ABSTRACT
Biochars, being derived from a variety of biological feedstocks that have been thermally degraded under a range of conditions (Chapter 8), exhibit a correspondingly large range in composition and chemistry. Due, in part, to the complex set of chemical reactions that occur during thermal processing, a large degree of chemical heterogeneity extends to the microscopic scale, even within a single biochar. Thus, in the strictest sense, each biochar made with a particular feedstock and process combination presents a unique mixture of phases and microenvironments that gives rise to a unique set of chemical properties. In some respects, the chemical
complexity of biochars rivals that of incipient soils. In this chapter we focus on the chemical complexity of biochar as manifested primarily at a microscopic and molecular scale.We start by describing the biochar-formation process and how this influences the composition and nature of the solid phases, entrained oils and their organization at the microscopic level.We then proceed to discuss the range of surface chemistries exhibited by biochars in terms of functional groups and electrochemical properties.We conclude with a discussion of the influence of these properties on the sorption of aqueous species at biochar surfaces.
