In this work, valorisation pathways of brewers’ spent grains (BSG) towards biofuels production under the biorefinery concept were studied utilizing experimental data that provide a common base for straightforward comparison. The dehydration and the recovery of used oil, bioethanol and biogas from BSG were studied. The process units involved were thoroughly investigated and optimized. The oil extraction efficiency reached up to 70% using solid-liquid extraction process with hexane as solvent. The optimal ethanol yield achieved was 45% after the application of acid pretreatment, enzymatic hydrolysis with CellicCTec2 and fermentation with S. Cerevisiae. As far as biogas potential is concerned, the raw BSG, defatted BSG and stillage presented values equal to 379 ± 19, 235 ± 21 and 168 ± 39 mL biogas/g for respectively. Through the combination of the proposed schemes, three biorefinery scenarios were set up able to produce biodiesel, bioethanol and/or biogas. Material flow diagrams were set up in order to assess these schemes. Given that BSG could ensure ‘green’ energy production in the range of 4.5–7.0 million MJ/y if the European BSG potential is fully valorised, BSG could substantially contribute to the biofuel energy strategy.

Global increase in demand for food supply has resulted in surplus generation of wastes. What was once considered wastes, has now become a resource. Studies were carried out on the conversion of biowastes into wealth using methods such as extraction, incineration and microbial intervention. Agro-industry biowastes are promising sources of carbon for microbial fermentation to be transformed into value-added products. In the era of circular economy, the goal is to establish an economic system which aims to eliminate waste and ensure continual use of resources in a close-loop cycle. Biowaste collection is technically and economically practicable, hence it serves as a renewable carbon feedstock. Biowastes are commonly biotransformed into value-added materials such as bioethanol, bioplastics, biofuels, biohydrogen, biobutanol and biogas. This review reveals the recent developments on microbial transformation of biowastes into biotechnologically important products. This approach addresses measures taken globally to valorize waste to achieve low carbon economy. The sustainable use of these renewable resources is a positive approach towards waste management and promoting circular economy.

This research aims to study the wet torrefaction (WT) and saccharification of sorghum distillery residue (SDR) towards hydrochar and bioethanol production. The experiments are designed by Box-Behnken design from response surface methodology where the operating conditions include sulfuric acid concentration (0, 0.01, and 0.02 M), amyloglucosidase concentration (36, 51, and 66 IU), and saccharification time (120, 180, and 240 min). Compared to conventional dry torrefaction, the hydrochar yield is between 13.24 and 14.73%, which is much lower than dry torrefaction biochar (yield >50%). The calorific value of the raw SDR is 17.15 MJ/kg, which is significantly enhanced to 22.36–23.37 MJ/kg after WT. When the sulfuric acid concentration increases from 0 to 0.02 M, the glucose concentration in the product increases from 5.59 g/L to 13.05 g/L. The prediction of analysis of variance suggests that the best combination to maximum glucose production is 0.02 M H₂SO₄, 66 IU enzyme concentration, and 120 min saccharification time, and the glucose concentration is 30.85 g/L. The maximum bioethanol concentration of 19.21 g/L is obtained, which is higher than those from wheat straw (18.1 g/L) and sweet sorghum residue (16.2 g/L). A large amount of SDR is generated in the kaoliang liquor production process, which may cause environmental problems if it is not appropriately treated. This study fulfills SDR valorization for hydrochar and bioenergy to lower environmental pollution and even achieve a circular economy.

At present, coal is considered one of the main components for the production of cheap, high-energy and environmentally attractive slurry fuels. The latter can be produced on the basis of low-grade coal dust or coal processing wastes. Thus, coal-water slurries and coal-water slurries containing petrochemicals are produced. The involvement of coal and oil processing wastes expands the scope of raw materials, reduces the fuel costs from traditional energy sources and modifies the main economic characteristics of power plant performance. However, it also increases the impact of coal-fired thermal power stations on the environment. In the last 30–50 years, many efforts have been made to decrease the negative impact of human industrial activity on climate. Involving plant-based components in the process of energy generation to save energy and material resources looks very promising nowadays. This research studies the influence of adding typical bioliquids (bioethanol, turpentine, glycerol) on the concentration of anthropogenic emissions from coal-water slurry combustion. Relative mass concentrations of bioliquids varied in a small range below 20%. We focused on the concentration of the most hazardous sulfur and nitrogen oxides from the combustion of typical filter cakes, as well as plant-containing slurries. It was established that the concentration of sulfur oxides can be decreased (as compared to coal) by 75%, whereas that of nitrogen oxides by almost 30%. Using a generalizing criteria expression, we illustrated the main benefits of adding bioliquids to slurry fuels in comparison with coal. Adding 20% of glycerol was found to provide maximum advantages.

