好氧堆肥腐殖酸形成機制及促腐調(diào)控技術概述

常 遠,李若琪,李 珺,詹亞斌,魏雨泉*,許 艇,李 季

好氧堆肥腐殖酸形成機制及促腐調(diào)控技術概述

常 遠1,2,李若琪1,2,李 珺1,2,詹亞斌3,魏雨泉1,2*,許 艇1,2,李 季1,2

(1.中國農(nóng)業(yè)大學資源與環(huán)境學院,北京 100193；2.中國農(nóng)業(yè)大學有機循環(huán)研究院(蘇州),江蘇 蘇州 215100；3.湖北省農(nóng)業(yè)科學院,植保土肥研究所,湖北 武漢 430064)

基于堆肥腐殖酸形成機制,重點綜述了工藝參數(shù)優(yōu)化、外源添加劑等促進堆肥腐殖化進程的有效方法,系統(tǒng)地總結了各調(diào)控手段對堆肥腐殖酸形成過程的影響機理,旨在為堆肥快速腐熟調(diào)控技術發(fā)展提供理論依據(jù).由于堆肥過程是不斷波動變化的,多種調(diào)控手段在實際生產(chǎn)應用中并不能完全達到預期的效果.因此在堆肥實際生產(chǎn)應用中,應更多關注堆肥中與腐殖酸形成相關的因素或過程,進一步針對性地加強各種調(diào)控手段的研究并建立彼此之間的關聯(lián),優(yōu)化其在堆肥過程中的影響,以實現(xiàn)提高最終產(chǎn)品質(zhì)量的目標.

腐殖化；腐殖酸形成；快速腐熟；工藝參數(shù)；新型添加劑

2019年中國各類有機廢棄物產(chǎn)生量干重總計22.69億t[1].由于有機廢棄物產(chǎn)量巨大,其處理工藝一直是研究重點.有機廢棄物主要處理手段有:衛(wèi)生填埋、焚燒、好氧堆肥等技術[2].作為傳統(tǒng)處理工藝,填埋和焚燒不僅資源化程度低,而且對生態(tài)環(huán)境和人體健康造成了嚴重危害.相較于傳統(tǒng)處理技術,好氧堆肥因無害化處理率高、環(huán)境友好性、成本低等優(yōu)勢,逐漸發(fā)展成處理有機廢棄物實現(xiàn)肥料化的主要技術手段[3].好氧堆肥實質(zhì)是微生物主導有機物質(zhì)分解并通過降解和聚合生成穩(wěn)定腐殖酸等高附加值產(chǎn)品的腐殖化過程[4].腐殖酸作為堆肥終端產(chǎn)物,在土壤修復、改善植物生長及土壤肥力方面發(fā)揮著重要作用[5].傳統(tǒng)好氧堆肥依靠土著菌進行降解發(fā)酵,未添加任何生物菌劑或添加劑,堆肥溫度較低,周期長,一般1～3個月,產(chǎn)品質(zhì)量不穩(wěn)定.隨著有機廢棄物產(chǎn)生量逐漸增大,有機廢棄物堆肥處理效率要求愈來愈高,傳統(tǒng)好氧堆肥已經(jīng)不能滿足日益增長的有機廢棄物處理需求,因此快速堆肥應運而生.

快速堆肥是利用反應器、工藝優(yōu)化、外源添加劑等調(diào)控手段人為強化堆肥關鍵可控因素,促進腐殖化進程,縮短堆肥周期[6],一般僅1～3個星期.目前仍存在腐熟不充分、腐殖化效率低和產(chǎn)品質(zhì)量差等缺點[7].腐殖化過程通常被認為是含碳化合物積累和儲存的一種形式,是堆肥固碳的關鍵環(huán)節(jié).腐殖酸類物質(zhì)是有機廢棄物堆肥腐殖化過程的主要產(chǎn)物之一,腐殖酸數(shù)量和質(zhì)量直接影響堆肥腐熟度和產(chǎn)品質(zhì)量,促進堆肥腐殖酸穩(wěn)定形成,可有效加快堆肥腐殖化效率,提升堆肥品質(zhì).因此,在有機廢棄物堆肥無害化、減量化的基礎上,調(diào)控好氧堆肥腐殖酸形成已成為新興領域.然而,由于有機廢棄物來源廣泛、結構多樣,各類腐殖酸前體可能相互作用、彼此聯(lián)系,造成堆肥腐殖酸形成過程的復雜性與多樣性[8].因此深入研究堆肥腐殖酸形成機制、調(diào)控堆肥腐殖化進程并建立腐殖酸穩(wěn)定化調(diào)控方法極其必要,既符合農(nóng)業(yè)綠色發(fā)展中有機肥相關產(chǎn)業(yè)需求,也是國內(nèi)外研究的熱點和難點問題.

廣大學者對堆肥腐殖化調(diào)控的研究主要集中在改善堆肥環(huán)境、加強形成途徑,以達到加快堆肥腐殖化的目的[4],主流快速腐熟調(diào)控技術有:優(yōu)化工藝參數(shù)、外源添加劑.優(yōu)化堆肥工藝參數(shù)是最常見的調(diào)控技術,溫度、含水率、碳氮比(C/N)、pH值等都對堆肥腐殖化有直接影響[9].通過調(diào)節(jié)原始理化參數(shù)、協(xié)調(diào)原料配比、物化輔助加強等手段維持堆肥環(huán)境因子在最佳水平,有利于微生物生長代謝,促進堆肥腐殖化.添加外源添加劑是一種高效的促腐策略,包括常規(guī)強化添加劑和新型功能添加劑.微生物菌劑[10]、腐殖酸前體[11]、腐熟堆肥[12]等是堆肥中常用的外源強化添加劑,能直接加強腐殖酸形成途徑,促進腐殖酸形成,提高堆肥腐熟度.新型功能添加劑如生物炭、礦物質(zhì)等,不僅能調(diào)節(jié)堆肥環(huán)境如生物炭可增加堆肥C/N[13]、礦物質(zhì)可作為調(diào)節(jié)劑增加pH值[14],還能吸附堆肥腐殖酸形成有機無機復合體起到保護作用[15],綜合了前兩種促腐調(diào)控技術的優(yōu)勢.同時由于這類物質(zhì)在高溫下具有較強的穩(wěn)定性,與熟料混合還可提高堆肥產(chǎn)品的附加值,因此被稱為新型功能添加劑.上述調(diào)控手段通過不同的促腐殖化機理,共同促進了快速堆肥技術的發(fā)展.

本文系統(tǒng)概述了堆肥腐殖酸形成途徑、多種快速堆肥腐殖化進程調(diào)控技術及其機制,以尋求處理效率高、經(jīng)濟效益好且環(huán)境友好的快速堆肥技術,為建立堆肥腐殖酸穩(wěn)定化機制、提高堆肥效率和產(chǎn)品質(zhì)量提供重要的理論基礎,促進有機廢棄物資源化利用快速發(fā)展.

1 堆肥腐殖酸及其形成機制

腐殖酸作為堆肥的重要次生產(chǎn)物,其主要包括胡敏酸(HA,堿溶酸不溶)和富里酸(FA,酸溶堿不溶)兩種組分.胡敏酸分子量大且結構復雜縝密,主要以芳香化合物為主,芳香化程度高而解離程度小;富里酸分子量小且結構簡單松散,主要以烷烴類化合物為主,含有較多的羥基和羧基.完整的腐殖酸大分子主要通過這兩種化合物結合而成,基本結構以芳環(huán)和脂環(huán)為主,環(huán)上連有羧基、酚羥基、醇羥基、羰基、醌和甲氧基等多種基團[16],同時結構表面還存在糖類、木質(zhì)素單體、酚酸和脂肪酸以及大量的非木質(zhì)素來源的芳香族化合物,豐富的結構表面賦予了腐殖酸生物活性[17].在堆肥過程中,微生物通過分解有機質(zhì)或自身合成釋放出含有上述基團的小分子有機化合物,這些多功能有機化合物通過隨機氧化、疏水作用、電荷轉移、氫鍵等方式聚合或縮合形成腐殖酸[16].

