水热炭特性及强化厌氧发酵潜力研究进展

耿 涛,赵立欣,姚宗路,申瑞霞,于佳动,罗 娟

水热炭特性及强化厌氧发酵潜力研究进展

耿 涛,赵立欣*,姚宗路,申瑞霞,于佳动,罗 娟

(中国农业科学院农业环境与可持续发展研究所,农业农村部华北平原农业绿色低碳重点实验室,北京 10081)

厌氧发酵技术可以对作物秸秆,畜禽粪便,市政污泥等有机废弃物进行清洁转化,生成的沼气,沼渣和沼液在能源,农业,环保等领域有极大的应用价值.但目前厌氧发酵技术仍存在停滞期长,发酵过程中微生物活性受氨氮和有机酸等代谢产物与微塑料,酚类等有毒物质抑制,沼气中甲烷含量低等问题.水热炭是生物质在高温密闭环境以及亚临界水的作用下发生热化学反应得到的固体产物,具有丰富的孔隙结构和表面含氧官能团,是一种新兴的多功能炭基材料.厌氧发酵体系中适量添加水热炭能够有效缩短停滞期,缓解不同物质的抑制效应,促进微生物种间电子传递,增强甲烷生成等,具有综合的强化效果.对水热炭理化特性以及水热炭强化厌氧发酵的作用方式与机理进行了解,有利于进一步开展水热炭强化厌氧发酵以及农业废弃物高效厌氧处理的研究与应用.

农业废弃物；生物质；厌氧发酵；水热炭；产甲烷

厌氧发酵是一种用于处理作物秸秆,畜禽粪便,厨余垃圾等有机废弃物的成熟技术,有机物在微生物的协同代谢作用下经过水解、酸化、产乙酸、乙酸裂解和氢营养型产甲烷实现稳定化[1].发酵产物沼渣,沼液,沼气,可用于清洁能源生产,土壤改良等[2-4].厌氧发酵技术为实现能源的可再生与废弃物的有效管理提供技术支持.作为一种以微生物为驱动主体的生化反应,微生物代谢活性决定了厌氧发酵体系的运行效率,发酵过程中底物降解难易程度,发酵环境,功能菌丰度等因素都会对厌氧发酵产生重要影响[5].

水热炭是一种以生物质材料为原料,制备工艺温和简单的新兴炭基材料,具有一定的酸碱性,表面孔隙结构复杂多样,官能团种类及数量丰富,在土壤改良,污染物吸附,储能材料制备等领域有较大应用潜力.厌氧发酵体系中添加水热炭可以缩短停滞期,构建功能菌种间电子传递途径,有效增强厌氧发酵过程中产酸细菌与产甲烷古菌间的互营代谢,提高功能菌丰度,增强体系稳定性,强化甲烷生成,对厌氧发酵体系有综合强化效果[6-8].

本文主要聚焦废弃生物质制备水热炭,对水热炭理化特性以及水热炭强化厌氧发酵的研究现状进行总结和梳理,进一步指出目前水热炭在厌氧发酵强化的局限性并对未来发展方向进行展望,旨在对有机废弃物的高效处理以及水热炭在厌氧发酵强化方向的研究与应用提供一定助力.

1 废弃生物质水热炭化

水热炭化指将废弃生物质原料(作物秸秆,畜禽粪污,市政污泥等)投入到密封反应装置中,生物质在相对温和的温度条件(180～250℃),自生压力(2～8MPa)以及亚临界水的作用下经过水解,解聚,缩合等关键步骤实现炭化[9-10].亚临界状态下,水的极性,酸碱性,黏度发生明显改变,传热与传质能力显著增强,可对生物质原料进行深度渗透与炭化[11].与传统炭化技术比较,水热炭化无需对反应原料进行提前干燥,反应介质简单易得,温和的反应条件在降低能耗的同时使得材料表面官能团种类与数量更为丰富,具有较大的应用潜力.

