Doctor of Philosophy / Department of Biological & Agricultural Engineering / Donghai Wang / In 2008 AGCO began a project to develop machinery to harvest biomass for a DOE project called “Integration of Advanced Logistical Systems and Focused Bioenergy Harvesting Technologies to supply Crop Residues and A Herbaceous Energy Crops in a Diversified Large Square Bale Format”. The project considered the harvest of corn stover, wheat straw, switchgrass and energy sorghum. AGCO modified some existing pieces of production hay harvesting equipment and developed a new larger square baler for single pass crop residue harvesting. Field scale tests of the developed equipment occurred in the years 2010, 2011, and 2012. Data collected during these tests included crop harvested, field location, number of hectares harvested, moisture content of harvested biomass, number of bales produced, weight of each bale, time to harvest, model(s) and sizes of machine(s) used, and fuel consumed. Data was collected for different harvesting techniques for crop residues: two-pass vs single-pass harvesting for corn stover and wheat straw. Data was collected for harvesting switchgrass and energy sorghum for comparison purposes. The cropping years were very different over the course of the project due rain fall amounts. The data was analyzed using American Society of Agricultural and Biological Engineer machinery management standards and accepted Agriculture & Applied Economics Association assumptions. Excel spreadsheets were developed to calculate the harvesting costs on a dry Mg basis for each crop that was harvested. Results from the data analysis was used to modify the Integrated Biomass Supply Analysis and Logistics model to predict harvesting costs for crop residues at different yield levels, harvest conditions, and machine settings for single-pass harvesting. A number of conclusions can be drawn from this analysis. First, “take rates” for crop residues can have a significant effect on harvest costs. Low “take rates” can make it economically unfeasible to harvest crop residues in some instances. Second, single-pass harvesting of crop residues is less labor and fuel intensive than multi-pass harvesting. Third, the large yields potential of energy sorghum, which requires more operations to harvest than switchgrass, more economically to harvest than switchgrass. Fourth, operational techniques can be used to offset some crop variability to reduce harvest cost of crop residues. Lastly, a decision tool has been developed to aid producers in the decision of whether to harvest corn stover or not based on cost return estimates.

<p>Kukuruzovina je žetveni ostatak i potencijalni supstrat za proizvodnju biogasa. Direktivom 2018/2001 definisan je tzv. RED metod za obračunavanje ušteda emisija gasova s efektom staklene bašte&ndash; GHG. Metod je primenjiv za silažu kukuruza i stajnjak kao supstrat za proizvodnju biogasa, ali se na neadekvatan način obračunavaju emisije GHG za kukuruzovinu. Cilj je bio da se predlože unapređenja RED metoda kojima bi se prevazišli identifikovani problemi, kao i da se ispita uticaj primene unapređenog metoda na ocenu ušteda emisija GHG energetskog iskorišćenja biogasa iz kukuruzovine, tj. na ocenu održivosti. Uštede emisija GHG za sve razmatrane slučajeve primene RED metoda u osnovnoj i unapređenoj formi, imale su vrednost nižu od postavljenog kriterijuma od 70 %, tj. nisu održivi. Predloženo je da se RED metod unapredi ukidanjem pravila da se ne obračunavaju emisije GHG pre ubiranja žetvenih ostataka i da je potrebno da se navede da je ostatak fermentacije ko-produkt proizvodnje i korišćenja biogasa, kao i da je primena alokacije emisija GHG na biogas i ostatak fermentacije obavezna u slučaju primene ostatka fermentacije na polja sa kojih nisu ubirani žetveni ostaci.</p> / <p>Corn stover is a crop residue and potential substrate for biogas production. Directive<br />2018/2001 defines so-called RED method for determination of greenhouse gas (GHG)<br />emission savings. In the case of energy utilization of biogas produced from corn stover,<br />savings are calculated in an inadequate manner. The objective was to suggest the<br />improvements of the RED method in order to overcome the identified problems, as well<br />as to investigate the impact of the application of the improved method on the evaluation<br />of GHG emission savings, i.e. the the sustainability evaluation. The results of the GHG<br />emission savings, using the basic and the improved forms of RED method, show that all<br />considered cases had a value lower than the set criterion of 70%, i.e. they are not<br />sustainable. It was suggested to improve the RED method by abolishing the rule that<br />GHG emissions prior to collection of crop residue are not accounted. Also, it should be<br />noted that the digestate is a co-product of biogas production as well that the application<br />of the GHG emissions allocation to biogas and the digestate is mandatory in the case<br />when digestate is used on fields other than those used for substrate provision.</p>

