The rapid increase in concentrated animal feeding operations in South Idaho brought the need for utilization of large amounts of dairy manure. Application of manure to agricultural fields as soil amendment can provide the benefit of increased plant nutrients and organic carbon, and potentially result in the improvement of soil health and mitigation of carbon emission by closing the loop in nitrogen cycling. At the same time, manure can be a source of organic and inorganic contaminants. Here we present results from the bench-to-field lysimeter study on the release of contaminants from dairy manure under typical application and irrigation regime. Intact soil core lysimeters (10 cm diameter, 0.6 m length) were sampled by a tractor-mounted hydraulic soil probe with PVC tubing liners and used for bench scale transport experiment. While field sampling was carried out using passive lysimeters silicon carbide porous cups (2×6 cm, -90 kPa bubbling pressure). For field and laboratory experiments, a representative composted manure was used containing up to 30.7, 9.0, and 47.7 g of N, P, and K per kg of manure, respectively, with the highest potential N:P:K value of the tested samples was equivalent to a fertilizer value of 3:2:6. Manure samples also contained several potential contaminants such as hormones, phytoestrogens, antibiotics, and other veterinary drugs. While phytoestrogens were present in manure in highest amounts relative to all other detected contaminants, once manure was applied they were mitigated by soil and not detected in ground water. Antibiotics and hormones were two groups of contaminants that were consistently present in both bench and field scale lysimeters with concentrations up to 0.02 µg. In addition, groundwater collected from manure applied fields contained elevated sulfate and nitrate concentrations as compared to groundwater collected from synthetic fertilizer applied plots.
The saturated activated carbon fiber (ACF) was regenerated by electro-peroxymonosulfate (E-PMS) process to desorb phenol (PN) from ACF, as well as mineralizing the contaminants in the regeneration solution simultaneously. After the regeneration process, 81.90% of TOC in ACF was removed, and the desorbed PN in the regeneration solution was only 4.11% of [PN]0. Compared with conventional electrochemical (E-Pt), PMS alone and E-PDS regeneration processes, E-PMS regeneration achieved the highest regeneration efficiency and the lowest energy consumption. Further study proved that reactive oxygen species oxidation played a major role in E-PMS process, and the relative contribution of hydroxyl radical, sulfate radical, and singlet oxygen was calculated subsequently. In addition, the migration of main intermediates and oxidation of ACF during the regeneration process were measured. Sample characterization of SEM, BET, Roman, FT-IR, and XRD suggested that ACF was protected under the action of cathode field polarization. The regeneration efficiency of ACF could be improved from 75.69% to 82.53% with PMS three-intervallic dosing. Moreover, ACF could maintain the regeneration efficiency of about 60% after 10 cycles, and the concentration of PN in the solution remained low throughout the cycles. The results indicated that E-PMS process was an efficient and environmentally friendly method for the regeneration of ACF.
The increased toxicity potential associated with waste solvents can hardly be overstated. The use of conventional waste disposal techniques such as incineration, onsite and offsite disposal have been explored; however, these traditional waste disposal approaches tend to increase the overall carbon and ecological footprints. Solvent recovery methods present a better alternative to these conventional approaches to improve industrial processes’ circularity. Emergy is one way to quantify the sustainability of an industrial process. It is defined as the amount of available energy (exergy) of one kind that is directly and indirectly used up in transformations to make a product. Different energy flow type into a process needs to be converted into a solar energy equivalent, termed as solar emjoules (sej). This emjoules sets the basis for all emergy calculations. Another metric that presents a good basis for sustainability analysis is the sustainable process index (SPI), which estimates the total area needed by a process to produce a unit of product. The choice of area as the basis for calculation is based on the idea that solar energy is the real long-term input with its utilization bound to the planet’s limited surface area. Thus, SPI represents the area needed by the process to provide one unit of product, while emergy helps to account for all the work done by nature and the human-economy in the production process. Due to the common denominator of solar energy and the use of several interrelated indices in the estimation of SPI and emergy, only one metric is insufficient to present a comprehensive sustainability analysis for a process. Therefore, to offer a holistic view of sustainability for a process, it is essential to integrate both SPI and emergy. In this work, a superstructure-based solvent recovery framework has been developed that considers multiple separation technologies simultaneously to recover waste solvents. We integrated mathematical models that consider the SPI, Emergy, and Economics of the recovery pathway. We then formulated a multi-objective problem that seeks to minimize all three metrics simultaneously. Our results indicate that solvent recovery presents a good alternative to conventional waste solvent disposal techniques such as incineration. Additionally, the integrated SPI-emergy analysis offers an approach to quantify the environment’s role in absorbing and processing pollution.
