Relationships between dairy slurry total solids, gas emissions, and surface crusts

Livestock slurry storages are sources of methane (CH?), nitrous oxide (NO?), and ammonia (NH?) emissions. Total solids (TS) content is an indicator of substrate availability for CH? and N?O production and NH? emissions and is related to crust formation, which can affect these gas emissions. The effect of TS on these emissions from pilot-scale slurry storages was quantified from 20 May through 16 Nov. 2010 in Nova Scotia, Canada. Emissions from six dairy slurries with TS ranging from 0.3 to 9.5% were continuously measured using flow-through steady-state chambers. Methane emissions modeled using the USEPA methodology were compared with measured data focusing on emissions when empty storages were filled, and retention times were >30 d with undegraded volatile solids (VS) remaining in the system considered available for CH? production (VS carry-over). Surface crusts formed on all the slurries. Only the slurries with TS of 3.2 and 5.8% were covered completely for ～3 mo. Nitrous oxide contributed <5% of total greenhouse gas emissions for all TS levels. Ammonia and CH? emissions increased linearly with TS despite variable crusting, suggesting substrate availability for gas production was more important than crust formation in regulating emissions over long-term storage. Modeled CH? emissions were substantially higher than measured data in the first month, and accounting for this could improve overall model performance. Carried-over VS were a CH? source in months 2 through 6. The results of this study suggest that substrate availability regulates emissions over long-term storage and that modifying the USEPA model to better describe carbon cycling is warranted.     

Oxygen distribution and potential ammonia oxidation in floating, liquid manure crusts

Floating, organic crusts on liquid manure, stored as a result of animal production, reduce emission of ammonia (NH3) and other volatile compounds during storage. The occurrence of NO2- and NO3- in the crusts indicate the presence of actively metabolizing NH3-oxidizing bacteria (AOB) which may be partly responsible for this mitigation effect. Six manure tanks with organic covers (straw and natural) were surveyed to investigate the prevalence and potential activity ofAOB and its dependence on the O2 availability in the crust matrix as studied by electrochemical profiling. Oxygen penetration varied from <1 mm in young, poorly developed natural crusts and old straw crusts, to several centimeters in the old natural crusts. The AOB were ubiquitously present in all crusts investigated, but nitrifying activity could only be detected in old natural crusts and young straw crust with high O2 availability. In old natural crusts, total potential NH3 oxidation rates were similar to reported fluxes of NH3 from slurry without surface crust. These results indicate that old, natural surface crusts may develop into a porous matrix with high O2 availability that harbors an active population of aerobic microorganisms, including AOB. The microbial activity may thus contribute to a considerable reduction of ammonia emissions from slurry tanks with well-developed crusts.     

Methane production during storage of anaerobically digested municipal organic waste

Anaerobic digestion of source-separated municipal organic waste is considered feasible in Denmark. The limited hydraulic retention in the biogas reactor (typically 15 d) does not allow full degradation of the organic waste. Storage of anaerobically digested municipal organic waste can therefore be a source of methane (CH4) emission that may contribute significantly to the potential global warming impact from the waste treatment system. This study provides a model for quantifying the CH4 production from stored co-digested municipal organic waste and estimates the production under typical Danish climatic conditions, thus quantifying the potential global warming impact from storage of the digested municipal organic waste before its use on agricultural land. Laboratory batch tests on CH4 production as well as temperature measurements in eight full-scale storage tanks provided data for developing a model estimating the CH4 production in storage tanks containing digested municipal organic waste. The temperatures measured in separate storage tanks on farms receiving digested slurry were linearly correlated with air temperature. In storage tanks receiving slurry directly from biogas reactors, significantly higher temperatures were measured due to the high temperatures of the effluent from the reactor. Storage tanks on Danish farms are typically emptied in April and have a constant inflow of digested material. During the warmest months the content of digested material is therefore low, which limits the yearly CH4 production from storage.     