反应温度,停留时间,升温速率,反应物浓度等因素都会对生物质水热炭化过程,最终产物分布与品质产生影响[12].温度是其中的关键参数,对反应过程与产物特性起着主导作用.随反应温度升高,水热炭产率显著降低,材料炭化程度,热稳定性,芳香化程度与能量密度皆随温度升高逐渐提高[13-16].

种植废弃物是水热炭制备的重要原料来源,木质纤维素是种植废弃物的主要成分,由木质素(9%～29%),纤维素(33%～47%)和半纤维素(21%～ 32%)组成[17].其中纤维素与半纤维素热稳定性较差,在较低的温度条件(200℃)即开始炭化.木质素作为一种非晶态杂聚物,其复杂成分与结构需要300℃以上的温度才开始炭化,并且木质素的组成分子广泛交联形成植物细胞壁的稳定骨架,对纤维素和半纤维素形成包裹,阻碍木质纤维素的炭化反应[18].木质纤维素材料这种组成与结构特性使得水热炭化过程中不同成分与反应途径相互作用,水热炭的形成机理更加复杂(图1).

图1 木质纤维素生物质水热炭化演化路径[19]

2 水热炭理化特性

2.1 表面形貌与孔隙结构

木质纤维素水热炭比表面积一般在1.09～ 52.86m2/g,孔隙度0.02～0.97cm3/g,平均孔径0.086～ 17.48nm,主要以介孔为主.木质纤维素原料在水热反应过程中,表面成分不断溶出并与其他物质反应,对材料表面形成剥蚀,覆盖并产生碳微球结构,塑造水热炭表面形貌[20];水热反应过程中挥发性物质产生气体排放效应使得水热炭表面形成孔隙[21].水热炭的表面形貌与孔隙特征主要受反应温度与停留时间的影响(图2).随着反应温度升高,炭材料表层会逐渐破碎,材料孔隙度增大并且表面碳微球增多[15,22];碳微球的直径随温度升高先增大后减小,随温度升高或停留时间的延长水热炭表面碳微球发生黏连,形态也逐渐不规则[23].高温下生物油中组分沉积会掩埋材料表面孔隙,阻碍材料表面孔隙结构发展,使水热炭表面变得平滑致密[24].

图2 松树皮,秸秆,纤维素水热炭SEM图像[10,16,23]

2.2 表面含氧官能团

生物质原料不完全炭化以及水热反应过程中物质的生成使得水热炭表面官能团的种类和数量得到丰富,底物类型与工艺条件都对水热炭表面官能团起影响作用(表1).水热炭化后材料表面的含氧官能团数目较原材料增加,并且含氧官能团的数量随温度升高呈现先增加后减少的趋势[25-28].Liu等[29]发现松木经过300℃水热炭化后,水热炭表面含氧官能团可增加95%.炭化过程中,纤维素,半纤维素热稳定性较差,在较低温度下即发生分解并进行反应,随着脱水脱羧发生,—OH,—CO等官能团减少;木质素热稳定性较强,在高温下才开始反应,形成水热炭骨架,随着芳构化反应的进行,材料表面C=C,C=O官能团增多[24].水热炭表面官能团在污染物吸附,土壤结构调控,材料储能等方面都发挥重要作用,选取合适原料与炭化工艺实现功能性材料的获取是水热炭应用的关键.

2.3 pH值

木质纤维素材料在水热炭化过程中生成有机酸与碳酸,同时高温下木质素分解产生酚类物质也会影响水热炭的pH值.水热炭的pH值受原料特性及制备温度影响[30].水热炭化过程中,温度升高导致材料脱水脱羧作用加剧,同时高温下水相中OH-与水热炭表面酸性官能团加速结合,导致水热炭表面酸性含氧官能团脱落转移,液相中的酸性物质的合成增加,水热炭pH值升高.李金铭等[31]发现水热炭表面弱酸性与材料表面含氧官能团含量有关.Liu等[29]认为水热炭的pH值与材料表面丰富的羧基官能团有关.

