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At least 271 records · Page 15

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DOE OSTI2021

Mitigation of Acute Ammonia Emissions With Biochar During Swine Manure Agitation Before Pump-Out: Proof-of-the-Concept

Ammonia (NH 3 ) emissions from animal agriculture can cause eutrophication of water ecosystems and are precursors to secondary particulate matter (PM 2 .5 ). NH 3 emissions from stored swine manure represent nutrient loss affecting the fertilizing value of manure. The short-term emission bursts occur when farmers agitate manure before emptying storage and fertilizing fields. There is no proven technology to mitigate gaseous emissions during agitation, while the hazards of acute releases (e.g., H 2 S) are well-known. Biochar mitigates NH 3 emissions from manure over the long-term. The objective of this research was to evaluate the mitigation of acute NH 3 emissions during/after agitation. Two biochars, highly alkaline and porous (HAP from corn stover) and red oak (RO), were tested. The 6 and 12 mm-thick layers of biochar powder were surficial applied followed by 3 min agitation. NH 3 concentrations were measured before/during/after agitation. Mitigation was assessed by comparing: (i) the maximum (peak) flux, (ii) total emission (from agitation start till NH 3 concentration returned to the before-agitation), and (iii) the total emissions during agitation. The 12 mm HAP significantly ( p < 0.05) reduced (i–iii) by 63, 70, and 85%, respectively. The 6 mm HAP significantly reduced (i–iii) by 76, 75, and 78%, respectively. The 12 mm RO significantly reduced (i–iii) by 9, 53, and 57%, respectively. The 6 mm RO significantly reduced (i–iii) by 61, 86, and 63%, respectively. The NH 3 emission kinetics model confirmed that a 6 mm dose was just as effective as the larger dose. More research is needed to optimize and scale-up mitigating emissions and retention of nutrients in manure with biochar.

Chen, Baitong↗

DOE OSTI2021

A Swollenin From Talaromyces leycettanus JCM12802 Enhances Cellulase Hydrolysis Toward Various Substrates

Swollenins exist within some fungal species and are candidate accessory proteins for the biodegradation of cellulosic substrates. Here, we describe the identification of a swollenin gene, Tlswo , in Talaromyces leycettanus JCM12802. Tlswo was successfully expressed in both Trichoderma reesei and Pichia pastoris . Assay results indicate that Tl SWO is capable of releasing reducing sugars from lichenan, barley β-glucan, carboxymethyl cellulose sodium (CMC-Na) and laminarin. The specific activity of Tl SWO toward lichenan, barley β-glucan, carboxymethyl cellulose sodium (CMC-Na) and laminarin is 9.0 ± 0.100, 8.9 ± 0.100, 2.3 ± 0.002 and 0.79 ± 0.002 U/mg, respectively. Additionally, Tl SWO had disruptive activity on Avicel and a synergistic effect with cellobiohydrolases, increasing the activity on pretreated corn stover by up to 72.2%. The functional diversity of Tl SWO broadens its applicability in experimental settings, and indicating that it may be a promising candidate for future industrial applications.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2020

Mitigation of Gaseous Emissions from Swine Manure with the Surficial Application of Biochars

Environmental impact associated with odor and gaseous emissions from animal manure is one of the challenges for communities, farmers, and regulatory agencies. Microbe-based manure additives treatments are marketed and used by farmers for mitigation of emissions. However, their performance is difficult to assess objectively. Thus, comprehensive, practical, and low-cost treatments are still in demand. We have been advancing such treatments based on physicochemical principles. The objective of this research was to test the effect of the surficial application of a thin layer (¼ inches; 6.3 mm) of biochar on the mitigation of gaseous emissions (as the percent reduction, % R) from swine manure. Two types of biochar were tested: highly alkaline and porous (HAP) biochar made from corn stover and red oak (RO), both with different pH and morphology. Three 30-day trials were conducted with a layer of HAP and RO (2.0 & 1.65 kg∙m−2, respectively) applied on manure surface, and emissions of ammonia (NH3), hydrogen sulfide (H2S), greenhouse gases (GHG), and odorous volatile organic compounds (VOCs) were measured. The manure and biochar type and properties had an impact on the mitigation effect and its duration. RO significantly reduced NH3 (19–39%) and p-cresol (66–78%). H2S was mitigated (16~23%), but not significantly for all trials. The phenolic VOCs had relatively high % R in most trials but not significantly for all trials. HAP reduced NH3 (4~21%) and H2S (2~22%), but not significantly for all trials. Significant % R for p-cresol (91~97%) and skatole (74~95%) were observed for all trials. The % R for phenol and indole ranged from (60~99%) and (29~94%) but was not significant for all trials. The impact on GHGs, isobutyric acid, and the odor was mixed with some mitigation and generation effects. However, larger-scale experiments are needed to understand how biochar properties and the dose and frequency of application can be optimized to mitigate odor and gaseous emissions from swine manure. The lessons learned can also be applicable to surficial biochar treatment of gaseous emissions from other waste and area sources.

