曹 云,黃紅英,吳華山,徐躍定,常志州

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豬糞稻秸超高溫預(yù)處理促進(jìn)后續(xù)堆肥腐殖化條件優(yōu)化

曹 云,黃紅英*,吳華山,徐躍定,常志州

(江蘇省農(nóng)業(yè)科學(xué)院循環(huán)農(nóng)業(yè)研究中心,農(nóng)業(yè)部種養(yǎng)結(jié)合重點(diǎn)實(shí)驗(yàn)室,江蘇 南京 210014)

以豬糞稻秸為原料,設(shè)計(jì)超高溫預(yù)處理溫度(75,85,95℃)、時(shí)間(2,4,8h)和通風(fēng)量(0.3,0.6,0.9L/kgTS·h)的三因素三水平正交試驗(yàn),研究不同超高溫預(yù)處理?xiàng)l件對(duì)豬糞稻秸理化特性及后續(xù)模擬堆肥腐殖質(zhì)生成的影響,結(jié)果表明,溫度、時(shí)間和通氣量對(duì)豬糞稻秸后續(xù)高溫堆肥腐殖化系數(shù)影響各不相同,各因素對(duì)后續(xù)好氧發(fā)酵累腐殖化系數(shù)的影響大小順序?yàn)榇笮№樞驗(yàn)轭A(yù)處理時(shí)間>溫度>通氣量; 最佳超高溫預(yù)處理?xiàng)l件為:預(yù)處理溫度為95℃,停留時(shí)間為4h,通氣量為0.6L/(kgTS·h),與CK相比,最佳預(yù)處理參數(shù)下豬糞稻秸后續(xù)高溫發(fā)酵60d腐殖化系數(shù)提高119%,腐殖質(zhì)、胡敏酸含量分別增加105%、116%,而富里酸含量降低17.2%,結(jié)合預(yù)處理前后物料理化特性變化規(guī)律分析,表明超高溫預(yù)處理促進(jìn)了大分子有機(jī)物降解為可溶性有機(jī)碳,促進(jìn)了木質(zhì)纖維素組分降解溶出,促使其更多轉(zhuǎn)化為多酚,同時(shí)增加了腐殖質(zhì)前體還原糖、氨基酸的含量,從而有利于腐殖質(zhì)的生成.

堆肥；腐殖質(zhì)；前體物質(zhì)；正交試驗(yàn)

隨著畜禽養(yǎng)殖業(yè)的發(fā)展,中國每年產(chǎn)生的畜禽廢棄物多達(dá)38億t,畜禽糞便已經(jīng)成為中國最主要的污染源之一[1],生物發(fā)酵是實(shí)現(xiàn)其資源化利用的主要手段,高溫好氧堆肥不僅能去除臭味、有毒有害物質(zhì)和病原菌[2],而且發(fā)酵產(chǎn)物可作為優(yōu)質(zhì)有機(jī)肥還田利用,實(shí)現(xiàn)養(yǎng)分的循環(huán)利用[3-4],堆肥化過程中,有機(jī)物由不穩(wěn)定狀態(tài)轉(zhuǎn)化為穩(wěn)定的腐殖質(zhì)物質(zhì),根據(jù)最廣為認(rèn)可的腐殖質(zhì)形成理論,腐殖質(zhì)由木質(zhì)素、蛋白質(zhì)及其分解中間產(chǎn)物,在微生物或其分泌的酶的作用下發(fā)生聚合而成.可見,木質(zhì)纖維素類物質(zhì)的降解與腐殖質(zhì)的形成關(guān)系密切[5],但由于畜禽廢棄物中多含有木質(zhì)纖維素等物質(zhì)難降解物質(zhì),采用傳統(tǒng)堆肥工藝生產(chǎn)周期長,腐殖化進(jìn)程緩慢[6-7],超高溫(75℃>>100℃)預(yù)處理是濕熱預(yù)處理的一種,即在常壓下,通過高溫改變畜禽廢棄物的理化性質(zhì),從而提高其省生物可利用性的預(yù)處理方法[8-9],研究表明,超高溫預(yù)處理改變物料中碳水化合物、蛋白質(zhì)、及木質(zhì)纖維素的理化性質(zhì),預(yù)處理過程中復(fù)雜的碳水化合物轉(zhuǎn)化為多糖、還原糖,部分蛋白質(zhì)被降解為氨基酸,纖維素轉(zhuǎn)化為多酚[10-11],提高后續(xù)生物處理效率,為后續(xù)堆肥過程中腐殖質(zhì)的生成提供了前體物質(zhì),因而可有效縮短畜禽糞便的堆肥腐熟周期,提高腐殖化進(jìn)程[8].

