Browsing by Subject "biomass"
Now showing 1 - 14 of 14
- Results Per Page
- Sort Options
Item Biomass yield and soil microbial response to management of perennial intermediate wheatgrass (Thinopyrum intermedium) as grain crop and carbon sink(2019-12) Bergquist, GalenIWG intermediate wheatgrass (Thinopyrum intermedium (Host) Barkworth & D.R. Dewey; IWG) is a perennial grain crop with an extensive root system that could prevent erosion and nutrient leaching, build soil fertility, and potentially sequester atmospheric carbon. Two field experiments were established in southeastern Minnesota, USA to 1) address management strategies for preventing IWG grain yield decline, 2) quantify plant biomass production of IWG relative to other conventional field crops, 3) determine how this perennial grass may alter soil microbial activity and composition to the benefit of soil organic carbon (SOC) accumulation, and 4) investigate the potential for carbon sequestration. Inter-row cultivation using rotary-zone tillage (RZT) as well as herbicide, burning, and mowing at different times were employed for two years, but none effectively prevented grain yield decline. However, the application of herbicide in spring and fall cultivation had positive impacts on grain, straw, and forage yield (relative to other management treatments). IWG can produce significantly more root biomass than annual grain crops, and even more than alfalfa (Medicago sativa). These large root systems, left undisturbed, were likely responsible for an increase in soil fungal biomarkers and overall microbial biomass after three years of growth. Soil respiration rates and microbial biomass-carbon were greater under IWG in the spring and fall seasons when soybean and wheat had either not emerged yet or were already senesced, providing evidence that perennial grasses may alter soil nutrient cycling by expanding and prolonging soil microbial activity. Particularly, changes in nutrient cycling that increase labile carbon pool sizes and promote SOC formation may, in addition to storage in root biomass, support carbon sequestration in agricultural soils.Item Characterization of Emissions from Small Scale Biomass Gasifier(2013-11) Hamilton, JaimieGasification of biomass has the potential to address many issues related to both the world's energy future and greenhouse gas emissions. Gasification can be carried out in a variety of ways depending on the end-use application of the synthesis gas (syngas) or producer gas. Gasification can also use a variety of feedstocks. Gasifying agricultural waste to generate electricity or provide heating and cooling solutions has the potential to utilize waste products while providing necessary energy. Unfortunately, there are environmental and human health concerns related to the conversion of biomass to energy and the combustion of the bio-derived fuel, as well as efficiency concerns related to the technology. In this study, The Power Pallet, a commercially available integrated gasification reactor, engine and generator was used to quantify the contaminants in the unfiltered producer gas, the filtered producer gas, and the engine exhaust and determine the engine's ability to reduce contaminants through filtration and combustion. The system was also tested to determine the effect of generator loading on operating conditions, emissions, and overall efficiency. The study used a fixed-bed downdraft modified Imbert reactor with a Kubota spark-ignited natural gas engine with a Mecc Alte 10kW generator. Organic solvent, gaseous and particulate matter emissions were characterized at three locations in the gasification system to determine the packed bed filter and engine's ability to reduce concentrations of contaminants. Contaminants, such as benzene, toluene, ethylbenzene, and xylenes (BTEX) and PM, in the gasifier system were cleaned up through the packed bed filter and through combustion in the engine. PM concentrations were approximately 70 mg/Nm3 in the pre-filtered producer gas but concentrations were reduced 98-99% through the packed bed filter. PM concentrations did not change significantly during the combustion in the engine yet specific concentrations of PM were below federally mandated emissions limits for Tier 4 diesel engines. Combustible compound were 99% consumed in the engine and specific concentrations of carbon monoxide were below federally mandated levels from the engine's exhaust. Concentrations of BTEX compounds were reduced to a small degree in the packed bed filter and significantly reduced in the engine. Although concentrations of benzene in engine exhaust were greater than 10 ppm, operating the gasification system in a well-ventilated environment would