Pyrolysis as an alternate to open burning of crop residue and scrap tires: Greenhouse emissions assessment and mechanical performance investigation in concrete

Abstract

In this study, waste from agriculture and industrial sources was transformed into valuable biochar to reduce the environmental threats associated with the open burning of this waste and used as an additive in concrete for the first time to impart superior mechanical characteristics to conventional concrete. Carbonaceous inert particles were derived from the pyrolysis of wheat straw, cotton stalk, and scrap tires. The environmental impact assessment was carried out to gauge the impact of pyrolysis process on char production and the global warming potential for engineered concrete. Based on the analysis, pyrolysis of scrap tires manifested the lowest net global warming potential of −1.285 KgCO 2 -eq. Furthermore, the characterization of synthesized inert particles was carried out by using Laser granulometry, scanning electron microscopy, x-ray diffraction analysis, thermo-gravimetric analysis, and Raman spectroscopy. Thereafter, the mechanical performance of concrete incorporated with synthesized inert particles by 1% of cement weight was evaluated and compared with the reference formulation of concrete having no amount of synthesized inert particles. A significant improvement of 51.42% in terms of flexural resistance was achieved by using pyrolyzed cotton stalk. Fracture toughness index and fracture energy were also improved with the inclusion of these inert particles. To rationalize the improved performance of specimens engineered with synthesized inert particles, fracture path analysis was conducted. In comparison to the reference formulation, composites reinforced with pyrolyzed scrap tires rendered maximum improvement in compressive strength by 43.1%. From the analysis of the emissions to strength ratio of concrete, specimens containing pyrolyzed scrap tires ensued the maximum reduction of 31.31% relative to the reference formulation. • Agricultural residue and scrap tires waste were transfigured to biochar through pyrolysis. • Net negative global warming potential was attained by opting for pyrolysis. • Maximum gain of 51.4% in flexural resistance was obtained with pyrolyzed cotton stalk. • Concrete with 43.1% enhanced compressive strength was made with pyrolyzed scrap tires. • 45.58% increase in strength to emissions ratio was achieved with the addition of pyrolyzed scrap tires.