超高溫預(yù)處理過程中,大部分嗜溫微生物被殺死,僅有少數(shù)嗜熱微生物存活,在后續(xù)堆肥過程中逐步繁殖[12].成為后續(xù)堆肥的主體[13].可見,在超高溫預(yù)處理堆肥工藝中,即使不接種外源微生物,堆肥原料中的嗜熱菌也能成為后續(xù)堆肥的內(nèi)源接種劑,完成堆肥過程中有機(jī)物的降解.但接種微生物,尤其是嗜熱菌可以進(jìn)一步提高發(fā)酵溫度和升溫速率,加速堆肥腐熟[14-15].

相對(duì)于常規(guī)堆肥,全程超高溫堆肥或超高溫預(yù)處理堆肥工藝盡管存在能源消耗大、預(yù)處理過程氨揮發(fā)等缺陷,但由于其能提高堆肥廠單位面積產(chǎn)能,有效節(jié)省土地面積,因而綜合成本并不高.Yu等采用城市污泥超高溫堆肥的研究結(jié)果表明,處理1t新鮮污泥,超高溫堆肥和傳統(tǒng)堆肥所需的場(chǎng)地面積分別為45,80m2,綜合處理成本比傳統(tǒng)堆肥少5$/t[13], Yamada等[12]研究表明,超高溫預(yù)處理的3h過程中,牛糞中80~100%的氨被去除,因此后續(xù)堆肥過程中沒有檢測(cè)到氨揮發(fā)及其他惡臭氣體的排放.前期結(jié)果也表明,超高溫預(yù)處理堆肥62%的氮素?fù)p失發(fā)生在預(yù)處理階段,整體氮損失率比常規(guī)堆肥降低28.9%[8].

目前,國內(nèi)外學(xué)者對(duì)對(duì)超高溫堆肥腐熟過程、氮素?fù)p失進(jìn)行了一些研究,但對(duì)超高溫預(yù)處理對(duì)后續(xù)堆肥腐殖化影響的研究較少,尤其是預(yù)處理后腐殖質(zhì)生成與轉(zhuǎn)化規(guī)律的研究鮮見報(bào)道,鑒于此,本研究采用超高溫預(yù)處理方法,研究不同預(yù)處理?xiàng)l件(溫度、時(shí)間、通氣量)對(duì)畜禽廢棄物理化性質(zhì)及腐殖質(zhì)形成的影響,以及不同腐殖質(zhì)前體物質(zhì)的轉(zhuǎn)化規(guī)律,通過優(yōu)選最佳預(yù)處理工藝組合,為提高畜禽廢棄物堆肥效率提供技術(shù)支撐.

1 材料與方法

1.1 試驗(yàn)材料

供試豬糞取自江蘇省農(nóng)業(yè)科學(xué)院六合動(dòng)物試驗(yàn)基地,秸稈取自江蘇省農(nóng)業(yè)科學(xué)院試驗(yàn)田自然條件下風(fēng)干后的水稻秸稈,經(jīng)破碎處理成5mm左右的顆粒粉末.堆肥原料的基本理化性質(zhì)見表1.

