Mechanical Engineering

Soil solarization is a non-chemical treatment of agricultural soil for the control of soil-borne pathogens and pests. To be most effective, the solarization process is undertaken when ambient temperatures are highest, often causing growers to lose the most productive time of year. Pre-solarization amendment of soil with organic matter has been shown to raise peak soil temperatures and possibly shorten the time required for effective soil treatment. Reliable predictive tools are necessary to characterize the solarization process and to minimize the opportunity cost incurred by farmers due to growing season abbreviation but current models do not accurately predict temperatures for soils with internal heat generation due the microbial breakdown of the soil amendment. To address the need for a more robust model, a first-order source term was developed in the course of this thesis to model the internal heat source during amended soil solarization. This source term was then incorporated into an existing "soil only" model and validated against data collected from amended soil field trials conducted at the Kearney Agricultural Center. The expanded model outperformed both the existing stable-soil model and a constant source term model, predicting daily peak temperatures to within 0.1˚C during the critical first week of solarization.

The undeveloped potential generation capacity of landfills, wastewater digesters and food digesters is estimated at 600 MW in California and 3,000 MW in the United States. California's 2000 dairies have the potential to produce an estimated 40 million cubic feet of biogas per day, representing a potential generation capacity of about 140 MW. One of the most significant challenges facing the combustion of digester biogas is high NOx emissions. Sulfur in the biogas poisons post-combustion catalysts, rendering them ineffective for reducing NOx emissions. To address this challenge, an integrated pollution capture and microwave system has been developed to reduce NOx emissions from biogas engines. The feasibility of reburning the captured NOx was assessed and the effect of various operating parameters, including temperature, pressure, and reactant composition were determined using chemical equilibrium and kinetic modeling.

Pomaces from tomato paste and wine production are the most abundant fruit processing residues in California. These residues were examined as soil amendments for solarization to promote conditions conducive to soil disinfestation (biosolarization). Simulated biosolarization studies were performed in both aerobic and anaerobic soil environments and soil temperature elevation, pH, and evolution of CO2, H2 and CH4 gases were measured as metrics of soil microbial activity. Tomato pomace amendment induced conditions associated with soil pest inactivation, including elevation of soil temperature by up to 2°C for a duration of 4days under aerobic conditions and a reduction of soil pH from 6.5 to 4.68 under anaerobic conditions. White wine grape pomace amendment showed similar trends but to a lesser extent. Red wine grape pomace was generally less suitable for biosolarization due to significantly lower soil temperature elevations, reduced acidification relative to the other pomaces and induction of methanogenesis in the soil.

This activity is a recommended curriculum for understanding the physical concepts of water bottle rockets culminating in student construction of rockets and competing in the annual MESA day event.  Concepts that are focused on include energy, pressure, Newton's Laws, center of drag, center of mass, flight stability, and momentum.  Included are instructions for an over-the-head water bottle rocket launcher.

Pomaces from tomato paste and wine production are the most abundant fruit processing residues in California. These residues were examined as soil amendments for solarization to promote conditions conducive to soil disinfestation (biosolarization). Simulated biosolarization studies were performed in both aerobic and anaerobic soil environments and soil temperature elevation, pH, and evolution of CO2, H2 and CH4 gases were measured as metrics of soil microbial activity. Tomato pomace amendment induced conditions associated with soil pest inactivation, including elevation of soil temperature by up to 2°C for a duration of 4days under aerobic conditions and a reduction of soil pH from 6.5 to 4.68 under anaerobic conditions. White wine grape pomace amendment showed similar trends but to a lesser extent. Red wine grape pomace was generally less suitable for biosolarization due to significantly lower soil temperature elevations, reduced acidification relative to the other pomaces and induc...

The aims of this study were to identify thermophilic microbial communities that degrade green waste in the presence of the ionic liquids (IL) tetrabutylphosphonium chloride and tributylethylphosphonium diethylphosphate and examine preservation methods for IL-tolerant communities. High-solids incubations with stepwise increases in IL concentration were conducted to enrich for thermophilic IL-tolerant communities that decomposed green waste. 16S rRNA sequencing of enriched communities revealed microorganisms capable of tolerating high levels of IL. Cryogenic preservation of enriched communities reduced the IL tolerance of the community and decreased the relative abundance of IL-tolerant organisms. The use of cryoprotectants did not have an effect on microbial activity on green waste of the stored community. A successful approach was developed to enrich communities that decompose green waste in thermophilic high-solids environments in the presence of IL. Alternative community storage a...

