.71 mg kg−1). This finding suggests the bio-methane potential of human feces can be used for energy recovery and alternative sanitation options, providing a positive remedy for the sanitation crisis in urban settings.

IntroductionThis research explored the status of the application of circular economy (CE) principles in the agricultural sector in the Nyanza district of Rwanda.MethodsA multi-methodological approach was used to collect mixed data from farmers and key stakeholders operating in two selected sectors of Muyira and Busasamana to evaluate the solid waste management value chain, assess the adoption of ecological latrines and explore farmers' perception on human waste fertilizers as a CE principle. Quantitative data was collected through interviews with a sample of 1244 farmers randomly selected from Busasamana (n = 598) and Muyira (n = 646). The data were interpreted according to the research questions and analysis was done using descriptive and inferential statistics.FindingsThe results indicated that waste management is still at a rudimentary stage in the localities studied, with a waste sorting rate of 2.2% and 1.1% but with a willingness of 96.9% in Busasamana and 99.5% in Muyira sector to sort waste from organic to non-organic at source. The majority of participants, represented by 80.3% of the surveyed farming households in Busasamana and 97.5% of their counterparts in Muyira generate between 1-2 sacks of household waste per week. Food-related waste was the most predominant in Busasamana households, accounting for 99.5% while Muyira farmer households generate both food and yard wastes in proportions of 58% and 41.6% respectively. It's worth knowing that waste is dumped in the domestic rubbish pits in the two sectors, with 88% and 77.9% in Busasamana and Muyira sectors. Furthermore, the research revealed the absence of a waste collection and transport provider and a landfill in the Muyira sector, while waste collection facilities are available in Busasamana. Low adoption rates of eco-friendly latrines were observed, as farmers trick to the use of traditional pit latrines at 98.2% of the households in Busasamana and 100% in Muyira sector. Muyira being far ahead of its Busasamana counterparts in toilet dislodging (67% vs. 33%).Conclusion and recommendationsGreater involvement of all actors in the system to ensure the success of the application of CE practices and initiatives was recommended as well as awareness raising and capacity building on the use of ecological latrines.

Human and animal waste, including waste products originating from human or animal digestive systems, such as urine, feces, and animal manure, have constituted a nuisance to the environment. Inappropriate disposal and poor sanitation of human and animal waste often cause negative impacts on human health through contamination of the terrestrial environment, soil, and water bodies. Therefore, it is necessary to convert these wastes into useful resources to mitigate their adverse environmental effect. The present study provides an overview and research progress of different thermochemical and biological conversion pathways for the transformation of human- and animal-derived waste into valuable resources. The physicochemical properties of human and animal waste are meticulously discussed, as well as nutrient recovery strategies. In addition, a bibliometric analysis is provided to identify the trends in research and knowledge gaps. The results reveal that the USA, China, and England are the dominant countries in the research areas related to resource recovery from human or animal waste. In addition, researchers from the University of Illinois, the University of California Davis, the Chinese Academy of Sciences, and Zhejiang University are front runners in research related to these areas. Future research could be extended to the development of technologies for on-site recovery of resources, exploring integrated resource recovery pathways, and exploring different safe waste processing methods. [ABSTRACT FROM AUTHOR]

Substituting biogas for Liquefied Petroleum Gas (LPG) in households is a long-awaited sustainable solution for the increasing cost of energy and large amounts of household human-generated waste. Nevertheless, a study of the characteristics of feedstocks is essential to maximise their energy potential. Consequently, this study examined the physico-chemical properties of Human Excreta (HE), Food Leftovers (FLO), Kitchen Residue (KR) and Cow Dung (CD) of Ghanaian origin adhering to recommended standards. Results for volatile to total solid ratios (VS/TS) were 0.81 ± 0.001, 0.97 ± 0.001,0.89 ± 0.001 and 0.85 ± 0.001 for HE, FLO, KR and CD, respectively. The results showed that all feedstocks had high biodegradable content, making them desirable for biogas production. The carbon-to-nitrogen (C/N) ratios determined from the elemental compositions were 8.29 ± 0.09, 22.14 ± 0.26, 23.34 ± 0.25 and 26.19 ± 0.47 for HE, FLO, KR and CD, respectively. Although the C/N ratios for FLO, KR and CD were within the optimal range, that of HE was significantly low. With a mean alkalinity of 1219.67 ± 1.53, 630.00 ± 0.58, 590.00 ± 2.08 and 15,730.00 ± 6.00 mg CaCO3 eq./L for HE, FLO, KR and CD, it was observed that only CD has the optimal alkalinity value for anaerobic digestion. This brings into perspective the need for co-digestion and the choice of potential co-substrates for household biogas production. [ABSTRACT FROM AUTHOR]