Polyolefin plastics are materials manufactured and used at a global scale, necessitating an effective recycling solution. Pyrolysis has significant potential as a technology for polyolefin recycling, but fundamental knowledge of the process chemistry is limited. To elucidate the chemistry of polymer decomposition and measure the intrinsic reaction kinetics of plastic pyrolysis, an experimental system is needed which is capable of operating absent transport limitations and on sufficiently short time scales. To this end, a new Pulse-Heated Analysis of Solid Reactions (PHASR) system was developed for the study of polyolefin pyrolysis. The new PHASR system operates under conditions which enable the measurement of polyolefin pyrolysis product evolution (e.g., propylene, butylene) under isothermal conditions with millisecond time-scale resolution. A Visual PHASR system was also developed for the visualization of polyolefin pyrolysis via high-speed photography, enabling the observation of reaction phenomena. As polypropylene (PP) is one of the most widely produced plastics, it is critical to understand the kinetic behavior of PP pyrolysis for the development of industrial recycling solutions as part of a circular economy. As such, it is of interest to use the PHASR method to measure the intrinsic kinetics of PP pyrolysis. This work demonstrates the application of PHASR to PP, presenting kinetic results and observed reaction phenomena.
Semi-continuous anaerobic digestion (AD) of sewage sludge with hydrothermal (HT) pretreatment have emerged as a sustainable technique for energy and nutrient recovery. Both AD and HT treatments impose significant impacts on the reclamation/recycling of phosphorous (P). Yet, the speciation evolution of P as well as involved reaction mechanisms during combined semi-continuous AD with HT pretreatment of sewage sludge still remain unclear. This study investigates the evolution and mineralization of P in sewage sludge during combined semi-continuous AD with HT pretreatment using complementary chemical extraction and X-ray spectroscopy characterizations. For raw sludge with high molar ratio of Mg/Fe (5.9), HT did not induce the formation of struvite in the hydrochars. Struvite was observed during the subsequent AD of low temperature (90 and 125 °C) HT slurries due to the reaction of Mg-phosphate phases with extensive NH4+ at pH > 7. For HT slurries produced at 155 °C, the pH was always below 7 during the subsequent AD process, preventing struvite precipitation in the AD solids. The results from this study suggest that pH plays important roles in controlling P mineralogy during AD and HT treatments of sludges. This work also provides insights into the reaction mechanisms during HT-AD treatments of sludges and can help evaluate the nutrient recycling and reclamation options for sludges.
