Biodiesel has a lower oxidation stability index (OSI) than mineral diesel fuel. Its consequential oxidation products and deteriorated physical and chemical properties of fuel are associated with engine operation challenges such as the formation of insoluble gums that can plug fuel filters. Given the fact that oxidation leads to barriers for commercial use of biodiesel, addition of appropriate antioxidants into biodiesel is a promising and cost-effective approach to overcome this challenge. Although synthetic antioxidants such as propyl gallate (PG) are frequently used to counter the oxidation process of biodiesel, PG is a designated carcinogen. In light of that, this study was conducted aiming at introducing walnut husk methanolic extract (WHME) as a more sustainable antioxidant to replace PG in waste cooking oil (WCO) methyl esters. Moreover, to facilitate the commercialization of the new product, a comprehensive environmental investigation and comparison with the conventional counterpart, i.e., PG, was performed using life cycle assessment (LCA) approach. To enhance the eco-friendly features of the natural antioxidant, a solar photovoltaic-driven extraction process based on methanol (as reagent) was used in extracting polyphenols from walnut husk. The results showed that the induction period of WCO methyl esters was prolonged from 1.2 h to more than 3 h (meeting the ASTM D6751 standards) using 5000 ppm and 250 ppm of WHME and PG, respectively. More specifically, 20-fold more natural antioxidants would be required to meet the international standards. However, since walnut-producing countries are responsible for 42.4% of global biodiesel production on one hand and the cost-effectiveness of walnut husks on the other hand, their valorization could attract the attention of the global biodiesel industry. Moreover, this study highlights the considerable environmental and health benefits of turning this bio-waste product into a value-added antioxidant fuel additive. The LCA results showed that the developed bio-antioxidant was more effective in different damage categories compared with PG, i.e., 0.32% in ecosystem quality, 12.13% in human health, 8.37% in climate change, and 614% in resource. Overall, the WHME obtained through solar photovoltaic-driven extraction process could outcompete PG from the environmental perspective.

生物柴油的氧化稳定性指数（OSI）比矿物柴油低。其随之而来的氧化产物以及燃料的恶化的物理和化学性质与发动机的运行挑战有关，例如形成不溶性树胶会堵塞燃料过滤器。考虑到氧化会导致生物柴油商业化使用的障碍，在生物柴油中添加适当的抗氧化剂是克服这一挑战的一种有前途且具有成本效益的方法。尽管经常使用合成抗氧化剂，例如没食子酸丙酯（PG）来对抗生物柴油的氧化过程，但PG是指定的致癌物。有鉴于此，本研究旨在引入核桃壳甲醇提取物（WHME）作为更可持续的抗氧化剂，以代替废食用油（WCO）甲基酯中的PG。而且，为了促进新产品的商业化，使用生命周期评估（LCA）方法进行了全面的环境调查，并与传统的同类产品PG进行了比较。为了增强天然抗氧化剂的环保特性，使用了基于甲醇（作为试剂）的太阳能光伏驱动的提取工艺，以从核桃壳中提取多酚。结果表明，分别使用5000 ppm和250 ppm的WHME和PG，WCO甲酯的诱导期从1.2 h延长至3 h以上（达到ASTM D6751标准）。更具体地，将需要超过20倍的天然抗氧化剂才能达到国际标准。但是，由于核桃生产国承担了42个责任。一方面，全球生物柴油产量占全球的4％，另一方面，核桃壳具有成本效益，它们的增值可能引起全球生物柴油行业的关注。此外，这项研究还强调了将这种生物废物产品转变为增值抗氧化剂燃料添加剂的巨大环境和健康益处。生命周期评估的结果表明，与PG相比，已开发的生物抗氧化剂在不同的损害类别上更为有效，即生态系统质量为0.32％，人类健康为12.13％，气候变化为8.37％，资源为614％。总体而言，从环境角度来看，通过太阳能光伏驱动的提取工艺获得的WHME可能会超过PG。这项研究强调了将这种生物废物产品转变为增值抗氧化剂燃料添加剂的巨大环境和健康益处。生命周期评估的结果表明，与PG相比，已开发的生物抗氧化剂在不同的损害类别上更为有效，即生态系统质量为0.32％，人类健康为12.13％，气候变化为8.37％，资源为614％。总体而言，从环境角度来看，通过太阳能光伏驱动的提取工艺获得的WHME可能会超过PG。这项研究强调了将这种生物废物产品转变为增值抗氧化剂燃料添加剂的巨大环境和健康益处。生命周期评估的结果表明，与PG相比，已开发的生物抗氧化剂在不同的损害类别上更为有效，即生态系统质量为0.32％，人类健康为12.13％，气候变化为8.37％，资源为614％。总体而言，从环境角度来看，通过太阳能光伏驱动的提取工艺获得的WHME可能会超过PG。气候变化占37％，资源占614％。总体而言，从环境角度来看，通过太阳能光伏驱动的提取工艺获得的WHME可能会超过PG。气候变化占37％，资源占614％。总体而言，从环境角度来看，通过太阳能光伏驱动的提取工艺获得的WHME可能会超过PG。