Utilization of carbon-based nanomaterials for wastewater treatment and biogas enhancement: A state-of-the-art review.

The management of environmental pollution and carbon dioxide (CO2) emissions is a challenge that has spurred increased research interest in determining sustainable alternatives to decrease biowaste. This state-of-the-art review aimed to describe the preparation and utilization of carbon-based nanomaterials (CNM) for biogas enhancement and wastewater contaminant (dyes, color, and dust particles) removal. The novelty of this review is that we elucidated that the performance of CNMs in the anaerobic digestion (AD) varies from one system to another. In addition, this review revealed that increasing the pyrolysis temperature can facilitate the transition from one CNM type to another and outlined the methods that can be used to develop CNMs, including arc discharge, chemical exfoliation, and laser ablation. In addition, this study showed that methane (CH4) yield can be slightly increased (e.g. from 33.6% to 60.89%) depending on certain CNM factors, including its type, concentration, and feedstock. Temperature is a fundamental factor involved in the method and carbon sources used for CNM synthesis. This review determined that graphene oxide is not a good additive for biogas and CH4 yield improvement compared with other types of CNM, such as graphene and carbon nanotubes. The efficacy of CNMs in wastewater treatment depends on the temperature and pH of the solution. Therefore, CNMs are good adsorbents for wastewater contaminant removal and are a promising alternative for CO2 emissions reduction. Further research is necessary to determine the relationship between CNM synthesis and preparation costs while accounting for other factors such as gas flow, feedstock, consumption time, and energy consumption.

Haitians' perceptions of biogas produced via human excreta: An approach to the democratization of energy systems.

The utilization of organic matter (OM) to produce biogas is an attractive alternative for promoting sustainable development, addressing energy shortages and waste disposal problems, creating jobs, and investing in sanitation systems. Thus, this alternative is becoming increasingly important in developing countries. This study investigated the perceptions of residents in Delmas district, Haiti, regarding the use of biogas produced via human excreta (HE). A questionnaire containing closed- and open-ended questions was administered for this purpose. Sociodemographic aspects had no influence on locals' willingness to use biogas produced via different types of OM. The novelty of this research is that democratization and decentralization of the energy system are possible in the Delmas district using biogas produced from various organic wastes. Socio-characteristics of the interviewees did not influence their willingness towards a possible adopt biogas-based energy from several types of degradable organic matter. The results showed that more than 96% of the participants agreed that HE could be used to produce biogas and reduce energy shortages in their locality. In addition, 93.3% of the interviewees thought this biogas could be utilized for cooking food. However, 62.5% of respondents argued that using HE to produce biogas could be dangerous. Bad smell and fear of biogas produced via HE are the major concerns of users. In conclusion, this research could guide stakeholders' decisions to better address the problems of waste disposal and energy shortages and to create new jobs in the target study area. The research findings could help decision-makers better understand the willingness of locals to invest in household digester programs in Haiti. Further research is required to investigate farmers 'willingness to use digestates from biogas production.

Advancement of biochar-aided with iron chloride for contaminants removal from wastewater and biogas production: A review.

The use of fossil fuels, emission of greenhouse gases (GHG) into the atmosphere, and waste pose a problem to the environment and public health that urgently needs to be dealt with. Among numerous chemical activating agents that can be added to anaerobic digestion (AD) to enhance nutrient removal and increase the quality and quantity of biomethane, iron chloride (FeCl3) is the one that has the lowest cost and is the most environmentally friendly. This state-of-the-art review aims to revise the influence of FeCl3 on the Brunauer-Emmett-Teller (BET) surface area of biochar and its ability to increase methane (CH4) yield and remove contaminants from biogas and wastewater. The novelty of the study is that FeCl3, an activating agent, can increase the BET surface area of biochar, and its efficacy increases when combined with zinc chloride or phosphoric acid. Regarding the removal of contaminants from wastewater and biogas, FeCl3 has proven to be an effective coagulant, reducing the chemical oxygen demand (COD) of wastewater and hydrogen sulfide in biogas. The performance of FeCl3 depends on the dosage, pH, and feedstock used. Therefore, FeCl3 can increase the BET surface area of biochar and CH4 yield and remove contaminants from wastewater and biogas. More research is needed to investigate the ability of FeCl3 to remove water vapor and carbon dioxide during biogas production while accounting for a set of other parameters, including FeCl3 size.