Feasibility  of  Rice  Straw  Utilization  for  Small  Scale  Power  Production  

 

 

 

 

 

 

Dan  Hoer  

Brock  Phillips  

Angela  Wang  

Ruby  Woodside

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Acknowledgements  

This  study  was  conducted  at  the  Joint  Graduate  School  of  Energy  and  the  Environment  (JGSEE),  King  Mongkut’s  University  of  Technology  Thonburi  (KMUTT).  

Advisors:  

  Savitri  Garivait  (JGSEE-‐KMUTT)  

Rich  Kamens  (UNC-‐CH)  

Special  Thanks  to:  

Penwadee  Cheewaphongphan  (JGSEE-‐KMUTT)  

Ubonwan  Chaiyo  (JGSEE-‐KMUTT)  

Kanittha  Kanokkanjana  (JGSEE-‐KMUTT)  

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Table  of  Contents  

Abbreviations  .........................................................................................................................  6  Abstract  ..................................................................................................................................  8  Executive  Summary  .................................................................................................................  8  1.Introduction  to  Rice  Agriculture    ........................................................................................  11  1.1.Rice  Agriculture  in  Thailand  .............................................................................................  13  

1.1.1.Different  Regions  in  Thailand  ...................................................................................  14  1.1.1.1.Northeast  Thailand  ................................................................................................  14  1.1.1.2.Central  Thailand  ....................................................................................................  15  1.1.1.3.Northern  Thailand  .................................................................................................  15  1.1.1.4.Southern  Thailand  .................................................................................................  15  1.1.2Increasing  Rice  Production  in  Thailand  ......................................................................  15  1.1.2.1.Irrigation  ...............................................................................................................  16  1.1.2.2.Use  of  Fertilizers    ...................................................................................................  17  1.1.2.3.Other    ....................................................................................................................  17  

1.2.Rice  Cultivation  ...............................................................................................................  18  1.2.1.Classification  of  Cultivation  Methods  .......................................................................  18  1.2.2.General  Cultivation  Practices  ....................................................................................  19  1.2.2.1.Pregermination  .....................................................................................................  19  1.2.2.2.Stand  Establishment  ..............................................................................................  19  

1.2.2.2.1.Transplanting  ...............................................................................................  19  1.2.2.2.2.Seedling  Raising  ............................................................................................  19  1.2.2.2.3.Seedling  Handling  .........................................................................................  20  

1.2.2.3.Planting  .................................................................................................................  20  1.2.2.4.Direct-‐Seeded  (Puddled)  ........................................................................................  21  1.2.2.5.Direct-‐Seeded  (Dry)  ...............................................................................................  21  1.2.2.6.Broadcast  in  Water  ................................................................................................  21  1.2.2.7.Crop  Maintenance  .................................................................................................  22  1.2.2.8.Harvesting  .............................................................................................................  22  1.2.3.Growing  Environments  .............................................................................................  22  1.2.3.1.Upland  ..................................................................................................................  23  1.2.3.2.Irrigated  Lowland  ..................................................................................................  23  1.2.3.3.Rainfed  Lowland  ....................................................................................................  24  1.2.3.4.Deepwater  ............................................................................................................  24  1.2.3.5.Floating  .................................................................................................................  25  

1.3.International  Data  ...........................................................................................................  25  1.3.1.Asia  ..........................................................................................................................  25  1.3.1.1Thailand  .................................................................................................................  25  

1.4.By-‐products  and  Residues  from  Rice  Cultivation  ..............................................................  26  2.Straw  Availability  in  Thailand  .............................................................................................  27  2.1.Pollution  Control  Department  Data  .................................................................................  27  

2.1.1.Thailand  Residue  Burn  Data  .....................................................................................  30  2.2.Rice  Straw  Availability  in  Thailand  ...................................................................................  34  

2.2.1.Area  .........................................................................................................................  34  2.2.2.Straw  to  Grain  Ratio  (SGR)  and  Harvest  Index  (HI)  ....................................................  34  2.2.3.Methodology  ............................................................................................................  35  2.2.3.1.Rice  Production  Statistics  ......................................................................................  35  2.2.3.2.Varietals  ................................................................................................................  35  2.2.3.3.SGR  Differences  .....................................................................................................  36  2.2.3.4.Regional  Differences  ..............................................................................................  37  

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2.2.3.5.PCD  Data  ...............................................................................................................  38  2.2.3.6.Rice  Straw  Availability  ...........................................................................................  39  2.2.4.Results  .....................................................................................................................  40  2.2.4.1.Rice  Straw  Produced  ..............................................................................................  40  

2.2.4.1.1.Total  .............................................................................................................  40  2.2.4.1.2.Major  and  Second  Rice  .................................................................................  42  

2.2.4.2.Rice  Straw  Burned.  ................................................................................................  43  2.2.4.2.1.Total  .............................................................................................................  43  2.2.4.2.2.Major  and  Second  Rice  .................................................................................  44  

3.Rice  Straw  Utilization  .........................................................................................................  45  3.1.Current  Management  Practices  .......................................................................................  45  

3.1.1.Burning  ....................................................................................................................  45  3.2.Utilization  .......................................................................................................................  46  

3.2.1.Offsite  ......................................................................................................................  46  3.2.2.Onsite  ......................................................................................................................  47  

3.3.Rice  Straw  Utilization  in  Thailand  ....................................................................................  47  4.Assessment  of  Technologies  for  Heat  and  Power  Production  .............................................  48  4.1.Combustion  ....................................................................................................................  48  

4.1.1.Stages  of  Biomass  Combustion  .................................................................................  49  4.1.2.Key  Issues  .................................................................................................................  49  4.1.2.1.Moisture  Content  of  Fuel  .......................................................................................  49  4.1.2.2.NOx  Emissions  .......................................................................................................  50  4.1.2.3Ash  Problems  .........................................................................................................  50  4.1.3.Power  Generation  ....................................................................................................  51  4.1.4.Rice  Straw  as  a  Fuel  Source  ......................................................................................  51  4.1.5.Technologies  ............................................................................................................  52  4.1.5.1.Pile  Burner  ............................................................................................................  52  4.1.5.2.Stoker  Fired  Boiler  .................................................................................................  52  

4.1.5.2.1.Sloping  Grate  ................................................................................................  53  4.1.5.2.2.Travelling  Grate  ............................................................................................  53  4.1.5.2.3.Vibrating  Grate  .............................................................................................  53  

4.1.5.3.Suspension  Fired  Boiler  .........................................................................................  53  4.1.5.4Fluidized  Bed  Boiler  ................................................................................................  54  

4.1.5.4.1.Bubbling  Fluidized  Bed  (BFB)  ........................................................................  55  4.1.5.4.2.Circulating  Fluidized  Bed  (CFB)  .....................................................................  55  

4.1.6.Suggestions  ..............................................................................................................  55  4.2.Gasification  .....................................................................................................................  56  4.3.Pyrolysis  ..........................................................................................................................  57  

4.3.1.Fast  (flash)  pyrolysis    ................................................................................................  57  4.3.2.Slow  (vacuum)  pyrolysis  ...........................................................................................  58  4.3.3.Pyrolytic  Bio-‐oils  .......................................................................................................  58  4.3.3.1.Kinematic  Viscosity  ................................................................................................  58  4.3.3.2.Density  ..................................................................................................................  58  4.3.3.3.Ash  Content  ...........................................................................................................  58  4.3.3.4.pH  Level  ................................................................................................................  59  4.3.3.5.Flash  Point  .............................................................................................................  59  4.3.3.6.Pour  Point  .............................................................................................................  59  4.3.3.7.Gross  Calorific  Value  ..............................................................................................  59  4.3.4.Costs  ........................................................................................................................  59  

4.4.Biomethanation  ..............................................................................................................  60  4.4.1.Requirements  for  the  Technology  .............................................................................  61  

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4.4.2.Material  Properties  ..................................................................................................  62  4.4.3.Current  Experience  ...................................................................................................  62  4.4.4.Applicability  to  Thailand  ...........................................................................................  63  4.4.5.Recommendations  ...................................................................................................  63  

4.5.Hydrolysis  .......................................................................................................................  64  4.6.Summary  of  Technologies  ...............................................................................................  65  5.Chemical  Analysis  of  Rice  Straw  .........................................................................................  65  5.1.Background  .....................................................................................................................  65  5.2.Methodology  ..................................................................................................................  69  5.3.Ultimate  Analysis  ............................................................................................................  70  5.4.Proximate  Analysis  ..........................................................................................................  72  5.5.Calorific  Values  ...............................................................................................................  76  6.Feasibility  of  Utilizing  Rice  Straw  for  Power  Production  .....................................................  78  6.1.Collection  Processes  ........................................................................................................  78  6.2.Harvest  Processes  ...........................................................................................................  78  6.3.Processing  Activities:  Raking  and  Swathing  .....................................................................  79  6.4.Processing  Activities:  Densification  and  Road-‐Siding  .......................................................  80  6.5.Transportation  ................................................................................................................  82  6.6.Storage  Considerations  ...................................................................................................  83  6.7.Energetic  Feasibility  Analysis  ...........................................................................................  84  

