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NGHIN CU SN XUT THAN SINH HC T RM R V TRU PHC V

NNG CAO PH T, NNG SUT CY TRNG V GIM PHT THI KH

NH KNH1

Mai Vn Trnh2, Trn Vit Cng2,

V Dng Qunh2, Nguyn Th Hoi Thu 2

Produce biochar from rice straw and rice husk to improve soil fertility, crop yields and

reduce greenhouse gas emissions

Analyze results of the rice residue showed that total carbon, organic carbon content

and potassium in rice straw is higher than in rice husk. In contrast, nitrogen and P2O5 in the

rice straw is lower than rice husk. With rice husk, biochar produced by canned combustion in

barrel (PP3) has total carbon, organic carbon, nitrogen and P2O5 higher than from open

burning methods (PP1 and PP2). With rice straw, biochar produced by canned combustion in

barrel (PP7) has total carbon, organic carbon, nitrogen and K2O higher than open burning

methods (PP4, PP5 and PP6). Recovery ratio of total carbon from rice straw is lower than

from rice husk, in which the highest recovery ratio of total carbon are from indirect pyrolysis.

Key words: rice straw, rice husk, biochar, pyrolysis.

1. M u

Than sinh hc (TSH) l thut ng dng ch cc bon en (black carbon) hay biochar,

c to ra t qu trnh nhit phn cc vt liu hu c trong mi trng khng c hoc ngho

xy khng xy ra phn ng chy. N ang c nhiu nh khoa hc trn th gii v nh l

vng en cho ngnh nng nghip. TSH c th to ra t nhiu ph ph phm trong nng

nghip khc nhau nh rm r, v tru, v ht, b ma v.v... Sau mi v thu hoch, mt lng

ln ph ph phm nng nghip b t chy hoc phn hy gii phng CO2 v CH4 vo kh

quyn gy nn s nhim khi bi v hiu ng kh nh knh (IPCC, 2007). Qu trnh nhit

phn to TSH, cc bon c trong vt liu hu c khng b mt i hon ton m tn ti dng

kh b phn gii bi cc yu t mi trng ca t. S dng nhng vt liu trn to TSH

bn vo t khng ch gim nhim mi trng, m cn gip tng cng trao i cation, kh

nng gi nc, dng cht v bo v vi khun c li cho t, tng sc sn xut ca t trng,

m bo an ninh lng thc, gim lng phn bn va ng vai tr nh b cha carbon t

nhin trong mi trng t. c bit n rt d lm v c mt chi ph thp.

Vit Nam c mt tim nng sinh khi ng k l nhng ph ph phm nng nghip.

Theo c tnh Vit Nam vi sn lng la l 38 triu tn/nm (GSO, 2009) th s c tng

ng 38 triu tn rm r, 6-7 triu tn tru. Ngoi la cn c khong 1,4 triu tn l ma (ch

tnh lng nng dn t ti rung) v mt lng khng nh cc ngun ph phm khc nh

c, l, mn ca, b ma y l ngun vt liu rt phong ph v y ha hn cho sn xut

TSH phc v cuc sng.

1 Bi vit do PGS. TS. Nguyn Vn Vit phn bin, c ng trn Tp ch Khoa hc v Cng ngh Nng

nghip Vit Nam (ISSN 1859-1558) s 3(24) 2011 2 Vin Mi trng Nng nghip

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Xut pht t thc t nu trn, bi vit ny m t cc th nghim v phn tch nh gi

tm ra phng php sn xut TSH ti u t tru v rm r, d dng p dng vng nng thn

Vit Nam.

2. Vt liu v phng php nghin cu

Cc phng php (PP) sn xut TSH c th nghim t thng 1 n thng 8 nm

2010 ti Vin Mi trng Nng nghip. Mi PP c lp li t nht 3 ln, mi ln s dng t

5 10 kg vt liu (rm r v tru).

TSH c sn xut bng cc PP sau:

PP 1: t tru: y l phng php sn xut TSH theo cch c truyn m ngi dn

vn lm l to mt nhn nhit gia, sau trm tru mi ln trn nhn tru. Sau khi lp

tru bn ngoi chuyn thnh mu en th tin hnh thm hi nc kt thc phn ng chy.

