Small-scale production of straight vegetable oil from rapeseed and its use as biofuel in the Spanish territory

Biofuels nowadays are an important topic of study. The most significant point is the availability of bioethanol or biodiesel and their production from different raw materials. It is already known that large-scale production of first-generation biodiesel cannot be seen as an alternative to fossil fuels due to land requirements, competition with food, increase in fertilizer requirements and pressure on tropical forests among others. This fact does not necessarily apply to second-generation biofuels or small-scale niche productions. Straight vegetable oil (SVO) can be used directly in diesel engines with minor modifications. Our proposal is a small-scale SVO production system for self-supply in agricultural machinery. In this paper a model to provide SVO to local farmers in a specific area in Catalonia (Spain) is presented. We also present a discussion about the regulations to be changed in order to make possible the incorporation of SVO as engine fuel in diesel vehicles and a comparative analysis between the emissions of tractors fed with SVO and petrodiesel. Moreover, a quantitative economic analysis of modifying diesel engines and long-term operability costs are shown and a first-run economic analysis comparing the actual crop rotation with the proposed one and some alternatives is studied.     

Batch slurry photocatalytic reactors for the generation of hydrogen from sulfide and sulfite waste streams under solar irradiation

In this study, two solar slurry photocatalytic reactors i.e., batch reactor (BR) and batch recycle reactor with continuous supply of inert gas (BRRwCG) were developed for comparing their performance. The performance of the photocatalytic reactors were evaluated based on the generation of hydrogen (H₂) from water containing sodium sulfide (Na₂S) and sodium sulfite (Na₂SO₃) ions. The photoreactor of capacity 300 mL was developed with UV-vis transparent walls. The catalytic powders ((CdS/ZnS)/Ag₂S + (RuO₂/TiO₂)) were kept suspended by means of magnetic stirrer in the BR and gas bubbling and recycling of the suspension in the BRRwCG. The rate constant was found to be 120.86 (einstein⁻¹) for the BRRwCG whereas, for the BR it was found to be only 10.92 (einstein⁻¹). The higher rate constant was due to the fast desorption of products and suppression of e⁻/h⁺ recombination.     

Selection of the best pretreatment for hydrogen and bioethanol production from olive oil waste products

Bioethanol is one of the most promising renewable energy sources, and it can be used as an alternative to petroleum-derived products. Agro-food residues are the substrates most frequently used for bioethanol production through anaerobic fermentation. The cultivation of olive trees and olive oil production are important economic activities throughout all Mediterranean countries. The wastes derived from olive oil production include a liquid waste, known as Olive Mill Wastewater (OMW), and a semi-solid waste, called Olive Pomace (OP), which is rich is lignin and cellulose materials. The aim of this work is to evaluate the quantity of hydrogen and bioethanol that could be extracted from an OMW-OP mixture after Saccharomyces cerevisiae anaerobic fermentation. In addition, different pretreatments (ultrasonic pretreatment, basic pretreatment, and calcium carbonate addition) have been tested to increase the glucose concentration and, consequently, the bioethanol and hydrogen production in the reaction medium and to decrease the content of inhibiting polyphenols which are mainly present in the OMW. All of the pretreatments were shown to have improved the hydrogen and bioethanol concentration at the end of the fermentation. The basic and ultrasonic pretreatments resulted in the best bioethanol and hydrogen production. These two pretreatments contributed to the hydrolysis of the lignin and cellulose and to increasing the soluble sugars (in particular glucose) content in the reaction mixture. Calcium carbonate addition decreased the polyphenol concentration; the polyphenols inhibit the fermentation mediated by S. cerevisiae.     

Efficacy of Bacillus subtilis for the biodegradation and viscosity reduction of waxy crude oil for enhanced oil recovery from mature reservoirs

