Agricultural chemistry and bioenergy

Renewed interest in converting biomass to biofuels such as ethanol, other forms of bioenergy, and bioenergy byproducts or coproducts of commercial value opens opportunities for chemists, including agricultural chemists and related disciplines. Applications include feedstock characterization and quantification of structural changes resulting from genetic modification and of the intermediates formed during enzymatic and chemical processing; development of improved processes for utilizing chemical coproducts such as lactic acid and glycerol; development of alternative biofuels such as methanol, butanol, and hydrogen; and ways to reduce greenhouse gas emission and/or use carbon dioxide beneficially. Chemists will also be heavily involved in detailing the phytochemical composition of alternative energy crops and genetically improved crops. A resurgence of demand for agricultural chemistry and related disciplines argues for increasing output through targeted programs and on-the-job training.     

Potential of Near- and Mid-infrared Spectroscopy in Biofuel Production

For many decades, near-infrared spectroscopy (NIRS) has been used to determine the composition of animal feedstuffs and grains. More recently, mid-infrared spectroscopy (mid-IR) has also been examined for similar determinations. These spectroscopic methods offer the potential for rapid and accurate determination of organic constituents, such as fiber components and protein, of forages, by-products, and grains at reduced cost and greatly increased speed (minutes instead of hours or days). Because they are nonchemical in nature, they result in a large reduction (90% or more) in the chemical wastes associated with standard chemical-based assay methods. The same components of interest for biofuel production (cellulose, hemicellulose, lignin, starch, protein, oil, etc.) are those that have already been determined by NIRS/mid-IR for evaluating grains and animal feedstuffs. Therefore, these techniques would appear to be a natural match for evaluating feedstocks for biofuels, and the literature shows that efforts in this direction are being successfully tested and instituted. For this discussion, an overview of where such efforts are and the potential for NIRS/mid-IR in producing biofuels will be covered. For example, while there are similarities between the needs of the biofuels industry and the analysis of animal feedstuffs, there are also both practical and technical differences between the two that will likely impact how NIRS/mid-IR is developed for biofuels. As an example, grain analysis for protein is performed on a large scale by government agencies such as the Canadian Grain Commission and U.S. Grain Inspection Service, while at least in the United States, animal feedstuff analysis is performed by state or independent laboratories for individual farmers. For biofuels, this might well result in most analysis being performed by the large corporations converting the feedstocks to biofuels, as opposed to the individual producer having analysis performed at an independent laboratory. Similarly for animal feedstuffs, measurements of fiber (neutral detergent fiber or NDF, acid detergent fiber or ADF, and lignin) and protein are carried out. These fiber measurements often consist of more than one type of fiber component with some being computed by difference (hemicellulose = NDF – ADF) and are empirical at best. Whether such empirical estimates will be sufficient for assessing biofuels or whether new spectroscopic methods for directly measuring the components of interest (cellulose, etc.) will need to be developed is a question to be answered when components other than starch for ethanol or oil for biodiesel become common.     

Evaluation of lignin and lignin‐nitrogen fractionation following alternative detergent fiber pre‐treatment methods

Abstract

Decomposition of plant material, compost, or mulch may be monitored or predicted by measuring certain key parameters in live or senescent material. Lignin is one of the key parameters to measure as it provides an indication of soil quality. This study evaluates the most promising detergent clean‐up procedures for pre‐treating plant material to provide a more rapid method for lignin determination. Performance was tested with a variety of plant material, typical of vegetation analyzed in decomposition, nutrient cycling and natural ecosystem studies. Lignin‐nitrogen (N) and fiber‐N residues were also determined to assess the efficiency of the clean‐up processes. Good agreement was obtained for lignin on a range of plant material between the time‐consuming classical Klasson method and either modified neutral detergent fiber (NDF) excluding sodium sulphite and Dekalin, or the acidified detergent fiber (ADF) pre‐treatments. We recommend either of the detergent pre‐treatment procedure as they provide rapid and effective preliminary steps for precise lignin determination. Residual lignin‐N following NDF and ADF detergent pre‐treatment methods were on average respectively 31% and 24% of the plant nitrogen.     

