Economic and environmental performance of non-cellulosic fermentable carbohydrates production for biofuels and chemicals

Fermentable carbohydrates (FC) are a major cost component and a major environmental burden in the production of biofuels and bio-based commodity chemicals; consequently, the cost of FC determines the economic feasibility and environmental performance of biofuels and bio-based commodity chemicals. Producing FC with conventional technology and without the additional processing steps of food-grade sugar can result in a low-cost industrial-grade fermentable sugar that is competitive with that of raw sugar. This study assesses the minimum selling prices (MSP) and the life cycle environmental impacts of FC produced from energycane, sweet sorghum, sugar beet, and corn all of which are grown in the US. The study also assesses FC produced from sugarcane grown in Brazil, which is used as a gauging reference of a low-cost FC source. The MSP was determined by calculating the prices of FC that will result in a net present value (NPV) of 0 with a discount rate that is better than that of a low-risk investment. Environmental performance was assessed by accounting for the life cycle emissions of greenhouse gas, use of fossil energy, and eutrophication potential. The MSP of FC produced from the evaluated feedstocks varies from $0.30 kg⁻¹ for FC produced from sugarcane to $0.50 kg⁻¹ for FC produced from sugar beet or sweet sorghum. The study shows that in the US, FC from energycane has a similar MSP of $0.40 kg⁻¹ to that of FC from corn at $0.38 kg⁻¹, but FC from energycane has lower environmental impacts than FC from corn. The potential for economic feasibility exists in the US for FC from energycane, and with similar environmental impacts to sugarcane and lower environmental impacts than corn. Opportunities for a lower MSP of $0.32 kg⁻¹ exist by using sweet sorghum as a supplementary feedstock with energycane to increase the utilization of the processing plant and reduce the capital cost per unit mass of FC. Producing FC in the US from energycane and supplementing it with sweet sorghum results in an MSP that is lower than raw sugar, which varied from $0.20 kg⁻¹ to $0.63 kg⁻¹ and averaged $0.35 kg⁻¹ from years 2005 through 2019. This shows that the US has access to a low-cost source of FC with lower environmental impacts than corn and with a price that is not subjected to external factors like the fluctuating price of raw sugar.