堆肥腐殖酸形成機制的研究起源于土壤腐殖質(zhì)的研究,堆肥類似于土壤腐殖化的一個快速過程[18].堆肥中有機組分(蛋白質(zhì)、多糖、脂質(zhì)和木質(zhì)素)轉化與降解過程中形成的小分子化合物(多酚、羧基、脂肪酸、糖類以及氨基酸等化合物)被稱為腐殖酸前體[19].不同前體分子對腐殖質(zhì)形成具有不同的影響:芳香族結構的多酚和羧基化合物對HA的形成有明顯的促進作用,而氨基酸、多糖和還原糖等烷烴類化合物則主要影響FA的形成[20].因此腐殖酸形成并不是前體生物分子單體間的簡單加和,多種不同來源的前體物彼此間需通過一定機制才能最終聚合成腐殖酸大分子.

1.1 以非生物途徑為主的形成機制

經(jīng)過多年腐殖酸合成途徑研究逐漸形成了多種腐殖酸形成機制假說(圖1),其中以非生物途徑為主的形成機制假說包括木質(zhì)素-蛋白學說、多酚-蛋白假說、多酚自縮合以及美拉德反應[21-23].木質(zhì)素-蛋白學說強調(diào)不完全分解的木質(zhì)素轉化形成具有酚羥基和羧基基團的分子,進而作為腐殖酸核心骨架與含氮化合物聚合形成腐殖酸.由于這類含氮化合物存在形式主要是蛋白質(zhì)和氨基酸,故又有學者提出類似的多酚-蛋白質(zhì)假說,認為酚、醌以及氨基酸等是構成腐殖酸骨架的核心物質(zhì)[24].多酚-蛋白假說與木質(zhì)素-蛋白學說高度相似,但多酚-蛋白假說涵蓋范圍更廣、適用性更強[11].多酚除了和含氮化合物聚合形成腐殖酸外,其還可通過環(huán)斷裂與其他酚類化合物縮合形成腐殖酸,即所謂的多酚自縮合[25].美拉德反應則與上述機制不同,主要強調(diào)糖和氨基的作用,還原糖和氨基酸之間的縮合被認為是堆肥初期腐殖酸形成的主要原因,且此過程沒有酶和酚的參與[26].由此看出腐殖酸形成途徑相互獨立,但多種腐殖酸前體相互作用又使得各腐殖酸形成途徑在堆肥環(huán)境中彼此聯(lián)系,因此往往多種非生物途徑共同作用于腐殖酸形成.

1.2 以生物途徑為主的形成機制

堆肥腐殖化是一個復雜的微生物主導的生物生化過程,有機質(zhì)分解和腐殖酸形成是微生物活動的結果[27].堆肥中微生物活動主要存在分解(有機物礦化)和合成(腐殖酸形成)兩種代謝路徑[28].兩種路徑共同作用,相輔相成,確保腐殖化過程的順利進行.堆肥中微生物合成腐殖酸強調(diào)以生物途徑為主(圖1),主要涉及微生物合成假說、微生物多酚學說、細胞自溶學說及活性氧(ROS)理論.微生物合成假說認為微生物利用植物物質(zhì)作碳源和能源在細胞內(nèi)合成高分子腐殖質(zhì)物質(zhì),微生物死亡后再釋放到土壤中,在細胞外再降解為HA和FA[25].微生物多酚學說強調(diào)微生物合成的多酚在微生物分泌的酚氧化酶作用下氧化成醌,最終與含氮化合物縮合形成腐殖酸.細胞自溶假說則認為腐殖物質(zhì)是植物和微生物死亡之后的自溶產(chǎn)物,原先的細胞成分,如糖、氨基酸、酚和其他芳香族化合物通過自由基進行縮合和聚合而成.此外,最近的研究表明,ROS在堆肥腐殖酸形成過程中起到關鍵作用,微生物通過在交替有氧和厭氧條件下介導鐵或腐殖質(zhì)氧化還原循環(huán)的耦合過程,產(chǎn)生的羥基自由基(·OH)、超氧陰離子自由基(·O2?)、過氧化氫(H2O2)等活性氧物質(zhì)可以將木質(zhì)纖維素分解成小分子前體有機物,進而聚合縮合形成腐殖酸[29].

圖1 堆肥腐殖酸形成機制

有機廢棄物來源廣泛、結構組成復雜,不同物料因其結構組成上的差異使得其在堆肥過程中被不同的功能微生物類群分解轉化,進而形成多種腐殖酸前體物質(zhì),使得堆肥過程中腐殖酸形成的主要途徑存在區(qū)別.目前對于秸稈、園林枯枝落葉等植物源有機固體廢棄物堆肥腐殖化過程研究較多,一般認為富含木質(zhì)素的有機廢棄物堆肥腐殖化過程主要依賴于以木質(zhì)素-蛋白質(zhì)復合體為核心的木質(zhì)素-蛋白學說,對于富含結構相對簡單的纖維素類有機固體廢棄物如雜草、尾菜等,其堆肥腐殖化過程中,多酚學說和微生物多酚學說更為主導,同時美拉德反應也發(fā)揮一定作用.然而動物源等高蛋白類有機廢棄物由于有機碳組分在堆肥中直接合成腐殖酸的比例相對較小,無法像植物源有機廢棄物一樣提供充足的典型腐殖酸核心骨架,易降解有機組分相對較高,微生物代謝更為活躍,有機物在堆肥過程中易以氣體形式排放實現(xiàn)穩(wěn)定化,不利于腐殖酸前體物的積累和聚合,但在堆肥過程中仍可發(fā)生明顯的腐殖化過程[30].因此,微生物介導的動物源高蛋白類堆肥腐殖化過程更為復雜,其堆肥腐殖酸形成機制可能更多是以生物途徑為主.

綜上所述,非生物途徑和生物途徑組成了堆肥腐殖酸形成的基本機理.但無論是非生物途徑還是生物途徑,都離不開腐殖酸前體物質(zhì).在堆肥進程中,微生物主導的生物途徑會與非生物途徑競爭底物,大量腐殖酸前體被微生物作為生長活動所需營養(yǎng)物質(zhì)利用消耗,致使堆肥腐殖化進程緩慢[25].因此,為了加速堆肥腐殖化進程,優(yōu)化工藝參數(shù)、添加功能添加劑等多種快速腐熟技術普遍應用于促進堆肥腐殖酸形成,縮短堆肥周期,提升堆肥產(chǎn)品質(zhì)量,使得快速腐熟技術在堆肥領域越來越受到關注.

2 堆肥快速腐熟調(diào)控技術

堆肥存在堆肥周期長、氮素損失、腐熟度低等缺點.腐殖酸是堆肥腐熟的重要指標,未腐熟的堆肥可能缺乏腐殖酸或腐殖酸不穩(wěn)定[4].腐殖酸形成受堆肥基本參數(shù)、原料特性、微生物活性、外源添加劑等因素影響[31].

2.1 堆肥參數(shù)優(yōu)化

2.1.1 堆肥過程基本工藝參數(shù)調(diào)節(jié) 溫度是影響堆肥微生物代謝及種群動態(tài)的重要環(huán)境變量[32].根據(jù)溫度,堆肥過程分為升溫期、高溫期、降溫期(腐熟期)三個時期,每個時期微生物群落影響堆肥腐殖化的機理不同.升溫和高溫期中嗜熱微生物占主導地位,優(yōu)勢嗜熱微生物對HA前體產(chǎn)生起決定性作用[33],且對多糖、木質(zhì)素、蛋白質(zhì)、脂肪的降解與高溫有關[34].溫度過高不利于HA前體形成[32].此外,堆肥進入高溫期越早,有機質(zhì)降解越徹底,越有利于縮短堆肥腐殖化周期[35].堆肥降溫腐熟階段是HA形成的關鍵時期,此時嗜溫微生物發(fā)揮主要作用,促進前體物縮合聚合形成HA[36].

微生物在堆肥過程中活動的最佳pH值范圍為5.5～8.0[37],可通過調(diào)節(jié)pH值來提高堆肥微生物活性及其豐度,以促進堆肥腐殖化進程[34].低pH(3.0～7.5)會使得超分子腐殖酸失穩(wěn),并與小分子富集[38];而pH小于2.0會使腐殖物質(zhì)聚合形成大分子[39].此外, pH對于控制氨揮發(fā)造成的氮損失至關重要[9].

碳氮比是評價堆肥啟動、影響堆肥產(chǎn)品生產(chǎn)工藝和質(zhì)量的重要指標[9].最佳碳氮比的確定決定了堆肥的穩(wěn)定性和腐熟度,初始C/N較低時,碳源少,氮源相對過量,過量的氮轉化成氨氣揮發(fā)導致氮損失;C/N過高時,微生物的活性會降低,有機物分解速度會變慢[40].過高或過低的C/N均不利于堆肥腐熟,被認為最適合堆肥的C/N為25～30[20].