ensure that the ambient air concentrations of BTEX compounds are below federal limits and protect human health and the environment from the hazards. The efficiency of the reactor increased significantly with increasing electrical load because the reactor operates at constant temperature and the higher flow rates of biomass meant that the heat loss was a smaller portion of the work from the engine. The overall system efficiency increased with increasing electrical load and the efficiency of the engine was fairly steady over the small range of generator loads tested.Item Corn Stover Utilization and Soil Health(2008) Mishra, NishiItem Decomposition of the finest root branching orders: Linking belowground dynamics to fine-root function and structure(2011) Goebel, Marc; Hobbie, Sarah E; Bulaj, Bartosz; Zadworny, Marcin; Archibald, Douglas D; Oleksyn, Jacek; Reich, Peter B; Eissenstat, David MRoot turnover is fastest in the finest roots of the root system (first root order). Additionally, tissue chemistry varies among even the finest root orders and between white roots and older, pigmented roots. Yet the effects of pigmentation and order on root decomposition have rarely been examined. We separated the first four root orders (all <1 mm) of four temperate tree species into three classes: white first- and second-order roots; pigmented first- and second-order roots; and pigmented third- and fourth-order roots. Roots were enclosed in litterbags and buried under their own and under a common species canopy in a 34-year-old common garden in Poland. When comparing decomposition of different root orders over 36 months, pigmented third- and fourth-order roots with a higher C:N ratio decomposed more rapidly, losing 20–40% of their mass, than pigmented first- and second-order roots, which lost no more than 20%. When comparing decomposition of roots of different levels of pigmentation within the same root order over 14 months, pigmented (older) first- and second-order roots lost ∼10% of their mass, while white (younger) first- and second-order roots lost ∼30%. In contrast to root mass loss, root N content declined more rapidly in the first- and second-order roots than in third- and fourth-order roots. In higher-order roots, N increased in the first 10 months from ∼110% to nearly 150% of initial N content, depending on species; by the end of the study N content had returned to initial levels. These findings suggest that, in plant communities where root mortality is primarily of pigmented first- and second-order roots, microbial decomposition may be slower than estimates derived from bulk fine-root litterbag experiments, which typically contain at least four root orders. Thus, a more mechanistic understanding of root decomposition and its contribution to ecosystem carbon and nutrient dynamics requires a fundamental shift in experimental methods that stratifies root samples for decomposition along more functionally based criteria such as root order and pigmentation, which parallel the markedly different longevities of these different root classes.Item Degradable Materials from Sugar-Derived Feedstocks(2019-01) Lillie, LeonSugar-derived molecules have excellent potential to serve as building blocks in the development of sustainable polymers with high performance and rich functionality. This thesis focuses on the utilization of carbohydrate-derived molecules (bicyclic sugar derivatives and sugar metabolites) to enhance the degradability of polymeric materials. The first area of research presented describes the synthesis of a novel GDL-based α,ω-diene (glucarodilactone 10-undecenoate, GDLU). This molecule and its congener (isosorbide undecenoate, IU), were found to be highly suitable monomers for acyclic diene metathesis polymerization and were used to produce a family of homopolymers and copolymers of various GDLU:IU ratios. The structure/property implications of these similar sugar-derived diols on the materials physical performance and hydrolytic stability were explored. The second area of research expanded the usage of GDLU to a new class of materials, poly(ester-thioethers), with the use of photo-initiated thiol-ene polymerization. The impact of dithiol chemistry on material thermal and mechanical properties were investigated. Finally, the third area of research details the synthesis of novel methacrylic anhydride-like monomers obtained from the two-step synthetic modification of itaconic acid. These monomers were polymerized via thiol-ene polymerizations to obtain degradable, polyanhydride-based thermoset materials, with rapid neutral water degradation.Item Distribution, Composition and Biomass of the Crustacean Zooplankton Population in Western Lake Superior(Water