Search

This study evaluates the potential of biorefinery and dairy wastewater as substrates for electricity generation in double chamber Microbial Fuel Cells (DCMFC), focusing on their microbial taxonomy and electrochemical viability. Taxonomic analysis using 16S/18S rDNA-targeted DGGE and high-throughput sequencing identified Proteobacteria as dominant in biorefinery biomass, followed by Firmicutes and Bacteriodota. In dairy biomass, Lactobacillus (77.36%) and Clostridium (15.70%) were most prevalent. Biorefinery wastewater exhibited the highest bioelectrochemical viability due to its superior electrical conductivity and salinity, achieving a voltage yield of 65 mV, compared to 75.2 mV from mixed substrates and 1.7 mV from dairy wastewater. Elevated phosphate levels in dairy wastewater inhibited bioelectrochemical processes. This study recommends Biorefinery wastewater as the most suitable purely organic substrate for efficient bioelectricity generation and scaling up of MFCs, emphasising the importance of substrate selection for optimal energy output for practical and commercial viability. [ABSTRACT FROM AUTHOR]

In the strategy to combat climate change that has been caused by the world's overdependence on fossil fuels, current research is focusing on the decarbonisation of the energy sector through the production of renewable cleaner energy, such as biofuels. Spent coffee grounds (SCGs), the waste stream of the coffee brewing industry, are a potential feedstock for the production of valuable products, including biofuels. However, the environmental implications for the valorisation of this valuable waste need to be investigated. This study assesses the environmental impacts of six biomass‐to‐fuel processing technologies using SCGs as a feedstock, with the aim of identifying the most environmentally friendly technology. A cradle‐to‐gate life‐cycle assessment (LCA) was conducted on fast pyrolysis, fermentation, anaerobic digestion (AD), hydrothermal liquefaction (HTL), gasification, and biodiesel production. The mass and energy balances obtained from Aspen Plus simulations served as the life‐cycle inventory data. Using the ReCiPe 2016 midpoint (H) and Eco‐Indicator 99 as the assessment methods, potential environmental impacts were calculated in OpenLCA software. Electricity generation and carbon dioxide emissions were the biggest contributors of environmental impacts. For each category, the maximum result was set to 100% and the results of the other variants were displayed in relation to this result. AD, with the smallest total weighted score (160), was the most environmentally friendly biomass‐to‐fuel processing route, while HTL, with the biggest total weighted score (893), was the worst. A sensitivity analysis indicated that the environmental performance of biofuel production from SCGs was highly influenced by energy input flows and the source of energy generation. [ABSTRACT FROM AUTHOR]

By promoting increased circularity through reuse, repurposing, and recycling, we can significantly reduce textile product carbon dioxide emissions by 33 %, concurrently mitigating air, land, and soil pollution associated with textile production, with chemical recycling playing a crucial role due to its ability to produce materials with comparable quality to virgin raw materials, minimizing the loss of a textiles original properties. This research investigated the chemical depolymerisation of cotton textiles, aiming to transform them into a material that closely resembles commercial dissolving pulp. The investigation focuses on comparing two pre-treatment methods, each aiming to optimise the depolymerisation process. The treated cotton material was then blended with conventional dissolving pulp, enabling the production of man-made cellulosic fibres (MMCFs) through the well-established viscose process. The successful implementation of this novel approach paves the way for incorporating recycled cotton into the viscose process and reduce dependence on virgin pulp, minimise environmental impact and promoting a more sustainable textile industry. [ABSTRACT FROM AUTHOR]

Anaerobic co-digestion (ACD) is prominent as a technology that offers a sustainable alternative energy source in biogas while contributing to sustainable waste management. However, several issues linked to process stability and performance remain, including slow anaerobe acclimation and growth. This study aimed to optimise the anaerobic co-digestion of sewage sludge and municipal landfill leachate by establishing the optimal operating conditions for ACD with biochar addition. Response surface methodology (RSM) Box-Benken design (BBD) was utilised to investigate the impact of critical process parameters: temperature, co-substrate loading rate, and Biochar loading rate on biogas yield. The response model underwent analysis of variance (ANOVA) analysis to determine the relevant elements that were accurately incorporated into the models. The model was determined to have a confidence level of 95 %. The adep accuracy, which quantifies the ratio of the signal to the noise, met the acceptable criterion of being more than 4. The ratio for Biogas Yield achieved was 15.9195. The optimum operating conditions were observed to be co-substrate loading of 1:20 (leachate; total reactor volume), BC loading of (6.7 g/L), and a temperature of 54.99 °C, achieving desirability of 94.10 %. A mean biogas yield of 60.45 mL/gVSadded was achieved under the optimum conditions. [ABSTRACT FROM AUTHOR]

