生物炭主要类型、理化性质及其研究展望

The main types of biochar and their properties and expectative researches

【目的】生物炭作为工农业生产副产品低碳利用的有效手段,其改善土壤及提高作物品质的有益功效已被逐步认识,但对其研究报道分散且差异较大。对已有研究进行梳理总结,可为生物炭生产施用以及形成有效的产业链提供科学依据。【主要进展】1)生物炭全碳含量在30%~90%之间,平均64%。生物炭碳含量由大到小来源依次是木质、秸秆、壳类、粪污和污泥。秸秆类生物炭碳含量大多为40%~80%,木质类生物炭在60%~85%。生物炭灰分含量在0~40%之间变动,平均15.52%。灰分含量由大到小依次是污泥、粪污、秸秆、壳类和木质。秸秆生物炭灰分含量主要在20%~35%之间,较少为15%;木质炭灰分主要在0~10%范围内。生物炭碳含量和灰分含量相关系数为–0.77。裂解温度与生物炭碳灰组分呈正相关,相关系数分别为0.17和0.28。施入生物炭可以改善土壤状况,生物炭灰分通常对养分贫瘠土壤及沙质土壤的一些养分补充作用较明显。2)生物炭比表面积绝大多数在0~520 m2/g之间,平均124.83 m2/g,壳类、秸秆、木质、粪污和污泥生物炭比表面积逐渐降低。秸秆炭比表面积集中在0~200 m2/g以内,木质炭比表面积集中在0~100 m2/g以内。制备温度与比表面积的相关系数为0.48。生物炭的孔隙结构能降低土壤容重、降低土壤密度,能较好地去除溶液和钝化土壤中的重金属。3)生物炭p H值范围在5~12,平均为9.15。秸秆、污泥、粪污、木质、壳类生物炭p H值中值逐渐降低。秸秆生物炭p H值多集中在8~11范围内,木质生物炭p H相对一致。生物炭的CEC从0到500 cmol/kg都有分布,平均为71.91 cmol/kg。秸秆类生物炭CEC值大多集中在0~100 cmol/kg范围内,木质生物炭则在5~10与15~25 cmol/kg范围内均有一定数量的分布。裂解温度与p H值和CEC的相关系数为0.58和0.30。生物炭施入土壤后可消耗土壤质子,提高酸性土壤p H值,提高酸性土壤一些养分的有效性;其巨大的表面积还可提高对阳离子的吸附,提高土壤保肥能力。4)生物炭的裂解温度大都集中在200~800℃之间,偶有达到1000℃的裂解温度。【建议和展望】目前,全世界范围内对生物炭的生产和使用还处于就近和来源方便的初级阶段,影响着生物炭功能和效益的最大化。应从以下几个方面加强研究和应用试验:首先,系统研究生物炭制造参数对理化性状的影响,研究不同原料生物炭的作用机理差异及其针对性,建立生物炭理化性质参数数据库;其次,加强应用研究,根据土壤理化性状和改良目标选择适宜的生物炭类型,根据对作物经济性状的要求,研究选择适宜的生物炭类型,实现生物炭功效的最大利用。加强不同原料的选配和组合研究,改良生物炭产品的目标性状,形成系列化产品。

【Objectives】Biochar production and application, as an effective low carbon use of by-products of industrial and agricultural production, have been widely recognized by researchers for their effects in soil improvement and crop production. However, the reports on the effects of biochar are discrepant greatly as the different feedstock and parameters in the production process of biochar. Summering previous researches willprovide academic base for the effective use and production of biochar.【Major advances】1） The range of the carbon contents in biochar is 30%-90% with an average of 63.84%, and the carbon contents from different raw materials are in order： wood straw shell manure sludge. The carbon contents of straw biochar are mainly in 40%-80%, and those of wood biochar are mainly in 60%-85%. The range of biochar ash is 0-40%with an average of 15.52%, and the contents are in order： sludge manure straw shell wood. The ash contents of straw biochar are generally in 20%-35%, and those of wood biochar are mainly in 0-10%. The correlation coefficient between the carbon contents and the ash contents is –0.77, the correlation coefficients between the pyrolysis temperature and the carbon contents and the ash contents are 0.17 and 0.28 respectively.Adding biochar could improve soil properties. Biochar ash content usually plays a significant role on nutrient supplement of poor and sandy soil. 2） The range of specific surface area is 0-520 m^2/g with an average of124.83 m^2/g, and the contents are in order： shell straw wood manure sludge. The specific surface area of straw biochar is generally in 0-200 m2/g and that of wood biochar is generally in 0-100 m2/g. The correlation coefficient between the pyrolysis temperature and the specific surface area is 0.48. The pore structure of biochar could reduce soil bulk density, soil density, and remove heavy metals in solution and soils. 3） The p H of biochar is in range of 5-12 with an average of 9.15, and in order： straw sludge manure wood shell.p H of straw biochar is generally in 8–11 and p H of wood biochar has an uniform distribution. The range of CEC is 0-500 cmol/kg with an average of 71.91 cmol/kg. CEC of straw biochar is generally in 0-100 cmol/kg and CEC of wood biochar is generally in 5-10 and 15-25 cmol/kg. The correlation coefficients between the pyrolysis temperature and p H and CEC are respectively 0.58 and 0.30. The biochar could reduce soil proton,improve p H and nutrient availability of acidic soil; biochar also gets the ability of ion exchange adsorption,improves the cation and anion exchange capacity, increase ability to protect fertilizer. 4） All the biochar were prepared at the paralysis temperature of 200℃-800℃, occasionally at 1000℃.【Suggestions and expectations】The production and application of biochar are still in the initial stage in the world. Some researches should be considered in the future. Firstly, the differences in beneficial effects of biochar related manufacture parameters and raw materials should be systemically studied and a database should be setup accordingly; the suitable type of biochar should be made clear according to the expected target and the soil properties, to achieve the highest profit of biochar. More work is also needed for the selection and combination of biochar from different material sources, so to produce multiple functional products to meet the requirement of practical use.