PURPOSE OF REVIEW: The depletion of fossil reserves and environmental challenges associated with fossil fuels are major drivers of the search for sustainable renewable energy sources. Bioethanol production from macroalgae is one of the promising alternatives to reduce use of fossil fuels and achieve energy security and ecological sustainability. The purpose of this review is to critically discuss the options to optimize the process parameters for steady production of bioethanol from macroalgae. RECENT FINDINGS: A comprehensive literature review reveals that bioethanol production from macroalgae not only depends on the macroalgae type but also on the selection of pretreatment, hydrolysis, and fermentation options. Unlike the first- and second-generation feedstocks, macroalgae contains low concentrations of glucans. Thus high bioethanol concentration cannot be achieved by converting only glucans. Therefore, it is important to produce bioethanol from other carbohydrate components of macroalgae, such as alginate, sulphated polysaccharides, carrageenan, mannitol, and agar. The selection of the right hydrolysing agents (e.g., enzyme and/or acid) and steps to minimize formation of inhibitors during the process were found to be important factors affecting the efficiency of hydrolysis process. The hydrolysis enzymes currently used were developed for lignocellulosic and starch-based biomass, not for macroalgae, which is different in polysaccharide structure and composition. Also, the lack of appropriate fermenting microorganisms capable of converting heterogeneous monomeric sugars in macroalgae is a major factor limiting bioethanol yield during the fermentation process. This review systematically discusses the implications of selecting different macroalgae types. The optimization of process parameters of different bioethanol production steps such as pretreatments, hydrolysis, and fermentation is discussed. It can be concluded that high bioethanol yield can be achieved by considering macroalgae type and composition, selecting appropriate pretreatment, hydrolysis, and fermenting microbes, and with effective bioethanol purification.

Biofuels are the cheapest source of energy, and the continuous decline of traditional sources of energy with the increasing population leads to looking for alternatives to reduce the consumption of traditional sources of energy. Bioethanol production from lignocellulosic wastes and cellulosic wastes is not a new approach for fuel production but a cheap and accessible way for the production of fuel. Bacillus is one of the major species that can act as a source of diversified enzymes. In this study, it was emphasized on screening and isolation of a novel, characterization, and best catalytic action on both celluloses and proteins in the presence of different carbon and nitrogen sources. It was observed the effective catalytic breakdown of cellulose with the crude enzyme to glucose allowed fur for fermentation with Saccharomyces, ultimately leading to the generation of alcohol. The study aims to isolate the microbes that can produce cellulases and enzymes and could be used for biodegradation to produce ethanol in the reaction. The maximum enzyme activity was achieved at 3.112 UI with optimized pH and temperature, and the maximum conversion of sugars into alcohol was about 70% in the newspaper, cartons, colored paper, and disposable paper cups. An essential observation was the decolorization of the origami craft paper within 24 hours. The study was involved in enhancing the maximum Enzyme activity of cellulases from different cellulosic raw materials. Hence, it was achieved by JCB strain, optimization of pH, temperature, and acids for the biodegradation. The presence of peaks at 3200 and 2900 was a confirmation of ethanol bonds in the biodegradation reaction mixtures.

