BIOCHAR - Fertilizers: Components, Uses in Agriculture and Environmental Impacts - page 98

(modified from Li et al., 2013).

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Figure 1. Solid-state C NMR spectra of rice straw and rice bran at various charring temperatures.

Unlike graphite sheets which orient themselves into compact sheet structures at high
temperatures, heterogeneous high-oxygen rich materials (>5% oxygen by mass) such as
biochar produced at lower temperatures (ca. <700 °C) tend to develop cross-link structures
that maintain the random orientation of the developed graphene/graphite like short-order
crystalline, withholding the voids that contribute to its porosity. Yet, development of porosity
in biochar follows a bell-shape pattern, increasing as temperature increases up to a critical
temperature range from which porosity declines, at values which are feedstock dependent
(Rutherford et al., 2004). Rutherford et al. (2004) noted that microporosity development
coincided with loss in total mass of aromatic carbon and suggested that microporosity