Carbon-negative cement-bonded biochar particleboards

Highlights

•	Carbon-negative particleboard is  for the first time pioneered by incorporating 70 wt.% biochar.
•	Biochar addition in MOSC systems reduced the thermal conductivity.
•	Further incorporation of SCMs improves the mechanical properties and CO2 sequestration.
•	Biochar particleboard can sequester 137 kg CO2 tonne−1 and yield potential profit of 92–116 USD m−3.

Abstract

Biochar from bio-waste pyrolysis presents excellent CO₂ sequestration capacity. This study innovated the design of cement-bonded particleboards utilizing a substantial amount of 50–70 wt.% pre-soaked biochar to render the products carbon-negative. We investigated the roles of biochar in magnesium oxysulfate cement (MOSC) system and demonstrated good mechanical and functional properties of biochar cement particleboards. In the presence of biochar, the amounts of hydration products were enriched in the cement systems as illustrated by the thermogravimetric analyses (TGA) and X-ray diffraction (XRD). We further incorporated supplementary cementitious materials (SCMs) and generated 5 Mg(OH)₂⋅MgSO₄·7H₂O (5–1–7) phase in the MOSC system. As a result, our designs of biochar particleboards satisfied the standard requirements for flexural strength (> 5.5 MPa) and thickness swelling (< 2%). Moreover, our biochar particleboards presented a low thermal conductivity as the biochar pores disrupted thermal bridging within particleboards. We illustrated that the high dosage ratio of biochar could significantly offset the CO₂ emissions of the particleboards (i.e., carbon-negative) via life cycle assessment. Noticeable economic profits could also be accomplished for the biochar particleboards. For instance, the 50BC-MOSC bonded particleboard (with 50 wt.% pre-soaked biochar as aggregate, 50 wt.% MOSC as binder) with promising mechanical properties could store 137 kg CO₂ tonne⁻¹ and yield an overall economic profit of 92 to 116 USD m⁻³ depending on the carbon prices in different countries. In summary, our new designs of carbon-negative biochar particleboards could curtail carbon emissions in the construction materials and promote the realization of carbon neutrality and circular economy.

Funding

The Hong Kong Green Tech Fund(GTF202020153); Alexander von Humboldt Foundation; Open Project of State Key Laboratory of Clean Energy Utilization, Zhejiang University(ZJUCEU2022001)