Biochar quality can be improved by the choice of waste feedstock, pyrolysis temperature, additives, and other factors. As an example, nitrogen-doped biochars can be used not only for pollutant removal from wastewaters, but also as nitrogen nutrient carriers. Nitrogen-doped biochars can be made through pyrolysis of nitrogen-rich biomass obtained by either using sources high in nitrogen or by supplementation of biomass with external nitrogen sources. The authors of this paper list several nitrogen-rich sources of biomass (including food wastes (bean dregs, watermelon rind, banana peels), Torula yeast (Candida utilis), municipal sewage sludge, human hair, iris, water hyacinth, tea, cat tails (Typha angustifolia), green algae, Spirulina, shrimp shells, and chitosan). Biomass low in nitrogen (such as agar, corn straw, bagasse, cotton stalks, bamboo chips, bagasse, cellulose, anaerobic digested fiber) can be treated with external nitrogen sources such as ammonia gas, ammonium hydroxide, urea, ammonium chloride, or melamine. The use of novel treatments such as surface oxygen modification and post-treatment to add nitrogen sources to the biochar and the temperature and time of pyrolysis are important for determining the effectiveness of the biochar as a slow-release fertilizer. This N-doping process can be an in-situ approach to processing biomass wastes. Another type of doped biochar can be made using sewage sludge as feedstock by treatment with potassium acetate prior to pyrolysis, resulting in potassium-doped biochar with better P availability as a novel PK fertilizer. A recent study by Kassem, et al. demonstrates use of cellulose and montmorillonite-modified biochar in nanocomposite film coatings on superphosphate to produce slowrelease phosphorus granules that also assist with water retention in soil. Montmorillonite increased the efficiency of biochar production, and use of cellulosic materials as coating modifiers and in biochar production provides new uses for these materials in making sustainable fertilizer formulations.