Posted May 1997

FAO Sustainable Rural Environment and Energy
Working Group on Environmental Aspects of Anaerobic Treatments
Workshop on Anaerobic Conversion for Environmental Protection,
Sanitation and Re-use of Residues
Gent, Belgium
24-27 March, 1997

Conclusions and recommendations

See related: "Abstract: Anaerobic digestion of agroindustrial byproducts and wastes"

Conclusions

Anaerobic treatment processes become more and more important in Europe and lesser developed countries for the treatment of low and high loaded wastewater, slurries, slurries with co-substrates and solid organic wastes.

The implementation of anaerobic treatment processes in East-European-Countries (Latvia, Poland, Russia) is relatively seldom, but there is a strong need for such technologies for pollution control, sanitation and production of renewable energy.

The implementation of anaerobic treatment processes and the re-use of residues differs considerably in the individual European and Non-European countries due to the different legal regulations, different economical situations and sometimes also due to a lack of acceptance of this technology by civil engineers.

Combined processes with the formation of high value products (e.g. lactic acid) together with biogas give the chance for an economic use of organic wastes and biomass.

Two-step processes with fungal pre-treatment can be a solution for an efficient anaerobic treatment of wastewater containing toxic or low degradable components, e.g. lignin.

Thermophilic anaerobic treatment sometimes allows the conversion to biogas of wastes that cannot be degraded by mesophilic cultures; however, details of the different species and degradation routes are mainly unknown.

Experiments with hyperthermophilic anaerobic conditions have shown, that the methanogenesis is inhibited whereas the degradation of polymeric compounds shows a strong increase due to fast acidogenesis. Hence, hyperthermophilic anaerobic conversion can be applied as a pre-treatment for acidification or an efficient separation of solids.

Psychrophilic anaerobic treatment experiments with specially adapted cultures have shown that manure treatment at relatively low temperatures (6°C) is possible and eventually applicable in agricultural practice.

Sulphur and nitrogen removal can be integrated in anaerobic digestion processes by the development of new process technologies.

The knowledge on methane oxidation within the soil cover of landfills should be used for the development of biofilters to treat biogas streams from small plants that cannot use biogas for energy production in an economical way.

Completely covered anaerobic ponds with support media can be an efficient way for the treatment of highly loaded wastewater at low investment and operation costs.

Co-digestion is a way to make the anaerobic treatment of slurries (manure) cost-effective due to the profit from waste treatment and the additional gas yield.

Biogas from cultivated biomass might be an economic energy resource if the biomass is treated together with wastes that yield a profit for waste treatment.

Sanitation of hygienically risky wastes by thermophilic anaerobic digestion plays an increasingly important role in agricultural waste management for preventing the distribution of infectious diseases.

Newly developed methods for an automatic determination of the sludge activity or the inhibitory effects of wastes are very important for process control and pre-testing of the degradability of unknown substrates.

Information on dechlorination of organic substances in anaerobic processes is important, because chlorinated organics, e.g. pesticides, are used in agriculture. The knowledge about the degradation of these compounds in anaerobic digestion processes is relatively scarce.

An on-site treatment of sewage is often necessary in rural areas but only few low cost systems are available.

Recommendations for future activities

The Working Group made the following recommendations:

1. that communication and information distribution via electronic media (e.g. www pages), mail (discussion lists) and conferencing will be used and made available by FAO to the benefit of the Working Group;

2. that the above will be used by the members of the Working Group to the fullest extent possible to improve collaboration, and to develop and distribute databases and other information systems;

3. that all members and FAO will give their fullest possible support to the efforts of the Expert Groups;

4. that information on new international research and support programmes on anaerobic conversion technologies will be sent by any member to the electronic discussion list and/or distributed to all other members by the WG-coordinator (Mr. Weiland) or by FAO;

5. that international research projects on anaerobic conversion technologies should be prepared by the members of the Working Group. Mr. Verstraete, Georgacakis and Weiland were named as scouts for relevant projects.

For Expert Group 1 (Data Collection)

Mr. Marchaim agreed to continue elaborating a proposal for a database system on anaerobic digestion together with assistance from Mr. Hulshoff Pol, Rozzi, Kalyuzhnyi and Mrs. Popovich and Parshina. The proposal will be presented to the Working Group members for discussion and contributions.

For Expert Group 2 (Economic Evaluation Model)

Mr. Georgacakis presented an economic evaluation model, a draft copy was distributed. Mr. Marchaim, Hulshoff Pol, Eymontt and Romaniuk offered to contribute further details and data. A questionnaire will be distributed to members for further collection of information.

For Expert Group 3 (Legal Framework of Standards)

Mr. Thyselius presented regulatory limits for heavy metal contents in sludges and anaerobic conversion products from several European countries. To complete this information for future reference a questionnaire will be prepared and mailed to all members.

The next Workshop will take place in spring 1999. Two members of the Working Group - Mrs. Nozhevnikova (Russia) and Mr. Georgacakis (Greece) - have made an offer for hosting the next Workshop. The majority of the present Working Group members voted for Greece. Mr. Georgacakis will organize the workshop, if possible in a rural environment.