合適的含水率是堆肥成功的關鍵條件,水分對堆肥物理結構、生物活性以及腐熟程度等均產(chǎn)生影響[41].堆體含水率過高或過低都不利于堆肥腐殖化進程,含水量過高,會形成厭氧發(fā)酵,影響堆體升溫;含水量過低,不利于微生物生長繁殖,延緩堆肥腐熟效率[42].堆肥含水率可以通過添加膨脹劑調(diào)節(jié), 40%～60%被廣泛認為是堆肥的最佳含水率范圍[43],不同的堆肥反應系統(tǒng)及堆肥原料最佳含水率可能有所差異.隨著堆肥的進行,水分會通過蒸發(fā)、滲濾流失,需對含水率進行合理調(diào)控,以營造適宜微生物生長繁殖的環(huán)境.

多種參數(shù)共同調(diào)控了影響堆肥中腐殖酸快速形成的直接或間接因子(表1),各個參數(shù)之間并不是獨立作用,而是彼此之間相互聯(lián)系、共同協(xié)調(diào)促進腐殖化進程.因此在實際調(diào)控堆肥參數(shù)時,往往不能只關注某個參數(shù),應聯(lián)系多參數(shù)之間的連鎖效應展開進一步研究.

2.1.2 原料配比 堆肥原料的類型是影響腐殖化過程中的一個重要參數(shù).單一物料堆肥時會受到自身理化性質(zhì)及組成的限制,而多種物料按照合適比例進行堆肥時可以加速腐熟的進程[45].秸稈、園林廢棄物等這類含水率低、碳氮比、孔隙度和木質(zhì)化程度高的堆肥原料,雖然其木質(zhì)素分解產(chǎn)生的酚類物質(zhì)是腐殖酸形成的重要前體,但單一秸稈等物料的堆肥腐殖化程度低[3].而畜禽糞便含水率高、碳氮比和孔隙度低,并含有大量的微生物,作為調(diào)節(jié)劑與秸稈等合理配比混合堆肥,可以促進腐殖物質(zhì)形成,加快腐殖化進程[46].因此提出了原料組分配比堆肥:不同類型的農(nóng)業(yè)廢棄物配比堆肥具有更高的效率,并且成分豐富能生產(chǎn)高質(zhì)量的堆肥產(chǎn)品[47].配比堆肥是基于原材料的物理和化學性質(zhì),按照一定比例組合將含水率和碳氮比調(diào)整到能夠有利于微生物生長繁殖的最佳條件,以加快升溫速度、縮短堆肥腐熟進程[48].在配比堆肥過程中,不同材料的組合可能會加速或減緩堆肥速度,選擇合適的原料對腐殖質(zhì)的形成至關重要,各種原料腐殖質(zhì)化的途徑機制值得進一步研究.

表1 堆肥基本工藝參數(shù)對腐殖酸形成的影響

2.1.3 新興物化輔助策略 近年來為克服傳統(tǒng)堆肥的缺點,開發(fā)了多種物化輔助策略(圖2).超高溫預處理堆肥(HPC)是基于物化輔助策略優(yōu)化堆肥工藝從而衍生出的一種新型堆肥工藝,利用超高溫反應器對堆肥物料進行預處理,再進行傳統(tǒng)堆肥(TC)[49]. Yamada等[50]所研發(fā)的超高溫反應器保持在100℃,持續(xù)2個小時.已有研究表明,HPC可加劇腐殖酸形成,使有機質(zhì)演化指數(shù)提高30%～50%[50];并且HPC 可有效減少總氮損失,氮保留較TC增加49%[51]; HPC還可通過調(diào)控前體產(chǎn)生來促進HA的形成, Huang等[52]表明,HPC中腐殖酸形成前體的濃度增加了44%～92%.此外,細菌群落的變化被認為是HPC過程中腐殖化率和HA產(chǎn)生增加的主要原因,從而導致成熟期縮短[53].Cao等[49]通過13C NMR波譜發(fā)現(xiàn)HPC中提取的腐殖質(zhì)物質(zhì)中的芳烴百分比更高,芳結構富集更早.因此,HPC通過加速堆肥腐殖化和縮短成熟期,在堆肥質(zhì)量和效率上均具有優(yōu)越性.

超高溫堆肥(HTC)同樣被提出作為另一種新型堆肥工藝,通過接種超嗜熱微生物提高好氧發(fā)酵的溫度,無需外源加熱[54].HTC工藝的最高溫度可超過90甚至100°C,明顯高于TC的溫度,從而提高了有機質(zhì)生物轉化效率[55].HTC通過發(fā)展超嗜熱微生物群落,形成超高溫階段,加速有機質(zhì)降解[56].在HTC中,HA前體的氧化水平是決定聚合度和腐殖化程度的關鍵因素.有研究表明HTC中類蛋白物質(zhì)在超高溫條件下通過強烈生物氧化反應產(chǎn)生高濃度含氮前體物,在酶的作用下形成穩(wěn)定的腐殖質(zhì)物質(zhì)[57].由此可見,HTC的快速腐殖化過程歸因于超嗜熱菌驅(qū)動有機質(zhì)快速降解和轉化形成前體,前體深度氧化進而加速HA形成.與傳統(tǒng)堆肥相比,超高溫堆肥依靠其獨特的嗜熱微生物群落在提高堆肥效率和減少氣體排放上具有潛力性[58].HTC系統(tǒng)的關鍵問題是缺乏合適的超嗜熱菌持續(xù)降解有機質(zhì),評估其他超嗜熱菌在HTC系統(tǒng)中的應用可行性值得研究.

電場輔助好氧堆肥(EAC)是一種新穎且有效的促腐工藝.好氧堆肥在本質(zhì)上是微生物驅(qū)動下的氧化還原過程,該過程產(chǎn)生的電子可被電活性細菌轉移到細胞外電子受體,EAC可以增加電活性細菌的相對豐度,從而加速有機物的生物降解,提高堆肥腐熟度[59].Cao等[60]研究證明施加直流電場豐富了堆肥中細菌豐度及其代謝,促進腐殖酸形成.直流電場可將TC的溫度提高到70～75℃,但直流電場作用下的梯度水分分布影響了微生物代謝熱,限制了堆肥溫度的升高[61].與直流電場不同,交流電場(AEF)可促進堆肥堆體中水分的均勻分布,進一步將溫度提高到90℃,促進有機質(zhì)的生物降解和腐殖化過程[62].此外,AEF還可富集嗜熱菌,其代表了一種新穎且適用于HTC快速腐殖化調(diào)控的可行策略.但堆肥材料導電性差、電子傳遞效率低等影響了EAC的效率和適用性[63].因此,提高堆肥系統(tǒng)的電導率對于確保EAC系統(tǒng)快速腐殖化調(diào)控的有效性非常重要.

2.2 常規(guī)堆肥添加劑強化

添加劑被認為是促進堆肥腐殖化的一種高效且易于掌握的策略.添加劑可以促進有機質(zhì)的分解,保留堆體營養(yǎng)物質(zhì),從而獲得腐殖物質(zhì)和營養(yǎng)物質(zhì)豐富的堆肥產(chǎn)品[65].

2.2.1 微生物菌劑 微生物作為堆肥腐殖化過程中物質(zhì)循環(huán)和能量流動的主要推動者,有機物在其作用下聚合或縮合形成腐殖酸[66].堆肥中,土著微生物菌群主導有機物的分解轉化;土著微生物菌群多樣性不足或受到某些環(huán)境參數(shù)和原料特性的不利影響,則會導致分解能力差、堆肥周期長、產(chǎn)品質(zhì)量低[67].因此,接種微生物菌劑是一種有效的促腐策略,通過改變微生物群落及其代謝功能,可加速簡單化合物的降解和復雜化合物的形成,促進腐殖化程度,提升堆肥產(chǎn)品質(zhì)量[68].