Effects of cattle slurry acidification on ammonia and methane evolution during storage

Slurry acidification before storage is known to reduce NH(3) emissions, but recent observations have indicated that CH(4) emissions are also reduced. We investigated the evolution of CH(4) from fresh and aged cattle slurry during 3 mo of storage as influenced by pH adjustment to 5.5 with sulfuric acid. In a third storage experiment, cattle slurry acidified with commercial equipment on two farms was incubated. In the manipulation experiments, effects of acid and sulfate were distinguished by adding hydrochloric acid and potassium sulfate separately or in combination, rather than sulfuric acid. In one experiment sulfur was also added to slurry as the amino acid methionine in separate treatments. In each treatment 20-kg portions of slurry (n = 4) were stored for 95 d. All samples were subsampled nine to 10 times for determination of NH(3) and CH(4) evolution rates using a 2-L flow-through system. In all experiments, the pH of acidified cattle slurry increased gradually to between 6.5 and 7. Acidification of slurry reduced the evolution of CH(4) by 67 to 87%. The greatest reduction was observed with aged cattle slurry, which had a much higher potential for CH(4) production than fresh slurry. Sulfate and methionine amendment to cattle slurry without pH adjustment also significantly inhibited methanogenesis, probably as a result of sulfide production. The study suggests that complex microbial interactions involving sulfur transformations and pH determine the potential for CH(4) emission during storage of cattle slurry, and that slurry acidification may be a cost-effective greenhouse gas mitigation option.     

Effect of cattle slurry separation on greenhouse gas and ammonia emissions during storage

Storage of cattle slurry leads to emissions of methane (CH(4)), nitrous oxide (N(2)O), ammonia (NH(3)), and carbon dioxide (CO(2)). On dairy farms, winter is the most critical period in terms of slurry storage due to cattle housing and slurry field application prohibition. Slurry treatment by separation results in reduced slurry dry matter content and has considerable potential to reduce gaseous emissions. Therefore, the efficiency of slurry separation in reducing gaseous emissions during winter storage was investigated in a laboratory study. Four slurry fractions were obtained: a solid and a liquid fraction by screw press separation (SPS) and a supernatant and a sediment fraction by chemically enhanced settling of the liquid fraction. Untreated slurry and the separated fractions were stored in plastic barrels for 48 d under winter conditions, and gaseous emissions were measured. Screw press separation resulted in an increase of CO(2) (650%) and N(2)O (1240%) emissions due to high releases observed from the solid fraction, but this increase was tempered by using the combined separation process (CSP). The CSP resulted in a reduction of CH(4) emissions ( approximately 50%), even though high emissions of CH(4) (46% of soluble C) were observed from the solid fraction during the first 6 d of storage. Screw press separation increased NH(3) emissions by 35%, but this was reduced to 15% using the CSP. During winter storage greenhouse gas emissions from all treatments were mainly in the form of CH(4) and were reduced by 30 and 40% using SPS and CSP, respectively.     

The fate of sulfate in acidified pig slurry during storage and following application to cropped soil

Acidification of slurry with sulfuric acid is a recent agricultural practice that may serve a double purpose: reducing ammonia emission and ensuring crop sulfur sufficiency. We investigated S transformations in untreated and acidified pig slurry stored for up to 11 mo at 2, 10, or 20 degrees C. Furthermore, the fertilizer efficiency of sulfuric acid in acidified slurry was investigated in a pot experiment with spring barley. The sulfate content from acidification with sulfuric acid was relatively stable and even after 11 mo of storage the majority was in the plant-available sulfate form. Microbial sulfate reduction during storage of acidified pig slurry was limited, presumably due to initial pH effects and a limitation in the availability of easily degradable organic matter. Sulfide accumulation was observed during storage but the sulfide levels in acidified slurry did not exceed those of the untreated slurry for several months after addition. The S fertilizer value of the acidified slurry was considerable as a result of the stable sulfate pool during storage. The high content of inorganic S in the acidified slurry may potentially lead to development of odorous volatile sulfur-containing compounds and investigations are needed into the relationship between odor development and the C and S composition of the slurry.     

Methane oxidation in freely and poorly drained grassland soils and effects of cattle urine application

A sink for atmospheric methane (CH4) is microbial oxidation in soils. We report CH4 oxidation rates in freely and poorly drained soils on an intensively managed dairy farm. Following cattle urine application to half the plots (650 kg of nitrogen [N] ha(-1)) 31 chamber measurements were made over 100 d during autumn and winter. In the control plots, the freely and poorly drained soils' integrated CH4 oxidation rates averaged 1.8+/-0.2 and 0.6+/-0.1 kg CH4 ha(-1) yr(-1), respectively. In the poorly drained soil, the highest CH4 oxidation rates occurred when water-filled pore space (WFPS)<56% and CH4 oxidation rate declined by ninefold to near zero as WFPS increased from 56 to 68%. Urine application induced the freely and poorly drained soils' CH4 oxidation rates to decline for up to 2 mo by 0.7+/-0.2 and 0.4+/-0.1 kg CH4 ha(-1) yr(-1), respectively. The two soils' responses were thus not significantly different. After urine application, soil pore space CH4 concentration profiles suggested a simultaneous inhibition of bacteria that were CH4 oxidizers and stimulation of CH4 producers.     

