Improved hydrogen gas production in microbial electrolysis cells using inexpensive recycled carbon fibre fabrics

Growing energy demands of wastewater treatment have made it vital for water companies to develop less energy intensive processes for treating wastewater if net zero emissions are to be achieved by 2050. Microbial electrolysis cells (MECs) have the potential to do this by treating water and producing renewable hydrogen gas as a product, but capital and operational costs have slowed their deployment. By using recycled carbon fibre mats, commercially viable MECs can brought closer to reality, where recycled carbon fibre anode MECs treating real wastewater (normalised ~3100 L d−1) were producing 66.77 L H2 d−1 while graphite felt anode MECs produced 3.65 L H2 d−1 per 1 m3 reactor, anodes costing £5.53 m−2 and £88.36 m−2 respectively, resulting in a total anode cost saving of 93%. This could incentivise the development of larger pilot systems, opening the door for generating greater value and a more sustainable wastewater treatment industry

Surface contamination of cars : a review

This review surveys the problem of surface contamination for cars, which poses a growing engineering challenge to vehicle manufacturers, operators and users. Both drivers’ vision and vehicle visibility need to be maintained under a wide range of environmental conditions. This requires managing the flow of surface water on wind screens and side glazing. The rate of deposition of solid contaminants on glazing, lights, license plates and external mirrors also needs to be minimised. Maintaining vehicle aesthetics and limiting the transfer of contaminants to the hands and clothes of users from soiled surfaces are also significant issues. Recently, keeping camera lenses clean has emerged as a key concern, as these systems transition from occasional manoeuvring aids to sensors for safety systems. The deposition of water and solid contaminants onto car surfaces is strongly influenced by unsteady vehicle aerodynamic effects. Airborne water droplets falling as rain or lifted as spray by tyres interact with wakes, vortices and shear flows and accumulate on vehicle surfaces as a consequence. The same aerodynamic effects also control the movement of surface water droplets, rivulets and films; hence, particular attention is paid to surface water management over the front side-glass and the deposition of contaminants on the rear surfaces. The test methods used in the automotive industry are reviewed, as are numerical simulation techniques

Optimisation of waste vegetable oil-based thermoset polymers

Bio-based thermoset polymers were produced from epoxidized waste vegetable oils cured with anhydrides at different molar ratios. Properties were compared to analogues produced with neat oil and DGEBA as a feedstock. Thermal stability proved to be affected by the molar ratio, and the use of feedstock from waste oil resulted in no effect on this property. DMA has shown that higher concentrations of anhydride enhance the storage modulus, Tg (up to 42.5 °C) and crosslink density. The frying process proved to play a minor role in tuning the dynamic-mechanical properties. However, the contribution of the anhydride demonstrated to be significant enough to mitigate the losses caused by the waste oil, as shown statistically in a DOE study. All formulations were chemically resistant to aqueous, organic and acidic media. The identification of the effects of critical parameters on the properties of WVO-based thermosets enables further production of polymers from waste streams

Sustainable alternative composites using waste vegetable oil based resins

Laminates were produced with epoxy resins from waste vegetable oil (WVO) intended for the manufacturing of environmentally-friendly alternatives for the composites industry. Post-use cooking oil appears a promising source of triglycerides for polymer manufacturing. Matrices cured with methylhexahydrophthalic anhydride (MHHPA) were reinforced with glass and flax fibres, creating a library of composites that were compared to analogues from virgin oil and benchmarked against commercial diglycidyl ether of bisphenol A (DGEBA). Glass fibre-reinforced composites presented Young’s moduli similar to the benchmark but reduced tensile strength. Chemical pre-treatment of the flax fibre (NaOH and stearic acid) countered the limited tensile performance observed for materials with untreated flax; improvements were evidenced by DMA and SEM. Moreover, WVO-based resins greatly improved impact properties and reduced density with no effect on thermal stability. Therefore, WVO-based composites appear as more sustainable alternatives in applications demanding toughness, stiffness and lightweight over strength

Epoxy resin blends and composites from waste vegetable oil

Thermosets and composites were prepared from blends of epoxidized waste vegetable oils and diglycidyl ether of bisphenol-A to investigate this material as an alternative triglyceride source for epoxy resins. Purification of the waste oil was developed to remove impurities derived from thermal degradation in the frying process and different epoxidation methodologies were investigated. Effects of epoxidized vegetable oil content (up to 30 wt%) and origin on the tensile properties were studied and revealed that purified waste oils performed similarly to neat oil in contents up to 10 wt%, proving that this strategy does not compromise tensile properties when waste oils are used in suitable proportions. Furthermore, a more prominent plasticizing effect was observed when more than 15 wt% of bio-based resin was used as confirmed by DMA. Composites were prepared with recycled carbon fibres (up to 30 wt%) and thermosets with 10 wt% of bio-based epoxy resins, significantly improving the mechanical properties

Recovery of ammonia from wastewater through chemical precipitation

Chemical precipitation is a consolidated technique applied in wastewater treatment to remove and recover phosphorous and ammonium that remain in the effluent after the anaerobic digestion treatment. The precipitate is magnesium ammonium phosphate hexahydrate (MgNH4PO4·6H2O), also known as struvite, and it is sold as a slow-release fertiliser. However, the value of struvite is quite low and has a limited market. Furthermore, it precipitates with heavy metals and other impurities that need to be removed to make the fertiliser commercially viable. This study looked at the thermal decomposition of struvite to recover added value products and recycle the magnesium for further precipitation. A kinetic study was carried out to understand the mechanism of decomposition and the formation of the different solid phases, which is fundamental for the design and optimisation of the technology. The thermogravimetric study confirmed that thermal decomposition is possible, but ammonia could not be completely released below 250 °C. The thermal analysis also led to the determination of the energy required for the decomposition, found to be 1.87 kJ g−1, which also includes the evaporation of water and ammonia. The kinetic study through the isoconversional method showed the presence of two major reactions, and the model-fitting approach identified the diffusion model as the best fit for the first reaction. The activation energy of the first reaction found with this method was 0.24 kJ g−1, comparable with the data obtained from the isoconversional method. The two-stage decomposition reactions were proposed, and the final calcination product was confirmed as magnesium pyrophosphate, which could be used in agriculture or dissolved in diluted mineral acids solution to separate the phosphate from the magnesium

