A large specific surface area is one of the structural characteristics which makes biochar a promising material for novel applications in agriculture and environmental management. However, the high complexity and heterogeneity of biochar’s physical and chemical structure can render routine surface area measurements unreliable. In this study, N₂ and CO₂ characterization of twelve biochars from three feedstocks with production temperatures ranging from 400 °C to 900 °C were used to evaluate materials with varying structural properties. The results indicate that the frequently reported peak in the surface area of biochars around 650 °C is an artefact of N₂ measurements and not confirmed by CO₂ analysis. Contradicting results indicate an influence of the structural rigidity of biochar on N₂ measurements due to pore deformation in certain biochars. Pore non-specific calculation models like the Brunauer-Emmett-Teller method do not allow for adjustments to these changes. Instead, the use of a pore specific model and the exclusion of pores smaller than 1.47 nm was found to achieve more representative results. The proposed calculation was validated on an external dataset to highlight the applicability of the method. Our results provide novel insights for understanding the structural evolution of biochar related to production temperature.

大的比表面积是使生物炭成为农业和环境管理中新应用的有前途的材料的结构特征之一。然而，生物炭的物理和化学结构的高度复杂性和异质性会使常规的表面积测量不可靠。在这项研究中，使用来自三种原料的12种生物炭的N ₂和CO ₂表征（生产温度范围为400°C至900°C）来评估具有不同结构特性的材料。结果表明，在650°C附近经常报告的生物炭表面积峰是N ₂测量的伪影，而未由CO ₂证实分析。相反的结果表明，由于某些生物炭中的孔变形，生物炭的结构刚度对N ₂测量有影响。诸如Brunauer-Emmett-Teller方法之类的非特定孔径计算模型不允许对这些更改进行调整。相反，发现使用孔特异性模型和排除小于1.47 nm的孔可实现更具代表性的结果。拟议的计算在外部数据集上得到了验证，以突出该方法的适用性。我们的结果为理解与生产温度有关的生物炭的结构演变提供了新颖的见解。