Optimising Milk bush (Euphorbia tirucalli. L) density and felling age for biomass and energy production in Tanzania's semi-arid climates

Euphorbia tirucalli, L. has excellent C3/CAM metabolism in its stems and leaves, making it a viable non-food energy plant with a high biomass production. A CRBD with five PPD treatments was utilised to grow E. tirucalli plants in the Bahi district of Dodoma, Tanzania, to determine the optimal PPD and felling age at initial harvesting for high biomass and energy production. The study revealed that E. tirucalli produced more biomass and energy in the wet season than in the dry season. It produced the maximum and minimum quantity of biomass and energy (4.0 - 5.0kg DMtree−1 and 15 - 18.0MJkg−1). The results correspond to 4,800 - 5,600 kg DMtree−1 and 28,320 - 28,800 MJkg−1 for very low-density plots (1,600 plants ha−1). These results were attained at very low optimal density of 1,600VL plants ha−1 ( 3.5 kg tree−1) and energy (> 18MJkg−1) production from E. tirucalli in Tanzania's semi-arid climates cost-effectively and sustainably.