Globally, 39% of carbon emission is due to the building and construction industry, of which 11% is due to building materials like concrete and steel-related emissions. To prevent disastrous climate changes, decarbonizing this sector is critical. Novel environment friendly bio-composite materials and 3D printing techniques and technologies have been developed as an alternative to subtractive manufacturing processes and hazardous materials. The construction sector is one such sector witnessing a paradigm shift in both materials and manufacturing technologies. The authors have made one such attempt in the growing research domain to present and address the following gaps: (1) absence of a promising bio-composite formulation with enhanced properties as an alternative to the conventional concrete material; (2) a suitable 3D printing technology for building construction parts from the novel material proposed. This paper formulates a novel carbon–neutral bio-based UV–thermal curable composite with high-performance behavior as an alternative to concrete for 3D printing building and construction components and discusses an autonomous, energy-efficient UV 3D printing system for using the UV–thermal curable composite. Multiple formulations have been discussed, and the structural integrity and performance of the new formulation showcasing the best properties versus the existing steel rebar-concrete (RCC) are compared using a 3-point-bend test simulation in ANSYS structural analysis. Subsequently, a UV-assisted gantry 3D printing technology has been discussed for dual curing of the UV–thermal composite.