In 2016, the DOE estimated the United States has 205 million tons of available biomass waste that include algae, forestry, agricultural, and municipal waste. These waste streams are often uncollected or underutilized. One common thermochemical processing method capable of converting a wide variety of organic residues into a value-added product is hydrothermal carbonization (HTC). HTC converts wet substrates at operating temperatures ranging between 150 – 280 °C and autogenous pressures to form a hydrochar product with applications in soil amendment, metal absorbent, and solid fuel. HTC has been broadly applied in thousands of published studies that evaluate the effectiveness of HTC using a subset of feedstocks and/or operating conditions. Similarly, the hydrochar products have been selectively characterized based on desired properties of the application. To date, connections between HTC studies have been limited to direct comparisons on results that have similar operating conditions and/or feedstocks. Therefore, we perform a meta-analysis on current HTC work in conjunction with experimental runs to assess the dependency of feedstock and process conditions on HTC performance. Our meta-analysis model evaluates over 100 datasets from HTC runs using miscanthus, cellulose, rice husk, and wheat straw. The HTC performance and corresponding hydrochar properties are considered with a confidence level on their dependency to the HTC operating temperature, reactor volume, reaction time, and reactor stirring. Hydrochar properties considered in the meta-analysis include elemental content, higher heating value, and proximate composition. Meta-analysis trends are experimentally assessed using miscanthus, food waste and brewer’s spent grain under HTC conditions between 190 – 250 °C and two differently sized reactors. Experimental HTC runs revealed synergistic effects when combining waste feedstocks. In addition, HTC runs using food waste produced different in hydrochar yields when performed in reactors of different size. This study reveals important considerations in comparing and evaluating HTC performance with other studies.
When it comes to the water-energy nexus, harnessing blue energy is vital with today’s energy-demanding processes and technologies. In this context, the reverse electrodialysis (RED) process is a thriving process that is serving as a potentially viable external energy source for many energy intensive processes such as membrane distillation (MD), electrodialysis (ED), capacitive deionization (CDI), etc. RED utilizes the Gibbs free energy of mixing two solutions of different salinities - salinity gradient energy (SGD) - and converts it into usable electrical energy. Hence, it is crucial to develop RED systems with an appropriate low concentration (LC) and high concentration (HC) solution pairs to maximize the extractable power density and at the same time make use of various disposable industrial effluent streams. Herein, this work explores using a compact RED system that converts the chemical potential energy of mixing ammonia-based industrial wastewater stream (LC) with a high effluent salinity brine stream (HC) into viable electrical energy. Simultaneously, the resultant brackish water level stream of this mixing process is properly diluted and used for fertigation to increase the sustainability of the process. As such, mixing those wastewater streams will eliminate the unadvisable disposal of high salinity brine directly back into the sea. The wastage of ammonia-rich wastewater can enhance agricultural productivity. The influence of concentrate and dilute stream concentrations, compositions and flowrates on acquired power density and energy recovery were investigated and gave maximum power density of 1.3 Wm-2 in the tested RED cell, which is comparable with power densities achieved with conventional NaCl based solutions in the same system (2.0 Wm-2). Additionally, the impact of changing the number of ion exchange membrane pairs, amount of external load added, and recyclability of wastewater streams was studied and optimized to amplify the osmotically generated power and subsequently obtain the maximum power density from it, and also to increase the extent of wastewater dilution to reach brackish water levels suitable for irrigation.
Photocatalysis by metal doped semiconductor is attracting major attention to enable the reduction of CO2(g) in the presence of water vapor as a hole scavenger. Such technology has the potential to produce chemical feedstock and simultaneously minimize environmental pollution. Potassium doped iron oxide (α-Fe2O3) of varying potassium compositions (100 Fe:x K, 0 ≤ x ≤ 5) are synthesized using incipient wetness impregnation method. The structure, composition, and properties of the catalysts are investigated by X-ray diffraction, nitrogen adsorption-desorption experiments, DSC, TGA, and multiple spectroscopies, including: DRUV-vis, FTIR, Raman, ICP-AES, XPS and UPS, TEM with EDS and SAED. UV-visible light (λ ≥ 295 nm) excited the catalysts uniformly deposited in a cylindrical photoreactor in presence of pure CO2 or air (400 ppm CO2), both under a saturated water vapor atmosphere. The maximum production of CO(g) (RCO = 0.5836 μmol gcat-1 h-1 in pure CO2 and RCO = 0.4267 μmol gcat-1 h-1 in air) quantified by GC-TCD-FID corresponds to 100Fe:1K photocatalyst. The surface doped potassium photocatalyst enhances the photocatalytic efficiency by creating a more negative conduction band than the CO2/CO reduction potential as supported by UPS and DRUV-vis spectroscopies. The photoreduction mechanism and also the effects of scavenger species will be reported.