Economic, energetic, and environmental analysis of lignocellulosic biorefineries with carbon capture

Bioenergy with carbon capture and sequestration (BECCS) is a promising method for global warming mitigation. We use a mixed-integer nonlinear programming (MINLP) model to examine the impact of carbon sequestration credits, capture rates, biorefinery capacity, feedstock, and pretreatment selection on the performance of an ethanol biorefinery system. We find that biorefineries using feedstocks and pretreatment methods that lead to higher carbon emissions from fermentation and anaerobic digestion tend to have lower average carbon capture costs. Biorefineries with high biomass to ethanol yields, such as those using dilute acid pretreatment, can capture high percentages of the carbon in the feedstock if energy is purchased, but less excess energy available from residue combustion limits carbon capture at an energetically self-sufficient biorefinery. Biorefineries that use feedstocks with high lignin content or have low energy requirements produce the most excess energy, which enables higher capture rates. Importantly, we find that the inclusion of potential carbon capture technologies can increase the cost-optimal biorefinery capacity. For biorefineries that use processing depots and rail transportation, increasing capacity has minimal impact on the GHG balance and energy consumption of the system.