January 13th, 2023
India-Japan EW:

Negative emission technology forcarbon dioxide in agricultural fields

Institute for Agro-Environmental Sciences, NARO

ンによる収穫作業がやりにくくなるので、収穫までの水田の水はけを良くす要である。
Typical rice paddy water management in JapanA
田植
期

溝切り

B

C

中
干
し

飽水管理

Water level

DE

常時湛水管理幼形期

Panicleinitiation

(３週間)
５月

６月

７月

出穂 Heading
期(25日間)
８月

落水
収穫
期

Harvesting

９月

A. Transplanting
B. Mid-season drainage(MD)水管理のイメージ（カドミウムの玄米含有濃度が0.2ppm以上検出される可能性のある地区
C.
Saturated water management
D. Flooded) 用水管理対策E. Final drainage

梅雨明けから登熟期にかけては、高温少雨により用水不足となる場合もので、効率的な水利用ができるように用水管理の徹底を図る。

Mechanisms of CH4 emission from rice paddy field

Paddy field

Upland（drained）
Poor CH4Rich CH4O2waterPaddy soil

Organic matters

CH4richpoor

酸化状態
Oxydized

CH4
還元状態
ReducedCO2, CH3COOH

methanogenmethanogen⚫ CH4 in paddy soil is emanated by the activities of anaerobic bacteria which iscalled methanogen. CH4 is produced by reduction of CO2 or decomposition ofacetic acid
⚫ It is effective to control methane emission from rice paddy that period is
prolonged on intermittent irrigation drainage, composted rice straw isincorporated as fertilizer instead of flesh one, or other.

Reduction of CH4 emission by prolonged MD (mid-season-drainage)
period; Fukushima Prefectural Agricultural Center in 2004.
⚫CH4 emission in paddy field is able to reduce prolonged‘Nakaboshi’ treatments.

Flooding period
CH4 flux （mg m-2 hr-1）

40
NAkaboshi

panicle initiation stage

Continuous flooding
MD 2 weeks
MD 3 weeks
MD 4 weeks

30
20
10

Yield of rice is strongly damaged bydrainage after panicle initiation stage ofrice with cadmium accumulation risk.

0MayJuneJuly

AugustSeptemberTechnologies for reducing greenhouse gases emitted
from farmland
Methane (CH4) emissions can be reduced by approximately 30% by extending the mid-season
drainage period of paddy fields by one week compared to conventional water management.

Average amount of methane generated in conventional paddy fields = 200 kg ha-1
(CO2equivalent to 5.0 t/ha)
Methane reduction effect by midseason drainage water management＝2.0 t/ha
Equivalent to CO2 emissions from one car for one year

Direct payment subsidy forenvironment-conserving
agriculture(Ministry of Agriculture, Forestryand Fishery, Japan)

Subsidy conditions:
Mitigation of methane emissions from paddy fields by prolonging midseason drainage,Masayuki Itoh, Shigeto Sudo, Shizuka Mori, Hiroshi Saito, Takahiro Yoshida, Yutaka Shiratori,Shinobu Suga, Nanako Yoshikawa, Yasufumi Suzue, Hiroyuki Mizukami, Toshiyuki Mochida,Kazuyuki Yagi, AGRICULTURE ECOSYSTEMS & ENVIRONMENT 141(3-4) 359-372( 2011)(1)The main crop is paddy rice.
(2)At least one ditch per 0.1 hectare should be cut
during the middle stage of rice growth, followedby mid-drying for at least 14 days.

Sequestration of carbon by biochar
Biochar is one of charcoal. Its origin is biomass. Biochar is
produced by low temperature(<300 ºC) combustion of biomass
under insufficient oxygen supply.
Lehmann J. & Joseph S. (2015)

analysisstandard
JIS8812BiocharN, O, H
NonPyCsolidcarbon
PyC

Ash(including
inorganic
C, H, O)solid carbon
80%
灰分
揮発分10%
10%

Biochar as carbon sequestration technology
Copyright 2022 NARO

○Biochar remains in the soil as persistent carbon for a long period of time (in units of100 years)〇 Domestic CO2 absorption potential of biochar is about 14 million t/yr in Japan
which is equivalent to about 40% of total GHG emissions in the agricultural sector

Estimation of annual CO2 sequestraton by applying biochar to farmland
Available
biomass（Gg）

carboncontent（％）

charcarbonratio

Carbon residual
ratio after 100yrs

CO2sequest
ration
（Gg）

wood

7500

400.770.897630

bamboo2560

27

rice straw

7510

50

0.490.65

4390

rice husk

2000500.49

0.65

11700

0.439

1130

total

14,320CO2Sequestration＝available biomass×carbon content×char carbon ratio×carbon residual ratio• Total CO2 emission in Japan（２０２０）＝1,150,000GgCO2/yr• GHG emission in agriculture（２０２０）＝ 30,000GgCO2/yr （including CH4＋N2O)

66

【GHG emission and sequestration in orchard】

photosynthesis

GHG input and output in orchard

光合成【GHG balance】
CH4 absorption
N2O emission (1% of applicated N fertilizer)
CO2 reduction by biochar application

ghg balanceCO2pearCO2
decomposition of有機物分解
organic matters

N2O
methaneoxidation
メタン酸化菌nitrification

硝化・脱窒& denitrification

N2O emission

grape
peachorange

carbonsequestration

CH4

Orchard field Biochar applicated orchard field canbe carbon negative field.

rice stock warehouse in Japan

revolver type combustor

In Japan, rice husk is removed by machinery in warehouse. In some warehouse, rice husk
is transported to revolver type combustor to make rice husk biochar.

biochar produce by rice crop residue

Yammer Company, Japan of agriculture machinery is now establishing bio-gas power
generating system. This picture shows small scale test plant in Japan and Myanmar. The
combustion source is rice husk and rice straw. By using this system, people remove rice
crop residues to make electricity. The remaining residue after burning will be used as soil
amendment.

Biochar involving rural carbon negative cycles

power gen. &carbonization

Eco Branding crops
harvestbiocharproduction instock yard

agro-waste

power generation &biochar

crops, fruits, vege

biochar blended
manure-chemical
mixture fertilizer

livestockammonia・CCS (J-Credit)
・N2O reductionmeategg

rural
ペレット化
transportati
onapplication of pelletized manure

reduction ofodder by biocharpelletized manure