表1 堆肥原料基本性狀

1.2 超高溫預(yù)處理正交試驗(yàn)

為了研究豬糞稻秸超高溫預(yù)處理的影響因素,本試驗(yàn)選擇了3個(gè)相關(guān)因素進(jìn)行條件優(yōu)化試驗(yàn),分別為預(yù)處理時(shí)間、預(yù)處理溫度和通風(fēng)量,并根據(jù)前期預(yù)實(shí)驗(yàn)結(jié)果確定出各因素水平值范圍:預(yù)處理溫度為75~95℃,預(yù)處理時(shí)間為2~8h,通氣量為0.3~ 0.9L/(kgTS·h),試驗(yàn)設(shè)計(jì)3因素3水平的正交試驗(yàn),另設(shè)置對(duì)照組CK(即豬糞稻秸不預(yù)處理),共計(jì)10個(gè)處理組(表2),各處理組試驗(yàn)重復(fù)3次.原料預(yù)處理在自制的超高溫堆肥反應(yīng)器中進(jìn)行,反應(yīng)器有效容積為30L,每次預(yù)處理時(shí),原料裝樣量為10kg新鮮豬糞和1.6kg風(fēng)干稻秸,物料初始含水率為約為60%,按照表2中各因素水平進(jìn)行試驗(yàn)操作,處理完畢后取出并自然冷卻,放置于4℃冰箱保存,待所有樣品預(yù)處理結(jié)束后置于2L的塑料桶,進(jìn)行模擬堆肥試驗(yàn).

表2 正交試驗(yàn)設(shè)計(jì)

注:/表示對(duì)照,不經(jīng)過預(yù)處理直接堆肥.

1.3 模擬堆肥試驗(yàn)

模擬堆肥試驗(yàn)在人工控溫箱中進(jìn)行,堆肥時(shí)間為60d,堆肥期間每個(gè)堆肥處理3個(gè)重復(fù).以不經(jīng)過預(yù)處理的原料為對(duì)照,每5 天翻動(dòng)一次以補(bǔ)充氧氣,根據(jù)前期試驗(yàn)結(jié)果[8],堆肥過程中的溫度控制設(shè)置如圖1所示,試驗(yàn)開始后,在堆肥的第0,7,28,42,60d分別取樣,在翻堆的同時(shí),在上、中、下3 部位分別取鮮樣,每次取樣100g.

圖1 模擬堆肥溫度控制

1.4 測(cè)定指標(biāo)及方法

將取回的堆肥樣品分成2份,一份新鮮樣品用于含水量、pH值、可溶性有機(jī)碳(DOC)的測(cè)定;一份置于陰涼處風(fēng)干、粉碎、過篩(100 目),用于有機(jī)質(zhì)、腐殖質(zhì)、游離氨基酸、還原糖、多酚、纖維素、半纖維素、木質(zhì)素含量的測(cè)定,含水量采用105℃烘干法; pH值測(cè)定采用肥水質(zhì)量比1:5浸提,ORION酸度計(jì)測(cè)定;氨基酸的測(cè)定采用茚三酮比色法[16];還原糖的測(cè)定采用DNS法[17];多酚的測(cè)定采用沸水浸提-福林酚試劑法[18],采秸纖維素、半纖維素和木質(zhì)素采用范氏法(Van Soest)測(cè)定(FIWE,Velp Scientifica)[19];用重鉻酸鉀油浴法測(cè)定有機(jī)碳[20],堆肥腐殖質(zhì)碳的測(cè)定采用0.1mol/L NaOH+0.1mol/L Na2P2O7(體積比為1:1)提取,TOC儀測(cè)定樣品中的腐殖酸碳[21],腐殖化系數(shù)(HI)是堆肥過程中胡敏酸碳的質(zhì)量分?jǐn)?shù)與總腐殖質(zhì)碳質(zhì)量分?jǐn)?shù)的比值HI= HA-C/HS-C[22].

