Modeling Denitrification : Can We Report What We Don't Know?

Funding Information: This study is the products of a workshop funded by the Deutsche Forschungsgemeinschaft through the research unit DFG‐FOR 2337: Denitrification in Agricultural Soils: Integrated Control and Modelling at Various Scales (DASIM), and by the German Federal Ministry of Education and Research (BMBF) under the “Make our Planet Great Again—German Research Initiative”, Grant 306060, implemented by the German Academic Exchange Service (DAAD). This work was supported by the European Union's Horizon 2020 research and innovation programme project VERIFY (grant agreement no. 776810). We would like to thank the contribution of all workshop participants of the II. DASIM Modeler Workshop. Publisher Copyright: © 2023. The Authors.Peer reviewedPublisher PD

Effect of Stocking Rate on Soil-Atmosphere CH4 Flux during Spring Freeze-Thaw Cycles in a Northern Desert Steppe, China

BACKGROUND: Methane (CH(4)) uptake by steppe soils is affected by a range of specific factors and is a complex process. Increased stocking rate promotes steppe degradation, with unclear consequences for gas exchanges. To assess the effects of grazing management on CH(4) uptake in desert steppes, we investigated soil-atmosphere CH(4) exchange during the winter-spring transition period. METHODOLOGY/MAIN FINDING: The experiment was conducted at twelve grazing plots denoting four treatments defined along a grazing gradient with three replications: non-grazing (0 sheep/ha, NG), light grazing (0.75 sheep/ha, LG), moderate grazing (1.50 sheep/ha, MG) and heavy grazing (2.25 sheep/ha, HG). Using an automatic cavity ring-down spectrophotometer, we measured CH(4) fluxes from March 1 to April 29 in 2010 and March 2 to April 27 in 2011. According to the status of soil freeze-thaw cycles (positive and negative soil temperatures occurred in alternation), the experiment was divided into periods I and II. Results indicate that mean CH(4) uptake in period I (7.51 µg CH(4)-C m(-2) h(-1)) was significantly lower than uptake in period II (83.07 µg CH(4)-C m(-2) h(-1)). Averaged over 2 years, CH(4) fluxes during the freeze-thaw period were -84.76 µg CH(4)-C m(-2) h(-1) (NG), -88.76 µg CH(4)-C m(-2) h(-1) (LG), -64.77 µg CH(4)-C m(-2) h(-1) (MG) and -28.80 µg CH(4)-C m(-2) h(-1) (HG). CONCLUSIONS/SIGNIFICANCE: CH(4) uptake activity is affected by freeze-thaw cycles and stocking rates. CH(4) uptake is correlated with the moisture content and temperature of soil. MG and HG decreases CH(4) uptake while LG exerts a considerable positive impact on CH(4) uptake during spring freeze-thaw cycles in the northern desert steppe in China

Micrometeorological methods for greenhouse gas measurement

Micrometeorological techniques are useful if greenhouse gas (GHG) emissions from larger areas (i.e. entire fields) should be integrated. The theory and the various techniques such as flux-gradient, aerodynamic, and Bowen ratio as well as Eddy correlationmethods are described and discussed. Alternativemethods also used areEddy correlation, mass balance techniques, and tracer-based methods.The analytical techniques with current state-of-the-art approaches as well as the calculation procedures are presented

Greenhouse gases from agriculture

The rapidly changing global climate due to increased emission of anthropogenic greenhouse gases (GHGs) is leading to an increased occurrence of extreme weather events such as droughts, floods, and heatwaves. The three major GHGs are carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The major natural sources of CO2 include ocean-atmosphere exchange, respiration of animals, soils (microbial respiration) and plants, and volcanic eruption; while the anthropogenic sources include burning of fossil fuel (coal, natural gas, and oil), deforestation, and the cultivation of land that increases the decomposition of soil organic matter and crop and animal residues. Natural sources of CH4 emission include wetlands, termite activities, and oceans. Paddy fields used for rice production, livestock production systems (enteric emission from ruminants), landfills, and the production and use of fossil fuels are the main anthropogenic sources of CH4. Nitrous oxide, in addition to being a major GHG, is also an ozone-depleting gas. N2O is emitted by natural processes from oceans and terrestrial ecosystems. Anthropogenic N2O emissions occur mostly through agricultural and other land-use activities and are associated with the intensification of agricultural and other human activities such as increased use of synthetic fertiliser (119.4 million tonnes of N worldwide in 2019), inefficient use of irrigation water, deposition of animal excreta (urine and dung) from grazing animals, excessive and inefficient application of farm effluents and animal manure to croplands and pastures, and management practices that enhance soil organic N mineralisation and C decomposition. Agriculture could act as a source and a sink of GHGs. Besides direct sources, GHGs also come from various indirect sources, including upstream and downstream emissions in agricultural systems and ammonia (NH3) deposition from fertiliser and animal manure

