Emissions monitoring during coal waste wood co-combustion in an industrial steam boiler

Fuel 81 (2002) 547±554

www.fuel®rst.com

Emissions monitoring during coal waste wood co-combustion in an industrial steam boiler q G. Skodras a,b,c,*, P. Grammelis a,d, P. Samaras b, P. Vourliotis d, E. Kakaras a,d, G.P. Sakellaropoulos b,c a Centre for Solid Fuels Technology and Applications, Ptolemais, Greece Laboratory of Solid Fuels and Environment, Chemical Process Engineering Research Institute, Thessaloniki, Greece c Chemical Process Engineering Laboratory, Department of Chemical Enginering, Aristotle University of Thessaloniki, Thessaloniki, Greece d Laboratory of Steam Boilers and Thermal Plants, Mechanical Engineering Department, National Technical University of Athens, Athens, Greece b

Received 17 November 2000; revised 20 June 2001; accepted 11 July 2001; available online 11 October 2001

Abstract Co-combustion tests were performed in a 13.8 MWth industrial steam boiler, using Greek lignite from Ptolemais reserve, natural waste wood, MDF residues and power poles. Fuel blends were prepared by mixing single waste wood components with lignite in various concentrations. Oxygen concentration and emissions of CO, SO2 and NOx were continuously monitored, during the co-combustion tests. Gaseous and particulate samples were collected and analysed for heavy metals, dioxins and furans according to standard methods. The results showed that co-combustion is technically feasible provided that agglomeration problems could be confronted. Low emissions of toxic pollutants were obtained during the co-combustion tests, below the legislative limit values. The lowest values of dioxins and furans were observed during combustion of fuel blends containing MDF, possibly due to inhibition by some nitrogenous components in MDF. No direct correlation was found between emitted PCDD/F and metal compounds, especially copper. Among the measured metals in the ¯ue gases, zinc was the most prominent, while iron was mainly observed in the solid ash samples. q 2001 Elsevier Science Ltd. All rights reserved. Keywords: Co-combustion; Waste wood; Lignite; PCDD/F; Heavy metals

1. Introduction Pulverised coal is used today world-wide for energy production in thermal power stations. Because of the high CO2 emissions of solid fuels, renewable sources are actively considered for energy generation with reduced net green house gas emissions. Co-combustion of coals with biomass (wood and waste wood) is of considerable importance from the technical, economical and environmental point of view, with a number of bene®ts such as preservation of the diminishing sources of fossil fuels, alleviation of the growing problem of waste wood disposal, use of existing infrastructure, adoption to local biomass availability, and high ¯exibility of fuel mixtures. As a result, the intensive use of wood and waste wood for energy production is an aspect of today's national policy in several countries. * Corresponding author. Chemical Process Engineering Research Institute, Aristotle University of Thessaloniki, PO Box 1520, 540 06 Thessaloniki, Greece. Tel.: 130-31-996-225; fax: 130-31-996-168. E-mail address: [email protected] (G. Skodras). q Published ®rst on the web via Fuel®rst.comÐhttp://www.fuel®rst.com

However co-combustion of waste wood with coals entails some environmental risks due to metals and organic chemicals present in such wood. Waste wood contains a number of metals, which may be present in relatively high amounts. Co-combustion of waste wood and coal may result in metal emissions in the ¯ue gases and in the solid residues, depending upon metal volatility and combustion conditions (residence time, temperature, presence of Cl, addition of limestone) [1±3]. In addition to heavy metal emissions, waste wood combustion may result in emissions of organic toxic compounds, since it is usually impregnated (since the early 1950s) with various fungicides and insecticides, such as pentachlorophenol (PCP) or its sodium salts and lindane because of their fungicide and insecticide properties. In Germany, commercially available wood preservatives have a maximum content of 8.8% PCP, lindane (gammaHCH) or a mixture of the two [4]. Industrial grade PCP contains also various impurities, especially polychlorinated dibenzo-p-dioxins (PCDD) and dibenzo-furans (PCDF), known for their extremely toxic and carcinogenic action [5]. Industrial grade HCH is also contaminated with PCDD and

0016-2361/02/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved. PII: S 0016-236 1(01)00147-8

