The PYSOLO project—Pyrolysis of biomass by concentrated solar power, funded through Horizon Europe—explores the use of solar energy to drive biomass pyrolysis in a sustainable way. This study focuses on the environmental performance of the solar subsystem, which consists of a heliostat field and a rotary kiln solar receiver. A distinctive feature of the system is its use of particle heat carriers (PHCs), including silica sand, bauxite, and olivine, which circulate inside the rotary kiln. The kiln simultaneously acts as both the solar receiver and the heat transfer medium in a central tower setup. Once heated, the particles are directed to a downstream reactor where pyrolysis occurs.