Resources Research Center, University of Minnesota, 1973-08) Conway, J.B.; Odlaug, T.O.; Olson, T.A.; Ruschmeyer, O.R.Although data were collected for two years, 1970 and 1971, the major portion of this research was carried out the second year. This research took place in western Lake Superior and most of the data were collected at two stations, Larsmont and Stony Point, which were twenty miles northeast of Duluth. Each of these stations included two sites, one a half mile and the second two miles from shore. The other area where samples were collected was at the Little Marais and Sugar Loaf Cove stations, some 70 miles north of Duluth. The major purposes of this research were to study the productivity and the vertical, seasonal and horizontal distribution of the crustacean zooplankton population in western Lake Superior. A limited study of the biology of the copepod, Limnocalanus macrurus, was also conducted. Productivity at the Larsmont and Stonv Point area averaged 323 crustaceans per 100 liters of water, and 60 grams per square meter (based on a fifty meter water column). Productivity at the Little Marais and Sugar Loaf Cove area averaged 95 crustaceans per 100 liters and 37 grams per square meter. In general, productivity decreased as the depth increased from zero to 50 meters. If a thermocline was present, then both the toted number of crustaceans and the biomass became relatively scarce below twenty meters. Cladocerans were most frequent1y found in the upper ten meters of the water column whereas copepods were present at every level. Adult copepods were usually heavier than adult cladocerans and it was not unusual to find the mean weight of an organism at 50 meters ten or more times that of one at five meters. Productivity at the Larsmont and Stony Point area was bimodal during the sampling season; the first peak occurred in July and contained primarily copepods and the second, which was the seasonal maximum, occurred in September and contained both copepocls and cladocerans. Surface water temperatures were also bimodal during the sampling season; the peak recorded in July was thirteen degrces centigrade and sixteen degrees was reached in September. The cladoceran, Bosmina, became abundant after the water temperature reached five degrees in July, Another cladoceran, Dapnia, Replaced Bosmina in September when the water temperature was about eleven degrees. Ephippia, the overwintering stage of Daphnia first appeared in late August. Three copepods, Diaptomus, Limnocalanus, and Cyclops were present during most of the sampling season. Limnocalanus was present at all depths from June to early August, but was most numerous at ten meters. When the water temperature warmed above twelve degrees, the population shifted downward and was usually below the thermocline during the davlight hours. At this time, they were most abundant at 40 meters, The copepod, Epischura, was numerous in the upper lavers after the water warmed above eleven degrees. Productivity differences were found between the various sites and stations. These differences point to the lack of homogeneity in the horizontal distribution of the crustacean zooplankton population and support the phenomenon of “zooplankton patchiness". Productivity levels at the Little Marais and Sugar Loaf Cove area were from one-third to two- thirds of those at Larsmont and Stony Point. The Larsmont station was slightly more productive than Stony Point. The Stony Point inshore site was slightly more productive than the offshore site. The period of maximum productivity occurred at the Larsmont inshore site amd at both Stony Point sites in September. Maximum productivity was recorded at the Larsmont offshore site in July. A phytoplankton bloom was observed at the Stony Point station on July 20, 1971, but was not seen on the same day at the Larsmont station. Limnocalanus macrurus contrihuted to the greatest percentage of the crustacean biomass (often more than 90 percent) at depths 30, 40 and 50 meters in western Lake Superior. The male to female ratio established was 1:2. The mean lengths of mature males and females were, 2.09 and 2.16 millimeters, respectively. The length-weight correlation was: Dry weight (mg/100) = 3.31 length (mm) - 2.95. Two cladocerans, new to Lake Superior, were identified. They were: Alona guttata Sars and Holopedium gibberum Zaddach.Item Energizing the Landscape: An analysis of switchgrass production costs, commodity crop economics, and nascent gasification technologies in the United States.