In their study in Honduras, the authors carefully mixed rice hull char (made in a TLUD stove) with cassava chips and foliage and fed that to cattle, while doing a careful control, and measuring the health of the cattle as well as their methane emissions. The results are encouraging.
Twelve local “Yellow” cattle with initial live weight ranging from 80 to 100 kg were assigned in a completely randomized block design to a 2*2 factorial arrangement of four treatments with three replications. The factors were: biochar at 0.6% of diet DM or none; and potassium nitrate at 6% of diet DM or urea at 1.83% of diet DM. The basal diet was cassava root chips fed ad libitum and fresh cassava foliage at 1% of LW (DM basis). Sodium sulphate and sodium chloride were added to the diet at the rate of 0.4% and 0.5% in the DM. The trial lasted 98 days following a 21 day adaptation to the diets.