Chatziathanassiou Artemios Center for Renewable Energy ... - Nifty

AD/Nett - Technical Summary - CRES 

CONSTRAINTS OF ANAEROBIC DIGESTION FOR ENERGY EXPLOITATION IN GREEK 

LIVESTOCK FARMING 

1. Introduction 

Chatziathanassiou Artemios 

Center for Renewable Energy Sources 

19th. km Marathonos Av. 

GR-19009 Pikermi, 

GREECE 

Tel: +30 1 6039 900 

Fax: +30 1 6039 904,5/6038006 

E-mail: atemis@cres.gr 

Abstract: The main purpose of this work is the identification of the constraints hindering the 

anaerobic digestion (AD) of animal excrements for energy purposes in Greece. The theoretical 

methane potential generated from animal manure, comes up to 1,45 million m 3 /day with an 

energy potential 1,2 MTOE. The potential users for biogas production through AD would be 

focused on intensive livestock and especially on medium-large scale livestock units. A few 

efforts of biogas applications were made in the past through E.U. or National projects, but they 

have fallen into disuse. The AD for biogas production is seldom used for livestock waste 

treatment at the moment. The no-acceptability of biogas applications is attributed to a number 

of structural, financial, attitudinal and awareness constraints. The non-acquaintance of Greek 

farmers with the optimized use of biogas for energy production and the “lost credibility” of the 

biogas technology are some of the determinant factors. As well as the structural problems of the 

livestock sector and the high financing risks are some other gaps minimized biogas 

technologies approval. Finally, the environmental arguments of a biogas implementation are 

weak currently in Greece taking into account the global change and the reduction of land and 

water pollution. However, the penetration of AD schemes would be based on existing and 

coming financing means for the promotion of RES as well as on the awareness of Greek 

farmers by demonstration and promotion actions. 

In Greece, the agriculture contribution to the gross domestic product is only 12% and the livestock 

production represents the 30% of the gross agricultural income. The latter does not secures selfsufficiency 

of national market except for poultry farming, causing an annual import of livestock 

products more than 1.2 billion $ (7). Sheep, goats and lambs breeding represent the highest 

percentage of livestock (5) and its breeding is mainly shepherded. On the other hand, cattle and pig 

breeding is a promising agricultural activity and, moreover, it is structured with advanced production 

systems. Medium-large livestock units are located in current regions but the manure density is lower 

than it has noticed in Western Countries. A few “nitrate sensitive” sites have been defined at areas 

which are more affected from agricultural activities. 

The most common manure management method in medium-large livestock units in Greece is the 

disposal of liquid manure in anaerobic stabilization lagoons or the collection and de-watering of solid 

wastes on dung heaps. Anaerobic digestion (AD) for biogas production is seldom used for livestock 

waste treatment in Greece at the moment. This is mainly due to the lack of information, proper 

infrastructure, state interest and waste management infrastructure. 

A few efforts of biogas applications were made in the past through EU or National projects, but they 

have fallen into disuse. 

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2. Potential resource 

On the basis of the EUROSTAT figures (1995) including all the kinds of breeding animals, the 

animal manure production is estimated up to 38,000 tonne/day. Taking into account that the largest 

portion of Greek livestock farming is not intensive, it is concluded that the available biogas potential 

would not include sheep, goats and lambs manure. This farming is mainly shepherded, so the manure 

produced is spread over the grazing land. 

The potential for biogas production through AD are likely to be focused on intensive livestock, 

especially on medium-large scale livestock units consisting of cattle, brood sows and poultry 

farming. The terms of medium and large scale livestock units were defined on an inventory of Greek 

Agricultural Bank (31/12/1995). Depending on these figures, the number of breeding animal heads 

and the medium-large scale units for cattle, pig and chicken breeding are presented in the following 

Table1: 

Table 1: Medium-large scale livestock units (Agricultural Bank of Greece, 1996). 

Category Number of Units Breeding animal heads 

Cattle 580 69,328 

Brood sows 448 105,793 

Chickens 361 20,042,050 

These units constitute the potential resource for biogas production under optimum conditions. It is 

estimated that AD of the manure produced by those units could result in a methane production 

almost 0,5 million m 3 /day and energy potential over of 400 kTOE (9). The volume of volatile solids, 

the estimated gas yield, in methane, and the energy potential per day are presented in the following 

Table 2: 

Table 2: Volume of volatile solids, estimated gas yield and energy potential per day 

of the medium-large scale livestock units in Greece. 

