Biogas Plants UN-ECDC

A project of Volunteers in Asia Renewable Sources of Eneruv, Volume II; Biosas by; Economic and Social Commission for Asia and the Pacific Published by: United Nations Economic and Social Commission for Asia and the Pacific The United Nations Building Rajadamnern Avenue Bangkok 2 Thailand Available from: United Nations Economic and Social Commission for Asia and the Pacific The United Nations Building Rajadamnern Avenue Bangkok 2 Thailand Reproduced by permission of the United Nations Economic and Social Commission for Asia and the Pacific. Reproduction of this microfiche document in any form is subject to the same restrictions as those of the original document. % ~IJINOIMC.Ah [ALo-‘. ‘Alilb ;. -THE ‘PAtiiN ,:‘/ _ -? ,’< _a .F 0 _”‘. Yf ,.: c y I . .I. ‘“>0, .- .h,. _I. d;i r . -. -‘I .. * CL. ___---- ..-’ L----- .,.:. .’ $.f. RENEWAl#ESOtiRGESii ASIA AND T ECONOMIC AND TECHNICAL CO-OPERATION AMONG DEVELOPING COUNTRIES 1 ST/ESCAP/WO 1 The designations employed and the presentation of the material in this publication do not imply the expression of any opinion what- soever on the part of the Secretariat of the United Nations concerning the legal status of any country, territbry, city or area or of its authori- ties, or concerning the delimitation of its frontiers or boundaries. The mention of any firm or licensed process does not imply endorsement by the United Nations. CONTENTS Page Preface ........................................................ (0 Introduction .................................................... 1 I. Biogas plants installed in the ESCAP region ................... I II. Use of the products of biogas plant ......................... 11 III. Methods of improving plant productivity ..................... 14 IV. Activities in the ESCAP region ............................. 15 v. Economic, social and environmental aspects .................. 18 VI. Scope for ECDC and TCDC ............................... 22 Cost-benefit analysis of Indian biogas system: a case study ................ 2s I. Cost-benI% analysis and some empirical results ..... - ........... 2s II. Some methodological problems ............................ 48 III. Some approaches to methodological problems ................. 53 IV. Conclusion ........................................... 58 Abbreviations ................................................... 63 Key to numbers in entries under experts and institutions .................. 65 Alphabetical list of experts and institutions ............................ 69 Subject index - by projects ........................................ 231 Bibliography .................................................... 245 PREFACE The current volume is the second in a series of sectoral directories on renewable sources of energy to be issued under the ESCAP publications programme on co-operation among developing countries. With this volume the title of the series has been changed from TCDC to ECDC-TCDC to reflect the expanding scope and contents of the volumes intended to promote and support economic as well as technical co- operation among developing countries. The present volume, like the preceeding one on solar energy and the others to follow, carries not only inventories of experts and institutions and the projects under- taken by them but also technological as well as economic details of the designs, pro- totypes and hardware developed in ESCAP member countries in Asia and the Pacific. While it is hoped that more details will be made available, the information contained in these volumes may be found adequate for initiating programmes of co-operation among developing countries. In preparing the roster of experts and institutions, the ESCAP secretariat has relied on the information provided by the experts and institutions concerned and expresses its appreciation of the co-operation extended by them. While every en- deavour has been made to include as many experts and institutions as possible the coverage may not be exhaustive. The secretariat will greatly welcome suggestions for improving the coverage of this volume as well as material for publications in the series now under preparation on wind energy and mini-hydro plants and the others envisaged. It is hoped that all the volumes in the series will be found particularly useful in con- nexion with the forthcoming United Nations Conference on New and Renewable Sources of Energy. Like the earlier publications issued in the TCDC series, funds for the present volume have been made available by the Netherlands Government as extrabudgetary assistance to ESCAP. This exemplifies “triangular co-operation” under which developed countries contribute to a joint undertaking to promote co-operation among developing countries. INTRODUCTION The decay of organic matter, particularly