## 1 Introduction  
The incorporation of sustainable production methods into intensive vegetable farming represents a pivotal advancement in contemporary agriculture. This endeavor seeks to achieve a delicate equilibrium between the escalating need for food and the imperative of environmental preservation [1]. Conventional intensive farming practices, although proficient in bolstering crop yields, frequently engender severe environmental degradation. This degradation encompasses emissions of greenhouse gases (GHGs), nitrogen (N) runoff culminating in eutrophication, the depletion of natural resources, and soil acidification and degradation [2]. In pursuit of agricultural methodologies that bolster food security while curtailing ecological footprints, organic alternatives and the application of biochar emerge as prominent candidates. Their potential to enhance soil quality and alleviate environmental challenges underscores their significance [3; 4]. The organic substitution strategy is widely regarded as one of the most effective methods for mitigating negative environmental impacts. Not only does it enhance the environmental quality of ecosystems, but it also bolsters product competitiveness in intensive vegetable production [5]. While organic substitution garners attention, there is growing acknowledgment of the indispensable role of biochar application in mitigating the environmental impact of agriculture [6]. Biochar is a stabilized form of carbon produced by the pyrolysis of biomass, and its high porosity and large surface area improves soil structure, water retention, and nutrient availability, in addition to its ability to enhance crop resistance, and thus crop yields, by boosting the concentration of available cations [7; 8]. The inherent resistance of biochar to decomposition renders it a potent vehicle for carbon storage, thereby contributing to diminished atmospheric carbon dioxide levels [9]. Moreover, biochar augments soil N fixation capacity, thereby curbing N loss and GHG emissions [10]. The primary objectives of agricultural production are to achieve the lowest environmental damage costs (EDCs) and the highest net economic benefits (NEBs). NEB indicates crop production avenues minus the purchase cost of agrochemical inputs. EDC refers to the costs associated with the reduced quality of environmental service functions due to Nr losses, including N footprints and GHGs from natural or anthropogenic activities [11]. From a life cycle assessment perspective, in addition to the significant emissions from on-farm applications, the production and transportation of agrochemical inputs, as well as the associated energy consumption, indirectly generate Nr and GHGs [12; 13]. Net ecosystem economic benefit (NEEB), defined as the difference between NEB and EDC from crop production, has thus become widely used to assess the sustainability of agricultural practices [14]. However, the comprehensive assessment of the impact of organic substitution and biochar addition on NEBs on the ecosystem, integrating production costs, crop yields, and environmental damages in intensive vegetable production, remains relatively unexplored. Our previous preliminary 5-year field observations and empirical modeling results indicated that organic substitution and biochar addition increased NEEB by increasing crop yields and reducing reactive N losses compared to synthetic N fertilizer alone [3]. In view of the role of biochar in carbon storage, particularly its capacity to sequester organic carbon over long time, this presents a significant opportunity for climate change mitigation and the enhancement of soil fertility and structure [15]. While existing studies have demonstrated the environmental and economic benefits of biochar in agricultural production, the reassessment of the quantitative NEEB of carbon storage benefits is still deficient. The long-term contribution of carbon sequestration has not been adequately considered in the calculation of NEEB, which may underestimate the role of biochar in agricultural sustainability [16].