PP 2: t tru ci tin: Lm nh phng php mt nhng t ng khi gia v ph

tru xung quanh. ng khi c tc dng tng tc c chy v gim thi gian sn xut TSH.

PP 3: t tru gin tip: L t c thit k lm 2 khoang, khoang gia c nht

vt liu cn sn xut than khng tip xc vi la, khoang bn ngoi dng cha cc vt liu

t to nhit. Khi vt liu khoang ngoi chy s to 1 nhit nng ln chuyn ha carbon t

vt liu hu c khoang trong thnh TSH. Phn ng chy ca l t kiu ny c th xy ra

trong thi gian khong 4h.

PP 4: t rm r: TSH c to t rm r ging nh phng php 1 v phn ng

chy c gim st cht ch mc khng xut hin ngn la v c can thip kp thi bng

hi m khi ton b lng carbon c chuyn sang TSH c mu en.

PP 5: t rm r ci tin: Rm r c cho vo my phay, cht ngn hn 2cm, phi

kh v t nh phng php 4.

PP 6: t rm r trong bung kn: rm r kh c nhi trong bung t c dung tch

nht nh c gn ng khi. Di chn bung t c 2 ca nhm la i xng nhau. Tin hnh

nhm la v y ca l rm chy m . i khi rm chy ym kh gn xong, tin hnh o

ngc bung vt liu chy ht, ra ngoi v dng hi nc dp tt qu trnh chy.

PP 7: t rm r gin tip: L t c lm tng t nh phng php 3 nhng vt

liu cho vo khoang gia l rm r thay v tru.

Hnh 1: Th nghim sn xut TSH t rm r, tru theo phng php gin tip

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o m, tnh ton: p dng cho tt c 7 phng php

Vt liu trc khi t v sn phm sau khi t c xc nh bng cch ly mu v

phn tch cc ch tiu cc bon tng s (TC, %); cc bon hu c tng s (TOC, %) phn tch

bng h thng phn tch Multi N/C2100S - Analytik- jena, c; N (%) theo phng php

Keldalh; P2O5 (%) theo phng php Bray 2; K2O (%) theo phng php t bng Quang k

ngn la.

3. Kt qu nghin cu

Nghin cu th nghim cc phng php sn xut TSH t vt liu rm r v tru n

gin hiu qu v d dng p dng vi nng dn. Mi phng php u c u v nhc im

ring. Vi cc phng php n gin, khng tn nguyn vt liu v thi gian thc hin th

cho hm lng cc bon thu c thp. Ngc li mt s phng php tn thi gian v

nguyn vt liu hn li thu c hm lng cc bon cao hn. T nhng nghin cu cho ra

mt s kt qu nh sau:

Bng 1: Kt qu phn tch vt liu v TSH trong nghin cu

STT KHM M t phng php TC

(g/kg)

TOC

(g/kg) N% P2O5% K2O%

Hiu sut

thu hi TC

(%)

1 Tru Trc t 228,2 105,5 0,17 1,16 0,43

2 Rm Trc t 552,0 237,2 0,07 0,27 0,81

3 PP1 t tru 256,3 31,9 0,05 0,28 0,58 33,69

4 PP2 t tru ci tin 335,9 27,6 0,02 0,33 0,77 44,16

5 PP3 t tru ci tin 340,5 41,9 0,07 0,39 0,78 44,76

6 PP4 t rm r 343,7 10,2 0,16 0,53 0,55 18,68

7 PP5 t rm r ci tin 353,8 121,2 0,17 0,85 0,62 19,23

8 PP6

t rm r trong bung

kn 316,0 130,4 0,19 0,34 0,72 17,17

9 PP7 t rm r gin tip 524,5 215,6 0,24 0,47 0,81 28,51

Trc khi t, lng cc bon tng s v cc bon hu c tng s trong rm c gi tr

ln hn so vi hm lng c trong tru, tng ng cacbon tng s trong rm l: 552,00 g/kg

v trong tru l: 228,20g/kg. Vi hm lng cc bon hu c tng s c trong rm l

237,2g/kg v hm lng c trong tru l 105,5g/kg.