Methane oxidation in two Swedish landfill covers measured with carbon-13 to carbon-12 isotope ratios

The release of methane (CH4) from landfills to the atmosphere and the oxidation of CH4 in the cover soils were quantified with static chambers and a 13C-isotope technique on two landfills in Sweden. One of the landfills had been closed and covered 17 years before this investigation while the other was recently covered. On both landfills, the tops of the landfills were compared with the sloping parts in the summer and winter. Emitted CH4, captured in chambers, was significantly enriched in 13C during summer compared with winter (P < 0.0001), and was enriched relative to anaerobic-zone methane. The difference between emitted and anaerobic zone delta 13C-CH4 was used to estimate soil methane oxidation. In summer, these differences ranged from 9 to 26@1000, and CH4 oxidation was estimated to be between 41 and 50% of the produced CH4 in the new landfill, and between 60 and 94% in the old landfill. In winter, when soil temperature was below 0 degree C, no difference in delta 13C was observed between emitted and anaerobic-zone CH4, suggesting that there was no soil oxidation. The temperature effect shown in this experiment suggests that there may be both seasonal and latitudinal differences in the importance of landfill CH4 oxidation. Finally the isotopic fractionation factor (alpha) varied from 1.023 to 1.038 and was temperature dependent, increasing at colder temperatures. Methanotrophic bacteria appeared to have high growth efficiencies and the majority of the methane consumed in incubations did not result in immediate CO2 production.     

Evaluating slurry broadcasting and injection to ley for phosphorus losses and fecal microorganisms in surface runoff

The recent growth in the size of dairy cattle farms and the concentration of farms into smaller areas in Finland may increase local water pollution due to increased manure production and slurry application to grass. Therefore, a field study was conducted to monitor losses of total phosphorus (TP), dissolved reactive phosphorus (DRP), and fecal microorganisms in surface runoff from a perennial ley. Cattle slurry was added once a year in June 1996-1997 (Study I) and biannually in June and October 1998-2000 (Study II). The slurry was surface broadcast or injected into the clay soil. The field had a slope of 0.9 to 1.7%. Mineral fertilizer was applied on control plots. Biannual slurry broadcasting increased DRP (p < 0.001) and TP losses (p < 0.001) and numbers of fecal microorganisms in surface runoff waters. The highest losses of TP (2.7 kg ha(-1) yr(-1)) and DRP (2.2 kg ha(-1) yr(-1)) and the highest numbers of fecal coliforms (880 colony-forming units [CFU] per 100 mL) and somatic coliphages (2700 plaque-forming units [PFU] per 100 mL) were measured after broadcasting slurry to wet soil followed by rainfall in fall 1998. Injection reduced the TP and DRP losses in surface runoff by 79 and 86%, respectively, compared with broadcasting (17 Oct. 1998-27 Oct. 1999). Corresponding numbers for fecal coliforms were 350 CFU (100 mL)(-1) and for somatic coliphages were 110 PFU (100 mL)(-1) in surface runoff after injection in October 1998. Slurry injection should be favored when spreading slurry amendments to grassland to avoid losses of P and fecal microorganisms in runoff to surface waters.     