In the context of the ongoing pandemic of COVID-19, SARS-CoV-2 was detected in human excreta and environmental matrices. The occurrence of SARS-CoV-2 in environmental compartments raises questions on its fate and stability in these matrices and its potential to spread in the exposed communities. This review focused on the stability of the SARS-CoV-2 in human excreta, wastewater, soils, crops, and other environmental matrices, that may be reached through human excreta and sewage products spreading. Little is known about the persistence and survival of SARS-CoV-2 in the environment. Up to now sewage sludge, soil and crops are seldom investigated implying the convenience of considering future researches focusing on SARS-CoV-2 in soils receiving wastewater and sewage sludge, as well as on grown crops. Information regarding SARS-CoV-2 persistence in environmental media is crucial to establish and implement effective policies and measures for mitigating the transmission of COVID-19 and tackling eventual future outbreaks. [ABSTRACT FROM AUTHOR]

Interrupted power supply and poor access to electricity (15%) have been persistent problems in Malawi for decades. Diversification of resources is required to solve the challenges. Therefore, this study is aimed at conducting a techno-economic analysis of a hybrid system to ensure electricity reliability, bill reduction, and reduced grid demand at a school. The study investigated six hybrid system scenarios that had various combinations of the grid, diesel, solar PV, wind, biogas, and battery. The HOMER Pro model was used to determine the best system combination. Six scenarios were examined further using the CRITIC-PROMETHEE II approaches. The best system configuration included grid, solar PV, and biogas electricity. Biogas generation is mainly from human excreta. The study also investigated the effect of the 2022 inflation rate on the financial performance of the system, which had shown a sharp increase in capital, replacement, O&M costs, and payback time. The proposed system’s levelized cost of electricity is 0.095 $/kWh, which is less than Malawi’s grid’s levelized cost of 0.11 $/kWh. Environmentally, the system could help to reduce greenhouse emissions, including those from the sewage system. Therefore, schools and governments should invest in alternative energy generation.

In the M'zab valley, dry toilets represent an ancestral dry sanitation system, serving as a source of fertilizer thanks to human excrement valorization. However, in the 20th century, local populations began to shun these systems. The objective of this article is to illustrate the importance of dry toilets on agricultural and environmental scales in ancient M'Zab, and the renewal of these systems in response to sanitation problems in the oasis after their decline. The hypothesis put forward is that dry toilets can act as a complementary system to conventional sanitation systems. Data were collected through interviews with the local population. Our results show that the use of dry toilets, and the resulting use of human excrement as fertilizer, has gone through three phases. First, a phase of strong recycling dynamics, followed by a second phase of decline in dry toilet use which is linked to the discovery of the Albian aquifer and flush toilet adoption. The third phase is characterized by dry toilet reuse in response to oasis degradation caused by sanitation and environmental problems. Some oasesians have taken the initiative to revert to dry toilets to ensure oasis system sustainability and to revive the practice of recycling human waste. HIGHLIGHTS Reintroduction of dry toilets in the oases.; Reuse of human excrements for agricultural purposes.; Reduce the discharge of wastewater.; Protection of oases from degradation.; Alternative system of sanitation.;

It has been proposed that providing energy for cooking and lighting would solve over 65% of energy needs in rural communities. The use of biomass resources has been found not sustainable as other bioproducts such as biodiesel and bioethanol depend on it. More so that there is a depletion of bioresources in some parts of the world. The shift into animal waste such as poultry droppings and cattle dung has huge prospects, but it is not sustainable in the long term as rural farmers depend on it. The use of human excreta is the most available and sustainable due to the human population. This research aims to provide a workable blueprint of biogas production to meet energy needs. The research considers a laboratory‐scale experiment whose result is used to project the medium‐scale biodigester. Microbial culturing from human waste is used to initiate the codigestion of human excreta and powdered chicken feathers. It is observed that this procedure drastically reduces the high nitrogen content in the biogas and improves its methane and carbon dioxide content. It is observed that the scaled‐up biodigester in a worst case scenario can function at 67%. Design parameters are documented for the onward adoption of the technique. [ABSTRACT FROM AUTHOR]

Abstract It has been proposed that providing energy for cooking and lighting would solve over 65% of energy needs in rural communities. The use of biomass resources has been found not sustainable as other bioproducts such as biodiesel and bioethanol depend on it. More so that there is a depletion of bioresources in some parts of the world. The shift into animal waste such as poultry droppings and cattle dung has huge prospects, but it is not sustainable in the long term as rural farmers depend on it. The use of human excreta is the most available and sustainable due to the human population. This research aims to provide a workable blueprint of biogas production to meet energy needs. The research considers a laboratory‐scale experiment whose result is used to project the medium‐scale biodigester. Microbial culturing from human waste is used to initiate the codigestion of human excreta and powdered chicken feathers. It is observed that this procedure drastically reduces the high nitrogen content in the biogas and improves its methane and carbon dioxide content. It is observed that the scaled‐up biodigester in a worst case scenario can function at 67%. Design parameters are documented for the onward adoption of the technique.