Biosolarization is a fumigation alternative that combines passive solar heating with amendment-driven soil microbial activity to temporarily create antagonistic soil conditions, such as elevated temperature and acidity, that can inactivate weed seeds and other pest propagules. The aim of this study was to use a mesocosm-based field trial to assess soil heating, pH, volatile fatty acid accumulation, and weed seed inactivation during biosolarization. Biosolarization for 8 days using 2% mature green waste compost and 2 or 5% tomato processing residues in the soil resulted in accumulation of volatile fatty acids in the soil, particularly acetic acid, and >95% inactivation of Brassica nigra and Solanum nigrum seeds. Inactivation kinetics data showed that near complete weed seed inactivation in soil was achieved within the first 5 days of biosolarization. This was significantly greater than the inactivation achieved in control soils that were solar heated without amendment or were amen...

Microorganisms involved in biomass deconstruction are an important resource for organic waste recycling and enzymes for lignocellulose bioconversion. The goals of this study were to examine the impact of nitrogen amendment on microbial community restructuring, secretion of xylanases and endoglucanases, and potential for biomass deconstruction. Communities were cultivated aerobically at 55 °C on green waste (GW) amended with varying levels of NH 4 Cl. Bacterial and fungal communities were determined using 16S rRNA and ITS region gene sequencing and PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) was applied to predict relative abundance of genes involved in lignocellulose hydrolysis. Nitrogen amendment significantly increased secretion of xylanases and endoglucanases, and microbial activity; enzyme activities and cumulative respiration were greatest when nitrogen level in GW was between 4.13-4.56 wt% (g/g), but decreased with higher nitrogen levels. The microbial community shifted to one with increasing potential to decompose complex polymers as nitrogen increased with peak potential occurring between 3.79-4.45 wt% (g/g) nitrogen amendment. The results will aid in informing the management of nitrogen level to foster microbial communities capable of secreting enzymes that hydrolyze recalcitrant polymers in lignocellulose and yield rapid decomposition of green waste.

Soil biosolarization (SBS) is a pest control technique that combines passive solar heating and fermentation of amended organic matter. The extreme soil conditions generated during SBS could decrease microbial biomass and restructure the soil microbiome, which could impact soil quality. Digestates from anaerobic digesters may harbor microbial communities tolerant of the oxygen, moisture, and temperature stresses encountered during SBS as these conditions may also occur in digesters. Digestate microbial communities may contribute to soil fermentation during SBS and affect organic matter turnover in soils treated with SBS. The objective of this study was to assess the effect of SBS on soil microbial diversity and quantity when solid digestates from thermophilic (TD) and mesophilic (MD) anaerobic digesters were used as soil amendments. In the soils amended with TD, communities showed the greatest divergence from the initial soil state whereas MD amendment resulted in a microbiome more similar to the non-amended soil. The microbial biomass of the biosolarized soils was significantly greater than the non-amended, solar-heated soil. The microbial biomass in the biosolarized soils was dominated by K-strategic or "native" species. Solar heating of the non-amended soil mainly affected "native" species, leading to conditions where other opportunistic species become more dominant. Further studies are needed to elucidate whether the persistent microbes in the soil are benign or pathogenic and to understand their roles in pest inactivation and nutrient cycling during and following SBS.

Anaerobic digestion is an organic waste bioconversion process that produces biofuel and digestates. Digestates have potential to be applied as soil amendment to improve properties for crop production including phytonutrient content and pest load. Our objective was to assess the impact of solid anaerobic digestates on weed seed inactivation and soil quality upon soil biosolarization (a pest control technique that combines solar heating and amendment-induced microbial activity). Two solid digestates from thermophilic (TD) and mesophilic (MD) digesters were tested. The solarized TD-amended samples presented significantly higher mortality of Brassica nigra (71%, P = 0.032) than its equivalent incubated at room temperature. However, biosolarization with digestate amendment led to decreased weed seed mortality in certain treatments. The plant-available water, total C, and extractable P and K were significantly increased (P < 0.05) in the incubated amended soils. The results confirm the potential of digestates as beneficial soil amendments. Further studies are needed to elucidate the impacts of digestate stability on biosolarization efficacy and soil properties.

Soil biosolarization is a promising alternative to conventional fumigation. Volatile fatty acids (VFAs) produced in the soil through fermentation of amended organic matter can affect pest inactivation during biosolarization. The objective was to determine how soil amended with organic wastes that were partially stabilized through either composting or anaerobic digestion affected the inactivation of Brassica nigra (BN; a weed) and Fusarium oxysporum f. sp. lactucae (FOL; a phytopathogenic fungus). The mortality of BN seeds in the biosolarized soil was 12% higher than in the solarized soil, although this difference was not significant. However, a significant correlation between BN mortality and VFA accumulation was observed. The number of FOL colony-forming units (CFU) in solarized samples at 5 cm was 34 CFU g of soil, whereas in the biosolarized samples levels were below the limit of quantification. At 15 cm, these levels were 100 CFU g for solarized samples and &lt; 50 CFU g of soil...

