If LPG has a calorific value of ~55 kJ/g and wood has a calorific value of ~20 kJ/g, then to obtain the same amount of heat, roughly how many grams of wood would replace 100 g of LPG?

Heat from 100 g LPG = 100 × 55 = 5500 kJ. To get 5500 kJ from wood with 20 kJ/g, mass = 5500 / 20 = 275 g. So you need almost three times as much wood by mass as LPG for the same heat — one reason LPG dominates urban kitchens.