Journal of Environmental Protection and Ecology 12, No 2, (2011) G. Perkoulidis a *, A. Karagiannidis a, N.

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1 Journal of Environmental Protection and Ecology 12, No 2, (211) Biomass Energy Recovery in Hellenic Wood Production Facilities Solid waste management G. Perkoulidis a *, A. Karagiannidis a, N. Philippopoulos b, A. Malamakis a a Laboratory of Heat Transfer and Environmental Engineering, Department of Mechanical Engineering, Aristotle University of Thessaloniki, Box 483, GR Thessaloniki, Greece b N. Philippopoulos SA, 1st km Neochorouda-Thessaloniki, Box 31, GR-57 8 Thessaloniki, Greece gperk@aix.meng.auth.gr Abstract. The continuous growth of global energy consumption raises an urgent problem that needs to be addressed. On the other side, the use of fossil fuels causes numerus environmental problems, such as atmospheric pollution, acidification and the emission of greenhouse gases. A very promising and reliable method for mitigating these problems is the development of cleaner and renewable energy sources and biomass utilisation emerges as a critical undertaking due to its potential availability, conversion efficiency and its ability to be produced and consumed on a CO 2 -neutral basis. On this basis, many industrial facilities that produce waste biomass or organic waste in Greece, both small- and medium-/large-scale, have moved to utilising these streams for energy production. This paper presents an inventory sample of such (mostly agro-) industrial units along with an analysis of the temporal evolution of installed capacity, together with disaggregation characteristics of the feedstock material as well as the production facility itself. Scope of this paper is to shed light upon already practiced but so far not well documented energy production from biomass and organic waste in Greece and to provide an insight of the energy recovery potential from contemporary biomass market trends. Keywords: biomass, energy recovery, Hellenic facilities. AIMS AND BACKGROUND The agro-industrial sector in Greece has been a vital part between agriculture and the market since the 6 s. The energy consumption on the sector has been affected by the previous energy crises and this has led to the search for means to exploit the energy content of their by-products. At that time, the turn to alternative energy sources was only oil-price driven. Today, given the current energy crisis a number of agro-industrial facilities turn, once again, to the utilisation of their by-products for energy production. The difference lies, now, to the fact that environmental issues and stricter legislation on greenhouse gas emissions have also risen. * For correspondence. 63

2 One of the principal limitations in the use of agro-industrial by-products for energy production is that their availability and moderate heating values led to smallscale and high-cost applications compared to fossil fuels (at a time when fossil fuel prices were relatively low). The reduced emissions of SO x and greenhouse gases, however, are in line with European and national legislation 1. Worldwide, the most extensively used technology for biomass power production is direct combustion 2,3, followed by some other options including co-firing, gasification and anaerobic digestion for high water content by-products. Co-firing refers to the practice of adding biomass as a complementary energy source in fossil-fuel fired boilers. The concept covers a range of technologies 4, including the direct mixture of the biomass with coal in the fuel handling section, the separate or combined loading of biomass and fossil-fuel into the boiler 5, as well as the prior gasification of the biomass for subsequent injection of the syngas into the boiler. Gasification is another technology with great future potential. Gasification can be classified according to the type of reactor used (bubbling or circulating fluidised bed, parallel or counter-current mobile bed), the operating pressure (atmospheric or pressurised), the type of gasifying agent (air, steam, mixture of air and steam, CO 2 ), and the system of cleansing the effluent gases (high temperature filtration, catalytic, etc.). This technological solution has yet to attain the maturity of the previous options, but introduces new opportunities, especially having in mind novel mobile gasification units for decentralised electricity production. Anaerobic digestion of biomass is a well-known biological process producing biogas and biofertiliser. A significant number of biogas plants have been built, mainly in Northern Europe, whereas now the concept is spreading all over the world (especially in Asia). Biogas plants treat various types of organic residues including sewage sludge, food industry residues and manure. Agricultural industries have mostly a specific, seasonal product, while other industries vary their production during the year. The amounts of organic residues generated may not be sufficient to make digestion cost-effective. However, the establishment of a centralised facility co-digesting a number of organic residues would ensure the viability of the process. Co-digestion of different types of organic by-products has been increasingly applied in order to improve plant profitability 6,7. In most cases biogas yields were improved due to positive synergistic effect of using co-substrate in co-digestion. The easier handling of mixed wastes, the use of common access facilities and the known effect of economy scale are some of the advantages of co-digestion 8. At the moment, biomass contributes only with a small percentage in the Hellenic electric energy production (79 GWh according to a 22 estimation), while it has a more prominent position in the heat production sector (mostly via wood combustion for household heating purposes) taking second place after lignite as a space heating source. Lately, there is a significant political promotion (through 64