2 結(jié)果與分析

2.1 不同超高溫預(yù)處理工藝參數(shù)對(duì)畜禽糞便理化特性的影響

表3 超高溫預(yù)處理前后畜禽糞便理化特性的變化

注:采用Duncan方法分析,同列標(biāo)有不同小寫字母者表示組間差異顯著(<0.05,=3).

由表3可以看出,與CK相比,經(jīng)不同的超高溫預(yù)處理后,豬糞稻秸水浸提液pH值均有顯著下降,其中處理6的pH值下降幅度最大,由初始的7.56下降至6.92.前期研究表明,預(yù)處理后物料pH值的降低主要與大分子物質(zhì)水解生成揮發(fā)性有機(jī)酸有關(guān)[8].經(jīng)超高溫預(yù)處理的后續(xù)堆肥中,可溶性有機(jī)碳較CK也有不同程度的增加,其中處理3增加幅度達(dá)顯著水平.朱金龍等[9]研究表明,隨著濕熱預(yù)處理溫度的增加和時(shí)間延長,有機(jī)廢棄物固相顆粒物逐步水解,液相中有機(jī)碳的質(zhì)量濃度不斷升高.預(yù)處理后,纖維素、半纖維素含量均有不同程度的降低,木質(zhì)素含量均增加.從各處理間變化幅度來看,與CK相比,以處理3 木質(zhì)纖維素含量變幅最大,其中纖維素和半纖維素含量分別降低了5.1%和4.9%,木質(zhì)素含量提高了17.2%.杜靜等[19]對(duì)稻秸進(jìn)行了溫和水熱預(yù)處理研究,結(jié)果表明,預(yù)處理后稻秸木質(zhì)素含量增加主要是纖維素、半纖維素含量降低形成的"濃縮”效應(yīng).纖維素、半纖維素含量這與方差分析表明,除處理3中各理化特性指標(biāo)與處理CK均呈現(xiàn)極顯著差異外,其余處理僅有部分指標(biāo)呈現(xiàn)顯著差異.以上結(jié)果表明,不同超高溫預(yù)處理促進(jìn)豬糞稻秸有機(jī)物大量溶出,pH 值下降,對(duì)豬糞稻秸木質(zhì)纖維素組分有一定程度降解,但不同預(yù)處理工藝對(duì)豬糞秸稈木質(zhì)纖維組分降解效果影響不同,以處理3工藝參數(shù)條件下的預(yù)處理效果最為明顯.

2.2 不同超高溫預(yù)處理工藝參數(shù)對(duì)豬糞稻秸后續(xù)堆肥腐殖化進(jìn)程的影響

2.2.1 正交試驗(yàn)結(jié)果與分析 表征堆肥腐殖化程度的指標(biāo)較多,由于胡敏酸(HA)是腐殖質(zhì)中分子量較大、是分子結(jié)構(gòu)穩(wěn)定性較高的組分,是評(píng)價(jià)堆肥腐殖質(zhì)質(zhì)量與穩(wěn)定性的重要指標(biāo)[23-24],HA含量升高能在一定程度上指示堆肥的腐殖化,因此本試驗(yàn)采用腐殖化系數(shù),即胡敏酸占總腐殖質(zhì)的質(zhì)量分?jǐn)?shù)來評(píng)價(jià)堆肥的腐殖化程度,設(shè)計(jì)L9(34)的正交試驗(yàn),對(duì)預(yù)處理后豬糞稻秸后續(xù)模擬高溫發(fā)酵60d腐殖化系數(shù)進(jìn)行極差分析,從表4中可以看出:試驗(yàn)組3堆制60d后腐殖化系數(shù)最高,為2.16,較CK提高了125%;試驗(yàn)組9的后續(xù)堆肥腐殖化系數(shù)最低(0.89),預(yù)處理組后續(xù)堆肥腐殖化系數(shù)平均比CK增加57.7%.從值可以得出最佳預(yù)處理工藝參數(shù)組合為B2A3C2,即預(yù)處理溫度為95℃,停留時(shí)間為4h,通氣量為0.6L/ (kgTS·h),

對(duì)正交試驗(yàn)結(jié)果進(jìn)行方差分析,從表5中各因素對(duì)應(yīng)的值大小可以得出,預(yù)處理溫度、時(shí)間和通氣量3個(gè)因素對(duì)豬糞稻秸后續(xù)高溫發(fā)酵腐殖化系數(shù)的影響程度各不相同,各因素對(duì)后續(xù)堆肥腐殖化系數(shù)(HA/FA)影響大小順序?yàn)锽>A>C,即預(yù)處理時(shí)間>溫度>通氣量.

