Characterization of silver nanoparticles produced by biosynthesis mediated by Fusarium oxysporum under different processing conditions

The goal of this study was the biosynthesis of silver nanoparticles (SNPs) mediated by the fungus Fusarium oxysporum, as well as the characterization of these nanoparticles including evaluation of the particles size and stability under different processing conditions. The results showed that the biosynthesis produced silver nanoparticles having a mean size of 34 nm and zeta potential values below −30 mV at the conditions used, characterizing the nanoparticles as being stable in suspension. Ultraviolet–visible spectroscopy and flame atomic absorption spectroscopy confirmed the formation of silver nanoparticles and Fourier transform infrared spectroscopy detected the bands corresponding to the binding vibration of amide I and II bands of proteins in addition to the presence of cyclic alkanes, cyclohexane, ethers, and aromatic hydrocarbons. Finally, field emission scanning electron microscopy and transmission electron microscopy revealed the formation of spherical and well-dispersed SNPs.

     

Carbon footprint and embodied energy of a wind turbine blade—a case study

Purpose

The main goal of this work is to evaluate the environmental impact of a 63-m blade for wind generators. The embodied energy and the carbon footprint are used as supporting tools for material selection in the initial project stages.

Methods

Real industrial data regarding the most used materials for wind turbine blade construction are used. Two eco-parameters, embodied energy and carbon footprint, were calculated from each selected material together with values of manufacture, transport, use, and final disposal. The blades must be built to have a mechanical strength high enough to withstand vibrations caused by manufacturing flaws, turbulence, or irregular loading. In this sense, Young’s modulus, yield strength, and density were compared to the environmental footprint data to support the final material choice. This evaluation process of the possible materials to be used in the blade manufacture was carried out in the initial stages of the project.

Results

Composite materials such as glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP), bonded together with an adhesive material, are used to build modern wind turbine blades. Those composites comprise a considerable number of different materials that can be mixed to reach adequate performance. Comparisons were made with 46 pre-selected materials, considering the mechanical behavior and environmental impacts. The final selected materials have better properties than the reference material. Finally, two materials with the desired mechanical properties and with a potential lower negative environmental impact than the reference material were selected.

Conclusions

Replacing the reference resin—epoxy/E-glass fiber—with the epoxy resin with the lowest environmental impact—epoxy/S-glass fiber—will reduce the total value of the environmental load to 102 GJ of energy and 3.4 t of CO₂. As important as the material selection in the early stages of product development is the end of life (EoL) choice. In this case, the glass fiber has an EoL potential of 370 GJ of energy and 460 t of CO₂ in the remanufacturing option, against zero for the landfill. This work shows that carefully selected raw materials and EoL alternatives for WTB can significantly reduce the environmental impact of this component.