The formula to calculate the burning efficiency of a biomass furnace is:

\[ \xi_b = \frac{H_v - H_r}{H_v} \times 100 \]

Where:

• \(\xi_b\) is the burning efficiency in percentage (%).
• \(H_v\) is the heating value of fuel in KCal/kg.
• \(H_r\) is the heating value of ash residue in KCal/kg.