6.7.1.Energetic  Feasibility  Analysis  Results  ........................................................................  85  6.8.Economic  Feasibility  Analysis  ..........................................................................................  86  

6.8.1.Economic  Feasibility  Analysis  Results  .......................................................................  86  6.9.Economic  Assessment  Based  on  End  User  .......................................................................  87  6.10.Economics  of  On-‐Site  Utilization  ....................................................................................  89  6.11.Conclusions  ...................................................................................................................  90  7.  Recommendations  ............................................................................................................  90  8.Conclusions  ........................................................................................................................  93  Appendix  A  ...........................................................................................................................  95  Appendix  B  ...........................................................................................................................  98  Appendix  C  .........................................................................................................................  103  Appendix  D  .........................................................................................................................  108  Appendix  E  ..........................................................................................................................  112  Appendix  F  ..........................................................................................................................  117  Appendex  G  ........................................................................................................................  119  Works  Cited  ........................................................................................................................  121  

 

 

 

 

 

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Abbreviations  

BC-‐Black  Carbon  

BFB-‐Bubbling  Fluidized  Bed  

C-‐Carbon  

Cd-‐Cadmium  

CFB-‐Circulating  Fluidized  Bed  

CH4-‐Methane  

CO-‐Carbon  Monoxide  

CO2-‐Carbon  Dioxide  

Cr-‐Chromium  

FAO-‐Food  and  Agriculture  Organization  

GSR-‐Grain  to  Straw  Ratio  

H-‐Hydrogen  

HHV-‐Higher  Heating  Value  

HI-‐Harvest  Index  

IRRI-‐International  Rice  Research  Institute  

K-‐Potassium  

LHV-‐Lower  Heating  Value  

N-‐Nitrogen  

NH3-‐Ammonia  

Ni-‐Nickel  

N2O-‐Nitrous  Oxide  

NOx-‐Nitrogen  Oxides  

O-‐Oxygen  

OC-‐Organic  Compounds  

P-‐Phosphorous  

PCD-‐Pollution  Control  Department  

Pb-‐Lead  

S-‐Sulfur  

SCG-‐Siam  Cement  Group  

Se-‐Selenium  

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SGR-‐Straw  to  Grain  Ratio  

SO2-‐Sulfur  Dioxide  

SOx-‐Sulfur  Oxides  

USD-‐U.S.  Dollar  

THB-‐Thai  Baht  

V-‐Vanadium  

VOC-‐Volatile  Organic  Compounds  

Zn-‐Zinc  

 

 

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Abstract  

As  the  total  yearly  production  of  rice  in  Thailand  increases,  Thais  must  find  ways  to  manage  

the  increasing  amounts  of  rice  straw  produced  as  a  byproduct.    One  of  the  current  methods  of  

management  is  open  burning,  and  in  2006  approximately  4.32  Mt  of  rice  straw  was  burned  in  

Thailand.    However,  in  recent  years  Thais  have  begun  to  search  for  alternative  methods  of  rice  straw  

management,  including  utilization  of  the  biomass  to  produce  energy.    This  study  focuses  on  the  

feasibility  of  using  rice  straw  for  such  purposes.    It  was  found  that  rice  straw  has  an  average  calorific  

value  of  3,308.29    cal/g.    However,  due  to  physical  and  chemical  properties  of  rice  straw,  the  

biomass  is  not  suited  for  most  large  scale  conversion  technologies.      The  most  feasible  option  for  

energy  conversion  is  co-‐firing  combustion  with  coal.    Analysis  show  that  while  off  site  utilization  of  

rice  straw  is  energetically  feasible,  the  main  barriers  are  currently  economics  related.      

 

Executive  Summary  

In  order  to  provide  the  overall  rice  straw  use  feasibility  analysis  presented  in  this  paper,  an  

extensive  literature  review  regarding  practices  of  rice  cultivation  and  harvest  in  Thailand,  rice  straw  

utilization  schemes,  and  possible  applicable  technologies  was  conducted.    The  goal  of  this  project  

was  to  compile  useful  information  into  a  single  location,  and  to  draw  from  existing  data  the  most  

viable  plan  of  action  for  the  future.  To  supplement  the  literature  review,  site  visits  were  conducted  

both  to  rice  plantations  where  straw  samples  were  taken  and  farmers  interviewed,  as  well  as  to  a  

major  Thai  cement  company  representing  a  possible  end  user  of  rice  straw.    The  data  gathered  from  

the  farmer  interviews  was  used  in  combination  with  data  from  the  Pollution  Control  Department  

(PCD)  to  analyze  current  patterns  of  rice  cultivation  and  straw  management  in  Thailand.    The  

samples  of  rice  straw  were  analyzed  for  composition  and  compared  to  data  found  in  the  literature.  

Finally,  using  data  from  the  field  visits  as  well  as  data  found  in  the  literature,  energetic  and  economic  

feasibility  analyses  were  preformed  regarding  the  use  of  rice  straw  for  energy  purposes.    Some  of  

the  key  findings  are  outlined  below.  

To  determine  the  amount  of  rice  straw  available  for  energy  utilization  in  Thailand,  the  total  

amounts  of  rice  straw  produced  were  determined  for  each  province.    This  was  done  using  straw  to  

grain  ratio  (SGR)  values  found  in  the  literature  and  recorded  values  of  each  province’s  rice  

production.    The  amount  of  this  rice  straw  available  for  energy  purposes  was  assumed  to  be  the  

amount  otherwise  burned  by  farmers.    The  fraction  of  rice  straw  burned  in  each  province  was  taken  

9    

from  the  PCD  data.    The  following  graph  shows  the  yearly  regional  results  for  the  total  rice  straw  

burned:  

 

Figure  2.13.  Total  rice  straw  burned,  in  tons,  by  region  in  Thailand.  

  Based  on  the  technology  review,  the  most  promising  methods  of  energy  conversion  utilizing  

rice  straw  are  combustion,  particularly  co-‐firing,  and  biomethanation.    For  the  large  scale  production  

of  heat  and  energy,  combustion  of  rice  straw  using  a  fluidized  bed  boiler  is  the  most  feasible.    To  

overcome  the  difficulties  of  maintaining  a  large  continuous  source  of  rice  straw,  as  well  as  

minimizing  some  of  the  problematic  qualities  of  straw  as  a  primary  fuel  source,  co-‐firing  with  coal  is  

ideal.    This  can  be  done  in  existing  fluidized  bed  boilers  with  minimal  adjustments.  Biomethanation  

would  be  most  applicable  for  small  scale,  on  site  usage  as  a  provider  of  fuel  for  cooking  or  lighting  

purposes.    This  technology  lends  itself  well  to  many  regions  of  Thailand,  particularly  the  Northeast,  

where  the  farms  are  decentralized  and  there  is  a  lack  of  suitable  highways,  making  transporting  rice  

straw  to  a  centralized  location  difficult.      

  The  energetic  feasibility  analysis  of  rice  straw  utilization  determined  that  energy  can  be  

recovered  at  all  transportation  distances  between  5  and  1500  kilometers  with  recovery  efficiencies  

varied  from  5  to  100  percent  of  the  higher  heating  value  of  rice  straw  (HHV).      However,  the  

economic  feasibility  analysis  showed  that  rice  straw  collection  and  utilization  is  not  beneficial  at  

significant  distances,  depending  on  parameters  such  as  the  market  price  of  rice  straw  and  

government  subsidies.    In  many  situations,  the  utilization  of  rice  straw  is  not  feasible  at  any  

transportation  distance.    While  these  two  analyses  make  many  assumptions  which  may  not  be  

accurate  for  Thailand  and  are  very  sensitive  to  market  fluctuations,  they  do  show  that  the  primary  

obstacle  in  rice  straw  utilization  is  economics  related.    

