D. Raj Raman

Laboratory scale evaluation of volatile organic compound emissions as indication of swine carcass degradation inside biosecure composting units.

Biosecure livestock mortality composting systems have been used to dispose of diseased livestock mortalities. In those types of system, visual inspection of carcass degradation is not possible and monitoring VOCs (volatile organic compounds) released by carcasses is a new approach to assess progress of the composting process. In this study, field-scale livestock mortality composting systems were simulated and a laboratory scale composting system with aerobic and anaerobic test units was designed to collect VOC samples from the headspace of decaying plant materials (70 g dry weight) and swine tissues (70 g dry weight) at controlled operating temperatures. Headspace samples were collected with SPME (solid phase microextraction) and analyzed by a GC-MS (gas chromatography-mass spectrometry) system. Among the 43 VOCs identified, dimethyl disulfide, dimethyl trisulfide, and pyrimidine were found to be marker compounds of the mortality composting process. These compounds were only found to be produced by decaying swine tissues but not produced by decaying plant materials. The highest marker VOC emissions were measured during the first three weeks, and VOCs were not detected after the 6th week of the process, which indicates degradation processes were completed and compost materials microbially stabilized (no additional VOC production). Results of respiration tests also showed that compost materials were stabilized. Results of this study can be useful for field-scale composting operations but more studies are needed to show the effects of size and aeration rate of the composting units.

Fungal production of eicosapentaenoic and arachidonic acids from industrial waste streams and crude soybean oil

A series of polyunsaturated fatty acids (PUFAs), including 5,8,11,14,17-cis-eicosapentaenoic acid (EPA) and 5,8,11,14-cis-arachidonic acid (ARA), have widespread nutritional and pharmaceutical value. This study investigated the potential production of the two economically important fatty acids with a fungal fermentation process. The substrates for the fungal fermentation process were crude soybean oil (SBO), a sucrose waste stream (SWS) and a soymeal waste stream (SMW). Glucose (GLU) was used as a substrate in control groups. The microorganisms used were Mortierella elongata NRRL 5513 and Pythium irregulare ATCC 10951. The use of P. irregulare ATCC 10951 is preferred since it produced high levels and reasonable ratios of EPA and ARA at various temperatures (12, 18 and 24°C). An advantage of P. irregulare was its ability to produce EPA at room temperature, which is desirable for commercial applications. Soybean oil had a unique characteristic of stabilizing pH; the optimal initial pH was 6.0. An emulsifier, Tween 80, allowed much greater dispersion of the SBO in aqueous broth and helped increase EPA and ARA production. In experiments exploring the combination effects of sugars (1, 2 and 3%) with soybean oil (4%) and Tween 80 (0.2%) at 12, 18 and 24°C, EPA yields of SMW + SBO were significantly higher than those of GLU + SBO and SWS + SBO. The greatest EPA production (1400 mg/l) was obtained at 12°C (1% SMW, 4% SBO). Cultivation of P. irregulare at reduced temperatures increased lipid unsaturation. The highest ARA level appeared at 18°C − SMW + SBO (2000 mg/l), which was a statistically interactive temperature-media combination. The ARA/EPA ratio in this study ranged from 0.2 to 4.0, which would be reasonable for food additive or supplement applications, e.g infant formula.

Ultrasonic pretreatment of corn slurry for saccharification: a comparison of batch and continuous systems.

The effects of ultrasound on corn slurry saccharification yield and particle size distribution was studied in both batch and continuous-flow ultrasonic systems operating at a frequency of 20 kHz. Ground corn slurry (28%w/v) was prepared and sonicated in batches at various amplitudes (192-320 microm(peak-to-peak (p-p))) for 20 or 40s using a catenoidal horn. Continuous flow experiments were conducted by pumping corn slurry at various flow rates (10-28 l/min) through an ultrasonic reactor at constant amplitude of 12 microm(p-p). The reactor was equipped with a donut shaped horn. After ultrasonic treatment, commercial alpha- and gluco-amylases (STARGEN 001) were added to the samples, and liquefaction and saccharification proceeded for 3h. The sonicated samples were found to yield 2-3 times more reducing sugars than unsonicated controls. Although the continuous flow treatments released less reducing sugar compared to the batch systems, the continuous flow process was more energy efficient. The reduction of particle size due to sonication was approximately proportional to the dissipated ultrasonic energy regardless of the type of system used. Scanning electron microscopy (SEM) images were also used to observe the disruption of corn particles after sonication. Overall, the study suggests that both batch and continuous ultrasonication enhanced saccharification yields and reduced the particle size of corn slurry. However, due to the large volume involve in full scale processes, an ultrasonic continuous system is recommended.