堆肥中主要微生物種類是細菌(包括放線菌)和真菌,在不同時期中都有其獨特的優(yōu)勢菌群,共同促進物料的分解和腐熟[69].在堆肥過程中細菌群落多樣性越高,對有機物的降解越有利[70].有研究表明細菌接種可增加細菌群落多樣性,產(chǎn)生更多功能性細菌,促進堆肥腐殖化[71].細菌作為主導升溫期的菌群,對發(fā)酵升溫起主要作用.Li等[72]證明接種微生物菌劑可加速溫度上升,縮短堆肥周期.事實上,堆肥產(chǎn)生的熱量主要來自微生物分泌的降解有機物的酶[70]. Duan等[73]報道,堆肥中接種枯草芽孢桿菌可增強纖維素酶、蛋白酶和淀粉酶的分泌,促進纖維素和蛋白質(zhì)的生物降解,從而形成穩(wěn)定的腐殖質(zhì).真菌接種加強堆肥進程也尤其顯著,堆肥中重要且廣泛使用的真菌之一是白腐真菌.它產(chǎn)生由錳過氧化物酶、木質(zhì)素過氧化物酶和漆酶組成的細胞外酶系統(tǒng),可用于降解木質(zhì)纖維素[74].研究發(fā)現(xiàn),接種白腐真菌是增強最終堆肥產(chǎn)品特性的有用策略,有機物降解和堆肥成熟的有效性取決于真菌類型[75].Zhang等[76]研究證明接種黃孢原毛平革菌(Phanerochaete chrysosporium對木質(zhì)素等穩(wěn)定性有機質(zhì)的分解有積極作用.此外,放線菌在堆肥微生物群落中起著重要的作用,不僅可生產(chǎn)木質(zhì)纖維素水解酶,還可在高溫下形成孢子以抵抗堆肥過程中的惡劣環(huán)境[77]. Zhao等[69]發(fā)現(xiàn),多階段接種從堆肥樣品中篩選出的纖維素降解嗜熱放線菌可提高纖維素酶活性,在加速纖維素降解、提高腐殖酸含量的同時降低了CO2排放量.

綜上所述,接種微生物菌劑是提高堆肥腐殖化和效率的有效措施之一,其機理主要包括:1)豐富微生物群落及其功能多樣性,共同參與腐殖質(zhì)合成.2)增加核心菌落豐度,合成大量酶促進有機物降解.3)改善礦化,保留碳氮,增強有機物轉化為腐殖質(zhì).盡管如此,微生物接種的有效性仍受微生物種類、接種時間、堆肥具體操作條件、原料特性等因素影響[78],調(diào)控堆肥快速腐殖化的最適微生物接種技術是什么的問題仍然存在.在未來,需要確定最佳接種微生物濃度;需要考慮堆肥過程中微生物的接種劑種類、功能、生理、適應性和穩(wěn)定性;需要針對堆肥過程中的微生物作用機制進行研究,以期找到堆肥過程中最適宜添加的微生物菌劑.

2.2.2 外源腐殖酸前體物 前體在腐殖酸形成過程中起著關鍵作用.堆肥腐殖酸前體可通過有機物分解和微生物合成兩種途徑形成[22].在生物和非生物腐殖化途徑下通過氧化和親核反應聚合形成腐殖酸[79].多酚作為腐殖酸的芳香族骨架,促進腐殖酸的芳香性以確保其結構穩(wěn)定性[80].羧基對增加腐殖酸的脂肪族化合物和不飽和度起著重要作用[24].氨基酸是含氮有機物的水解產(chǎn)物,被還原可作微生物的氮源,為HA的形成提供氮素[81].還原糖和多糖作為微生物的主要能量和碳源,可促進FA轉化成HA[23].因此,前體作為促進腐殖酸形成的重要調(diào)節(jié)因子,通過添加外源前體物是促進堆肥快速腐殖化的有效方法.

外源前體物促進堆肥腐殖化主要是通過以下幾方面(圖3):1)直接參與腐殖酸的形成[82];2)提高FA向HA的轉化速率,增加HA的不飽和度[83];3)促進木質(zhì)纖維素降解[4],并改變細菌群落功能以調(diào)節(jié)前體數(shù)量[82];4)作為微生物的能源物質(zhì)和養(yǎng)分來源,提高微生物代謝能力以產(chǎn)生腐殖酸前體[84];5)減弱微生物對前體的利用,使得更多前體形成腐殖酸[11].外源前體物促進HA形成的多種途徑并不是單獨存在的,而是多途徑相互聯(lián)系、共同作用[85],因此未來研究應探究各前體在堆肥不同時期下多途徑之間的相互關系,精準定位不同外源前體物的添加時期,提高促腐效率.

圖3 外源腐殖酸前體促進堆肥腐殖化機制

2.2.3 腐熟堆肥回流 腐熟堆肥(MC)作為堆肥穩(wěn)定發(fā)酵產(chǎn)品,具有低含水率、低碳氮比、高孔隙及富含微生物的特點[86].MC屬于常用的堆肥添加劑,并兼具調(diào)理劑、膨脹劑與接種劑的功能[12].添加MC可以有效促進堆肥快速腐殖化,縮短堆肥周期.

MC通過調(diào)節(jié)堆肥物理結構和微生物群落結構兩個方面來影響堆肥的礦化和腐殖化進程.一方面,MC用作調(diào)理劑,可提高堆肥孔隙度并降低堆肥含水率[87].另一方面,MC用作膨脹劑和接種劑,可為堆體接種內(nèi)源微生物,加速微生物演替,縮短堆肥周期[88].因此,MC理論上是一種促進快速腐殖化的堆肥輔料調(diào)節(jié)劑和微生物接種劑綜合體.腐熟堆肥回流有利于腐殖酸前體的形成與積累,有效降低腐殖質(zhì)損失率,顯著提高腐殖質(zhì)含量[12].在經(jīng)濟效益上,腐熟堆肥可代替商業(yè)微生物接種物,降低堆肥成本[89].此外,MC可回收利用,價格低廉且易于獲得.但利用腐熟堆肥作為堆肥添加劑需要很高的添加比例,但過高的添加量會抑制堆肥過程中腐殖質(zhì)聚合度和芳構化程度的增長,因此在實際生產(chǎn)中要注意控制腐熟堆肥的添加用量,以確保堆肥效果.

2.3 新型功能添加劑

在研究外源添加劑提高堆肥快速腐熟的同時,還應盡可能考慮產(chǎn)品的多功能性.為提升堆肥產(chǎn)品附加值,新型功能添加劑如生物炭、礦物質(zhì)等被發(fā)掘應用.新型添加劑施加在堆肥中不僅可穩(wěn)定形成腐殖酸,還可增強堆肥產(chǎn)品的農(nóng)藝功能[5].

2.3.1 生物炭 生物炭是一類碳含量極高、活性官能團豐富、離子交換能力強、芳構化程度高、性質(zhì)穩(wěn)定的碳基物質(zhì)[90].大量研究表明,生物炭在促進堆肥腐殖化中發(fā)揮積極作用.

生物炭直接促進堆肥腐殖化通過以下機制實現(xiàn):1)生物炭自身部分被氧化降解釋放可溶性有機化合物和芳香化合物摻入腐殖質(zhì)類物質(zhì),促進HA的形成及其穩(wěn)定[91].有研究發(fā)現(xiàn)木材生物炭的水萃取部分含有更高水平的類富里酸和類胡敏酸物質(zhì),可直接用于形成類腐殖質(zhì)樣物質(zhì)[13].2)堆肥形成的HA及其前體等物質(zhì)通過配體交換和疏水作用在生物炭活性表面吸附保留[39].生物炭表面豐富的官能團(如羧基、羥基、羰基、?；?可作為吸附位點[92],將腐殖質(zhì)吸附到其表面并保護它們免受微生物分解來促進腐殖化過程[91].

生物炭間接促進腐殖化則通過影響堆肥微生物群落實現(xiàn)[93].高比表面積可為微生物生長繁殖提供適宜的棲息環(huán)境.豐富的孔隙結構可加速氧氣快速流通和能量傳輸,促進微生物的好氧代謝[94].生物炭表面能吸附堆肥中產(chǎn)生的水溶性碳和酚類等物質(zhì),作為底物為微生物生長代謝提供營養(yǎng)[95].生物炭可通過中和氫離子或促進有機酸的降解來調(diào)節(jié)堆肥體系的酸堿環(huán)境,增強微生物活性[13].此外,生物炭還可提高產(chǎn)品附加值.可通過靜電吸引作用減少氣體揮發(fā)和養(yǎng)分損失;依賴表面高陽離子交換能力及含氧官能團降低堆肥中重金屬生物有效性;通過表面的電子供體受體吸附削減有機污染物的毒性[96].