10    

Based  on  these  analyses  and  the  data  compiled  from  the  literature  and  field  visits,  

recommendations  were  made  for  future  research  and  action  to  be  taken  regarding  the  use  of  rice  

straw  for  energy  purposes.    It  was  found  that  on  a  large,  country  wide  scale,  rice  straw  for  power  

production  is  simply  not  feasible.    In  some  provinces  where  larger  farms  are  situated  in  close  

proximity  to  one  another  and  the  rice  straw  is  thus  more  centralized,  it  may  be  feasible  to  collect  

and  transport  rice  straw  to  a  common  site  for  energy  production.    However,  the  collection  method  

and  transportation  scheme  need  to  be  analyzed  carefully  depending  on  the  specific  situation.    It  is  

not  viable  at  all  to  have  collection  schemes  in  regions  where  the  rice  straw  is  decentralized  and  

located  at  smaller  farms.    In  these  cases  further  research  into  on  site  utilization  schemes  other  than  

burning  is  recommended.    Biomethanation  has  strong  potential  for  these  cases.    Finally,  it  is  also  

recommended  that  more  spatially  resolute  data  regarding  the  rice  cultivation  in  Thailand  be  

collected.    In  this  way  it  could  be  seen  exactly  where  rice  straw  is  located,  and  thus  exactly  which  

regions  have  the  potential  for  collection  schemes.      

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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1. Introduction  to  Rice  Agriculture    

This  report  will  focus  on  rice  straw  and  its  current  disposal  as  well  as  possible  energy  

utilizations,  specifically  in  Thailand.    Currently,  the  main  method  for  removal  of  rice  straw  is  through  

burning  because  it  is  the  most  convenient  and  least  labor  intensive  way.    Also,  there  are  no  existing  

incentives  for  the  farmers  not  to  burn.  The  different  technologies  available  to  convert  rice  straw  into  

an  energy  source  are  still  relatively  new  and  still  under  development,  but  they  have  the  potential  to  

benefit  farmers  on  a  local  scale  by  allowing  them  to  harness  the  energy  in  rice  straw  towards  other  

activities.    This  study  will  first  look  at  rice  agriculture  in  Thailand  and  investigate  the  availability  of  

rice  straw  in  Thailand  based  on  government  data  on  rice  production  and  literature  values  for  straw  

to  grain  ratios.    Next,  current  management  practices,  energy  potential  of  collected  sample  rice  straw  

from  laboratory  experiments,  and  potential  technologies  that  use  rice  straw  for  heat  and  power  

production  are  considered.    Lastly,  the  energetic  and  economic  feasibility  of  utilizing  rice  straw  for  

power  production  is  examined  considering  collection,  transport,  and  storage  of  rice  straw.  

In  order  to  examine  the  availability  of  rice  straw,  it  is  important  to  first  get  some  background  

about  rice  production  worldwide  and  Thailand.    In  2007,  the  world  produced  about  645  million  

tonnes  of  rice.    Not  surprisingly,  Asia  is  the  leader  in  rice  production,  generating  about  575  million  

tonnes  of  rice  in  2007,  as  can  be  seen  below.  (IRRI  2007).  

 

Figure  1.1.  Rough  rice  production  worldwide,  1961-‐2007.  (IRRI  2007).  

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  The  harvested  area  of  rice  has  followed  a  similar  upward  trend  but  with  less  of  a  steep  

increase,  while  the  yield  of  rough  rice  has  improved  drastically  in  the  recent  decades.  

 

Figure  1.2.  Harvested  area  of  rough  rice  worldwide,  1961-‐2007.  (IRRI  2007).  

 

Figure  1.3.  Rough  rice  yield  worldwide,  1961-‐2007.  (IRRI  2007).  

The  rapid  growth  of  rice  production  and  yield  without  a  significant  expansion  in  harvested  area  is  

due  to  different  management  techniques,  new  technology  (e.g.  combine  harvesters),  fertilizers,  

higher  yielding  varieties  of  rice,  and  more.      To  complement  background  information  about  rice  

agriculture  in  Thailand,  the  top  five  rice  producing  nations-‐  China,  India,  Indonesia,  Bangladesh,  and  

Vietnam-‐  are  examined  as  well.  

13    

 Production  

(tonnes)  

Export  

(tonnes)  Rice  area  (ha)  

Yield  

(tonne/ha)  

World   636,493,000   29,066,000   154,436,000   4.12  

China   186,454,000   1,000,000   29,865,000   6.24  

India   143,534,000   2,800,000   44,000,000   3.26  

Indonesia   55,039,000   -‐   11,900,000   4.63  

Bangladesh   42,904,000   -‐   11,100,000   3.87  

Vietnam   35,671,000   4,750,000   7,342,000   4.86  

Thailand   28,030,000   10,000,000   10,430,000   2.69  

Table  1.1.  2007  World  Rice  Statistics  (IRRI  2007).  

  The  largest  producer  of  rice  is  China,  producing  186,454,000  tonnes  of  rice  in  2007.  

However,  the  largest  exporter  of  rice  is  Thailand,  exporting  nearly  a  third  of  their  production  and  

total  world  exports.    Indonesia  and  Bangladesh  have  subsistence-‐based  rice  agricultures  and  

therefore,  do  not  contribute  to  the  world  export  of  rice.    India,  second  largest  in  production,  has  the  

most  area  devoted  to  rice  cultivation.    The  average  yield  of  6.24  t/ha  in  China  is  well  above  the  world  

average  yield  of  4.12  t/ha  while  Thailand  has  the  lowest  yield  of  only  2.69  t/ha.  (IRRI  2007).  

1.1. Rice  Agriculture  in  Thailand    

In  order  to  determine  the  availability  of  rice  straw  in  Thailand,  one  must  first  understand  rice  

agriculture  and  its  trends  over  recent  years.    Rice  is  the  staple  food  for  all  of  Thailand  and  the  main  

agricultural  product  in  Thailand.    Also,  Thailand  has  become  the  top  exporter  of  rice  in  recent  years.    

About  40%  of  land  in  Thailand  is  devoted  to  agriculture,  of  which  about  50%  is  used  for  rice  

cultivation.  (OAE  2001).  

 

Figure  1.4.  Land  use  in  Thailand.  (OAE  2001).  

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1.1.1. Different  Regions  in  Thailand  

There  are  four  regions  Thailand  can  be  divided  into-‐  the  northeast,  central,  north,  and  south.    These  

regions  are  distinct  in  their  environments  and  characteristics  pertaining  to  rice  productivity.    

Figure1.5.  Regions  of  Thailand  and  land  use.  (OAE  2001).  

1.1.1.1. Northeast  Thailand  

The  northeast  holds  more  than  half  of  the  rice  land  in  Thailand  although  the  average  size  of  its  farms  

is  smaller  than  other  regions.    Problems  in  this  area  include  soil  erosion  and  drought  during  the  dry  

season,  so  less  than  10%  of  the  land  here  is  planted  with  rice  during  the  dry  season.    Also,  the  

northeast  has  poor  water-‐holding  capacity  soils  which  further  worsens  soil  conditions  since  less  than  

20%  of  total  irrigated  land  in  Thailand  is  in  this  region.  

 

 

15    

 

1.1.1.2. Central  Thailand  

About  20%  of  total  cultivated  rice  land  is  in  the  central  region  of  Thailand.    The  central  area  has  large  

average  farm  sizes  and  farmers  have  more  access  to  irrigation  resources  so  about  75%  of  dry  season  

rice  is  grown  using  irrigation.    Also,  production  is  high  due  to  the  mechanization  of  almost  all  

operations  and  the  use  of  less  labor  intensive  practices  like  direct  seeding.  

1.1.1.3. Northern  Thailand  

The  northern  region  of  Thailand  accounts  for  about  one-‐third  of  the  land  area  in  Thailand  and  also  

has  opposite  kinds  of  topography.    Therefore,  there  are  two  kinds  of  rice  grown  here-‐  upland  rice,  

grown  in  high  hills  and  in  upland  areas,  and  lowland  rice,  grown  in  valleys  and  terraced  paddies.    This  

region  contains  about  20%  of  total  rice  land  in  Thailand.  

1.1.1.4. Southern  Thailand  

The  southern  region  of  Thailand  only  comprises  about  14%  of  the  total  land  area  in  Thailand.    Not  

surprisingly,  this  region  accounts  for  just  6%  of  the  total  rice  land  in  Thailand.    Also,  rice  productivity  

is  low  since  there  are  limited  rice  fields  and  the  soil  in  this  region  is  acidic.  (IRRI  2007).  

1.1.2. Increasing  Rice  Production  in  Thailand  

Thailand  has  become  the  major  exporter;  in  2007,  Thailand  produced  about  28  million  tonnes  of  rice  

and  exported  almost  10  million  tonnes  of  rice.    (IRRI  2007).  

 

Figure  1.6.  Rice  production  in  Thailand,  1994-‐2003.  (OAE  2003).  

