Co-pyrolysis re-use of sludge and biomass waste: Development, kinetics, synergistic mechanism and industrialization

Pyrolysis is one of the substantial thermal conversion technologies for high-value reutilization of biomass and organic solid waste (OSW). Adding some typical OSWs to biomass pyrolysis can achieve directional regulation of target products that are considered potential alternatives to fossil energy. Understanding copyrolysis behaviors is vital for the optimizing pyrolysis process to minimize environmental pollution and efficiently utilize biomass and OSW. However, there is no overall review on the copyrolysis of biomass and various OSWs. This paper reviews and discusses recent advances in the copyrolysis mechanism, thermal–chemical processes of some typical OSWs and biomass, and effects of chemical compositions of raw materials and pyrolysis parameters on thermal–chemical conversion behaviors, synergistic effect, and copyrolysis product characteristics. Recent reports show that the synergistic effect in copyrolysis effectively improves the quality of bio-oil and biochar. Moreover, adding OSW to biomass pyrolysis can promote the secondary reaction of pyrolysis intermediates. The reaction mechanism and relative numerical simulation work of copyrolysis are summarized. Finally, the current challenges to energy- and environment-oriented conversion of biomass and OSW are discussed, and perspectives for further developing the copyrolysis process are highlighted. This paper provides valuable information for optimizing sustainable copyrolysis processes of OSW and biomass and improving the efficiency and selectivity of recycled OSW. 

Recent Advances and Perspectives of Copyrolysis of Biomass and Organic Solid Waste

Co-pyrolysis technology is an effective method to reduce heavy metal concentration in biochar produced from biosolids. In the current study, the effect of co-pyrolysis feedstock on product yield and properties was studied by mixing Biosolids (BS) with Wheat Straw (WS) and Canola Straw (CS) in a 3:1 mass ratio and carrying out thermal decomposition at 700 °C in a fluid bed reactor. This study found that the feedstock ash content and the volatile matter had a significant effect on biochar, oil, and gas yields from co-pyrolysis. The results also indicated that the addition of WS and CS feedstock notably reduced As, Cd, Cr, Cu, Ni, Pb, Se, and Zn concentrations in the biochar, due to the net effect of dilution and synergistic effects. BS-WS and BS-CS co-pyrolysis reduced Cu concentration in biochar by 61.6% and 63.3%, respectively, and Zn concentration by 66.4% and 64.4%, respectively. Lignocellulosic biomass addition also reduced biochar yield and improved C, H, and N content, along with the calorific value and the thermal stability of biochar. C content was increased by 36.9% in BS: WS biochar and 43.3% in BS: CS biochar compared to solely biosolids’ biochar. The calorific value of biochar was increased by 43.5% and 52.9% in BS-WS biochar and BS-CS biochar compared to biosolids’ biochar. During co-pyrolysis, CS addition produced oil with the lowest mole percentage of nitrogenated compounds. However, the addition of WS and CS increased co-pyrolysis oil acidity. Biosolids co-pyrolysis with WS and CS also increased the gas yield and the heating value compared to biosolids pyrolysis. Furthermore, the synergistic effect between biosolids and co-feedstocks resulted in increased gas yields and decreased oil and biochar yields. 

Co-pyrolysis of biosolids with lignocellulosic biomass: Effect of feedstock on product yield and composition

The development of ecological restoration projects is unsatisfactory, and soil erosion is still a problem in ecologically restored areas. Traditional soil erosion studies are mostly based on satellite remote sensing data and traditional soil erosion models, which cannot accurately characterize the soil erosion conditions in ecological restoration areas (mainly plantation forests). This paper uses high-resolution unmanned aerial vehicle (UAV) images as the base data, which could improve the accuracy of the study. Considering that traditional soil erosion models cannot accurately express the complex relationships between erosion factors, this paper applies convolutional neural network (CNN) models to identify the soil erosion intensity in ecological restoration areas, which can solve the problem of nonlinear mapping of soil erosion. In this study area, compared with the traditional method, the accuracy of soil erosion identification by applying the CNN model improved by 25.57%, which is better than baseline methods. In addition, based on research results, this paper analyses the relationship between land use type, vegetation cover, and slope and soil erosion. This study makes five recommendations for the prevention and control of soil erosion in the ecological restoration area, which provides a scientific basis and decision reference for subsequent ecological restoration decisions.

