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close this book Boiling Point No. 22 - August 1990
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Household Cooking Fuel

Hydrogen Sulphide & Sulphur Dioxide Emissions from Stalks, Coal & Biogas

By R A Hamburg, Omega - Alpha Recycling Systems, Rt. 1, Box 51, Orma, West Virginia 25268, USA, from a pilot study in China.

A/though Hamburg's paper is mainly concerned with biogas, the following extracts also concern the use of plant stalks and coal. The paper concentrates on hydrogen sulphide and sulphur dioxide emission but as H2S is produced at the biogas generator rather than in use, this part is not reproduced here - Ed.

The World Health Organization has now concluded that respiratory diseases are the chief cause of death in developing countries and that acute respiratory infections (ARI) are a major cause of infant mortality in some areas. While there are numerous factors involved, one of the most likely causes is the exposure to emissions from household cooking and heating fires.

Many of the problems brought about by over-population, such as over-use of agricultural lands and biomass energy resources, which the Chinese have been facing for centuries, are now being experienced in a growing number of areas around the world. Biogas systems offer benefits in renewable household energy, small-industry process energy, increased crop production by maintenance of better soils, and improved sanitation and respiratory health.

A pilot study of hydrogen sulphide and sulphur dioxide concentrations in cooking areas was conducted in Henan province (Peoples' Republic of China). Data were collected in cooking areas utilizing crop stalks, coal and biogas generated from family scale anaerobic digesters and a large, distillery residue system. Although biogas was not scrubbed in any case, no recordable levels of hydrogen sulphide were detected in any of the areas. Sulphur dioxide levels in cooking areas where coal and stalks were used were found to average about 4 times higher than for biogas. The differences were statistically significant for coal but not for stalks. Problems and considerations for related studies and the aspects of biogas in ameliorating indoor air pollution are discussed.

Sulphur Dioxide Emission

Sulphur dioxide is classified as an irritant gas and is the primary component of sulphur emissions from combustion of fossil and biomass fuels. It is generally present in the atmosphere of industrial and urban centers at 1 ppb-1 ppm (1 ppm S02+2620 micrograms/m ) and in remote areas at 50-120 ppt (parts per trillion). Symptoms of upper respiratory irritation have been reported at levels of 2-5 ppm, and concentrations above 20 ppm have noticeable irritant, choking and sneeze-inducing effects. Higher concentrations promptly result in coughing and nasal discharge and can cause suppurative bronchitis and asthma- and influenza-like symptoms. Very high levels may cause asphyxia leading to death or the development of chemical broncho-pneumonia which may also be fatal in a few days.

TABLE 2 - Recorded 8-hour SO2 Levels in Cooking Areas

Fuel Type

Location

No. of Samples

Range (ppm)

Mean

Deviation (ppm)

Biogas

All sites

16

0-3.9

0.86

1.12

Coal

All sites

15

1. 7-9

3.5

2.29

Stalks

Zhu Yuan

5

0-13

3.3

5.5

Biogas

Zhu Yuan

5

0-3

0.60

1.34

Coal

Nanyang

5

1. 7-4

2.4

0.93

Biogas

Nanyang

5

0.4-0.9

0.52

0.22

Outdoor levels in one of the cities varied from 0.4 to 0.8 ppm SO2 at two different sites. The five stalk-burning village kitchens had widely varying 8-hour averages ranging from 0 to 13 ppm, with a mean of 3.2 ppm (standard deviation = 5.5). Levels in the 15 coal-burning kitchens varied from 1.7 to 9 ppm, with a mean of 3.5 ppm (s = 2.29). (As might be expected, there was no recordable level of H2S in any of these kitchens). Both stalks and coal resulted in about four times higher SO2 levels than biogas. (A test in one natural-gas burning city kitchen showed a SO2 level of 1.3 ppm). The data are summarized in Table 2.

The author would like to thank: Professors Li Junde and Li Jue and the other members of the Biogas Group of the Energy Research Institute, Henan Academy of Sciences, for their hospitality and assistance in data collection; Drs Richard Hosier and Rober Wirtshafter of the University of Pennsylvania and Kirk Smith of the East-West Center for their inspiration and direction; 'Biomass' reviewers for assistance with the manuscript in general; and Allen and Dorothy Hamburg for instrumentation.