The formula to calculate the area of the fuel bed in a biomass furnace is:

\[ A_{fb} = \frac{P_d}{BR} \]

Where:

• \(A_{fb}\) is the area of the fuel bed in square meters (m²).
• \(P_d\) is the design power in KCal/hr.
• \(BR\) is the burning rate in KCal/hr-m².