INFORM November/December 2025

32 • inform November/December 2025, Vol. 36 (10)

sel and propane co-production from waste feedstocks. Propane puri fication is often overlooked in techno-economic assessments of green diesel processes; it is hypothesized that its explicit inclusion may significantly impact overall process viability. To test this, a process simulation and economic evaluation were conducted for the co-pro duction and purification of green diesel and propane via hydro processing of used cooking oil. The novelty of this work lies in the integrated evaluation of fuel quality parameters, process simulation, and economic performance. The process, simulated in Aspen Plus, achieved 81.3 % green diesel yield and 5.4 % propane yield, with a hydrogen consumption of 29 kg per ton of feed oil. Economic analy sis showed that feedstock costs dominated operating expenses (73 % from used cooking oil), leading to negative net present values across all production scales. The minimum selling price for green diesel ranged from 1.78 to 1.17 US$/L (vs. 0.73 US$/L for fossil diesel), and for propane, from 1.22 to 0.80 US$/kg (vs. 0.50 US$/kg fossil equiv alent). Capital costs reached 95 million USD at the highest capacity, with hydrogen compressors accounting for 48 % of equipment costs. Including the propane purification section added 6.5–8.5 % to cap ital investment, mainly due to absorption and stripping units. These findings underscore the importance of including purification steps in early-stage assessments and highlight the need for policy incentives or alternative revenue sources (e.g., carbon credits) to ensure the eco nomic viability of such biorefineries. Valorization of used cooking oil: challenges, This review explores the recycling of used cooking oil, a global waste product with an annual production ranging from 41 to 67 mil lion tons, for waste management and resource recovery. It exam ines the sources and composition of used cooking oil, focusing on its potential as a feedstock for valuable products. The review ana lyzes biochemical, thermal, and chemical conversion methods for their application in valorization of UCO (Used Cooking Oil). The advanced techniques such as catalytic upgrades, electrochemical conversion, membrane separation, and supercritical fluid extraction have also been investigated for their role in improving efficiency. Although biodiesel is the widely produced product, the review also sheds light on the recent researches for development of plastic, soap and other value-added products from UCO. Using a case study meth current developments, life cycle assessment and future prospects Kumar, A., et al. , Discover Sustainability , 6, 119, 2025. https://doi.org/10.1007/s43621-025-00905-7

odology and a review of recent research, the article also addresses challenges like feedstock variability and environmental impacts. It discusses market trends, regulatory frameworks, and potential research directions, aiming to integrate used cooking oil valorization into sustainable waste management and circular economy practices.

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Ryan J. Stoklosa is a research chemical engineer and lead scientist for the USDA, Agricultural Research Service located in Wyndmoor, Pennsylvania. His research focuses on technologies to convert plant biomass into fuels and high value chemicals.

Crude glycerol generated during biodiesel production can increase economic value if viewed as a recoverable co-product. Recent work has used crude glycerol from biodiesel generation for chem ical conversion to bio-based chemicals or fuels. The first article took refined, crude glycerol and performed gas phase dehydration using a copper catalyst to produce acetol, an important intermedi ate chemical for building carbon chains for use in aviation fuel. The second article upgraded crude glycerol through electrooxidation to the high value chemical format while disentangling the influence of residual impurities (e.g. methanol) during processing. The last article developed a process for upgrading glycerol waste using a lig nin-based acid catalyst to generate a bio-based fuel additive that can be added back to biodiesel fuel stocks. Valorization of pure and biodiesel-derived refined crude glycerol to renewable acetol over copper-based catalyst: Effect of operating conditions and catalyst stability Lete, A., et al. , Biomass and Bioenergy , 203, 108273, 2025. https://doi.org/10.1016/j.biombioe.2025.108273 Acetol is a key intermediate in the aldol condensation of bio mass-derived furans, enabling the production of carbon chains within the aviation fuel range. This work proposes glycerol, a bio mass-derived by-product from biodiesel production, as a renew able feedstock for acetol production. The catalytic performance of