2.4 水热炭改性

为了更好地增强水热炭的功能性,可采用不同改性手段对水热炭理化特性进行优化.目前,水热炭改性的方式按照改性步骤可分为一步法或两步法,按照改性方法可分为物理改性,化学改性和生物改性.

2.4.1 物理法 物理改性具有廉价,不使用化学药剂,没有二次污染的优点,改性方法包括高温气体活化,球磨,高温或冻融循环等.谢伟玲,刘宇等[27]和谢伟玲[32]发现水热炭经高温活化后比表面积与孔隙度显著增大且孔径缩小,含氧官能团丰度一定程度上降低. Huang等[33]发现水热炭经过混合气体高温活化以后,水热炭材料微孔与比表面积增加,比表面积从7.5m2/g增至618.02m2/g.球磨法则通过物料间研磨与碰撞使炭材料粒径细化至纳米级别,增大材料比表面积并且通过破坏或者拉伸大分子化学键,在材料表面增加新的官能团[34].He等[35]使用球磨法对水热炭改性后,发现表面O—H,C—O官能团增加.关俊杰[36]将稻壳和玉米秸秆分别在70℃和-25℃进行高温和冻融循环老化,发现两种老化方法都可以使水热炭表面—OH,C=C,C—OH显著增多,其中冻融老化效果更加显著.

2.4.2 化学法 化学改性按照使用化学试剂类型可以分为酸碱改性,金属盐改性,有机物改性,过氧化物改性;按照处理方式则可以分为化学处理,水热添加剂,水热后处理等.化学改性可以有效改变水热炭材料表面形貌,官能团特性并且实现金属,氮,磷等元素的掺杂,显著增强水热炭功能性.

(1)酸碱改性.酸改性可以溶解水热炭表面金属盐等无机成分,降低水热炭灰分,在材料表面引入酸性官能团并对表面形貌有一定改良作用.谢伟玲[32]通过H3PO4对水热炭进行一步改性,使得水热炭表面官能团种类与数量得以丰富,水热炭对水体中Pb(Ⅱ)的去除率提高28.3%;分别以盐酸,硝酸,硫酸和毛竹共混合进行水热炭化,发现改性水热炭孔隙结构并未优化但是在材料表面发现氯元素,氮元素和硫元素.Li等[41]用硝酸对杨木屑水热炭进行浸渍改性后,材料比表面积最高提高5.6倍且含氧官能团丰度提高.碱改性通过强碱物质腐蚀,清除水热炭表面覆盖物,促进材料孔隙发育,增强材料芳构化程度.刘宇等[27]使用KOH对水热炭进行改性,优化材料表面形貌与孔隙结构,改性后水热炭对水体中PFOS的吸附量最高提升近1000倍.

表1 水热炭官能团特性变化

(2)金属盐改性.使用金属盐对水热炭进行改性,不仅优化材料表面形貌及官能团特性,而且金属元素的附着可以增强水热炭的功能性,例如通过铁盐改性实现水热炭表面铁元素附着,增强材料在污水处理,厌氧强化等方面的效果,并且在外加磁场的作用下实现材料的分离与再利用[42].段佳男[43]以FeCl3溶液为反应介质制备稻壳改性水热炭,铁盐改性水热炭比表面积和孔容明显增加.孙畅[44]以FeCl3溶液为反应介质进行米糠改性水热炭制备,材料比表面积和孔隙度分别提高60.49%与32.71%,表面碳微球更加丰富同时实现了铁元素附着.严伟等[45]发现KMNO4改性后水热炭表面存在锰氧化物.王曦等[46]使用NH4H2PO4溶液作水热反应介质进行改性水热炭制备,改性后,水热炭表面N元素增加,总孔体积显著缩小;—COOH,C=O, C=C,C—O官能团增多,—CH减少,在水热炭表面掺入含氮官能团.

