Abstract Yerba mate (Ilex paraguariensis) is one of the most popular hot drinks in the world and might represent an opportunity for energetic valorization after its consumption. Alkaline pretreatment appears to be a potential strategy for unlocking cellulosic biofuels. Thereby, in this study, four alkaline agents were evaluated for improving yerba mate anaerobic digestion (AD): (1) sodium hydroxide (NaOH); (2) potassium hydroxide (KOH); (3) lime; and (4) sodium bicarbonate. Complete factorial design with center point repetition was chosen to evaluate all combinations of concentration of alkali (50, 125, and 200 galkaline agent kg−1dry yerba mate), reaction time (12.2, 30.1, and 48 h) and temperature (30, 65, and 100 °C) in carbohydrate solubilization (variable response). Pre-treatment harshness was quantified by the modified severity factor (MSF). The methane production potential was determined for the best pretreatment condition achieved for each alkali tested. Energy balance for assessing the effectiveness of the proposed treatments on net energy gain was performed. NaOH and KOH had the same effect on organic matter solubilization and produced the same optimum value for the MSF. Thermal-alkaline pretreatment of yerba mate can increase the methane yield up to seven-fold as compared to control (maximum cumulated methane yield of 700 N-LCH4.Kg-VS−1added). All of the alkalis evaluated in the yerba mate pretreatment improved the kinetics of the AD process (kh; from 1e−5 to 1e−1 d−1). NaOH pretreatment at its highest levels of alkali concentration and temperature and lowest level of reaction time was found to be the best scenario in terms of net energy gain.

中文翻译：

---

马黛茶 (Ilex paraguariensis) 废物的碱性预处理，以解锁低成本纤维素生物燃料

摘要 Yerba mate (Ilex paraguariensis) 是世界上最受欢迎的热饮之一，可能是饮用后恢复精力充沛的机会。碱性预处理似乎是解锁纤维素生物燃料的潜在策略。因此，在本研究中，评估了四种碱性试剂以改善马黛茶厌氧消化 (AD)： (1) 氢氧化钠 (NaOH)；(2)氢氧化钾(KOH)；(3) 石灰；(4) 碳酸氢钠。选择具有中心点重复的完整因子设计来评估碱浓度（50、125 和 200 加碱剂 kg−1 干马黛茶）、反应时间（12.2、30.1 和 48 小时）和温度（30、65 , 和 100 °C) 在碳水化合物溶解（可变响应）中。治疗前的严酷程度通过修正的严重程度因子 (MSF) 进行量化。对于每种测试的碱所达到的最佳预处理条件，确定了甲烷生产潜力。进行能量平衡以评估提议的治疗对净能量增益的有效性。NaOH 和 KOH 对有机物增溶作用相同，MSF 的最佳值也相同。与对照相比，马黛茶的热碱性预处理可以将甲烷产量提高多达七倍（最大累积甲烷产量为 700 N-LCH4.Kg-VS-1 加入）。在马黛茶预处理中评估的所有碱都改善了 AD 过程的动力学（kh；从 1e-5 到 1e-1 d-1）。就净能量增益而言，在其最高碱浓度和温度以及最低反应时间水平的 NaOH 预处理被认为是最佳方案。