Methane oxidation in an intensively cropped tropical rice field soil under long-term application of organic and mineral fertilizers

Methane (CH4) oxidation is the only known biological sink process for mitigating atmospheric and terrestrial emissions of CH4, a major greenhouse gas. Methane oxidation in an alluvial soil planted to rice (Oryza sativa L.) under long-term application of organic (compost with a C/N ratio of 21.71), and mineral fertilizers was measured in a field-cum-laboratory incubation study. Oxidation rates were quantified in terms of decrease in the concentration of CH4 in the headspace of incubation vessels and expressed as half-life (t(1)2) values. Methane oxidation rates significantly differed among the treatments and growth stages of the rice crop. Methane oxidation rates were high at the maximum tillering and maturity stages, whereas they were low at grain-filling stage. Methane oxidation was low (t(1)2) = 15.76 d) when provided with low concentration of CH4. On the contrary, high concentration of CH4 resulted in faster oxidation (t(1)2) = 6.67 d), suggesting the predominance of "low affinity oxidation" in rice fields. Methane oxidation was stimulated following the application of mineral fertilizers or compost implicating nutrient limitation as one of the factors affecting the process. Combined application of compost and mineral fertilizer, however, inhibited CH4 oxidation probably due to N immobilization by the added compost. The positive effect of mineral fertilizer on CH4 oxidation rate was evident only at high CH4 concentration (t(1)2 = 4.80 d), while at low CH4 concentration their was considerable suppression (t(1) = 17.60 d). Further research may reveal that long-term application of fertilizers, organic or inorganic, may not inhibit CH4 oxidation.     

Optimization of Fenton's oxidation of chemical laboratory wastewaters using the response surface methodology

Establishing a treatment process for practical and economic disposal of laboratory wastewaters has become an urgent environmental concern of the Department of Chemical Engineering of the Universidade Estadual de Maringá (State University of Maringá), Brazil. Fenton and related reactions are potentially useful oxidation processes for destroying toxic organic compounds in water. In these reactions, hydrogen peroxide is combined with ferrous or ferric iron in the presence or absence of light to generate hydroxyl radicals (.OH). The feasibility of Fenton's reagent to treat waste chemicals from an academic research laboratory was investigated in this study. A response surface methodology was applied to optimize the Fenton oxidation process conditions using chemical oxygen demand (COD) removal as the target parameter to optimize, and the reagent concentrations, as related to the initial concentration of organic matter in the effluent, and pH as the control factors to be optimized. Maximal COD removal (92.3%) was achieved when wastewater samples were treated at pH 4 in the presence of hydrogen peroxide and iron in the ratios [COD]:[H2O2]=1:9 and [H2O2]:[Fe2+]=4.5:1. Under these conditions, it was possible to obtain simultaneously maximal COD removal and minimal chemical sludge after treatment, which is a residue that needs further processing.     

A response surface methodology to address uncertainties in cap rock failure assessment for CO2 geological storage in deep aquifers

Cap rock failure assessment, either tensile fracturing or shear slip reactivation of pre-existing fault, is a key issue for preventing CO₂ leakage from deep aquifer reservoirs up to the surface. For an appropriate use in risk management, the uncertainties associated with such studies should be investigated. Nevertheless, uncertainty analysis requires multiple simulations and a direct use of conventional numerical approaches might be too computer time consuming. An alternative is to use conventional analytical models, but their assumptions appear to be too conservative. An intermediate approach is then proposed based on the response surface methodology, consisting in estimating the effective stress state after CO₂ injection as a linear combination of the most influential site properties based on a limited number of numerical simulations. The decision maker is provided with three levels of information: (1) the identification of the most important site properties; (2) an analytical model for a quick assessment of the maximal sustainable overpressure and (3) a simplified model to be used in a computationally intensive uncertainty analysis framework. This generic methodology is illustrated with the Paris Basin case using a large-scale hydromechanical model to assess cap rock failure in the injector zone.     

Simulating nitrogen dynamics in agricultural soils fertilized with pig slurry and urea

Within the framework of an interregional project in the Emilia Romagna region of northern Italy, the coupled MACRO-SOILN model was chosen to estimate soil protective capacity against pollutants. The aim of our study was to evaluate the model to better identify key parameters and processes that influence N losses in agricultural soils. Nitrate N content was monitored in soil under corn (Zea mays L.) fertilized with urea and/or pig slurry, in two field experiments performed on four different soils: a Fienili clay, a Barco-like silt, a Sant'Omobono silt loam, and a La Boaria silty clay soil. Measurements were compared with model predictions. For all soils, nitrate content was underestimated on average by 24 to 88% at lower N rates; it was overestimated by 1 to 104% at higher N rates. The root mean square error (RMSE) was equal to 81.1%. Simulation of crop N uptake and soil water flow, estimation of the ammonia losses at pig slurry spreading, and N transformation parameter setting were considered as possible error sources. The calibration of crop N uptake gave rise to good model efficiency index values. The RMSE for the simulation of soil water content varied between 9.8 and 20.2%. A more accurate setting of the ammonia losses and of the feces transformation parameter values could allow the RMSE for the simulation of soil nitrate content to be reduced by no more than 10 to 15%. It is possible for the model not to include the simulation of processes that could have relevant effects on the soil N dynamics.     