In times of climate change, practicing a form of sustainable, climate-resilient and productive agriculture is of primordial importance. Compost could be one form of sustainable fertilizer, which is increasing humus, water holding capacity, and nutrient contents of soils. It could thereby strengthen agriculture toward the adverse effects of climate change, especially when additionally combined with biochar. To get access to sufficient amounts of suitable materials for composting, resources, which are currently treated as waste, such as human excreta, could be a promising option. However, the safety of the produced compost regarding human pathogens, pharmaceuticals (like antibiotics) and related resistance genes must be considered. In this context, we have investigated the effect of 140- and 154-days of thermophilic composting on the hygienization of human excreta and saw dust from dry toilets together with straw and green cuttings with and without addition of biochar. Compost samples were taken at the beginning and end of the composting process and metagenomic analysis was conducted to assess the fate of antibiotic resistance genes (ARGs) and pathogenicity factors of the microbial community over composting. Potential ARGs conferring resistance to major classes of antibiotics, such as beta-lactam antibiotics, vancomycin, the MLSB group, aminoglycosides, tetracyclines and quinolones were detected in all samples. However, relative abundance of ARGs decreased from the beginning to the end of composting. This trend was also found for genes encoding type III, type IV, and type VI secretion systems, that are involved in pathogenicity, protein effector transport into eukaryotic cells and horizontal gene transfer between bacteria, respectively. The results suggest that the occurrence of potentially pathogenic microorganisms harboring ARGs declines during thermophilic composting. Nevertheless, ARG levels did not decline below the detection limit of quantitative PCR (qPCR). Thresholds for the usage of compost regarding acceptable resistance gene levels are yet to be evaluated and defined. [ABSTRACT FROM AUTHOR]

Composting organic waste and human excreta could significantly reduce the amount of waste dumped and increase soil fertility and agricultural yields. However, studies focusing on the replacement of mineral fertilizer with compost from these resources are rare. The presented study quantifies the potential of human excreta and other organic waste for compost production. During wet and dry seasons, the generation and composition of household solid waste (HSW) was measured from three wealth categories: poor, medium, and rich, as well as the organic waste generated from 20 commercial facilities. Furthermore, the amount of human excreta, when converting unimproved into ecological sanitation facilities, was assessed. The HSW generation was significantly higher in the wet (0.77 ± 0.07 kg fresh weight (FW) cap−1 day−1) compared to the dry season (0.54 ± 0.04 kg FW cap−1 day−1). Organic waste was the main component of HSW in the dry and wet seasons, accounting for 84% and 76% of the total HSW, respectively. Annually, about 6824 Mg of organic dry matter could be collected from households, 212 Mg from commercial units, and 12,472 Mg from ecological sanitation. With these resources, 11,732 Mg of compost could be produced annually and used for fertilizing 470 ha of farmland, completely replacing mineral fertilizer. [ABSTRACT FROM AUTHOR]

This paper explored people's perceptions on the use of human excreta for biogas generation in Ghana using the theory of planned behaviour (TPB). It sought to assess the effect of attitude, subjective norms and perceived behavioural control on people's behavioural intention to use human excreta (HEx) for biogas. Data collection was by questionnaire designed with the TPB constructs and other demographic information, and the analysis was done by structural equation modelling (SEM). The analysis produced two structural models: the standard TPB model and the adjusted model. Based on SEM, this study revealed that the adjusted model provides a useful and effective framework for analysing the interrelationships between socio-demographic variables and the standard TPB constructs than the standard TPB. Therefore, the results show that the effect of attitude, subjective norms and perceived behavioural control are all significant and positive. Though all the constructs were significant and positive, participants showed low perceived behavioural control or they perceive low ability of using HEx for biogas. Results revealed an adequate fit for people's behavioural intentions to use HEx for biogas. The adjusted model, generated by the inclusion of gender and education into the TPB model, provided a useful and effective framework for the interrelationships between socio-demographic variables and the TPB constructs than the standard TPB. Attitudes, subjective norms and perceived behavioural control significantly influenced intentions to use HEx for biogas. Though perceived behavioural control showed low controllability, subjective norm was a major factor with religion being key on intentions to use HEx for biogas generation. Gender and education had no direct significant influence on intentions, but their effects were mediated through the TPB factors. It was further revealed that knowledge on the benefits of biogas as well as the perceived effect of using human excreta was strong and positive. Interventions aimed at promoting the use of HEx for biogas should address low controllability and that should include government subsidy and financial support as well as education to address stigma and HEx knowledge. The intervention should also bring on board important persons such as religious leaders and persons from relevant institutions to lead more open discussions on HEx use for biogas. [ABSTRACT FROM AUTHOR]

