Ruihong Zhang

BIODIESEL FROM WASTE SALMON OIL

Salmon oils separated from salmon processing waste and hydrolysate and their derived methyl esters were analyzed and compared with corn oil and its methyl ester. These materials were characterized for their fatty acid profiles, viscosity, volatility, thermal properties, low temperature properties, oxidative stability, and heating value. The salmon oil methyl esters contained 26.64% saturated fatty acid methyl esters compared to 13.68% for corn oil methyl ester. Salmon oil methyl esters also contained relatively high concentrations of eicosapentaenoic acid (C20:5) and docosahexaenoic (C22:6) acid methyl esters. Despite these differences in fatty acid composition, salmon and corn oil methyl esters had comparable physical properties. In addition, the methyl esters produced from salmon oils extracted from fish processing by-products and hydrolysate showed little difference in their physical properties.

Anaerobic Codigestion of Food Waste and Dairy Manure

Codigestion of food waste and dairy manure in a mesophilic, completely mixed anaerobic digester was studied in the laboratory. Two mixtures of food waste and dairy manure were tested with the first mixture composed of 32% food waste (based on VS content) and 68% dairy manure and the second mixture composed of 48% food waste and 52% dairy manure. For each mixture, the performance of the anaerobic digester was evaluated at two different organic loading rates (2 and 4 gVS/L.day). The results showed that at 2 gVS/L.day, the digesters fed with both mixtures were stable. The digester fed with the second mixture had higher biogas yield and production rate (504 mL/gVS and 1.01 L/L.day, respectively) than the digester fed with the first mixture (398 mL/gVS and 0.78 L/L.day, respectively). At 4 gVS/L.day, the digester fed with the first mixture had stable performance but the digester fed with the second mixture had variable performance as shown by large fluctuation in daily biogas production. The average biogas yield was 476 and 504 mL/gVS, respectively, and biogas production rate was 1.91 and 2.02 L/L.day. No significant differences were found for VS removals between different conditions tested. Based on the measurement data, the energy generation potential of a farm digester was calculated for co-digestion of different amounts of manure and food waste.

Biodiesel Production from Fish Oil

Salmon oil, a byproduct of salmon processing, was investigated as a feedstock for biodiesel production via transesterification. Two different types of salmon oil were tested: acidified salmon oil extracted from salmon hydrolysate and non-acidified salmon oil extracted directly from fresh salmon waste. Optimal amounts of chemicals required were determined to give the highest biodiesel yield from each oil using batch production procedures. Due to the high acid value of salmon oil, using alkaline-catalyzed transesterification was not efficient. Therefore a two–step process was applied, in which sulfuric acid-catalyzed pretreatment was used in the first step to reduce the acid value from 12.04 to 3 mg KOH/g oil. Then, in the second step, KOH- catalyzed transesterification was applied. All experiments were performed at a temperature of 52 ±2oC with a mixing intensity of 600 rpm. Based on the total weight of salmon oil used, the maximum biodiesel yield of 99% was achieved using a total methanol/ molar ratio of 9.2 and KOH of 0.5% (w/w). It was calculated that the ester loss during washing and drying steps was 15% at the maximum due to the formation of emulsion. This loss could be reduced in practical application by better design of washing and drying techniques. A preliminary economic analysis showed that the cost of biodiesel production was almost twice that of soybean biodiesel.

Drying and decontamination of raw pistachios with sequential infrared drying, tempering and hot air drying

Pistachio nuts have been associated with outbreaks of foodborne disease and the industry has been impacted by numerous product recalls due to contamination with Salmonella enterica. The current hot air drying of pistachios has low energy efficiency and drying rates, and also does not guarantee the microbial safety of products. In the study described herein, dehulled and water-sorted pistachios with a moisture content (MC) of 38.14% (wet basis) were dried in a sequential infrared and hot air (SIRHA) drier to <9% MC. The decontamination efficacy was assessed by inoculating pistachios with Enterococcus faecium, a surrogate of Salmonella enterica used for quality control in the almond industry. Drying with IR alone saved 105min (34.4%) of drying time compared with hot air drying. SIRHA drying of pistachios for 2h with infrared (IR) heat followed by tempering at a product temperature of 70°C for 2h and then by hot air drying shortened the drying time by 40min (9.1%) compared with drying by hot air only. This SIRHA method also reduced the E. faecium cell population by 6.1-logCFU/g kernel and 5.41-logCFU/g shell of pistachios. The free fatty acid contents of SIRHA dried pistachios were on par with that of hot air dried samples. Despite significant differences in peroxide values (PV) of pistachio kernels dried with the SIRHA method compared with hot air drying at 70°C, the PV were within the permissible limit of 5Meq/kg for edible oils. Our findings demonstrate the efficacy of SIRHA drying in achieving simultaneous drying and decontamination of pistachios.

