Wood residues are modelled for unprocessed woods:

• Commercial forestry plantation residues
• Deciduous tree offcuts
• Sustainable harvesting from indigenous woodlands (i.e. only dead wood)
• Alien vegetation control

Processed wood residues are derived from the wastes of:

• Sawmills, such as chips, sawdust, and bark, and
• Pulp mills, such as partially combusted boiler ash, bark, sludge, sawdust, and black liquor.

• Maize
• Wheat
• Sunflowers
• Sugarcane
• Sorghum

The residues of the above crops have been modelled based on a simple rainfall and heat units equation.

Together these crops make up over 90% of the area currently under crop production, and over 98% of the annual crop production in South Africa.

Grasses are a potential source of biomass energy that can seemingly be harvested on an annual basis with no adverse effect to the veld.

Above ground net primary productivity of grasses has been modelled for the grassland and savanna biomes, as depicted by the National Botanical Institute vegetation map ⁽¹⁾, based on a function of growth days, temperature and soil fertility. Growth days are derived from potential evaporation and precipitation.