綜上所述,生物炭在促進堆肥腐殖化、改善堆肥產(chǎn)品質(zhì)量上展現(xiàn)出巨大的優(yōu)勢.過往研究討論了不同生物炭添加量對腐殖化的影響,建議添加約10%的生物炭以最大限度促進堆肥腐殖化[2].盡管如此,超過20%的添加量會抑制微生物的活性并干擾有機物的降解,同時生物炭較高的成本限制了其大劑量的使用.另外不能忽略的一個問題便是內(nèi)源污染問題,如何有效避免因內(nèi)源污染產(chǎn)生環(huán)境風險在未來值得進一步研究.

2.3.2 礦物質(zhì) 堆肥作為一個快速、易變化的體系,堆肥所形成的類腐殖質(zhì)物質(zhì)不穩(wěn)定易被降解,外源礦物質(zhì)的添加可以緩解堆肥過程中類腐殖質(zhì)物質(zhì)的降解,提高堆肥腐殖酸形成穩(wěn)定性[65].

礦物質(zhì)通過以下四種主要機制促進腐殖化(圖4):首先,直接催化美拉德反應[97].其次,通過改變微生物群落結構和多樣性并產(chǎn)生協(xié)同作用.一方面,多孔特性和高比表面積為微生物活動或表面官能團催化腐殖化提供位點和空間[98].另一方面,通過調(diào)節(jié)堆肥理化性質(zhì)來為微生物降解創(chuàng)造適宜的環(huán)境.其獨特的晶體結構和內(nèi)部納米孔道的吸附性,保證了良好的保水保肥性和酸堿緩沖性能[99].同時,礦物不同形式的電子能量通過胞外電子傳遞方式影響微生物生長代謝,豐富微生物的能量獲取途徑,并且作為直接參與生長代謝的電子供體/受體,提高電子能量的傳遞效率,促進堆肥腐殖化[100].再次,可加速前體的形成和積累,從而促進堆肥腐殖化.最后,通過各種吸附機制與腐殖質(zhì)相互作用形成有機無機復合體,保障腐殖酸穩(wěn)定形成[101-102].在礦物質(zhì)基底表面,腐殖酸通過疏水相互作用和陽離子橋鍵吸附形成有機無機復合體[103].在礦物質(zhì)邊緣表面,腐殖酸通過配體交換和靜電吸引吸附形成有機無機復合體[101].

近年來,很多具有促腐殖化能力的礦物質(zhì)添加劑被廣泛研究, Pan等[104]發(fā)現(xiàn)蒙脫石和伊利石的添加主要促進了HA的非生物途徑的形成.蒙脫石和沸石可用作路易斯酸,以非生物方式催化氨基酸和還原糖縮合以產(chǎn)生腐殖酸[19,105].蒙脫石基底表面的Si-O、Si-O-Al基團也參與了礦物邊緣對HA的吸附,促進了HA的形成[36].膨潤土可為微生物提供棲息地,還可吸附酶并增強酶活性和穩(wěn)定性,從而促進微生物降解有機物,提高堆肥的穩(wěn)定性和成熟度[106].堿性石灰可促進木質(zhì)纖維素水解產(chǎn)生前體,還可調(diào)節(jié)堆肥的初始酸性pH值[14].黑電氣石可延長高溫期,改善腐殖化并減少氮損失[107].麥飯石可加速木質(zhì)纖維素降解,促進HA形成[108].海泡石可增加堆體中高芳香組分占比,提高堆肥穩(wěn)定性從而促進堆肥腐熟[109].凹凸棒土可加速有機物降解并促進動物糞便堆肥腐殖化[110].

礦物質(zhì)作為一種廉價易得、操作性強、時效長和經(jīng)濟成本低的材料,礦物質(zhì)改性能夠進一步提升快速堆肥腐殖化效果,如Pan等[104]發(fā)現(xiàn)熱改性礦物較普通礦物促進堆肥腐熟效果更好.未來可進一步研究開發(fā)應用于堆肥促腐的礦物質(zhì)改性方法,同時還需結合土壤礦物學理論和微生物學進一步剖析有機無機復合體在堆肥體系中穩(wěn)定形成腐殖酸的機制.最后,從堆肥實際生產(chǎn)應用角度出發(fā),應該進行更多的大規(guī)模試驗,驗證從小試或中試規(guī)模研究中獲得的結果.

3 結語

快速堆肥是為了在短時間內(nèi)獲得完全腐熟的終端產(chǎn)物,腐殖酸含量是堆肥產(chǎn)品的重要評判指標,快速腐熟調(diào)控技術(圖5)都是以促進腐殖酸穩(wěn)定形成為目的.優(yōu)化工藝參數(shù)是調(diào)控各種堆肥理化性質(zhì),為堆肥各階段關鍵微生物提供最適宜的棲息環(huán)境,提高微生物多樣性及其代謝活性,通過微生物間接促進腐殖質(zhì)穩(wěn)定生成.物化輔助策略是從原料預處理、接種超嗜熱微生物、加速電子傳遞的角度來提高酶活性、增殖超嗜熱微生物、加強微生物代謝活性,以實現(xiàn)快速腐殖化.常規(guī)強化添加劑是通過強化腐殖酸形成途徑中的某一環(huán)節(jié),如生物腐殖化途徑、前體形成和積累等,以提高腐殖化效率,縮短堆肥周期.新型功能添加劑則是依靠其豐富的孔隙空間和表面官能團通過多種吸附作用吸附氨基酸、糖和酚等低分子量化合物,促進腐殖酸前體形成和積累,還可形成有機無機復合體以保護腐殖酸并促進腐殖酸穩(wěn)定化,同時由于其穩(wěn)定的性質(zhì)還能保留在堆肥產(chǎn)品中,從碳固存、降低重金屬有效性、削弱有機污染物毒性等多個方面提高堆肥附加價值.此外,本文針對各調(diào)控手段分別給予了一定研究展望.總的來說,由于堆肥環(huán)境的波動變化和微生物群落的演化,不論是調(diào)控參數(shù)還是外源添加劑對腐殖化的影響相對來說都是難以控制,而且大多數(shù)促腐殖化研究都是在實驗室條件下展開,并未投入到實際生產(chǎn)應用中,對于這些手段促腐效果并沒有一個綜合的評價.因此,針對不同有機固廢原料性質(zhì)的差異性,選擇合適的添加劑種類、添加量對于精細化控制堆肥進程是有意義的,未來還需深入研究.

圖5 堆肥促腐調(diào)控技術

[1] 中華人民共和國國家統(tǒng)計局.中國統(tǒng)計年鑒 [M]. 北京:中國統(tǒng)計出版社, 2021. National Bureau of Statistics of China. china statistical yearbook [M]. Beijing: China Statistics Press, 2021.

[2] Awasthi M K, Wang Q, Chen H, et al. Evaluation of biochar amended biosolids co-composting to improve the nutrient transformation and its correlation as a function for the production of nutrient-rich compost [J]. Bioresource Technology, 2017,237:156-166.

[3] Reyes-Torres M, Oviedo-Oca?a E, Dominguez I, et al. A systematic review on the composting of green waste: Feedstock quality and optimization strategies [J]. Waste Management, 2018,77:486-499.

[4] Zhang Z, Zhao Y, Yang T, et al. Effects of exogenous protein-like precursors on humification process during lignocellulose-like biomass composting: amino acids as the key linker to promote humification process [J]. Bioresource Technology, 2019,291:121882.

[5] 郭小夏,劉洪濤,常志州,等.有機廢物好氧發(fā)酵腐殖質(zhì)形成機理及農(nóng)學效應研究進展[J]. 生態(tài)與農(nóng)村環(huán)境學報, 2018,34(6):489-498. Guo X X, Liu H T, Chang Z Z, et al. Review of humic substances developed in organic waste aerobic composting and its agronomic effect [J]. Journal of Ecology and Rural Environment, 2018,34(6): 489-498.

[6] 徐子琪,閻 中,葛艷菊,等.有機垃圾機械強化快速好氧發(fā)酵工藝參數(shù)優(yōu)化[J]. 環(huán)境工程, 2022,40(8):159-163.142. Xu Z Q, Yan Z, Ge Y J, et al. Optimization of technical paramaters of mechanical enhanced rapid composting technology for organic solid waste [J]. Environmental Engineering, 2022,40(8):159-163,142.

[7] Zhang L, Sun X. Improving green waste composting by addition of sugarcane bagasse and exhausted grape marc [J]. Bioresource Technology, 2016,218:335-343.