Meiirkhanuly, Zhanibek↗

DOE OSTI2020

The Impact of Surficial Biochar Treatment on Acute H2S Emissions during Swine Manure Agitation before Pump-Out: Proof-of-the-Concept

Acute releases of hydrogen sulfide (H2S) are of serious concern in agriculture, especially when farmers agitate manure to empty storage pits before land application. Agitation can cause the release of dangerously high H2S concentrations, resulting in human and animal fatalities. To date, there is no proven technology to mitigate these short-term releases of toxic gas from manure. In our previous research, we have shown that biochar, a highly porous carbonaceous material, can float on manure and mitigate gaseous emissions over extended periods (days–weeks). In this research, we aim to test the hypothesis that biochar can mitigate H2S emissions over short periods (minutes–hours) during and shortly after manure agitation. The objective was to conduct proof-of-the-concept experiments simulating the treatment of agitated manure. Two biochars, highly alkaline and porous (HAP, pH 9.2) made from corn stover and red oak (RO, pH 7.5), were tested. Three scenarios (setups): Control (no biochar), 6 mm, and 12 mm thick layers of biochar were surficially-applied to the manure. Each setup experienced 3 min of manure agitation. Real-time concentrations of H2S were measured immediately before, during, and after agitation until the concentration returned to the initial state. The results were compared with those of the Control using the following three metrics: (1) the maximum (peak) flux, (2) total emission from the start of agitation until the concentration stabilized, and (3) the total emission during the 3 min of agitation. The Gompertz’s model for determination of the cumulative H2S emission kinetics was developed. Here, 12 mm HAP biochar treatment reduced the peak (1) by 42.5% (p = 0.125), reduced overall total emission (2) by 17.9% (p = 0.290), and significantly reduced the total emission during 3 min agitation (3) by 70.4%. Further, 6 mm HAP treatment reduced the peak (1) by 60.6%, and significantly reduced overall (2) and 3 min agitation’s (3) total emission by 64.4% and 66.6%, respectively. Moreover, 12 mm RO biochar treatment reduced the peak (1) by 23.6%, and significantly reduced overall (2) and 3 min total (3) emission by 39.3% and 62.4%, respectively. Finally, 6 mm RO treatment significantly reduced the peak (1) by 63%, overall total emission (2) by 84.7%, and total emission during 3 min agitation (3) by 67.4%. Biochar treatments have the potential to reduce the risk of inhalation exposure to H2S. Both 6 and 12 mm biochar treatments reduced the peak H2S concentrations below the General Industrial Peak Limit (OSHA PEL, 50 ppm). The 6 mm biochar treatments reduced the H2S concentrations below the General Industry Ceiling Limit (OSHA PEL, 20 ppm). Research scaling up to larger manure volumes and longer agitation is warranted.