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This  may  seem  strange  since  Thailand  is  not  in  the  top  three  rice-‐producing  countries  but  there  are  

several  explanations  for  this-‐  increasing  access  to  irrigation  systems,  use  of  fertilizers  and  pesticides,  

mechanization  of  labor,  and  weather.    These  reasons  are  also  responsible  for  explaining  why  

harvested  area  has  remained  fairly  constant  while  yield  has  increased,  shown  in  the  next  two  figures.  

 

Figure  1.7.  Harvested  area  in  Thailand,  1994-‐2003.  (OAE  2003).  

 

Figure  1.8.  Rice  yield  in  Thailand,  1994-‐2003.  (OAE  2003).  

1.1.2.1. Irrigation  

The  irrigated  areas  in  Thailand  have  been  slowly  but  steadily  increasing.    The  biggest  increase  in  

irrigated  areas  is  in  the  North,  increasing  on  average  about  180,000  rai  a  year,  while  the  other  

regions  are  increasing  at  about  88,000  rai  a  year.  

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Figure  1.9.  Irrigated  area  in  Thailand,  1003-‐2003.  (OAE  2003)  

1.1.2.2. Use  of  Fertilizers    

The  use  of  fertilizers  has  also  increased  progressively  in  the  last  couple  decades,  which  is  also  a  

major  reason  production  and  yield  have  increased.  

 

Figure  1.10.  Fertilizer  consumption  in  Thailand,  1961-‐2002.  (IRRI  2002)  

1.1.2.3. Other    

Manual  labor  is  being  replaced  by  machines  that  can  do  the  same  amount  of  work  in  less  time  and  

can  help  the  farmer  save  money  on  labor  costs.    Also,  higher  yielding  varieties  of  rice  are  now  being  

used,  which  has  improved  yield  and  production  of  rice.  

 

18    

1.2. Rice  Cultivation  

As  a  crop,  rice  is  incredibly  versatile  given  its  ability  to  be  grown  in  latitudes  ranging  from  30°  S  to  

50°  N,  altitudes  from  sea  level  to  2500m,  soils  with  a  pH  of  3  to  10,  and  varying  amounts  of  organic  

matter  and  salinity.    Cultivated  for  centuries,  the  numbers  of  rice  varietals  and  potential  growing  

environments  have  grown  in  such  a  way  that  there  are  numerous  means  of  classifying  rice  

cultivation.    The  simplest  means  of  classification  is  as  either  lowland  (wetland)  or  upland  (dryland),  

with  rice  originally  being  a  lowland  crop.    Lowland  rice  is  less  dependent  upon  the  physical  

properties  of  the  soil  due  to  the  presence  of  large  amounts  of  water  used  during  the  growing  

season.    Instead  soil  fertility  and  the  chemical  nature  of  the  soil  are  key.    Most  Asian  rice  is  cultivated  

in  a  lowland  setting,  while  rice  cultivated  in  Latin  America  and  Africa  is  done  so  in  an  upland  

environment.  (De  Datta  1981)  

1.2.1. Classification  of  Cultivation  Methods  

The  four  primary  classification  systems  for  rice  cultivation  are  based  upon  one  of  the  following:  the  

water  source,  the  land  and  water  management  system,  the  watering  regime,  or  the  varietal  type.    In  

terms  of  water  source,  rice  can  be  either  rainfed  or  irrigated,  with  rainfed  crops  being  more  

common,  but  higher  yields  obtained  with  irrigated  crops.    Based  upon  the  land  and  water  

management  system,  crops  are  either  lowland  (wetland)  or  upland  (dryland)  preparation.    The  

watering  regime  classification  system  is  based  upon  the  amount  of  standing  water  present  in  the  

fields  during  the  majority  of  the  growing  season.    Upland  rice  cultivation  involves  no  standing  water,  

lowland  rice  cultivation  involves  standing  water  from  a  depth  of  5  cm  to  50  cm,  and  deepwater  rice  

cultivation  involves  standing  water  from  a  depth  of  50  cm  to  600  cm.    The  fourth  major  classification  

system  is  based  upon  the  varietal  type,  with  lowland  rice  crops  being  semidwarf  to  medium  to  tall  in  

height  (100  cm  to  200  cm),  upland  rice  crops  being  medium  to  tall  in  height  (130  cm  to  150  cm),  

deepwater  rice  crops  being  medium  to  tall  in  height  (120  cm  to  150  cm  without  standing  water  and  

200  cm  to  300  cm  with  rising  water  levels),  and  floating  rice  crops  being  tall  in  height  (larger  than  

150  cm  without  standing  water  and  up  to  500  cm  or  600  cm  with  rising  water  levels).  

Classification  of  rice  by  a  single  system  is  rare  since  each  classification  by  itself  is  insufficient  in  fully  

describing  a  particular  rice  crop.    For  example,  lowland  and  deepwater  crops  can  be  further  

categorized  depending  upon  the  stand  establishment  of  the  crop  or  the  method  by  which  the  land  is  

prepared.    Ideally,  a  rice  crop  would  be  classified  by  each  of  these  four  systems  to  provide  the  best  

description  of  the  crop  being  cultivated.    More  holistic,  and  therefore  specific,  systems  of  classifying  

rice  crops  have  been  developed,  including  one  by  Barker  and  Herdt  in  1979.    This  system    is  specific  

19    

to  South  and  Southeast  Asia  and  categorizes  rice  crops  into  one  of  four  categories:    irrigated,  shallow  

rainfed,  deepwater,  and  upland.      

1.2.2. General  Cultivation  Practices  

1.2.2.1. Pregermination  

Pregermination  is  a  process  used  to  prepare  seeds  prior  to  planting  in  order  to  ensure  that  the  crop  

experiences  a  rapid,  even  start,  both  of  which  are  keys  to  a  successful  crop.    A  standard  

pregermination  process  involves  soaking  the  rice  seeds  in  water  for  24  hours  and  then  incubating  

them  for  48  hours.    Following  this  three  day  period,  the  seeds  are  ready  for  planting.  (De  Datta  1981)  

1.2.2.2. Stand  Establishment  

There  are  four  main  methods  of  stand  establishment:  transplanting,  direct-‐seeding  in  puddled  soil,  

direct-‐seeding  in  dry  soil,  and  broadcast  seeding  in  water.  (De  Datta  1981)  

1.2.2.2.1. Transplanting  

In  the  transplanting  method  of  stand  establishment,  seedlings  are  raised  in  smaller  beds  in  one  of  

three  ways  and  then  removed  and  transferred  to  the  main  rice  field.    The  amount  of  time  required  

to  raise  the  seedlings  varies  based  upon  the  method,  which  is  described  in  the  section  discussing  the  

handling  of  seedlings.      Given  improvements  technology,  transplanting  can  be  done  both  manually  

and  mechanically.    (De  Datta  1981)  

1.2.2.2.2. Seedling  Raising  

The  raising  of  seedlings  is  necessary  only  when  transplanting  is  the  method  of  stand  establishment  

employed.    There  are  three  major  methods  of  raising  seedlings:  wet-‐bed,  dry-‐bed,  and  dapog.  The  

selection  of  which  one  is  to  be  used  is  dependent  upon  the  availability  of  water,  yet  each  produce  

similar  yield  rates  in  the  resultant  rice  crop  if  all  other  factors  are  constant.    The  wet-‐bed  method  of  

raising  seedlings  requires  the  broadcast  of  pregerminated  seeds  on  raised,  puddled  soil  at  a  rate  of  

50  kg/ha.        Dry-‐bed  seedling  raising  is  similar  to  the  wet-‐bed  method  in  terms  of  seed  distribution  

method  and  seeding  rate,  however  requires  the  soil  to  be  slightly  moist,  not  puddle.    This  method  is  

more  suitable  for  areas  where  there  is  little  water  for  irrigating  the  seedbeds.      

