• Energy Research

One of the main triggers of the climate change is the consumption of fossil derivative fuel to satisfy the energy need, and also it is clearly known that the future of the fossil fuel supply is limited. That is why, finding and using alternative, sustainable, renewable, and eco-friendly energy sources are inevitable to fight climate change and to reduce the global warming. Biomass is a well-known renewable material for energy production and is called as biofuels. There are some limitations to utilize the biomass effectively, because of the structure of their molecular forms. For this very reason, the pretreatment pathways to increase the biomass sugar concentration potential to increase the bioconversion potential are attempted in this study. Two different pretreatment methods, i.e., hydrogen peroxide and acid, were applied to biomass, which in this case is duckweed, taken from artificial pond at Nigde, Turkey. In order to determine important factors of the processes, Plackett–Burman design was used. Chemicals dosages, timing, temperature, solid ratio, and mesh size are identified using this methodology to obtain the interested results. Box–Behnken statistical design method was applied to make the optimization of the factors chosen from the factorial design. Consequently, Box–Behnken test indicated that acid pretreatment method showed slightly better results than the hydrogen peroxide application per total sugar concentration, which are 0.60 and 0.48 g/L, respectively.

It is well known that energy-related emissions have been increasing the global warming and pushing the climate change. In the face of this situation biomass-based biofuels, which is a kind of renewable energy source, are great alternatives instead of fossil derivative fuels. Moreover, biomass can be found easily and widely, which makes it an economical alternative. Biological conversation rate of the biomass to the biofuel is insufficient because of the molecular structure of the biomass. Pretreatment is required to increase the bioavailability of the biomass as the raw material. In this study, weak and strong acid pretreatments are studied under pressurized and non-pressurized conditions for apple pulp as biomass, which is an agro-industrial residue coming from industrial plants. Box-Behnken statistical design is used to determine the optimum level of some factors as time, chemical dose, and raw material dose. While the maximum total sugar concentration was found to be 23.71 g/L with sulfuric acid pretreatment, the reduced sugar concentration under pressurized conditions with strong acid pretreatment was found as 17.00 g/L.

Owing to rising population and increasing energy demand, renewable energy resources become the most convenient and promising solution. Hence, solar power plant investments and photovoltaic module numbers have risen sharply. Turkey is one of the tight followers of the energy trends, thanks to its rising energy demand and economic power. However, the consequences of the massive plant wastes importance in term of economically and environmentally have not been understood yet. Almost 70% of the modules are formed by glass and the rest accumulates economically valuable metal materials, which are silver, aluminium and copper. These three main materials are substantially important in the overall waste. Not only the economic value, but also the environmental impacts of the mining effluents to excavate these metals are causing emission problems. As a chain reaction, the higher energy demand triggers a search for new and renewable energy resources. This is why popularity of solar energy has increased. Solar energy can be absorbed and transformed through photovoltaic modules, which contain glass and three main metals. In order to respond for the production of modules, metals are fundamental. This need triggers the need of metals mining excavations and emissions. In this respect, in the near future, thanks to the rising investments on photovoltaic modules and the CO2 emissions coming from mining, the wastes of photovoltaic modules and the need of recycling will become more important. That is why, in this study it is aimed to present environmental benefits and economic recoveries of recycling photovoltaic module in Turkey.

In this study, pumice stone (PS), which is a vastly available material in Turkey, was evaluated as an alternative immobilization material in comparison to other commercially available immobilization materials such as glass beads and polyurethane foam. All immobilized bioreactors resulted in much better 1,3-propanediol production from waste glycerol in comparison to the suspended cell culture bioreactor. It was also demonstrated that the locally available PS material is as good as the commercially available immobilization material. The maximum volumetric productivity (8.5 g L(-1) h(-1)) was obtained by the PS material, which is 220 % higher than the suspended cell system. Furthermore, the immobilized bioreactor system was much more robust against cell washout even at very low hydraulic retention time values.