Coupled abiotic-biotic mineralization of 2,4,6-trinitrotoluene (TNT) in soil slurry

The explosive 2,4,6-trinitrotoluene (TNT) is a contaminant of soils and ground waters worldwide. To help alleviate such environmental contamination, we investigated a coupled abiotic-biotic treatment scheme for remediating TNT-contaminated soil in slurry solutions. Two types of soil were used (sandy and silt loam) to simulate different soils that might be found at actual sites. These soils were subsequently contaminated with 5000 mg kg(-1) TNT. Mineralization of TNT was initially optimized for minimum reactant use (Fe(3+) and H(2)O(2)) and maximum soil slurry percentage (percent solids) using modified Fenton reactions conducted in the absence of light followed by the addition of an uncharacterized aerobic biomass. Greater than 97% TNT degradation was observed under optimum reaction conditions for both soils. Using two optimum reactant concentrations for each soil, coupled abiotic-biotic reactions showed an increase in TNT mineralization, from 41 to 73% and 34 to 64% in the sandy soil (10 and 20% slurry, respectively, 1470 mM H(2)O(2)), and increases from 12 to 23% and 13 to 28% in the silt loam soil (5% slurry, 294 and 1470 mM H(2)O(2), respectively). These results show promise in the use of combined abiotic-biotic treatment processes for soils contaminated with high concentrations of TNT.     

Estimation and Spatiotemporal Analysis of Methane Emissions from Agriculture in China

Estimating and analyzing the temporal and spatial patterns of methane emissions from agriculture (MEA) will help China formulate mitigation and adaptation strategies for the nation’s agricultural sector. Based on the Tier 2 method presented in the 2006 guidelines of the Intergovernmental Panel on Climate Change (IPCC) and on existing reports, this article presents a systematic estimation of MEA in China from 1990 to 2006, with a particular emphasis on trends and spatial distribution. Results from our study indicate that China’s MEA rose from 16.37 Tg yr⁻¹ in 1990 to 19.31 Tg yr⁻¹ in 2006, with an average annual increase of 1.04%. Over the study period, while emissions from field burning of crop residues remained rather low, those from rice cultivation and from livestock typically decreased and increased, respectively, showing extremely opposite trends that chiefly resulted from changes in the cultivated areas for different rice seasons and changes in the populations of different animal species. Over the study period, China’s high-MEA regions shifted generally northward, chiefly as a result of reduced emissions from rice cultivation in most of China’s southern provinces and a substantial growth in emissions from livestock enteric fermentation in most of China’s northern, northeastern, and northwestern provinces. While this article provides significant information on estimates of MEA in China, it also includes some uncertainties in terms of estimating emissions from each source category. We conclude that China’s MEA will likely continue to increase in the future and recommend a demonstration study on MEA mitigation along the middle and lower reaches of the Yellow River. We further recommend enhanced data monitoring and statistical analysis, which will be essential for preparation of the national greenhouse gas (GHG) inventory.     

Distribution of phosphorus in manure slurry and its infiltration after application to soils

Computer models help identify agricultural areas where P transport potential is high, but commonly used models do not simulate surface application of manures and P transport from manures to runoff. As part of an effort to model such P transport, we conducted manure slurry separation and soil infiltration experiments to determine how much slurry P infiltrates into soil after application but before rain, thus becoming less available to runoff. We applied dairy and swine slurry to soil columns and after both 24 and 96 h analyzed solids remaining on the soil surface for dry matter, total phosphorus (TP), and water-extractable inorganic (WEIP) and organic (WEOP) phosphorus. We analyzed underlying soils for Mehlich-3 and water-extractable P. We also conducted slurry separation experiments by sieving, centrifuging, and suction-filtering to determine which method could easily estimate slurry P infiltration into soils. About 20% of slurry solids and 40 to 65% of slurry TP and WEIP infiltrated into soil after application, rendering this P less available to transport in runoff. Slurry separation by suction-filtering through a screen with 0.75-mm-diameter openings was the best method to estimate this slurry P infiltration. Measured quantities of manure WEOP changed too much during experiments to estimate WEOP infiltration into soil or what separation method can approximate infiltration. Applying slurries to soils always increased soil P in the top 0 to 1 cm of soil, frequently in the 1- to 2-cm depth of soil, but rarely below 2 cm. Future research should use soils with coarser texture or large macropores, and slurry with low dry matter content (1-2%).     