The  dapog  method  of  raising  seedlings  was  developed  in  the  Philippines  and  is  less  common  than  

the  previous  two  methods.    Pregerminated  seeds  are  broadcast  over  smaller  sections  of  moist  

banana  leafs  or  plastic  sheets  at  a  rate  of  100  kg/ha.    Despite  the  requirement  of  more  seedbed  

preparation,  this  method  is  advantageous  given  the  shorter  period  required  to  grow  the  seedlings,  

20    

the  overall  decrease  in  labor  costs,  and  the  ease  of  transporting  the  seedlings  on  the  leaves  or  sheets  

once  they  are  ready  to  be  transplanted.  (De  Datta  1981)  

1.2.2.2.3. Seedling  Handling  

The  handling  of  seedlings  requires  great  care  given  the  need  for  a  quick  revival  and  rapid  early  

growth  of  the  seedlings  following  transplanting.    Prior  to  transplanting  the  seedbeds  are  flooded  

allowing  for  easier  removal  of  the  seedlings.    In  the  dapog  method,  the  banana  leaves  or  plastic  

sheets  are  simply  cut  into  sections  and  then  used  to  transport  the  seedlings.    Given  the  fact  that  it  is  

harder  for  older  seedlings  to  recover  from  the  transplanting  process  it  is  important  to  transfer  the  

seedlings  at  an  optimal  time.    For  wet-‐bed  and  dry-‐bed  methods  seedlings  are  commonly  

transplanting  after  40  to  50  days  of  growth,  although  20  to  30  days  is  optimal  for  wet-‐bed  raised  

seedlings.    The  dapog  method  fosters  faster  seedling  growth,  allowing  for  them  to  be  transplanted  

after  9  to  14  days  of  growth.    In  terms  of  varietals,  earlier  maturing  rice  should  be  transplanted  

sooner  and  traditional  varieties  are  typically  more  resilient  during  the  transplanting  process  than  

modern  varieties.  (De  Datta  1981)  

1.2.2.3. Planting  

Two  factors  important  to  the  actual  planting  process  are  the  number  of  seedlings  planted  per  hill  

and  the  spacing  of  the  hills  within  the  rice  field.    The  number  of  seedlings  per  hill  is  dependent  upon  

both  the  method  of  raising  the  seedlings  and  the  tillering  capacity  of  the  varietal  being  grown.    

Seedlings  raised  using  the  wet-‐bed  or  dry-‐bed  method  can  be  planted  at  a  density  of  3  to  4  seedlings  

per  hill,  while  a  density  of  6  to  8  seedling  per  hill  is  required  for  seedlings  raised  using  the  dapog  

method.    Varietals  with  higher  tillering  capacities  require  fewer  seedlings  per  hill,  thus  reducing  

labor  and  costs.    For  example,  Chinese  varietals  that  have  lower  tillering  capacities  need  almost  10  

seedlings  per  hill  to  achieve  desired  yields.  

The  amount  of  space  between  adjacent  hills  varies  based  upon  the  varietal  used,  the  seasonal  

conditions,  and  the  fertility  of  the  soil.    Spacing  becomes  increasingly  important  as  the  extremes  are  

reached.      Hills  that  are  planted  too  close  to  one  another  increase  both  the  cost  of  transplanting  and  

the  chance  of  lodging.    A  spacing  that  places  hills  too  far  from  one  another  leads  to  fewer  plants  

being  planted  overall  and  therefore  diminished  yields.  

A  common  practice  in  South  and  Southeast  Asia  is  to  randomly  space  the  hills.    Despite  the  

widespread  use  of  this  method,  especially  in  rainfed  rice  cultivation,  it  makes  the  process  of  weeding  

more  difficult  and  also  complicates  efforts  to  optimize  the  population  of  plants  within  the  field.  (De  

Datta  1981)  

21    

1.2.2.4. Direct-‐Seeded  (Puddled)  

Direct-‐seeding  on  puddled  soil,  also  known  as  wet-‐seeded,  involves  the  broadcasting  or  machine  

drilling  of  pregerminated  seeds  onto  puddled  soil.    Given  the  greater  potential  for  poor  stand  

establishment  that  results  from  this  method,  more  exact  water  management,  better  weed  control,  

and  optimal  fertilizer  management  are  essential.    Additionally,  the  threat  of  lodging  is  more  serious  

with  this  method  of  stand  establishment.    Varietals  with  a  high  tillering  capacity,  good  seedling  vigor,  

and  early  maturation  are  preferred  for  this  method.  (De  Datta  1981)  

1.2.2.5. Direct-‐Seeded  (Dry)  

The  method  of  direct-‐seeding  on  dry  soil  is  the  same  as  the  method  of  direct-‐seeding  on  puddled  soil  

with  the  other  difference  being  the  moisture  content  of  the  soil.    In  the  case  of  rainfed  rice  crops,  

the  execution  of  this  method  is  entirely  dependent  upon  the  pattern  of  local  rainfall.    Ideally,  the  

crop  will  be  planted  just  prior  to  the  onset  of  seasonal  rains,  with  enough  rain  falling  after  planting  

so  that  there  is  good  seedling  emergence  and  quick  vegetative  growth.    These  two  factors  influence  

the  crops  ability  to  withstand  the  two  extremes  of  large  amounts  of  rainfall  and  periods  of  intense  

drought.    Should  the  planting  take  place  after  the  onset  of  seasonal  rains,  there  is  poor  seedling  

emergence  which  results  in  lower  yields.    Much  like  with  direct-‐seeding  in  puddled  soils,  early  

maturing  varietals  are  preferred  as  well  as  varietals  with  good  drought  tolerance.  

A  primary  benefit  of  direct-‐seeding  on  dry  soil,  particularly  with  rainfed  crops,  is  the  potential  for  

doubling  cropping.    The  planting  of  a  secondary  crop  is  characterized  by  turnaround  time,  which  is  

the  interval  between  harvesting  of  the  first  crop  and  planting  of  the  second  crop.    This  period  varies  

from  5  to  37  days,  averaging  21  days,  and  is  dependent  upon  the  planting  method  of  the  second  

crop.    If  the  second  crop  is  wet-‐seeded  compared  to  transplanted,  the  turnaround  time  can  be  

reduced  by  almost  10  days.  (De  Datta  1981)  

1.2.2.6. Broadcast  in  Water  

A  final  method  of  stand  establishment  is  that  of  broadcast  seeding  in  water.    This  method  simply  

requires  the  broadcasting  of  seeds  on  a  field  flooded  to  some  extent  with  water.    Drawbacks  to  this  

method  include  the  use  of  a  greater  amount  of  seeds  to  achieve  similar  yields  and  more  precise  

water  management.    Preferred  varietals  include  those  with  good  seed  viability  and  high  resistance  to  

lodging.  (De  Datta  1981)  

 

 

22    

1.2.2.7. Crop  Maintenance  

Maintenance  of  rice  crops  various  as  much  as  the  cultivation  environments  and  seeding  practices.    

As  with  any  crop,  the  key  forms  of  maintenance  include  supplying  water,  supplying  nutrients,  

controlling  weeds,  and  controlling  pests.    The  first  of  these  depends  upon  the  water  source  and  the  

cultivation  environment.    Application  of  fertilizers,  herbicides,  and  pesticides  have  become  more  

common  to  achieve  the  remaining  three  goals,  yet  simple  solutions  such  as  flooding  to  prevent  

weeds  and  introduction  of  fish  or  ducks  to  reduce  pests  have  proven  to  be  just  as  effective.  

(Greenland  1997)  

1.2.2.8. Harvesting  

The  time  for  harvesting  the  rice  depends  upon  the  percentage  of  ripened  grains  in  panicles,  with  

approximately  80%  of  the  grains  having  a  straw  color.    Also  at  this  stage,  the  lower  part  of  the  

panicle  having  a  hard  dough-‐like  feel.    At  the  time  of  harvest,  the  moisture  content  of  the  rice  is  

typically  greater  than  20%.    Harvesting  of  dry  season  rice  occurs  earlier  than  for  wet  season  rice  

given  the  greater  amount  of  solar  radiation  and  higher  temperatures  achieved  during  the  growing  

season.  

Harvesting  can  be  either  manual  or  mechanical,  both  of  which  are  concerned  with  cutting  the  plant  

in  such  a  way  as  to  minimize  the  amount  of  straw  being  processed  while  harvesting  the  maximum  

amount  of  grain.    Mechanical  harvesting  using  combines  cuts  the  straw  just  below  the  head  at  a  

height  to  minimize  the  amount  of  unharvested  grain  and  the  excessive  shattering  of  harvested  grain.    

The  logistics  of  rice  harvesting  and  its  implications  will  be  discussed  further  in  subsequent  sections.        

(De  Datta  1981)  

1.2.3. Growing  Environments  

Ultimately,  five  general  methods  of  rice  cultivation  emerge  from  the  various  classification  systems,  

which  include  upland,  irrigated  lowland,  rainfed  lowland,  deepwater,  and  floating.    These  methods  

vary  based  not  only  upon  water  level  and  source,  but  stand  establishment  method,  seedling  raising,  

problems  encountered  an  more.    A  general  illustration  of  these  different  methods  is  provided  in  the  

following  diagram.  (De  Datta  1981)  

23    

 

Figure  1.11.  Barker  and  Herdt  rice  cultivation  classification  system.  

1.2.3.1. Upland  

Upland  rice  cultivation  is  unique  in  that  the  rice  crop  is  planted  on  level  or  sloping  fields  with  no  

bunds  to  contain  water.    The  fields  are  prepared  under  dry  conditions  and  the  crop  is  entirely  

dependent  upon  rainfall  for  moisture.    This  method  is  primarily  used  by  subsistence  farmers  in  

poorer  regions  and  due  to  the  growing  environment  there  is  little  mechanization  in  the  cultivation  

process.    Upland  rice  crops  tend  to  have  stable,  lower  yields.  