Conventional solarization and biosolarization with mature compost and tomato processing residue amendments were compared with respect to generation of pesticidal conditions and tomato ( Solanum lycopersicum L.) plant growth in treated soils. Soil oxygen depletion was examined as a response that has previously not been measured across multiple depths during biosolarization. For biosolarized soil, volatile fatty acids were found to accumulate concurrent with oxygen depletion, and the magnitude of these changes varied by soil depth. Two consecutive years of experimentation showed varying dissipation of volatile fatty acids from biosolarized soils post-treatment. When residual volatile fatty acids were detected in the biosolarized soil, fruit yield did not significantly differ from plants grown in solarized soil. However, when there was no residual volatile fatty acids in the soil at the time of planting, plants grown in biosolarized soil showed a significantly greater vegetation amount...

Current agricultural soil pathogen control methods that rely on fumigation with toxic synthetic chemicals are not sustainable. Combining soil organic matter amendment with soil hydrothermal treatment via solarization is a biological pest control alternative to chemical fumigation. The application and bioconversion of readily-available organic amendment resources, such as green wastes (GW), have not been considered. The impact of compost inoculum on the bioconversion of GW to pesticidal volatile fatty acids (VFAs) in soil during solarization was investigated. Laboratory experiments showed a significant positive effect of compost inoculum at a rate ≥ 1% on aerobic and anaerobic decomposition of GW, but only when soils were heated. Field trials showed that GW induced conditions in soil that supported fermentation and resulted in accumulation of VFAs. When soil was inoculated with compost, VFA accumulation was enhanced at increasing soil depth. The results indicate that green waste bioconversion can be used to improve pest control conditions in soil during solarization. The findings have environmental implications on green waste management and use of toxic synthetic chemical fumigants.

Aims. Soil biosolarization (SBS) is a pest control technology that includes the incorporation of organic matter into soil prior to solarization. The objective of this study was to measure the impact of the initial soil microbiome on the temporal evolution of genes encoding lignocellulose-degrading enzymes during SBS. Methods and Results. SBS field experiments were completed using green waste as a soil amendment and in the presence and absence of compost activating inoculum. Samples were collected over time and at two different soil depths for measurement of the microbial community and the predicted lignocellulosic-degrading microbiome. Compost inoculum had a significant positive effect on several predicted genes encoding enzymes involved in cellulose, hemicellulose and lignin degradation. These included betaglucosidase, endo-1,3(4)-beta-glucanase, alpha-galactosidase and laccase. Conclusion. Amendment of microorganisms found in compost to soil prior to soil biosolarization enhanced the degradation potential of cellulose, hemicellulose and lignin found in green waste. Significance and Impact of Study. The type of organic matter amended and its biotransformation by soil microorganisms impact the efficacy of SBS. The results suggest that co-amending highly recalcitrant biomass with microorganisms found in compost improves biomass conversion during soil biosolarization.

Regulatory pressure along with environmental and human health concerns drive the development of soil fumigation alternatives such as soil biosolarization (SBS). SBS involves tarping soil that is at field capacity with a transparent film following amendment with certain organic materials. Heating via the greenhouse effect results in an increase of the soil temperature. The organic amendments can promote microbial activity that can enhance pest inactivation by depleting oxygen, producing biopesticidal fermentation products, and competing with pests. The properties of the organic amendments can heavily influence the type and magnitude of these effects. This study evaluated the viability of chitin as a novel SBS soil amendment to influence soil fungal and bacterial microbial communities, including control of the plant pathogen Fusarium oxysporum f.sp. lactucae (FOL). Changes to FOL and the broader soil microbiota were monitored in response to biosolarization using 0.1% (by dry weight) amendment with chitin (Rootguard). FOL suppression was only observed in chitin amended soils that were incubated at room temperature, not under solarized conditions. Conversely, it decreased solarization efficacy in the upper (0-10 cm) soil layer. The presence of chitin also showed increase in FOL under anaerobic and fluctuating temperature regime conditions. Biosolarization with chitin amendment did exhibit an impact on the overall soil microbial community. The fungal genus Mortierella and the bacterial family Chitinophagaceae were consistently enriched in biosolarized soils with chitin amendment. This study showed low potential FOL suppression due chitin amendment at the studied levels. However, chitin amendment showed a higher impact on the fungal community than the bacterial community. The impact of these microbial changes on crop protection and yields need to be studied in the long-term.