Spent coffee grounds (SCG) valorisation can produce high-value products to supply cosmetics, petroleum and pharmaceutical industries among others. An overview of the various products achievable from spent coffee grounds valorisation are established, while the effect of temperature, reaction time and solid-to-liquid loading ratio on the yield of caffeine extracted from SCG was investigated. The best extraction solvent between (i) dichloromethane, (ii) 1-ethyl-3-methylimidazolium chloride (IL) and (iii) water was established. Characterisation of SCG using Technical Association of the Pulp and Paper (TAPPI) methods was carried out. Variations of parameters were established using the Box-Behnken design of experiment (DOE) which varied the investigated parameters; (i) temperature (88 - 120 °C), (ii) reaction time (15 - 35 min) and (iii) solid-to-liquid loading ratio (5 g SCG per 10 -25 mL). The conventional extraction method used dichloromethane as the extraction solvent, whereas the green method used the ionic liquid and water in a Parr pressure reactor. High performance liquid chromatography (HPLC) quantified the yield of extracted caffeine. Recrystallised caffeine is analysed using scanning electron microscopy (SEM), transition electron microscopy (TEM) and energy dispersive spectroscopy (EDS) for its structural properties, crystalline structure and physical analysis, while differential scanning calorimetry (DSC) established the purity of extracted caffeine achieved from each extraction solvent. The expected yield of caffeine is between 4.67 and 8.0 mg/g SCG. According to this experimental methodology, at 120 °C, 25 min reaction time and 25 mL solvent volume the extraction yield ranged from 2.83 to 3.67 mg/g SCG. [ABSTRACT FROM AUTHOR]

Spent coffee grounds (SCGs) are a renewable source that can be converted into different types of biofuels or chemicals. Recent research has focused on the examination of a two-step bioconversion process that involves;1) extraction of fermentable sugars from SCGs, and 2) conversion of sugars into fuels and/or chemicals by microbial fermentation. The capability of SCGs as a source of fermentable sugars has not been fully realised, due to their complex structure. Which makes the depolymerisation of the SCGs into its component monomeric sugars relativity difficult. The use of ionic liquids (ILs) as green solvents is an attractive alternative for the pretreatment of lignocellulosic biomass such as SCGs. It has been shown that pre-treatment with imidazoliumbased ILs containing anions such as chloride, acetate, and alkyl phosphate can greatly speed up the subsequent enzymatic hydrolysis of lignocellulosic biomass. The present investigated the use of 1-Butyl-3-methylimidazolium chloride as a green solvent for the extraction of sugars from SCGs for the production of bioethanol. The maximum concentration of sugars extracted was 22.55 wt% of mannose in 100 g of SCGs, galactose, 15 wt% of galactose in 100 g of used, 9.81 wt% glucose in 100 g of SCGs, 6.36 wt% arabinose and 10.46 wt% of, sucrose in 100 g of dry SCGs used. Mannose yield was prominent in all runs, the high content of this sugar causes difficulty in bioethanol production but is advantageous in the production of itaconic acid. [ABSTRACT FROM AUTHOR]

Some industrial wastewaters contain high levels of non-biodegradable organic and inorganic matter, and inhouse physical and chemical treatment produces secondary pollutants that are released into the receiving environment and can harm the ecosystem. Over the years, conventional biological treatment of these industrial effluents has proven ineffective. Advanced biological aerobic and anaerobic methods, in which biomass is nurtured for growth and biochemical manipulations are used to present a variety of value-added products with potential applications, have been adopted. As CO2 gas is sparged through the broth, the microalga Scenedesmus sp. accumulates lipid as it mops up minerals and nutrients from brewery wastewater to produce biomass. Standard methods were used to determine the mineral content of brewery wastewater from Durban, KwaZulu-Natal. Scenedesmus sp. was then grown in wastewater using bubble-column photobioreactors, with the broth being CO2-sparged at regular intervals. The optical density reading on the DR 3900 spectrophotometer was used to track biomass production, and lipid accumulation was measured using the chloroform-methanol solvent system. The findings revealed that the minerals in the effluent brewery wastewater contained high levels of cadmium, exceeding the WHO limit of 0.03 mg/L. Zinc (1.578 mg/L) and nickel (0.053 mg/L) concentrations were both within WHO limits of 5.0 mg/L and 1.0 mg/L, respectively. All of the minerals in the effluent were significantly reduced after treatment with Scenedesmus sp. As a result, during the exponential growth period, biomass production increased in tandem with proportional lipid accumulation. [ABSTRACT FROM AUTHOR]