Chen, Baitong (ORCID:0000000266071253)↗

DOE OSTI2023

Hybrid Mesoporous Carbon/Copper Ferrite Electrode for Asymmetric Supercapacitors

Asymmetric supercapacitors (ASCs) with two dissimilar electrodes are known to exhibit relatively moderate energy and power densities. If electrodes derived from earth-abundant materials or renewable resources such as lignocellulosic biomass (LCB) are used for fabrication, energy storage systems are expected to become less expensive and more sustainable. Hybrid electrode materials have advantages such as higher surface area, better chemical stability, and superior energy density. This study reports on the synthesis of a novel hybrid electrode material containing porous carbon (POC) and copper ferrite, which is designated as POC@Cu-ferrite, and its electrochemical performance in ASC configuration. Corn stover derived hydrochar is utilized for the sol–gel synthesis of POC@Cu-ferrite hybrid material using earth-abundant Cu and Fe-based precursors. This material is characterized using X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET) surface area analyzer, and scanning and transmission electron microscopy (SEM/TEM). As-synthesized Cu-ferrite is found to contain 89.2% CuFe 2 O 4 and 10.8% Fe 2 O 3 , whereas other phases such as Fe 3 O 4 , CuFeO 2 , and CuO are observed for the POC@Cu-ferrite. BET-specific surface area (SSA) and pore volume of POC@Cu-ferrite are observed as 1068 m 2 /g and 0.72 cm 3 /g, respectively. POC@Cu-ferrite hybrid electrode is used with POC opposite electrode to fabricate ASC, which is tested using Gamry G-300 potentiostat/galvanostat/ZRA to obtain cyclic voltammetry (CV) profiles and galvanostatic charge–discharge (GCD) plots. ASC is also prepared using Cu-ferrite and POC materials and its specific capacitance and stability are compared with ASCs prepared with POC@Cu-ferrite and POC or graphene nanoplatelets (GNPs) electrodes. POC@Cu-ferrite hybrid electrode is found to be superior with a 2-fold higher capacitance and significant electrochemical stability over 100 GCD cycles as compared to the Cu-ferrite electrode.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Simultaneous Electrospinning and Electrospraying for the Preparation of a Precursor Membrane Containing Hydrothermally Generated Biochar Particles to Produce the Value-Added Product of Carbon Nanofibrous Felt

Biochar is a byproduct generated from the hydrothermal liquefaction of biomass, such as corn stover, in an anaerobic environment. This work aims to convert biochar into a value-added product of carbon nanofibrous felt. First, the biochar-containing precursor membrane was prepared from simultaneous electrospinning and electrospraying. After thermal stabilization in air and carbonization in argon, the obtained precursor membrane was converted into a mechanically flexible and robust carbon nanofibrous felt. Electrochemical results revealed that the biochar-derived carbon nanofibrous felt might be a good candidate as a supercapacitor electrode with a good rate capability and high kinetic performance.

25 ENERGY STORAGE↗

DOE OSTI2020

Anatomical Fraction segmentation in the biomass bales

The U.S. Department of Energy Bioenergy Technologies Office (BETO) is committed to the development of sustainable, nationwide, commercial biofuel production to displace petroleum-derived fuels, increase domestic energy production, and encourage the creation of a domestic bioenergy and bioproducts industry. Operating a commercial-scale bioenergy operation requires significant technological advancements for determining biomass feedstock quality during the preprocessing stage. Usage of non-food feedstocks- e.g., corn-stover, pine residue, and forest residue - at the biorefineries reduces strain on the food supply chain. But the non-food feedstock heterogeneity- physical size, shape, and chemical composition-poses a significant challenge during milling, conveyance, feeding, and biofuel conversion processes. 3D X-Ray imaging (CT) is capable of distinguishing material features by detecting density and compositional differences. But the inherent complexity introduced during harvesting and bailing makes the reconstruction and interpretation of baled biomass materials from x-ray data time consuming, laborious, and expensive. Feedstocks are low-density materials that produce small contrast differences in the x-ray images. This paper focuses on using the shape and texture properties, using 3D image processing techniques like 3D skeletonization, directional statistics to characterize and extract volumetric content of the different tissue samples in the biomass bales.

09 BIOMASS FUELS↗

DOE OSTI2021

BETO 2021 Peer Review - Biological Upgrading of Sugars (BUS) 2.3.2.105

The Biological Upgrading of Sugars (BUS) project directly targets the anaerobic conversion of lignocellulosic feedstocks into intermediate molecules readily upgradeable to fuel precursors. Recent efforts on the BUS project have a particular emphasis on the biological production of butyric acid, an intermediate that can be readily upgraded to sustainable aviation fuel, diesel blend-stocks, and high value chemicals. The BUS project approaches this direction through a combination of strain engineering, fermentation process engineering, development of novel separations technologies, and the design and build of pilot scale systems. Our ultimate project goal is to develop an integrated cost-effective process at pilot scale to achieve DOE's MYPP targets of $2.50/GGE. The major thrust of the BUS project over the last project cycle was on the development of integrated processes surrounding the anaerobic production of carboxylic acids using diverse Clostridium species. We developed and expanded genetic tools for several Clostridium species and rewired microbial metabolism in an attempt to maximize substrate utilization and flux towards butyric acid. We designed and built novel bioreactors with an in situ product recovery system enabling the biological production and recovery of highly purified acids. We leveraged this system to generate 100s of grams of acid from corn stover hydrolysate. In this presentation we highlight data surrounding our proposed process and accompanying results from technoeconomic and life-cycle analyses of our integrated process. Finally, we detail plans of our pilot scale reactor system that is in process and discuss our future routes towards achieving economically viable and sustainable diesel and jet blendstocks.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2021