In times of climate change, practicing a form of sustainable, climate-resilient and productive agriculture is of primordial importance. Compost could be one form of sustainable fertilizer, which is increasing humus, water holding capacity, and nutrient contents of soils. It could thereby strengthen agriculture toward the adverse effects of climate change, especially when additionally combined with biochar. To get access to sufficient amounts of suitable materials for composting, resources, which are currently treated as waste, such as human excreta, could be a promising option. However, the safety of the produced compost regarding human pathogens, pharmaceuticals (like antibiotics) and related resistance genes must be considered. In this context, we have investigated the effect of 140- and 154-days of thermophilic composting on the hygienization of human excreta and saw dust from dry toilets together with straw and green cuttings with and without addition of biochar. Compost samples were taken at the beginning and end of the composting process and metagenomic analysis was conducted to assess the fate of antibiotic resistance genes (ARGs) and pathogenicity factors of the microbial community over composting. Potential ARGs conferring resistance to major classes of antibiotics, such as beta-lactam antibiotics, vancomycin, the MLSB group, aminoglycosides, tetracyclines and quinolones were detected in all samples. However, relative abundance of ARGs decreased from the beginning to the end of composting. This trend was also found for genes encoding type III, type IV, and type VI secretion systems, that are involved in pathogenicity, protein effector transport into eukaryotic cells and horizontal gene transfer between bacteria, respectively. The results suggest that the occurrence of potentially pathogenic microorganisms harboring ARGs declines during thermophilic composting. Nevertheless, ARG levels did not decline below the detection limit of quantitative PCR (qPCR). Thresholds for the usage of compost regarding acceptable resistance gene levels are yet to be evaluated and defined.

On-site small-scale sanitation is common in rural areas and areas without infrastructure, but the treatment of the collected fecal matter can be inefficient and is seldom directed to resource recovery. The aim of this study was to compare low-technology solutions such as composting and lactic acid fermentation (LAF) followed by vermicomposting in terms of treatment efficiency, potential human and environmental risks, and stabilization of the material for reuse in agriculture. A specific and novel focus of the study was the fate of native pharmaceutical compounds in the fecal matter. Composting, with and without the addition of biochar, was monitored by temperature and CO2 production and compared with LAF. All treatments were run at three different ambient temperatures (7, 20, and 38°C) and followed by vermicomposting at room temperature. Materials resulting from composting and LAF were analyzed for fecal indicators, physicochemical characteristics, and residues of ten commonly used pharmaceuticals and compared to the initial substrate. Vermicomposting was used as secondary treatment and assessed by enumeration of Escherichia coli, worm density, and physicochemical characteristics. Composting at 38°C induced the highest microbial activity and resulted in better stability of the treated material, higher N content, lower numbers of fecal indicators, and less pharmaceutical compounds as compared to LAF. Even though analysis of pH after LAF suggested incomplete fermentation, E. coli cell numbers were significantly lower in all LAF treatments compared to composting at 7°C, and some of the anionic pharmaceutical compounds were detected in lower concentrations. The addition of approximately 5 vol % biochar to the composting did not yield significant differences in measured parameters. Vermicomposting further stabilized the material, and the treatments previously composted at 7°C and 20°C had the highest worm density. These results suggest that in small-scale decentralized sanitary facilities, the ambient temperatures can significantly influence the treatment and the options for safe reuse of the material. [ABSTRACT FROM AUTHOR]

Inadequate fecal sludge treatment is contributing to the high prevalence of Opisthorchis viverrini (OV) infections in northeast Thailand. Two configurations of solar greenhouse drying beds were assessed and compared against a conventional covered (open-air) sand drying bed during two experimental rounds. The objectives were to compare sludge heating and drying rates among the beds and to identify factors associated with inactivation of OV eggs. The sludge temperatures (°C) in the greenhouse (daily x̅±SD = 32.8±1.8, 28.4±2.9) were higher than the covered open-air bed (27.0±1.8, 25.6±2.7) with 150-250 min per day >40°C during sunny days, while sludge temperatures in the open-air bed never exceeded 40°C. The addition of a solar-heated water system underneath the sand drying bed increased the sludge temperature (°C) further (33.9±1.8, 30.0±2.3; 350 to 450 minutes per day >40°C). With proper ventilation and air circulation, the solar greenhouse sand drying beds (first-order drying rate, k = 0.092, 0.193) were also able to dry sludge at a faster rate than the open-air bed (k = 0.076). Sludge dryness, sludge temperature, and time were significantly associated with increased OV inactivation. Solar irradiance and air relative humidity were identified as factors associated with sludge drying. These results highlight the importance of balancing enclosure to increase sludge heating with ventilation to reduce relative humidity in order to optimize OV egg inactivation. Solar greenhouse sand drying beds may provide a low-cost, low-technology option for fecal sludge management in tropical Thailand. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization may be a sustainable sanitary treatment for wet organic waste including human excreta. Human-excreta-derived hydrochar properties differ from those of typical wet biomass due to the formation of a biocrude-like phase at low reaction temperatures. This study characterized the importance of this phase in terms of hydrochar combustion properties and potential agricultural use. Hydrothermal carbonization of raw human excreta was undertaken at 180, 210, and 240 °C, after which the biocrude phase was extracted with dichloromethane. Physicochemical properties, surface-area parameters, combustion profiles, and gas emissions of non-extracted hydrochar, biocrude, and extracted hydrochar were compared. The potential agricultural use of extracted hydrochar was assessed in germination experiments. Biocrude comprised up to 49.5% of hydrochar mass with a calorific value of >60% that of extracted hydrochar. Biocrude combustion properties were better than those of hydrochar, before and after extraction as demonstrated by higher combustion index value (S i). The extracted hydrochar surface area (34.7 m2 g−1) was greater than that of non-extracted hydrochar (<2 m2 g−1), and seeds germinated more readily due to the lower phytotoxin content. Most macro and micronutrients required for plant growth were retained in the extracted hydrochar. The extraction of biocrude from human-excreta-derived hydrochar not only provided a higher-quality fuel with enhanced combustion properties but also improved hydrochar characteristics, suggesting its potential as a soil additive for enhanced plant growth. [Display omitted] • Human-excreta-derived hydrochar (HC) contains a major biocrude phase. • Biocrude has higher energy density and better fuel characteristics than HC. • Phytotoxins occur mainly in the biocrude phase. • Extracted HC has higher surface area and yields enhanced seed germination. [ABSTRACT FROM AUTHOR]

