Sophorolipids Production from Oil Cake by Solid-State Fermentation. Inventory for Economic and Environmental Assessment

Biosurfactants are being proposed as a substitute for surfactants in the framework of a circular economy strategy. Sophorolipids (SL) are a type of biosurfactant produced by yeast that can be produced through submerged or solid-state fermentation (SSF) processes. Even though sophorolipids are being produced at full scale, through submerged fermentations, environmental and technoeconomic information regarding its production through SSF is unavailable. An inventory of data necessary to perform preliminary economic and environmental assessments is presented in this study. Data was obtained from three SSF processes at 22-L reactor volume and from two SSF processes at 100-L reactor volume, using winterization oil cake and molasses as substrates, wheat straw as support material, and Starmerella bombicola as SL producing yeast. The effect of increasing the operation scale was assessed. Besides presenting parameters such as inoculum production, initial mass of substrates, and airflow requirements; process emissions (NH3, Volatile Organic Compounds, N2O, SH2 and CH4) and the biogas potential of the spent fermentation solids were also presented.

Statistical Analysis of Anode Efficiency in Electrochemical Treatment of Wastewater and Sludge

Electrochemical processes have proven their potential as effective technologies to treat wastewater from industrial, urban and agricultural activities, and thus, contribute towards a cleaner environment. In this study, we aimed to assess the effectiveness of the leading electrochemical technologies, such as electro-oxidation, electrochemical coagulation and electrochemical advanced oxidation processes (EAOPs), statistically for different types of anodes for the removal of various pollutants from wastewater along with their treatment efficiency. Anode is considered as a source of electron and an essential part of electrochemical processes. So, we have evaluated the relationship between different anode features such as anodic material, surface area versus removal of chemical oxygen demand (COD), dissolved organic carbon (DOC) and colour in various wastewater treatment plants (WWTPs) by IBM SPSS Statistics 26. Apart from that, various process characteristics such as inter-electrode distance, system pH, reactor volume, current density and voltage were also considered in this investigation. From the regression analysis of the electrochemical coagulation system, it was found that the removal efficiency of pollutants is enhanced by the surface area of the electrodes along with the inter-electrode distance. Regarding electro-oxidation, it was seen that COD and colour removal are both dependent on the reaction time of the system, while the DOC removal rate of different EAOPs was strongly related to the reactor volume. Furthermore, the uncertainty of the regression analysis on pollutant removal efficiency prediction was assessed. Finally, sensitivity analysis was done by Monte-Carlo method to check modest changes from input variables.

Energy Efficiency of a Small Bioreactor in Various Climatic Zones

The authors proposed a model for estimating the heat balance and energy efficiency of a bioreactor that makes possible for a small-sized reactor operating on a relatively low-energy substrate to determine the critical volume, under which the existing climatic conditions allow year-round fully autonomous operation of the digester, as well as for evaluation the potential energy efficiency of such a bioreactor (output commodity heat). For the numerical characteristics of the climatic zone, it is proposed to use the average annual temperature and/or the “degree-day of the heating period” (DDHP) indicator common in construction heat engineering; the DDHP value more adequately characterizing the unevenness of the average monthly temperature distribution, i.e. degree of climate continentality. At the same time, the value of the critical volume of the bioreactor, at which year-round autonomous operation of the digester operating on the municipal sewage sludge, is possible, varies from 7.5 (Vladikavkaz, DDHP = 3410) to 17.0 m3 (Tomsk, DDHP = 6938), i. e. increases almost in proportion to the degree-day of the heating period. It should be noted that when using a substrate with a high biogas yield, e. g., pig manure (a biogas yield of 40 g/kg is adopted), the critical volume in all cases is less than 1 m3. Such results are relevant only for relatively low-energy raw materials. The nature of changes in the output of commodity heat, depending on the volume of the bioreactor and climatic conditions, is quite expectable, viz. the amount of heat that is useful for business interests is higher, the higher is the reactor volume and the milder is the climate. However, when the reactor volume is less than 5 m3, the non-linearity of the graphs is much higher, i. e. for a designer of especially small bioreactors, it seems mandatory to carry out such calculations. The obtained numerical values can be useful both for the designer of bioreactors and for the customer of the project when evaluating the economic efficiency of the planned new innovations.