In this study, the feasibility of banana straw (BS) hydrolysate as carbon source and reutilizing the pretreated liquor (PL) of BS in the Rhodosporidium toruloides fermentation was explored for the first time. When BS hydrolysate was used as the carbon source, total biomass concentration, lipid concentration, and lipid content under optimal conditions reached 15.52 g/L, 5.83 g/L, and 37.56% (w/w), respectively, which was similar to the results of pure sugar control. After detoxification, 50% PL can be returned to enzymatic hydrolysis and fermentation, and total biomass concentration, lipid concentration, and lipid content can reach 15.14 g/L, 5.59 g/L, and 36.91% (w/w). Then, ethanol stillage (ES) was used as the nitrogen source. The NaCl and glycerol of ES could promote lipid accumulation, reaching 7.52 g/L under optimized conditions. Finally, microbial lipid production from BS hydrolysate and ES without any additional nutrients was investigated, and the maximum total biomass concentration, lipid concentration, and lipid content were 13.55 g/L, 4.88 g/L, and 36.01% (w/w), respectively. Besides, the main compositions of microbial lipid produced were C16 and C18, and the biodiesel production from the microbial lipid could meet Chinese and US standard through theoretical numerical calculation.

The impregnation process has successfully prepared a novel composite of iron oxide/carbon from black liquor (CA-BL/Fe) as an adsorbent for the removal of tripolyphosphate ions. Black liquor is a secondary product of the bioethanol pre-treatment process. X-ray diffraction results showed that the main iron oxide species present in the CA-BL/Fe was goethite (α-FeOOH). Interestingly, the specific surface area of CA-BL/Fe was 504 m²/g higher than that of commercial activated carbon of 356 m²/g. The adsorption performance showed that tripolyphosphate ion removal efficiency increased by increasing the adsorbent dosage, pH, and contact time. At the same time, it decreased with an increase in the initial concentration of tripolyphosphate. By controlling the environment pH value, the optimum removal efficiency of tripolyphosphate ions with CA-BL/Fe was 96.87%, with the adsorption capacity of 1.5922 mg/g for 1 h measurement. In this study, the dominant mechanisms of tripolyphosphate adsorption are electrostatic attraction and ion exchange. The result of this study is expected to be the basis for further promising adsorbent material for tripolyphosphate ion.

The rapid depletion of the world’s fossil fuel reserves and global warming issues have promoted the search for sustainable alternative energy resources. In the present investigation, large-scale cultivation of naturally isolated freshwater microalgae Asterarcys quadricellulare strain was carried out using tertiary treated municipal wastewater as a growth medium in an open HRP pond for bioethanol production. A total of 12.091 kg of dry biomass was obtained at the end of the study. The lipid extracted carbohydrate rich spent microalgae biomass was converted to bioethanol by ethanolic fermentation. The biomass was first pre-treated with different concentrations of H2SO4 and HCL hydrolysis with different temperatures and reaction times. The biomass treated with a 2.0% concentration of H2SO4, showed maximum yields of glucose 308.38 mg.g-1 at 100°C with 180 min reaction time. The hydrolysates derived from the hydrolysis of microalgae biomass were used as a substrate for fermentation by using S. cerevisiae. The obtained bioethanol was analyzed using HPLC and the purity of ethanol was 90%.

In this article, sugarcane molasses and agave juice were compared as potential feedstocks for producing bioethanol in Mexico in terms of their environmental impact and economic factors. Life cycle assessment (LCA) using SimaPro was carried out to calculate environmental impacts by using a cradle-to-gate approach. A preliminary economic analysis was performed to determine the economic feasibility of the studied options. Also, capital goods costs were obtained using the Aspen Plus economy package. Moreover, a sensitivity analysis was involved to compare the environmental and economic viability of producing bioethanol from sugarcane molasses and agave juice. LCA results revealed that cultivation and fermentation were the most harmful stages when producing bioethanol from sugarcane molasses and agave juice, respectively. Furthermore, when it was derived from agave juice rather than sugarcane molasses, it had more environmental benefits. This was ascribed to the lower consumption rate of fertilizers, pesticides, and emissions given off from the former. Regarding financial aspects, the preliminary analysis showed that producing bioethanol was not economically viable when grid energy alone was used. However, if power from the grid is partially replaced with renewable energy, producing bioethanol becomes economically feasible, and sugarcane molasses is the most suitable feedstock.