This policy brief argues that due to the failure of local municipalities, political instability, and corruption, hazards act synergistically with unequal and complex power relationships to reproduce and disproportionately distribute hazardous landscapes, particularly in the low-income communities of South Africa. It argues that when municipal bureaucrats hide behind a façade of claiming to do something about hazards and the associated challenges they present for low-income communities, but in reality take no action, they reveal their “dangerous mindscapes” which have devastating effects on low-income communities. The author defines “dangerous mindscapes” as the deliberate and consistent insistence that municipal bureaucrats are distributing and will distribute basic services to everyone in South Africa. This consistent insistence is rooted in an ideological mantra that the government is committed to distribute basic services, but in order to justify their failings; they construct basic service provision as dependent on class and citizenship. This study adopted a qualitative research design, grounded on the descriptive phenomenological approach. The study covers the period between 2015 and 2019. Twenty-four (24) in-depth interviews were conducted in the greater Mangaung low-income communities. The brief explores and highlights the climate change-urbanization nexus as politically propelled with devastating spatiality outcomes, where low-income community residents of Mangaung are forced to navigate a hazardous landscape that forces them to “walk at their own risk” because when hailstorms come, the residents are exposed to human excreta from improvised toilets that runs inside their houses and on the streets.

Treatment of human excreta (HE) is necessary before its discharge into natural water body. Untreated discharge may cause several ill effects for environment and human health. Anaerobic digestion of human excreta can unravel this problem along with production of biogas. Anaerobic digestion process may be either batch type or continuous type. In present study, human excreta were degraded anaerobically by both the means in the laboratory scale 5L capacity glass digesters. The comparative assessment between batch digestion and continuous digestion was carried out. The digesters were fed with human excreta at 6% Total Solids and operated at ambient temperature of 20-37°C for 99 days. The results show that average biogas production in batch feeding process is 322.78 mLday-1 whereas in continues digestion it is 382 mLday-1. Total biogas production during 99 days in batch digestion and continue digestion is 31955.1 mL and 37833.9 mL respectively. Average methane content in biogas produced in continuous and batch digestion was 68.0% and 67.4% respectively. Results conclude that human excreta can be successfully digested anaerobically to produce biogas with good methane content either by batch or continuous digestion process.

• How to integrate environmental concerns into Chemical Engineering education. • University education in Sustainable Development through two case studies. • Human waste can be managed to obtain energy, fertilizer and improve sanitation. • Mathematical Optimization is used in this context and explained for non-specialists. Given the damage that the natural environment suffers from human activities, it is relevant to provide ecological literacy to all Chemical Engineering students. Sometimes, this information is offered through elective courses and/or seminars and consequently it might not reach the whole class. Some courses have more obvious connections to environmental issues, while others do not appear to. In this paper, we aim to show through some solved examples how to introduce an environmental topic in the subject Mathematical Optimization. The problems goal is to decide on the best logistics for the transport and management of human waste that will be used in the production of sustainable energy. The context is that of improving the sanitation and hygiene in areas of the developing world, while simultaneously creating job opportunities within the communities. The research that we have conducted for finding the proper way to address the environmental analysis in class, led us first to the Sustainable Development Goals (SDGs), but later on, other theories such as the Cradle-to-Cradle (C2C) have proven to be more comprehensive and therefore, better. We believe that this multidisciplinary paper shows how to integrate environmental concerns and understanding in the Chemical Engineering curricula. [ABSTRACT FROM AUTHOR]

