Solid biofuels, including straw as production residue, are still the largest energy feedstock in the structure of primary energy production from renewable energy sources. However, the properties of ...straw as a solid biofuel can vary depending on the species from which it was produced and the harvest period and year. Therefore, this study aimed to assess the thermophysical properties and elemental composition of six types of straw (rye, oat, triticale, wheat, corn, and rapeseed straw) obtained over three consecutive years (2020, 2021, 2022). Rye straw had the lowest moisture (mean: 10.55%), ash (mean: 2.71% DM), nitrogen (mean: 0.54% DM) and chlorine (mean: 0.046% DM) contents and the highest carbon content (mean: 47.93% DM), a higher heating value—HHV (mean: 19.03 GJ Mg−1 DM) and a lower heating value—LHV (mean: 15.71 GJ Mg−1). Triticale straw had similar properties, classifying it into the same cluster as rye straw. Corn straw had a remarkably high moisture content (mean: 48.91%), low LHV and high chlorine content. Rapeseed straw contained high levels of Cl, S, N and ash, and they were 643%, 481%, 104% and 169% higher, respectively, than those in rye straw. The sulfur, chlorine and moisture contents of the six straw types under study were highly variable during the three years of the study. Knowledge of the properties of different types of straw as energy feedstocks facilitates the logistics and organization of the supply of bioenergy installations. However, further research is needed, especially studies assessing the energy intensity and logistical costs of different types of straw used for energy purposes.
Grinding experiments were conducted on non-treated and steam exploded barley, canola, oat and wheat straw using a forage chopper and a hammer mill (screen sizes of 30, 6.4, 3.2 and 1.6 mm) to ...determine specific energy requirements, and geometric mean particle size and distribution of ground material. The bulk density of non-treated biomass was significantly higher than bulk density of steam exploded agricultural biomass. For non-treated agricultural straw, the particle density of canola and oat straw significantly increased with a decrease in hammer mill screen size from 30 to 1.6 mm. The particle density of steam exploded barley and oat straw was significantly higher than non-treated straw, except for barley at 6.4 mm hammer mill screen size. The particle density of steam exploded canola straw was not statistically different from non-treated straw. The chopper consumed highest (3.15 ± 0.09 kWh t
−1) and lowest (1.96 ± 0.33 kWh t
−1) specific energy to chop barley and canola straw, respectively. The highest and lowest specific energy was consumed by wheat (42.57 ± 2.04 kWh t
−1) at 1.6 mm and canola (1.46 ± 0.30 kWh t
−1) straws ground using 30 mm hammer mill screen size, respectively. For steam exploded agricultural biomass, the highest and lowest specific energy was consumed by oat (33.18 ± 3.10 kWh t
−1) at 1.6 mm and canola (2.69 ± 0.26 kWh t
−1) straws ground using 6.4 mm hammer mill screen size, respectively. Specific energy required by hammer mill to grind non-treated and steam exploded barley, canola, oat and wheat straw showed a negative power correlation with hammer mill screen sizes.
•First measurement of Emission Factors (EFs) from burning rice straw in the Philippines.•The EFs of straw burning were 4.51g CH4 and 0.069gN2O per kg dry weight of straw.•The obtained EFs were used ...to estimate the CH4 and N2O fluxes during open-field burning of straw.
Open-burning of rice straw residues pollutes the air and contributes to global warming through emissions of greenhouse gases (GHGs). Although burning of straw residues emits large amounts of CO2, this component of the smoke is not considered as net GHG emissions and only concludes the annual carbon cycle that has started with photosynthesis. Hence, we focused on emissions of CH4 and N2O from open-field burning against a baseline of straw incorporation. The experimental approach combined a newly designed combustion chamber for the collection of smoke followed by chemical analysis (Exp. A) as well as field observations of soil-borne emissions for different straw treatments (Exp. B). At constant straw moisture of 10%, the mass-scaled Emission Factors (EFm) were 4.51g CH4 and 0.069gN2O per kg dry weight (kg−1dw) of straw. In Exp. B, we conducted field trials over two seasons with the following straw management practices: SRt − straw retained including stubbles and incorporated, PSRm − partial straw removal only stubbles incorporated, CSRm − complete straw removal including removal of stubbles, and SB − straw burned followed by incorporation of ash and unburned residues. Soil-borne emissions were recorded with a closed chamber approach whereas straw burning was computed indirectly using the EF from Exp. A. As metrics for comparison, we have used the GWP contributions of CH4 and N2O for the different straw management practices over two cropping seasons in the field. On an annual basis, SRt had the highest total GWP (8023kgCO2eqha−1). SB entailed a GWP of 4913kgCO2eqha−1 that was almost identical to the GWP of PSRm (4531kgCO2eqha−1). CSRm had the lowest GWP (3470kgCO2eqha−1) that was significantly lower than that of SRt. However, full GHG accounting of straw removed from the field will depend on the ensuing utilization of straw and the off-field emissions involved − which was outside of the boundaries of this study. The quantification of open field burning in this study can be instrumental for diverse purposes by providing data of an important component in emission inventories and carbon footprint analysis of rice.