Biosolarization is an integrated pest management strategy that combines soil solarization with organic amendment application. In the present study, soil samples were taken after biosolarization using tomato pomace and green waste compost (GWC) amendments and analyzed to elucidate changes to the soil microbiome, including both fungal and bacterial communities. Following a field trial wherein soil mesocosms were biosolarized for 8 days, the effects of soil depth and soil amendments were assessed via sequencing and bioinformatic analysis of 16S rRNA gene and ITS2 amplicons generated from soil microbial genomic DNA. Structural and network analyses were used to quantify differences in microbiota between treatments and these results were correlated with measured levels of volatile fatty acids in the soils. The results showed that biosolarization had a stronger impact on the bacterial community relative abundance profile than on the fungal community at the phylum and order levels. However, at the operational taxonomic units (OTUs) level, biosolarization treatment had a significant impact on both fungal and bacterial communities, across soil depth and GWC addition. Co-occurrence microbial network analysis revealed a unique circular network consisting of 8 discrete clusters. Correlation between the clusters and soil volatile fatty acid (VFA) production suggested that the bacterial Clostridium, Weissella and Acetobacter genera tolerate, and perhaps drive, VFA accumulation. Notable fungal community effects included significantly reduced relative abundance within genera known to contain plant pathogenic members, such as Gibberella, Haematonectria, Fusarium, Aspergillus and Alternaria.

Aims: The aims of this study were to identify thermophilic microbial communities that degrade green waste in the presence of the ionic liquids (IL) tetrabutylphosphonium chloride and tributylethylphosphonium diethylphosphate and examine preservation methods for IL tolerant communities. Methods and Results: High-solids incubations with step-wise increases in IL concentration were conducted to enrich for thermophilic IL tolerant communities. 16S rRNA sequencing of enriched communities revealed microorganisms capable of tolerating high levels of IL. Cryogenic preservation of enriched communities reduced the IL tolerance of the community and decreased the relative abundance of IL tolerant organisms. The use of cryoprotectants did not have an effect on microbial activity on green waste of the stored community. Conclusions: Step-wise increases in IL facilitated the enrichment of thermophilic, IL tolerant microbial communities that decomposed green waste. Alternative community storage and revival methods are necessary for maintenance and recovery of IL-tolerant communities. Significance and Impact of Study: A successful approach was developed to enrich communities that decompose green waste in thermophilic high-solids environments in the presence of IL. The enriched communities provide a targeted source of enzymes for the bioconversion of IL-pretreated green waste for conversion to biofuels.

Soil biosolarization (SBS) is an alternative technique for soil pest control to standard techniques such as soil fumigation and soil solarization (SS). By using both solar heating and fermentation of organic amendments, faster and more effective control of soilborne pathogens can be achieved. A circular economy may be created by using the residues of a given crop as organic amendments to biosolarize fields that produce that crop, which is termed circular soil biosolarization (CSBS). In this study, CSBS was employed by biosolarizing soil with amended tomato pomace (TP) residues and examining its impact on tomato cropping under conditions of abiotic stresses, specifically high salinity and nitrogen deficiency. The results showed that in the absence of abiotic stress, CSBS can benefit plant physiological performance, growth and yield relative to SS. Moreover, CSBS significantly mitigated the impacts of abiotic stress conditions. The results also showed that CSBS impacted the soil micro...

One of the main and most challenging steps in the design and analysis of a mechatronics system is to generate a computer model. This paper explores the fundamental theory, the methodology and the process from conceptual ideas to practical realization. Using a multienergetic approach that allows the modeling of interdisciplinary models, it explores the theory and method to automate the process of the generation of the differential equations and how to automate the derivation of transfer functions. The approach is discussed for linear and nonlinear systems. The generation of a computer model takes new dimensions when that model contains mixed energy domains such as electromechanical, electrohydraulic, thermo-fluid, and electronic control systems all together. These are typical of mechatronics applications. This paper explores the bond graph technique as a modeling tool to generate state space models or non-linear models together with software tools. CAMP-G (Computer Aided Modeling Program with Graphical input) has been developed in order to generate computer models automatically and have them integrated with MATLAB-SIMULINK as simulation tools. Several aspects of mechatronics systems design have been investigated in order to focus on which areas the bond graph modeling technique can help engineers in the process of creating mechatronics systems from scratch. Towards this end, the paper deals with computer-generated models of sensors, actuators, and multidisciplinary complex physical systems.