Encarnación Ruiz

Hydrothermal pre-treatment of rapeseed straw

As a first step for ethanol production from alternative raw materials, rapeseed straw was studied for fermentable sugar production. Liquid hot water was used as a pre-treatment method and the influence of the main pre-treatment variables was assessed. Experimental design and response surface methodology were applied using pre-treatment temperature and process time as factors. The pretreated solids were further submitted to enzymatic hydrolysis and the corresponding yields were used as pre-treatment performance evaluation. Liquid fractions obtained from pre-treatment were also characterized in terms of sugars and no-sugar composition. A mathematical model describing pre-treatment effects is proposed. Results show that enzymatic hydrolysis yields near to 100% based on pretreated materials can be achieved at 210-220 degrees C for 30-50 min, equivalent to near 70% of glucose present in the raw material. According to the mathematical model, a softer pre-treatment at 193 degrees C for 27 min results in 65% of glucose and 39% of xylose available for fermentation.

Photocatalytic degradation of eight pesticides in leaching water by use of ZnO under natural sunlight.

Photodegradation of eight pesticides in leaching water at pilot plant scale using the tandem ZnO/Na(2)S(2)O(8) as photosensitizer/oxidant and compound parabolic collectors under natural sunlight is reported. The pesticides, habitually used on pepper culture and belonging to different chemical groups were azoxyxtrobin, kresoxim-methyl, hexaconazole, tebuconazole, triadimenol, and pyrimethanil (fungicides), primicarb (insecticide), and propyzamide (herbicide). As expected, the influence of the semiconductor used at 150 mg L(-1) on the degradation of pesticides was very significant in all cases. Photocatalytic experiments show that the addition of photosensitizer strongly improves the elimination of pesticides in comparison with photolytic tests; significantly increasing the reaction rates. The use of Na(2)S(2)O(8) implies a significant reduction in treatment time showing a quicker reaction time than ZnO alone. On the contrary, the addition of H(2)O(2) into illuminated ZnO suspensions does not improve the rate of photooxidation. The disappearance of the pesticides followed first-order kinetics according to Langmuir-Hinshelwood model and complete degradation occurs from 60 to 120 min. The disappearance time (DT(75)), referred to the normalized illumination time (t(30 W)) was lower than 3 min in all cases.

Dilute acid pretreatment of rapeseed straw for fermentable sugar generation

The influence of the main pretreatment variables on fermentable sugar generation from rapeseed straw is studied using an experimental design approach. Low and high levels for pretreatment temperature (140-200 °C), process time (0-20 min) and concentration of sulfuric acid (0.5-2% w/v) were selected according to previous results. Glucose and xylose composition, as well as sugar degradation, were monitored and adjusted to a quadratic model. Non-sugar components of the hydrolysates were also determined. Enzymatic hydrolysis yields were used for assessing pretreatment performance. Optimization based on the mathematical model show that total conversion of cellulose from pretreated solids can be achieved at pretreatment conditions of 200 °C for 27 min and 0.40% free acid concentration. If optimization criteria were based on maximization of hemicellulosic sugars recovery in the hydrolysate along with cellulose preservation in the pretreated solids, milder pretreatment conditions of 144 °C, 6 min and 2% free acid concentration should be used.

Ethanol Production From Pretreated Olive Tree Wood and Sunflower Stalks by an SSF Process

Olive tree wood and sunflower stalks are agricultural residues largely available at low cost in Mediterranean countries. As renewable lignocellulosic materials, their bioconversion may allow both obtaining a value-added product, for fuel ethanol, and facilitating their elimination. In this work, the ethanol production from olive tree wood and sunflower stalks by a simultaneous saccharification and fermentation (SSF) process is studied. As a pretreatment, steam explosion at different temperatures was applied. The water insoluble fractions of steam-pretreated sunflower stalks and steamed, delignified olive tree wood were used as substrates at 10% w/v concentration for an SSF process by a cellulolytic commercial complex and Saccharomyces cerevisiae. After 72-h fermentation, ethanol concentrations up to 30 g/L were obtained in delignified steam-pretreated olive tree wood at 230°C and 5 min. Sunflower stalks pretretated at 220°C and 5 min gave maximum ethanol concentrations of 21 g/L in SSF experiments.

Pretreatment of olive tree biomass with FeCl3 prior enzymatic hydrolysis.

Olive tree biomass (OTB) is an agricultural residue which can be used as raw material for bioethanol production. OTB was pretreated with 0.05-0.275 M FeCl(3) solutions at 120-180 °C for 0-30 min. Enzymatic hydrolysis yields were used for assessing pretreatment performance. Optimum FeCl(3) pretreatment conditions were found to be 152.6 °C, 0.26 M FeCl(3) for 30 min. Under such conditions, 100% of hemicellulose was removed, and enzymatic hydrolysis of pretreated solids resulted in a yield of 36.6g glucose/100g of glucose in the raw material. Hemicellulosic sugar recovery in the prehydrolysate was 63.2%. Results compare well with those obtained by other pretreatment strategies on the same raw material, confirming FeCl(3) solutions as a new, feasible approach for bioethanol production.

Use of farming and agro-industrial wastes as versatile barriers in reducing pesticide leaching through soil columns.