Fuel Properties and Characteristics of Saline Biomass

Integrated farm drainage management (IFDM) systems employ sequential reuse of water with biomass production to help control saline groundwater and improve the sustainability of arid land irrigated agriculture. Currently operating near Five Points, CA is a 640 acre IFDM demonstration project. Subsurface drainage water is reused to irrigate plants of increasing salt tolerance and produce crops which could be utilized in energy conversion. Combustion properties of biomass are influenced by the presence of chlorine, alkali and other metals, all of which may increase in concentration with drainage water reuse. Physical, chemical, structural, and fuel properties were determined for three species of biomass irrigated with saline drainage water, including two woods (Athel and Eucalyptus) and one grass (Jose Tall Wheatgrass). For each species, the as-harvested moisture content, heating value, proximate analysis (ash, volatiles, and fixed carbon), and concentration of acid-insoluble ash were determined. Wood and bark dry matter fractions were determined on both a volume and a mass basis along with apparent wood density. Structural carbohydrate fractions were found through NDF, ADF, and lignin determinations. Ultimate, ash, and water soluble alkali analyses and heavy metals and trace element concentrations were also conducted for each biomass species. Combustion fuel properties including ash volatilization, ash fusibility, and ash sulfur decomposition temperatures were determined. The Jose Tall Wheatgrass has high fouling potential for combustion systems, and the Athel exhibits high uptake of calcium and alkali sulfates.

Assessing Energy Pathways for Forestry Residue Utilization

Technical and economic assessment of fast pyrolysis, gasification and pelleting systems were performed. Required components were determined for each technology. These included pretreatment and primary conversion equipment, intermediate product and final product recovery systems, and in some cases secondary conversion equipment. Capital, operating and maintenance costs were obtained directly from manufacturers or from literature related to engineering economic assessments of similar technologies. A spreadsheet model was developed to determine required revenue, in US (2007) dollars, for each final product (electricity, bio-oil or pellets). Sensitivity of product cost to feedstock cost and plant availability was determined. Options were compared based on production cost per dry tonne of chips converted over a range of feedstock throughputs, given zero feedstock cost.

Kinetic Modeling for Enzymatic Hydrolysis of Pretreated Creeping Wild Ryegrass

A semimechanistic multi-reaction kinetic model was developed to describe the enzymatic hydrolysis of a lignocellulosic biomass, Creeping Wild Ryegrass (Leymus triticoides) (CWR). This model incorporated one homogeneous reaction of cellobiose to glucose and two heterogeneous reactions of cellulose to cellobiose and cellulose to glucose. Adsorption of cellulase onto pretreated CWR during enzymatic hydrolysis was modeled via a Langmuir adsorption isotherm. This is the first kinetic model which incorporated the negative role of lignin (nonproductive adsorption) using a Langmuir-type isotherm adsorption of cellulase onto lignin. The model also reflected the competitive inhibitions of cellulase by glucose and cellobiose. The Matlab optimization function of “lsqnonlin” was used to fit the model and estimate kinetic parameters based on experimental data generated under typical conditions (8% solid loading and 15 FPU/g-cellulose enzyme concentration without the addition of background sugars). The model showed high fidelity for predicting cellulose hydrolysis behavior over a broad range of solid loading (4-12%, w/w, dry basis), enzyme concentration (15-150 FPU/g-cellulose), sugar inhibition (glucose of 30 and 60 mg/mL and cellobiose of 10 mg/mL). In addition, sensitivity analysis showed that the incorporation of the nonproductive adsorption of cellulase onto lignin significantly improved the predictability of the kinetic model. Our model can serve as a robust tool for developing kinetic models for system optimization of enzymatic hydrolysis, hydrolysis reactor design, and/or other hydrolysis systems with different type of enzymes and substrates.

Integrated Rotary Drum and Anaerobic Phased Solids Digester System for Biogas Production from Municipal Solid Wastes

This research was conducted to develop an integrated rotary drum reactor (RDR)-Anaerobic Phased Solids (APS) Digester system for the treatment of municipal solid waste (MSW) to produce biogas energy and achieve waste degradation. The RDR was used to provide pretreatment and separation of the organics from MSW and then the organics were digested in the APS-Digester system for biogas production. The solid retention time in the RDR was 3 d. The organics generated from the RDR contained 50% total solids (TS) and 36% volatile solids (VS) on a wet basis. The APS-Digester system is a two-phase, high-solids anaerobic digestion system which consists of four sequentially loaded batch hydrolysis reactors and one continuous biogasification reactor. The APS-Digester system was started at an organic loading rate (OLR) of 3.1 gVS L-1 d-1 and operated at three higher OLRs of 4.6, 7.7 and 9.2 gVS L-1 d-1. At the OLR of 9.2 gVS L-1 d-1 the system’s biogas production rate was 3.5 L L-1 d-1 and the biogas and methane yields were 0.38 and 0.19 L gVS-1, respectively. Anaerobic digestion resulted in 38% TS reduction and 53% VS reduction in the organic solids. The changes of pH and volatile fatty acids (VFA) in all the reactors were measured. It was found that the total VFA concentration reached a peak value of 15000 mg L-1 as acetic acid in the first three days of batch digestion and later decreased to about 500 mg L-1. The APS-Digester system remained stable at each OLRs for over 100 d with a steady pH of 7.8 throughout.

Rheological and Thermal Properties of Salmon Processing Byproducts

Salmon oils separated from salmon processing waste and hydrolysate and their derived biodiesel were analyzed and compared with corn oil and its biodiesel. These materials were characterized for their fatty acid profiles, viscosity, volatility, thermal properties, low temperature properties, oxidative stability, and heating value. The salmon oil methyl esters contained 26.64% saturated fatty acid methyl esters compared to 13.68% for corn oil methyl ester. Also, salmon oil methyl esters contained relatively high concentrations of eicosapentaenoic acid (C20:5) and docosahexaenoic (C22:6) acid methyl esters. Despite these differences in fatty acid composition, salmon and corn oil methyl esters had comparable physical properties. In addition, the methyl esters produced from acidified and non-acidified salmon oils showed little difference in their physical properties.