(2014-08) Nickerson, ThomasThe United States has set ambitious goals for bioenergy that, if met, would require the widespread production of additional sources of biomass on the landscape. In this dissertation, I explore three important economic aspects of the development of the bioenergy industry, namely switchgrass production costs, competition between switchgrass crops and existing commodity crops, and the use of biomass in emerging energy technologies. First, I derive near-term production costs, returns, and profitability of switchgrass (Panicum virgatum), a perennial bioenergy crop, across a region spanning 14 states. Costs vary across the region, ranging from less than $300 ha-1 to more than $1,400 ha-1, yet switchgrass for bioenergy may be profitable in certain locations with commoditized switchgrass prices at or above $50 Mg-1. Second, I describe the financial profile of the two most prevalent commodity crops grown in the United States, corn and soybeans. I find both crops experience an increase in production costs across the entire study period, but these increases are outpaced by commodity prices, ultimately leading to higher operating profit margins. Furthermore, approximately half of all major corn and soybean producing counties have experienced, in at least one year from 2005 to 2011, a policy inefficiency in which crop insurance overcompensates for the loss of crops, which hinders the introduction of dedicated bioenergy crops on the landscape. Third, I assess the viability of solar-heated gasification systems and find that given current energy market conditions, financial incentives such as tax credits, bond yield reductions, or price subsidies would be necessary to generate a positive return over the life of facilities. In total, bioenergy in the United States will face substantial hurdles and will need to overcome industrial inertia in the agriculture and energy sectors. However, with the correct tools and incentives, it may be possible for bioenergy from switchgrass to become an increasingly important piece of the United States energy profile.Item Fine-root biomass from Cloquet and Auclair IDENT sites(2022-03-14) Schuster, Michael J.; Williams, Laura J; Stefanski, Artur; Bermudez, Raimundo; Messier, Christian; Belluau, Michaël; Paquette, Alain; Gravel, Dominique; Reich, Peter B; schuster@umn.edu; Schuster, Michael JMean fine-root biomass data gathered from the IDENT experiments in Cloquet, MN and Auclair, Quebec.Item Land Use Constraints on Wetland Biomass Development: A Case Study in Aitkin County Minnesota.(Midwest Universities Energy Consortium, Chicago., 1981) Craig, William J.Item Methods and Mechanisms of Pyrolysis: Modeling Polymer Decomposition for a Circular Economy(2022-01) Wang, ZiweiFast pyrolysis offers one of the most accessible ways to convert macromolecular feedstocks, such as biomass or plastic waste, into small molecules that can subsequently be used to produce liquid fuels and chemicals. The complexity of the feedstock and the dynamic changes in condensed phase chemical environments make it challenging to elucidate elementary kinetics and reaction mechanisms and control the selectivity to products. These effects also manifest in macroscopic phenomena such as measurable differences in kinetics and product distribution with changes in reaction temperature, feedstock composition, and even pellet size of the feedstock. These complexities are ultimately dictated by molecular transformations and controlled by the molecular structure and local chemical environments. Understanding the molecular processes in pyrolysis is crucial for the development of large-scale and economical biomass conversion or plastic upcycling facilities. This dissertation presents the development and applications of an ab initio-based kinetic Monte Carlo and Molecular Dynamics (KMC+MD) simulation approach that can model the kinetics of the fast pyrolysis and thermal reaction networks for biomass and polyolefin plastic feedstocks. This approach tracks detailed atomic structural information, including 3D coordinates of atoms and connectivity of chemical bonds in the feedstock molecules. It uses a stochastic simulation algorithm (SSA) to track and carry out the elementary reaction steps and uses classical MD simulations to follow the dynamics of the feedstock and the reaction environment as reactions proceed. The elementary step kinetics for the KMC simulations were established from detailed first-principle density functional theory (DFT) calculations. The detailed atomic-structural information is retained throughout the simulation, thus allowing the simulations to follow molecular transformations and the local environment during the reaction. As such, the simulations capture the unique kinetic manifestations that would otherwise be lost in composition-based deterministic models. This KMC+MD simulation approach is first used to model