Sugar industry is one the biggest contributors to the environmental pollution in the modern world. The effects are specifically felt by the aquatic environment which in turn affects the human beings as they depend (partially and otherwise) on the aquatic creatures such as fish for food resource. Also, water demands are growing continually as human population increases although the supply of water is diminishing. The disposal of the effluent from industries to water streams becomes detrimental as it does not only disturb the aquatic life but also the water quality that is used for domestic and agricultural purposes. Effluent discharging industries include thermal power plants, paper mills, oil refineries, sugar mills etc. The composition of this effluent is total suspended solids, chemical oxygen demand, biological oxygen demand, heavy metals and sometimes the total dissolved solids. Treatment and reuse of industrial effluent (wastewater) then becomes a necessary step to meeting the environmental strain. One way of effectively solving the crisis of industrial wastewater is through treating while making additional useful products such as biogas and electricity. The aim of the present paper is to do a thorough analysis of the effluent from sugar milling industry for production of biogas and electricity through anaerobic digestion. [ABSTRACT FROM AUTHOR]

The present study focused on the optimisation of production of fuel-grade hydrocarbons using lipids or oil extracted from spent coffee grounds (SCGs). The oil was extracted from SCGs using 2-methyltetrahydrofuran as a green solvent and calcium oxide synthesised from chicken eggshells was used as a green catalyst during the SCGs oil transesterification. Calcium oxide was doped with lithium (Li-CaO(s)) to improve catalyst activity. The oil extraction and the transesterification processes were optimised using the design of experiment (DoE). The response surface methodology (RSM) and the Box-Behnken design were used to optimise both processes. The combination of extraction time and solvent-to-solids ratio were optimised for the oil extraction process. The combination of reaction time and catalyst loading were optimised for the transesterification process. Fourteen 14 experiments were predicted by Box-Behnken design for both the oil extraction and transesterification processes. The model predicted that the optimum extraction conditions were, 1:18 (w/v) SCGs-to-solvent ratio and 4.5 h extraction period, providing a maximum of 25.10 wt% oil yield. The model predicted optimal yield was confirmed experimentally, obtaining an oil yield of 24.60 wt%, which was 0.5 wt% lower than the value predicted by the model. During transesterification the reactor temperature was maintained at 65 °C, a SCGs oil-tomethanol molar ratio of 1:12 and 165 rpm mixing speed. The model predicted the optimum reaction time of 2 h, 5 wt% of the oil used catalyst loading, providing 98.21 wt % oil conversion. The predicted optimal yield was confirmed experimentally, achieving an oil conversion of 97.81 wt%, which was 0.4 wt% lower than the predicted by the model. [ABSTRACT FROM AUTHOR]

The present study assessed the recycling of spent coffee grounds (SCG) as a perspective source of oil which can be used as a feedstock for the production of fuel-grade hydrocarbons or Fatty Acid Methyl Esters (FAME). Traditionally, hexane is used for the recovery of lipids from lipids bearing seeds. The challenge is finding novel solvent/solvents which are derived from renewable materials but with the same or improved oil extraction efficiency than the traditional solvents such as hexane. One such solvent is 2-methyltetrahydrofuran (2-MeTHF), which is produced from renewable lignocellulosic materials. This investigation aimed to assess the capability of 2-MeTHF as a novel green solvent for the recovery of lipids from SCG employing a Soxhlet extraction system and to investigate the effectiveness of the lipid extraction process. Hexane was used as a reference solvent to measure the oil extraction capability of 2-MeTHF. The effect of the solvent-to-SCG ratio and the effect of oil recovery time on the oil yield were investigated. The SCG were characterised with regard to moisture content and particle size, and they were found to contain 66.23 wt% water, on average and a particle size of 481.22 µm on average. The lipid extraction process was carried out for 8 h using both hexane and 2-MeTHF, at a solvent-to-SCG ratio of 15:1 (% w/v), producing an oil yield of 18.99 wt% for hexane and 27.95 wt% for 2-MeTHF on average. The density of the oil extracted using 2-MeTHF was 1162.83 kg/m3 and kinematic viscosity of 37.67 mm2/s on average. The average free fatty acid content (FFA) of the oil extracted using 2-MeTHF was found to be 4.54 wt% and the saponification value (SV) of the oil was found to be 170.22 mg KOH/g. These values were relatively higher than those obtained for the oil extracted using hexane [ABSTRACT FROM AUTHOR]