A pressing concern of issues such as climate change has drawn main attention in the world.The burning of fossil fuels by human due to increasing energy demand in various sectors is one of the main factors that influence the climate change.This has resulted in the introduction of many renewable energy sources as alternatives to fossil fuels.Biogas is one type of renewable energy that has numerous advantages.The present review covers the recent challenges of biogas production and its conversion to electrical energy.This includes the substrates used, the operating parameters, and the pre-treatment used, which can be implemented to maximise the biogas yield.The challenges and potential of the generation of electricity from biogas were also discussed in this review.The results obtained in this review emphasise that biogas is a good renewable energy, as it solves multiple problems and at the same brings benefits to human beings in many ways.
A pilot scale granular activated carbon-sequencing batch biofilm reactor with a capacity of 2.2 m3 was operated for over three months to evaluate its performance treating real recycled paper industry wastewater under different operational conditions. In this study, dissolved air floatation (DAF) and clarifier effluents were used as influent sources of the pilot plant. During the course of the study, the reactor was able to biodegrade the contaminants in the incoming recycled paper mill wastewater in terms of chemical oxygen demand (COD), adsorbable organic halides (AOX; specifically 2,4-dichlorophenol (2,4-DCP)) and ammoniacal nitrogen (NH3-N) removal efficiencies at varying hydraulic retention times (HRTs) of 1–3 days, aeration rates (ARs) of 2.1–3.4 m3/min and influent feed concentration of 40–950 mg COD/l. Percentages of COD, 2,4-DCP and NH3-N removals increased with increasing HRT, resulting in more than 90% COD, 2,4-DCP and NH3-N removals at HRT values above two days. Degradation of COD, 2,4-DCP and NH3-N were seriously affected by variation of ARs, which resulted in significant decrease of COD, 2,4-DCP and NH3-N removals by decreasing ARs from 3.4 m3/min to 2.1 m3/min, varying in the ranges of 24–80%, 6–96% and 5–42%, respectively. In comparison to the clarifier effluent, the treatment performance of DAF effluent, containing high COD concentration, resulted in a higher COD removal of 82%. The use of diluted DAF effluent did not improve significantly the COD removal. Higher NH3-N removal efficiency of almost 100% was observed during operation after maintenance shutdown compared to normal operation, even at the same HRT of one day due to the higher dissolved oxygen concentrations (1–7 mg/l), while no significant difference in COD removal efficiency was observed.
Cooling powder is a traditional local cosmetic product produced from natural fermentation of rice. This product has been passed down until today due to its beneficial properties and is believed to have a cooling effect on the user. In current market, this product is still being sell in its traditional form which is in the form of powder and beads which are difficult to use. At the same time, there are concerns regarding safety talc-based cosmetics due to its potential contamination with asbestos, a toxic mineral. Therefore, this study is conducted to modernize this increasingly forgotten traditional product into a compact powder and replace the talc composition with cooling powder. Binding agents and oil absorbing agents are added to produce better quality of compact powder. The objective of this study is to determine the best composition of powder, binding agent and oil absorbing agent for compact powder formulations by using Response Surface Methodology (RSM), where Central Composite Design (CCD) is utilized. The cooling powder composition studied for the compact powder formulation are 50%, 55% and 60%. Meanwhile, kaolin is added as oil absorbing agent with compositions of 20%, 25% and 30%. Virgin coconut oil is added as binding agent at varied composition of 5%, 7.5% and 10%. Two types of drop tests are carried out to investigate the durability of the compact powder formulation, which are weight and height drop tests. Oil absorption capacity test is performed to evaluate the effectiveness of the compact powder formulations in absorbing oil.
Biogas-fed proton exchange membrane fuel cell (PEMFC) plants offer a sustainable energy solution, but their operation can pose significant hazards and risks. Ensuring the safety of these plants is paramount, especially given the potential for fires, explosions, and chemical exposures. This study evaluated hazards and risks in biogasfed proton exchange membrane fuel cell (PEMFC) plants using six analytical methods: Dow's fire and explosion index (FEI), Dow's chemical expo-sure index (CEI), Hazard and Operability Study (HAZOP), Risk Matrix Analysis (RMA), Bayesian Network (BN) and ALOHA® software hazard modelling. The FEI analysis revealed that the anaerobic digester and bio-gas storage tank exhibited severe hazards (FEI =170), thereby signifying the highest risks within the plant. CEI analysis revealed the spread of the highest hydrogen sulfide (H2S) concentration up to 129 meters from the anaerobic digester and storage tank location. Further assessment was conducted, calculating risk values using the RMA and performing additional HAZOP analysis specifically for these units. The results confirmed similar risk levels (4-20) between the units, except for a higher explosion risk in the storage tank. The novelty of this research lies in the application of Bayesian Network (BN) analysis. In addition to assessing the hazards associated with PEMFC, our BN analysis reveals that the risk of fire attributed to PEMFC ranges between 10% and 18%, while the risk of explosion falls within the range of 3% to 17%. Based on the hierarchy control concept, several effective mitigation controls were proposed to enhance the safety of biogas-fed PEMFC plants. In future research, a deeper exploration of human error and equipment malfunctions within hazard modelling is crucial for a more precise hazard assessment.
Recycled paper industry wastewater generates potentially persistent and toxic pollutants which can affect the ecological balance and cause aesthetic concerns.In this study, the biodegradability of recycled paper mill wastewater by a granular activated carbonsequencing batch biofilm reactor (GAC-SBBR) pilot plant system during a period of 53 days was evaluated while on-line monitoring was used to observe the influence of parameter changes during the treatment process.The effect of nitrogen (N) and phosphorus (P) addition on removal of chemical oxygen demand (COD) in four phases was investigated.The COD:N:P ratio in the nutrient medium was considered as an independent variable at a fixed value hydraulic retention time (HRT) of 24 hours.The study demonstrated that the process was unstable during the initial phase and started to stabilise during the last phase when a COD:N:P ratio of about 100:5:1 was achieved.Degradation of COD was seriously affected by variation of COD:N:P ratios, resulting in the highest removal efficiency of COD at COD:N:P ratio of 100:5:1 (80.1 %) and a minimum degradation at COD:N:P ratio of 1000:7:0.2(33.8 %).Using the Monod model, the kinetic parameters (µ m , K s , Y and K d ) were determined as 0.1007 mg MLSS/mg COD.day, 65.917 mg COD/L, 0.5199 mg MLSS/mg COD and 0.0048 mg MLSS/mg COD.day, respectively.These findings can be used to improve the performance of the pilot GAC-SBBR system.
Dyes are considered to be hazardous, have low biodegradability and can affect the human health as well as the aquatic life cycle.This research investigated the methylene blue (MB) removal using an activated carbon matrix of Scirpus grouss (waste that was initially used for phytoremediation of soil).The experiment was conducted in a flask containing 0.5 g AC-SC with MB concentrations of 5 and 15 mg/L.The adsorption was monitored for 120 sec.The results showed complete removal of MB within a contact time of 30 sec using 6-AC.The surface morphology analysis showed that at 6-AC, the structure was more porous.The ultimate potential of activated carbon prepared from the phytoremediation plant waste would be the best alternative for the water and wastewater treatment, while it provides an alternative to the phytoremediation waste management process.
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