Alternative glazing for automotive vehicles: executive summary

The first approach utilises a thin film of acrylic that is moulded onto the outside of a polycarbonate substrate. It was found that the gate of the injection mould cavity must be of uniform cross section otherwise local shear heating can occur and melt the acrylic film. The injection gate must also be located entirely on one side of the mould cavity otherwise the film is punctured by the molten polycarbonate and free to float within the cavity. Any mixing of the two materials will lead to opaque components due the difference in the refractive indices. The film was found to improve the UV resistance of any component, acting as a protective buffer for the polycarbonate. A new variety of hardcoat was applied to film-backed samples to impart abrasion resistance and samples were found to outperform commercially available alternatives under recognised laboratory conditions. The film-backed samples also exhibited excellent impact resistance when impacted upon the film-face. However, similar components failed at extremely low energy levels when impacted from the non-film face because flaws in the acrylic film caused cracks to be initiated when the film was placed into tension. The level of adhesion between the film and the polycarbonate has been found to be critical and if the failure mechanism could be guaranteed, then intruder resistant glazing that could be broken from the inside in an emergency becomes a possibility. Such a product would address the identified consumer concern of being trapped in a vehicle. The second approach utilises simultaneous dual injection moulding (2K), which has previously only been used to manufacture coloured components. A successful feasibility study was undertaken to demonstrate the concept of producing transparent components via such a process. This showed that much greater control is required for transparent applications otherwise the skin and core materials mix and opaque components are produced. The generally accepted academic principles associated with the process have been shown to be too simplistic and cannot be relied upon to guarantee good results. The ratio of viscosities of the skin and core materials appear to be more dominant than previously thought and the relative injection speeds of the two materials has a direct influence upon interfacial mixing and haze generation. It was also found that haze could be avoided if the refractive indices of the skin and core material were matched to within ±0.002, but this is impractical. A third area of research examined the feasibility of introducing structured glass fibres weaves into transparent components to improve rigidity. The study resulted in the construction of a transparent glass fibre pre-preg that could be moulded onto the outer surface of polycarbonate components. Flexural tests revealed that a single layer of glass fibre increased the flexural modulus of test samples by a factor of 3, whilst transparency and clarity were retained. Two patents have been filed as a direct result of this work

Simulation of rear surface contamination for a simple bluff body

Predicting the accumulation of material on the rear surfaces of square-backed cars is important to vehicle manufacturers, as this progressively compromises rear vision, vehicle visibility and aesthetics. It also reduces the effectiveness of rear mounted cameras. Here, this problem is represented by a simple bluff body with a single sprayer mounted centrally under its rear trailing edge. A Very Large Eddy Simulation (VLES) solver is used to simulate both the aerodynamics of the body and deposition of contaminant. Aerodynamic drag and lift coefficients were predicted to within +1.3% and −4.2% of their experimental values, respectively. Wake topology was also correctly captured, resulting in a credible prediction of the rear surface deposition pattern. Contaminant deposition is mainly driven by the lower part of the wake ring vortex, which advects material back onto the rear surface. This leads to a maximum below the rear stagnation point and an association with regions of higher base pressure. The accumulation of mass is linear with time; the relative distribution changing little as the simulation progresses, implying that shorter simulations can be compared to longer experiments. Further, the rate of accumulation quickly reaches a settled mean value, suggesting utility as a metric for assessing different vehicles

Biodegradation as natural fibre pre-treatment in composite manufacturing

Bacterial and fungal degradation of wheat straw has become intensively scrutinised in recent years because of the growing interest in procuring useful feedstocks and chemicals from lignocellulosic sources. Typically, after the extraction of valuable sugars and phenolics, significant quantities of solid biomass remain as waste. In this work, it has been shown that the leftover fermented wheat straw can be successfully used to reinforce epoxy resins, providing better strength properties compared to non-degraded straw. A 12% and a 22% increase in Young’s modulus and ultimate tensile strength respectively were observed for degraded wheat straw/epoxy composites compared to composites containing non-degraded straw. The improvement in mechanical strength is explained in terms of the structural and morphological transformations that occurred in the fibres during the fermentation process. The opportunity to use degraded natural fibres in the manufacturing of composites, in addition to the production of chemicals from lignocellulosic feedstocks, looks promising for improving biorefinery economics further

GM crops and gender issues

Correspondence in the December issue by Jonathan Gressel not only states that gender issues in rural settings have not been adequately addressed with respect to weed control biotech but also asserts that such technology can increase the quality of life of rural women in developing countries. Improved weed control is a labor-saving technology that can result in less employment in a labor surplus rural economy. Often in rural areas, wage income is the main source of income and an important determinant of the quality of life, particularly where employment opportunities are generally limited. Apart from soil preparation, planting and weeding, harvesting is also 'femanual' work that can generate more employment if yields are higher. Biotech can enhance the quality of life of women but only if the technology is associated with overall generation of rural employment