Optimising high-throughput, automated preform production with non-linear simulation of the pick and place process for technical fabrics

The serial manufacturing of high performance composites parts is based on the lay-up of textile cuttings with subsequent resin impregnation. For industrial applications the cuttings are produced on automated cutter systems [1, 2, 3, 4, 8]. The existing difficulty for a complete automated process is the "pick and place"- process of these cuttings [1, 2, 3, 4, 8]. The process step is a main challenge for high throughput and quality. The textiles have a low stiffness, high sensitivity against mechanical loads and great range of the mechanical properties depending on the fabric structure [5]. The production of high performance parts is dominated by non-crimp fabrics with single- or multi-layer structure. Currently the handling of textile cuttings is done manually. These leads to challenges in the handling process if the cuttings become larger or the handling times have to be reduced for a more effective production [1, 2]. Automated "pick & place" will avoid structural defec ts and speed up the production [1, 2]. Currently handling of textile blanks is dominated by grabbing of the entire cutting surface [2, 3, 8]. More flexibility of such gripping devices can be achieved by multiple picking points with relatively small contact areas instead of the entire fabric area. Apart from the challenge of choosing a feasible gripping principle, the number and the positioning of gripping units have to be known for a successful handling. Because of the different shapes and variation of mechanical properties a practical evaluation will need time and resources. This can be reduced by a virtual model for the handling process. The approach of this work is focussed on non-crimp fabrics. Existing simulation approaches of the handling process are based on the complex modelling of textiles substructure [6, 7]. The proposed solution is based on FEA -approach with existing elements by modelling the integral textile structure. The non-linear FE-model requires a relatively small number of mate

Alternative approach for the simulation of handling processes for large textile cuttings used for high volume composite production

High performance composites become an important material for lightweight design and sustainable applications with the main driver automotive, aircraft and wind energy. As a result of the increasing number of units and the demand for consistent quality in connection with falling costs, the industrialization of the composite manufacturing is absolutely necessary. In respect to the complexity of the production steps, serial production of high performance structural composites is still a challenge. The market is dominated by the requirements of aircraft and automotive production because of the high numbers. In contrast rotor blade manufacturing has its unique challenges of high mass throughput. A 65m blade with 20 tons is produced within 48hours. A main challenge in the manufacturing of these three different applications is the handling and lay-up of textile blanks in a mold. The textile blanks, mainly basing on non-crimp fabrics, show high sensitivity against mechanical lo ads. Though manual handling of large cuttings or high numbers of cuttings in short cycle times will provoke failures in the lay-up. Lay-up failures in a composite structure will reduce mechanical properties significant. In recent years there have been developed many different solutions for mechanization or automation of this process. These solutions are aimed primarily at high quality through careful handling technologies, but less with the goal of high productivity. Fraunhofer IWES has investigated the process of textile handling especially for typical wind turbine rotor blades and is developing processes to new industrialized production concepts. The aim is reducing blade manufacturing costs and reaching higher level of quality at once. Fraunhofer IWES develops methods to achieve cost-effective and high volume production

Digital process chain for offline programming and simulation of automated composite part and mold production

