Biomass 2 (1982) 161-163

E D I T O R I A L

ANAEROBIC DIGESTION IN EUROPE

As the developed world has increased its technological development over the last 100 years there has been a rapid depletion of non-renewable energy sources such as oil, coal and gas and a requirement for alternative energy sources has brought about an interest in anaerobic digestion. This process, using the activity of anaerobic microbes, will convert a wide range of organic materials, present in waste products, to useful energy in the form of biogas methane. Similarly, the residue is a useful source of fertiliser, protein and irrigation water whilst at the same time the process kills off a wide range of plant and animal pathogens. A number of text books are being produced at the present time which cover a wide area governing anaerobic digestion some of which include biology, engineering, economics, process control, practical applications to specific industries, and the very wide application in the Third World. The benefits for waste disposal, pollution control, disease control, etc., highlight this method as a good recycling system with more than just the one function of energy production.

In Europe, many countries have now instituted biomass energy programmes and large laboratory teams are looking into the microbiology and the engineering of anaerobic digestion. The main areas involved include the development of techniques for producing the methane bacterial consortium with very high activities and rates of reaction, and new digester designs for producing increased activity for methane production. One interesting combination where microbiology and engineering have been brought together is in the development of the up-flow anaerobic sludge blanket (UASB) system at the University of Wageningen in Holland. In this reactor micro- organisms are fixed together in the form of very tight flocs, waste material is pumped past the microbes at a very fast rate and copious amounts of methane are produced in a short hydraulic retention time. This system has particular applications for treating industrial liquid wastes and has been developed commercially on a number of industrial sites. In Germany, a large integrated pilot plant and a full-scale system have been developed at the Institute of Technology in Braunschweig and this research and development team is led by Professor W. Baader. Using computer data collection at

161 Biomass (2) (1982) - © Applied Science Publishers Ltd, England, 1982 Printed in Great Britain

162 EDITORIAL

this Institute a number of digester system designs are being evaluated for the treatment of animal and crop wastes.

In France, wide applications of anaerobic digestion are continuing with use of animal, plant, and of course industrial wastes, and a number of research teams are looking into the basic microbiology of the process as well as studying the way in which parameters during digestion are measured. Professor Buvet at the University of Paris, Val de Marne, is leading one such team. The emphasis in France in some areas is in terms of the control of anaerobic digesters once they have been installed 'on site' in a farm. This research should prove useful in seeing how a national development of digester installations can be brought to successful conclusions.

In the United Kingdom, the Department of Energy through its Energy Technology Support Unit is funding research into the basic microbiology and engineering of anaerobic digestion as is also the UK Department of Agriculture. A number of full- scale demonstration plants have been built, and are now operating producing electricity on some sites. They are being evaluated with respect to their total energy and economic efficiencies. Also in the UK are one or two groups interested in the fate of pathogens during anaerobic digestion, in particular those pathogens which are found in animal wastes and can be transmitted to other animals and to man as well as those plant pathogens which could be disseminated if the digester residue was used as a fertiliser. Results so far indicate that there is good and efficient control of potential pathogens during the anaerobic treatment process.

In Scandinavia, a number of large-scale and pilot-plant digesters have been evaluated for some years now and these are being made commercially available both for industrialists, such as in the sugar industry, and for farmers. A number of satisfied customers are now producing electricity from their own farm wastes and this has particular potential in those countries that have limited non-renewable energy s o u r c e s .

Particular interest, of course, is developing in those countries with warmer climates such as Spain, Italy and Greece and here there is good development of anaerobic digesters from the point of view of the manufacturer and the end user. We must remember that the 'Totem' system produced by Fiat in Turin has, in fact, pioneered the production of electrical energy from farm waste biogas digesters. In warmer climates certain effluents peculiar to these countries, such as citrus fruit and olive oil plant effluents, would make these countries particularly amenable to the exploita- tion of such wastes using anaerobic digestion.

In a number of countries economic studies of digestion are now showing that improvements can be made in the efficiency of performance by changing the design of the digester, and by bringing down the capital cost, enabling the farmer to produce methane gas and possibly electrical energy at favourable cost rates. Some work is commencing in the UK and possibly in Belgium and Holland on the use of residues from the point of view of feeding to animals. This could be an exciting development. Some workers in Sweden also have shown that the value in the protein could be very

EDITORIAL 163

much more than the monetary value in the biogas itself. It remains to be seen whether full-scale feeding of digester protein residues to farm animals will be an efficient process and whether there are any inherent dangers. We look forward to these developments with interest.

The first international conference on anaerobic digestion was held in Cardiff, Wales, UK, in September, 1979. A book on the conference is published by Applied Science Publishers and is now available. 1 This conference was followed two years later in September, 1981, by another on anaerobic digestion held in Travemunde in West Germany. This was attended by well over 400 delegates from 35 countries and included a very exciting poster session with over 120 posters o f a high standard being presented. Significant advances are being made in the large scale application of anaerobic digesters especially with commercial companies and this was reflected in the industrial exhibits at the 1981 conference. A third international symposium is planned for Boston, USA, in 1983. The second conference is now available in a volume published by Elsevier Biomedical Press?

D. A. STAFFORD University College, Cardiff

REFERENCES

1. Stafford, D. A., Wheatley, B. I. & Hughes, D. E. (eds) (1980). Anaerobic Digestion, Applied Science Publishers Ltd, London.

2. Hughes, D. E., Stafford, D. A., Wheatley, B. I., Baader, W., Lettinga, G., Nyns, E. J., Verstraete, W. & Wentworth, R. L. (eds) (1981). Anaerobic Digestion 1981, Elsevier Biomedical Press, Amsterdam and New York.