5.1 Discussions on results on Thailand
As can be found from the result sections (4.1.1-3), small scale biomethanation plants in Thailand enjoys neither high gasification efficiency nor high energy efficiency. As was estimated in these sections, the gasification efficiency is 0.21 in average, which is much lower than Japanese plants where gasification efficiency around 0.8 is usual. Energy efficiency ranges from 0.16 to 0.35, and again much lower than Japanese plants. In Japan, the high efficiency is required so that the burden for treatment of fermentation residue is lessened. On the other hand, the treatment of fermentation residue is not a serious problem in Thailand. The fermentation residue is usually used as compost to the field in the form of solid compost or liquid (or actually slurry) compost. It is also used for accelerator of compost production process. They say that the fermentation residue makes much better compost than usual compost. Since the conversion efficiency is not necessarily high, and thus the process can be simple, the plant cost is cheap for these small scale processes. The simplicity also results in no necessity of operation person or labor cost, and for the case of Nakorn-Rajchaseema Province, farmers themselves can construct the plant.
The use of product gas is usually cooking for this scale, since it is too small for the power generation. The manure from 5 cows is enough for a familyfs cooking for 3 hours, and this data corresponds to Dr. Matsumotofs information in Section 4.2.6. Conventional cooker is used, but for starting fire, an igniter or a match is needed. One problem was that sulfur content resulted in plugging of the cooker nozzle, and it had to be exchanged time to time. However, the introduction of biomethanation cooking system abandons the necessity of liquid propane gas, which costs 350 Bahts a month. This is a fair amount for a farmerfs family, and they said they were happy with the reduction of this cost.
The use of fermentation residue as compost also reduces the amount of chemical fertilizer. Then, the expenditure for the chemical fertilizer is reduced, which also made the farmers happy. Other merits of the small-scale biomethanation plants include improved hygiene due to reduced number of flies, educational effect to the nearby residents. There are not so many problems.
Sustainability of the agriculture with these small-scale biomethanation plants can be discussed as follows for the case of Nakorn-Rajchaseema Province. In terms of material sustainability, no fossil fuel input is necessary. This is because the feedstock is a waste, and is renewable, which in turn is because it is from the livestock. The feed to the cows is produced using the nutrition in the fermentation residue, and the manure of the cows results in the nutrition of the fermentation residue. Thus, it is a nutrition recycling, and can be considered as sustainable agriculture. In terms of energy sustainability, energy of methane gas is from the heating value of cattle manure, which is from the feed of the cattle, coming originally from a solar energy stored by photosynthesis. If chemical fertilizer is used for feed grass growing, it is not sustainable in this sense, but since fermentation residue is used, this process can be considered energetically sustainable. As for economical sustainability, necessity of no special maintenance and labor as well as proper use of the fermentation residue as compost makes the situation very desirable. Installation of the plant is only 5,000 Bahts, and the use of product gas reduces the expenditure for liquid propane gas and chemical fertilizer. Even when only LPG expenditure, 350 Bahts per month is considered, payback time is only 14.2 months. Thus this process is economically sustainable.
Judging from the above discussion, the small-scale biomethanation for cattle manure is a sustainable and desirable process for the farmers. However, the numbers of the plants already installed are limited. Actually, the plant we visited was the only one under operation, and two are under construction. The reason for this should be the farmersf ignorance on this technology. During the discussion with Thai people, it was pointed out that education of people is important. In the rural area of Thailand, the literacy rate is not high, and sometimes children have to help their parents and cannot go to school. There is a case where two brothers have to share a pair of pants, thus only one child can go to school at a time. In this sense, it is important to supply proper information on this technology to the farmers. Actually, the plant we visited was a demonstration plant fully supported by the local government to show neighbors the effectiveness of the biomethanation plant. It is planned that one biomethanation plant per a village for the district of 8 villages are to be installed by local government budget for demonstration. The first one was the one we visited, and the neighbors are now watching how it works.
Considering the fact that we also had large amount of number of biomethanation plants of this size before the World War II, and the same is true for China after 1970s with the governmental policy, this small-scale biomethanation should be effective for the Thai farmers, too, and will be widely used once proper information is supplied. More demonstration project throughout the country should be effective for this purpose.
5.1.2 Ethanol production
In Thailand, 24 plants are licensed to produce ethanol. 6 plants will use cassava as a raw material and molasses will be utilized in the other 18 plants. The target of the ethanol production set by the government is three million liter per day in the year 2011. The production capacity of the 6 plants using cassava will be 1.95 million liter per day or 702 million liter per year, demanding 4.13 million ton of annual amount of cassava. That of the other 18 plants using molasses will be 2.93 million liter per day or 1,506 million liter per year, demanding 4.23 million ton of annual amount of molasses. Among the licensed 24 plants, 6 plants are now in operation (2 for cassava and 4 for molasses). The production capacity of these 6 plants is 1.155 million liter per day and the actual amount of daily production is estimated to be 0.8 million liter.
In order to help the discussion of gsustainable agriculture,h the ethanol production from cassava root is discussed here. At the present moment, as mentioned in 4.2.5, 4 million ton of cassava can be used for ethanol production annually, which is almost enough to supply to the licensed 6 plants. Moreover, about 8 million ton is used for domestic starch consumption and the other 8 million ton is exported. In the future, the amount of cassava production for ethanol may increase, while it is often said that bioenergy utilization may be in conflict with food production, e.g., the international growing demand for ethanol may threaten the stability of domestic supply of food. Even the cassava production for food and that for ethanol are balanced in Thailand now, the future use of cassava root should be carefully determined.
Now the cultivated area of cassava is about 1 million hectare. As mentioned in 4.2.5, the expansion of agricultural land is prohibited, but farmers can change one crop to another. The increase in the ethanol fuel production from cassava is expected to make rural area and people rich. In order to make farmers happy, the profit per unit area of agricultural land, by cassava cultivation, have to be higher than the other crops. The demand of cassava is increasing now. However, the market price of cassava heavily declined before, so financial support by the government to farmers will be necessary in some instances.
From the point of view of energy and material sustainability, the LCA of the Ayudthaya plant has not been analyzed yet, while the energy input was less than the energy output in the TISTR plant. In the Ayudthaya plant, however, corn cores are bought from surrounding farmers and burned in a boiler, and heat is used for fermentation process. Cassava residues are also chipped and burned for heat utilization. Moreover, research on the application of organic compost produced from fermentation residues to cassava field is now being carried out. Agricultural credit cooperation lends money to users of such organic compost (but not to users of chemical fertilizer). Various efforts to make regional agriculture gsustainableh are being made, but the situation is not probably enough to judge as gclosed loop.h Generally speaking, a complete waste recycling within a region may be impossible, but the efforts to increase the recycling, in and around Ayudthaya plant, are being made and politically supported in part. How should we evaluate such a situation from the point of view of gsustainable agricultureh? Methodology of the evaluation of agricultural sustainability is difficult but must be examined.