Search Results (72)

This study investigated the enhancement of an acetone–butanol–ethanol (ABE) fermentation from sugarcane molasses using Clostridium beijerinckii TISTR 1461 immobilized on lotus stalk (LS) pieces. The addition of 0.01 g/L of ZnSO₄, MnSO₄ or FeSO₄ into the molasses medium containing 50 g/L of sugar negatively impacted butanol production. However, incorporating 2.2 g/L of ammonium acetate as a buffer increased the butanol concentration (P_B), ABE concentration (P_ABE), and butanol productivity (Q_B) by 8–11%. Optimization of the initial sugar concentration in batch mode showed that 80 g/L yielded the highest P_B (19.65 g/L) and Q_B (0.55 g/L·h). To further improve the butanol production efficiency, two strategies were employed: fed-batch process and gas stripping (GS) for product recovery. Integrating a GS system into the batch process increased the P_B (22.26 g/L), and Q_B (0.61 g/L·h) by ~11–13%. In a fed-batch mode (an initial sugar concentration of 50 g/L at 50% of the total working volume), feeding a medium at 150 g/L (corresponding to a total sugar concentration in all media of 100 g/L), a feeding time of 3 h and feeding rate of 25 mL/h achieved the highest P_B and Q_B. The most effective results were obtained by combining a fed-batch culture with a GS system, which boosted the total P_B to 23.04 g/L, P_ABE to 35.91 g/L and Q_B to 0.64 g/L·h with a butanol yield of 0.30 g/g. These values are a 14–15% improvement over the non-GS fed-batch process. The study findings demonstrate that utilizing LS as a low-cost immobilization carrier, coupled with product recovery (GS) in batch/fed-batch modes, significantly improves butanol production efficiency. Full article

Under the dual-carbon goals, adopting renewable alternative fuels in transportation is crucial. Alcohol-based fuels, produced via biomass fermentation or green electricity-powered CO₂ hydrogenation, offer benefits like renewability, engine compatibility, and long driving range. Bio-butanol, with an energy density close to gasoline, can power SI engines directly, but its high production costs due to low fermentation efficiency limit its viability. In contrast, IBE (a butanol fermentation intermediate) avoids costly separation steps, making it more competitive than pure butanol. Existing research on IBE in spark ignition engines mainly focuses on fixed-ratio IBE-gasoline blends, restricting real-time fuel adjustment. Building on prior findings that IBE outperforms ABE and butanol, this study examines the combustion and emission characteristics of a gasoline port injection + IBE direct injection engine under varying direct injection timings, IBE ratios, and excess air ratios. Research indicates that early direct injection timings with pure IBE provide optimal performance at stoichiometric conditions. As the excess air ratio rises, an 80% IBE direct injection ratio becomes more advantageous. IBE shows great promise as an alternative fuel, enhancing combustion performance and reducing gaseous and particulate emissions. Full article

Issues related to the environmental safety of transport vehicles, the operation of which leads to environmental pollution, continue to be highly relevant. In this work, we consider the use of biofuel mixed with diesel fuel for internal combustion engines operating at low temperatures. This approach does not reduce the efficiency of transport, while also solving the issue of organic waste recycling. In this work, we address the possibility of reducing environmental pollution using carbon-neutral blended fuels based on esters of waste cooking oil (WCO), biobutanol, and diesel fuel for transport, tractor, and other equipment powered by a diesel internal combustion engine. In terms of the rate of biofuel implementation, Russia is still lagging behind the EU, China, and Japan, largely due to, inter alia, its climatic conditions with cold and long winters. The article also provides data on the possibility of using mixed biofuels under sub-zero temperatures. The process of forming a volumetric fuel supply through the common rail injector of the D4CB engine under changes in fuel pressure and drive pulse duration was also investigated, with the corresponding regression dependencies being presented. The losses of heat supplied into the cylinder when using a blend of diesel fuel and biodiesel (with 20 wt% butanol) in comparison with diesel fuel were analytically calculated. This made it possible to identify a function for adjusting fuel supply to compensate for power losses. The lubricity of fuel blends was assessed using the HFRR method. Full article