Increasing maturity of the crude oil reservoirs across the world have led to the production of waxy crude oil which need economical and efficient methods for enhanced oil recovery (EOR). The studies on the performance of bacteria in the presence of waxy crude oil is rare. In this study, experiments were performed to understand the efficacy of thermophillic microorganism Bacillus subtilis on the biodegradation of waxy crude oil for EOR applications. Bacterial growth, changes in crude oil composition, viscosity reduction, and surface and emulsification activity have been monitored to evaluate the oil degradation capabilities of the bacteria. This study also presents the effect of temperature, salinity, pH, and pressure on the stability of the produced biosurfactant for EOR applications. The biosurfactant produced by bacteria in the presence of crude oil was found to be stable up to 120°C, 10 MPa, 15% salinity, and wide range of pH, and thus favorable for reservoir environment. The crude oil composition before and after degradation at 75°C was determined using gas chromatography-mass spectroscopy and observed to be 60% in one day, while the maximum viscosity reduction was found to be 60% from initial values. Experimental results showed that the bacteria used in this work are capable of surviving at reservoir conditions, and are easy to grow on the waxy crude oil for enhanced oil recovery operations.     

The influence of seed and oil storage on the acid levels of rubber seed oil, derived from Hevea brasiliensis grown in Xishuangbanna, China

High acid levels, characteristic of rubber seed oil (RSO), limit RSO use in biodiesel production. The aims of this study were to determine the causes of these high acid levels by investigating what affects the storage of rubber seeds and RSO had on the acid levels. Two storage conditions/methods were evaluated, one representing a proposed storage method (SM 1), the other mimicking storage conditions characteristic to the Xishuangbanna region (SM 2). Furthermore, RSO storage was evaluated by testing RSO acid levels over a 2-month period, under standard storage conditions. Seeds from SM 2 displayed increased seed pile temperatures, higher levels of Mildew infection, lower seed oil content and higher acid levels. Low seed oil content and high acid values of SM 2 were resultant of the high Mildew infection and increased seed pile temperatures. In addition, a critical value of 90% relative humidity of seed piles was identified, above which Mildew infection increased sharply. Storage of crude RSO resulted in increased acid values. This data shows that in order to reduce high acid values, seed pile temperature, humidity and Mildew infections need to be kept to a minimum, as well as the storage time of the seeds and the RSO.     

Kinetics of the NH reaction with H2 and reassessment of HNO formation from NH + CO2, H2O

The reaction of ground-state NH with H₂ has been studied in a high-temperature photochemistry (HTP) reactor. The NH(X³Σ) radicals were generated by the 2-photon 193 nm photolysis of NH₃, following the decay of the originally produced NH(A³Π) radicals. Laser-induced fluorescence on the transition at 336 nm was used to monitor the progress of the reaction. We obtained , with ±2σ precision limits varying from 12 to 33% and corresponding accuracy levels from 23 to 39%. This result is in excellent agreement with that of Rohrig and Wagner [Proc. Combust. Inst. 25 (1994) 975] and the data sets can be combined to yield . Starting with this agreement, it is argued that their rate coefficients for NH + CO₂ could not be significantly in error [Proc. Combust. Inst. 25 (1994) 975]. This, combined with models of several combustion systems, indicates that HNO + CO cannot be the products, contrary to their suggestion [Proc. Combust. Inst. 25 (1994) 975]. Ab initio calculations have been performed which confirm this conclusion by showing the barriers leading to these products to be too high compared to the measured activation energies. The calculations indicate the likelihood of formation of adducts, of low stability. These then may undergo further reactions. The NH + H₂O reaction is briefly discussed and it is similarly argued that HNO + H₂ cannot be the products, as had been previously suggested.     

Thermo-economic analysis of using an organic Rankine cycle for heat recovery from both the cell stack and reformer in a PEMFC for power generation

Distributed power generation is gaining attention as a solution for the transmission loss and site selection in centralized power generation. Polymer-electrolyte membrane fuel cells (PEMFCs) are suitable as a distributed power source for residential areas because of their high efficiency and low environmental impact. This study proposes a combined power generation system for recovering waste heat from both the cell stack and the reformer of a PEMFC by applying an organic Rankine cycle (ORC). The best working fluid with the highest ORC power output (i.e., the highest combined system efficiency) was identified through a parametric study of different working fluids. An economic analysis was also performed for different working fluids, waste heat sources, and types of system operation. The results show that the installation cost of the ORC can be recovered within the fuel cell's lifetime in all design cases. Greater cumulative profit can be generated by maintaining the same power output as the stand-alone PEMFC system for greater efficiency than when increasing the power output to sell surplus power. The results demonstrate that the optimal heat recovery from the PEMFC system is both thermodynamically and economically beneficial.