Coproduction of high-value bioproducts at biorefineries is a key factor in making biofuels more cost-competitive. One strategy for generating coproducts is to directly engineer bioenergy crops to accumulate bioproducts in planta that can be fractionated and recovered at biorefineries. Here, we develop quantitative insights into the relationship between bioproduct market value and target accumulation rates by investigating a set of industrially relevant compounds already extracted from plant sources with a wide range of market prices and applications, including <$10/kg (limonene, latex, and polyhydroxybutyrate [PHB]), $10 to $100/kg (cannabidiol), and >$100/kg (artemisinin). These compounds are used to identify a range of mass fraction thresholds required to achieve net economic benefits for biorefineries and the additional amounts needed to reach a target $2.50/gal biofuel selling price, using cellulosic ethanol production as a test case. Bioproduct market prices and recovery costs determine the accumulation threshold; we find that moderate- to high-value compounds (i.e., cannabidiol and artemisinin) offer net economic benefits at accumulation rates of just 0.01% dry weight (dwt) to 0.02 dwt%. Lower-value compounds, including limonene, latex, and PHB, require at least an order-of-magnitude greater accumulation to overcome additional extraction and recovery costs (0.3 to 1.2 dwt%). We also find that a diversified approach is critical. For example, global artemisinin demand could be met with fewer than 10 biorefineries, while global demand for latex is equivalent to nearly 180 facilities. Our results provide a roadmap for future plant metabolic engineering efforts aimed at increasing the value derived from bioenergy crops.

Gaseous streams in biorefineries have been undervalued and underutilized. In cellulosic biorefineries, coproduced biogas is assumed to be combusted alongside lignin to generate process heat and electricity. Biogas can instead be upgraded to compressed biomethane and used as a transportation fuel. Capturing CO 2 -rich streams generated in biorefineries can also contribute to greenhouse gas (GHG) mitigation goals. We explore the economic and life-cycle GHG impacts of biogas upgrading and CO 2 capture and storage (CCS) at ionic liquid-based cellulosic ethanol biorefineries using biomass sorghum. Without policy incentives, biorefineries with biogas upgrading systems can achieve a comparable minimum ethanol selling price (MESP) and reduced GHG footprint ($1.38/liter gasoline equivalent (LGE) and 12.9 gCO 2e /MJ) relative to facilities that combust biogas onsite ($1.34/LGE and 24.3 gCO 2e /MJ). Incorporating renewable identification number (RIN) values advantages facilities that upgrade biogas relative to other options (MESP of $0.72/LGE). Incorporating CCS increases the MESP but dramatically decreases the GHG footprint (−21.3 gCO 2e /MJ for partial, −110.7 gCO 2e /MJ for full CCS). The addition of CCS also decreases the cost of carbon mitigation to as low as $52−$78/t CO 2 , depending on the assumed fuel selling price, and is the lowest-cost option if both RIN and California's Low Carbon Fuel Standard credits are incorporated.

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Near-term decarbonization of aviation requires energy-dense, renewable liquid fuels. Biomass-derived 1,4-dimethylcyclooctane (DMCO), a cyclic alkane with a volumetric net heat of combustion up to 9.2% higher than Jet A, has the potential to serve as a low-carbon, high-performance jet fuel blendstock that may enable paraffinic bio-jet fuels to operate without aromatic compounds. DMCO can be produced from bio-derived isoprenol (3-methyl-3buten-1-ol) through a multistep upgrading process. This study presents detailed process configurations for DMCO production to estimate the minimum selling price and life-cycle greenhouse gas (GHG) footprint considering three different hydrogenation catalysts and two bioconversion pathways. The platinum-based catalyst offers the lowest production cost and GHG footprint of $9.0/L-Jet-A eq and 61.4 gCO 2e /MJ, given the current state of technology. However, when the supply chain and process are optimized, hydrogenation with a Raney nickel catalyst is preferable, resulting in a $1.5/L-Jet-A eq cost and 18.3 gCO 2e /MJ GHG footprint if biomass sorghum is the feedstock. This price point requires dramatic improvements, including 28 metric-ton/ha sorghum yield and 95−98% of the theoretical maximum conversion of biomass-to-sugars, sugars-to-isoprenol, isoprenol-to-isoprene, and isoprene-to-DMCO. Because increased gravimetric energy density of jet fuels translates to reduced aircraft weight, DMCO also has the potential to improve aircraft efficiency, particularly on long-haul flights.

With increasing environmental concerns with respect to the petroleum-based adhesive production process, bio-based adhesive has been explored as a promising replacement. The purpose of this paper was to explore the economic feasibility of structural bio-adhesives made from glycerol, a byproduct of biodiesel production. SuperPro Designer software was employed to perform the techno-economic analysis. Several key parameters were analyzed, such as total capital investment, annual operating costs and revenues. It was found that the unit production cost of structural bio-adhesives ($2.45/kg) was compatible with that in the current market.Three different scenarios were built to investigate the worst-case scenario and the best-case scenario associated with this production process. Sensitivity analysis was also performed to evaluate the key parameters significantly influencing the economic result. In this study, material cost was determined to be the most significant factor throughout the production process. Discounted cash flow analysis was conducted to explore the influence of the time value of money. The minimum selling price obtained was $3.11/kg for this bioadhesive production process. Underlying issues and areas needed for improvement were also discussed in this study.

Forage sorghum is a promising feedstock for the production of biofuels and bioproducts because it is drought tolerant, high-yielding, and familiar to farmers across the world. However, sorghum spans a diverse range of phenotypes, and it is unclear which are most desirable as bioenergy feedstocks. This paper explores four forage sorghum types, including brown-midrib (bmr), non-bmr, photoperiod sensitive (PS), and photoperiod insensitive (non-PS), from the perspective of their impact on minimum bioethanol selling price (MESP) at an ionic liquid pretreatment-based biorefinery. Among these types, there are tradeoffs between biomass yield, lignin content, and starch and sugar contents. High biomass-yielding PS varieties have previously been considered preferable for bioenergy production, but, if most starch and sugars from the panicle are retained during storage, use of non-PS sorghum may result in lower-cost biofuels (MESP of $1.26/L-gasoline equivalent). If advances in lignin utilization increase its value such that it can be dried and sold for $0.50/kg, the MESP for each scenario is lowered and non-bmr varieties become the most attractive option (MESP of $1.08/L-gasoline equivalent). While bmr varieties have lower lignin content, their comparatively lower biomass yield results in higher transportation costs that negate its fuel-yield advantage.

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Techno-Economic Analysis (TEA) plays an important role in assessing economic performance and potential market acceptance for new technologies. Previous work has shown that the construction and operation of a cellulosic bioethanol plant can be very expensive. One of the largest cost categories is pretreatment processing. The purpose of this study was to conduct a detailed cost analysis to assess low moisture anhydrous ammonia (LMAA) pretreatment process at the commercial-scale, and to estimate the breakeven point in large-scale production. In this study, capital expenses, including annualized purchase and installation fees, and annual operating costs associated with each unit operation were determined. This research compared the unit cost per year between different scales of the LMAA process, and focused on exploring the optimal costeffective point for this pretreatment method for bioethanol production.