Aim
The selection of suitable mulch methods is of great significance for obtaining the best soil and water conservation function of straw.
Methods
An indoor rainfall simulation experiment was ...conducted to analyze the straw effects on runoff, sediment yield and velocity under two straw mulching methods: straw surface mulch and straw incorporation. Under both methods, 4 straw rates (1.5, 2.5, 3.5, and 4.5 t·hm
−2
) and 3 straw lengths (3–5, 8–10, and 13–15 cm) were considered, and a bare slope was selected as the control.
Results
Compared with the straw surface mulch, there was a lower runoff reduction effect and a higher sediment reduction effect under the straw incorporation. The straw factor contributions to runoff and sediment varied with the mulching method. Compared with the surface mulch, the straw rate generated a higher sediment yield contribution and a lower runoff yield contribution under the straw incorporation. Moreover, the effect of straw length on the flow velocity under the straw surface mulch was greater than that under straw incorporation. Straw reduced the sediment yield mainly by lowering the erosion kinetic energy under the straw surface mulch, while straw could largely reduce the soil erodibility under the straw incorporation. Under the straw surface mulch, the best runoff and sediment reduction effects were achieved when the straw rate reached 4.5 t·hm
−2
and the straw length ranged from 3–5 cm. Under straw incorporation, the best effects were achieved when the straw rate reached 3.5 t·hm
−2
and the straw length ranged from 8–10 cm.
Conclusions
In areas with greater rainfall, straw incorporation should be incorporated. In areas with less rainfall, straw surface mulch should be used. This study provides a reference for the selection of suitable straw mulching methods and an understanding the mechanisms by which straw reduces soil and water loss, on sloping farmland.
Aims
In order to understand the response of soil microbial communities to the long‐term of decomposed straw return, the modifications of soil microbial community structure and composition induced by ...more than 10 years of fresh and decomposed straw return was investigated and the key environmental factors were analysed.
Methods and Results
Phospholipid fatty acid analysis and high‐through sequencing technique were applied to analyse the structure and composition of the soil microbial communities. Compared with fresh straw, returning decomposed straw increased the relative abundance of bacteria and fungi by 1·9 and 7·7% at a rate of ~3750 kg ha−1, and increased by 23·1 and 5·7%, at a rate of ~7500 kg ha−1 respectively. The relative abundance of the bacteria related to soil nitrification increased, but the ones related to soil denitrification decreased with decomposed straw return, which led to higher total nitrogen contents in soils. Moreover, returning decomposed straw reduced pathogenic fungal populations (genus of Alternara), which had significantly positive correlation with soil electric conductivity. It indicated that the long‐term of decomposed straw return might have lower risk of soil‐borne disease mainly for the reasonable soil salinity.
Conclusions
Long‐term of decomposed straw return could provide suitable nutrient and salinity for healthier development of soil microbial community, both in abundance and structure, compared with fresh straw return.
Significance and Impact of the Study
The results of the study helps to better understand how the microbial community modifications induced by decomposed straw return benefit on soil health. The obtained key factors impacting soil microbial community variations is meaningful in soil health management under conditions of straw return.
•α-Cellulose content of rice, wheat, and barley straws was 36.9, 43.0, 39.2%, respectively.•Yield of CNCs were 64, 75, and 69wt% for cellulose of RS, WS and BS, respectively.•Width and length of the ...CNCs were 10–25 and 120–800nm with aspect ratio of 16–19.•Tensile strength increased by 45.7%, 25.2% and 42.6% for RS, WS and BS, respectively.•WVP decreased by 26.3%, 19.1% and 20.4% for RS, WS and BS, respectively.
Cellulose nanocrystals (CNCs) were isolated from rice straw (RS), wheat straw (WS), and barley straw (BS) by using acid hydrolysis method. They were fibrous in shape with length (L) of 120–800nm and width (W) of 10–25nm, aspect ratio (L/W) of 18, 16 and 19, crystallinity index (CI) of 0.663, 0.710, and 0.634, and yield of 64, 75, and 69wt% for RS, WS, and BS respectively. Carboxymethyl cellulose (CMC)/CNC composite films were prepared with various concentration of the CNCs. SEM results showed that the CNCs were evenly distributed in the polymer to form homogeneous films. Mechanical and water vapor barrier properties were varied depending on the type of CNCs and their concentration. Tensile strength (TS) increased by 45.7%, 25.2%, and 42.6%, and the water vapor permeability (WVP) decreased by 26.3%, 19.1%, and 20.4% after forming composite with 5wt% of CNCs obtained from RS, WS, and BS, respectively.
