The problem of utilizing plant wastes of the agro-industrial complex is equally important and urgent. In this regard, it is advisable to develop a complex technology of plant waste application to solve the ecological problems of environmental pollution with heavy metals. Modification of walnuts shells with orthophosphoric acid has proven to be a promising process for obtaining the biosorbents with the efficient sorption properties. It was found out that the increase in the concentration of inorganic acid in modification time promotes the improvement in sorption capacity. Such biosorbents can be used in low-waste water demineralization systems. The utilization of waste biosorbents through the use in the composition of building materials is effective from an economic point of view. It was shown that the biosorbent acts as a fine additive; the increase in normal density and acceleration in hardening time takes place. At the same time, the compressive strength of the cement with the application of biosorbents decreases slightly. The results show that the modified walnuts shells have a slightly adverse effect on the hardening time of cement.