2.2.2 總有機(jī)碳(TOC)和可溶性有機(jī)碳(DOC)含量的變化 堆肥過程中總有機(jī)碳、可溶性有機(jī)碳含量變化趨勢(shì)相似,CK呈現(xiàn)先上升后下降趨勢(shì),而處理組主要呈下降趨勢(shì),與初始TOC值相比,CK下降了2%,而處理組TOC含量平均下降了11.7%(圖2A),說明在好氧堆肥中有機(jī)質(zhì)的分解速度大于合成速度,而超高溫預(yù)處理加快了后續(xù)堆肥不穩(wěn)定有機(jī)質(zhì)的分解,更快地形成腐殖質(zhì),促進(jìn)了堆肥的腐殖化進(jìn)程,這與Yamada等[12]、Kanazawa等[24]的研究結(jié)果一致,CK可溶性有機(jī)碳含量在第14d達(dá)到最大,比初始含量提高了25.2%,14~28d內(nèi)下降了27.1%,之后DOC值穩(wěn)定在40g/kg左右,說明堆肥前期微生物分解生成的DOC不穩(wěn)定,處理組DOC含量在0~14d內(nèi)較初始值平均下降了58.5%,較28~42d的降幅(42.3%)高,這主要是因?yàn)槎逊是捌谖⑸锘钴S,有機(jī)物分解加劇,42d后,除了處理1和處理8外,其他各處理DOC含量呈持續(xù)下降趨勢(shì),下降幅度為32.8~68.5%,整體而言,堆肥過程中CK的DOC含量顯著高于其他處理組,說明超高溫預(yù)處理堆肥有機(jī)質(zhì)穩(wěn)定速率高于CK.

表4 正交試驗(yàn)結(jié)果

注:1、2、3分別表示溫度、停留時(shí)間、通氣量三個(gè)因素下對(duì)應(yīng)水平為1、2、3的腐殖化系數(shù)和,表示每個(gè)因素下的最大值減最小值.

表5 方差分析

2.2.3 后續(xù)發(fā)酵過程中腐殖化進(jìn)程 腐殖物質(zhì)(HS)是有機(jī)物料在微生物與酶的作用下形成的一類由一系列分子構(gòu)成的聚合物,它一般是由1 到多個(gè)芳香核附以多種活性官能團(tuán)構(gòu)成,堆肥過程中腐殖質(zhì)含量變化規(guī)律不一致,與堆肥原料與堆肥工藝參數(shù)有關(guān)[25],本研究利用畜禽糞便和稻秸為主要原料進(jìn)行的堆肥試驗(yàn),結(jié)果表明,HS含量均表現(xiàn)為先增加后下降的趨勢(shì),HS含量在2~5d左右達(dá)到最大值,之后逐漸降低,這與魏自民等[26]、Zhou等[27]的研究結(jié)果一致,堆肥初期,腐殖物質(zhì)合成能力極強(qiáng),HS形成數(shù)量達(dá)到峰值;隨后由于分解速度大于形成速度,HS質(zhì)量分?jǐn)?shù)呈現(xiàn)下降的趨勢(shì)并趨于穩(wěn)定,堆肥過程中新HS形成的同時(shí),原有的HS也在不斷被礦化[28].堆肥60d時(shí), S7(85℃,8h)以及95℃試驗(yàn)組HS含量均高于CK,其中S3處理比CK高出105%,這可能是因?yàn)楦邷馗欣诖龠M(jìn)木質(zhì)纖維素的溶出以及粗蛋白的降解[29].