Combining biobutanol and oxyhydrogen in an SI engine can reduce fossil-fuel use and improve power, but oxyhydrogen increases NOx. Without sacrificing combustion stability, this work investigates lean–burn coupled with exhaust gas recirculation for a gasoline port injection + biobutanol direct injection + oxyhydrogen in-cylinder negative pressure indraft engine, across five oxyhydrogen flow levels, four exhaust gas recirculation ratios, and three excess air ratios. Results show that with lean–burn + exhaust gas recirculation, oxyhydrogen more effectively lowers the coefficient of variation of indicated mean effective pressure and increases indicated mean effective pressure, peak cylinder pressure, and peak heat release rate. With 16 L/min oxyhydrogen, the negative effects of 6–12% exhaust gas recirculation on CA 0–10 and CA 10–90 are mitigated for all excess air ratios, and the crank angle corresponding to peak pressure remains optimal under lean conditions when 6% ≤ exhaust gas recirculation ≤ 12%. Oxyhydrogen reduces CO and HC after exhaust gas recirculation, while lean–burn dominates CO reduction. Exhaust gas recirculation suppresses NO more than lean–burn. At 1.1 ≤ excess air ratios ≤ 1.2, the optimal exhaust gas recirculation is 12%, ensuring favorable in-cylinder conditions. Overall, lean–burn + exhaust gas recirculation effectively controls NO and maximizes thermal efficiency and renewable-fuel substitution. The optimal strategy is “oxyhydrogen = 16 L/min, exhaust gas recirculation = 12%, 1.1 ≤ excess air ratios ≤ 1.2”. Full article

Butanol is currently produced on an industrial scale, primarily from fossil-based raw materials. An alternative method involves gas fermentation. To improve the efficiency of microbial processes, one promising approach is electrofermentation, which involves the application of an electric current to stimulate microbial growth or modulate metabolic pathways. This study examined the production of biobutanol from gas fermentation supported by electrofermentation, as assessed through a Life Cycle Assessment (LCA). The LCA was conducted for a biobutanol production technology developed within the framework of the BesTECH project, funded in the ERA-NET Bioenergy programme. Two environmental impact assessment methods were applied: ReCiPe 2016 and IPCC 2021 GWP 100 (with CO₂ absorption considered). The results of the LCA indicated that the most significant environmental impact is associated with greenhouse gas emissions from fossil fuel combustion used to generate electricity (based on Austria’s energy mix). An additional environmental burden is related to the production of the fermentation medium. Sensitivity analysis revealed that the environmental performance of the process is strongly influenced by the source of electricity used in biobutanol production. Full article

Biobutanol can be obtained by fermentation of microorganisms and used as biofuel. The membrane separation is energetically favorable. The incorporation of butanol into syndiotactic polystyrene (sPS) with crystalline nanopores was investigated as a function of the butanol uptake temperature using infrared spectroscopy. The OH stretching modes at 3596 and 3300 cm⁻¹, corresponding to hydrogen-bonded butanol in the crystalline cavity and free butanol in the amorphous region, respectively, were employed for analysis. Upon immersion of the sPS film in butanol, butanol molecules were absorbed in the crystalline nanocavities and amorphous phase. Diffusion increased with the uptake temperature in both regions. This can be associated with the larger molecular mobility of butanol molecules at high temperatures, facilitating contact between the film surface and the butanol molecules. The number of butanol molecules incorporated into the crystalline cavity was estimated using Lambert-Beer’s law. On average 90% of the nanopore cavities were occupied by butanol, while the remaining 10% were empty. Full article

