## 4 Discussion  
Our newly revised framework incorporates the storage of organic carbon and spans the lifetime of biochar incorporation in the field. Biochar, as a multifunctional soil amendment, not only improves soil quality and crop yields, but also possesses a unique carbon storage function, which give it a huge potential, making it essential for combating climate change and achieving sustainable agriculture [28; 29]. Considering the multiple benefits of biochar, we conclude that biochar is superior to organic substitution in terms of improved benefits and reduced EDC, emerging as the most beneficial practice for NEEB in intensive vegetable production. This finding is consistent with the findings of [PERSON] and [PERSON] [30], who emphasized the potential of biochar for improving the economic viability and environmental desirability in agricultural systems. However, this is contrary to our previous preliminary results that we have found that NEEB was significantly better with organic substitution than with biochar addition and that the NEEB was lower with combined application compared to N fertilizer alone. The primary reason for this contradiction is that the study's inclusion of carbon benefits in the NEEB assessment framework resulted in  
Figure 4: Costs, gains and NEEB under different treatments in intensive vegetable production. Different lowercase letters represent significant differences in total costs and total gains, and different uppercase letters represent NEEB (\(p<0.05\)). CK: no fertilizer or biochar addition; SN: synthetic fertilizer application); NB: SN plus 20 t ha\({}^{-1}\) biochar amendment; NM: substituting 50% of chemical N fertilizer with organic manure; NMB: NM plus 20 t ha\({}^{-1}\) biochar amendment. significantly higher carbon benefits for the NMB treatment compared to the SN treatment. Thus, NEEB was superior to the SN treatment, which suggests that biochar's ability to sequester carbon makes it uniquely suited for agricultural production. When added to the soil, it is able to conserve carbon stably over a long period of time, thus creating a \"carbon sink\" in the farmland [31]. Unlike conventional organic substitutes, biochar can be stabilized in the soil for decades or even centuries, meaning that it can effectively convert atmospheric CO\({}_{2}\) into stable carbon in the soil. This long-term carbon sequestration not only helps mitigate climate change, but also creates additional financial gains for farmers in the carbon trading market [16]. In contrast, while organic matter can increase the SOC content of the soil in the short term, it decomposes more rapidly, and the carbon it fixes is quickly re-released into the atmosphere. Therefore, from the perspective of long-term carbon sequestration benefits, organic alternatives are less beneficial than biochar. In addition, the multiple benefits of biochar include its positive impact on soil microbial communities. Studies have demonstrated that biochar can provide a favorable habitat for beneficial microorganisms in the soil, promoting their activity and diversity [32]. These microorganisms play a crucial role in breaking down organic matter, recycling nutrients, and enhancing crop disease resistance, thus indirectly increasing agricultural productivity and soil carbon sequestration rates [33]. In contrast, while organic alternatives can also improve the soil microbial environment, their effectiveness is limited by the rapid and unstable decomposition of organic matter compared to biochar. Therefore, we believe that biochar is most beneficial to NEEB in intensive vegetable production because of its long-term stability and multifunctionality, making it a more promising strategy for sustainable agricultural management. For the ultimate NEEB, biochar was higher than the organic substitution, but the difference was not significant. This lack of significance can primarily be attributed to the relatively elevated input costs associated with biochar application, which poses a significant barrier to its widespread adoption [3].