Increased interest has been recently focused on assessing the influence of the addition of organic wastes related to movement of pesticides in soils of low organic matter (OM) content. This study reports the effect of two different amendments, animal manure (composted sheep manure) and agro-industrial waste (spent coffee grounds) on the mobility of 10 pesticides commonly used for pepper protection on a clay-loam soil (OM = 0.22%). The tested compounds were azoxystrobin, cyprodinil, fludioxonil, hexaconazole, kresoxim-methyl, pyrimethanil, tebuconazole, and triadimenol (fungicides), pirimicarb (insecticide), and propyzamide (herbicide). Breakthrough curves were obtained from disturbed soil columns. Cumulative curves obtained from unamended soil show a leaching of all pesticides although in different proportions (12-65% of the total mass of compound applied), showing triadimenol and pirimicarb the higher leachability. Significant correlation (r = 0.93, p<0.01) was found between the observed and bibliographical values of GUS index. The addition of the amendments used drastically reduced the movement of the studied pesticides. Only two pesticides were found in leachates from amended soils, pyrimethanil (<1%) for both, and pirimicarb (44%) in the soil amended with spent coffee grounds. A decrease in pesticide leaching was observed with the increase in dissolved organic matter (DOM) of leachates. The results obtained point to the interest in the use of organic wastes in reducing the pollution of groundwater by pesticide drainage.

Dilute sulfuric acid pretreatment of sunflower stalks for sugar production.

In this work the pretreatment of sunflower stalks by dilute sulfuric acid is studied. Pretreatment temperature and the concentration of acid solution were selected as operation variables and modified according to a central rotatable composite experimental design. Based on previous studies pretreatment time was kept constant (5 min) while the variation range for temperature and acid concentration was centered at 175°C and 1.25% (w/v) respectively. Following pretreatment the insoluble solids were separated by filtration and further submitted to enzymatic hydrolysis, while liquid fractions were analyzed for sugars and inhibitors. Response surface methodology was applied to analyze results based on the combined severity of pretreatment experiments. Optimized results show that up to 33 g of glucose and xylose per 100g raw material (65% of the glucose and xylose present in the raw material) may be available for fermentation after pretreatment at 167°C and 1.3% sulfuric acid concentration.

Reduction of the movement and persistence of pesticides in soil through common agronomic practices.

Laboratory and field studies were conducted in order to determine the leaching potential of eight pesticides commonly used during pepper cultivation by use of disturbed soil columns and field lysimeters, respectively. Two soils with different organic matter content (soils A and B) were used. Additionally, soil B was amended with compost (sheep manure). The tested compounds were cypermethrin, chlorpyrifos-methyl, bifenthrin, chlorpyrifos, cyfluthrin, endosulfan, malathion and tolclofos-methyl. In soil B (lower organic matter content), only endosulfan sulphate, malathion and tolclofos-methyl were found in leachates. For the soil A (higher organic matter content) and amended soil B, pesticide residues were not found in the leachates. In addition, this paper reports on the use of common agronomic practices (solarization and biosolarization) to enhance degradation of these pesticides from polluted soil A. The results showed that both solarization and biosolarization enhanced the degradation rates of endosulfan, bifenthrin and tolclofos-methyl compared with the control. Most of the studied pesticides showed similar behavior under solarization and biosolarization conditions. However, chlorpyrifos was degraded to a greater extent in the solarization than in biosolarization treatment. The results obtained point to the interest in the use of organic amendment in reducing the pollution of groundwater by pesticide drainage and in the use of solarization and biosolarization in reducing the persistence of pesticides in soil.

Leaching potential of several insecticides and fungicides through disturbed clay-loam soil columns

A laboratory study was conducted in order to determine the leaching potential of five insecticides and six fungicides commonly used during pepper cultivation by use of disturbed soil columns. The tested compounds were pyridaben, pyriproxyfen, tebufenpyrad, buprofezin and pirimicarb (insecticides/acaricides) and azoxyxtrobin, kresoxim-methyl, hexaconazole, tebuconazole, triadimenol, and pyrimethanil (fungicides). For this purpose, 100 µg of each pesticide were added to columns (n = 5) filled with 150 g of a clay loam soil and leached with 600 mL of 0.01 M CaCl2 during 10 days. Finally, leachates and soil fractions were analysed for pesticide residues. For insecticides only pirimicarb was found in leachates (48% of the initial amount) while 55% was recovered from the soil layers. For the other studied insecticides, the percentage remaining in the top soil fraction was nearly the total amount added and therefore showing ‘non-leaching’ behaviour. In the case of fungicides 41% of triadimenol and 6% of pyrimethanil were found in leachates. The amount recovered in leachates for the other fungicides was lower than 2%, hexaconazole and tebuconazole exhibiting the higher retention on the upper layer of soil. Therefore, is extremely important to propose methods and conduct to avoid the potential adverse effect of pesticides behaving as ‘leacher’ compounds.

Heterogeneous photocatalytic oxidation of cyprodinil and fludioxonil in leaching water under solar irradiation.

The efficiency of ZnO and TiO(2) suspensions in the photocatalytic degradation of two fungicides (cyprodinil and fludioxonil) in leaching water was investigated. The experiments were carried out at pilot plant scale using compound parabolic collectors under natural sunlight. The blank experiments for both irradiated compounds solutions showed that both oxides strongly enhanced the removal of the fungicides. The addition of an oxidant (Na(2)S(2)O(8)) to the ZnO or TiO(2) increased the rate of photooxidation. The degradation of cyprodinil and fludioxonil followed first order kinetics according to the Langmuir-Hinshelwood model. Complete degradation of both fungicides was achieved within 4 h (t(30W)=18 min) when treated with illuminated ZnO. The disappearance time (DT(75)), when referred to the normalized illumination time (t(30W)), was lower than 40 and 550 min (t(30W)=2 and 40 min) for both fungicides using ZnO or TiO(2), respectively. ZnO appeared to be more effective in cyprodinil and fludioxonil oxidation than TiO(2) probably due to its nonstoichiometry.