Abstract

Biochar is a solid material obtained by the decomposition of organic material under oxygen-limited conditions (pyrolysis) and at a temperature ranging from 350°Cto 900°C (http://www.biochar-international.org/). As compared with raw biomass, biochar contains a high amount of carbon (C), in addition to being composed of other elements such as hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S). This material is also characterized by its high stability and surface properties, such as large surface area, porous structure, and surface functional groups. These properties are variable and depend on the source of the raw material (i.e., biomass), and on production conditions. Biochar has various uses, including the amendment and fertilization of soil; as a reducer of greenhouse gas emissions; as an adsorbent of organic and inorganic pollutants in the air, soil, and water; and as an energy source, among other applications. The use of biochar in the soil allows fixing carbon, thereby improving soil quality by neutralizing acidic soil, promoting cationic exchange capacity, and increasing the activities of microorganisms. When biochar is applied, the basic cations of biochar are discharged into the soil, with aluminum (Al) and H+ being replaced. This consequently improves the cationic exchange capacity of the soil (Cha et al. 2016). In addition, worth mentioning, biochar has high N, phosphorus (P), calcium (Ca), and potassium (K) concentrations, which directly provide nutrients to the soil or associated microorganisms. Biochar originating from algal biomass is efficient for the adsorption of heavy metals and organic matter from aqueous solutions (Cha et al. 2016). Furthermore, seaweed-derived biochar has higher nutrient (N, P) contents and exchanged trace elements (Ca, Mg, and K) compared with many terrestrial biomass types (Bird et al. 2011); therefore, biochar from seaweeds could be adequate for use as a soil amender. Considering the given context, the objective of this chapter is to shed light on the potential uses of biochar generated from algae and to describe an efficient method of production from the kelp Macrocystis pyrifera.