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Abstract Agave bagasse is the lignocellulosic residue accumulated during the production of alcoholic beverages in Mexico and is a potential feedstock for the production of biofuels. A factorial design was used to investigate the effect of temperature, residence time and concentrations of acid and ethanol on ethanosolv pretreatment and enzymatic hydrolysis of agave bagasse. This method and the use of a stirred in-house-made mini-reactor increased the digestibility of agave bagasse from 30% observed with the dilute-acid method to 98%; also allowed reducing the quantity of enzymes used to hydrolyze samples with solid loadings of 30% w/w and glucose concentrations up to 225 g/L were obtained in the enzymatic hydrolysates. Overall this process allows the recovery of 91% of the total fermentable sugars contained in the agave bagasse (0.51 g/g) and 69% of total lignin as co-product (0.11 g/g). The maximum ethanol yield under optimal conditions using an industrial yeast strain for the fermentation was 0.25 g/g of dry agave bagasse, which is 86% of the maximum theoretical (0.29 g/g). The effect of the glucose concentration and solid loading on the conversion of cellulose to glucose is discussed, in addition to prospective production of about 50 million liters of fuel ethanol using agave bagasse residues from the tequila industry as a potential solution to the disposal problems.

Abstract This paper reports on a single alkaline exchange membrane direct formate fuel cell (AEM DFFC) consisting of a carbon-supported palladium catalyst at the anode, a quaternized polysulfone membrane, and a non-precious Fe–Co catalyst at the cathode. It is demonstrated that the AEM DFFC yields a peak power density of 130 mW cm−2 with 5 M potassium formate (HCOOK) at 80 °C. It is further shown that with the addition of KOH to the anolyte, the peak power density rises to as high as 250 mW cm−2 at the same operating temperature. In addition, the AEM DFFC was also tested at 100 mA cm−2 for more than 130 h and no significant degradation in performance is found. The results reported in this work suggest that formate salt (HCOOM, M+ = Na+ or K+) is a potential fuel for alkaline-type direct liquid fuel cells.

Waste biomass is generated during the conservation management of semi-natural habitats, and represents an unused resource and potential bioenergy feedstock that does not compete with food production. Thermogravimetric analysis was used to characterise a representative range of biomass generated during conservation management in Wales. Of the biomass types assessed, those dominated by rush (Juncus effuses) and bracken (Pteridium aquilinum) exhibited the highest and lowest volatile compositions respectively and were selected for bench scale conversion via fast pyrolysis. Each biomass type was ensiled and a sub-sample of silage was washed and pressed. Demineralization of conservation biomass through washing and pressing was associated with higher oil yields following fast pyrolysis. The oil yields were within the published range established for the dedicated energy crops miscanthus and willow. In order to examine the potential a multiple output energy system was developed with gross power production estimates following valorisation of the press fluid, char and oil. If used in multi fuel industrial burners the char and oil alone would displace 3.9 × 105 tonnes per year of No. 2 light oil using Welsh biomass from conservation management. Bioenergy and product development using these feedstocks could simultaneously support biodiversity management and displace fossil fuels, thereby reducing GHG emissions. Gross power generation predictions show good potential.

Abstract Algal biofuel has been advocated as a sustainable and environmentally friendly renewable energy source. However, intensive chemical usage, high energy consumption, and high operation and maintenance costs associated with current cell disruption methods have been identified as main challenges to cost-effective production of algal biofuel. Viral infection of algae is a natural process that can lyse algal cells under ambient conditions without using chemicals or energy-intensive equipment. This study, for the first time, provides a comprehensive and in-depth evaluation of the feasibility of using viruses to assist algal lipid extraction. Detailed mechanistic studies were conducted to evaluate the impact on mechanical strength of algal cell walls, lipid yield, and lipid distribution when Chlorella sp. were infected by Paramecium bursaria Chlorella virus 1 (PBCV-1). Viral disruption with multiplicity of infection of 10−8 was able to disrupt concentrated algal biomass completely in six days. Our results indicated that viral disruption significantly reduced the mechanical strength of algal cells. Lipid yield with viral disruption increased more than three times compared to no disruption controls and was similar to that of ultrasonic disruption. Moreover, lipid composition analysis showed that the quality of extracted lipids was not affected by viral infection. The results showed that viral infection is a highly cost-effective technique to promote lipid extraction without extensive energy input and chemicals required by existing disruption methods. The results of this study provided new insights in the development of nature-inspired lipid extraction methods for cost-efficient biofuel production.