This review synthesizes recent research on alternative fuels for piston-engine aircraft and related propulsion technologies. Biofuels show substantial promise but face technological, economic, and regulatory barriers to widespread adoption. Among liquid options, biodiesel offers a high cetane number and strong lubricity yet suffers from poor low-temperature flow and reduced combustion efficiency. Alcohol fuels (bioethanol, biomethanol) provide high octane numbers suited to high-compression engines but are limited by hygroscopicity and phase-separation risks. Higher-alcohols (biobutanol, biopropanol) combine favorable heating values with stable combustion and emerge as particularly promising candidates. Biokerosene closely matches conventional aviation kerosene and can function as a drop-in fuel with minimal engine modifications. Emissions outcomes are mixed across studies: certain biofuels reduce NO_x or CO, while others elevate CO₂ and HC, underscoring the need to optimize combustion and advance second- to fourth-generation biofuel production pathways. Beyond biofuels, hydrogen engines and hybrid-electric systems offer compelling routes to lower emissions and improved efficiency, though they require new infrastructure, certification frameworks, and cost reductions. Demonstrated test flights with biofuels, synthetic fuels, and hydrogen confirm technical feasibility. Overall, no single option fully replaces aviation gasoline today; instead, a combined trajectory—biofuels alongside hydrogen and hybrid-electric propulsion—defines a pragmatic medium- to long-term pathway for decarbonizing general aviation. Full article

This study focuses on determining the optimal fig and butyric acid concentrations for butanol production under thermophilic conditions. Waste fig is a potentially rich substrate in sugars, minerals, and vitamins, but it is insufficient for effective butanol formation when butyrate is not present in the media because butanol is produced by butyrate reduction. Therefore, butyric acid was supplemented gradually in certain concentrations to fig-containing fermentation broth. The best combination of butyric acid and fig was determined using the Box–Wilson statistical experiment design. Fig and butyric acid concentrations were set as independent variables, while butanol concentration was the objective function. When the concentrations of butyric acid and fig were near the middle of the ranges under inspection, more butanol was produced. Butanol production was the lowest as fig and butyric acid values got closer to the extremes, particularly at high concentrations. Maximum butanol of 0.32 g/L was obtained with 16 g fig/L and 1.6 g butyric acid/L. The quadratic model generated was found to be significant, and its reliability was tested with verification experiments with reproducible results. This study showed that butanol could be produced from butyrate-supplemented fig waste under thermophilic conditions with a consolidated bioprocessing approach. Full article

The industrial potential of Clostridium beijerinckii for acetone–butanol–ethanol (ABE) fermentation is limited by oxygen sensitivity and suboptimal solvent productivity. Peroxide repressor (PerR), a key negative regulator protein, is reported to suppress the oxidative stress defense system in anaerobic clostridia, leading to poor survival of bacteria under aerobic conditions. However, the regulatory mechanism underlying this phenomenon remains unclear. This study demonstrates that targeted deletion of perR (Cbei_1336) in the solvent-deficient strain C. beijerinckii DS confers robust oxygen tolerance and enhances ABE fermentation performance. The engineered perR mutant exhibited unprecedented aerobic growth under atmospheric oxygen (21% O₂), achieving a (3.79 ± 0.09)-fold increase in biomass accumulation, a (2.84 ± 0.12)-fold improvement in glucose utilization efficiency, a (57.23 ± 0.01)-fold elevation in butanol production, and a (32.78 ± 0.02)-fold amplification in acetone output compared to the parental strain. Transcriptomic analysis revealed that perR knockout simultaneously upregulated oxidative defense systems and activated ABE pathway-related genes. This genetic rewiring redirected carbon flux from acidogenesis to solventogenesis, yielding a (9.64 ± 0.90)-fold increase in total solvent titer (15.61 ± 0.89 vs. 1.62 ± 0.12 g/L) and a (2.71 ± 0.04)-fold rise in volumetric productivity (0.19 ± 0.01 vs. 0.07 ± 0.01 g/L/h). Our findings establish PerR as a master regulator of both oxygen resilience and metabolic reprogramming, providing a scalable engineering strategy for industrial oxygen-tolerant ABE bioprocessing toward low-cost biobutanol production. Full article