Start-up of an automated system for composite part production largely determines the cost effects and time to production, especially for large parts made on versatile systems and small lots/single item production. All these factors are combined in molds for large composite parts and in novel processes like fiber placement and automated surface activation of the actual parts. To improve the set-up and reduce machine time when manufacturing large scale multi-material composite parts, Fraunhofer IWES has set up a generalized integrated digital tool chain. The part geometry and multi-material information generated in CAD is directly employed for mold design as well as programming part manufacturing processes. By building up a machine model, Fraunhofer IWES is able to simulate processes from mold milling to part production offline, avoiding collisions and reachability issues and enabling process planners to optimize the setup in advance of any physical works on the shop floor, thereby greatly reducing start-up times and increasing confidence in the resulting programming. Fraunhofer IWES has evaluated this toolchain for an advanced direct tooling approach, further reducing time to market and accelerating implementation of blade design changes. This work included manufacturing a full scale wind turbine rotor blade mold in the Blade Maker Demo Center with its multi-functional carbon fiber gantry robot

On an integrated process and machinery concept for economic industrialized production of higher quality wind turbine rotor blades

Fraunhofer IWES has investigated the production process of typical wind turbine rotor blades and developed a cost model to compare the current manual production process to new industrialized production concepts. The aim is identifying key methods to reduce blade cost: Development of cost-effective rotor blade materials with similar properties, reduction of manual labor and increase of production reproducibility for robust quality, as quality costs pose a significant part of blade costs. Fraunhofer IWES will show methods to achieve cost-effective production and present industrialized fabric handling and finishing processes as they are key factors for blade quality. Different production strategies developed by using draping simulation and a simplified finite element analysis for the complete lay-up process result in an industrialized fabric placement process to address these quality and manufacturability aspects of large blades. In many production processes the final shap e of the rotor blade is created by manual labor to reproducibly achieve the desired aerodynamics and surface quality. Fraunhofer IWES is developing a fast automated process for measuring, CNC-trimming and -grinding the blade to a shape with better aerodynamic and guaranteed structural performance by increased reproducibility. Fraunhofer IWES is currently building up a demo center for processes development and validation on the full scale blade level. Therefore Fraunhofer IWES has defined the specifications for an innovative easy-to-use CNC tool machine designed for industrialized rotor blade manufacturing, including an integrated CAD-CAM-solution

Integrated evaluation of greenhouse gas emissions (CO₂, CH₄, N₂O) from two farming systems in Southern Germany.

Agricultural practices contribute to emissions of the greenhouse gases CO2, CH4 and N2O. The aim of this study was to determine and discuss the aggregate greenhouse gas emission (CO2, CH4 and N2O) from two different farming systems in southern Germany. Farm A consisted of 30.4 ha fields (mean fertilization rate 188 kg N per ha), 1.8 ha meadows, 12.4 ha set-aside land and 28.6 adult beef steers (year-round indoor stock keeping). Farm B followed the principles of organic farming (neither synthetic fertilizers nor pesticides were used) and it consisted of 31.3 ha fields, 7 ha meadows, 18.2 ha pasture, 5.5 ha set-aside land and a herd of 35.6 adult cattle (grazing period 6 months). The integrated assessment of greenhouse gas emissions included those from fields, pasture, cattle, cattle waste management, fertilizer production and consumption of fossil fuels. Soil N2O emissions were estimated from 25 year-round measurements on differently managed fields. Expressed per hectare farm area, the aggregate emission of greenhouse gases was 4.2 and 3.0 Mg CO2 equivalents for farms A and B, respectively. Nitrous oxide emissions (mainly from soils) contributed the major part (about 60%) of total greenhouse gas emissions in both farming systems. Methane emissions (mainly from cattle and cattle waste management) were approximately 25% and CO2 emissions were lowest (circa 15%). Mean emissions related to crop production (emissions from fields, fertilizer production, and the consumption of fossil fuels for field management and drying of crops) was 4.4 and 3.2 Mg CO2 equivalents per hectare field area for farms A and B, respectively. On average, 2.53% of total N input by synthetic N fertilizers, organic fertilizers and crop residues were emitted as N2O-N. Total annual emissions per cattle unit (live weight of 500 kg) from enteric fermentation and storage of cattle waste were about 25% higher for farm A (1.6 Mg CO2 equivalents) than farm B (1.3 Mg CO2 equivalents). Taken together, these results indicated that conversion from conventional to organic farming led to reduced emissions per hectare, but yield-related emissions were not reduced