堆肥過程中胡敏酸(HA)質(zhì)量分?jǐn)?shù)有一定的波動(dòng),說明在堆肥過程中伴隨著HA的形成,HA又向富里酸轉(zhuǎn)化,兩個(gè)過程同時(shí)進(jìn)行[30],超高溫預(yù)處理對(duì)HA含量的影響不同,75℃處理組HA質(zhì)量分?jǐn)?shù)顯著高于CK,而85,95℃處理組HA質(zhì)量分?jǐn)?shù)顯著低于CK,但兩個(gè)溫度處理組之間無顯著差異,處理間比較,堆肥結(jié)束時(shí),95℃處理組HA質(zhì)量分?jǐn)?shù)比CK高41.3%,S3處理(95℃,4h)HA質(zhì)量分?jǐn)?shù)最高,比CK提高了116%,而85,75℃處理組HA質(zhì)量分?jǐn)?shù)與CK無顯著差異,4h處理組HA平均質(zhì)量分?jǐn)?shù)比CK高47.7%,而2h處理組HA平均質(zhì)量分?jǐn)?shù)比CK低26.0%,8h處理組HA平均質(zhì)量分?jǐn)?shù)與CK無顯著差異,說明不同處理時(shí)間及溫度對(duì)HA形成影響不同,本試驗(yàn)條件下預(yù)處理溫度越高,越有利于后續(xù)堆肥HA的形成.

堆肥過程中,富里酸(FA)總體呈下降趨勢(shì),堆肥初期,95,85℃處理組FA含量與對(duì)照差異不顯著,而75℃處理組FA含量比對(duì)照低33.8%(<0.05).堆肥結(jié)束時(shí),與初期相比,75,85,95℃各處理組的FA分別下降了2.6%、43.9%、40.8%,S3處理FA比對(duì)照降低17.2%.堆肥中后期FA含量的下降主要是其轉(zhuǎn)化為HA所致.

腐殖化系數(shù)(HI)是胡敏酸和富里酸的比值,是評(píng)價(jià)堆肥腐殖化水平的一個(gè)重要指標(biāo),能較好的反應(yīng)堆肥腐殖質(zhì)組分性質(zhì)的變化[22-23],如圖3所示,堆肥初期,除了75℃處理組,其余處理組與CK腐殖化系數(shù)差異不顯著,堆肥過程中,HI變化趨勢(shì)與HA相似,堆至60d時(shí),各處理HI出現(xiàn)不同程度的增加,75, 85,95℃處理組HI分別較CK高出58.9%、45.8%、91.2%;2,4,8h處理組HI分別較CK高出46.6%、111.8%、39.6%,說明超高溫預(yù)處理提高了后續(xù)堆肥的腐殖化, Yamda等[12]研究也表明,采用60~100℃高溫處理牛糞過程中,腐殖化指數(shù)顯著增加.

2.2.4 后續(xù)發(fā)酵過程中腐殖質(zhì)前體物質(zhì)變化 根據(jù)腐殖質(zhì)形成的多酚學(xué)說,多酚是腐殖質(zhì)形成的基本步驟[31],本研究中,與CK相比,除S2(75℃、2h)、S4(75℃、4h),其余處理均增加了堆肥初始物料的多酚含量,平均增幅為14.3%,堆肥開始后,呈先上升后下降趨勢(shì),至堆肥14d,各處理多酚含量均有不同程度上升,預(yù)處理溫度為75,85,95℃的平均多酚含量分別比初始增加39.1%、71.9%、14.9%.14d后,CK及S1、S4、S7、S8、S9處理(75℃和85℃預(yù)處理)多酚含量迅速下降,其余處理多酚含量繼續(xù)增加,直至堆肥35d后,所有堆肥處理多酚含量均呈下降趨勢(shì),堆肥結(jié)束時(shí),與起始值相比,CK中多酚濃度下降了21.7%,各預(yù)處理堆體多酚濃度下降幅度為58.9%~ 85.0%(圖4A),說明堆肥結(jié)束時(shí),大部分多酚已轉(zhuǎn)化為腐殖質(zhì),芳構(gòu)化程度增加[32-33].