Laboratory Wet Milling of Corn: Milling Fraction Correlations and Variations Among Crop Years

Several coproducts result from fractionating corn in the wet‐milling process. Because small changes in product composition and milling characteristics can have a major impact on coproduct yields and values, testing is done to anticipate final product yields. Using small sample size and controlled conditions, a laboratory wet‐milling method proved to be a useful tool for wet milling and genetics industries. A wet‐milling process (100‐g batches) was used for data collection. Data collected during 11 years (1994–2004) were observed for samples used as benchmarks to verify process precision and accuracy and determine correlations among wet‐milling yields. More than 400 milling tests were performed on benchmark samples. Data from benchmark samples also were pooled. Coefficients of variation were low (<6%) for mean yields; year‐to‐year standard deviations of benchmark sample yield means were homogenous and implied precision of the procedure. Some differences were detected in mean yields among years (P ≤ 0.05) for benchmark data due to combined effects of hybrid and environment. A negative correlation (r = –0.58) was observed between starch and gluten yield for pooled benchmark data. Four years (2002–2005) of milling data from commercially available hybrids were analyzed using the milling procedure. For pooled commercial data, the correlation between starch and fiber yield was (r = –0.80); correlation between starch and gluten was (r = –0.76).     

Phosphorus Concentrations and Flow in Maize Wet‐Milling Streams

Marketing of coproducts such as corn gluten meal (CGM) and corn gluten feed (CGF) is important to the maize wet‐milling industry. High phosphorus concentrations could lead to limited markets for CGF due to its potential to increase phosphorus in animal wastes. The objective was to measure the concentration and flow of phosphorus in the wet‐milling process and identify streams that could be altered. Samples were taken from 21 process streams of three facilities and the phosphorus content of each was determined. Flow of phosphorus was simulated using a computer model for a 2,700 tonne/day (105,000 bu/day) wet‐milling plant. Phosphorus concentrations of streams varied from <10 mg/kg to >14,000 mg/kg. Phosphorus content of many streams differed significantly among facilities. Flow of phosphorus (kg/day) varied dramatically among streams. However light steepwater, light gluten, and process water streams (5,960, 3,080, and 970 kg/day, respectively) accounted for much of the phosphorus flow. Modification of these streams could reduce phosphorus content of coproducts. The high phosphorus content of either CGF or CGM could be reduced markedly if phosphorus was reduced in the appropriate streams.     

土壤生态系统服务的概念、量化及其对城市化的响应

土壤生态系统是陆地生态系统的重要组成部分,是人类赖以生存的重要资源。全球的快速城市化进程使土壤生态系统服务发生了部分不可逆转的变化。本文归纳了土壤生态系统服务定义和分类的发展过程,介绍了土壤生态系统服务定量化表征方法以及GUMBO、In VEST等几种常用的评价模型,并从供给服务、调节服务、文化服务和支持服务几个方面阐述土壤生态系统服务对城市化的响应。针对土壤生态系统服务分类、建模、空间表达以及其对人为活动的响应等方面研究存在的不足,本文提出未来的研究重点方向:建立土壤生态系统服务分类体系与标准,构建基于生态过程的土壤生态系统服务量化模型,开展土壤生态系统服务制图与权衡研究,加强土壤生态系统服务对城市化的动态响应机制与过程研究。期望更多的人关注和参与土壤生态系统服务研究,并将其应用于土壤资源管理、生态文明建设等政府决策。     

Effect of plant age on in-soil decomposition and nitrogen content of sunn hemp tissue

ABSTRACT

The effects of plant age at the time of mowing on sunn hemp (Crotalaria juncea L.) tissue decomposition, nitrogen (N) release, and fiber content in Krome very gravelly loam were assessed. Combined leaf and stem tissue from 42-, 77- or 112-day-old sunn hemp plants was placed in mesh bags and buried below the soil surface in the field. Bags were removed bi-weekly and dry weights, N concentration, acid detergent fiber (ADF) and neutral detergent fiber (NDF) concentrations in buried sunn hemp tissues were determined. There was a rapid decrease plant tissue dry weight during the first 14 days after tissue was buried, followed by a slow gradual decrease. The amount N per hectare was much lower for 42-day-old than 112-day-old sunn hemp. Tissue of the youngest plants decomposed the quickest. Forty two-day-old tissue had a higher N concentration, N mineralization rate, and lower NDF and ADF than 77- or 112-day-old tissue. Mowing and soil incorporation of a 42-day-old instead of a 77- to 112-day-old sunn hemp cover crop prior to planting a cash crop can be beneficial for a fast-growing cash crop planted soon after soil incorporation of the cover crop.     

