Use of receding horizon optimal control to solve MaxEP-based biogeochemistry problems Running title: MaxEP and biogeochemistry Joseph J. Vallino, Christopher K. Algar, Nuria Fernández González and Julie A. Huber Marine Biological Laboratory, Woods Hole, MA, USA jvallino@mbl.edu Abstract The MaxEP principle has been applied to steady state systems, but bio- geochemical problems of interest are typically transient in nature. To apply MaxEP to biogeochemical reaction networks, we propose that living systems max- imum entropy production over appropriate time horizons based on strategic infor- mation stored in their genomes, which differentiates them from inanimate chemis- try, such as fire, that maximizes entropy production instantaneously. We develop a receding horizon optimal control procedure that maximizes internal entropy pro- duction over different intervals of time. This procedure involves optimizing the stoichiometry of a reaction network to determine how biological structure is parti- tioned to reactions over an interval of time. The modeling work is compared to a methanotrophic microcosm experiment that is being conducted to examine how microbial systems integrate entropy production over time when subject to time varying energy input attained by periodically cycling feed-gas composition. The MaxEP-based model agrees well with experimental results, and model analysis shows that increasing the optimization time horizon increases internal entropy production. Accepted (July 2012) in: Beyond the Second Law: Entropy Production and Non- Equilibrium Systems. R. C. Dewar, C. H. Lineweaver, R. K. Niven and K. Re- genauer-Lieb, Springer.