In  addition  to  the  problems  that  face  lowland  cultivated  rice  crops,  upland  crops  face  greater  weed  

competition,  susceptibility  to  changes  in  the  amount  and  availability  of  rainfall,  incidence  of  blast,  

and  changes  in  soil  nutrients.    This  latter  problem  results  from  the  varying  moisture  availability  

within  aerobic  soils.    The  amount  and  form  of  various  nutrients  necessary  for  successful  plant  

growth,  such  as  potassium  and  iron,  depend  directly  upon  the  moisture  supply  within  the  soil.    Most  

traditional  upland  rice  varietals  are  intermediate  to  tall  in  height,  exhibit  good  drought  tolerance,  

mature  earlier,  develop  deeper  roots,  and  have  lower  tillering  rates.    Problems  associated  with  the  

rice  crop  include  weaker  straw  and  greater  susceptibility  to  lodging.  (De  Datta  1981)  

1.2.3.2. Irrigated  Lowland  

Irrigated  lowland  rice  cultivation  is  a  method  by  which  a  water  level  of  5  cm  to  50  cm  is  maintained  

on  the  rice  field  by  bunds  for  the  majority  of  the  growth  period  and  for  which  the  primary  water  

source  is  irrigation.    The  most  commonly  used  method  of  stand  establishment  is  transplanting,  

however  the  other  three  methods  discussed  previously  are  also  utilized  in  certain  circumstances.    

24    

The  success  of  irrigated  lowland  rice  cultivation  relies  upon  timely  preparation  of  the  land,  careful  

raising  and  handling  of  seedlings,  and  efficient  transplanting.    Compared  to  rainfed  lowland  rice  

cultivation,  this  method  involves  more  efficient  weed  control  and  pesticide  and  fertilizer  application,  

leading  to  higher  yields.  

The  lowland  environment  for  rice  cultivation  is  the  original  growing  environment  for  rice  and  

therefore  problems  encountered  by  and  traits  exhibited  by  varietals  in  this  environment  are  the  

standard  by  which  all  others  are  measured.    Lowland  encompasses  a  wide  variety  of  growing  

conditions  and  therefore  a  large  number  of  varietals  are  grown,  with  the  method  of  stand  

establishment  and  water  level  dictating  the  optimal  varietal.  (De  Datta  1981)  

1.2.3.3. Rainfed  Lowland  

The  method  of  rice  cultivation  classified  as  rainfed  lowland  is  the  same  as  irrigated  lowland  except  

that  the  water  source  is  local  rainfall.    Dikes  are  a  necessity  within  this  growing  environment  as  there  

is  not  always  a  dependable  water  supply.    The  onset  of  seasonal  rains  determines  when  cultivation  

can  begin  since  the  fields  can  only  be  plowed  once  enough  water  has  accumulated  to  soften  the  

field.    The  method  of  stand  establishment  is  most  often  transplanting  on  puddled  soil;  however,  

some  farmers  use  direct  seeding  in  puddled  soil  or  direct  seeding  on  dry  soil.    Preferred  varietals  and  

growing  conditions  are  similar  to  those  of  the  irrigated  lowland  environment.  

1.2.3.4. Deepwater  

The  primary  characteristic  of  deepwater  rice  cultivation  is  that  the  crop  is  surrounded  by  water  of  

any  depth  from  50  cm  to  100  cm  for  more  than  half  of  the  crop’s  growth  period.    This  type  of  

cultivation  method  is  generally  located  near  river  valleys,  deltas,  and  estuaries.      This  category  of  rice  

cultivation  can  be  quite  ambiguous  given  the  differences  that  can  exist  including  variations  in  

turbidity  of  the  water,  the  rate  at  which  the  water  level  increases,  the  flooding  duration,  the  

temperature  of  the  environment,  and  the  time  of  occurrence  of  cultivation.    All  of  these  factors  

combine  to  create  a  wide  variety  of  rice  crops  that  can  be  classified  as  deepwater.    The  most  

common  method  of  seeding  is  direct-‐seeding,  although  some  farmers  use  transplanting.  

The  main  problems  that  hinder  deepwater  rice  cultivation  include  poor  stand  establishment,  high  

seedling  mortality  rates,  weed  competition,  and  drought  damage  at  the  germination  and  seedling  

stages  resulting  from  direct-‐seeding.    Given  these  potential  problems,  preferred  varietals  have  traits  

such  as  good  seeding  vigor,  greater  submergence  tolerance,  and  enhanced  ability  to  elongate.    

Despite  these  problems,  little  fertilizer  and  pesticides  are  utilized  given  the  ability  of  flooding  

practices  to  effective  manage  the  growth  of  weeds.  (De  Datta  1981)  

25    

1.2.3.5. Floating  

Floating  rice  cultivation  is  rarer  than  the  other  four  cultivation  methods  and  is  most  common  as  a  

subsistence  crop  in  densely  populated  areas  where  no  other  crops  are  able  to  grow.    The  main  

distinction  for  floating  rice  cultivation  is  that  the  water  depth  surrounding  the  plants  ranges  from  1m  

to  6m  for  more  than  half  of  the  cultivation  period.    Ungerminated  seeds  are  broadcasted  onto  dry  

soil  at  a  rate  of  60  kg/ha  to  130  kg/ha  to  plant  the  crop  and  the  rice  plants  grow  as  the  water  level  

rises.    The  issues  associated  with  deepwater  rice  cultivation  exist  for  floating  rice  cultivation  as  well,  

but  can  be  intensified.    Additionally,  traits  for  varietals  that  thrive  in  this  type  of  environment  are  

similar  to  those  of  the  preferred  traits  of  deepwater  rice  varietals.    (De  Datta  1981)  

1.3. International  Data  

The  amount  of  land  dedicated  to  each  method  of  rice  cultivation  varies  from  country  to  country  due  

to  difference  in  geography,  cultural  traditions,  water  resources,  technological  advancements  and  

more.    Of  the  five  rice  cultivation  methods  discussed,  statistics  are  compiled  concerning  the  use  of  

four  of  them,  with  floating  rice  cultivation  being  omitted  due  its  relative  lack  of  use.    The  following  

statistics  are  provided  by  the  Food  and  Agriculture  Organization  of  the  United  Nations  (FAO)  and  

represent  an  annual  average  from  2004  to  2006  of  the  amount  of  crop  area  dedicated  to  each  

growing  environment.  

1.3.1.Asia  

The  majority  of  the  crop  area  for  rice  cultivation  is  dedicated  to  the  method  of  irrigated  lowland  

cultivation.    This  constitutes  58.6%  of  the  135.026  million  hectares  of  total  rice  crop  area  and  is  

heavily  influenced  by  Asian  countries  in  temperate  climates,  such  as  China,  Japan,  and  Korea,  that  

primarily  use  irrigated  lowland  rice  cultivation.    China  alone  cultivates  over  27  million  hectares,  93%  

of  its  total  rice  crop  area,  via  irrigated  lowland  rice  cultivation.    The  cultivation  method  occupying  

the  next  largest  area  is  that  of  rainfed  lowland  by  which  over  43  million  hectares,  or  32.1%  of  the  

total  rice  crop  area,  are  cultivated.    The  remainder  of  the  crop  area  is  cultivated  in  upland  (6.7%)  and  

deepwater  (2.6%)  environments.  (FAO  2006)  

1.3.1.1.Thailand  

From  2004  to  2006,  the  average  annual  crop  area  committed  to  rice  cultivation  in  Thailand  totaled  

10.097  million  hectares.    Of  this,  a  large  majority  was  rainfed  lowland  rice  cultivation  (72.8%),  trailing  

only  Laos  and  Cambodia  in  terms  of  the  percentage  of  total  rice  crop  area  cultivate  by  rainfed  

lowland  methods.      Irrigated  lowland  constituted  the  next  largest  percentage  of  total  rice  crop  area,  

26    

with  25%  of  the  total  area.    The  remaining  two  rice  cultivation  methods,  upland  and  deepwater,  

combined  to  account  for  less  than  2.5%  of  the  total  crop  area,  amounting  to  1.7%  and  0.5%,  

respectively.  (FAO  2006)  

