In some variations, the invention provides a biocarbon pellet comprising: 35 wt % to 99 wt % of a biogenic reagent, wherein the biogenic reagent comprises, on a dry basis, at least 60 wt % carbon; 0 wt % to 35 wt % water moisture; and 1 wt % to 30 wt % of a binder, wherein the biocarbon pellet is characterized by an adjustable Hardgrove Grindability Index (HGI) from about 30 to about 120, as shown in the Examples. The pellet HGI is adjustable by controlling process conditions and the pellet binder. The binder can be an organic binder or an inorganic binder. The carbon is renewable as determined from a measurement of the 14C/12C isotopic ratio. Many processes of making and using the biocarbon pellets are described. Applications of the biocarbon pellets include pulverized coal boilers, furnaces for making metals such as iron or silicon, and gasifiers for producing reducing gas.