氨基酸(AA)是腐殖質(zhì)形成的前體物質(zhì)之一[34],超高溫預(yù)處理增加了堆肥原料中AA的含量,比對(duì)照平均增加了10.9%,堆肥初期,S1(85℃,4h)、S3 (95℃,4h)處理AA濃度最高,分別為170.04, 170.06mg/kg,并顯著高于S8(85℃,2h)、S9(75℃,8h),說明濕熱處理溫度較高,更有利于豬糞中的粗蛋白水解生成AA[10].

還原糖是美拉德反應(yīng)途徑中HAs 形成的重要構(gòu)成因素[31]與CK相比,75℃的三個(gè)處理物料還原糖含量均比對(duì)照低, 85,95℃處理的平均還原糖含量分別比CK高5.6%、14.6%.后續(xù)堆肥開始后,還原糖含量呈先下降后上升趨勢(shì),主要與強(qiáng)烈的微生物活動(dòng),消耗大量的碳源有關(guān)[35](圖4C).

2.2.5 多酚、還原糖、氨基酸濃度與腐殖質(zhì)形成的相關(guān)性 多酚、還原糖、游離氨基酸作為腐殖質(zhì)形成的重要前體物質(zhì),在腐殖質(zhì)形成過程中發(fā)揮的作用體現(xiàn)于兩者濃度的相關(guān)性分析上,表6可知,胡敏酸、富里酸作為腐殖質(zhì)的重要組分,其含量與腐殖質(zhì)含量均極顯著正相關(guān)(<0.01).多酚、還原糖、游離氨基酸含量與腐殖質(zhì)含量呈顯著負(fù)相關(guān),其中多酚、還原糖與腐殖質(zhì)的相關(guān)性達(dá)顯著水平(<0.05),而游離氨基酸含量與腐殖質(zhì)相關(guān)性不顯著,腐殖質(zhì)形成多酚途徑理論認(rèn)為,多酚類物質(zhì)是腐殖質(zhì)形成的主要構(gòu)件,所以多酚含量的降低是因?yàn)楹铣闪烁迟|(zhì)[31],Baddi等[36]研究也表明,假木質(zhì)素降解產(chǎn)物多酚類化合物,經(jīng)歷了重組和分子的縮合,在腐殖質(zhì)形成中起關(guān)鍵作用,多酚類物質(zhì)的減少,以及腐殖質(zhì)的增加是支持多酚類物質(zhì)作為腐殖質(zhì)形成的原始前體,這與本研究結(jié)果相符,糖-胺理論認(rèn)為,腐殖質(zhì)主要是由微生物代謝所產(chǎn)生的還原糖與氨基酸以氫鍵相連進(jìn)行非酶聚合作用形成的聚合物[37],此外,還原糖還可為富里酸轉(zhuǎn)化為胡敏酸的微生物活動(dòng)過程提供重要碳源和能源,魏自民等[34]研究表明,堆肥過程中游離氨基酸濃度與腐殖質(zhì)濃度呈顯著負(fù)相關(guān)關(guān)系,表明游離氨基酸對(duì)腐殖質(zhì)的形成促進(jìn)作用明顯.本研究中,氨基酸與腐殖質(zhì)相關(guān)性未達(dá)到顯著,可能是因?yàn)?以畜禽糞便為主要原料的堆肥過程中,粗蛋白分解產(chǎn)生大量游離氨基酸,粗纖維和粗脂肪含量等構(gòu)成腐殖質(zhì)的核心碳源的結(jié)構(gòu)較少,使氨基酸對(duì)腐殖質(zhì)的形成促進(jìn)作用不明顯[34].