https://www.mdpi.com/1660-4601/20/3/2513/pdf?version=1675154455

Applying Convolutional Neural Network to Predict Soil Erosion: A Case Study of Coastal Areas

Effect of mineral additives on pyrolytic characteristics and heavy metal behavior during co-pyrolysis of industrial sludge and hyperaccumulator plant

Co-pyrolysis with biomass is a promising solution to obtain high-quality products for sewage sludge (SS) treatment. In the present study, a thermogravimetric analyzer (TGA) and fixed bed reactor were used to investigate the synergistic effect and bio-oil characteristics during co-pyrolysis of SS and pinewood sawdust (WS). The results show a significant interaction between SS and WS, and the most apparent synergistic effect appears at the WS proportion of 50 wt. %. Co-pyrolysis of SS with WS promotes the generation of bio-oil while reducing gas formation, but less effect can be observed on the char yield. In the case of 50 wt. % WS addition, the maximum bio-oil yield (40.54%) was obtained at 550 °C, which was increased by 13.65% relative to the calculated value. Moreover, at 550 °C, the production of acids, sugars, and nitrogen-containing compounds during co-pyrolysis decreased by 47.68%, 54.34%, and 71.89%, respectively. In the meanwhile, the phenolic compounds are 29.92% higher than the theoretical value. Besides, high temperatures can decrease acids, alcohols, ketones, esters, and sugars and increase hydrocarbon production during co-pyrolysis. The above results indicated that the addition of WS can effectively improve the quality of bio-oil from SS pyrolysis.

Co-pyrolysis of sewage sludge and pinewood sawdust: the synergistic effect and bio-oil characteristics

In the black soil area, where soil erosion is severe and the soil is in urgent need of ecological restoration, providing reasonable and practical measures to prevent soil erosion and restore the soil is an urgent issue at present. In this study, nine runoff plots were deployed in Bin County, the core area of soil erosion control, to monitor runoff and soil loss long-term, simulated by the erosion potential method (EPM) for comparison. Studies have shown that soil erosion is strongly influenced by soil conservation measures, land use, and vegetation cover. In contrast, slope, pre-soil moisture content, and soil crusting due to rainfall can affect erosion in a single rainfall event. The most severe soil erosion was in bare land, up to 1093.58 t km−2 a−1, followed by longitudinal ridge tillage land (751.88 t km−2 a−1) and cross ridge tillage land (31.58 t km−2 a−1). The shrublands and mixed forests planted for ecological restoration experienced almost no erosion. The soil loss rate of the cross ridge tillage and ecological restoration plots was much lower than the allowable soil loss rate (200 t km−2 a−1). Under erosive storms, longitudinal ridge tillage can produce soil loss rates that far exceed those of bare ground. The change from longitudinal ridge tillage to cross ridge tillage on gentle slopes can effectively prevent soil erosion in the study area. The vegetation restoration measures of planting shrubs such as Amorpha fruticosa Linn. are incredibly effective in the ecological restoration of wastelands in black soil areas. For the black soil area after the retreat, the vertical structure of vegetation can be improved by planting shrubs at the bottom, thus achieving a good restoration effect.