Category Volume of volatile 

solids per day (ton) 

Gas yield 

( 10 3 Nm 3 CH4) 

Energy Potential 

kTOE 

Cattle 291 195 155 

Brood sows 24 5 4 

Chickens 980 300 255 

Total 1,295 500 414 

3. Current treatment of livestock wastes 

In medium-large scale pig farms (>100 sows), the common practice of manure management is the 

collection in anaerobic lagoons after the collection mixing and mechanical separation. The discharged 

sludge is stored pit is considered as the main anaerobic treatment unit and the second as storage and 

currently as a treatment unit. Its operation acts as psychrophylic anaerobic digester open to the 

atmosphere (4). The main problem of this biological treatment system is the release of methane to 

the atmosphere contributing to global warming. As well as this, local nuisance problems have been 

created by the ammonia and other odour emissions during warm and dry weather periods. 

In cattle farms, solid manure is collected on impermeable platform where liquid from dung heap 

discharges in septic pool. 

In both cases and “vision of optimal conditions”, the disposal of liquid or solid manure is spread on 

farm land according to the “Codes of good agricultural practice for the protection of the waters from 

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nitrate pollution” (5). These guidelines define the timing of the disposal, for instance when the 

weather conditions are favourable for avoidance of run-off, or the retention time of slurry in 

anaerobic lagoons, even though the amounts of liquid manure for certain crops, etc. 

The poultry manure is collected dung heaps and is disposed on farm land after composting as it is a 

good fertilzer. The method and the compost process depends on the unit size, the bedding type and 

the objective of the breeding. Revenues are gained in the most poultry units. 

4. Historic perspective 

During the 1980s, few efforts for biogas applications were carried out in Greece. The Hellenic 

Center for Productivity (ELKEPA), a non-profit organization, had the main responsibility and the 

technical expertise of these efforts, usually in corporation with Agricultural University of Athens. 

The feedstock of the biogas applications was animal excrement and wastes from food processing 

industries such as olive oil mills. Some of them were demonstration projects that after enthusiasm 

and insurance of scientific support were abandoned and no longer operate. Examples of those 

projects are presented in Table 3: 

Table 3: Biogas demonstration projects out of commission today. 

Owner Place Feedstock Biogas 

production (m 3 /d) 

Digester 

Capacity (m 3 ) 

ELVIK ABEE Trikala Swine Manure 300 402 

Vrakas-Paras Korinthos Swine Manure ---- ---- 

Farm Corporation Kadanou Crete Olive oil mill waste 77 33 

EAS Naxou Naxos Milk factory wastes 330 500 

American Farm School (A.F.S.) – Biogas production through anaerobic treatment of farm waste. 

The AFS biogas plant is the oldest one in Greece. Initially the focus of its construction was directed 

to optimum biogas production. After a lot of technical and monitoring problems the emphasis shifted 

to the best environmental performance of the entire waste treatment and water reuse facility in which 

the biogas plant is one component (11). The anaerobic treatment of animal waste takes place in two 

anaerobic plug flow reactors in series. The liquid part goes through the anaerobic tanks and the solid 

part through a composting machine. 

The operational characteristics of the anaerobic treatment are summarized below: 

Liquid waste flow 30 m 3 /d 

Reactor temperature 37° C 

Total suspended solids TSS 22.3 kg/ m 3 

Volatile solids VS 17.5 kg/ m 3 

Biogas production 250 m 3 /d 

5. Constraints of AD for energy schemes in Greek livestock farming 

There are a lot of non technical barriers, which have affected negatively or have been continuing to 

steer public opinion away from the applicability of AD for energy exploitation in Greece. 

The reasons for low acceptability of biogas production in Greek livestock farming are presented in 

order of importance below. Awareness of them is necessary to overcome the current status in this 

type of RES in the near future and to plan operational energy schemes that could successfully 

promote AD applications in Greece 

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Non-acquaintance and structural problems 

The agricultural sector in Greece is dominated by small family owned enterprises which generally 

lack the resources and trained personnel to engage in long range planning or to implement 

technological developments. Thus, their capacity to institute efficiency improvements as well as 

waste treatment practices installing AD technologies is limited. 

Information transfer is a critical point of failure for farm owners, often lack the skills necessary to 

keep abreast of development in both the technological and policy areas. As a result, many 

opportunities to improve the performance of their livestock units are missed. 

Lack of credibility 

Past unsuccessful experience of biogas projects has led to the general idea that it is an unreliable 

technology, not suitable for use and sometimes no proven technology. However, the problems faced 

in most of those cases had nothing to do with digestion process or technology itself (digester, 

engine/generator) but with marginal aspects like: 

• Improper influent material or discontinuous feeding of the treatment process leading to 

discontinuous operation and varying thermal energy availability. 

• Lack of spare parts locally, crucial for the operation of a biogas plant (e.g. in American Farm 

School). 

