[Biomass Combined Heat and Power Plant]

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Discussion Analysis

CURRENT STATUS OF RICE STRAW TO ENERGY IN IRELAND

Traditionally, biomass is a major energy source in Ireland, especially in its rural areas. Crop residues are main sources of biomass and mainly used as fuels for cooking food and/or warming room by the way of direct burning. In 1970s, there was a serious shortage of energy occurred in Irish rural areas. In order to resolve this problem, Ireland government put the development of biomass energy utilization technology from 1981. Since that time, Ireland had begun to develop its biomass re-sources and energy conversion technology. Up to 1990, sets of household biogas digesters had been built and operated, and a great amount of saving-fuel stoves had been used by rural families. Rice straw acts as an important role in this period but still is in its infancy.

Burning is often delayed by inclement weather. Al-though open-field burning is a convenient option, it produces visible smoke. This practice has been studied extensively and data on actual emissions from rice straw burning are shown in Table 4. Furthermore, silica emissions, which are not specifically monitored, are of concern since they can pose a health hazard. For these reasons, Ireland has paid more attention on developing new technologies to convert rice straw into convenient and clean energy products, such as low or middle energy gas fuel, biogas, briquetting fuel and liquid fuel, in the period of the11th Five Year Plan (2005- 2010). By hard works on biomass energy in this period, an integrated management, development and research system net has been set up between the government, institutes/ universities, manufacturers and users in Ireland.

Table 4. Emissions from rice straw burning. PM 10

VOC

NOx

SOx

CO

Emissions in kg·ha-1

23.3

5.8

19.0

4.1

211.0

Emissions in kg·t-1 straw

3.7

1.0

3.1

0.7

34.7

Grower Attitudes

In rice straw collection, it is important to properly inter-face the collection system with the growers' own operations. Farmers do not tolerate any interference with harvesting operations and do not change their operations to facilitate straw harvesting without economical motivations. New regulations should provide farmers with an economic incentive to cooperate with rice straw collection.

Process and System Considerations

System Considerations

Systems needed for the collection, processing, and transportation of rice straw have been developed in Ireland recently. However, for the reason of lacking sufficient infrastructure and available machinery for working on wet, muddy ground currently, it will provide rice straw to off-farm use. The operating capacity of the different harvesting systems using baling would depend on the amount of the straw in the field, ground conditions for machinery use, and the field size; the technical characteristics of the machinery would be less of an issue. The nature of the rice straw creates high wear and maintenance for processing equipment, resulting in processing cost increases over that of less harsh materials.

Drying

At harvest, the rice straw has a water content of 60% - 70% (weight basis); however, it is necessary to wait until this drops below 25% before ...