国外生物液体燃料发展和示范工程综述及其启示

概述了国内外利用农林废弃木质纤维素、能源作物和生活垃圾等生物质制备生物液体燃料的发展现状和工程进展动态,着重讨论了美国、巴西、欧洲、加拿大等国促进生物液体燃料发展的政策和法规,介绍了各国在纤维素乙醇、油脂加氢、气化-费托合成液态烃等生物液体燃料制备技术的大型运行及在建工程装置,分析了中国该领域的基础,分析了生物液体燃料发展中存在的主要障碍,如原料成本高及供给不确定,高生产成本及政策不确定性。提出继续研发高效的生物液体燃料技术路线、加大中试和示范工厂建设和投入、开展生物液体燃料生产企业与航空公司及与传统能源化工公司的合作等促进其未来发展的建议与方向。同时应立足国情,加强国家层面的生物液体燃料使用目标,完善政策保障,建立反映各类能源环境成本的能源价格和税收制度,为生物液体燃料能源产业发展建立公平的竞争环境。     

土壤微生物影响土壤健康的作用机制研究进展

土壤健康是农业可持续发展的中心主题。土壤微生物参与土壤生态功能、环境功能和免疫功能协同驱动土壤生命系统运转，是维持土壤健康的核心与关键。了解不同微生物介导的土壤健康调控机制对有效利用这些核心微生物维持和改善土壤健康至关重要。本文围绕微生物参与调节土壤碳循环、养分循环，改变土壤结构、抑制植物病虫害、污染控制等主要生物过程系统梳理了微生物在调控土壤健康中的重要作用，以及微生物作为土壤健康的敏感指标对土壤健康的指示与预警作用。强调未来应加强驱动土壤健康特定功能以及多个生物过程的核心微生物组信息数据库挖掘、构建与生产应用研究，为定向利用微生物改善农业土壤生态系统功能、维持土壤健康以及保障土壤可持续发展提供科学依据。     

Impact of fertilizer source on the dynamics of carbon and nutrients in a podzol designated for land-use conversion

Boreal lands have long been considered unsuitable for agriculture. Climate change projections support a shift towards increased agricultural production in boreal ecosystems via land use conversion. Depending on the conversion protocol, the new plough layer may variably reflect the properties of different soil depths. This study assessed how adding mineral or organic fertilizer sources to distinct soil layers within ploughing depth (0–15 cm [topsoil] or 15–30 cm [subsoil]) affects nutrient uptake and crop productivity. Locally relevant organic waste fertilizers (dairy manure [DMN], recirculating aquaculture system supernatant [SUP] and slurry [RAS]), were compared against mineral fertilizer. Tall fescue was used to verify agronomic responses. Starting available nutrient concentrations were balanced as necessary with mineral N and P fertilizers. Except for NH₄-nitrogen, both soils were of apparent similar fertility (total C < 1%); unfertilized, neither could support significant plant growth. Subsoil-based growth was fast but limited in time reflecting immediately available nutrients. Topsoil led to delayed, extended growth. This might be due to dichotomous priming effects: during the duration of the experiment up to 36% of subsoil carbon was lost, while the topsoil gained up to 49% carbon, most apparent for DMN. While RAS led to the greatest N and P acquisition efficiencies for topsoil, it had no such effect for subsoil, suggesting distinct fixation and mineralization processes. Dissimilar C cycling and nutrient acquisition for the two soil depths indicates that site-specific considerations that include soil health parameters with commonly tested available nutrients are needed where podzols are farmed after land-use conversion.     