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PCDF [6]. Moreover, organic substances, and especially pentachlorophenol, are known precursors of PCDD/Fs formed at the post combustion zone of an incinerator [7], while some metals (Fe, Al and especially Cu) are active catalysts for the formation of chlorinated dioxins and furans. The objectives of this work were (a) to investigate the operation of an industrial scale combustor during cocombustion of waste wood and a low grade lignite, (b) to determine the CO, SO2, NO, PCDD/F and heavy metal emissions, and (c) to correlate gas emissions with the fuel blend properties. 2. Methodology Co-combustion tests were performed in an industrial 13.8 MWth boiler at PINDOS SA, an MDF producing industry located in north-western Greece. The boiler was a twocompartment combustion chamber, equipped with an economiser and a multi-cyclone. The ®rst compartment employed a moving grate, with seventeen series of stairs, each of them being alternatively constant or moving. The moving stoker system was able to operate with sawdust and wood chips and covered about 50±60% of the total thermal input. The fuel was supplied on the moving grate through a spinning wheel, a chain conveyor and a fuel damper. Two radio elements were used for regulating the fuel supply by detecting the fuel level in the intermediate reception hopper and on the moving grate respectively. The ¯ame positioned to cover about 1/3 to 1/2 of the moving grate surface, therefore, there was enough area available for fuel drying and ash removal, at the beginning and the end of the grate respectively. Primary air was distributed through four ducts below the moving grate and it was also used as a cooling medium of the stairs, while secondary air was fed just above the fuel supply. The second compartment had a multi-fuel burner employing sawdust, heavy oil, diesel or heavy oil in combination with saw dust. Raw gases from the second compartment passed through a multi-cyclone system, which led to the stack. A complete description of the boiler system as well as a schematic representation is given elsewhere [8]. The coal used in the co-combustion experiments was lignite from the Ptolemais seam, Greece. Medium Density Fibre (MDF) powder, which was a by-product of the company's production process, and wood poles used for power transmission, were used as a waste wood sources. Pine wood chips were used as a natural wood source. The proximate, ultimate and ash analyses of the various fuels are given in Tables 1 and 2. Elemental concentrations of metals in the raw fuel ashes are shown in Table 3. Co-combustion tests were performed by feeding the desired fuel blends in the ®rst compartment of the boiler. The fuel test matrix, employed for the evaluation of the co-®ring behaviour is shown in Table 4. Fuel feed and air ¯ow rate were regulated in order to maintain complete combustion conditions,

Table 1 Proximate and ultimate analysis of the raw fuels Parameter Proximate analysis (%wt) Moisture Volatiles Fixed carbon Combustibles Ash Ultimate analysis (%wt, dry basis) C H N S Oa Ash a

Lignite

Natural wood

Power poles

MDF

60.0 23.4 12.3 35.7 4.3

28.2 67.5 3.7 71.2 0.6

13.4 73.1 12.7 85.9 0.8

6.8 84.0 8.7 92.7 0.5

50.0 4.6 1.3 1.1 32.2 10.8

39.6 5.2 0.1 0.2 54.1 0.8

45.3 5.4 0.2 0.0 48.2 0.9

46.5 6.0 2.4 0.3 44.3 0.5

By subtraction.

a low CO content in the ¯ue gas stream and a ¯ame positioned to cover about 1/3 to 2/3 of the moving grate surface. A multi-component gas analyser (MULTOR 610) was used for monitoring continuously oxygen concentration, CO, SO2 and NO emissions, during the co-combustion tests. The measured values of emitted pollutants as well as the operating data of the boiler were recorded on a PC. Gaseous samples were collected from the ¯ue gas duct after the multi-cyclone unit and before the air draft fan. Samples for PCDD/F and heavy metals were obtained by the cooled probe method under isokinetic conditions, according to EPA methods 23 and 29 [9,10]. Solid residue samples from the bottom of the combustion chamber and from the bottom of the multi-cyclone unit were collected and analysed for unburned carbon and heavy metals. Analysis and quanti®cation of PCDD/F were performed in the extracts by using a mixed silica column and an alox column [11]. The PCDD/F results are based on the analysis Table 2 Ash chemical analysis (%wt) of the raw fuels Compound