Dairy slurry application method impacts ammonia emission and nitrate in no-till corn silage

Reducing ammonia (NH3) emissions through slurry incorporation or other soil management techniques may increase nitrate (NO3) leaching, so quantifying potential losses from these alternative pathways is essential to improving slurry N management. Slurry N losses, as NH3 or NO3 were evaluated over 4 yr in south-central Wisconsin. Slurry (i.e., dairy cow [Bos taurus] manure from a storage pit) was applied each spring at a single rate (-75 m3 ha(-1)) in one of three ways: surface broadcast (SURF), surface broadcast followed by partial incorporation using an aerator implement (AER-INC), and injection (INJ). Ammonia emissions were measured during the 120 h following slurry application using chambers, and NO3 leaching was monitored in drainage lysimeters. Yield and N3 uptake of oat (Avena sativa L.), corn (Zea mays L.), and winter rye (Secale cereale L.) were measured each year, and at trial's end soils were sampled in 15- to 30-cm increments to 90-cm depth. There were significant tradeoffs in slurry N loss among pathways: annual mean NH3-N emission across all treatments was 5.3, 38.3, 12.4, and 21.8 kg ha(-1) and annual mean NO3-N leaching across all treatments was 24.1, 0.9, 16.9, and 7.3 kg ha' during Years 1, 2, 3, and 4, respectively. Slurry N loss amounted to 27.1% of applied N from the SURF treatment (20.5% as NH3-N and 6.6% as NO,-N), 23.3% from AER-INC (12.0% as NH3-N and 11.3% as NO3-N), and 9.19% from INJ (4.4% as NH3-N and 4.7% as NO3-N). Although slurry incorporation decreased slurry N loss, the conserved slurry N did not significantly impact crop yield, crop N uptake or soil properties at trial's end.     

四川省煤层气开发利用的必要性与可行性分析

四川省拥有丰富的煤层气资源，预测资源量3481亿m^3。煤层气的开发利用有利于弥补常规能源的不足，有利于改善煤矿安全生产条件和减轻大气污染。目前国内外煤层气地面开采技术、井下瓦斯抽放技术均已成熟，四川煤层气开发利用是可行的。     

Carbon storage potential in natural fiber composites

The environmental performance of hemp based natural fiber mat thermoplastic (NMT) has been evaluated in this study by quantifying carbon storage potential and CO₂ emissions and comparing the results with commercially available glass fiber composites. Non-woven mats of hemp fiber and polypropylene matrix were used to make NMT samples by film-stacking method without using any binder aid. The results showed that hemp based NMT have compatible or even better strength properties as compared to conventional flax based thermoplastics. A value of 63 MPa for flexural strength is achieved at 64% fiber content by weight. Similarly, impact energy values (84–154 J/m) are also promising. The carbon sequestration and storage by hemp crop through photosynthesis is estimated by quantifying dry biomass of fibers based on one metric ton of NMT. A value of 325 kg carbon per metric ton of hemp based composite is estimated which can be stored by the product during its useful life. An extra 22% carbon storage can be achieved by increasing the compression ratio by 13% while maintaining same flexural strength. Further, net carbon sequestration by industrial hemp crop is estimated as 0.67 ton/h/year, which is compatible to all USA urban trees and very close to naturally, regenerated forests. A comparative life cycle analysis focused on non-renewable energy consumption of natural and glass fiber composites shows that a net saving of 50 000 MJ (3 ton CO₂ emissions) per ton of thermoplastic can be achieved by replacing 30% glass fiber reinforcement with 65% hemp fiber. It is further estimated that 3.07 million ton CO₂ emissions (4.3% of total USA industrial emissions) and 1.19 million m³ crude oil (1.0% of total Canadian oil consumption) can be saved by substituting 50% fiber glass plastics with natural fiber composites in North American auto applications. However, to compete with glass fiber effectively, further research is needed to improve natural fiber processing, interfacial bonding and control moisture sensitivity in longer run.