The production of biobutanol from lignocellulosic biomass is a promising route toward sustainable biofuels, but current research is limited due to the use of commercial simulation tools, incomplete process modeling, and insufficient variation in available feedstock. The current work addresses these gaps by developing and evaluating a complete process simulation for biobutanol production using the open-source software DWSIM. A process flow diagram was established based on a comprehensive literature review, and relevant experimental data were collected to guide simulation inputs and validate results. Six process configurations were developed, using dilute acid and autohydrolysis as pretreatment methods, and assessed based on parameters such as feedstock composition, conversion efficiency, and enzymatic hydrolysis performance. Simulation results show that DWSIM effectively models key stages of biobutanol production and accommodates variations in pretreatment and hydrolysis conditions. Processing solid fractions of pretreated biomass yields higher biobutanol concentrations than using liquid prehydrolysate alone, and the efficiency of enzymatic hydrolysis strongly influences the final output. This work demonstrates that DWSIM is a viable platform for simulating biofuel processes and offers a flexible, cost-effective alternative for early-stage process development, followed by process design with implications for future biorefinery integration and technology scaling. Full article

Developing a more efficient, cleaner, and energy-saving pretreatment process is the primary goal for lignocellulosic biofuels production. This study demonstrated the feasibility of circulating high-concentration acetone–butanol–ethanol (ABE) obtained via in situ product recovery (ISPR) as a pretreatment liquor. Taking ABE solvent separated from pervaporation (PV) and gas stripping (GS) as examples, results indicated that under dilute alkaline (1% NaOH) catalysis, the highly recalcitrant lignocellulosic matrices can be efficiently depolymerized, thereby improving fermentable sugars recovery in saccharification stage and ABE yield in subsequent fermentation stage. Results also revealed delignification of 91.5% (stream from PV) and 94.3% (stream from GS), with total monosaccharides recovery rates of 56.5% and 57.1%, respectively, can be realized when using corn stover as feedstock. Coupled with ABE fermentation, mass balance indicated a maximal 106.6 g of ABE (65.8 g butanol) can be produced from 1 kg of dry corn stover by circulating the GS condensate in pretreatment (the optimized pretreatment conditions were 1% w/v alkali and 160 °C for 1 h). Additionally, technical lignin with low molecular weight and narrow distribution was isolated, which enabled further side-stream valorisation. Therefore, integrating ISPR product circulation with lignocellulosic biobutanol shows strong potential for application under the concept of biorefinery. Full article

Biobutanol is becoming more relevant as a promising alternative biofuel, primarily due to its advantageous characteristics. These include a higher energy content and density compared to traditional biofuels, as well as its ability to mix effectively with gasoline, further enhancing its viability as a potential replacement. A viable strategy for attaining carbon neutrality, reducing reliance on fossil fuels, and utilizing sustainable and renewable resources is the use of biomass to produce biobutanol. Lignocellulosic materials have gained widespread recognition as highly suitable feedstocks for the synthesis of butanol, together with various value-added byproducts. The successful generation of biobutanol hinges on three crucial factors: effective feedstock pretreatment, the choice of fermentation techniques, and the subsequent enhancement of the produced butanol. While biobutanol holds promise as an alternative biofuel, it is important to acknowledge certain drawbacks associated with its production and utilization. One significant limitation is the relatively high cost of production compared to other biofuels; additionally, the current reliance on lignocellulosic feedstocks necessitates significant advancements in pretreatment and bioconversion technologies to enhance overall process efficiency. Furthermore, the limited availability of biobutanol-compatible infrastructure, such as distribution and storage systems, poses a barrier to its widespread adoption. Addressing these drawbacks is crucial for maximizing the potential benefits of biobutanol as a sustainable fuel source. This document presents an extensive review encompassing the historical development of biobutanol production and explores emerging trends in the field. Full article