The kinetics of nitrate uptake from flowing solutions by rice : influence of pretreatment and light

Abstract The kinetics of nitrate (NO − 3 ) uptake by intact 23 day old rice plants was studied by measuring the depletion of NO − 3 in solutions flowing over the plant roots. A Michaelis-Menten kinetic model was applied, allowing the uptake kinetics to be characterized by two parameters: the apparent half-velocity constant, K m , and the apparent maximum uptake rate, V max . A propagation of uncertainty calculation revealed that the kinetic parameters could be determined with a high degree of accuracy; the standard deviation in K m was typically 15% of the K m value; the standard deviation in V max was typically 7% of the V max value. The plants were exposed to full nutrient solutions containing NO − 3 at 50, 200, 500 and 800 μ m for 24 h prior to kinetic testing, and both K m and V max were found to vary with pretreatment NO − 3 concentration, [NO − 3 ]; plants pretreated at high [NO − 3 ] had lower V max and higher K m values than plants pretreated at lower [NO − 3 ]. However, the variations in V max were more consistent than those in K m . These changes in the kinetic parameters reflect an uptake system which is capable of compensating for changes in the external [NO − 3 ] to maintain a virtually constant NO − 3 uptake rate in the range studied. Changes in K m and V max begin within 4 h of a change in [NO − 3 ]. Light deprivation during pretreatment in 200 μ m NO − 3 resulted in a complete cessation of NO − 3 uptake; 4–8 h of illumination were required before the uptake resumed, and uptake rates had not yet reached normal levels 8 h after the resumption of illumination.

Air Sampling and Analysis Method for Volatile Organic Compounds (VOCs) Related to Field-Scale Mortality Composting Operations

In biosecure composting, animal mortalities are so completely isolated during the degradation process that visual inspection cannot be used to monitor progress or the process status. One novel approach is to monitor the volatile organic compounds (VOCs) released by decaying mortalities and to use them as biomarkers of the process status. A new method was developed to quantitatively analyze potential biomarkers--dimethyl disulfide, dimethyl trisulfide, pyrimidine, acetic acid, propanoic acid, 3-methylbutanoic acid, pentanoic acid, and hexanoic acid--from field-scale biosecure mortality composting units. This method was based on collection of air samples from the inside of biosecure composting units using portable pumps and solid phase microextraction (SPME). Among four SPME fiber coatings, 85 microm CAR/PDMS was shown to extract the greatest amount of target analytes during a 1 h sampling time. The calibration curves had high correlation coefficients, ranging from 96 to 99%. Differences between the theoretical concentrations and those estimated from the calibration curves ranged from 1.47 to 20.96%. Method detection limits of the biomarkers were between 11 pptv and 572 ppbv. The applicability of the prepared calibration curves was tested for air samples drawn from field-scale swine mortality composting test units. Results show that the prepared calibration curves were applicable to the concentration ranges of potential biomaker compounds in a biosecure animal mortality composting unit.

Effect of Agricultural Antibiotics on the Persistence and Transformation of 17β-Estradiol in a Sequatchie Loam

A laboratory incubation study was conducted to investigate the effect of agricultural antibiotics (sulfamethazine, tylosin, and chlortetracycline) on the persistence and transformation of 17β-estradiol in Sequatchie loam. We measured concentrations of 17β-estradiol and its primary metabolite (estrone) in soils spiked with antibiotics and 17β-estradiol. Dehydrogenase activity (DHA) was also measured as an indicator of the total microbial activity of the soils. The presence of antibiotics significantly decreased transformation of 17β-estradiol to estrone. There was a positive correlation between the DHA and the concentrations of estrone in soil spiked with 17β-estradiol only, implying that the reaction is mainly catalyzed by dehydrogenases. However, the positive correlation was weakened in soil spiked with 17β-estradiol and antibiotics together. We recommend that any study evaluating the fate and transport of estrogenic hormones in soil should include the effect of agricultural antibiotics because antibiotics and estrogenic hormones are commonly excreted together in environmental samples.

Development and validation of a technoeconomic analysis tool for early-stage evaluation of bio-based chemical production processes.