1.4. By-‐products  and  Residues  from  Rice  Cultivation  

Depending  on  the  rice  variety  and  the  cultivation  practices,  different  amounts  of  rice  residue  are  

produced.  There  are  three  main  residues  from  rice  cultivation;  rice  stubble,  rice  husks,  and  rice  

straw.    Rice  stubble  is  the  portion  of  the  rice  stalk  left  in  the  ground  after  harvesting.    The  length  of  

the  stubble  depends  on  the  harvesting  method,  and  is  an  important  parameter  to  consider  when  

studying  the  practice  of  burning  residues  left  in  the  field.    However,  because  the  rice  stubble  remains  

in  the  ground  and  is  not  removed  from  the  field,  it  is  not  available  for  energy  purposes  and  for  the  

most  part  is  omitted  from  this  feasibility  study.    Rice  husks  are  the  portion  of  the  plant  which  

surround  the  actual  rice  grain,  and  are  typically  removed  from  the  field  along  with  the  rice  grain  to  

the  mill,  where  they  are  separated  from  the  grain.    Because  they  are  already  collected  and  

transported  to  a  centralized  location,  rice  husks  are  well  suited  for  utilization  such  as  energy  

production.    Many  companies  already  utilize  rice  husks  as  a  biomass  for  heat  or  power  production,  

usually  in  combination  with  other  biomass  or  fossil  fuels.    The  Siam  Cement  Group  (SCG)  for  example  

currently  derives  25%  of  the  heat  required  in  the  production  of  cement  from  rice  husk.    The  

remaining  75%  comes  from  traditional  fossil  fuel,  namely  coal  and  lignite.    Initially,  rice  husk  was  

used  purely  for  economic  reasons,  as  it  was  much  cheaper  than  the  fossil  fuel  alternatives.    

However,  in  the  past  2-‐3  years,  the  price  of  rice  husks  has  increased  greatly  due  to  competition  for  

this  type  of  biomass.    This  has  led  SCG,  as  well  as  other  companies,  to  search  for  alternative  biomass  

suitable  for  energy  production.    Rice  straw,  for  example,  is  of  interest  due  to  the  large  amounts  

produced  during  rice  cultivation,  much  of  which  is  currently  not  utilized.  

Rice  straw  is  the  bulkiest  rice  residue,  and  the  management  of  this  biomass  often  creates  a  problem  

for  farmers.    Most  cultivation  practices  leave  the  rice  straw  in  the  field.      Current  management  

schemes  include  open  burning,  incorporation  into  the  soil,  use  as  animal  fodder,  and  conversion  into  

energy.    This  paper  will  focus  on  the  possibility  of  using  rice  straw  for  power  production.  

It  should  be  noted  that  rice  straw  can  be  divided  up  into  different  fractions  which  have  different  

properties.    Rice  straw  consists  of  leaf  blades,  leaf  sheaths,  nodes,  internodes,  and  panicles.    By  

weight,  the  largest  component  of  rice  straw  is  the  sheaths  (40.1%),  followed  by  the  internodes  

(27.7%),  leaf  blades  (21.9%),  nodes  (6.4%),  and  panicles  (3.9%).    (Jin  et  al,  2006).  

 

27    

2. Straw  Availability  in  Thailand  

2.1. Pollution  Control  Department  Data  

After  the  National  Plan  on  Open  Burning  Control  was  approved  in  2003,  the  Open  Burning  Control  

Plan  of  Implementation  was  approved.  In  order  to  monitor  this  plan,  the  Pollution  Control  

Department  of  Thailand  needed  to  evaluate  the  current  status  of  open  biomass  residue  burning  and  

its  emissions.    This  study  used  four  methods-‐  literature  review,  observations  via  satellite  images,  

questionnaires/interviews,  and  laboratory  analysis  field  samples.    Each  of  these  methods  provided  

estimates  for  how  much  biomass  residue  is  burned  in  Thailand.  

Using  various  papers  from  sources  such  as  the  Department  of  Land  Development  or  the  Department  

of  Agricultural  Statistics,  the  fractions  of  biomass  residues  burned  were  compiled.    These  values  

were  compared  to  field  experiments  that  were  conducted  by  the  study  to  determine  the  fraction  of  

burned  residues  to  be  used.  

Type  of  Agricultural Fraction  burned  from  

literature  review  

Fraction  burned  from  

field  survey

Fraction  burned  used  

for  assessment

Rice  

Stubbles  and  

straw  

 

0.2-‐0.12  

 

0.83-‐0.96  

 

0.89  

Sugarcane  

bagasse  

Top  and  Trash  

 

-  

0.12  

 

-  

0.29-‐0.54  

 

-  

0.39  

Maize  

Cob  

Leaves  and  Stalks  

 

-  

0.12  

 

-  

0.11-‐0.29  

 

-  

0.2  

Table  2.1.  Fraction  burned  from  literature  review  and  field  experiments.  (PCD  2005).  

To  report  possible  open  burning  areas  in  Thailand,  satellite  images  (collected  using  MODIS-‐  Terra  

and  Aqua)  recording  spots  with  abnormally  high  temperature  were  compared  with  land  use  data  to  

group  hotspots  according  to  land  use  type  and  to  determine  the  potential  type  of  open  burning.    

This  was  used  to  establish  the  potential  risk  areas  of  open  burning  in  agricultural  lands,  shown  in  

Figure  2.1.  

28    

Nan

Chiangrai

Surat Thani

Phayao

Tak

Loei

Chiang Mai

SurinKanchanaburi

Lampang

Sisaket

Roi Et

Burirum

Phrae

Phetchabun

Nakhon Ratchasima

Chaiyaphum

Yala

Khon Kaen

Udon Thani

Kalasin

Krabi

Ubon Ratchathani

Srakaeo

Mae Hong Son

Songkhla

Lopburi

Phitsanu Lok

Trang

AuttaraditNong Khai

SukhothaiSakon Nakhon

Nakhon Sawan

Phichit

Trat

Uthai Thani

Chumphon

Kampaeng Phet

Phetchaburi Chanthaburi

Phang Nga

Satun

ChonburiRatchaburi

Rayong

Lamphun

Nakhon Si Thammarat

Prachinburi

Yasothon

Suphan Buri Saraburi

Ranong

Narathiwat

Mukdahan

Mahasarakham

Chachoengsao

Prachuap Khilikha

Nakhon Phanom

Phatthalung

Chainat

Pattani

Nong Bua Lamphu

Amnaj Charoen

BangkokNakhon Nayok

Nakhon Prathom

Phuket

Trat

Satun

200000

200000

400000

400000

600000

600000

800000

800000

1000000

1000000

1200000

1200000

700000

700000

900000

900000

1100000

1100000

1300000

1300000

1500000

1500000

1700000

1700000

1900000

1900000

2100000

2100000

2300000

2300000

®0 120 24060

Kilometers

Legend

Risk area (rai)

0 - 100,000

100,001 - 500,000

500,001 - 900,000

900,001 - 1,300,000

1,300,001 - 1,700,000

> 1,700,000

Map of risk areas of open burning in agricultural lands in Thailand in 2005

 

Figure  2.1.  Risk  areas  for  open  burning  in  Thailand.  (PCD  2005)  

The  results  from  the  satellite  images  provided  estimates  for  area  burned,  which  could  then  be  used  

to  calculate  the  burned  area  to  cultivated  area  ratio,  shown  below.  

 

Type  of  land  

Area  burned  

(km2)  

Area  burned  (rai) Cultivated  

area  (rai)  

Burn/Cultivated  

area  ratio  

Forest 21,777.62   13,611,012.50   107,531,250.00   12.7  

Paddy  field  

(major  +  

9,151.85   5,719,906.00     57,773,844.00   9.9  

29    

 

Type  of  land  

Area  burned  

(km2)  

Area  burned  (rai) Cultivated  

area  (rai)  

Burn/Cultivated  

area  ratio  

second)  

Sugarcane  

fields  

2,940.10   1,837,562.50     6,667,804.00   27.6  

Maize  fields   4,078.64   2,549,150.00   6,606,653.00   38.6  

Total  area 37,948.21 23,717,631.00   178,579,551.00   13.3  

Table  2.2.  Burned  to  cultivated  area.  (PCD  2005).  

The  questionnaires  and  interviews  were  aimed  at  farmers,  agricultural  officers,  and  environmental  

officers.    Sixty  farmers  in  55  target  provinces  were  interviewed  about  cultivation  and  harvest,  water  

resources,  cause  of  burning,  utilization  of  residues,  awareness  of  negative  impacts  of  burning,  and  

need  for  governmental  supports.    In  each  of  the  55  target  provinces,  one  agricultural  officer  was  also  

interviewed  about  details  on  cultivation  and  harvest,  burning  periods,  cause  of  burning,  types  of  

residues  burned,  and  characteristics  of  residues  before  and  after  burning.    In  addition,  one  

environmental  officer  was  interviewed  in  all  76  provinces  of  Thailand  about  burning  periods,  

awareness  of  negative  impacts  of  burning,  and  types  of  residues  burned.    The  estimates  from  the  

questionnaires  and  interviews  were  compiled  into  the  following  table.  