/pdf/study-on-the-characteristics-of-soil-erosion-in-the-black-2oc59vq7.pdf

Study on the Characteristics of Soil Erosion in the Black Soil Area of Northeast China under Natural Rainfall Conditions: The Case of Sunjiagou Small Watershed

Straw mulching has been widely used to conserve soil water and enhance soil fertility in dryland cropping systems. However, the lack of soil nutrient availability due to the immobilization with straw mulch decomposition would result in a decrease in crop yield and harvest index. Based on a 9-yr straw mulching field experiment, we evaluated the effect of late topdressing in 2 years on crop yield under a winter wheat monoculture system in the Loess Plateau of China. Three treatments were included as straw mulching at rates of 9000 (HSM) and 4500 kg ha–1 (LSM) during growing season and control without mulching (CK) from 2008 to 2019. Topdressing as urea was added to each plot at wheat tillering from 2017 to 2019.Across two years, straw mulching significantly increased soil water storage at most growing stages. Compared with CK, straw mulching promoted wheat growth (tiller number and plant number) but decreased grain yield and harvest index significantly. Soil mineral N contents in later wheat growing stages and net photosynthetic rate, transpiration rate of wheat flag leaf and leaf water use efficiency during filling stage decreased with HSM and LSM when compared with CK. However, late topdressing significantly increased wheat grain yield in both years. Generally, additional application of N fertilizer in the late growing stage could alleviate the yield decrease by straw mulching and should be considered for sustainable crop production in the Loess Plateau of China. This article is protected by copyright. All rights reserved 

Late topdressing can sustain wheat grain yield under straw mulching in the Loess Plateau of China

A field experiment was carried out to study the effects of winter cover cropping on soil greenhouse gas emissions in dryland maize. Four cover crop treatments, namely oat, lentil, a mixture of oat and lentil, and no cover crops (CK), were included during the winter fallow period. Greenhouse gas emission fluxes from soil were measured using the static chamber-gas chromatograph technique. The results showed that:both soil CO2 and N2O were emitted, but the soil acted as a sink for CH4. Compared with the that in CK, oat and lentil had no effect on the cumulative amount of soil CO2 emissions during the winter fallow period and increased the cumulative amount of soil CO2 emissions by 7.77% and 25.7% (P<0.05) in the spring maize growing period, respectively; the mixture increased the cumulative amount of soil CO2 emissions by 19.1% and 14.5% (P<0.05) during the winter fallow and spring maize growing periods. In the winter fallow and spring maize periods, compared with that in CK, oat declined the cumulative amount of soil N2O emissions by 11.6% and 14.7% (P<0.05), and lentil increased the cumulative amount of soil N2O emissions by 31.9% and 14.9% (P<0.05), respectively. Compared to that in the CK, the mixture declined the cumulative amount of soil N2O emissions by 19.2% (P<0.05) in the winter fallow period but had no effect in the spring maize period. Compared with the CK, oat, lentil, and their mixture resulted in a declined cumulative amount of soil CH4 uptake by 37.9%, 23.6%, and 29.6% (P<0.05) in the winter fallow period and by 19.4%, 33.5%, and 31.5% (P<0.05) in the spring maize growing period, respectively. Compared with the CK, oat had no effect on global warming potential (GWP), maize yield, and greenhouse gas intensity (GHGI). Lentil and the mixture increased GWP, and lentil showed a greater increase in GWP than that of the mixture. Compared with the CK, lentil and the mixture increased maize yield by 20.3% and 15.4% (P<0.05), respectively, and had no effect on GHGI. The findings from this study show that the lentil and oat mixture can significantly increase maize yield and decrease GHGI.

[Effect of Winter Cover Cropping on Soil Greenhouse Gas Emissions in a Dryland Spring Maize Field on the Loess Plateau of China].

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Papers

Co-pyrolysis of sewage sludge and pinewood sawdust: the synergistic effect and bio-oil characteristics

Study on the Characteristics of Soil Erosion in the Black Soil Area of Northeast China under Natural Rainfall Conditions: The Case of Sunjiagou Small Watershed

Late topdressing can sustain wheat grain yield under straw mulching in the Loess Plateau of China

[Effect of Winter Cover Cropping on Soil Greenhouse Gas Emissions in a Dryland Spring Maize Field on the Loess Plateau of China].