Bioconversion of Organic Residues for Rural Communities (UNU, 1979): Analysis of bioconversion systems at the village level: Future development possibilities

Bioconversion of Organic Residues for Rural Communities (UNU, 1979)

From the charter of the United Nations University

Foreword

Perspectives on bioconversion of organic residues for rural communities

(introductory text...)

Introduction

Sources of available nutrients

The most suitable materials for bioconversion

Characteristics of residues

Bioconversion systems

Physical and chemical treatments

Microbial conversion

The animal conversion phase

Summary

References

Availability of organic residues as a rural resource

(introductory text...)

Discussion summary: Papers by van der Wal and Barreveld

Micro-organisms as tools for rural processing of organic residues

(introductory text...)

Introduction

Microbial utilization of mono- and di-saccharide residues

Microbial conversion of starchy residues

Microbial conversion of complex mixtures of compounds (Polysaccharides, Proteins, Lipids, etc.)

Microbial utilization of cellulose and ligno-cellulose residues

Algal culture as a source of biomass

Microbial utilization of silviculture biomass

Micro-organisms and marine and freshwater biomass

International studies on processing organic residues

References

Production of feed as an objective for bioconversion systems

(introductory text...)

Introduction

General characteristics

Manure as feed

Sewage-grown micro-algae

Conclusion

References

Environmental goals for microbial bioconversion in rural communities

(introductory text...)

Introduction

Health and water economy

Fertilizer and energy economy

Concluding remarks

References

Discussion summary: Papers by Porter, Berk and La Rivière

Strategies for developing small-scale fermentation processes in developing countries

(introductory text...)

References

Discussion summary

Production of microbial protein foods on edible substrates, food by-products, and ligno-cellulosic wastes

(introductory text...)

Preface

Introduction

Contributions to the solution of nutritional problems

Development of protein-rich vegetarian meat substitutes in the western world

References

Discussion summary

The role of ruminants in the bioconversion of tropical byproducts and wastes into food and fuel

(introductory text...)

Introduction

Nutritional limitations in the use of tropical by-products and waste

Practical experience with tropical by-products and wastes as feed for ruminants

An integrated system for converting tropical feeds and byproducts into milk, beef, and fuel

References

Discussion summary

Possible applications of enzyme technology in rural areas

(introductory text...)

Introduction

Biocatalytic processes

Enzyme hydrolysis of manioc

Whole cell systems

Cellulose degradation and utilization

Transfer of enzyme technology to rural communities

Conclusions

References

Discussion summary

Indian experience with treated straw as feed

(introductory text...)

Introduction

Experience with straw treatment

Field testing and demonstration of straw treatment

General considerations

Summary

Annex 1. The energy efficiency of the two-stage, feed-fuel processing of straw in indian villages

Annex 2. Method of calculating the value presented in table 2 for the efficiency of naoh energy usage

Annex 3. Recommendations to farmers on the treatment of straw

Annex 4. Calculated efficiency of milk production by straw-fed village buffaloes

References

Discussion summary

Indian experience with algal ponds

(introductory text...)

Introduction

Cultivation of algae in wastes for feed

Problems of contamination

Cultivation of algae for biofertilizer

References

Acknowledgements

Discussion summary

Organic residues in aquaculture

(introductory text...)

Introduction

The range of production in aquaculture

The value of organic wastes

Direct feeding

Concluding remarks

References

Discussion summary

Biogas generation: developments. Problems, and tasks - an overview

(introductory text...)

Introduction

What is biogas?

Microbiology of CH4, or bio-methanogenesis

The biogas plant-some technical considerations

Environmental and operational considerations

Developments and processes for rural areas

Cost-benefit analyses

Health hazards

Bottlenecks, considerations, and research and development

References

Discussion summary

Mushroom production technology for rural development

(introductory text...)

Materials and methods for growing mushrooms under natural or field conditions

Growing mushrooms under semicontrolled conditions

Results and discussion

References

Discussion summary

The combination of algal and anaerobic waste treatment in a bioregenerative farm system

(introductory text...)

Introduction

Algae production on organic wastes

The bioregenerative farm

References

Discussion summary

A continuous composting system for disposal and utilization of animal wastes at the village level

(introductory text...)

Status of land utilization and disposal of animal wastes

A continuous composting system for land utilization of animal wastes at the village level

References

Bioconversion of fruit and vegetable wastes

(introductory text...)

State of the art of bioconversion

Technical transfer

Integrated research on agricultural waste reclamation

(introductory text...)

Introduction

Production of yeast from soybean cooking waste at miso factories

Application of soy waste as koji substrate for rice miso manufacturing (5, 6)

Conclusion

References

Discussion summary

Solid state fermentation of starchy substrates

(introductory text...)

Introduction

Materials and methods

Agro-economic perspectives

Summary

References

Discussion summary

Production of single-cell protein from cellulose

(introductory text...)

Introduction

Experimental results

Discussion

Summary

References

Acknowledgements

Discussion summary

Analysis of energy cost of integrated systems

(introductory text...)

Energy cost and energy requirement

Why energy analysis?

Net energy intensity

What criteria are offered by energy analysis?

Conclusion

References

Analysis of bioconversion systems at the village level

(introductory text...)

Introduction

Approach to bioconversion analysis

Some results and costs from integrated systems

Future development possibilities

Conclusions

Summary

References

Nutritional evaluation of bioconversion products for farm animals

(introductory text...)

Introduction

Testing procedures for determination of nutritional value

Bioconversion products: toxicology - problems and potential

(introductory text...)

Summary

References

Nutritional evaluation in humans

(introductory text...)