(3)有机物改性.有机物改性使水热炭表面形貌发生改变,增强水热炭芳香性,增加材料碳元素含量并且可以通过交联等方式引入新的元素.孙迎超[47]以柠檬酸溶液为反应介质对玉米芯与松子壳进行水热炭化,改性后材料含氧官能团与表面碳微球都有所增加.杨正武[48]以丙酮溶液为反应介质对小麦秸秆进行水热改性,改性后水热炭孔隙结构得到优化.段佳男等[43]以葡萄糖对水热炭进行改性,改性后水热炭表面C=C,C—O官能团增加.谢伟玲[32]以聚乙烯亚胺对水热炭进行改性,两者发生交联作用,在水热炭表面引入含氮官能团.

(4)过氧化物改性.过氧化物具有强氧化性,对水热炭材料改性可以增加水热炭的氧含量并且丰富水热炭表面含氧官能团.Xue等[49]使用H2O2对花生壳水热炭进行浸渍改性,发现水热炭表面羧基,羰基等含氧官能团增多且氧元素含量增加.关俊杰等[50]发现H2O2改性可以在水热炭表面引入大量含氧官能团,增加材料中氧含量并降低碳含量.王曦[46]对木屑水热炭进行H2O2浸渍改性,改性水热炭C元素含量显著减少,O元素含量明显增加,材料亲水性与极性增强且内部形成大量不规则孔道,表面积与平均孔径增加,表面官能团种类与数量得到丰富.

2.4.3 生物法 生物改性也称“微生物陈化”,指微生物吸收利用水热炭表面有机物质并产生分泌物,使水热炭表面官能团与表面形貌发生变化.花昀[51]将麦秆和杨树锯末水热炭加入到厌氧发酵体系中陈化后发现水热炭孔隙结构,pH值,表面含氧官能团增加,水热炭的碳元素减少,而氧元素所占比例增加.胡子瑛[52]使用好氧细菌枯草芽孢杆菌对水热炭进行生物改性,发现改性后水热炭表面形成了许多非均质的裂缝和空洞,同时碳微球萎缩甚至消失,C—O—C,C=O等含氧官能团减弱.

2.4.4 混合法 除以上3种单一的改性手段,诸多研究将不同改性手段结合使得水热炭材料理化特性明显改善.混合改性可以在增强材料特性的同时减小改性造成的环境或成本负担.严伟[45]将毛竹与不同碱性试剂共水热后进行高温热解,材料比表面积与孔径显著增大,混合改性在减少强碱使用量的同时得到优质吸附性炭材料.郭大川[10]使用尿素溶液为反应介质进行松树皮水热炭制备后进行高温热解活化,所得改性材料平均孔径与氮元素明显增加,在表面氧元素含量基本不变的情况下将部分C—O键转化为C—N键,进一步增强了材料对溶液中镉的吸附性能.

3 水热炭强化厌氧发酵

近年来,水热炭在生物领域的应用成为新兴热点.厌氧发酵体系中添加适量水热炭可以缩短厌氧发酵的启动期,提高厌氧发酵沼气中甲烷的含量,增强发酵系统对酸,氨抑制等不良发酵环境的耐受性,有明显的强化厌氧发酵产甲烷效果(表2).Shi等[7], Leithaeuser等[53],Xu等[54]分别以玉米秸秆,污泥等为原料制备热解炭与水热炭进行比较研究,发现水热炭强化厌氧发酵产甲烷效果优于热解炭.为了探明水热炭强化厌氧发酵的作用机理,有研究借助代谢组学分析,宏基因组分析,元基因组分箱算法,同位素标记,荧光标记等技术和手段进行探索,提出水热炭对厌氧发酵的强化作用与炭材料表面含氧官能团丰度,供受电子能力等特性相关.目前水热炭强化厌氧发酵的主要作用途径包括:(1)缓解厌氧发酵体系物质抑制;(2)促进互营微生物间电子传递;(3)富集厌氧发酵功能微生物.