Abstract The thermodynamic cycle of a gas parcel in the thermo-acoustic engine is referred to as a thermo-acoustic micro-cycle, which consists of two isobaric branches by two straight line branches. The influence of quantum degeneracy on the work output of the cycle is investigated based on the correction equation of state of an ideal Bose gas. The relationship between the dimensionless work output W∗ and the efficiency η∗ is obtained under the condition of weak gas degeneracy. Some significant results are discussed.

The photosynthetic capacity of algae as a primary producer in nature and the relative ease of its cultivation on a large scale make it attractive to explore opportunities and develop algal technology for simultaneous sequestration of industrial and atmospheric CO2 (to mitigate climate change), whilst developing sustainable processes for manufacturing renewable fuels alongside biochemicals of value. The development of strategies that maximise algal product yield while optimising the CO2 gas supply is needed for the appropriate scale-up of algal technology. One of the main targets of this technology is the potential exploitation of flue gases, an inexpensive and carbon-rich source. So far, the growth of microalgae has predominantly been investigated using relatively low CO2 concentrations that are far from the levels offered by flue gas (6–25%), which are more useful for energy generation with concomitant development of carbon neutral processes. Here, we tested a series of gas supply strategies to investigate microalgal growth at high CO2 levels with the aim to improve algal CO2 fixation and lipid accumulation. Optimal growth of Nannochloropsis salina (a marine algae) occurred at 6% CO2, whilst few cells grew under 20% CO2. Excess CO2 resulted in medium acidification, pigment reduction, and growth inhibition. However, the fixation capacity of CO2 and the production of specific lipids were improved by O2 removal from the inlet gas by up to 4.8-fold and 4.4-fold, respectively. These parameters were further improved by 72% and 25%, respectively, via a gradual increase in CO2 concentration. Extremely high CO2 levels (100%) completely inhibited cell growth, but this effect was reversed when air containing atmospheric CO2 levels was introduced in place of 100% CO2. These findings will allow for the future development of more effective strategies using algal biotechnology for producing biofuel while mitigating carbon emissions.

Abstract Proton exchange membrane fuel cells (PEMFCs) are one of the most promising energy solutions in meeting the soaring global energy demand and relieving the environmental concerns associated with greenhouse emissions. Cost and durability are two main obstacles hindering the successful commercialization of PEMFCs. Here, we propose a solution which could significantly enhance durability, reduce PGM catalyst, and increase tolerance to impure hydrogen sources thereby reducing cost and increasing convenience by allowing operation in ambient conditions. We show that applying a coating of 1 μg/cm2 of graphene oxide (GO) directly onto the Nafion membrane or electrodes enabled a 60% enhancement of the maximum power output to 0.78 or 0.76 W/cm2, using only a total of 0.15 mg/cm2 Pt catalyst. Durability tests were carried out complying with the DOE2020 protocols, indicating that the enhancement persisted even after 30k cycles, where the maximum power decrease was only 9%, as compared with 18% in the control sample, and the decrease in voltage at 1.5 A/cm2 was only 13%, as compared with 70% of the control sample. In addition, blending of 0.1% CO gas into the input H2 stream reduced the power by 72% in the control, while only 26% power reduction was observed in the coated PEMFCs. Also, electrochemical impedance spectroscopy (EIS) measurements exhibited a decrease in resistance of only 13%, while the active Pt surface area of the electrode with GO coating after 30k cycles was 17.5% higher than the control and the minimal DOE requirement.