Compost Maturity Effects on Nitrogen and Carbon Mineralization and Plant Growth

Improved predictive relationships between compost maturity and nitrogen (N) availability are needed. A total of 13 compost samples were collected from a single windrow over a 91 d period. Compost stability and maturity were assessed using both standard chemical analyses (total C and N, mineral N, total volatile solids) and other methods (CO₂ evolution, commercial maturity kits, and neutral detergent fiber, and lignin). Compost N and carbon (C) were evaluated during a 130 d aerobic incubation in a sandy loam soil after each compost was applied at 200 mg total kg^?1 soil. The effect of compost maturity on plant growth was evaluated by growing two ryegrass (Lolium perenne L.) crops and one barley (Hordeum vulgare L.) crop in succession in compost-amended soil under greenhouse conditions. Potential phytotoxicity from compost was assessed by growing tomato (Lypersicum esculentum L.) seedlings in compost-amended soil. Regression and correlation analyses were used to evaluate the relationship between compost maturity parameters, the rate and extent of net N and C mineralization, plant yield and N uptake, and phytotoxicity. Commonly used maturity parameters like total C, total N, and C:N ratio were poorly correlated with the rate and extent of mineralization, and with plant growth parameters. The N mineralization rate during the first 48 d of aerobic incubation was strongly correlated (r= ?0.82 to ?0.86) to compost fiber and lignin concentration, and to the Maturity Index (r=0.85). Trends in C mineralization were similar. There were few differences in C mineralization between composts after 48 d of aerobic incubation in soil. Ryegrass harvested 35 and 70 d after compost application was not strongly affected by compost maturity, and relatively immature composts were phytotoxic to tomato seedlings. Methods of characterizing compost maturity and stability that more realistically reflect the composting process are better predictors of N release and potential plant inhibition after incorporation into soil.     

Hydrolysis and Fermentation of Pericarp and Endosperm Fibers Recovered from Enzymatic Corn Dry‐Grind Process

A modified dry‐grind corn process has been developed that allows recovery of both pericarp and endosperm fibers as coproducts at the front end of the process before fermentation. The modified process is called enzymatic milling (E‐Mill) dry‐grind process. In a conventional dry‐grind corn process, only the starch component of the corn kernel is converted into ethanol. Additional ethanol can be produced from corn if the fiber component can also be converted into ethanol. In this study, pericarp and endosperm fibers recovered in the E‐Mill dry‐grind process were evaluated as a potential ethanol feedstock. Both fractions were tested for fermentability and potential ethanol yield. Total ethanol yield recovered from corn by fermenting starch, pericarp, and endosperm fibers was also determined. Results show that endosperm fiber produced 20.5% more ethanol than pericarp fiber on a g/100 g of fiber basis. Total ethanol yield obtained by fermenting starch and both fiber fractions was 0.370 L/kg compared with ethanol yield of 0.334 L/kg obtained by fermenting starch alone.     

Fiber Separated from Distillers Dried Grains with Solubles as a Feedstock for Ethanol Production

In the dry-grind process, corn starch is converted into sugars that are fermented into ethanol. The remaining corn components (protein, fiber, fat, and ash) form a coproduct, distillers dried grains with solubles (DDGS). In a previous study, the combination of sieving and elutriation (air classification), known as the elusieve process, was effective in separating fiber from DDGS. In this study, elusieve fiber was evaluated for ethanol production and results were compared with those reported in other studies for fiber from different corn processing techniques. Fiber samples were pretreated using acid hydrolysis followed by enzymatic treatment. The hydrolyzate was fermented using Escherichia coli FBR5 strain. Efficiency of ethanol production from elusieve fiber was 89–91%, similar to that for pericarp fiber from wet-milling and quick fiber processes (86–90%). Ethanol yields from elusieve fiber were 0.23–0.25 L/kg (0.027–0.030 gal/lb); similar to ethanol yields from wet-milling pericarp fiber and quick fiber. Fermentations were completed within 50 hr. Elusieve fiber conversion could result in 1.2–2.7% increase in ethanol production from dry-grind plants. It could be economically feasible to use elusieve fiber along with other feedstock in a plant producing ethanol from cellulosic feedstocks. Due to the small scale of operation and the stage of technology development for cellulosic conversion to ethanol, implementation of elusieve fiber conversion to ethanol within a dry-grind plant may not be currently economically feasible.     

