Agricultural and forest residues represent a major fuel source for potential bio-energy projects in many developing countries. However, a number of risks can threaten a secure fuel supply. This paper presents a methodology to set up fuel supply strategies for large-scale biomass conversion units (between 10 and 40 MWe), and to determine the connected risks and to minimize them. The methodology focuses (amongst others) on variations in residue quantities produced, limited accessibility of residues, utilization by other competitors and logistical risks. For each risk, possible ranges are determined and incorporated in different fuel supply scenarios which indicate how biomass quantities and prices may vary under different circumstances. The methodology was demonstrated in Northeastem Thailand. It is shown that process-based residues are already highly utilized, white more expensive field-based residues represent the largest net available biomass potential. Both residue quantities and prices (0.59-2.58 US$/GJ) can vary strongly, mainly depending on fluctuating harvests, increased utilization by competitors and varying transportation costs. In the current Thai situation, only a state-of-the-art combustion plant seems to be able to operate economically on residues. It is concluded that assessing the risks connected to the fuel supply is vital for the successful operation of large-scale bio-energy projects.