• Inadequate planning, for instance, no study of sludge characteristics that later lead to blocked 

pipes or interruption of anaerobic process (e.g in the case of the large-scale piggery in Korinthos 

region). 

• Poor construction techniques, for instance resulting in substantial heat losses through the caps of 

digesters. 

• Inadequate resources (economic and human) resulting in problems in operation and inadequate 

maintenance programs (preventive cares/services not frequent enough). 

High risk of finance/investment: 

Biogas projects need heavy investment. Financing is therefore one of the key elements in order to 

promote biogas projects. The financing schemes must be adapted to this type of investments, with 

long pay-back periods, as the biogas projects will have long pay-back periods. The biogas plants are 

still very vulnerable from a commercial point of view, and the actual breakthrough is still uncertain. 

Failure is still a very real possibility even in countries with certain pioneering on biogas schemes such 

as Denmark and Germany (4). All of the these reasons and the national economic conditions, which 

discourage risk, do not favour any biogas scheme in Greek livestock farming. The obstacles for any 

investor could be summarized as follows: 

• high value of the discount rate (a promising reduction has been recently noticed) leading the net 

present value (NPV) and internal rate of return (IRR) on marginal levels for non-ambitious 

investments; 

• low electricity prices in Greece compared to other members of E.U., which make investments 

targeting energy savings unattractive; 

• lack of experience in strategy planning, investment realization and plant operation for all 

productive sectors (Local Authorities, Farm Associations and Livestock Unions) concerning 

biomass and especially biogas implementations; 

• lack of demonstration plants fully operational under Greek conditions. 

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In addition, the present restricted financial resources of the livestock farmers make them unable to 

invest for a project that can reach costs between 4,000 and 9,500 ECU per kW of electric power 

installed (13). All the above usually leads to medium/long pay-back periods, making those farmers 

who are interested hesitant on such investments. 

Weak environmental arguments 

Methane is an active greenhouse gas, with a Global Warming Potential (GWP) 23 times higher than 

that of CO2. Recovery techniques in manure management such as anaerobic digestion enable 

methane collection. The energy use of that eliminates completely the harmful effect of methane in the 

“global greenhouse effect”; the resulting CO2 emissions represent a much smaller contribution to the 

greenhouse effect than the one that the original methane would have had made. 

In terms of Kyoto protocol, the EU has made an commitment to reduce its greenhouse gases by 7% 

by 2010 in relation with 1990 emission levels. However, the Greek commitment is less strict: to limit 

greenhouse gases emissions increase to 25%. In 1995, the Greek agriculture contribution on methane 

release was 60% , but only 6% of that originated from manure management (7). On the other had, 

methane emissions from the enteric fermentation of ruminant livestock is the same with the European 

average (30%). 

The morphology of the Greek land is such that even when intensive agriculture is applied in some 

areas, the degree of intensification is much lower than the European dispersed and surrounded by 

vast quasi natural areas (hills, mountains, lakes, gulfs, etc.), that on one side are beneficial preserving 

biodiversity, on the other hand minimize problems causing insufficient treatment of livestock wastes. 

According to Nitrate Directive of the CEC 

91/676/EU, the Ministry for the Environment, 

Physical Planning & Public Works has 

determined four regions sensitive to nitrate 

concentration after measurements in surface and 

underground water. These regions – West and 

East Thessalia, Kopaida Plain, Argoliko Valley 

and Pinios Basin (Ilia) (Figure 1) – nitrate 

concentrations are higher than the limits set in 

the above Directive. Considering the existing 

strong agricultural activities (greenhouses, 

arable crops, etc.) and the low levels of livestock 

it would be safe to assume that the inorganic 

fertilizers as the main polluters there (6). 

Based on the above analysis, the argument of a 

biogas scheme for environmental benefits on 

“global change” and reduction of land and water 

pollution is not so strong currently in Greece. 

6. Perspectives of AD for energy schemes 

Figure 1: Distribution of sensitive nitrate areas in 

Greece 

(1) West & East Thessalia, 

(2) Kopaida Plain, 

(3) Argoliko Valley 

(4) Pinios Basin. 

The penetration of AD schemes in Greece is quite difficult due to the barriers outlined above. The 

existing means for financing the promotion of the investments on Renewable Energy Sources 

(Operational Programme for Energy-OPE/Ministry of Development, Law 2601/98/Ministry of 

Economics Affairs, European Programmes of Structural and Cohesion Funds) would be used for 

energy exploitation projects, including biogas. These means have been already exploited for different 

types of RES and are expected to continue and even intensify in the near future (2000-2006). The 

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recent incentives for the promotion of RES, which are applicable to future biogas schemes, could be 

summarized as follows: 

• The Law 2244/94 regulates the issues connected to the production of electrical power from 

renewable sources of energy and conventional fuel. It is under revision now to be replaced by 

another one, which is draft according to new environment as its coming from the E.U. direction 

96/92/EC for the deregulation of power market. 