After a brief characterisation of lignocellulosic biomass (LCB) in terms of its biochemical structure and the pretreatment techniques used to disrupt lignin structure and decrystallise and depolymerise cellulose, this review considers five main pathways for biochemical biomass conversion: starting with anaerobic digestion to convert various LCB feedstocks into bioproducts; considering the integration of biochemical and thermochemical processes, syngas fermentation, which has been recently developed for biofuel and chemical production, is reviewed; the production of 2G bioethanol and biobutanol from LCB waste is discussed; the literature on biohydrogen production by dark fermentation, photofermentation, and bioelectrochemical processes using microbial electrolysis cells as well as hybrid biological processes is reviewed. The conclusions and future prospects of integrating biochemical and thermochemical conversion processes of biomass are discussed and emphasised. Full article

The growing advocacy for greener climates, coupled with increasing global energy demand driven by urbanization and population growth, highlights the need for sustainable solutions. Repurposing food wastes as substrates offers a promising approach to enhancing cleaner energy generation and promoting a circular economy. This study investigated the potential of spent coffee grounds (SC) and biosolids cake (BS) from tea wastes as substrates for producing valuable fuels and chemicals through acetone–ethanol–butanol (ABE) fermentation. Clostridium beijerinckii NCIMB 8052 was used to ferment 100% and 50% hydrolysates derived from Parr-treated enzyme-hydrolyzed (PEH, PEH50), Parr-treated non-hydrolyzed (PNEH, PNEH50), and non-Parr-treated hydrolyzed (NPEH) SC wastes, as well as enzyme-hydrolyzed (BSH, BSH50) and non-hydrolyzed BS wastes (NBH, NBH50). Fermentation of unmodified hydrolysates by C. beijerinckii was poor. Following CaCO₃ modification of SC and BS hydrolysates, ABE titer, yield, and productivity increased, with the highest values obtained with PEH50 and NBH. Specifically, CaCO₃ modification of SC hydrolysates led to increased butanol titer, yield, and productivity in PEH50, while the NBH exhibited higher butanol yield and productivity than the non-CaCO₃-modified hydrolysates. Additionally, H₂ gas production with PEH50 and NBH was 1.41- and 1.13-fold higher, respectively, than in other hydrolysates. These findings suggest that SC and BS hydrolysates can be valorized to butanol and hydrogen gas and, thereby, can contribute to global food wastes management, energy sustainability, and cost-effective biofuel production. Full article

Pineapple (Ananas comosus) is one of the most economically important fruit cultivars in South Africa. The fruit is locally consumed, processed into various industrial products or exported to foreign markets. Approximately 115,106 metric tons of pineapple fruit are harvested in South Africa. The pineapple value chain generates significant amounts of waste, in the form of pomace, peel, crown, stem, core and base. If not properly treated, pineapple waste (PAW) could have a profound detrimental impact on the environment. This calls for advanced technological platforms to transform PAW into useful bio-based products. A biorefinery is a potent strategy to convert PAW into multiple food and non-food products while effectively disposing of the waste. The objective of this review is to explore possible pathways for the valorization of PAW into energy and material products in a biorefinery. The paper looks at 10 products including biogas, biohythane, bioethanol, biobutanol, biohydrogen, pyrolytic products, single-cell proteins, animal feed, vermicompost and bioactive compounds. Several platforms (i.e., biochemical, chemical, physical and thermochemical) are available to convert PAW into valuable goods. Amongst them, the biochemical route appears to be the most favorable option for the valorization of PAW. Anaerobic digestion and fermentation are well-established biochemical technologies for PAW valorization. These methods are simple, low-cost, eco-friendly and sustainable. The focal point of emerging research is the enhanced efficacy of biorefinery platforms. The commercialization of PAW biorefining is a potential gamechanger that could revitalize the entire South African economy. Full article