生物炭混凝土生命周期CO2排放评价

为评价生物炭混凝土的CO₂排放量,采用生命周期评价技术构建了生物质热解生产生物炭过程的碳排放计算模型、生物炭混凝土从原材料生产到混凝土拆除废弃阶段CO₂排放量化模型和生物炭混凝土服役期碳化-吸收模型,同时研究了生物炭按质量比例取代水泥对混凝土力学性能的影响。在此基础上,计算了1 m³C30生物炭混凝土的CO₂排放量,并与普通C30混凝土CO₂排放量进行对比。结果表明:生物炭作为一种碳负性材料,其碳元素含量越高,CO₂减排效果越好; 当生物炭取代率小于5.0%时,研磨后的超细炭颗粒可以充分发挥填充和内固化效应,有效地提高混凝土的力学性能; 生物炭混凝土生命周期CO₂排放量随生物炭取代率的提高而降低,5%取代率的1 m³木屑生物炭混凝土相比普通C30混凝土,可减排CO₂66.5 kg,减排率为20.7%; 生物炭混凝土在服役期内因碳化吸收CO₂占总碳排放量的1.8%～2.5%,而拆除废弃阶段由于混凝土的比表面积呈指数增长,碳化吸收量需要进一步研究。

Life cycle assessment on CO2 emission for biochar concrete

To evaluate the CO₂ emissions of biochar concrete, life cycle assessment technology was used to construct a carbon emission calculation model for the production of biochar by biomass pyrolysis, a CO₂ emission model for biochar concrete from raw material production to concrete demolition and abandonment, and a carbonation-absorption model for biochar concrete during service period. Meanwhile, the effect of biochar replacing cement in mass ratio on the mechanical properties of concrete was studied. On this basis, the CO₂ emission for 1 m³ C30 biochar concrete were calculated and compared with that of ordinary C30 concrete. The results show that biochar is a carbon negative material and the higher carbon content, the better the CO₂ reduction effect. When the replacement rate of biochar is less than 5.0%, the ultrafine carbon particles after grinding can give full play to the filling and internal curing effects and effectively improve the mechanical properties of concrete. The life-cycle CO₂ emission of biochar concrete decreases with the increase of biochar replacement rate. Compared with ordinary C30 concrete, the CO₂ emission of 1 m³ wood biochar concrete with 5% replacement rate can reduce 66.5 kg CO₂ emissions with a reduction rate of 20.7%. During the service period of biochar concrete, the absorption of CO₂ by carbonation accounts for 1.8%-2.5% of the total carbon emissions. However, due to the exponential growth of the specific surface area of concrete in the demolition and abandonment stage, the amount of carbonation absorption needs further study.