表2 水热炭对厌氧消化性能的影响

3.1 缓解厌氧发酵体系物质抑制

水热炭孔隙结构复杂且表面官能团丰富,可以和发酵体系中氨氮,酚类,微塑料等物质发生作用并进行吸附,同时刺激微生物产生胞外聚合物,减少微生物与抑制因子的接触,削弱其对发酵微生物的毒害,缓解发酵体系中的抑制效应(图3).

图3 水热炭对厌氧体系抑制效应的缓解作用

3.1.1 缓解氨抑制 畜禽胴体以及粪便等高含氮量底物在发酵过程中产生大量铵离子(NH4+)和游离氨(NH3),不仅对发酵过程中酶活性有抑制作用,而且游离氨进入细胞内改变细胞代谢过程,会对微生物产生毒害[55].水热炭可以对发酵体系中氨氮进行吸附并促进微生物对氨氮的转化.徐杰等[6]发现发酵体系中每克水热炭吸附约1.0～17.5mg氨氮,促进微生物对氨氮的转化同时提高发酵体系氨氮抑制的阈值. Usman等[5]发现厌氧发酵体系中水热炭对氨氮的吸附量达到40.98mg/g. Leithaeuser等[53]发现氨抑制体系中水热炭添加组甲烷产量较对照组增加17.30%.Wang等[56]发现KOH改性水热炭降低发酵体系中NH4+-N的含量并促进含氮化合物的降解.

3.1.2 缓解微塑料毒害作用 污水中微塑料(粒径<5mm)会抑制颗粒污泥胞外聚合物的分泌并导致污泥颗粒破碎,使发酵体系中微生物总量与功能菌相对丰度降低,发酵系统COD去除率与甲烷产率下降[63-64].水热炭可以吸附并累积发酵体系中的微塑料,促进厌氧微生物分泌腐殖酸,增加胞外聚合物生成,减少微塑料与微生物的直接接触,阻止微塑料对厌氧颗粒污泥中微生物产生毒性,增强发酵体系稳定性[65].

3.1.3 缓解酚类物质毒害作用 酚类有机物对厌氧发酵体系的抑制作用是当今有机废弃物高效处理的一个发展障碍.酚类物质具有毒性和腐蚀性,可以破坏微生物细胞膜并改变细胞通透性,抑制微生物活性.酚浓度过高甚至会导致体系中甲烷生成完全停止.He等[60]发现水热炭对厌氧发酵体系中酚类物质有明显的吸附作用并且可以刺激微生物分泌胞外聚合物,增强细胞结构,减少酚类物质对微生物的毒害,同时水热炭加强微生物对苯酚的降解作用,缓解发酵体系中酚抑制.

3.2 促进互营微生物间电子传递

厌氧发酵产甲烷是多种微生物协同实现的复杂生化反应,提高微生物胞外电子传递效率可以有效增强厌氧发酵过程中底物转化与甲烷生成(图4).发酵初期或体系有机负荷过高时,丙酸,丁酸等挥发酸无法及时消耗形成累积,发酵体系pH值下降,产甲烷功能菌活性受到抑制进而破坏整个体系的稳定性.水热炭可以增强发酵体系中微生物种间电子传递,促进微生物对底物的降解与转化,缓解厌氧发酵酸抑制.Shi等[7-8]发现水热炭对发酵体系中挥发酸降解与转化有促进效果并增强甲烷的生成,对发酵体系酸抑制有一定的缓解作用.Xu等[54]发现水热炭有效促进发酵体系中丙酸盐降解.

图4 厌氧发酵体系中微生物种间电子转移方式[72]

种间氢转移(IHT)曾被认为是厌氧发酵种间电子传递的主要方式,即在极低的氢分压(约0.1～10Pa)环境中,产甲烷菌消耗发酵性细菌产生的H2,还原环境中CO2并生成甲烷[66-67].但发酵体系中H2分子主要依靠扩散进行转移,电子转移效率极低,通过IHT产生的甲烷仅占总甲烷的4.7%[68].