表6 腐殖質(zhì)不同組分與多酚、還原糖、游離氨基酸含量的相關(guān)性

注:*,**分別表示相關(guān)性分別達(dá)顯著(<0.05)和極顯著水平(<0.01).

3 結(jié)論

3.1 在超高溫預(yù)處理過程中,時(shí)間是影響后續(xù)堆肥腐殖化進(jìn)程的主控因子,其次是溫度,通風(fēng)量沒有顯著影響.

3.2 不同超高溫預(yù)處理?xiàng)l件對(duì)后續(xù)腐殖質(zhì)生成有顯著影響,豬糞稻秸經(jīng)超高溫預(yù)處理后,后續(xù)堆肥中腐殖化系數(shù)明顯提高,平均增幅為57.7%,其中95℃、4h預(yù)處理?xiàng)l件下最高,達(dá)到2.16,

3.3 超高溫預(yù)處理增加堆肥腐殖化水平與促進(jìn)腐殖質(zhì)前體物質(zhì)生成有關(guān).超高溫預(yù)處理促進(jìn)了豬糞稻秸有機(jī)物的溶出.與CK相比,預(yù)處理組多酚、氨基酸含量分別比CK高出14.3%、10.9%; 85, 95℃處理的平均還原糖含量分別比CK高5.6%、14.6%.

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Optimization of conditions for promotion of humic substance formation during subsequent composting with hythermal pretreatment for pig manure and rice straw.

CAO Yun, HUANG Hong-ying*, WU Hua-shan, XU Yue-ding, CHANG Zhi-zhou

(1.Circular Agricultural Research Center,Jiangsu Academy of Agricultural Sciences, Key Laboratory of Crop and Livestock Integrated Farming, Ministry of Agriculture, Nanjing 210014)., 2019,39(5)：2055~2062

The influences of hyperthermophilic pretreatment on physico-chemical properties and the formation of humic substances during the subsequent composting of pig manure and rice straw were investigated using an orthogonal experiment, The orthogonal experiment containing three factors, each with three levels, were conducted under different temperatures (75, 85, 95°C), heating intervals (2, 4, 8h) and ventilation (0.3, 0.6, 0.9L/kg TS·h), The results showed these three factors had different effects on the humification coefficient of the subsequent aerobic composting, The size of effects on the humification coefficient during the subsequent aerobic composting was in the order of pretreatment time, followed by temperature ventilation, The optimal hyperthermal pretreatment conditions were: 95°C for the temperature, 4h for the heating time and the aeration rate was 0.6L/kg TS·h, Compared with the control (CK), the humification coefficient of subsequent composting with pig manure and rice straw was increased by 119% under the optimal pretreatment conditions, The contents of total humic substance and humic acid were increased by 105% and 116%, respectively, while the fulvic acid content was decreased by 17.2%, Based on the variations of the physico-chemical characteristics before and after hyperthermal pretreatment, the results suggested that the hyperthermal pretreatment could promote the degradation of macromolecular organic matter into soluble organic carbon and degrade lignocellulosic components into to polyphenols, The precursors, such as the reduced sugars and amino acids, were also increased, which would in turn facilitate the formation of humic substances in composting.

compost；humic substance；precursors；orthogonal test

X713

A

1000-6923(2019)05-2055-08

曹 云(1981-),女,江蘇丹陽人,副研究員,博士,主要從事農(nóng)業(yè)廢棄物資源化研究.發(fā)表論文20余篇.

2018-10-10

國家水體污染控制與治理科技重大專項(xiàng)(2017ZX07202004);國家自然科學(xué)基金資助項(xiàng)目(41701340);江蘇省農(nóng)業(yè)自主創(chuàng)新項(xiàng)目(CX (17)2024);南京市農(nóng)業(yè)科技產(chǎn)學(xué)研合作示范項(xiàng)目(2018RHJD11)

*責(zé)任作者, 研究員, sfmicrolab@163.com