National Research Centre, Water Pollution Research Department, 12622, Dokki, Cairo, Egypt.
Department of Smart-city Engineering, Inha University, 100 Inharo, Nam-gu, Incheon, 22212, South Korea.
Environ Res. 2022 Sep;212(Pt D):113494. doi: 10.1016/j.envres.2022.113494. Epub 2022 May 31.
Onion skin waste (OSW) is common waste in developing countries, which can cause severe environmental pollution when not properly treated. Value-added products can be chemically extracted from OSW; however, that process is not economically feasible. Alternatively, dry anaerobic digestion (DAD) of OSW is a promising approach for both energy recovery and environment protection. The main hurdles during DAD of OSW can be the hydrolysis and acidification. In batch tests, sludge digestate (SD) rich with methanogens was co-digested with different fractions of OSW for enhancing hydrolysis and raising biogas productivity. The cumulative biogas production (CBP) was 36.6 ± 0.3 mL for sole DAD of SD (100% SD) and increased up to 281.9 ± 14.1 mL for (50% SD: 50% OSW) batch. Self-delignification of OSW took place by SD addition, where the lignin removal reached 75.3 ± 10.5% for (85% SD: 15% OSW) batch. Increasing the fraction of OSW (45% SD: 55% OSW) reduced the delignification by a value of 68.8%, where initial lignin concentration was 9.48 ± 1.6% in dry weight. Lignin breaking down resulted a high fraction of phenolic compounds (345.6 ± 58.8 mg gallic acid equivalent/g dry weight) in the fermentation medium, causing CBP drop (219.0 ± 28.5 mL). The presence of elements (K, Ca, Mg, Fe, Zn, Mn, S and P) in OSW improved the enzymatic activity, facilitated phenolic compounds degradation, shifted the metabolism towards acetate fermentation pathway, and raised biogas productivity. Acidogenesis was less affected by phenolic compounds than methanogenesis, causing higher H contents and lower CH contents, at batches with high share of OSW.
洋葱皮废物（OSW）是发展中国家常见的废物，如果处理不当，会造成严重的环境污染。OSW 可以通过化学方法提取增值产品，但该过程在经济上不可行。相反，OSW 的干法厌氧消化（DAD）是一种有前途的既能回收能源又能保护环境的方法。OSW 的 DAD 过程中的主要障碍可能是水解和酸化。在批处理测试中，富含产甲烷菌的污泥消化物（SD）与 OSW 的不同部分共消化，以增强水解并提高沼气生产力。单独进行 SD 的 DAD 时，累积沼气产量（CBP）为 36.6±0.3 mL（100% SD），当进行（50% SD：50% OSW）批处理时，CBP 增加到 281.9±14.1 mL。SD 的添加使 OSW 发生自脱木质素，木质素去除率达到（85% SD：15% OSW）批处理的 75.3±10.5%。增加 OSW 的比例（45% SD：55% OSW）降低了脱木质素的比例，达到 68.8%，初始木质素浓度为干重的 9.48±1.6%。木质素分解导致发酵介质中酚类化合物的含量很高（345.6±58.8 mg 没食子酸当量/g 干重），从而降低了 CBP（219.0±28.5 mL）。OSW 中元素（K、Ca、Mg、Fe、Zn、Mn、S 和 P）的存在提高了酶的活性，促进了酚类化合物的降解，使代谢向乙酸发酵途径转移，提高了沼气的生产力。与产甲烷菌相比，产酸菌受酚类化合物的影响较小，导致高比例 OSW 批次中 H 含量较高，CH 含量较低。
