Evaluation of biomass pretreatment to optimize process factors for different organic acids via Box-Behnken RSM method.

Biomass, as renewable energy source, is of importance to investigate to extend the conversion yield by microorganism. Because of lignocellulosic structure, biomass must be pretreated with a process, frequently inorganic acid has to be used with a problem of hazardous byproducts. Organic acid pretreatment is an efficient alternative to be investigated. Sugar beet pulp, as an agro-industrial residue of microorganism, can be utilized by pretreatment, which is usually a costly process. Pretreatment with organic acids creates a great opportunity to convert the process into more economic and effective. Moreover, pressure conditions significantly increase the yield of biodegradable sugar content. In this study, different organic acids of maleic, fumaric, oxalic, and acetic acid pretreatment was investigated to pretreatment of sugar beet pulp, which came vast amount from factories, under pressure and non-pressure conditions via Box-Behnken method to estimate optimum point of acid ratio (1, 3, 5%), time (10, 27.5, 45 min), and solid ratio factors (3, 6.5, 10%) for highest degradation. Results were also evaluated economically. As a result of the experiments, it was observed that acetic acid gave the best result with 409.16 g/L total sugar concentration than the other organic acids. The highest TS concentration of maleic, oxalic, and fumaric acid were 97.26, 97.85, and 91.37 g/L, respectively, under pressure. According to economical evaluation, owing to lower market price and highest TS formation yield, pretreatment cost of acetic acid pretreatment was found averagely 1.51 $/gTS under pressure conditions. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10163-021-01276-7.

Environmental and economic evaluation of solar panel wastes recycling.

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.

Continuous production of 1,3-propanediol using raw glycerol with immobilized Clostridium beijerinckii NRRL B-593 in comparison to suspended culture.

The continuous production of 1,3-propanediol (1,3-PDO) was investigated with Clostridium beijerinckii NRRL B-593 using raw glycerol without purification obtained from a biodiesel production process. Ceramic rings and pumice stones were used for cell immobilization in a packed-bed bioreactor. For comparison purpose, a control bioreactor with suspended culture was also run. The effect of hydraulic retention time (HRT) on the production of 1,3-PDO in both immobilized and suspended bioreactors were also investigated. The study revealed that HRT is an important factor for both immobilized and suspended systems and a HRT of 2 h is the best one in terms of volumetric production rate (g 1,3-PDO/L/h). Furthermore, cell immobilization had also obvious benefits especially for the robustness and the reliability of the production. The results indicated that cell immobilization achieved a 2.5-fold higher productivity in comparison to suspended cell system. Based on our results, continuous production of 1,3-PDO with immobilized cells is an efficient method, and raw glycerol can be utilized without any pretreatment.

Treatment of slaughterhouse wastewater by electrocoagulation and electroflotation as a combined process: process optimization through response surface methodology.

The contamination of water with organic compounds has become an increasing concern in today's world. The cost-effective and sustainable treatment of industrial wastewaters is a major challenge. Advanced treatment techniques such as electrocoagulation-electroflotation offer economic and reliable solutions for the treatment of industrial wastewater. In this study, the electrocoagulation-electroflotation method was investigated for the simultaneous removal of chemical oxygen demand, total phosphorus, total Kjeldahl nitrogen, and color via response surface methodology. Factors such as electrode combination (Fe and Al), current density (10-20 mA/cm2), pH (3.0-9.0), and electrode distance (1-3 cm) were investigated in the treatment of wastewater to obtain maximum treatment efficiency. It was determined that chemical oxygen demand, total Kjeldahl nitrogen, total phosphorus, and color removal reached up to 94.0%, 77.5%, 97.0%, and 99.0%, respectively. Treatment costs were found as $0.71 with the Al-Fe electrode combination.

Effect of cell immobilization on the production of 1,3-propanediol.

Immobilized cultures of locally isolated Klebsiella pneumoniae (GenBank no: 27F HM063413) were employed in the continuous production of the high value added biomonomer, 1,3-propanediol from waste glycerol. The effect of hydraulic retention time (HRT) was tested by increasing the dilution rate gradually. Three different immobilization materials (stainless steel wire, glass raschig ring and Vukopor(®)) were tested. The highest productivity was reported with the reactor filled with stainless steel wire as 4.8 g/(L hours) and the highest 1,3-propanediol concentration was 17.9 g/L when glass raschig rings were used as the packing material with the HRTs of 0.5 hours and 1.5 hours, respectively. Compared to the suspended culture system 1,3-propanediol production was more resistant to shorter hydraulic retention times that leads to higher 1,3-PDO productivities. All three of the materials are good candidates for immobilization purpose; however, stainless steel wire and Vukopor(®) are better support materials in terms of productivities. The results reported in this study revealed that continuous fermentation in a packed-bed bioreactor system is a suitable method to enhance 1,3-propanediol production.

Comparative evaluation of pumice stone as an alternative immobilization material for 1,3-propanediol production from waste glycerol by immobilized Klebsiella pneumoniae.

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.

1,3-Propanediol production potential of Clostridium saccharobutylicum NRRL B-643.

Owing to the significant interest in biofuel production in the form of biodiesel, vast amount of glycerol as a waste product is produced all over the world. Among the economically viable and ecologically acceptable solutions for the safe disposal of this waste, biotechnological conversion of glycerol into a valuable bioplastic raw material, namely 1,3-propanediol (1,3-PDO) seems to be very promising. In this study, 1,3-PDO production potential of Clostridium saccharobutylicum NRRL B-643 was studied and the results were compared with other types of anaerobic microorganisms (Clostridium spp., Pantoea agglomerans, Ochrobactrum anthropi, Chyreseomonas luteola, and Klebsiella pneumoniae) and aerobic microorganisms (Lactobacillus spp.). The results were important for understanding the significance of C. saccharobutylicum NRRL B-643 among other well-known 1,3-PDO producer species. According to the screening results only C. saccharobutylicum (B-643) was able to consume feed glycerol almost entirely. However, 1,3-PDO production yield was found to be 0.36mol/mol which is lower than that of Clostiridium beijerinckii (B-593). B-593 showed the highest value of production yields with 0.54 mol/mol. This microorganism is seen as a promising type for further 1,3-PDO studies, because it has the highest substrate utilization percentage among others. In this regard, this microorganism may have an important role in tolerating and converting glycerol during fermentation into 1,3-PDO.