Effects of pretreatments on thickened waste activated sludge and rice straw co-digestion: Experimental and modeling study.

In order to maximize the biogas production from thickened waste activated sludge (TWAS), co-digestion of TWAS and rice straw (RS) was studied and the application of thermal/thermo-alkaline and NaOH/H2O2 to TWAS and RS, respectively, was evaluated. The batch experiments were conducted at three different TWAS/RS (volume basis) ratios of 1:3, 1:1 and 3:1, respectively. Furthermore, the modified Gompertz model was introduced to predict the biogas yield and evaluate the kinetic parameters. The highest biogas production (409.2 L/kg VSadded) was achieved from co-digestion of TWASthermo-alkaline and RSNaOH at mixing ratio of 1:1, which is greater by 42.2% and 5.9% than that of digesting TWASthermo-alkaline, and RSNaOH alone, respectively. The highest VS removal rate was obtained from the co-digestion of TWASthermo-alkaline and RSNaOH at mixing ratio of 1:3, which is greater by 55.8% and 14.0% than those of mono-digestion. The modified Gompertz model (R(2): 0.993-0.998 and 0.993-0.999 for mono- and co-digestions, respectively) showed a good fit to the experimental results and the estimated parameters indicating that the pretreatments and co-digestion of substrates markedly improved the biogas production rate.

Recent developments in biochar as an effective tool for agricultural soil management: a review.

In recent years biochar has been demonstrated to be a useful amendment to sequester carbon and reduce greenhouse gas emission from the soil to the atmosphere. Hence it can help to mitigate global environment change. Some studies have shown that biochar addition to agricultural soils increases crop production. The mechanisms involved are: increased soil aeration and water-holding capacity, enhanced microbial activity and plant nutrient status in soil, and alteration of some important soil chemical properties. This review provides an in-depth consideration of the production, characterization and agricultural use of different biochars. Biochar is a complex organic material and its characteristics vary with production conditions and the feedstock used. The agronomic benefits of biochar solely depend upon the use of particular types of biochar with proper field application rate under appropriate soil types and conditions. © 2016 Society of Chemical Industry.

Fast pyrolysis biochar from sawdust improves the quality of desert soils and enhances plant growth.

BACKGROUND: Biochar has been mostly used in conventional arable soils for improving soil fertility. This study investigated the effect of biochars of different temperatures on plant growth and desert soil properties. Biochars of different temperatures (i.e. 400, 500, 600, 700, and 800 °C) were mixed in the soil with 5% by mass, and the treatments were designated as T-400, T-500, T-600, T-700 and T-800, respectively. Sorghum was used as a test crop, and the effect of biochar on plant height, yield and soil properties was evaluated. RESULTS: Sorghum yield increased by 19% and 32% under T-400 and T-700, respectively, above the control. Biochar reduced depth-wise moisture depletion in soil columns and hence improved soil water-holding capacity by 14% and 57% under T-400 and T-700, respectively. Soil hydraulic conductivity was reduced by 15% and 42%, and moisture-retention capacity was improved by 16% and 59%. Hence, sorghum net water-use efficiency increased by 52% and 74% in T-400 and T-700, respectively. Biochar also improved soil total carbon, cation exchange capacity and plant nutrient content. CONCLUSION: The addition of fast pyrolysis biochar made from pine sawdust improved the quality of Kubuqi Desert soil and enhanced plant growth. Hence, it can be used for desert modification.

Characteristics and kinetic studies of Hydrilla verticillata pyrolysis via thermogravimetric analysis.

The pyrolysis characteristics and kinetic of Hydrilla verticillata (HV) have been investigated using non-isothermal thermogravimetric analysis. The results showed that the pyrolysis behavior of HV can be divided into two independent stages. The kinetics of Stage I was investigated using a distributed activation energy model (DAEM) with discrete 99 first-order reactions. Stage II was an independent stage which corresponds to the decomposition of calcium oxalate, whose kinetics was studied using iso-conversional method together with compensation effect and master-plots method. The activation energies ranged from 92.39 to 506.17 and 190.42 to 222.48 kJ/mol for the first and second stages respectively. Calculated data gave very good fit to the experimental data.

Characteristics and kinetic study on pyrolysis of five lignocellulosic biomass via thermogravimetric analysis.

Pyrolysis characteristics and kinetic of five lignocellulosic biomass pine wood sawdust, fern (Dicranopteris linearis) stem, wheat stalk, sugarcane bagasse and jute (Corchorus capsularis) stick were investigated using thermogravimetric analysis. The pyrolysis of five lignocellulosic biomass could be divided into three stages, which correspond to the pyrolysis of hemicellulose, cellulose and lignin, respectively. Single Gaussian activation energy distributions of each stage are 148.50-201.13 kJ/mol with standard deviations of 2.60-13.37 kJ/mol. The kinetic parameters of different stages were used as initial guess values for three-parallel-DAEM model calculation with good fitting quality and fast convergence rate. The mean activation energy ranges of hemicellulose, cellulose and lignin were 148.12-164.56 kJ/mol, 171.04-179.54 kJ/mol and 175.71-201.60 kJ/mol, with standard deviations of 3.91-9.89, 0.29-1.34 and 23.22-27.24 kJ/mol, respectively. The mass fractions of hemicellulose, cellulose and lignin in lignocellulosic biomass were respectively estimated as 0.12-0.22, 0.54-0.65 and 0.17-0.29.