Cc phng php khc nhau cho hm lng cacbon thu c l khc nhau.

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i vi TSH lm t tru (cc phng php PP1, PP2 v PP3): Hm lng TC ca cc

phng php c xp theo th t PP3>PP2>PP1 nhng hm lng TOC li theo th t

PP3>PP1>PP2. Hiu sut thu hi C phng php 3 cng l cao nht vi t l 44,76%.

i vi TSH lm t rm (cc phng php PP4, PP5, PP6 v PP7) th hm lng TC

sp xp theo th t PP7>PP5>PP4>PP6 v hm lng TOC c sp xp theo th t

PP7>PP6>PP5>PP4, trong hiu sut thu hi cc bon PP7 l cao nht vi t l l 28,51%.

Hm lng cc nguyn t dinh dng c trong TSH cng khc nhau theo cc phng

php sn xut than khc nhau. Theo mt s nghin cu nc ngoi, cc nguyn t dinh dng

c trong TSH c th khng c hiu lc ngay i vi cy trng bi v a s chng trng thi

kh tiu.

i vi hm lng nit cc phng php to TSH t tru: PP1, PP2 v PP3 cho

thy, hm lng nit c trong PP3 l cao nht, tip n l PP1 v thp nht l PP2, vi cc gi

tr tng ng l 0,07%, 0,05% v 0,02%. Vi cc phng php to TSH t rm r: PP 4, PP5,

PP6, PP7 cho thy, hm lng nit c trong PP7 l cao nht, tip n l PP6, PP5 v thp

nht l PP4 vi gi tr tng ng l 0,24%, 0,19%, 0,17%, 0,16%.

Vi hm lng P2O5 c trong TSH cho thy, vi PP3 c hm lng cao nht v thp

nhp l PP1. Vi hm lng tng ng theo th t gim dn l: PP3>PP4>PP6> PP7>

PP5>PP2> PP1.

Kali l nguyn t tro, thng th n khng b mt i sau qu trnh t chy. Theo kt

qu phn tch TSH cho thy, hm lng kali c trong TSH lm t tru c xp theo th t

PP3>PP2>PP1. Hm lng kali c trong TSH lm t rm cng c sp xp theo th t nh

sau PP7>PP6>PP5> PP4.

Nu quan st k ta thy hm lng m v Kali hu nh gn lin vi hm lng TC

trong c 2 loi vt liu rm v tru, ngha l khi TC cao thi N v K cng tng.

4. Kt lun

T nhng nghin cu th nghim cc phng php sn xut TSH khc nhau cho kt

lun nh sau:

- Hm lng cacbon tng s, cacbon hu c v kali trong rm cao hn hm lng c

trong tru. Ngc li hm lng nit v P2O5 trong rm thp hn so vi tru.

- Than sinh hc lm t tru theo phng php t gin tip (PP3) cho hm lng

cacbon tng s, cacbon hu c, nit v P2O5 cao hn cc phng php t trc tip (PP1 v

PP2).

- Than sinh hc lm t rm r theo phng php t gin tip (PP7) cng cho hm

lng cacbon tng s, cacbon hu c, nit v K2O cao hn cc phng php trc tip (PP4,

PP5 v PP6).

- Hiu sut thu hi cc bon t rm r thp hn t tru. PP3 i vi vt liu t tru v

PP7 i vi vt liu t rm r cho hiu sut thu hi cc bon l cao nht.

TI LIU THAM KHO

1. GSO, 2009. Trung tm d liu thng k,Tng cc thng k Vit Nam.

2. IPCC. 2007. Climate Change 2007: The Physical Science Basis. Contribution of

Working Group I to the Fourth Assessment Report, eds., Solomon S, Qin D, Manning M,

Chen Z, Marquis M, Averyt K-B, Tignor M, Miller H-L (Cambridge Univ. Press, Cambridge,

UK and New York, NY, USA).

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