Rising world petroleum prices and global warming are contributing to interest in renewable energy sources, including energy produced from agricultural crops and waste sources of biomass. A network of small mobile pyrolysis units may be the most cost effective system to convert biomass from agricultural feedstocks to bio-crude oil. Mobile pyrolysis units could be moved to the feedstock production fields thereby greatly simplifying feedstock logistics. In the North Central (NC) region of the U.S., possible feedstocks are corn stover, energy sorghum, and switchgrass. A grid-based Geographic Information System (GIS) program was developed to identify optimum locations for mobile pyrolysis units based on feedstock availability in the NC region. Model builder was used to automate the GIS analysis. Network analysis was used to find the best route to move the mobile pyrolysis units to new locations and to identify the closest refinery to transport the bio-crude oil. To produce bioenergy from feedstocks, the removal of biomass from agricultural fields will impact the hydrology and sediment transport in rural watersheds. Therefore, the hydrologic effects of removing corn stover from corn production fields in Illinois (IL) were evaluated using the Soil Water Assessment Tool (SWAT). The SWAT model was calibrated and validated for streamflow and sediment yields in the Spoon River basin in IL using observed data from the USGS. The modeling results indicated that as residue removal rates increased, evapotranspiration (ET) and sediment yields increased, while streamflows decreased. Biochar is a carbon-based byproduct of pyrolysis. To ensure that the mobile pyrolysis system is economically and environmental sustainable, the biochar must be land applied to the feedstock production fields as a soil amendment. An assessment of hydrologic changes due to the land application of biochar was made using the SWAT model in the Spoon River basin and changes in soil properties due to incorporation of biochar into the soil obtained from laboratory experiments by Cook et al. (2012). Model simulations indicated that a biochar application rate of 128 Mg/ha decreased water yield, and sediment yield in surface runoff and increased soil moisture and ET.