3 financial incentives, e.g. tax breakages and public capital subsidies reaching 4%) towards utilisation of renewable energy sources 9. Renewable energy contributed, during 22, with 1396 ktoe to the total primary energy supply. It has been reported that approximately 273 plants (cotton gin factories, olive kernel factories, sawmills, wood-based panel factories, major furniture factories, rice straw mills) operated utilising organic by-products in various percentiles, without taking into consideration the biomass amounts that are utilised in-house. This paper hence focuses on the energetic utilisation of agro-industrial byproducts from a research campaign performed through a sample of 7 Hellenic agro-industrial facilities. RESULTS AND DISCUSSION THE AGRO-INDUSTRIAL SECTOR IN GREECE This study focuses on two main agro-industrial sectors in Greece, cotton-ginning facilities and wood processing industries. Another smaller, but highly developing sector under consideration is rice processing. The cotton-ginning sector has evolved rapidly during the 8 s due also to the subsidies on cotton production set by the Common Agriculture Policy that was on effect at that time. Currently, the cotton production shows significant decline as farmers tend to turn to more profitable crops like corn or cereals. The Hellenic cotton production timeline since the early 6 s is shown in Fig. 1. In 23, there were 38 cotton-ginning facilities in operation in Greece 9,1. The majority of them are owned by farmers associations, thus having a range of operational problems due to organisational inadequacies and lack of state-of-the-art-knowledge. cotton production in Greece (t) Fig. 1. Evolution of cotton production in Greece Wood processing industry is currently a highly developing sector in Greece, with these developments being a response to a mixture of emerging constraints and opportunities that have existed for a much longer time. Advanced machinery and technologies for more efficient wood use have existed in industrial countries for decades. However, their adoption in Greece was neglected first because the * 65

4 natural forests were viewed as infinite and untouchable resources and second, as control over timbering areas has been very loose 12. There are over 66 small- and medium-sized enterprises in the sector (including small, family-based furniture businesses), with only 59 of them producing reconstituted wood-based panels (MDF, particleboard, etc.), meaning that only those need energy in the form of steam or heated oil. Rice processing industry in Greece is a sector numbering only a handful of enterprises processing rice produced in the country (Fig. 2) or bagging imported rice products. Moreover, it should not be neglected that the olive and grape agro-industrial sectors are of major economic importance in Greece. These agro-industrial activities generate large amounts of by-products, which are totally unexploited and in some cases dangerous for the environment. During 2, Greece produced an annual yield of 377 kt of olive oil and 348 kt of must, corresponding to 2266 Mt of olive oil wastewater and 135 kt of wine-grape residue 12, whereas 18 Mt of non-hazardous slaughterhouse waste were also produced 12. rice production in Greece (t) Fig. 2. Evolution of rice production in Greece SAMPLED INVENTORY OF ENERGY RECOVERY FACILITIES This study has focused on a sample of 7 agro-industrial facilities in the Hellenic region. The data presented below were gathered through interviews with the manufacturer of each plant energy recovery module. In line with the background presented above, three main plant categories were included in the sample, namely cotton-ginning facilities, wood processing plants and a small number of rice processing factories. The evolution of the installed thermal capacity of all the plants in question is presented in Fig. 3. A steady increase in capacity can be observed from the early 7 s, while during the last decade the increase is steeper due not to the fact that more plants are equipped with energy recovery modules, but rather because higher capacity units are installed. This can be partly explained by the rise in the knowhow levels of local manufacturers after almost two decades of installations. 66

5 installed capacity (kw) Fig. 3. Evolution of installed thermal capacity of all examined energy recovery facilities (rectangles reflect on the cumulative capacity, while triangles illustrate annual marginal capacity variations (mostly positive, although occasionally stagnant or even slightly negative)) Regarding specifically wood processing plants, 35 (out of a total of 59 in Greece) were included in the examined sample. Most of these plants produce wood-based boards and therefore need great amounts of steam for their operation, while they produce significant amounts of wood chips or wood dust from their board sawing modules. The evolution of their installed capacity is shown in Fig. 4, where a prevailing rise during the last decade of the installed capacity can be observed. Out of the 35 sampled plants, only 21 of them (6%) are still operational in 28. The reason for the closure of the remaining 14 plants (4%) was mostly due to the age of their owners, or secondarily the fact that some of them (in total 2) were sold and moved abroad installed capacity (kw) Fig. 4. Evolution of installed thermal capacity of energy recovery facilities in wood processing plants (rectangles reflect on the cumulative capacity, while triangles illustrate annual marginal capacity variations (mostly positive, although occasionally stagnant or even slightly negative)) For the cotton-ginning sector, 28 out of a total of 38 plants operational in 23 were included in the sampled inventory. The first installation of an energy recovery module in such a plant took place at 1986 and a significant rise of the installed capacity took place during the 9 s (Fig. 5). The new Common Agriculture Policy implemented by the EU in 2 has however lead into a decrease of cotton quantities produced in Greece (Fig. 1) down to 1991 levels; therefore, a change in the cotton-ginning sector is expected in the coming years also as a result of pressures related to viability issues of the existing plants. 67