厌氧发酵体系中微生物种间电子直接转移(DIET)是目前厌氧发酵领域的研究热点.已知的DIET构建途径主要有3种:①借助微生物导电鞭毛(Electrically conductive pili)与细胞外表面相关色素(Cytochrome C);②向体系中添加导电物质;③构建微生物电解池[1,5,69-70].DIET的电子传递效率可达IHT的106～108倍,是更加高效且稳定的电子传递方式,可以有效增强厌氧发酵体系性能[71].

水热炭借助表面含氧官能团发挥电子介体作用,构建厌氧发酵体系中功能菌DIET途径,加速产酸细菌与厌氧发酵功能菌对挥发酸的互营代谢,促进厌氧发酵体系甲烷生成[68].Shi等[7-8]结合微生物转录与代谢组学分析发现水热炭添加促进了厌氧发酵体系内维生素B6的代谢,使得微生物群落的代谢过程和活动受到了干扰;通过以基因组为中心的元转移组学对水热炭构建厌氧发酵DIET途径的方式进行探索,发现水热炭添加体系中和富集程度最高,这两种微生物可以参与DIET强化甲烷生成.Ren等[57]通过无标记蛋白质组学分析揭示参与DIET,进一步提出水热炭强化效果厌氧发酵与炭材料表面含氧官能团丰度呈正相关.He等[35]发现水热炭进行球磨改性后,材料表面C—O,O—H含氧官能团进一步丰富,对甲烷生成的促进效果优于未改性水热炭并且对和等可能参与DIET的微生物有富集作用.

3.3 富集厌氧发酵功能微生物

表3 水热炭对厌氧发酵体系中功能微生物群落演替作用

水热炭表面孔隙与官能团可以作为结合位点对厌氧发酵体系中功能微生物进行固定与富集,增强体系稳定性(表3).Xu等[62]探究水热炭对厌氧发酵不同环节的强化效果,发现水热炭显著富集与有机物水解,产酸,产甲烷相关的功能菌,明显改变发酵体系中微生物群落结构.He等[60]通过宏基因组分箱手段发现水热炭富集厌氧发酵功能微生物并促进甲烷生成的相关基因表达.Hurst等[61]发现水热炭使得厌氧发酵体系中Bacteroidetes与Firmicutes显著富集.Usman等[58]通过三维荧光激发发射矩阵分析发现水热炭添加后厌氧发酵体系中腐殖质,黄腐酸等难降解物质的浓度降低并推测水热炭改变厌氧发酵体系中微生物群落结构,实现对这些物质的降解.Yang等[72]发现水热炭使得发酵体系中Bacteroidetes,Firmicutes和Proteobacteria等微生物一定程度富集.

4 结语与展望

作为一种厌氧发酵外源添加剂,水热炭原料来源丰富,较纳米零价铁,活性炭等材料,制备成本低,工艺对环境影响小;而且水热炭表面孔隙,含氧官能团,电导率等特性在厌氧发酵体系中能够吸附毒害物质,富集功能微生物,提高微生物种间电子传递效率,有效缩短发酵停滞期,增强体系稳态并改善厌氧发酵产甲烷效果,有利于实现有机废弃物的高效消纳与利用.深入了解水热炭强化厌氧发酵的作用方式,探索厌氧发酵过程中物质转化路径与关键微生物间互营机制,实现对发酵过程及产物分布的有效调控,促进有机废弃物向甲烷等产物转化,提高厌氧发酵技术对自然环境中复杂混合物和毒害废弃物的处理水平,扩大厌氧发酵技术的应用规模,增强有机废弃物消纳与利用能力.生物质厌氧发酵与水热炭化一体化工艺具有良好的经济可行性和环境效益,有助于构建有机废弃物清洁处理的循环经济模式,沼气,水热炭等产物在环境,能源等发面都有良好的应用价值,能够实现有机废弃物的高效清洁处理与多元高值利用.