Lignite

Natural wood

MDF

Power poles

SiO2 Al2O3 Fe2O3 MgO K2O Na2O CaO P2O5 SO3 Rest

32.08 9.30 7.18 6.67 0.36 0.00 40.00 0.64 2.06 1.71

14.45 2.71 1.61 8.00 10.04 0.17 51.30 2.82 ± 8.90

3.01 1.59 0.00 10.00 1.69 4.50 63.50 4.50 ± 11.21

13.43 2.50 4.50 5.60 1.75 0.74 57.45 0.88 ± 13.15

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549

Table 3 Elemental concentration of metals in the ash of raw fuels (mg/g, dry basis) Elements

Natural wood a

Al Ag As Ca V Cd K Sn Co Mn Mg Pd Na Ni Fe Cu Cr Zn a

Lignite

a

21 1 353 0.06 ^ 0.01 0.42 ^ 0.2 837 1 727 a 0.47 ^ 0.01 0.27 ^ 0.01 1401 1 102 a 1.8 ^ 0.5 0.18 ^ 0.01 52 ^ 2 148 1 183 a 0.48 ^ 0.02 104 ^ 3 0.88 ^ 0.02 148 ^ 35 1.82 ^ 0.1 0.6 ^ 0.05 5.23 ^ 0.1

120 1 5000 0.26 ^ 0.05 13 ^ 1 6450 1 24,000 a 20 ^ 1 2.9 ^ 0.1 492 ^ 10 8.8 ^ 1 5.2 ^ 0.1 18 ^ 1 2318 1 930 a 3.62 ^ 0.1 78 ^ 3 20.4 ^ 0.3 2446 1 1050 a 8.13 ^ 0.2 29 ^ 1 4.4 ^ 0.3

MDF

Power poles

0.03 1 27 0.05 ^ 0.01 2.14 ^ 0.5 603 1 1750 a 0.10 ^ 0.01 0.31 ^ 0.01 931 ^ 10 4.3 ^ 1 0.10 ^ 0.01 26 ^ 2 214 1 124 a 0.33 ^ 0.02 210 ^ 5 0.34 ^ 0.01 4.6 1 26a 2.06 ^ 0.1 0.18 ^ 0.01 13.2 ^ 0.1

20.5 ^ 2 0.10 ^ 0.01 5.60 ^ 0.5 1231 ^ 50 0.31 ^ 0.01 0.13 ^ 0.01 458 ^ 10 0.6 ^ 0.2 0.14 ^ 0.01 11.5 ^ 1 97 ^ 2 0.33 ^ 0.02 33 ^ 2 0.61 ^ 0.02 100 ^ 2 3.32 ^ 0.2 2.95 ^ 0.2 0.76 ^ 0.05

These elements were partially precipitated in the solution. Their concentrations were measured by EDS, in the electron microscope.

of all the 215 individual compounds of polychlorinated dioxins and furans. The obtained data are based on the concept of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity equivalents quantities, i.e. TEQ values [12]. This concept is based on de®ning toxicity equivalent factors (TEFs) for individual compounds by comparison with 2,3,7,8-TCDD, the most toxic chlorinated aromatic hydrocarbon. TEQ values represent then the sum amount of individual congeners multiplied by their TEFs. PCDD/F measurements were performed in a HRGC/HRMS system (HP5890/MAT 95 Finnigan). The recoveries of certain isomers ranged between 60 and 95%. An ICP-AES spectrophotometer was used for heavy metal analysis (ICP-AES Perkin Elmer). Prior to heavy metal analysis, ash samples were heated at 5408C for ®ve hours in order to remove the organic part of the sample. Subsequently, samples were acid treated in HCl and HNO3 in order for all metal elements to be dissolved into the acid solution. Analysis of unburned carbon in the ash samples was performed by a LECO CHN800 analyser.

3. Results and discussion 3.1. Boiler operation during the co-combustion tests No dif®culties were observed during the transportation of the fuel blend from the storage place to the boiler feed hopper. Experimental measurements were obtained after the boiler had reached steady state for each fuel blend fed. This required appropriate adjustment of the operating conditions, especially with regard to emission monitoring at the desired steam generation levels. During all tests, the thermal input was kept almost constant and equal to 3.9 MWth for the moving grate and 5.9 MWth for the burner. Based on the experimental measurements, the total ef®ciency of the boiler was 81.3% and the main heat losses were due to the high ¯ue gas temperature. The overall process ef®ciency is considered suf®cient for the moving grate and pulverised fuel ®ring technology. Under steady-state conditions, the temperatures at different points in the plant are presented in Fig. 1. No signi®cant