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Cellulosic biomass-to-bioenergy systems can provide environmental and economic benefits to modern societies, reducing the dependence on fossil-fuels and greenhouse gas emissions while simultaneously improving rural economies. Corn (Zea mays L.) stover and wheat straw (Triticum aestivum L.) residues have particular promise given these crops are widely grown and their cellulosic fractions present a captured resource as a co-product of grain production. Annual systems also offer the ability to change crops rapidly in response to changing market demands. However, concerns exist about residue removal effects on soil health, greenhouse gases emissions and subsequent crop productivity. The carbon footprint and the crop yield productivity and soil health responses resulting from the removal of crop residues has been studied extensively over the last 20 years, but this research has been largely conducted in the Corn Belt. To investigate the impact of crop residue removal in the Mid-Atlantic USA, combinations of corn stover (0, 3.33, 6.66, 10 and 20 Mg ha-1) and wheat straw (0, 1.0, 2.0, and 3.0 Mgha-1) were soil applied in a corn-wheat/soybean (Glycine max L. Merr.) rotation in Virginia's Coastal Plain. Corn stover (0, 3.33, 6.66, 10 and 20 Mg ha-1) was applied in a continuous corn cropping system in the Ridge/Valley province. For each system, residues were applied following grain harvest over two production cycles. Each experiment was conducted as a randomized complete design with four replications. The highest rates of stover retention resulted in greater greenhouse gas emissions in year 1, but not year 2 of these studies and did not affect overall global warming potentials. Stover application also increased soil carbon but had little effect on other measures of soil quality. Stover K levels were greater with high rates of stover retention. Overall, these studies indicate little effect of residue removal or retention (above typical residue production rates) on subsequent crop production, greenhouse gas emissions, or soil health measures in the short term. This study is one of the first to assess residue removal in the Mid-Atlantic USA and is the first study to investigate the impacts that managing more than one crop residue in a multi-crop system. Longer-term research of this type may be warranted both to determine the consequences of residue management and to start building a regionally-specific body of knowledge about these practices. / Ph. D. / Over the last decade, strategic economic and environmental concerns have increased interest in the use of crop residues as sustainable, renewable sources for bioenergy and bio-products. Most of the work investigating the sustainability of residue removal has occurred in the US Corn Belt, where corn stover and wheat straw (the part of the plant that is not grain) supplies are abundant. Although the research data from the Corn Belt provide guarded optimism about residue harvest systems in the Midwest, it is not suitable to extrapolate these results to the South because of differences in soils, climate, and cropping systems. Cooler, humid conditions can sustain higher levels of soil organic matter, lessening but not eliminating concerns about stover removal. Current research from the Midwest region suggests routine stover harvest – within limits – can be sustainable. The development of new bioenergy and bioproduct industries in the Southeast region is leading to a growing expectation that regional cropping systems will supply the millions of tons of biomass needed for these new businesses. However, few data are available regarding sustainable crop residue harvest from the Southeast. Sustainable levels of residue removal may be quite low given regional soil and climatic conditions, and the effects of residue removal on soil health parameters and greenhouse gas emissions remain to be defined. The purpose of this project was to determine the amount of corn stover and wheat straw can sustainably be harvested from Virginia’s grain-based cropping systems without reducing plant productivity or soil quality or increasing GHG emissions. This research generated regionally relevant information on the impacts of crop residue removal to help determine whether harvesting wheat straw and corn stover can be a sustainable practice for the region’s cropping systems. In a first stage, short term impacts of residue removal on soil quality and greenhouse gases were measured in Blacksburg and New Kent, VA, over the period 2015-2017.

Gasification is a process used to convert any carbonaceous species through heterogeneous reaction to obtain the desired gaseous products of H2 and CO which are used to make chemicals, liquid transportation fuels, and power. Both pyrolysis and heterogeneous gasification occur in commercial entrained-flow gasifiers at pressures from 4 to 65 atm with local gas temperatures as high as 2000 °C. Many gasification studies have been performed at moderate temperatures, heating rates, and pressures. In this work, both pyrolysis and char gasification experiments were performed on coal, petroleum coke, and biomass at conditions pertinent to commercial entrained-flow gasifiers. Rapid biomass pyrolysis experiments were performed at atmospheric pressure in an entrained-flow reactor for sawdust, switchgrass, corn stover, and straw mostly using a peak gas temperature of 1163 K at particle residence times ranging from 34 to 113 ms. Biomass pyrolysis was modeled using the Chemical Percolation Devolatilization model assuming that biomass pyrolysis occurs as a weighted average of its individual components (cellulose, hemicellulose, and lignin). Thermal cracking of biomass tar into light gas was included using a first-order model with kinetic parameters regressed in the current study. Char gasification rates were measured for biomass, petroleum coke, and coal in a pressurized entrained-flow reactor at high heating-rate conditions at total pressures between 10 and 15 atm. Peak centerline gas temperatures were between 1611 and 1879 K. The range of particle residence times used in the gasification experiments was 42 to 275 ms. The CO2 gasification rates of biomass and petroleum coke chars were measured at conditions where the reaction environment consisted of approximately 40 and 90 mol% CO2. Steam gasification rates of coal char were measured at conditions where the maximum H2O concentration was 8.6 mol%. Measured data was used to regress apparent kinetic parameters for a first-order model that describes char conversion. The measured char gasification rates were far from the film-diffusion limit, and are pertinent for pulverized particles where no internal particle temperature gradients are important. The modeling and measured data of char gasification rates in this research will aid in the design and efficient operation of commercial entrained-flow gasifiers, as well as provide validation for both existing and future models at a wide range of temperatures and pressures at high heating-rate conditions.

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