Type  of  land   Burned/Cultivated  Area, α (%)  from  

Questionnaire/Interview  

Forest   -  

Major  rice   50  %  

Second  rice   75  %  

Sugarcane   50  %  

Maize   15  %  

Table  2.3.  Burned  to  cultivated  area  from  questionnaires  and  interviews.  (PCD  2005).  

The  following  are  conclusions  about  rice  straw  burning  in  Thailand  from  the  Pollution  Control  

Department  study.    Major  rice  plantations  correspond  with  the  areas  where  hotspots  were  most  

prevalent  and  second  rice  areas  were  the  only  areas  with  hotspots  all  year  round.    Also,  open  

burning  on  major  rice  plantations  in  Central,  Northern,  and  Northeast  Thailand  occurred  between  

January  to  February  and  an  average  of  50%  of  cultivated  fields  were  burned.    For  second  rice  areas,  

which  are  mostly  in  Central  and  Northern  Thailand,  about  75%  of  fields  were  burned.    The  main  

reason  for  burning,  collected  from  the  questionnaires  and  interviews  with  farmers,  was  to  facilitate  

land  preparation  for  the  next  crop.    From  the  study,  the  10  provinces  with  the  highest  risk  areas  for  

30    

open  burning  are  Nakhorn  Sawan,  Nakhorn  Ratchasima,  Suphanburi,  Ubon  Ratchathani,  Khon  Kaen,  

Burirum,  Roi  Et,  Surin,  Pichit,  and  Udon  Thani.  

2.1.1. Thailand  Residue  Burn  Data  

From  the  Pollution  Control  Department’s  study,  the  following  figures  depict  the  percentages  of  fields  

that  burned  by  province  and  region,  and  of  those  that  burn,  the  amount  of  residue  burned.  

 

Figure  2.2.  Residue  Utilization-‐  Northern  Thailand.  (PCD  2005).  

 

Figure  2.3.  Residue  Utilization-‐  Northeast  Thailand.  (PCD  2005).  

31    

 

Figure  2.4.  Residue  Utilization-‐  Central  Thailand.  (PCD  2005).  

 

Figure  2.5.  Residue  Utilization-‐  Southern  Thailand.  (PCD  2005).  

  From  this  data,  the  majority  of  Thailand  does  not  burn  rice  straw,  except  for  in  the  central  

region.    And,  of  those  that  do  burn,  most  farms  burn  all  of  their  rice  straw.  

32    

 

Figure  2.6.  Amount  of  Residue  Burned-‐  Northern  Thailand.  (PCD  2005).  

 

Figure  2.7.  Amount  of  Residue  Burned-‐  Northeast  Thailand.  (PCD  2005).  

33    

 

Figure  2.8.  Amount  of  Residue  Burned-‐  Central  Thailand.  (PCD  2005).  

 

Figure  2.9.  Amount  of  Residue  Burned-‐  Southern  Thailand.  (PCD  2005).  

The  data  that  was  gathered  from  our  trip  to  Chainat,  Nakhorn  Sawa,  Suphanburi,  and  Chiang  Mai  

was  similar  to  the  PCD  data.    The  graphs  can  be  found  in  Appendix  A.  

 

 

34    

2.2. Rice  Straw  Availability  in  Thailand  

There  are  two  methods  by  which  the  amount  of  rice  straw  produced  from  rice  cultivation  can  be  

determined.    These  methods,  established  on  a  farm  by  farm  basis,  can  then  be  scaled  up  based  up  to  

provincial,  regional,  and  national  scales.    Each  of  these  methods  rely  upon  statistics  commonly  

collected  concerning  annual  rice  cultivation,  such  as  harvested  area  and  rough  rice  production.  

2.2.1. Area  

The  first  method  entails  calculating  the  amount  of  rice  straw  produced  within  a  certain  area  and  

then  multiplying  that  by  the  total  harvested  area.    The  amount  of  straw  produced  by  this  method  is  

dependent  upon  a  number  of  factors,  with  two  of  the  key  factors  being    type  of  rice  varietal  planted  

and  the  spacing  of  the  rice  plants.    As  discussed  previously,  the  spacing  between  rice  plants  within  a  

plot  is  extremely  variable,  especially  given  the  lack  of  variability  in  yield  over  a  specific  range  of  

spacings.  (De  Datta  1981)  Given  lack  of  consistency  among  farms,  this  method  lacks  the  ability  to  

provide  a  reliable  estimate  of  the  amount  of  rice  straw  produced  through  straw  cultivation.  

2.2.2. Straw  to  Grain  Ratio  (SGR)  and  Harvest  Index  (HI)  

The  second,  and  more  preferable,  method  is  to  use  a  value  known  as  the  straw  to  grain  ratio  (SGR)  

and  apply  it  to  rice  production  data  to  determine  the  amount  of  straw  produced.    The  SGR  is  defined  

as  the  ratio  of  straw  produced  to  the  amount  of  rice  produced.    This  ratio  can  then  be  multiplied  by  

the  amount  of  rough  rice  produced,  statistics  of  which  are  meticulously  kept  given  that  the  rice  grain  

is  the  source  of  economic  revenue  from  rice  cultivation.    Further  support  for  the  use  of  the  SGR  to  

determine  the  amount  of  straw  produced  arises  from  a  study  conducted  by  Shen,  Ni,  and  Sunstol.    A  

wide  array  of  varietals  were  studied  across  multiple  seasons  and  it  was  found  that  grain  yield  

strongly  correlated  with  straw  production,  with  an  r  value  of  0.99.  (Shen  1998)  

Two  other  ratios  that  are  similar  to  the  SGR  are  the  grain  to  straw  ratio  (GSR),  simply  the  inverse  of  

the  SGR,  and  the  harvest  index  (HI).    The  latter  of  these  is  a  ratio  of  the  dry  grain  yield  to  the  total  

above  ground  dry  matter  yield  of  the  plant.  (Passioura  2006)  The  total  dry  matter  of  the  rice  crop  

includes  stubble,  straw,  rachis,  filled  spikelets,  and  unfilled  spikelets.  (Peng  2006)  Another  way  of  

interpreting  it  is  as  a  ratio  of  the  economic  yield  of  the  crop  to  the  biological  yield  of  the  crop.    This  

interpretation  is  used  to  rationalize  research  efforts  to  improve  the  HI  of  rice  crops,  thereby  ensuring  

that  more  of  the  agricultural  inputs  translate  into  a  higher  economic  yield.  (Yoshida  1981)    

Values  for  SGR  and  HI  vary  based  upon  the  varietal,  the  cultivation  environment,  and  climatic  

variables,  with  the  most  significant  factor  being  the  varietal  type.    Commonly  cited  values  for  the  HI  

35    

range  from  approximately  0.40  to  1.0,  while  straw  to  grain  ratios  range  from  0.3  to  2.1.  (Romyen  

1998;  Summers  2003)  Higher  yielding  varietals  usually  have  higher  HI  values  and  lower  SGR  values.    

HI  values  are  common  throughout  the  literature,  but  the  same  is  not  true  for  SGR  values.    Although  

the  two  values  are  related  to  an  extent,  there  is  no  effective  way  to  translate  an  HI  value  into  a  

corresponding  SGR.    Given  the  fact  that  the  SGR  deals  specifically  with  the  rice  crop  residue  analyzed  

by  this  paper,  it  will  be  the  ratio  used  in  all  of  the  calculations.  

2.2.3. Methodology  

The  amount  of  rice  straw  available  annually  in  Thailand  will  be  calculated  through  the  use  of  varietal  

specific  SGRs  and  rough  rice  production  statistics  available  on  a  provincial  level.    The  SGR  of  each  

varietal  will  be  applied  to  the  portion  of  the  total  rice  production  that  is  occupied  by  that  specific  

varietal  and  a  sum  of  the  rice  straw  produced  by  each  varietal  will  be  calculated  to  provide  the  

amount  of  rice  straw  produced  within  each  province.    Then,  using  the  data  collected  by  the  PCD  

survey  concerning  the  utilization  of  rice  straw,  the  percentage  of  rice  straw  burned  will  be  assumed  

to  be  the  percentage  of  rice  straw  currently  unused  and  therefore  available  for  collection  and  use.    

Applying  these  provincially  specific  percentages  to  each  province,  the  amount  of  rice  straw  available  

for  utilization  will  be  calculated.  

2.2.3.1. Rice  Production  Statistics  

Statistics  for  the  amount  of  rough  rice  produced  on  a  national  level  a