To develop the most effective products from biochar, both the macroscopic and microscopic properties should be optimized for a desired task. Several options are available for custom tailoring biochar, including modification of production conditions, use of additives before or after pyrolysis, oxidative treatment and chemical grafting. The efficacy of any of these treatments is strongly dependent on both the chemical structure of the biochar as well as the physical structure.  While a variety of effective and well established methods are available to study the physical structures of char, the chemical structure remains somewhat elusive. In this study we have examined the application of several spectroscopic techniques, including FT-IR, Raman, XPS, and NMR to more completely describe the chemical structure of a thermoseries of cellulose chars. These studies have allowed in-depth analysis of carbon clustering and heteroatom inclusion, and have revealed a wide range of defects within the carbon matrix including non-hexagonal ring systems and internal ether structures. These structures will have a significant impact on both the adsorption properties and the oxidative behavior of the biochar. The modified characterization techniques presented provide the necessary chemical structure information required for more accurate predictions of the behavior of biochar in real systems, and may allow for more rapid tailoring of desired biochar properties.