Techno-economic analysis of guayule (Parthenium argentatum) pyrolysis biorefining: Production of biofuels from guayule bagasse via tail-gas reactive pyrolysis

The tire industry is currently considering natural rubber from guayule (Parthenium argentatum Gray) as a viable alternative to imported Hevea natural rubber, or petroleum-based synthetics, to meet expanding materials needs of the industry. However, only 5-10% of the harvested guayule plant is converted into rubber latex. For economic sustainability, the industry must identify viable uses for the balance residual, termed bagasse. Bioenergy production has been considered, but conversion facilities must be co-located to avoid additional costs in transportation of the bagasse. This study investigated the economics of processing a minimum of 200 metric ton per day (MTPD) of guayule bagasse to produce biofuels in a biorefinery co-located with a guayule latex processing facility. A unique aspect of the simulated process was the use of the tail gas reactive pyrolysis (TGRP) technology that formulates an intermediate bio-oil with less oxygenates and therefore requires only mild upgrading to fuel products. This achieved a yield of 16.2%, distributed in the gasoline (9.7%), jet fuel (5.6%), and diesel (0.9%) carbon ranges. The capital cost was estimated at $58.74 million (MM), and the annual operating cost was estimated at $14.19 MM. A discounted cash flow rate of return (DCFROR) analysis was conducted to evaluate the economic feasibility based on a 30-year plant life and 10% internal rate of return. The minimum fuel selling price (MFSP) calculated was 1.88 $/L for gasoline, 1.84 $/L for jet fuel and 1.91 $/L for diesel fuel, clearly showing the limitations imposed by economies of scale of the current guayule bagasse availability. However, there is a potential to reduce the MFSP by increasing the facility capacity and utilizing the valuable co-products that accompany guayule pyrolysis biorefining. Sensitivity analysis indicates the MFSP of gasoline can be lowered to 0.96 $/L considering the most optimistic scenario, comprising an integrated large facility of 2000 MTPD, lower cost of hydrogen, and the sale of a premium-quality residual guayule biorefinery coke.