Anaerobic digestion of multiple substrates can generate more biogas while remaining stable, if positive synergistic effects are achieved. The type of co-digested substrates and the mixing ratio used, are the most important variables as each substrate has unique set of characteristics. Optimizing the volume ratios by testing various substrate mixing ratios is a popular method for determining the best-performing ratio of substrate mixture. The ternary mixture design has reportedly been found to quicken the process of testing different mixing ratios with high accuracy without running several experiments. Therefore, a ternary mixture design and a response surface approach are used in this work to ascertain the relationship between substrate mix and responses (biogas yield, methane yield, and synergy). The findings of the experiment revealed that R9 comprising 78.8 % human excreta, 11.8 % food leftovers and 9.4 % kitchen residue, had the highest methane production of 764.79 mLCH 4 /gVS and a synergistic index of 3.26. Additionally, the 3D response surface plots from the response surface model showed important and shared interactions between Human Excreta, (HE), Food Leftovers (FLO), and Kitchen Residue (KR). HE and KR had a similar positive synergistic effect on biogas yield, methane yield, and synergy, which was not the case for FLO. The response surface plots showed that the predicted responses (methane yield, biogas yield and synergy) increased with increasing HE and KR fractions and decreased with increasing FLO fractions in the substrate mixtures., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Blissbern Appiagyei Osei-Owusu reports financial support was provided by Regional Water and Environmental Sanitation Centre, Kumasi., (© 2024 Published by Elsevier Ltd.)

Soil-transmitted helminth (STH) infections caused 4.98 million years live with disability globally in 2014, mostly affecting the poor. When farmers handle excreta for reuse in agriculture, involuntary ingestion of excreta particles is an important infection pathway for STH infections. The aim of this study was to quantify farmers' ingestion of human excreta during common agricultural practices in Vietnam. The weight of excreta that remained on farmers' hands, the weight of excreta that would remain on a farmer' mouth after contact with hand, and the frequency of contact between hand to the mouth by observing farmers while they handled excreta were simulated and quantified. Our findings revealed that farmers are on average exposed 5.16 h to excreta handling per year. Based on this average exposure time, it was estimated that farmers ingest 91 mg of excreta per year (95% CI: 73–110 mg). Our study presents for the first time a robust quantitative estimation of excreta ingestion by farmers during excreta handling in agricultural practices. Hence, this paper makes an important contribution to more robust quantitative microbial risk assessment and health impact assessment related to STH infections and diarrhea in Vietnam and other similar settings where excreta is used as fertilizer. [ABSTRACT FROM AUTHOR]

• HEDF applications did not pose risk in terms of pathogen or heavy metals. • Perception of using HEDF needs to be supported with data. • Standards and certification can help to alleviate perception on HEDF. Land degradation and inadequate faecal sludge management are two major issues in Sub-Saharan Africa (SSA). The transformation of human excreta into soil amendments and their wide-scale adoption could improve soil health and contribute to solving the sanitation crisis in SSA. There are however perception challenges around these fertilisers because of the potentially harmful components they contain such as pathogens and heavy metals, which can be removed with appropriate treatment such as composting. A major barrier to the wide scale commercialisation of human excreta derived fertiliser (HEDF) is the unclear regulations surrounding their use. The aim of this study was to identify barriers to the use of HEDF by farmers participating in the horticultural export market with Kenya as focus area since horticultural exports are a major contributor to the country's economy. Global GAP is the most widely adopted standard for quality assurance of horticultural crops and the use of human sewage sludge is currently not allowed on certified farms. Interviews with stakeholders along the food export chain highlighted the complex interactions that exist between them and showed that Global GAP certified farmers were not willing to use HEDF on their farms even if local regulations recognise treated sludge as a valid input to agriculture. Several countries (like the UK, Sweden, Australia and the USA) created specific certification or assurance schemes to improve public perception of biosolids. The creation of a similar assurance or certification scheme specific to fertilisers made from source-separated human excreta would be a step into formalising them as a product, establishing production procedures, limits on contaminants content as well as testing protocols. Such a certification scheme could increase the confidence of regulating bodies in HEDF and lead to their acceptance by global farming standards. [ABSTRACT FROM AUTHOR]

Sustainable food production to achieve food security and increased access to safely managed sanitation are major global challenges. Treating human excreta and producing safe nutrient-rich soil amendments is an effective way of creating an incentive to tackle these two challenges. This research analysed the quality of fertilisers produced from human excreta and evaluated their acceptability within the local market. Antananarivo (Madagascar) was the field site for crop trial and three different fertilisers derived from human excreta were used to grow maize: digestate, compost and vermicompost, each derived from the previous one. The three fertilisers had different characteristics: nutrients were more concentrated in compost (23 g/kg) and vermicompost (11 g/kg) and mineralisation stages varied between them but did not cause any detrimental effect to crop yield. When compared to chemical fertilisers, the three human excreta derived fertilisers resulted in comparable yield which is encouraging. A series of 81 interviews were also carried out with farmers of the peri-urban area of Antananarivo, which highlighted the importance of characterising the market, identifying users' perceived needs and developing a product responding to these. The majority of local farmers perceived human excreta derived fertilisers as acceptable and gave great importance to their texture and general appearance. In this study, both the field trials and interviews suggest that there is a good potential to produce fertilisers from human excreta, which have a positive effect on crops and can be adopted in the local market. [ABSTRACT FROM AUTHOR]