the pyrolysis reaction pathways of cellulose, including the paths to form levoglucosan as well as light oxygenates. The simulation results are able to reproduce temporal experimental product distributions and, in addition, gain molecular-level insights into the unique catalytic features that control the kinetics. The generality of the KMC simulation framework allows it to readily be adapted and used to simulate the kinetics and product distributions of polyolefin pyrolysis, including polyethylene and polypropylene feedstocks. The simulated polyolefin pyrolysis results are extensively compared with experimental data reported in the literature and those obtained by experimental collaborators in Prof. Paul Dauenhauer’s group. More generally, the simulation framework presented in this dissertation provides a powerful tool to study the thermal degradation of different polymeric feedstocks in pyrolysis systems that challenges the capability of deterministic models. The simulation approach offers molecular-level mechanistic insights and has direct applications in reactor modeling and techno-economic analyses of large-scale pyrolysis facilities.Item Production of Energy and Chemicals by Thermochemical Conversion from Recycled and Renewable Biomass(2016-08) Zhu, ChengRecovery energy from municipal solid waste and biomass are one of the leading methods to achieve maximum energy efficiency and environmental sustainability. My research mainly includes two projects, novel biomass-supported sorbent for coal combustion emission control and fundamental study of biomass fast pyrolysis in the presence of alkaline earth metals. The first research project was collaborated with Accordant Energy LLC. on the development of ReEngineered Feedstock (ReEF), consisting of sorbent containing post-recycled paper and plastics. ReEF was evaluated in a laboratory-scale fluidized bed combustor system. The results indicate that co-firing ReEF with coal provides SO2 reduction in flue gas up to 85% as well as higher carbon conversion than pure coal combustion. Sulfation kinetics of ReEF combustion were evaluated in a drop-tube reactor. Sulfation of calcium hydroxide in ReEF was delayed due to RDF combustion when compared with pure calcium hydroxide sorbent. The second project investigated the catalytic effect of alkaline earth metals on cellulose pyrolysis primary (transport-free) and secondary (diffusion-limited) reaction pathways. Catalytic materials included homogeneous metal ions from their inorganic salts, and their corresponding heterogeneous metal oxides. While oxides were shown to have limited impact on cellulose pyrolysis chemistry, metal ions were found to significantly alter the secondary reaction pathways of cellulose under diffusion-limited conditions. The initial breakdown kinetics of cellulose were examined using a millisecond, thin-film reactor called PHASR (Pulse-Heated Analysis of Solid Reactions). Using the cellulose surrogate, α-cyclodextrin, the energetics of cyclodextrin decomposition were characterized. An interesting finding is that cellulose undergoes two distinct kinetic regimes with a distinct transition at 467 °C, which is interpreted as a reactive melting point.Item Productivity, Carbon Sequestration, Nutrient Accumulation, And Species Interactions In Perennial Biomass Alley Cropping Systems(2016-02) Gamble, JoshuaPerennial biomass production in agroforestry systems has been promoted as a strategy to increase productivity and ecosystem services from marginal agricultural lands. However, little is known about appropriate species combinations and production potential for biomass crops in agroforestry systems. Our objectives were to evaluate the potential for biomass feedstock production, nutrient uptake and accumulation, and carbon sequestration in alley cropping agroforestry systems at two Minnesota sites, and to determine how tree – crop interactions influenced productivity in these systems. Short-rotation woody crops (SRWC) were hybrid poplar (Populus maximowiczii x P. nigra ‘NM6’) and shrub willow (Salix purpurea ‘Fish Creek’). Herbaceous alley crops were switchgrass (Panicum virgatum L.), prairie cordgrass (Spartina pectinata Bosc ex Link), ‘Rush’ intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth and Dewey cv. Rush), and an eleven species native polyculture. After four years of growth, we found that NM6 poplar alley cropping systems maximized biomass yields at Empire (13.5 Mg ha-1 yr-1) and Granada, MN (9.6 Mg ha-1 yr-1), irrespective of herbaceous crop type. NM6 poplar – intermediate wheatgrass systems showed the greatest potential for aboveground N, P, and K uptake (477, 62, and 301 kg ha-1), while NM6 poplar – prairie cordgrass systems