My long term goal is a quantitative and mechanistic understanding of the relationship between infaunal ecology, their actions and their rates and the consequent modification of sediments, including the creation and destruction of heterogeneities and the modes and rates of sediment component mixing. The objective of this research was the development of a model/computer code that embraces the discrete nature of sediments and organisms, rather than averaging it away, and that utilizes biologically relevant parameters, such as animal sizes, population density, feeding and locomotion rates, and probabilities for observed behaviour(s), to drive the model and produce predictions about sediment composition and fabric. The approach is the direct modelling of organism-sediment interactions via a new type of model. Biologically active sediment is represented on a computer as a regular lattice of quasi-particles with individually assigned chemical, biological or physical properties. Model benthic organisms are introduced in the form of automatons, i.e. programmable entities, that are capable of moving through the particle lattice by displacing or ingesting-defecating particles. Each automaton obeys a set of rules, both deterministic and stochastic, designed to mimic real organism behavior, and different types of organisms have different sets of rules.