FeasibilityofRice!Straw!Utilizationfor Small!Scale ...8" "! Abstract(...
Transcript of FeasibilityofRice!Straw!Utilizationfor Small!Scale ...8" "! Abstract(...
-
Feasibility of Rice Straw Utilization for Small Scale Power Production
Dan Hoer
Brock Phillips
Angela Wang
Ruby Woodside
-
2
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)
-
3
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
-
4
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
-
5
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
-
6
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
-
7
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
-
8
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.
-
11
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).
-
12
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).
-
14
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).
-
16
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.
-
17
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