Alkaline Oxidation of Enzymatic Hydrolysis Lignin Using Reversibly Soluble Bases

Production of aromatic aldehydes, such as vanillin, from lignin, has been an intriguing process for decades, but widespread implementation has been inhibited by the high hydroxide:lignin ratios required for significant aldehyde yields. In this work, we explore oxidation of lignin-rich residues isolated from corn stover after deacetylation, mechanical refining, and enzymatic hydrolysis (DMR lignin), using reversibly-soluble bases in place of NaOH. In particular, strontium and barium hydroxides have low solubility at room temperature, but become soluble to more than 2 M at temperatures above 100 °C, thus producing highly alkaline conditions at reaction temperature but facilitating a simple recovery and recycle of the alkali upon cooling. Aromatic monomer yields are comparable for both types of bases at 20-30 wt%, depending on the lignin substrate. Overall, these results suggest a strategy to substantially reduce the cost and life cycle impact of lignin depolymerization by alkaline oxidation.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2022

Understanding Biomass and Polymer Feedstock Variability Through Analytical Pyrolysis and Two Dimensional Gas Chromatography and Mass Spectrometry

Moving toward a circular carbon economy requires enabling reuse of carbon-based macromolecules like those in biomass and polymers. Meeting this goal requires increased upcycling of waste products into higher value products. For biomass waste such as corn stover, pine needles, or bark, one approach is using pyrolysis to convert these feedstocks into bio-oil that can be used for liquid fuel or transformed into other hydrocarbon based products, like bio-polymers. Waste plastics can be upcycled or recycled into new products, or alternatively converted into bio-oil by pyrolysis. Macromolecules from biomass and polymers are challenging to convert into liquid fuel or chemical feedstocks, due to large and sometimes heterogeneous networks of polymeric bonds. We work with the Idaho National Laboratory’s Biomass Feedstock National User Facility and Department of Energy’s Feedstock Conversion Interface Consortium to develop a molecular understanding of biomass variability that occurs naturally and as a result of storage or preprocessing techniques applied to feedstocks, to understand chemical reactions occurring during pyrolysis and other biomass or polymer conversion techniques. Using two dimensional gas chromatography mass spectrometry coupled to analytical pyrolysis provides insight into the molecular changes that occur during the pyrolysis event, and these insights can extend to bench or pilot scale pyrolysis conversions. Understanding pyrolysis of biomass and polymers at a molecular level contributes to development of new tools to predict and manipulate the optimum conditions and identify the best storage, preprocessing, and conversion techniques to maximize output of specific high-value chemical species in the conversion to fuels, or to characterize feedstocks for blending before pyrolysis. Identification and understanding of the molecular level changes resulting from novel preprocessing techniques that can be used to control and manipulate the chemical output of bench or pilot scale pyrolysis is another focus of investigation, including the use of gamma irradiation, acid, or enzyme pre-treatments. We also focus on the impacts of storage conditions and techniques, which can affect moisture levels, degradation, and impacts from naturally occurring microbes in the environment.

09 BIOMASS FUELS↗

DOE OSTI2022

Evaluating the Feasibility of Higher Titers and Yields for 2,3-Butanediol Production to Achieve the Biofuel Industry Economic Goal of Under $3.50 GGE