Soil quality and fertility in sustainable agriculture,with a contribution to the biological classification of agricultural soils

Soils and crops are particularly vulnerable to climate change and environmental stresses. In many agrosystems, soil biodiversity and ecosystem services provided by soils are under threat from a range of natural and human drivers. Agricultural soils are often subject to agronomic practices that disrupt soil trophic networks and make soils less productive in the long term. In this scenario, sustainable soil use aimed at improving plant/root status, growth and development plays a crucial role for enhancing the biological capacity of agricultural soils. This commentary paper is divided into the following four main sections: (i) the contentious nature of soil organic matter; (ii) soil biological quality/fertility; (iii) soil classification; and, (iv) which agricultural practices can be defined as sustainable? The published literature was analyzed within a holistic framework, with agrosystems considered as living systems where soil, vegetation, fauna and microorganisms co-evolve and are reciprocally influenced. Ultimately, this article will suggest a better stewardship of agricultural soils as a natural capital.     

Evidence for enhanced N availability during switchgrass establishment and seeding year production following inoculation with rhizosphere endophytes

Improvement in sustainable production of switchgrass (SG, Panicum virgatum L), as a purpose-grown biomass feedstock crop, could be realized through investigation of plant–microbe interactions associated with plant growth promoting rhizobacteria (PGPR), capable of biological nitrogen fixation (BNF). The objective of this study is to increase establishment year production of SG biofuels by inoculation with a mixed PGPR inoculum. We isolated pure strains of N₂-fixing, and other PGPR, from SG rhizomes. The bacteria were identified as Paenibacillus polymyxa, an N₂-fixing bacterium, and other PGPR capable of solubilizing phosphate and/or producing auxins. Field trials utilizing these strains in a mixed PGPR inoculum showed that inoculated plants contained more N in tillers during anthesis but not at senescence, suggesting that more N could be cycled to belowground roots and rhizomes for winter storage. The amount of N removal in biomass and recovery of fertilizer N were also greater for inoculated than uninoculated plants. PGPR inoculation also resulted in positive N balances, suggesting improved access to N from non-fertilizer N sources, possibly through BNF and improved soil N uptake. Overall, inoculation of SG with PGPR enhanced N acquisition and could be an effective strategy to increase the establishment year production of this crop.     

Soil protists: An untapped microbial resource of agriculture and environmental importance

Protists are essential components of soil biodiversity and ecosystem functioning. They play a vital role in the microbial food web as consumers of bacteria, fungi, and other small eukaryotes and are also involved in maintaining soil fertility and plant productivity. Protists also contribute to regulating and shaping the bacterial community in terrestrial ecosystems via specific prey spectra. They play a role in plant growth promotion and plant health improvement,mostly via nutrient cycling, grazing, and the activation of bacterial genes required for plant growth and phytopathogen suppression. Thus, protists may prove to be a useful inoculant as biofertilizer and biocontrol agent. They can also be applied as model organisms as bioindicators of soil health. Despite their usefulness and essentiality, they are often forgotten and under-researched components of the soil microbiome, as most of our research focuses on bacteria and fungi. In this review, we provide an overview of the role of protists in plant productivity and plant health management and in shifts in soil bacterial community composition, as well as their roles as bioindicator. We also discuss the perspectives of knowledge gaps and future prospects to further improve soil biology.More research in soil protistology will provide insights into sustainable agriculture and environmental health alongside the study of bacteria and fungi.     

Physical and Chemical Characterization of Fuel Ethanol Coproducts Relevant to Value‐Added Uses

One of the fastest growing industries in the United States is the fuel ethanol industry. In terms of ethanol production capability, the industry has grown by more than 600% since the year 2000. The major coproducts from corn‐based ethanol include distillers dried grains with solubles (DDGS) and carbon dioxide. DDGS is used as a livestock feed because it contains high quantities of protein, fiber, amino acids, and other nutrients. The goal of this study was to quantify various chemical and physical properties of DDGS, distillers wet grains (DWG), and distillers dried grain (DDG) from several plants in South Dakota. Chemical properties of the DDGS included crude ash (5.0–21.93%), neutral detergent fiber (NDF) (26.32–43.50%), acid detergent fiber (ADF) (10.82–20.05%), crude fiber (CF) (8.14–12.82%), crude protein (27.4–31.7%), crude fat (7.4–11.6%), and total starch (9.19–14.04%). Physical properties of the DDGS included moisture content (3.54–8.21%), A_w (0.42–0.53), bulk density (467.7–509.38 kg/m³), thermal conductivity (0.05–0.07 W/m·°C), thermal diffusivity (0.1–0.17 mm²/sec), color L* (36.56–50.17), a* (5.2–10.79), b* (12.53–23.36), and angle of repose (25.7–47.04°). These properties were also determined for DWG and DDG. We also conducted image analysis and size determination of the DDGS particles. Carbon group characterization in the DDGS and DDG samples were determined using NMR spectroscopy; O‐alkyl comprised >50% of all DDGS samples. Results from this study showed several possibilities for using DDGS in applications other than animal feed. Possibilities include harvesting residual sugars, producing additional ethanol, producing value‐added compounds, using as food‐grade additives, or even using as inert fillers for biocomposites.     