Table 4 Fuel test matrix of the co-combustion trials at the moving stoker Fuel blend

Symbol

(% weight)

(% thermal input)

Natural woodÐlignite Natural woodÐlignite Natural wood MDF MDFÐlignite Natural woodÐligniteÐpower poles Natural woodÐligniteÐMDF MDFÐligniteÐpower poles MDF

(a) (b) (c) (d) (e) (f) (g) (h) (i)

80/20 60/40 100 100 80/20 60/20/20 60/20/20 60/20/20 100

88.4/11.6 74.1/25.9 100 100 90.7/9.3 64.1/11.2/24.7 62.6/10.9/26.5 69.4/9.5/21.1 100

550

G. Skodras et al. / Fuel 81 (2002) 547±554

Fig. 1. Temperature variations during the co-combustion trials. T0, ambient temperature; T1, 1st compartment; T2, 2nd compartment; T3, ¯ue gas temperature.

variations were detected for the different test cases and only a small increase of the ®rst compartment temperature was observed, when MDF was used as base fuel. In all tests, the differential pressure drop between the ®rst compartment and the stack was between 3.2 and 4.8 mbar, ensuring constant ¯ue gas ¯ow. When MDF was burnt, either alone or in conjunction with other fuels, combustion evolution improved, constant operating conditions were achieved faster and the useful heat output increased. 3.2. Co-combustion ef®ciency and emissions Evaluation of the co-combustion behaviour was based on the emissions of CO, NO and SO2 and on the unburned fuel content of the ash samples. CO, NO and SO2 emissions measured at the stack, were corrected to (mg/Nm 3, dry, 6% O2), and are shown in Fig. 2 as a function of the excess air ratio. Results for the unburned fuel content in the ash samples collected from the ®rst compartment of the combustion chamber and the cyclone system are shown in Fig. 3.

Fig. 2. CO, SO2 and NO emissions during co-combustion tests. Fuel blend codes Table 4.

Fig. 3. Unburned fuel content of the ash samples. Fuel blend codes Table 4.

CO emissions were maintained at similar levels during the combustion of the different fuel blends (Fig. 2). Increase of lignite percentage in the fuel blend (b) up to 40%wt did not in¯uence seriously the emission of CO, while the unburned fuel content was decreased in the same test case (Fig. 3). This was attributed to the higher residence time required for the lignite combustion on the grate, due to its high moisture content. The use of MDF instead of natural wood in the fuel blend brought about a slight improvement of the combustion ef®ciency, resulting in relatively lower CO emission values (Fig. 2). Moreover, the comparison of the CO emission values and unburned fuel content for the blends (a) and (e) shows that the use of MDF instead of natural wood in the fuel blend brings about a slight improvement to the combustion ef®ciency. Similar behaviour was observed with the fuel blends (f)±(h), where MDF was used at the highest percentage of 60%wt. In all cases, NO emissions were dependent upon the operating conditions and were not affected by the nitrogen content of the raw fuel (Fig. 2). This observation is valid even for MDF, despite its high nitrogen content. The highest values of NO were observed in the fuel blends (c) and (g), where the excess air ratio was at its maximum. The lowest NO values were obtained for the fuel blends (a) and (f), following the trend of the excess air variation. Furthermore, low SO2 emissions were measured during the co-combustion tests. The highest SO2 value was observed during combustion of the mixture with the highest lignite content (b), due to the higher sulphur content of raw lignite. The total unburned carbon in the ash samples re¯ected the combustion conditions and in all cases it was rather low lower than 8%wt (Fig. 3). All cyclone samples presented higher unburned carbon content than the corresponding samples from the bottom of the combustion chamber, since carbon tends to concentrate on ¯y ash particles [13]. This is mainly attributed to the faster pyrolysis of the waste

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Fig. 4. I-TEQ values for the various fuel blends during the co-combustion tests. Fuel blend codes Table 4.