Influence of the pH control strategy and reactor volume on batch fermentative hydrogen production from the organic fraction of municipal solid waste

Three different experimental sets of runs involving batch fermentation assays were performed to evaluate the influence of the experimental conditions on biological hydrogen production from the source-separated organic fraction of municipal solid waste collected through a door-to-door system. The fermentation process was operated with and without automatic pH control, at a pH of 5.5 and 6.5, food-to-microorganism ratios of 1/3 and 1/1 (wet weight basis) and with different working volumes (0.5 and 3 L). The experimental results showed that the pH control strategy and the reactor volume did not affect the final hydrogen production yield but played an important role in determining the time evolution of the process. Indeed, although the different experimental conditions tested yielded comparable hydrogen productions (with maximum average values ranging from 68.5 to 88.5 NLH2 (kgTVSOF)−1), the automatic pH control strategy improved the process from the kinetic viewpoint resulting in a t95 reduction from an average of 34.9 h without automatic pH control to an average of 19.5 h.

THE DEVELOPMENT OF A BASIC PROCESS SCHEME FOR THE PREPARATION OF ISOAMYL ACETATE

The article reports the development of a technological scheme for isoamyl acetate preparation on the basis of kinetic data, vapor-liquid and liquid-liquid equilibrium data. A review of isoamyl acetate production methods was made. At present most of the methods are based on esterification reaction, which takes place in the presence of homogenous and heterogeneous catalysts. Heterogeneous catalysis is preferred because of absence the catalyst separation problem. In the first part of the work vapor-liquid and liquid-liquid equilibrium simulation was made. NRTL and UNIQUAC models were used to calculate phase equilibrium of a quaternary reaction mixture. It was proved by comparison of deviations of the calculated temperature and vapor mole fractions from the experimental values that NRTL is the best model for the considered mixture phase equilibrium calculations. This model was used in further calculations of distillation and liquid-liquid splitting. The choice of the technological scheme is based on the use of the principle of both distillation and liquid phase separation and the recycling of substances in the system. The difficulty in isolating pure isoamyl acetate as a product is due to the presence of four binary azeotropes and two triple ones in the system. When developing and selecting a technological scheme, the possibility of obtaining maximum conversions of the reactants was taken into account. Besides, when designing and calculating the scheme, an assumption was made about infinite separating ability of separation distillation columns. To check operating efficiency of the scheme in real conditions, a verification calculation was made to determine the minimum and working reactor volume. The minimum and working reactor volume calculation was based on the Langmuir-Hinshelwood-Hougen-Watson model for the kinetics of the esterification reaction. The selection of constructive and operating parameters of the scheme, at which high quality of isoamyl acetate is achieved, was made.

Study on Simulation of Biomass Gasification for Syngas Production in a Fixed Bed Reactor

This study was focusing on the simulation of the biomass (coffee bean husk and rice husk) gasification process based on the kinetics of the gasifier and to investigate the produced syngas composition. The ASPEN PLUS simulator was used to investigate the effect of operating parameters on composition of product gas. The gasification process usually begins with the drying process, and then followed by pyrolysis. The pyrolysis process leads to breaking down of the biomass into solid matter, gaseous mixture (mainly CO2, CO, CH4 and H2) and liquid matter. The main focus on biomass gasification process is to efficiently convert the entire char constituent into gaseous product of the syngas by using either steam or CO2. The simulations include; gasification temperature, pressure, reactor volume, Equivalence ratio and moisture content have been investigated. From the result of sensitivity analysis increase the temperature the production of H2 and CO and the increase of moisture content of the biomass the lower heating value of the producer gas decrease. Based on the obtained result the maximum lower heating value of syngas was obtained at the gasification temperature of 8000C, steam to biomass ratio of 0.1, pressure of 1 bar, 0.05 of moisture content and 0.02 m3 of reactor volume.

Sludge blanket anaerobic baffled reactor for source-separated blackwater treatment

The performance of a sludge blanket anaerobic baffled reactor was tested as an integrated treatment system for source-separated blackwater. The system consists of a stirred equalization tank, a buffer inlet tank, and two identical reactors, each with a working volume of 16.4 L, operated in parallel. Both reactors run at 3-days hydraulic retention time with different intermittent pulse feeding. Pulse lengths of 12 and 24 seconds per feed were set with respective rates of 114 L h−1 and 52 L h−1 for the short-pulse fed reactor (RI) and the long-pulse fed reactor (RII). Stable performance of the reactors was attained after 120 and 90 days, for RI and RII, respectively. After stable conditions attained, total chemical oxygen demand (COD) removal efficiency stabilized above 78%. Biogas production ranged from 0.52 to 1.16 L d−1 L−1 reactor volume, with 67–82% methane concentration and an average conversion of 0.69 ± 0.2 and 0.73 ± 0.2 g CH4-COD g−1CODin for RI and RII, respectively. The results imply that source-separated blackwater can be treated effectively in an anaerobic sludge blanket process on average loading rate of 2.3 ± 0.5 g COD d−1 L−1 reactor volume with high methane production potential and more than 80% removal of organic and particulate matter.