To achieve the economic goal of producing biofuels that can compete with petroleum-based products, we increased titers of 2,3-butanediol (BDO) production. BDO has many advantages over ethanol; including lower toxicity, higher heat of capacity, and is a precursor to various valuable applications. To produce BDO for fuel upgrading, we have genetically modified Zymomonas mobilis (YC-1). Several materials and feed strategies were evaluated to determine the best titer and economic feasibility. Titers from DMR corn stover in a batch process were in the range of 70-80 g/L. The fully hydrolyzed material was easy to work with but suffered from dilution issues. We pushed the concentration of solids to above 25% w/w and were met with numerous challenges. This included an initial sugar concentration above 150 g/L, the high solid concentration altered the oxygen mass transfer rate and affected which products were produced, and the fermentation conditions were not optimal for the enzyme. Despite these challenges, our current results yielded 100 g/L of upgradeable products (70 g/L BDO and 30 g/L acetoin) and 83% fermentation process yield. However, the poor enzymatic hydrolysis yield of 64%, unconverted xylose, and the high acetoin levels warrant further exploration for optimization. Using unhydrolyzed solids as the feed material, we achieved titers in the range of 75-95 g/L BDO. The raw solids feed, though operationally more challenging to work with, proved to be promising as the rate of hydrolysis promoted co-utilization of the sugars. We reached 150 g/L BDO using concentrated DDR liquors under boules and continuous feeding strategies. The clarified liquors showed high titers, high productivity, high yield, and high sugar utilization with little drawback operationally. The target goal of under $3.50 GGE was achieved in several feeding strategies. Scale-up feasibility has also been demonstrated at the 100L scale using both whole slurry and liquor hydrolysates.

BIOMASS FUELS↗

DOE OSTI2022

Engineered microbes for conversion of organic compounds to medium chain length alcohols and methods of use

This disclosure provides a genetically-modified bacterium from the genus Pseudomonas that comprises an exogenous nucleic acid encoding an enoyl-CoA reductase and an exogenous nucleic acid encoding an acyl-CoA reductase that produces medium chain length alcohols. The disclosure further provides methods for producing medium chain alcohols using such genetically-modified bacterium. This disclosure provides a renewable, bio-based production platform for valuable mcl-alcohols that have a wide range of industrial applications. Current production of mcl-alcohols typically occurs through the hydrogenation of plant oils and waxes. This process leads to issues of deforestation and is largely unsustainable. Utilizing waste lignin streams as the carbon source provides a more sustainable feedstock that can be generated from plant waste like corn stover. Along with this, the use of lignin avoids competition with food resources as traditional starch and sugar feedstocks.

Guss, Adam M.↗

DOE OSTI2022

Alkaline Oxidation of Lignin Using Reversibly-Soluble Bases

Production of oxidized aromatic monomers from lignin has been an intriguing process for decades, but widespread implementation has been inhibited by the high hydroxide:lignin ratios required for significant aldehyde yields. The high hydroxide loading in most scenarios renders the process uneconomical even for high-value products such as vanillin. In this work, we explore alkaline oxidation of a lignin-rich enzymatic hydrolysis residue isolated from corn stover, using alkaline earth metal hydroxides, such as Sr(OH)2 and Ba(OH)2 as base promoters. These materials are soluble at reaction temperature, but mostly insoluble at room temperature, allowing recovery and reuse by simple filtration. We show that monomer yields and profiles using these bases is similar to that obtained using NaOH as base, and that Sr(OH)2 can be recovered in yields above 90%. Preliminary TEA and LCA suggest that replacing NaOH with Sr(OH)2 can decrease monomer production costs by 40% and decrease global warming potential in lignin depolymerization by 30%, enabling a more economical and sustainable process.

BIOMASS FUELS↗

DOE OSTI2022

Alkaline Oxidation of Lignin Using Reversibly-Soluble Bases

alkaline oxidation↗

DOE OSTI2023

Economic and Sustainability Assessment on Bio-Based 2,3-BDO Separation Approaches for Sustainable Aviation Fuel Production

Sustainable aviation fuel (SAF) plays a critical role in aviation decarbonization. SAF can be derived from lignocellulosic biomass, such as corn stover, via 2,3-butanediol (BDO) intermediate. BDO undergoes downstream upgrading, including dehydration, oligomerization, and hydrotreating, to make the hydrocarbon blend stock like SAF. Separating BDO from a fermentation broth is challenging. Water is more volatile than BDO, so energy consumption for ordinary distillation is prohibitively high. For BDO to be a feasible intermediate for sustainable biofuels such as SAF, the total energy usage for the BDO separation target was set to be no greater than 30% of its lower heating value (LHV). We have developed and explored less energy intensive separation technologies for processing dilute fermentation BDO broth into suitable feed for downstream upgrading. The combined economic and sustainability assessment was performed to assess the feasibility of select cost-effective process designs and comparisons with baseline technology (i.e., cascade vacuum distillation).

