Effects of different pretreatments on compression molding of wheat straw and mechanism analysis

In-situ registration subtraction image segmentation algorithm for spatiotemporal visualization of copper adsorption onto corn stalk-derived pellet biochar by micro-computed tomography

The non-homogeneous structure and high-density ash composition of biochar matrix pose significant challenges in characterizing the dynamic changes of heavy metal adsorption onto biochar with micro-computed tomography (Micro-CT). A novel in-situ registration subtraction image segmentation method (IRS) was developed to enhance micro-CT characterization accuracy. The kinetics of Cu(II) adsorption onto pellet biochar derived from corn stalks were tested. Respectively, the IRS and traditional K-means algorithms were used for image segmentation to the in-situ three-dimensional (3D) visual characterization of the Cu(II) adsorption onto biochar. The results indicated that the IRS algorithm reduced interference from high-density biochar composition, and thus achieved more precise results (R2 = 0.95) than that of K-means (R2 = 0.72). The visualized dynamic migration of Cu(II) from surface adsorption to intraparticle diffusion reflexed the complex mechanism of heavy metal adsorption. The developed Micro-CT method with high generalizability has great potential for studying the process and mechanism of biochar heavy metal adsorption.

A comprehensive review of the production, adoption and sustained use of biomass pellets in Ghana

Ghana's Renewable Energy Master Plan of 2019 includes the production and use of biomass pellets. However, pellets have neither been developed commercially nor included in Ghana's energy mix. This paper reviewed the prospect of production, adoption and sustained use of pellets in Ghana. Besides having abundant biomass resources, Ghana has high market demand and relevant policies for pellet development. The production of pellets can significantly replace traditional household biomass demand and improve environmental and health quality. However, the production and use of pellets are limited due to technical, financial, social and policy issues. Our estimates show that 3% of the annual national average household income will be spent on pellet demand for cooking, with the highest burden on rural households in Ghana. Practical measures are required since the cost of pellets and gasifier stoves may limit pellet adoption and use in Ghana. Based on study findings, it is recommended that the government of Ghana establishes a robust supply chain and provides infrastructure for pellet production and use. Existing renewable energy policies should be reviewed to remove ambiguities, attract investment, and build capacity in the renewable energy sector. Apart from raising public awareness of the benefits of pellets use, the government of Ghana should ensure that continuous and thorough impact assessments are undertaken to assess the implications of pellet production and use. This review will inform policymaking on achieving sustainable production, adoption and use of pellets and assess Ghana's contribution to achieving the United Nations' sustainable development goals.

Effects and mechanism of pyrolysis temperature on physicochemical properties of corn stalk pellet biochar based on combined characterization approach of microcomputed tomography and chemical analysis

To further explain effects of pyrolysis temperature on physicochemical properties of corn stalk pellet biochar from a new perspective, various lab physicochemical analysis methods combining microcomputed tomography were used to characterize biochar in this study. The results showed that at pyrolysis temperatures from 300 °C to 800 °C, yield of biochar decreased logarithmically with increasing pyrolysis temperature (T); changes of proximate and elemental compositions all showed significant differences, but the change rules were not consistent; high temperature pyrolysis biochar had high stability, high hardness and was convenient for storage and transportation; the proportions of hydroxyl group and amino group were highest in BC800 and BC600, respectively, contributing to the adsorption and removal of pollutants; BC400 had the best combustion performance; X-ray mean attenuation coefficient (XMAC) showed the following correlations, namely, XMAC = 0.003*ln(T-285.329) + 0.011 (R² = 0.904) and XMAC = -0.031*(VM/100) + 0.021*(Ash/100) + 0.027 (R² = 0.915). Above results provide important basic data support for development of corn stalk pellet biochar.

Fuel Characteristics of Briquettes Manufactured by Natural Stacking Bamboo/Chinese Fir Mixtures

Bamboo wastes were naturally stacked for 1 month and were uniformly mixed with Chinese fir. Briquettes were manufactured by a briquette extruder at different process temperatures and mixing ratios. The physical, mechanical, pyrolysis, and combustion characteristics of briquettes were determined. The results showed that the mixing ratios and process temperature had a significant impact on the fuel properties of briquettes. The optimum briquettes were manufactured by 70% bamboo/30% Chinese fir blends at a process temperature of 520 °C. The fuel properties of optimum briquettes met the standard requirement of LY/T 2552-2015 and GB/T 28669-2012. The lower heating rate at the primary pyrolysis stage increased the yield of charcoal during the carbonization process of briquettes. The combustion process of briquettes added a char combustion stage, compared with the pyrolysis process. There were no synergistic interactions of bamboo and Chinese fir during pyrolysis and combustion process. The results of this research are helpful to develop large-scale production of bamboo briquettes or charcoal.

The composition characteristics of different crop straw types and their multivariate analysis and comparison

The heterogeneity and complex composition of crop straw are some of the main obstacles to its scientific and efficient industrial utilization. To thoroughly reveal and identify the composition of different crop straw types and their latent attributes, in this study, 784 straw samples of rice, wheat, corn, rape and cotton were collected. Based on the large sample size, 18 composition characteristics, including chemical composition, proximate composition, ultimate composition, and heating values, were adopted to determine the profiles of the crop straw composition characteristics. Correlation analysis and 7 different types of multivariate analysis were applied and compared. The results indicated that among the 18 characteristics, hemicellulose, water-soluble carbohydrates, crude proteins, phosphorus, fixed carbon, hydrogen, nitrogen, and sulfur had non-normal distributions. Spearman method was a more suitable correlation analysis approach for the crop straw characteristics than Pearson method. The results of the different multivariate analysis methods were reflected in the different classification attributes of water-soluble carbohydrates, phosphorus, hydrogen and sulfur. Non-parametric principal component analysis and non-parametric exploratory factor analysis provided consistent results. The characteristics could be divided into 4 categories of intrinsic associated attributes, namely, (1) lignin, volatile matter, fixed carbon, carbon, hydrogen, higher heating value, and lower heating value; (2) potassium, ash, and sulfur; (3) cellulose, hemicellulose, moisture, and oxygen; and (4) water-soluble carbohydrates, crude proteins, phosphorus, and nitrogen, which exhibited combustion positive, combustion negative, biochemical conversion, and nutritional property, respectively. The study results provide data and methodology support for the development of crop straw utilization strategies.