AbstractThe construction sector adversely affects the environment. In this research, biowaste and electronic waste are used as raw materials to produce lightweight cement blocks. Cement-like material was synthesized using cockleshells and rice husk ash as raw materials, and the filler used in the cement blocks primarily consisted of nonmetallic fractions (NMF) of printed circuit board (NMF residue). The NMF residue was characterized by X-ray diffraction and exhibited prominent peaks corresponding to SiO2 and Al(OH)3. Morphological examination of the NMF residue revealed irregularly-shaped particles with an average size of 29.2 μm. The use of NMF residue as fillers adversely affected the compressive strength of the lightweight cement blocks. Nevertheless, when the NMF residue content did not exceed 15 wt.%, the average compressive strength was 3.83–4.63 MPa and the average density was 1.086–1.19 g/cm3, which are within the acceptable ranges specified by the Thai Industrial Standards Institute. The concentrations of hazardous elements, such as Pb, Hg, Cr, Cd, As, Be, and Ni, were in the range 0–220 ppm, below the limits set by the Restriction of Hazardous Substances Directive. This study highlights a synergistic approach to waste utilization in the fabrication of lightweight cement blocks suitable for practical applications.