This study explicates the scope of published literature on the influence of attitudes and perceptions on the intention to use human excreta and human excreta derived materials in agriculture. Using a scoping review methodology, search results from Scopus and Web of Science were screened and synthesized using the DistillerSR web-based application. Out of the 1192 studies identified, 22 published articles met the inclusion criteria. Additional studies were identified by keyword enrichment, hand-searching, and snowballing in other electronic data bases. The benefit perception of the soil health, income, and yield was the main driver for positive attitudes. Perceived health risk and socio-cultural factors were reported as the main barriers to the use of human excreta derived materials in agriculture. Limited information, availability, collection, transport, and storage were the other reported perceived barriers. The influence of socioeconomic and demographic factors on farmers’ attitudes and perceptions was inconclusive, which is potentially attributed to contextual and methodological differences. Social and behavior change communication through community mass campaigns and targeting interventions segregated by socioeconomic and demographic contexts is recommended for development interventions. Future empirical studies could focus on the influence of crop types, treatment processes, food preparation and processing on attitudes and perceptions.

Biogas toilets are one of the most resource-efficient sanitation technologies. The technology has dual purposes of generating energy and stabilizing waste-producing biofertilizers. In Ethiopia, knowledge of human feces' energy potential is limited to optimize the development of biogas toilet facilities. Therefore, this study was aimed to evaluate the biogas and biofertilizer potential of human feces in Jimma City, Ethiopia, which may contribute to the development of sustainable sanitation technologies. The study was lab-based experimental design. In the lab-scale batch experiment, fresh human excreta samples were collected using a urine diversion raised toilet. Using ultimate and proximate laboratory analyses, the theoretical yield of biogas was predicted. Then a series of anaerobic digestion batch experiments were conducted to determine the practical energy yield. The bio-fertilizer potential of human feces was determined by analyzing the nutrient contents of human feces. The findings of this study showed that the bio-methane yield from the experimental results has a mean of 0.393 m 3  kg -1 , which is 14.16 MJ kg -1 . The bio-methane meter cube per capita per head per year were 28.71 (28.03-29.27) from the experimental result and 45.26 for the theoretical yield of methane. In this study, the bio-fertilizer potential of human feces was evaluated using nutrient analysis, specifically the NPK (nitrogen, phosphorus, and potassium). Accordingly, human feces contain potassium (2.29 mg kg -1 ), phosphorus (1.12 mg kg -1 ), and nitrogen (3.71 mg kg -1 ). This finding suggests the bio-methane potential of human feces can be used for energy recovery and alternative sanitation options, providing a positive remedy for the sanitation crisis in urban settings., Competing Interests: The authors declare that they have no competing interests.The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

Abstract Poor sanitation due to improper treatment of human excreta, and energy scarcity are global problems with only partial solutions. Thus, feasible conversion of human excreta into safe, reusable "products" and renewable energy could be advantageous. The research objectives were to study the properties and major chemical processes occurring during hydrothermal carbonization of raw human excreta with typical solids content, as well as exploring potential use of the resulting hydrochar and aqueous phase. Human excreta (often considered as black water) were hydrothermally carbonized in a set of nine 50-mL laboratory batch reactors under a range of severities, a single parameter obtained from a coalification model that represents the combination of temperature and time. Three temperatures (180, 210 and 240 °C) and reaction times (30, 60 and 120 min) were used. The physicochemical characteristics such as yield, elemental composition, organic matter and calorific value of the hydrochar (solid phase) were studied. Aqueous phase was characterized for carbon, nitrogen, macro and micronutrients composition. In addition, the potential use of the hydrochar and aqueous phase were studied. There was high correlation between severity factor and carbon content (R2 = 0.95) and calorific value (R2 = 0.89). Hydrochar yield decreased with increasing severity from 69 to 56%. Calorific values increased from 24.7 to 27.6 MJ/kg, falling within the calorific range of sub-bituminous coal. The aqueous phase demonstrated high nitrogen concentration, reaching up to 8178 mg/L total nitrogen, while N:P:K ratios were similar to those of commercial fertilizers. Pilot scale experiments resembled the results found in laboratory scale experiments for both hydrochar and aqueous phase and fitted the regression curves obtained from the severity factor. It is postulated that hydrothermal carbonization of human excreta could potentially serve as a sustainable sanitation technology with a closed-loop cycle approach while recovering energy and nutrients. Graphical abstract Image 1 Highlights • Hydrothermal carbonization (HTC) experiments were performed with raw human excreta. • High correlation was found between severity factor and hydrochar carbon content. • Aqueous phase was nutrient-rich thus can potentially be used as liquid fertilizer. • Pilot and laboratory scale HTC reactors obtained similar results. [ABSTRACT FROM AUTHOR]