Introduction

Evaluation of products of bioconversion for human consumption

Procedures for nutritional evaluation in humans

The evaluation of various food products

Concept of productivity

Conclusions

References

Discussion summary: Papers by van Weerden, Shacklady, and Bressani

Biomass from organic residues for animal and human feeding

(introductory text...)

References

Discussion summary

Appropriate biotechnology - summary remarks

(introductory text...)

References

Other UNU Publications

(introductory text...)

Books

Future development possibilities

Organized bioconversion of residues seems to be practiced most in the People's Republic of China (14), but it is in its infancy in other less developed countries. However, the possibilities are immense with both conventional and newer processes. A survey of Microbiology Abstracts, Section A (15), revealed at least 25 papers* on processes applicable to rural residues. Thus, a determined effort to work at the rural level on rural residues would yield the best results.

This section indicates some possibilities for bioconversion in the future. Residues from industries situated near rural centres are also listed, because the waste from a medium-sized industry will probably suffice for a whole community. The possibility of generating employment from use of industrial waste should not be ignored. In the Indian context, large industrial undertakings situated near the outskirts of townships and generating usable waste should be encouraged to recycle and re-use the waste instead of resorting to expensive treatment not leading to agricultural products. This would also prevent pollution of the neighbourhood.

Two requirements have to be met for widespread propagation of bioconversion methods: (a) designs for cheap fermenters, and (b) culture or inoculum banks to supply starter cultures. This is similar to the large-scale effort now being launched to supply blue-green algal cultures (16).

If these facilities are provided, and this does not seem too difficult a task, various kinds of residues can be used (Table 7). The table gives only a representative sample and is not meant to be comprehensive.

Locally available grain, millet, and weed residues are added here to re-emphasize the need to make the best use of existing wastes by supplying starter cultures for better ensilage, or by supplying better designs of biogas digesters or fermenters. The available quantity is so vast that commensurate work seems to be called for in order to solve the urgent problem of food, feed, and energy shortages. In many parts of India, harvested straws rot because the harvest and the monsoon are concurrent. Even good drying systems to prevent deterioration (negative bioconversion?) will go a long way to alleviate the problem. Providing every reasonable-sized community a 6 m x 6 m drying platform of hard plastered mud or cement with embedded pipe flanges in a grid would help the villagers dry and preserve their crop residues more effectively. The pipe flanges are used as anchors to fix tent driers of plastic or thatch.

Items 2 and 8 in the table are examples of the variety of process liquors now being underutilized. Paddy steep liquor is available in millions of litres in most rice-producing countries as a result of the parboiling process, and makes nutrients available for fermentation (17). Similar liquors are biogas effluent (4), silk spin liquor (conservatively estimated at about 50 million I per year in one district to Karnataka State alone), coconut water (0.5 x 10(6) tons per year) (18), turmeric" and areca-processing liquors. All these liquors need to be supplemented by a molasses or glucose source for yeast manufacture; they supply N. P. K, and essential vitamins. Items 3 and 9 point out the need for a close look at CO2 as a resource (19). Both biogas as generated and combustion stackgases are thermally valuable as well as being rich sources of CO2 for algal cultures. These gases, being neutrally buoyant, can be transported in balloons to desired locations. Prosopis and forest residues are extremely valuable resources that are now used only for burning. Thayer (20) has grown cytophaga on such material to make fodder. Items 5 and 11 are very effectively used in China (14), and their use should be propagated in other countries.

Regarding item 6 in the table, in India, wherever illicit liquor is brewed, it is done under conditions of very low sterility. Jaggery and acacia bark with some roots and herbs are added to water and sealed in a pot and buried underground. The brew is ready to distill in 10 to 15 days. If the yeast can be induced to multiply under aerobic conditions, it might be a good source of protein. Item 7 refers to the need to develop valuable starch or sucrose residues as cheap substrates for indigenous fermentation. Cotton dust availability in India is 33,000 tons per year (18), and is in a form suitable for enzymatic degradation to glucose, or for 20-day aerobic compost formation. Fish wastes (item 10) can be ensiled in a remarkably simple process (21). The product is a valuable poultry ration and is stable for up to three years. Silkworm cocoons can be dried immediately (to prevent negative bioconversion) and fed directly or ensiled by the same method used for fish wastes.

TABLE 7. Residues Locally Available in Rural Areas and from Proximate Industries

Rural Residues

Grain, millet residues, aquatic weeds, etc.
Paddy steep liquor, biogas effluent, other processing liquors
CO: from biogas
Prosopis, etc., forest residues
Dung, faecal matter
Illicit liquor process adaptation

Industrial and Urban Residues

Carbohydrate residues: sago (cassava waste, molasses, spent wash, cotton dust)
Paddy steep liquor, silk spin liquor, coconut water, areca, turmeric liquors, etc.
CO: from thermal, cement, and fertilizer plants
Fish wastes, silk worm cocoons
Sewage sludge

This brief review of future possibilities for rural communities would not be complete without a design for a cheap big-solar fermentation device. This design is not now in use, but might serve to stimulate ideas and improvements.

Figure 3 shows a box-type solar cooker (3) adapted for fermentation. This is made of hollow tiles and plastered with cement with a high coefficient of thermal expansion; e.g., lime/wood ash. The cycle undergone is: Expose to the sun to sterilize, cover to ferment, re-expose for broth concentration. To maintain the healthy growth of aerobic organisms, a compressor driven by a biogas engine, or wind power, or bicycle power, is used to aerate the brew. The tiles provide cellular air spaces as insulation during the sterilization cycle. If it is cloudy, wood-fired heat can be used to sterilize the broth. Though this kind of device cannot mass-produce material, it can be used to provide needed protein for village children.

Figure. 3. Box-type Solar Cooker Adapted for Fermentation