Chemical composition, in vitro fermentation characteristics, and in vivo digestibility responses by dogs to select corn fibers

The objective was to examine the chemical composition, in vitro fermentation characteristics, and in vivo digestibility responses of fiber-rich corn coproducts resulting from corn wet milling. Native corn fibers, native corn fibers with fines, hydrolyzed corn fibers, and hydrolyzed extracted corn fibers were analyzed chemically and their capacity to produce short-chain fatty acids determined. Ash content was low (<1.2%), crude protein content varied little, but fat and fiber concentrations varied widely. Most fiber was in the insoluble form, with glucose being predominant followed by xylose. Total short-chain fatty acid production ranged from 211.6 to 699.52 micromol/g of dry matter, whereas branched-chain fatty acid production was low. Four corn fibers (native and processed) were included in a canine diet matrix at the 7% inclusion level. Nutrient digestibility, food intake, and fecal characteristics were not affected by corn fiber inclusion in canine diets, suggesting that they should be considered as potential dietary fiber sources in dog foods.     

Laboratory Measurement of Yield and Composition of Dry‐Milled Corn Fractions Using a Shortened,Single‐Stage Tempering Procedure

The objective was to describe a laboratory‐scale dry‐milling procedure that used single‐stage tempering and determine the effect of hybrid on yields and fraction compositions in milled corn. Samples of 11 commercially available hybrids were processed through a laboratory dry‐milling procedure that used 1 kg samples of corn to produce milling fractions of large grits, small grits, fines, germ, and pericarp. Compositions of milling fractions (protein, neutral detergent fiber, ash, and crude fat) were determined. The procedure used a single‐stage tempering step that increased corn moisture from 15 to 23.5% wb during an 18‐min tempering period. Germ were separated from endosperm particles using a roller mill followed by screening over a sieve with 1.68‐mm openings. Coefficients of variability were small, indicating acceptable repeatability. Overall yield means were 39.2, 25.3, 13.8, 78.2, 14.3, and 6.8 g/100 g (db) for large grits, small grits, fines, total endosperm, germ, and pericarp, respectively. There were effects due to hybrid (P < 0.05) on fraction yields and compositions of milling fractions. Correlations (r) among endosperm fractions (large grits, small grits, and fines) ranged from 0.54 to |–0.92|. Correlations among endosperm fractions and germ and pericarp were <0.68. The developed dry‐milling method estimated milling yields among hybrids with low standard deviations relative to the means and should be a useful tool for research and industry in measuring dry‐milling characteristics.     

EVALUATION OF NUTRITIONAL COMPOSITION OF PLANT SPECIES OF SOONE VALLEY IN PUNJAB,PAKISTAN

The key component for global sustainability is plant diversity, an essential for living sources on this planet. An investigation was carried out in the Soone Valley, Punjab, Pakistan to determine the nutritional value of plant diversity in relation to requirements of grazing ruminants therein. Various parameters such as moisture content, crude protein, mineral matter, fat fiber content, dry matter, nitrogen free extractable substances, and net energy were evaluated in this investigation. Results showed that various plant species studied exhibited fluctuation in all parameters in this valley. Correlation studies also indicated that various parameters showed negative as well as positive significant relationships with various parameters of soil in this valley. The information will be useful in further conservation program. A. farnesiana was negatively correlated (?0.335) with protein and mineral matter (?0.048). Significant correlations of different plant species regarding nitrogen- phosphorus- potassium (NPK) were recorded with net energy. Various variables studied in this investigation demonstrated their importance to be used in further conservation, research, and grazing livestock programs.