Fig. 5. PCDD/F emissions during lignite±waste wood co-combustion. Fuel blend codes Table 4.

wood particles that certainly affects their residence time in the combustion chamber. Total PCDD/F emissions, expressed as toxicity equivalent (TEQ) values [12] for all co-combustion tests are shown in Fig. 4. TEQ values, in almost all cases, were lower than the limit value of 100 pg/Nm 3, and ranged between 3 pg/ Nm 3 in the case of MDF/lignite 80/20, and 97 pg/Nm 3 for the combustion of 80/20 natural wood/lignite mixture. Separate analyses of PCDD/F in the quartz glass wool cartridge sample and in the XAD resin cartridge sample obtained during the combustion of pure wood, showed that PCDD/ F were mainly adsorbed on the surface of the soot particles, which were collected in the ®rst quartz wool cartridge. Only a small part of the total PCDD/F concentration, about 3%, was present in the gaseous form, and it was trapped in the second cartridge. A duplicate experiment of pure MDF combustion was performed under complete combustion conditions, and the measured TEQ values were close, about 55 and 72 pg/Nm 3, respectively. The data from the co-combustion of pure natural wood showed that there was no direct correlation between the TEQ values and the percentage of wood in the solid fuel. However, the lowest TEQ values were observed during cocombustion of lignite/MDF mixtures (3 pg/Nm 3) and pine wood/MDF/lignite (6 pg/Nm 3). It is considered that MDF contained such compounds as urea and formaldehyde, which could inhibit the formation of PCDD/F in the ¯ue gases [14,15]. There is evidence that the addition of some nitrogen compounds in the post combustion zone can effectively reduce the concentration of PCDD/F in the ¯ue gases, although the mechanism of this inhibition has not been completely resolved [16]. Furthermore, co-combustion of MDF/lignite mixture took place under complete combustion conditions as it is indicated by the CO concentration in the ¯ue gases. CO content in this case was about 180 mg/Nm 3, the lowest from all the measured experimental values.

The dioxin and furan content in the ¯ue gases from the combustion experiments is shown in Fig. 5. As shown in this ®gure, furan concentrations were higher than the corresponding dioxin concentrations, and the ratio of PCDD:PCDF ranged between 1:2 and 1:3. However, for the combustion of natural wood and the co-combustion of natural wood and lignite, dioxins prevailed over furans and the corresponding ratio values of PCDD:PCDF were about 1:0.5 to 1:1.5. It appears that wood combustion changed the distribution of PCDD/Fs; it is known that both the formation and the distribution of PCDD/Fs dependent both on burning conditions and waste composition [17]. In addition, as shown from the homologue patterns, Figs. 6 and 7, the lower chlorinated congeners prevailed over the higher chlorinated ones, in accordance with typical homologue patterns from combustion processes [17].

Fig. 6. Homologue pattern of dioxins for the co-combustion tests. Fuel blend codes Table 4.

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G. Skodras et al. / Fuel 81 (2002) 547±554

Fig. 7. Homologue pattern of furans for the co-combustion tests. Fuel blend codes Table 4.

Although unburned carbon in ash samples re¯ects the combustion conditions, no direct correlation was found between the PCDD/F emissions and the carbon content in ash samples. For example, the lowest unburned carbon content was measured in the ash sample obtained from the wood-lignite (60/40 w/w), with PCDD/F emissions of about 50 pg I-TEQ/Nm 3, while the lowest toxic release was observed for the co-combustion of MDF-lignite which gave the highest carbon content in the ash. Total metal emissions measured in the ¯ue gases during the coal-waste wood co-combustion experiments are shown in Fig. 8, where sample letters correspond to the fuel blends of Table 4. Total concentration values correspond to elemental contents in the gas phase and in the ¯y ash particles after the multi-cyclone system. Low concentrations, ,50 mg/Nm 3, were measured in the case of metals like

Fig. 8. Heavy metal emissions during lignite±waste wood co-combustion. Fuel blend codes Table 4.

Fig. 9. Metal contents in the combustion chamber ash. Fuel blend codes Table 4.