Treatment of human excreta (HE) is necessary before its discharge into natural water body. Untreated discharge may cause several ill effects for environment and human health. Anaerobic digestion of human excreta can unravel this problem along with production of biogas. Anaerobic digestion process may be either batch type or continuous type. In present study, human excreta were degraded anaerobically by both the means in the laboratory scale 5L capacity glass digesters. The comparative assessment between batch digestion and continuous digestion was carried out. The digesters were fed with human excreta at 6% Total Solids and operated at ambient temperature of 20-37°C for 99 days. The results show that average biogas production in batch feeding process is 322.78 mLday-1 whereas in continues digestion it is 382 mLday-1. Total biogas production during 99 days in batch digestion and continue digestion is 31955.1 mL and 37833.9 mL respectively. Average methane content in biogas produced in continuous and batch digestion was 68.0% and 67.4% respectively. Results conclude that human excreta can be successfully digested anaerobically to produce biogas with good methane content either by batch or continuous digestion process. [ABSTRACT FROM AUTHOR]

Infectious disease transmission is frequently mediated by the environment, where people's movements through and interactions with the environment dictate risks of infection and/or illness. Capturing these interactions, and quantifying their importance, offers important insights into effective interventions. In this study, we capture high time-resolution activity data for twenty-five Vietnamese farmers during collection and land application of human excreta for agriculture. Although human excreta use improves productivity, the use increases risks of enteric infections for both farmers and end users. In our study, the activity data are integrated with environmental microbial sampling data into a stochastic-mechanistic simulation of E . coli contamination on hands and E . coli ingested. Results from the study include frequent and variable contact rates for farmers' hands (from 34 to 1344 objects contacted per hour per hand), including highly variable hand-to-mouth contact rates (from 0 to 9 contacts per hour per hand). The frequency of hand-to-mouth contacts was substantially lower than the widely-used frequency previously reported for U.S. Office Workers. Environmental microbial contamination data highlighted ubiquitous E . coli contamination in the environment, including excreta, hands, toilet pit, handheld tools, soils, surfaces, and water. Results from the simulation suggest dynamic changes in E . coli contamination on hands, and wide variation in hand contamination and E . coli ingested amongst the farmers studied. Sensitivity analysis suggests that E . coli contamination on hands and ingested doses are most influenced by contamination of handheld tools, excreta, and the toilet pit as well as by frequency of hand-to-mouth contacts. The study findings are especially relevant given the context: no farmers reported adequate storage time of human excreta, and personal protective mask availability did not prevent hand-to-mouth contacts. Integrating high time-resolution activity data into exposure assessments highlights variation in exposures amongst farmers, and offers greater insight into effective interventions and their potential impacts. [ABSTRACT FROM AUTHOR]

Wa, a fast growing municipality in Ghana, is at the first stage of the urban environmental transition where most of the environmental problems tend to occur within or close to the home, including the management of human faecal matter. This study examined the state of faecal matter management in Wa. A stratified sample of residential areas and a systematic sampling of households were employed for the selection of respondents and data was collected using questionnaire survey and key informant interviews. The results indicate that 52% of households in the municipality do not have their own toilet facilities and open defecation appears to be an acceptable practice for them. Surprisingly, public perception about faecal matter handling generally indicates that there are no dangers posed by exposure to humans. The finding suggests a considerable demand for improvements in the management of faecal matter but efforts to improve the situation might be thwarted by misconceptions of the risks posed by exposure to humans. Local government authorities need to re-engineer their efforts of providing a liveable environment by developing a regulatory framework that incorporates subsidies for the construction of household toilets and enforcement of sanitation bye-laws. [ABSTRACT FROM AUTHOR]

A unique autothermal thermophilic aerobic digestion (ATAD) process has been used to convert human excreta to liquid fertilizer in Japan. This study investigated the changes in physicochemical and bacterial community characteristics during the full-scale ATAD process operated for approximately 3 weeks in 2 different years. After initiating simultaneous aeration and mixing using an air-inducing circulator (aerator), the temperature autothermally increased rapidly in the first 1 to 2 days with exhaustive oxygen consumption, leading to a drastic decrease and gradual increase in oxidation-reduction potential in the first 2 days, reached >50°C in the middle 4 to 6 days, and remained steady in the final phase. Volatile fatty acids were rapidly consumed and diminished in the first 2 days, whereas the ammonia nitrogen concentration was relatively stable during the process, despite a gradual pH increase to 9.3. Principal-coordinate analysis of 16S rRNA gene amplicons using next-generation sequencing divided the bacterial community structures into distinct clusters corresponding to three phases, and they were similar in the final phase in both years despite different transitions in the middle phase. The predominant phyla (closest species, dominancy) in the initial, middle, and final phases were Proteobacteria (Arcobacter trophiarum, 19 to 43%; Acinetobacter towneri, 6.3 to 30%), Bacteroidetes (Moheibacter sediminis, 43 to 54%), and Firmicutes (Thermaerobacter composti, 11 to 28%; Heliorestis baculata, 2.1 to 16%), respectively. Two predominant operational taxonomic units (OTUs) in the final phase showed very low similarities to the closest species, indicating that the process is unique compared with previously published ones. This unique process with three distinctive phases would be caused by the aerator with complete aeration. [ABSTRACT FROM AUTHOR]