Accurate assessment and monitoring of biomass are important for managing terrestrial ecosystems, their sustainability especially for developing world. This case study is interested in the Sudan Savanna agroforestry Parklands of North Western Benin, where agroforestry parklands’ systems play key roles in the socio-ecological system among which firewood energy. For many years, research endeavours reported the sustainability of the system, nevertheless with little importance to population growth and the related increasing firewood demand. To address this, various biophysical and socio-economic data were collected on 137 households and their plots belonging to 17 villages spread across Dassari catchment. The first Key findings are that, among the 3 main utilisations of trees in the area, firewood is in the front line. Around 100% and 76% of the households use firewood and NTFPs respectively, while only 8% of them use trees for fodder. Secondly, with an average firewood consumption of 1.026 kg per capita in rainy season again 0.814 kg in dry season, the farmers consume more firewood in the rainy season (p<0.05). These values correspond respectively to 1.559 kg and 2.015 kg when considering farmers ‘perceptions. Therefore we conclude farmers tend to overestimate the overall quantity consumed (p<0.01). Yet, there are many factors impacting the amount of firewood used at the household level although the farmers lack straightforward explanations. Tree branching (30%) is the most encountered firewood collection method. The farmers prefer Combretum sp. (69%) among shrubs and Anogeissus leiocarpus (23%) among trees. The analysis of the biomass (1, 153, 363, 780.44 ± 636305.2 kg corresponding to 235, 384, 2526 kg in terms of dry wood) revealed that the catchment is a valuable source of carbon sink. Nevertheless, the effect of population growth and climate change humper its sustainability.