[8] Zhang T, Wu X, Shaheen S M, et al. Effects of microorganism- mediated inoculants on humification processes and phosphorus dynamics during the aerobic composting of swine manure [J]. Journal of Hazardous Materials, 2021,416:125738.

[9] Amuah E E Y, Fei-Baffoe B, Sackey L N A, et al. A review of the principles of composting: Understanding the processes, methods, merits, and demerits [J]. Organic Agriculture, 2022,12(4):547-562.

[10] Li S, Li J, Zhang B, et al. Influence of inoculants on content and quality of humus during chicken manure composting [J]. Transactions of the Chinese Society of Agricultural Engineering, 2016,32(1):268- 274.

[11] Zhang Z, Zhao Y, Wang R, et al. Effect of the addition of exogenous precursors on humic substance formation during composting [J]. Waste Management, 2018,79:462-471.

[12] 徐 成,劉國濤,王 政,等.添加腐熟堆肥對廚余垃圾堆肥腐殖質(zhì)形成的影響[J]. 環(huán)境科學與技術, 2020,43(8):122-127. Xu C, Liu G T, Wang Z, et al. Effect of matured compost addition on the formation of humus in kitchen waste composting [J]. Environmental Science & Technology, 2020,43(8):122-127.

[13] Zhang J, Lü F, Luo C, et al. Humification characterization of biochar and its potential as a composting amendment [J]. Journal of Environmental Sciences, 2014,26(2):390-397.

[14] Wong J W-C, Fung S O, Selvam A. Coal fly ash and lime addition enhances the rate and efficiency of decomposition of food waste during composting [J]. Bioresource Technology, 2009,100(13):3324- 3331.

[15] Chi J, Fan Y, Wang L, et al. Retention of soil organic matter by occlusion within soil minerals [J]. Reviews in Environmental Science and Bio/Technology, 2022,21(3):727-746.

[16] 油 暢,崔 駿,李 強,等.堆肥腐殖酸形成及其電化學活性[J]. 環(huán)境科學研究, 2021,34(12):2980-2988. You C, Cui J, Li Q, et al. Formation and electrochemical activity of humic acid in compost [J]. Research of Environmental Sciences, 2021,34(12):2980-2988.

[17] Muscolo A, Sidari M, Nardi S. Humic substance: Relationship between structure and activity. Deeper information suggests univocal findings [J]. Journal of Geochemical Exploration, 2013,129:57-63.

[18] 唐景春,孫 青,王如剛,等.堆肥過程中腐殖酸的生成演化及應用研究進展[J]. 環(huán)境污染與防治, 2010,32(5):73-77,88. Tang J C, Sun Q, Wang R G, et al. Formation and evolution of humic acid during composting process and its application [J]. Environmental Pollution & Control, 2010,32(5):73-77,88.

[19] Fukuchi S, Miura A, Okabe R, et al. Spectroscopic investigations of humic-like acids formed via polycondensation reactions between glycine, catechol and glucose in the presence of natural zeolites [J]. Journal of Molecular Structure, 2010,982(1-3):181-186.

[20] Ayilara M S, Olanrewaju O S, Babalola O O, et al. Waste management through composting: Challenges and potentials [J]. Sustainability, 2020,12(11):4456.

[21] Stevenson F J. Humus chemistry: genesis, composition, reactions [M]. New York: John Wiley & Sons, 1994.

[22] Tan K H. Humic matter in soil and the environment: principles and controversies [M]. Boca Raton: CRC press, 2003.

[23] Wu J, Zhao Y, Zhao W, et al. Effect of precursors combined with bacteria communities on the formation of humic substances during different materials composting [J]. Bioresource Technology, 2017,226: 191-199.

[24] Hardie A, Dynes J, Kozak L, et al. The role of glucose in abiotic humification pathways as catalyzed by birnessite [J]. Journal of Molecular Catalysis A: Chemical, 2009,308(1/2):114-126.

[25] 解新宇,史明子,齊海石,等.堆肥腐殖化:非生物學與生物學調(diào)控機制概述[J]. 生物技術通報, 2022,38(5):29-35. Xie X Y, Shi M Z, Qi H S, et al. Compost humification: An overview of abiotic and biological regulatory mechanisms [J]. Biotechnology Bulletin, 2022,38(5):29-35.

[26] 明中遠.基于市政污泥好氧堆肥過程的強化腐殖化技術研究 [D]. 北京:清華大學, 2016. Ming Z Y. Research on the enhenced humification in primary stage of sewage sludge composting [D]. Beijing, Tsinghua University, 2016.

[27] 竇 森,王 帥.不同微生物對形成不同腐殖質(zhì)組分的差異性研究進展[J]. 吉林農(nóng)業(yè)大學學報, 2011,33(2):119-125. Dou S, Wang S. Review of different microorganisms effect on humus formation [J]. Journal of Jilin Agricultural University, 2011,33(2):119- 125.

[28] Qi H, Zhao Y, Zhao X, et al. Effect of manganese dioxide on the formation of humin during different agricultural organic wastes compostable environments: It is meaningful carbon sequestration [J]. Bioresource Technology, 2020,299:122596.

[29] Chen S, Yang Y, Jing X, et al. Enhanced aging of polystyrene microplastics in sediments under alternating anoxic-oxic conditions [J]. Water Research, 2021,207:117782.

[30] Wei Y, Wang N, Lin Y, et al. Recycling of nutrients from organic waste by advanced compost technology-A case study [J]. Bioresource Technology, 2021,337:125411.

[31] Guo X-X, Liu H-T, Wu S-B. Humic substances developed during organic waste composting: Formation mechanisms, structural properties, and agronomic functions [J]. Science of the Total Environment, 2019,662:501-510.

[32] Liang C, Das K, Mcclendon R. The influence of temperature and moisture contents regimes on the aerobic microbial activity of a biosolids composting blend [J]. Bioresource Technology, 2003,86(2): 131-137.

[33] Zhu N, Zhu Y, Kan Z, et al. Effects of two-stage microbial inoculation on organic carbon turnover and fungal community succession during co-composting of cattle manure and rice straw [J]. Bioresource Technology, 2021,341:125842.

[34] Onwosi C O, Igbokwe V C, Odimba J N, et al. Composting technology in waste stabilization: On the methods, challenges and future prospects [J]. Journal of Environmental Management, 2017,190:140-157.

[35] Awasthi M K, Pandey A K, Khan J, et al. Evaluation of thermophilic fungal consortium for organic municipal solid waste composting [J]. Bioresource Technology, 2014,168:214-221.

[36] Xu J, Jiang Z, Li M, et al. A compost-derived thermophilic microbial consortium enhances the humification process and alters the microbial diversity during composting [J]. Journal of Environmental Management, 2019,243:240-249.

[37] Raza S, Ahmad J. Composting process: a review [J]. International Journal of Biological Research, 2016,4(2):102.

[38] Pédrot M, Dia A, Davranche M. Dynamic structure of humic substances: Rare earth elements as a fingerprint [J]. Journal of Colloid and Interface Science, 2010,345(2):206-213.

[39] Wang C, Tu Q, Dong D, et al. Spectroscopic evidence for biochar amendment promoting humic acid synthesis and intensifying humification during composting [J]. Journal of Hazardous Materials, 2014,280:409-416.

[40] Kumar M, Ou Y-L, Lin J-G. Co-composting of green waste and food waste at low C/N ratio [J]. Waste Management, 2010,30(4):602-609.

[41] Kulikowska D. Kinetics of organic matter removal and humification progress during sewage sludge composting [J]. Waste Management, 2016,49:196-203.

[42] 邵華偉,楊 莉,趙紅霞,等.不同堆肥方式對農(nóng)業(yè)廢棄物堆肥腐熟效率的影響[J]. 農(nóng)村科技, 2021,(6):23-26. Shao H W, Yang L, Zhao H X, et al. Effects of different composting methods on the maturity efficiency of agricultural waste composting [J]. Rural Science & Technology, 2021,(6):23-26.

[43] Wang S-P, Wang L, Sun Z-Y, et al. Effect of distillery sewage sludge addition on performance and bacterial community dynamics during distilled grain waste composting [J]. Bioresource Technology, 2022, 345:126486.

[44] Cayuela M L, Sánchez-Monedero M, Roig A. Evaluation of two different aeration systems for composting two-phase olive mill wastes [J]. Process Biochemistry, 2006,41(3):616-623.