Sn, Pb, Cd, Co, Ni, Mn, Cr, V, and Ag, which in total were below the limit speci®ed for total metal emissions from waste incinerators (0.5 mg/m 3). However, increased concentrations were observed for zinc, where emissions reached up to 1.4 mgN/m 3. The highest emissions of zinc could be attributed to the high volatility of this element; hence zinc is usually found adsorbed on the surface of ®ne ¯y ash particles from incinerators, which pass through the cyclones [18]. The highest value of 1.4 mg/m 3 was observed during the co-combustion of natural wood and lignite, possibly due to the high content of zinc in pinewood (5.2 mg/g). From all metal elements, copper in the ¯ue gases deserves special attention, since it is assumed to catalyse the formation of PCDD/F [19]. Copper emissions in all the cocombustion tests varied from 58 to 147 mg/Nm 3. The lowest value was measured during combustion of MDF, and the highest one in combustion of the MDF/lignite/power poles mixture. However, no explicit relationship was found between PCDD/F emissions and copper content. Apparently the operating conditions of the moving stoker could mask any such correlation, since they are known to affect PCDD/F emissions [17]. The metal element content in the ash collected from the combustion chamber and from the multi-cyclone system is shown in Figs. 9 and 10, respectively. Both ash samples gave concentrations of the metal elements Sn, Zn, Pb, Cd, Co, Ni, Mn, Cr, V, and Cu, lower than 0.5 mg/g. The content of Cd, Cu, Ni, Pb and Zn in all the ash samples was lower than the legislative limits which are anticipated for the maximum content of these metals in sludge deduced from wastewater treatment plants, in order to be used in agricultural areas. Iron gave the highest concentration in both samples, reaching up to 30 mg/g in the combustion chamber in the case of natural wood±lignite±MDF mixture combustion, and up to 14 mg/g in the multi-cyclone ash. The lower

G. Skodras et al. / Fuel 81 (2002) 547±554

Fig. 10. Metal contents in the multi-cyclone ash. Fuel blend codes Table 4.

iron content in the latter case was explained by the lower volatility of this element, which is concentrated in the slug residue of a solid waste incinerator [18]. The high concentration of iron was attributed to the presence of this element in the raw fuels and especially in the lignite samples, which contained up to about 3.5 mg Fe/g. 3.3. Long time co-combustion performance Based on the above results, a six month demonstration phase was carried out on site, using an MDF/lignite/natural wood mixture in proportions of 60/20/20 (%weight). Power poles were not included in the optimum fuel blend mainly due to the increased operating and maintenance cost for shredding this material at the existing facility of PINDOS SA. The emissions of CO, SO2 and NO were recorded at standard intervals and their mean values corrected to (mg/ Nm 3, dry, 6% O2) were 249, 40 and 600, respectively. These are below the legislative limits, and they do not deviate signi®cantly from the emission values measured during the co-combustion tests with the various fuel blends. Hence, systematic co-combustion of waste woods should be feasible without the need for costly waste gas scrubbing. In addition, monitoring of the boiler operation, and inspection of the heat exchange surfaces and of the water tubes of the economiser did not show any signi®cant changes in ash deposition formation. Consequently, no additional maintenance costs of the mechanical equipment of the boiler should be need if burning of this fuel blend was chosen as a permanent solution for the installation. 4. Conclusions Co-combustion tests of lignite with waste wood can be effectively achieved in a moving grate. All waste wood blends are good fuels, with MDF residues resulting in a

553

small improvement of emissions and combustion ef®ciency, under the same operating conditions. In all cases, emissions of CO, NO and SO2 were lower than the legislative limits. PCDD/F emissions were also low, in most cases below the legislative limit value of 0.1 TEQ ng/Nm 3, with the lowest values were for the lignite±MDF dust mixture, possibly due to inhibition effects of the MDF nitrogenous components. Examination of PCDD/F homologue patterns revealed the predominance of the lower chlorinated compounds over the higher ones, similar to typical combustion pro®les. Characterisation of metal elements in the ¯ue gases and in the solid residues showed that metal element emissions were lower than these anticipated by the guidelines. Of all metals, zinc and iron were found in the highest concentrations. Zinc was mainly volatilised and found in the gas phase, while iron was mainly concentrated in the ash samples from the combustion chamber and the multi-cyclone system. The high iron content in the solid residues was attributed to the high concentration of this element in the raw materials, and especially in lignite. Finally, considering the above and the Greek energy policy's trend to promote the development of decentralised energy production units supplied with biomass and various solid waste types, it is concluded that waste wood cocombustion is a promising option for industrial and district heating boilers. This is particularly true for the wood processing industries, such as PINDOS SA. Further development of waste wood thermal recycling will be accelerated if solid waste management companies, that will collect and transform the waste wood into an easy to handle by the boiler operators' form, will be established.

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