BIOMASS FUELS↗

DOE OSTI2024

Biomass Attributes and Attribute Modifications Affecting Systems and Methods to Separate and Fractionate. In: Handbook of Biorefinery Research and Technology

Chemical and physical heterogeneity in biomass feedstocks such as agricultural or forestry residues is due to substantial differences in plant tissue types. These differences can contribute significant challenges to handling, preprocessing, and conversion in biorefining processes. An understanding of this chemical and physical heterogeneity can be used to inform fractionation technologies that could facilitate more streamlined processing and potentially be employed to yield multiple co-product streams for a single feedstock. In this chapter, the motivation and scope of biomass fractionation is first outlined. Physical and chemical properties of biomass feedstocks, along with their distribution and diversity within plants is next discussed with respect to how these differences can be exploited in a fractionation process. A summary of some of the key physical principles that allow for fractionation is next covered along with how these physical principles are exploited in equipment designs. Examples from the literature are briefly discussed that highlight how these approaches can be employed to achieve processing objectives. Several case studies on physical fractionation of corn stover and forestry residues are presented that illustrate how integrated fractionation processes could be employed. Finally, prospects and potential economic drivers for adoption of biomass fractionation technologies are discussed.

Biomass chemical properties↗

DOE OSTI2024

Use of Lignin-Based Admixture as Water Reducer (WRA) for Tailoring the Rheological Properties of Mortars for 3D-Printing

Efforts towards decarbonizing construction materials and industrial processes related to cement and concrete can be aided via multifaceted approaches that target alternative admixtures as well as precision control of fabrication. Chemical admixtures for water reduction have played a crucial role in the development of advanced mortar and concrete mixtures. Newer biomass processing techniques developed for aviation fuel production from corn stover biomass produce a highly reactive lignin byproduct that is suitable for chemical modifications to mimic the properties of commonly used polycarboxylate ethers (PCEs) with a smaller carbon footprint. These lignin-based plasticizers developed at NREL can be used in place of petrochemical-derived superplasticizers to tailor the rheological properties of cement-based systems for applications such as additive manufacturing while reducing the carbon intensity of the concrete mix. Lignosulfonates derived from paper pulping were historically used as water reducers only to be displaced with the rise of PCEs. The present study examines the use of a NREL produced lignin-based water reducing admixture (WRA), in cement pastes and mortar mixtures for 3D-printing at small- (mm) scale. The experimental program consisted of different formulations of oxidized lignin-based WRAs added in variable dosages to cement pastes with a fixed water-to-cement ratio. The objective is to achieve an appropriate workability, extrudability and buildability of mortar mixtures to produce 3D-printed specimens. The rheological characterization was performed to compare the initial yield stress and viscosity of the different mixtures with lignin-based admixture with respect to conventional PCE superplasticizers. The rheological characterization shows that the proposed material act as an effective water-reducer in cement systems, affecting the yield stress, plastic viscosity, and structuration rate of the mixtures evaluated. On the other hand, the effect on early hydration process of the cement pastes containing lignin-based admixtures is comparable to conventional superplasticizers.

3D-printing↗

DOE OSTI2020

Irrigation, carbon amelioration, nitrogen, and stover removal effects on continuous corn

Corn (Zea mays L.) residue or stover is harvested as supplemental feed for livestock and is a potential feedstock for cellulosic biofuels. Limited information is available on corn stover removal effects on grain yield under different irrigation rates, nitrogen (N) fertilizer rates, and practices to maintain soil carbon (C) and minimize soil erosion. Here, we evaluated potential interactions between irrigation rate (full or limited), C amelioration practices (cover crop, surface-applied manure, or no amelioration practice), fertilizer N management (125 or 200 kg N ha –1 ), and stover removal (residue removal or no residue removal), on no-till continuous corn grain yield located on a silt loam soil in south-central Nebraska (2011–2018). Stover removal increased (P = .0017) grain yield by 1.02 Mg ha –1 and grain N uptake compared with no stover removal. Manure increased corn grain yield by 899 kg ha –1 compared to either the control or cover crop with stover removal while C amelioration practices did not affect grain yield under stover retention. Grain N concentration was higher (P < .0001) with stover removal (13.2 g kg –1 ) than residue retained (12.7 g kg –1 ). Partial factor productivity (grain yield/N rate) was highest for manure treatments with residue removal. The farmgate N balance (N applied – N removed) from stover removal was negative, yet grain yield was not affected after eight growing seasons. Grain yield increased with stover removal and manure application resulting in a cost-effective C amelioration practice whereas incorporating a winter cover crop resulted in similar grain yield as the control.

54 ENVIRONMENTAL SCIENCES↗