• Development Law 2601/98, which replace the Development Law 1892/90, improving incentives 

for investments on RES. 

• Joint Ministerial Decision (Ministry for Development, Ministry for Environment, Physical 

Planning and Public Works and Ministry of Economic Affairs) for the promotion of RES and the 

reduction of emissions CO2, which has been in effect since 1997. 

• Joint Ministerial Decision for the management of the solid wastes and the planning of landfill sites. 

Energy exploitation is the latest priority. 

The European Union target to increase the average of bioenergy from 45 million TOE (1995) to 135 

million TOE (2010), as is described in the White Paper for the promotion of Renewable Energy 

Sources in Europe, must be also mentioned as a potential driving force the development of biogas 

schemes. 

In Europe the most commercial and technically mature anaerobic digestion systems are those 

designed for the digestion of animal manure, both on and off-farm as well as for co-digestion of 

animal manure and residues from slaughter houses, breweries and a wide range of other foodprocessing 

industries. In Greece, biogas applications will have more chance for success when there 

is a combination of by-products from cheese factories, oil olive mills, etc. with animal excrement. 

Livestock units that incorporate the whole chain of production, for instance slaughter, trade feeding 

stuffs, etc. would be potential investors for single biogas plants. The installation and operation of codigested 

biogas plants is a very promising alternative as has been shown from similar cases in 

Sweden, Denmark, Holland and Germany. However, the high investment cost, the Greek countryside 

morphology and the required strength cooperation of local productive sectors, makes this solution 

questionable for Greece for the time being. 

8. References 

1. Agricultural Bank of Greece. Directorate Livestock Production – Data from census in 

31/12/1995. 

2. Chatziathanassiou, A. and Panoutsou, K. (1998). Second intermediate year report of AD/Nett 

European Project, Co FAIR CT97 2083, CRES. 

3. EUROSTAT (1997). Agricultural Statistical Yearbook. 

4. Georgakakis, D. and Bicudo, J.R. (1999). “Anaerobic lagoon design and operation in swine 

facilities in Greece and in USA”. In the proceedings of the AgEnergy ’99 Conference, titled 

“Energy and Agriculture towards the Third Millennium”, Athens 2-5 June 1999, p. 374-381. 

5. Greek Democracy, Ministry of Agriculture (1994). “Codes of good agricultural practice for the 

protection of the waters from nitrate pollution”. Athens (in Greek). 

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6. Greek Democracy, Ministry for the Environment, Physical Planning & Public Works, 

Environmental Planning Directorate, Water department (1999). Network for the water 

protection of nitrate pollution. Athens (in Greek). 

7. Greek Democracy, Ministry for the Environment, Physical Planning & Public Works, 

Environmental Planning Directorate (1997). “2 nd National Communication to the United Nations 

Framework Convention on CLIMATE CHANGE. Review of the Greek National Action Plan for 

the Abatement of CO2 and other Greenhouse Gases Emissions” Athens. 

8. Holm-Nielsen, J.B. and Seadi, A.T. (1998). “Danish experience concerning the advantage of the 

integrated system of biogas production, environmental protection and agricultural production”. 

In the proceedings of the ALTENER Workshop titled “Energy Exploitation of Biogas - 

Possibilities and Applications”, Thessaloniki, November 1998, CRES. 

9. Loehr, R.C. (1984). Pollution control for Agriculture (2 nd Ed.). Academic Press Inc., New York, 

p. 72-81. 

10. Nanou-Gianarou, A., Andreadakis, A. and Lazarou, A. (1999). Pollution of the water resources 

in Greece due to agricultural activities. In the proceedings of the 6o International Conference 

titled “Environment Science and Technology”. Pithagorio Samou, 30/8-2/9/1999, p. 26-33 (in 

Greeks). 

11. Nikolaidis, D. (1998). “Biogas production from agro-industrial wastes. Thessalonica 

Agricultural and Industrial Institute”. In the proceedings of the ALTENER Workshop in 

Thessaloniki titled “Energy Exploitation of Biogas - Possibilities and Applications”, November 

1998, CRES. 

12. Plitas F. (1995). “The Greek Livestock in E.U.” Modernized Livestock, Greek Magazine, 

Vol.12, 1995, Athens, p. 4-15. 

13. U.K., ETSU (1997). Anaerobic Digestion of farm and food processing residues. Good practice 

guidelines. 

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Chatziathanassiou Artemios Center for Renewable Energy ... - Nifty

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