This is a textbook for undergraduate students of chemical and biological engineering. It is also useful for graduate students, professional engineers and numerical analysts. All reactive chemical and biological processes are highly nonlinear allowing for multiple steady states. This book addresses the bifurcation characteristics of chemical and biological processes as the general case and treats systems with a unique steady state as special cases. It uses a system approach which is the most efficient for knowledge organization and transfer. The book develops mathematical models for many commercial processes utilizing the mass-, momentum-, and heat-balance equations coupled to the rates of the processes that take place within the boundaries of the system. The models are solved numerically through MATLAB codes with emphasis on the design and optimization of the chemical and biological industrial equipment and plants, such as single and batteries of CSTRs, porous and nonporous catalyst pellets and their effectiveness factors, tubular catalytic and noncatalytic reactors, fluidized bed catalytic reactors, coupled fluidized beds such as reactor-regenerator systems (industrial fluid catalytic cracking units), fluidized bed reformers for producing hydrogen or syngas, fermenters for fuel ethanol, simulation of the brain acetylcholine neurocycle, anaerobic digesters, co- and countercurrent absorption columns, and many more. The book also includes verification against industrial data. The algorithms include solving transcendental and algebraic equations, with and without bifurcation; as well as initial and boundary value ordinary differential equations. Said Elnashaie is Professor of Chemical and Biological Engineering at the University of British Columbia. Frank Uhlig is Professor of Mathematics at Auburn University. Chadia Affane is a Ph.D. candidate in Applied Mathematics at Auburn with a B.S. in Chemical Engineering.