The application of carbon-negative biochar in cement composites can effectively reduce carbon emissions of construction materials. In this study, low-carbon composites were tailored with high volume of food waste digestate (FWD) biochar aggregate. The biochar was customized at different temperatures with the goal of enhancing the properties of cement-based composites. Backscattered electron microscopy (BSEM) images show that FWD biochar with a grey circle shape exhibited strong bonding with the cement matrix. Nano-indentation results indicate that the two statuses of FWD biochar showed visco-elastic and elastic-plastic modes of deformation, respectively. The FWD biochar aggregate prepared at higher pyrolysis temperatures (i.e., 650 degrees C and 750 degrees C) has higher elastic modulus (up to 11.4 GPa), which can be applied to make biochar blocks with higher strength and lower density compared to the biochar pyrolyzed at 550 degrees C. As a result, FWD 750BC blocks could reach 28-d compressive strength of 57.8 MPa and density of 1.77 g cm-3, which fulfilled the requirements of high-strength lightweight aggregate concrete. Hence, this study established a foundation to utilize FWD biochar as an aggregate in high-strength biochar construction materials.