Commercial-scale liquid-biofuel production utilizing forest-based biomass would require feedstock supply from a large geographical area. Feedstock composition, supply chains' arrangements, and the resulting greenhouse gas (GHG) emissions are location dependent, and case-specific assessments are needed if one is to guarantee the fulfillment of GHG reduction requirements by a specific biofuel product. This work assessed GHG emissions derived from the feedstock supply and transportation chain to three possible commercial-scale biodiesel plant locations in Finland (Rauma, Porvoo, and Kemi) at site-specific level. The supply of 7.2 PJ yr−1 (approximately 1 million m3solid) of forest biomass (harvesting residues, stumps, and small-diameter energy wood) was assessed for each location, including four distinct scenarios for truck and railway transportation and two scenarios for biomass availability. Biomass availability and transportation-network assessments were conducted through utilization of geographical information system methods, and the GHG emissions were assessed by means of life-cycle assessment. The results showed that the GHG emissions of the supply chains can be effectively reduced through use of railway transportation from distant supply areas. Furthermore, even though the supply-chain GHG emissions differed by up to 30% between the case-study locations, the GHG emissions of the feedstock supply chain, from roadside stores of uncomminuted biomass to comminuted biomass delivered to the plants, were relatively low (2–4%) when compared with the GHG emissions of fossil diesel.