目前,水热炭强化厌氧发酵的作用机制与相关应用工艺仍无明确定论,建议在以下几点对水热炭强化厌氧发酵进行研究:

(1)从水热炭表面形貌,孔隙结构,表面官能团,供受电子能力,可降解性等角度对水热炭强化厌氧发酵的关键理化特性进行探索,进一步明确实现并强化该类特性的相关工艺与手段,为开发低成本高效率的厌氧发酵外源添加剂提供支持.

(2)结合水热炭添加体系中功能微生物群落演变情况与微生物种间电子传递不同途径对甲烷生成的贡献程度深入探索水热炭强化厌氧发酵产甲烷机制.

(3)结合厌氧发酵体系中水热炭添加量,材料老化与可重复利用性,沼液沼渣营养成分变化等方面对水热炭强化厌氧发酵的可持续利用性与后端产物应用途径进行探索.

(4)现有研究主要针对实验室规模水热炭强化批式厌氧发酵效果进行探究,需加强对水热炭强化中试规模以及实际沼气工程中连续厌氧发酵的效果研究以及水热炭结合其他厌氧发酵调控策略的耦合效果及作用方式研究.

(5)综合经济利益与环境效益等角度借助生命周期,技术经济评估等手段对生物质水热炭化与厌氧发酵技术结合处理有机废弃物的效果进行充分的评估,为水热炭强化厌氧发酵技术的推广应用提供充足理论支撑.

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Characteristics and potential to strengthen anaerobic digestion of hydrochar.

GENG Tao, ZHAO Li-xin*, YAO Zong-lu, SHEN Rui-xia, YU Jia-dong, LUO Juan

(Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Key Laboratory of Low-carbon Green Agriculture in North China, Ministry of Agriculture and Rural Affairs P. R. China. Beijing 100081, China)., 2023,43(10)：5170～5180

Anaerobic digestion (AD) offers an attractive method to reduce the negative impact of organic waste existing in the environment such as stalk, animal manure and municipal sludge. The biogas, digestate and slurry generated have great application value in energy, agriculture, environmental protection and other fields. However, AD has some problems such as the lag phase, the inhibition effect caused by ammonia nitrogen, VFA and so on, and low methane content in biogas. Hydrochar is the solid product of hydrothermal carbonization of biomass which is converted to porous multi-functional carbon-based material with the presence of subcritical water in the sealed equipment under the effect of heat and pressure. The potential benefits and applications of hydrochar have received significant attention with complex pore structures and high density of oxygen-containing functional groups. There is a comprehensive strengthening effect on AD including shortening the lag phase, alleviating the inhibition, favoring electron transfer between microbes, and enhancing the CH4production with the addition of hydrochar. Specifically, it was brought together recent advances made in the area through a systematic and critical review of the characteristics, modification, and strengthening effect on AD of hydrochar. The potential and limitations involved in the hydrochar application on AD were pointed out with suggestions for further research to exploit the great potential of AD on treating agricultural wastes.

agricultural wastes；biomass；anaerobic digestion；hydrochar；methanogenesis

X705;S216.4;TK6

A

1000-6923(2023)10-5170-11

2023-02-23

国家重点研发计划(2022YFD2002100);中央级公益性科研院所基本科研业务费专项(BSRF202221);中国农业科学院科技创新工程

* 责任作者, 研究员, zhaolixincaae@163.com

耿 涛(1995-),男,山西太原人,中国农业科学院研究生院硕士研究生,主要从事农业废弃物厌氧生物处理技术研究.发表论文1篇.gt0502@126.com.

耿 涛,赵立欣,姚宗路,等.水热炭特性及强化厌氧发酵潜力研究进展 [J]. 中国环境科学, 2023,43(10):5170-5180.

Geng T, Zhao L X, Yao Z L, et al. Characteristics and potential to strengthen anaerobic digestion of hydrochar [J]. China Environment Science, 2023,43(10):5170-5180.