6 14 12 installed capacity (kw) Fig. 5. Evolution of installed capacity of energy recovery facilities in cotton-ginning facilities (rectangles reflect on the cumulative capacity, while triangles illustrate annual marginal capacity variations (mostly positive, although occasionally stagnant)) Concerning the technology used for the combustion of by-products, three main types of grates are used in the combustion chambers: fixed grate, underfed fixed grate and travelling-slope grate. The disaggregation of the used grate technologies for the wood-processing facilities is illustrated in Fig. 6, while it is noted that for all cotton-ginning facilities the travelling-slope grate is used. As far as the flue gas cleaning technologies used for this type of facilities are concerned, both wood processing plants and cotton-ginning facilities use multi-cyclones for dust removal, while only three plants in the inventory have bag-filters installed. It is worth mentioning that bag-filters were first introduced in 25 in a meat-powder incineration plant and have since been installed also in a rice-husk and another meat-powder incinerator. All plants were designed to cover 1% of the industry heat demand via their own by-products, while only four of them also import external by-products to partially cover their heat loads; the later comprise of two rice processing plants, a particle board producing factory, as well as even a monastery utilising waste wood for space heating. Fig. 6. Combustion chamber technology and respective installed capacity selection used for wood processing plants in Greece (the inner diagram shows the number of installed technologies (and their overall percentage), while the outer circle shows the respective installed capacity in kw) 68

7 CONCLUSIONS In this study a sampled inventory of selected agro-industrial and wood processing facilities, with a view to their energy recovery functions was compiled and its energy-related features analysed. The investigated agro-industrial facilities included primarily cotton-ginning plants, which showed similar characteristics both concerning combustion grate technology and flue gas cleaning options. Given that the investigated ones represent 73.6% of the total existing plants in Greece, a clear pattern is thus derived. Wood processing plants, on the other side, showed a wider disaggregation and divergence in their features, yielding three different combustion grate technology options. On a timeline basis, cotton-ginning energy-recovery plants reached a peak in their installed biowaste-to-energy capacity during the late 9 s, while due to the new Common Agriculture Policy implemented by the EU and the resulting consequences changes in cotton production, all new facilities have stopped installing energy recovery modules. On the other hand, wood processing facilities showed a rapid increasing trend in their corresponding biowaste-to-energy installed capacity over the last ten years, yielding a total of over 25% increase rate since Travelling-slope grates are lately been used as they are better coupled with larger capacities and economies of scale. Concluding, it should be noted that some of the issues addressed in this study constitute a slight grey area on renewable energy production in Greece, coupled to traditional practices but lately put under a broad new spectrum in view of recent developments in oil/energy markets and environmental considerations. They have therefore the potential to constitute local available best practices and support the further acceptance and understanding of bioenergy in Greece. It must be also pointed out that, apart from the plants studied and analysed in this paper, there are still some other small- to medium-scale agro-industrial facilities employing renewable energy recovery modules to cover their thermal energy needs. These include olive processing plants, breweries and slaughterhouses. There is therefore a certain clear need to study all these plants in depth and to assess their energy patterns, as they constitute areas of opportunity for the further promotion and dissemination of renewable energy from organic substrates. REFERENCES 1. H. M. Groscurth, A. Almeida, A. Bauen, F. B. Costa, J. Ericsson, J. Giegrich: Total Costs and Benefits of Biomass in Selected Regions of the European Union. Energy, 25, EPRI, 1997 (2). 2. R. L. Bain, R. P. Overend, K. R. Craig: Biomass-fired Power Generation. Fuel Processing Technology, 54, 1 (1998). 3. D. A. Tillman: Biomass Co-firing: The Technology, the Experience, the Combustion Consequences. Biomass and Bioenergy, 19, 365 (2). 4. K.Wieck-Hansen, P. Overgaard, O. Hede Larsen: Co-firing Coal and Straw in a 15 MW Power Boiler Experiences. Biomass and Bioenergy, 19, 395 (2). 69

8 5. A. Mshandete, A. Kivaisi, M. Rubindamayugi, B. Mattiasson: Anaerobic Batch Codigestion of Sisal Pulp and Fish Wastes. Bioresource Technology, 95, 19 (24). 6. L. Neves, R. Ribeiro, R. Oliveira, M. M. Alves: Enhancement of Methane Production from Barley Waste. Biomass and Bioenergy, 3 (6), 599 (26). 7. G. Martinez-Garcia, A.C. Johnson, R. T. Bachmann, C.J. Williams, A. Burgoyne, R.G. Edyvean: Two-stage Biological Treatment of Olive Mill Wastewater with Whey as Co-substrate. International Biodeterioration & Biodegradation, 59, 273 (27). 8. EUBIONET European Bioenergy Networks: Eurobionet Biomass Survey in Europe. Country Report of Greece, ESYE National Statistical Service of Greece: Assessed 3/7/ Ministry of Rural Development and Food: Agricultural Statistical Data. / gr/ en/agro_pol/3_en.htm. Assesed 3/7/ M. S. Fountoulakis, S. Drakopoulou, S. Terzakis, E. Georgaki, T. Manios: Potential for Methane Production from Typical Mediterranean Agro-industrial By-products. Biomass and Bioenergy, 32, 155 (28). 12. A. Pantokratoras: Management of Solid and Liquid Waste of Hellenic Slaughterhouses. Hellenic Ministry of Agricultural Development and Food, Final Report, 26. Received 12 March 29 Revised 5 May 29 61