Biomass has long been investigated both as a (nearly) CO2 neutral substitute for fossil fuels and as a means for sequestering carbon in terrestrial ecosystems (Kheshgi et al. 2000). More recently, the potential to integrate carbon capture and storage technologies (“CCS”)— conceived to enable fossil fuel use without atmospheric CO2 emissions—with bio-energy systems has emerged as a means to capture atmospheric carbon, fixed through photosynthesis, and sequester it from the atmosphere for geologic timescales (Obersteiner et al. 2001; Yamashita and Barreto 2004; Mollersten et al. 2003; Rhodes and Keith 2005). The ability of such integrated systems to produce energy products with negative net atmospheric carbon emissions could have important implications for mitigating anthropogenic climate change. The scale and timing of biomass-based mitigation is limited by the availability and cost of conversion technologies, many of which are currently inefficient or technologically immature. More fundamentally, it is limited by feasible scales of biomass production, estimates of which are highly uncertain and indicate that the capacities envisioned within aggressive proposals, including those by Read (2008), may not be achievable (Hoogwijk et al. 2003; Berndes et al. 2003). Concern for environmental, social, and economic impacts of biomass development may further constrain production below technically feasible levels. The current biofuels boom may be illustrative in this context. On the one hand, it demonstrates the feasibility of rapid, large-scale bio-energy deployments; while on the other hand, it provides examples of undesirable environmental and social consequences from large-scale biomass production (Ziegler 2007; Rosenthal 2007a, b). Climatic Change (2008) 87:321–328 DOI 10.1007/s10584-007-9387-4