had among the highest root biomass, and root C, N, P, and K due to extensive coarse roots. Soil carbon declined slightly over the study period, although alley system roots sequestered up to 7.0 and 6.3 Mg C ha-1 at Empire, and Granada, respectively. At Empire, above– and belowground biomass of herbaceous alley crops declined substantially with proximity to SRWC rows, as did soil water potential, soil NO3 – N, and transmittance of photosynthetically active radiation (PAR). A mixed effects model with predictors for PAR and soil water potential best explained patterns in prairie cordgrass and native polyculture yield, suggesting that competition for light and water limited crop growth at this site. Our results show that after four years of production, NM6 poplar and prairie cordgrass were among the best SRWC and herbaceous crop choices for biomass production, C sequestration, and nutrient accumulation in alley cropping systems. However, competition may limit the stand longevity of herbaceous crops, which could reduce the utility of these systems for biomass production and ecosystem services over time.Item Understanding the role of local condensed phase environments in pyrolytic and catalytic biomass conversion(2021-05) Maliekkal, VineetBiomass conversion generally involves two major sets of chemical transformations – (1) thermal breakdown of macromolecules in the feedstock, such as cellulose, to smaller sugars and oxygenates via fast pyrolysis followed by (2) catalytic upgrading to the desired fuels or precursor chemicals. These reactions of biomass conversion usually occur in the condensed phase – either in the melt phase for pyrolytic reactions or in the solvent phase for catalytic upgrading reactions. The work in this thesis sheds light on the molecular complexity of such condensed phase environments. Explicit molecular modeling of these condensed phase environments coupled with first-principles simulation techniques such as density functional theory (DFT) and ab initio molecular dynamics (AIMD) are used to elucidate the influence of such environments on the kinetics of biomass conversion reactions. Examples from cellulose pyrolysis and hydrogenation chemistry are studied to demonstrate the critical importance of considering the role of condensed phase environments in biomass conversion.Using DFT calculations, constrained AIMD and experimental kinetics from the Pulsed Heated Analysis of Solid Reactions (PHASR) set-up, it is shown that vicinal hydroxyl groups which are present in the cellulose matrix in abundance can directly participate in the activation of cellulose by promoting facile proton transfer as well as stabilizing transition states through hydrogen bonding. The kinetic influence of calcium ions, naturally present in such feedstocks, is also examined in this thesis. It is shown that calcium interacts with cellulosic melt environment such that the native hydrogen bonding is disrupted. Such disruption of the hydrogen bonding network coupled with Lewis acid stabilization of the transition states leads to dual catalytic cycles for cellulose activation and second order rate dependence on calcium. Explicit modeling of the cellulosic environment is critical towards capturing such kinetic behavior. Furthermore, the influence of hydroxyl groups, calcium ions and more generally the cellulosic condensed phase environment, is examined more broadly and extended to other ring opening and fragmentation pathways that lead to glycolaldehyde, a side product of pyrolysis. The work from this part of the thesis helps establish the ubiquitous involvement of the local condensed phase environment in mediating biomass pyrolysis reactions. Finally, aqueous phase hydrogenation of C=C bonds in phenol over Pt particles inside zeolites is studied as a model reaction to demonstrate the importance of solvent environment in catalytic upgrading. Through explicit modeling of local water clusters around the reaction centers, it is shown that increasing the acidity of the zeolite supports can alter the local acidity of the water clusters. This in turn is shown to not just open up proton coupled electron transfer (PCET) pathways but also improve the efficacy of such mechanisms for hydrogenation. Thus, this study helps demonstrate that one can alter the solvent environment to enhance reactions of biomass conversion, especially those that involve proton transfer. More generally, the collective body of work in this thesis could act as a framework for future studies that seek to understand the role of condensed phase environments in biomass conversion as well as to develop strategies that use such environments for improved reactivity and selective chemical transformations.