| With the rapid growth of food demand,intensive agriculture has greatly increased the number of chemical fertilizers,while consuming soil fertility,especially soil organic matter.Soil quality had declined significantly and had a negative effect on crop growth and health.Numerous agricultural wastes are generating gradually,but how to industrialize and recycle those bio-wastes is an urgent problem in agricultural management.Until now,many bio-wastes utilization technologies have come out,including solid molding,biomass direct combustion,biomass liquefaction,gasification/thermal cracking,and aerobic/anaerobic biological fermentation technology.Meanwhile,biomass pyrolysis technology is increasingly applied and promoted because biochar can improve soil quality and enhance crop productivity.In addition,straw pyrolysis technology can contribute to greenhouse gas emission and always have additional economic benefits.Generally,biochar soil amendment can improve soil structure,enhance soil fertility and increase crop yields.Bio-wastes pyrolysis technology can establish a full ecological cycling from agriculture to environmental and economic benefits by combining crop waste management,biomass fuel production and biochar agricultural application.Biochar is a new type of agricultural resource for soil improvement,fertilizer substitution and environmental governance,it can serve the development of green agriculture in the future.However,there are many types of bio-wastes in agriculture and food supply chain management,and the relationship between pyrolysis products and its raw material sources has not yet been integrated.In this study,we select 26kinds of bio-wastes in the food production supply chain,and pyrolyzed them under same condition(a heating rate of 5℃min-1 was adopted up to 450℃and maintained for 1 h before cooling to ambient temperature).Besides,we evaluate the application potential of those pyrolysis.In this study,a total of 26 bio-waste raw materials were selected from three major sources:five kinds of primary biomass,including walnut peel,tobacco stem powder,rice husk powder,peanut shell,and coconut dregs;seven kinds of secondary biomass,including cattle dung,sheep dung,rabbit dung,vermicompost,rice husk-cow dung,silkworm excrement,bone powder;fourteen kinds of processed biomass,including straw mushroom residue,eryngii mushroom residue,enoki mushroom residue,bisporus mushroom residue,bagasse,black tea residue,cassava residue,Chinese materia medica residue,rice husk ash,xylose residue,corn residue,sorghum liquor residue,coffee residue,and vinegar residue.The raw materials were pyrolyzed under the same conditions,and the product characteristics and nutrient recovery of different sources of bio-wastes were analyzed,and agricultural benefit the biochars was compared with the Chinese cabbage pot experiment.The main findings are as follows:（1）Biochar properties were varied with bio-wastes types after carbonization:On average,the p H（9.1）and CEC(73 cmol kg-1)of biochar were in small variation（CV was～10%）;the organic carbon content(306 g kg-1),total nitrogen content(16 g kg-1),moisture（5%）,ash（38%）of biochars were in 60-70%variation,while EC(2 m S cm-1)value,the contents of soluble organic carbon(7 g kg-1),phosphorus(11 g kg-1)and potassium(12 g kg-1)varied more than 90%.For primary bio-waste,the conductivity(3 m S cm-1),cation exchange capacity(225 cmol kg-1),soluble organic matter(22 g kg-1)and potassium content(23 g kg-1)of biochar were the highest;pot experiment showed that it had the best effect on reducing nitrate accumulation in Chinese cabbage（-22%）.For secondary bio-waste,the pyrolysis solid yield was the highest（56%）,and the p H value（9.4）,ash content（51%）and phosphorus content(15 g kg-1)of the products were higher than other biochar（2）The yield of biochar was among 34-84%,the recovery of organic carbon was 21-80%,and the recovery of nitrogen was 21-67%.The comprehensive yield showed that:bone powder carbon,bagasse residue biochar,agaricus bisporus residue biochar,rice husk ash biochar,vermicompost biochar,silkworm excrement biochar and corn residue biochar were more than 50%.These wastes can be pyrolyzed and the process was an effective method for efficient utilization of bio-wastes.（3）The effects of biochar on soil properties were as follows:applying biochar could improve soil p H（0.34 units on average）,EC value（24%）,soil organic carbon（54%）,total nitrogen（25%）,available phosphorus（356%）and available potassium（52%）.The results of comprehensive soil index calculation showed that the average of soil fertility increase 105%under biochar treatment.The results showed that the EC value and P content of biochar played an important role in improving soil p H.The p H value,EC value and K content of biochar played an important role in improving soil fertility.Among these biochars,silkworm excrement biochar,bone powder biochar and tobacco stem powder biochar improved soil fertility efficiency by more than 150%.These biochars can be applied to the soil to improve the soil fertility greatly.Therefore,these wastes can be used as efficient materials for soil amendment,and their products can be directly or indirectly made into fertilizer and applied to the soil to solve the soil fertility problem effectively.（4）The effects of biochar on crop productivity and quality were as follows:applying biochar could improve the yield of pakchoi（103%）,vitamin C content（63%）,soluble sugar content（5%）,soluble protein content（23%）,and reduce nitrate content（-10%）;applying biochar could improve the comprehensive quality benefit of crops by about 100%.Combined with the comprehensive analysis of crop yield and quality,biochar can improve the comprehensive benefit of plant（～100%）.The statistical analysis results showed that applying biochar could reduce the nitrate content in crops,which was mainly related to the high K content and EC value of biochar.Among these biochars,silkworm excrement biochar,rice husk and cow dung biochar,bone powder biochar,agaricus bisporus residue biochar,rabbit dung biochar,sheep dung biochar and corn residue biochar can improve the comprehensive benefits of plant by more than 150%.The product of these wastes can be used as high-quality crop growth promoting fertilizers for agricultural production to improve the yield and quality of crops.（5）The comprehensive benefits of pyrolysis cycle and agricultural application results showed:silkworm excrement,rice husk,cow dung,bone powder,agaricus bisporus residue,rabbit dung,sheep dung and corn residue belong to the dominant waste for pyrolysis utilization.It would be meaningful to pyrolyze these wastes,set up an ecological industry chain with biomass pyrolysis cycle,soil fertility improvement and efficient crop production,and to suit a green circular economy agriculture. |
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