human, animal and plant wastes, in the absence of air produces an inflammable gas which consists mainly of methane (CH,) and carbon dioxide (CO,). The gas is known as biogas and the process as an- aerobic digestion or fermentation. This process can be used to the great benefit of the rural community for a nu,mber of reasons. First, it produces a smoke-free fuel. Second- ly, it produces anexcellent fertilizer. Thirdly, it destroys most of the disease-carrying pathogens and parasites. Fourthly, the raw materials needed in the construction of the digestion and in its operations are available in rural areas. Finally, the biogas technology is appropriate to rural conditions as comparatively sophisticated devices and highly qualified expertise are not involved. The main handicap in biogas application is the relatively high capital cost which small-scale farmers cannot afford on an individual basis. Besides, as with any new technology, it needs well-planned programmes for promotion and extension. The present introduction is meant to give a brief account of the stage of development of and of the economic, social and environmental issues in biogas technology in developing countries in the ESCAP region. Several more comprehensive technical . reviews of the subject have been published.’ * 3 4 ’ I. BIOGAS PLANTS INSTALLED IN THE ESCAP REGION There are two main types of biogas plant that have been developed in this region; the fixed-dome digester, which is commonly called the “Chinese digester’ (see figure 1) and the floating gas holder digester known as the Indian (KVIC) digeste. (see figure 2). The digesters used in the other developing .countries in the ESCAP region, with the exception of the bag digester, are slightly modified forms of one or the other of these two main types. 1 A Chinese Biogas Manual, translated from the Chinese by Michael Crook and edited by Ariane van Buren from the original by the Office of the Leading Group for the Propagation of Marshgas, Sichuan Province, China (London, Intermediate Technology Publications, 1979) 2 “Guidebook on biogas development*‘, Energy Resources Development Series, No. 21 (United i4ations publication. Sales No. E.80.II.F.10). 3 Sichuan Rovincial Office of Biogas Development, “Biogas technology and utilization” (Chengdu Seminar, China, 1979). 4 Sichuan Provincial Institute of Industrial Buildings Design, “Construction c;f marsh-gas-producing tanks @igesters)in simple ways”. 5 Simplified Biogas Digester Drawings. Compiled by the South-west Engineering Institute, Beijing, China, 1979 (in Chiiese). 1 A. THE BIOGAS DIGESTER 1. Fixed dome digester (China) This digester which was developed and is widely used in China runs on a continuous-batch basis (see figure 1). Accordingly, it could digest plant waste as well as human and animal wastes. It is usually built below ground level; hence it is easier to insulate in a cold climate. The digester can be built from several materials, e.g. bricks, concrete, lime concrete and lime clay. This facilitates the introduction and use of local materials and manpower. The variable pressure inside the digester was found to cause no problems in China in the use of the gas. 2. Floating gas holder digester (India) This type was developed in India and is usually made of masonry (see figure 2). It runs on a continuous basis and uses mainly cattle dung as input material. The gas holder is usually made of steel, although new materials such as ferrocement and bam- boo-cement have already been introduced. The original version of this floating gas holder digester was a vertical cylinder provided with partition wall except for the small sizes of 2 and 3 m3 of gas per day. The main characteristic of this type is the need for steel sheets and welding skill. 3. Flexible bag digester This digester is made usually of Hypalen-Neoprene (see figure 3). It is portable, could be easily erected and has low capital cost. It has, however, a short lifespan in view of its low resistivity to ultraviolet rays and rodents. 4. Other types of digesters (a) Taper digester with floating gas holder (Nepal) This digester (see figure 4) is more suitable than the vertical type digester in sites with a high water-table. (b) Floating gas holder with water seal (Pakistan) This type (see figure 5) eliminates the smell and decreases gas leakage and cor- rosion of the gas holder. It is, however, considered more expensive than the original model. (c) Two-chamber digester (Philippines) Clogging problems hindered the widespread use of this digester (see figure 6), requiring more appropriate designs of the inlet and outlet. (d) Oil drum digester (Indonesia) This digester has been used for research purposes (see figure 7). The oil drum tends to rust out within a few years. 2 Gas

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