[45] Kulcu R, Yaldiz O. Composting dynamics and optimum mixture ratio of chicken manure and vineyard wastes [J]. Waste Management & Research, 2005,23(2):101-105.

[46] 王廣耀,李 雪.有機物料配比對堆肥腐殖質(zhì)及養(yǎng)分含量變化的影響[J]. 河南農(nóng)業(yè)科學, 2021,50(2):66-71. Wang G Y, Li X. Effect of organic material ratio on change of humus and nutrient content in compost [J]. Journal of Henan Agricultural Sciences, 2021,50(2):66-71.

[47] Liu N, Han H, Yin H, et al. Variations in the fate and risk analysis of amoxicillin and its degradation products during pig manure aerobic composting [J]. Journal of Hazardous Materials, 2018,346:234-241.

[48] Soares M A, Quina M J, Quinta-Ferreira R. Prediction of free air space in initial composting mixtures by a statistical design approach [J]. Journal of Environmental Management, 2013,128:75-82.

[49] Cao Y, Wang J, Huang H, et al. Spectroscopic evidence for hyperthermophilic pretreatment intensifying humification during pig manure and rice straw composting [J]. Bioresource Technology, 2019, 294:122131.

[50] Yamada T, Miyauchi K, Ueda H, et al. Composting cattle dung wastes by using a hyperthermophilic pre-treatment process: Characterization by physicochemical and molecular biological analysis [J]. Journal of Bioscience and Bioengineering, 2007,104(5):408-415.

[51] Huang Y, Li D, Wang L, et al. Decreased enzyme activities, ammonification rate and ammonifiers contribute to higher nitrogen retention in hyperthermophilic pretreatment composting [J]. Bioresource Technology, 2019,272:521-528.

[52] Huang Y, Danyang L, Shah G M, et al. Hyperthermophilic pretreatment composting significantly accelerates humic substances formation by regulating precursors production and microbial communities [J]. Waste Management, 2019,92:89-96.

[53] Tang Y, Dong B, Dai X. Hyperthermophilic pretreatment composting to produce high quality sludge compost with superior humification degree and nitrogen retention [J]. Chemical Engineering Journal, 2022, 429:132247.

[54] Liu X-M, Yu Z, Zhou P-X, et al. Spectroscopic characterization of DOM during hyperthermophilic composting of sewage sludge [J]. Environmental Science, 2018,39(8):3807-3815.

[55] Yu Z, Tang J, Liao H, et al. The distinctive microbial community improves composting efficiency in a full-scale hyperthermophilic composting plant [J]. Bioresource Technology, 2018,265:146-154.

[56] Wang S, Wu Y. Hyperthermophilic composting technology for organic solid waste treatment: recent research advances and trends [J]. Processes, 2021,9(4):675.

[57] Yu Z, Liu X, Zhao M, et al. Hyperthermophilic composting accelerates the humification process of sewage sludge: Molecular characterization of dissolved organic matter using EEM–PARAFAC and two- dimensional correlation spectroscopy [J]. Bioresource Technology, 2019,274:198-206.

[58] Wang Z, Wu D, Lin Y, et al. Role of temperature in sludge composting and hyperthermophilic systems: A review [J]. BioEnergy Research, 2021:1-15.

[59] Tang J, Li X, Zhao W, et al. Electric field induces electron flow to simultaneously enhance the maturity of aerobic composting and mitigate greenhouse gas emissions [J]. Bioresource Technology, 2019, 279:234-242.

[60] Cao Y, Wang X, Zhang X, et al. An electric field immobilizes heavy metals through promoting combination with humic substances during composting [J]. Bioresource Technology, 2021,330:124996.

[61] Fu T, Shangguan H, Shen C, et al. Moisture migration driven by the electric field causes the directional differentiation of compost maturity [J]. Science of The Total Environment, 2022,811:152415.

[62] Fu T, Tang J, Wu J, et al. Alternating electric field enables hyperthermophilic composting of organic solid wastes [J]. Science of The Total Environment, 2022,828:154439.

[63] Li X, Zhao Y, Xu A, et al. Conductive biochar promotes oxygen utilization to inhibit greenhouse gas emissions during electric field- assisted aerobic composting [J]. Science of The Total Environment, 2022,842:156929.

[64] Cui P, Liao H, Bai Y, et al. Hyperthermophilic composting reduces nitrogen loss via inhibiting ammonifiers and enhancing nitrogenous humic substance formation [J]. Science of the Total Environment, 2019,692:98-106.

[65] Chen L, Chen Y, Li Y, et al. Improving the humification by additives during composting: A review [J]. Waste Management, 2023,158: 93-106.

[66] Cui H-Y, Zhang S-B, Zhao M-Y, et al. Parallel faction analysis combined with two-dimensional correlation spectroscopy reveal the characteristics of mercury-composting-derived dissolved organic matter interactions [J]. Journal of Hazardous Materials, 2020,384: 121395.

[67] Greff B, Szigeti J, Varga á, et al. Effect of bacterial inoculation on co-composting of lavender (Lavandula angustifolia Mill.) waste and cattle manure [J]. Biotech, 2021,11(6):306.

[68] Wu D, Wei Z, Qu F, et al. Effect of Fenton pretreatment combined with bacteria inoculation on humic substances formation during lignocellulosic biomass composting derived from rice straw [J]. Bioresource Technology, 2020,303:122849.

[69] Zhao Y, Zhao Y, Zhang Z, et al. Effect of thermo-tolerant actinomycetes inoculation on cellulose degradation and the formation of humic substances during composting [J]. Waste Management, 2017,68:64-73.

[70] Sun Q, Wu D, Zhang Z, et al. Effect of cold-adapted microbial agent inoculation on enzyme activities during composting start-up at low temperature [J]. Bioresource Technology, 2017,244:635-640.

[71] Gao X, Xu Z, Li Y, et al. Bacterial dynamics for gaseous emission and humification in bio-augmented composting of kitchen waste [J]. Science of The Total Environment, 2021,801:149640.

[72] Li C, Li H, Yao T, et al. Microbial inoculation influences bacterial community succession and physicochemical characteristics during pig manure composting with corn straw [J]. Bioresource Technology, 2019,289:121653.

[73] Duan M, Zhang Y, Zhou B, et al. Effects of Bacillus subtilis on carbon components and microbial functional metabolism during cow manure– straw composting [J]. Bioresource Technology, 2020,303:122868.

[74] Varma V S, Ramu K, Kalamdhad A S. Carbon decomposition by inoculating Phanerochaete chrysosporium during drum composting of agricultural waste [J]. Environmental Science and Pollution Research, 2015,22:7851-7858.

[75] Voběrková S, Vaverková M D, Bure?ová A, et al. Effect of inoculation with white-rot fungi and fungal consortium on the composting efficiency of municipal solid waste [J]. Waste Management, 2017,61: 157-164.

[76] Zhang C, Xu Y, Zhao M, et al. Influence of inoculating white-rot fungi on organic matter transformations and mobility of heavy metals in sewage sludge based composting [J]. Journal of Hazardous Materials, 2018,344:163-168.

[77] Zhao Y, Lu Q, Wei Y, et al. Effect of actinobacteria agent inoculation methods on cellulose degradation during composting based on redundancy analysis [J]. Bioresource Technology, 2016,219:196-203.

[78] Greff B, Szigeti J, Nagy á, et al. Influence of microbial inoculants on co-composting of lignocellulosic crop residues with farm animal manure: A review [J]. Journal of Environmental Management, 2022, 302:114088.

[79] Orlov D S. Humic substances of soils and general theory of humification [M]. Boca Raton: CRC Press, 2020.

[80] Zhang Y, Yue D, Ma H. Darkening mechanism and kinetics of humification process in catechol-Maillard system [J]. Chemosphere, 2015,130:40-45.

[81] Lu M, Feng Q, Li X, et al. Effects of arginine modified additives on humic acid formation and microbial metabolic functions in biogas residue composting [J]. Journal of Environmental Chemical Engineering, 2022,10(6):108675.

[82] Zheng G, Liu C, Deng Z, et al. Identifying the role of exogenous amino acids in catalyzing lignocellulosic biomass into humus during straw composting [J]. Bioresource Technology, 2021,340:125639.

[83] Wang N, Zhang Q, Li W, et al. Effect of exogenous glucose at different concentrations on the formation of dark-brown humic-like substances in the maillard reaction pathway based on the abiotic condensation of precursors involving δ-MnO2[J]. Sustainability, 2022,14(18):11603.