By using cost correlations and standard scale-factors, a spreadsheet-based early-stage cost estimation tool was developed. Named BioPET (Biorenewables Process Evaluation Tool), this tool allows users to specify up to seven primary unit operations--fermentation, separation, three catalytic stages, and purification--along with key parameters for each. BioPET then computes an estimated minimum selling price for the pathway. Model validation was conducted by selecting three molecules (ethanol, succinic acid, and adipic acid), and comparing BioPETs results to literature values and to results from a commercial process design tool. BioPET produced virtually identical prices to the process design tool, although the costs were not identically distributed amongst the categories. BioPET produced estimates that were within 40% of other literature values at low feedstock costs, and within 5% at high feedstock costs.

Midwest vision for sustainable fuel production.

This article charts the progress of CenUSA Bioenergy, a USDA-NIFA-AFRI coordinated agricultural project focused on the North Central region of the US. CenUSA’s vision is to develop a regional system for producing fuels and other products from perennial grass crops grown on marginally productive land or land that is otherwise unsuitable for annual cropping. This article focuses on contributions CenUSA has made to nine primary systems needed to make this vision a reality: feedstock improvement; feedstock production on marginal land; feedstock logistics; modeling system performance; feedstock conversion into biofuels and other products; marketing; health and safety; education, and outreach. The final section, Future Perspectives, sets forth a roadmap of additional research, technology development and education required to realize commercialization.

Evaluation of Ultrasonic Pretreatment on Anaerobic Digestion of Different Animal Manures

This article addresses the effect of ultrasonication as a pretreatment to anaerobic digestion of four types of animal manure, including swine slurry, beef feedlot manure, dairy manure slurry, and separated dairy manure effluent. The effect of ultrasonication on soluble chemical oxygen demand (SCOD) and biochemical methane potential (BMP) were determined, and the energy efficiency of ultrasonic pretreatment was evaluated. Ultrasonic pretreatment was applied at two amplitudes (80 and 160 µmpp) and at two time settings (15 and 30 s) to each of the four manure types. The SCOD of each manure sample was determined before and after ultrasonic pretreatment. In addition, BMP trials were run on each waste with and without ultrasonic pretreatment. As part of the BMP, biogas production was measured and analyzed for methane content and cumulative methane production. Ultrasonic pretreatment of swine slurry, beef feedlot manure, dairy manure slurry, and separated dairy manure effluent increased the average SCOD up to 23%, 92%, 59%, and 33%, respectively, and the average methane yield up to 56%, 43%, 62%, and 20%, respectively. Increasing the ultrasonic amplitude and treatment time resulted in an increase in manure SCOD and methane production; the greatest methane production was obtained using the ultrasonic pretreatment at the highest power and longest treatment time. The observed greatest methane production from swine slurry, beef feedlot manure, dairy manure slurry, and separated dairy manure effluent were 394, 230, 226, and 340 mL CH4 g-1 VS, respectively. In contrast, the greatest energy efficiency was obtained with the lowest ultrasonic amplitude combined with the shortest treatment time.

Development of a Bench-Scale Air Sparged Continuous Flow Reactor for Struvite Precipitation from Two Different Liquid Swine Manure Storage Systems

Forced precipitation of struvite (MgNH4PO4 . 6H2O) can reduce dissolved reactive phosphorus (DRP) in swine manure slurries. Optimization of this process requires that the swine manure slurry pH be increased, that magnesium be added, and that sufficient reaction time be allowed for struvite precipitation. To gather data that could be used for a full-scale continuous-flow struvite precipitation reactor, a bench-scale (14-L) continuous flow reactor was designed, constructed, and tested. The bench-scale reactor used air sparging for both pH adjustment and mixing, used a peristaltic pump to continuously inject magnesium chloride (MgCl2 . 6H2O), and was operated at a 10-min hydraulic retention time. The bench-scale system provided a 95% reduction of DRP in swine manure slurry collected from a concrete storage tank with a permeable cover, and a 78% reduction of DRP in swine manure slurry collected from a shallow under floor pit collection system. A bench-scale up-flow clarifier was designed, constructed, and tested for continuous flow separation of the precipitated struvite in order to provide total phosphorus (TP) removal. The up-flow clarifier was unable to continuously settle struvite particles formed in the bench-scale reactor and provided no significant TP removal through the system. The implication of this work for full-scale systems is discussed.