Optimization of the Ex Situ Biomethanation of Hydrogen and Carbon Dioxide in a Novel Meandering Plug Flow Reactor: Start-Up Phase and Flexible Operation

With the increasing use of renewable energy resources for the power grid, the need for long-term storage technologies, such as power-to-gas systems, is growing. Biomethanation provides the opportunity to store energy in the form of the natural gas-equivalent biomethane. This study investigates a novel plug flow reactor that employs a helical static mixer for the biological methanation of hydrogen and carbon dioxide. In tests, the reactor achieved an average methane production rate of 2.5 LCH4LR∗d (methane production [LCH4] per liter of reactor volume [LR] per day [d]) with a maximum methane content of 94%. It demonstrated good flexibilization properties, as repeated 12 h downtimes did not negatively impact the process. The genera Methanothermobacter and Methanobacterium were predominant during the initial phase, along with volatile organic acid-producing, hydrogenotrophic, and proteolytic bacteria. The average ratio of volatile organic acid to total inorganic carbon increased to 0.52 ± 0.04, while the pH remained stable at an average of pH 8.1 ± 0.25 from day 32 to 98, spanning stable and flexible operation modes. This study contributes to the development of efficient flexible biological methanation systems for sustainable energy storage and management.

SU-F-BRCD-05: Mean Regional Dose to the Esophagus Predicts Acute Toxicity Rate for Lung Cancer Patients

PURPOSE

The relationship between spatial aspects of the dose distribution and incidence of acute radiation esophagitis for non-small-cell lung cancer (NSCLC) patients is not well understood. Specifically, the location of dose along the superior-inferior (SI) axis of the esophagus has not been previously considered. We introduce the concept of mean regional dose (MRD) calculated for esophageal subvolumes, and test for significance for prediction of acute esophagitis (AE).

METHODS

The 3D dose distribution within the esophagus was extracted for 541 NSCLC patients treated with definitive photon therapy. The esophagus contour was divided into equal geometric halves, thirds, and fourths along the SI direction of the structure. MRD in each subvolume was calculated. Univariate logistic regression was performed to determine the correlation between MRD and CTCAE3.0 AE grade = 2 (medical intervention). The MRD was incorporated into an existing NTCP model (based on mean dose for the total esophageal volume) as a separate additive factor.

RESULTS

Univariate analysis indicated a significant correlation between AE grade = 2 and MRD in each of the esophageal subvolumes except for the inferior third and inferior-most quarter. There was a statistically significant improvement when including the additive MRD factor for the superior/inferior halves, superior/inferior thirds, and superior-most/inferior-most quarters into the NTCP model.

CONCLUSIONS

This study investigates previously unexplored regional differences in delivered dose to the esophagus of patients treated for NSCLC. There is evidence to suggest that dose to the superior portions of the esophagus is more important as it relates to the potential for acute toxicity. The 541 patient cohort is the largest database used to investigate AE in patients treated for NSCLC, strengthening the power of the statistical results. Additional methods to incorporate dose in individual esophagus voxels (along the SI axis) into the NTCP model are also being explored.