[84] Ma H, Beadham I, Ruan W, et al. Enhancing rice straw compost with an amino acid-derived ionic liquid as additive [J]. Bioresource Technology, 2022,345:126387.

[85] Wei Z, Wu J, Zhao Y, et al. Production of amino acids and its effect on the formation of humic acids during composting [J]. Journal of Environmental Engineering Technology, 2016,6(4):377-383.

[86] Yang F, Li Y, Han Y, et al. Performance of mature compost to control gaseous emissions in kitchen waste composting [J]. Science of the Total Environment, 2019,657:262-269.

[87] Iqbal M K, Shafiq T, Ahmed K. Characterization of bulking agents and its effects on physical properties of compost [J]. Bioresource Technology, 2010,101(6):1913-1919.

[88] Kato K, Miura N. Effect of matured compost as a bulking and inoculating agent on the microbial community and maturity of cattle manure compost [J]. Bioresource Technology, 2008,99(9):3372-3380.

[89] Yang W, Zhang L. Addition of mature compost improves the composting of green waste [J]. Bioresource Technology, 2022,350: 126927.

[90] Cha J S, Park S H, Jung S-C, et al. Production and utilization of biochar: A review [J]. Journal of Industrial and Engineering Chemistry, 2016,40:1-15.

[91] Jindo K, Sonoki T, Matsumoto K, et al. Influence of biochar addition on the humic substances of composting manures [J]. Waste Management, 2016,49:545-552.

[92] Xiao X, Chen B, Chen Z, et al. Insight into multiple and multilevel structures of biochars and their potential environmental applications: A critical review [J]. Environmental Science & Technology, 2018,52(9):5027-5047.

[93] Jindo K, Sánchez-Monedero M A, Hernández T, et al. Biochar influences the microbial community structure during manure composting with agricultural wastes [J]. Science of the Total Environment, 2012,416:476-481.

[94] He X, Chen L, Han L, et al. Evaluation of biochar powder on oxygen supply efficiency and global warming potential during mainstream large-scale aerobic composting [J]. Bioresource Technology, 2017,245: 309-317.

[95] Sun D, Lan Y, Xu E G, et al. Biochar as a novel niche for culturing microbial communities in composting [J]. Waste Management, 2016, 54:93-100.

[96] 張 頔,李龍威,王 鑫,等.生物炭對畜禽糞便好氧堆肥的影響研究進展[J]. 玉米科學, 2022,30(6):138-148. Zhang D, Li L W, Wang X, et al. Research progress on the effect of stalk biochar on livestock manure aerobic composting [J]. Journal of Maize Sciences, 2022,30(6):138-148.

[97] Wu J, Qi H, Huang X, et al. How does manganese dioxide affect humus formation during bio-composting of chicken manure and corn straw? [J]. Bioresource Technology, 2018,269:169-178.

[98] Wang S, Xu J, Zhang X, et al. Structural characteristics of humic-like acid from microbial utilization of lignin involving different mineral types [J]. Environmental Science and Pollution Research, 2019,26: 23923-23936.

[99] 蔡琳琳,李素艷,康 躍,等.沸石、膨潤土和過磷酸鈣對蚯蚓堆肥園林綠化廢棄物腐熟效果的影響[J]. 應用基礎與工程科學學報, 2020,28(2):299-309. Cai L L, Li S Y, Kang Y, et al. Effects of zeolite, bentonite and calcium superphosphate on the vermicomposting of green wastes [J]. Journal of Basic Science and Engineering, 2020,28(2):299-309.

[100]賈昊凝,李 艷,黎晏彰,等.礦物電子能量協(xié)同微生物胞外電子傳遞與生長代謝[J]. 微生物學報, 2020,60(9):2084-2105. Jia H L, Li Y, Li Y Z, et al. Mineral electronic energy cooperates with microbial extracellular electron transfer and growth metabolism [J]. Acta Microbiologica Sinica, 2020,60(9):2084-2105.

[101]Chen H, Koopal L K, Xiong J, et al. Mechanisms of soil humic acid adsorption onto montmorillonite and kaolinite [J]. Journal of Colloid and Interface Science, 2017,504:457-467.

[102]Zhang Y, Liu X, Zhang C, et al. A combined first principles and classical molecular dynamics study of clay-soil organic matters (SOMs) interactions [J]. Geochimica et Cosmochimica Acta, 2020, 291:110-125.

[103]Wang K, Xing B. Structural and sorption characteristics of adsorbed humic acid on clay minerals [J]. Journal of Environmental Quality, 2005,34(1):342-349.

[104]Pan C, Zhao Y, Zhao L, et al. Modified montmorillonite and illite adjusted the preference of biotic and abiotic pathways of humus formation during chicken manure composting [J]. Bioresource Technology, 2021,319:124121.

[105]Gonzalez J M, Laird D A. Role of smectites and Al-substituted goethites in the catalytic condensation of arginine and glucose [J]. Clays and Clay Minerals, 2004,52(4):443-450.

[106]Fernández-Calvi?o D, Rodríguez-Salgado I, Pérez-Rodríguez P, et al. Time evolution of the general characteristics and Cu retention capacity in an acid soil amended with a bentonite winery waste [J]. Journal of Environmental Management, 2015,150:435-443.

[107]Ren X, Wang Q, Zhang Y, et al. Improvement of humification and mechanism of nitrogen transformation during pig manure composting with Black Tourmaline [J]. Bioresource Technology, 2020,307:123236.

[108]Wang Q, Awasthi M K, Zhao J, et al. Improvement of pig manure compost lignocellulose degradation, organic matter humification and compost quality with medical stone [J]. Bioresource Technology, 2017, 243:771-777.

[109]鄭 威,周 紅,楊航波,等.海泡石添加對豬糞堆肥腐熟和水溶性有機質(zhì)的影響[J]. 農(nóng)業(yè)工程學報, 2021,37(1):259-266. Zheng W, Zhou H, Yang H B, et al. Effects of sepiolite addition on pig manure compost maturity and dissolved organic matter [J]. Transactions of the Chinese Society of Agricultural Engineering, 2021,37(1):259-266.

[110]Pan J, Li R, Zhai L, et al. Influence of palygorskite addition on biosolids composting process enhancement [J]. Journal of Cleaner Production, 2019,217:371-379.

Mechanism and regulation method of humic acid formation in composting-a review.

CHANG Yuan1,2, LI Ruo-qi1,2, LI Jun1,2, ZHAN Ya-bin3, WEI Yu-quan1,2*, XU Ting1,2, LI Ji1,2

(1.College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China；2.Organic RecyclingResearch Institute (Suzhou) of China Agricultural University, Suzhou 215100, China；3.Institute of Plant Protection and Soil Fertilizer, Hubei Academy of Agricultural Sciences, Wuhan 430064, China).2023,43(10)：5291～5302

The aim of this study was to review the mechanism of humic acid formation and the regulation method for improving the humification degree by process parameter optimization, the exogenous additives, and so on, in composting. The mechanisms of various regulation methods for accelerating humic acid formation process were also discussed, which provided theoretical basis for the development of fast composting technologies. Various regulatory methods may be interacted in applications due to the complex dynamic physiochemical environment factors in composting. Therefore, it is necessary to establish an integrated relationship among more factors related to humic acid formation based on practical compost production process. The future regulating methods will help to improve the quality of composting products.

humification；humic acid formation；rapid maturation；process parameters；new additives

X705

A

1000-6923(2023)10-5291-12

2023-03-05

國家自然科學基金資助項目(32071552);國家環(huán)境保護食品鏈污染防治重點實驗室開放課題基金(FC2022YB01);蘇州市科技計劃項目(SS20200);安徽省科技重大專項(202003a06020003)

* 責任作者, 副教授, weiyq2019@cau.edu.cn

常 遠(1999-),男,安徽馬鞍山人,中國農(nóng)業(yè)大學碩士研究生,主要從事生態(tài)工程與有機廢棄物資源化處理研究.發(fā)表論文3篇. chy491@cau.edu.cn.

常 遠,李若琪,李 珺,等.好氧堆肥腐殖酸形成機制及促腐調(diào)控技術概述 [J]. 中國環(huán)境科學, 2023,43(10):5291-5302.

Chang Y,LI R Q, LI J, et al. Mechanism and regulation method of humic acid formation in composting-a review [J]. China Environmental Science, 2023,43(10):5291-5302.