Lignin in straw of herbaceous crops Buranov, Anvar U.; Mazza, G.
Industrial crops and products,
11/2008, Volume:
28, Issue:
3
Journal Article
Peer reviewed
Biomass from herbaceous crops is the largest renewable source for the production of bioproducts and biofuels. The available information about lignins in straw of herbaceous crops is scattered and the ...available reviews generally address wood lignins. This review is focused on the structural characteristics and separation of lignin in the straws of corn, wheat, rice and flax, and it is the first attempt to generalize the information about lignin structure of important herbaceous crops and processes for the separation of lignin from hemicellulose and cellulose in lignocellulosic crop residues. The differences in lignin structures and processes for the fractionation of the major components of straw are highlighted, and the conversion of lignin into value-added products is addressed.
► In spring maize growing period of a sub-humid area, fallow field with wheat straw mulch had a fallow efficiency of 35%. ► Fallow field mulched with plastic sheets had a fallow efficiency of 46.1%. ...► Largest water loss by evaporation occurred during the hottest part of summer. ► Maize plant canopy significantly reduced evaporation due to uptake of soil water and shading of the soil surface.
A field experiment was conducted in a dry sub-humid area to study the effect of plastic sheet mulch and wheat straw mulch on water loss by evaporation (E) under fallow and cropped conditions and water use by transpiration (T) under cropped conditions. Results showed that during the entire spring maize (Zea mays L.) growing period with 305.1mm water of precipitation and irrigation from April 22 to August 28, fallow plots mulched with wheat straw conserved 106.9mm water in the 0–200cm soil layer with a fallow efficiency of 35% while those mulched with plastic sheets conserved 140.6mm water with a fallow efficiency of 46.1%. Although plastic film and wheat straw mulch significantly reduced water loss by E compared to non-mulch that had typically a fallow efficiency of 10–15%, water loss by E was still serious, with the largest water losses occurring during the hottest part of summer (July and August). During this period, it was difficult to reduce E, even when mulch was properly applied. In contrast, water losses due to E were much lower when maize plants were grown on the plots. In this case, maize plants continuously took up water from soil, leading to a reduction in the amount of soil water available for E. The large canopy shaded the soil surface and reduced water loss by evaporation. Only 20mm, or 6.3% water was estimated lost by evaporation for maize grown on plots covered with plastic mulch. We developed a regression equation between shoot dry matter and transpiration amounts from plastic sheet mulched plots to estimate water loss by E in non-mulched and wheat straw mulched plots. Results showed that non-mulched plots lost 30.2% and wheat straw mulched plots lost 24.5% of the water received during the maize-growing season to E.
•Straw mulching (SM) and straw burying (SB) increase crop yields and soil nutrient contents.•SB is more conducive to increasing soil organic carbon, soil total nitrogen, and soil total potassium than ...SM.•SM is more conducive to increase soil available nitrogen, soil available phosphorus, and soil available potassium than SB.•SM performed better than SB in arid regions.•SB performed better than SM where mean annual precipitation is >800 mm.
Straw returning is an important measure for improving soil organic matter, biological activity, and nutrient availability. Straw mulching and straw burying are two methods for returning straw to the soil; however, there is little information to compare their benefits and limitations. This study assessed changes in soil nutrients induced by straw mulching and straw burying using a meta-analysis of straw returning data from 420 publications in China. The results showed that straw burying significantly increased soil organic carbon (SOC), soil total nitrogen (STN), soil total phosphorus (STP), soil total potassium (STK), soil available nitrogen (SAN), soil available phosphorus (SAP), and soil available potassium (SAK) in the surface soil (0–20 cm), with mean effect sizes of 0.126, 0.095, 0.056, 0.053, 0.118, 0.117, 0.138, respectively. Straw mulching increased SOC, STN, STP, SAN, SAP, and SAK in the surface soil, with mean effect sizes of 0.114, 0.079, 0.082, 0.125, 0.152, 0.150, respectively. Straw burying is more conducive to increasing SOC, STN, and STK, while straw mulching is more conducive to increasing SAN, SAP, and SAK. Straw mulching increased soil nutrient contents more than straw burying in areas with mean annual precipitation (MAP) <400 mm, while the reverse was true in areas with MAP> 800 mm. Straw mulching and straw burying both increased crop yield, with mean effect sizes of 0.100 and 0.101, respectively. Straw burying positively correlated with the effect size of yield, SOC, SAP, and SAK, while there were no significant relationships for straw mulching. Long-term straw burying and straw mulching was conducive to increasing crop yields, SOC, and STN. The benefits and limitations of straw mulching and burying on soil fertility and yield vary under different agronomic management, environmental, and edaphic factors.
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