IMPLEMENTATION OF A BIOMASS POWER PLANT ENVIRONMENT AND ECONOMIC SUSTAINABILITY

Transcription

1 IMPLEMENTATION OF A BIOMASS POWER PLANT ENVIRONMENT AND ECONOMIC SUSTAINABILITY By: Maria Guadalupe Saião Orientation: Prof. Tiago Domingos Eng João Caldeira Eng Tatiana Valada Abstract Lately Europe has witness a vigorous growth in the woody biomass market. Bulgaria, although having a considerable forest area, only now starts to be aware of the potential that this recourse can offer. With the entry into the European Union, Bulgaria is obliged to comply with the European aims, in particularly those related to renewable energy sources. Taking into consideration the experience in forestry and the Bulgarian government s interest in exploring the biomass potential, the company Mapa Internacional considers the installation of a biomass power station, a business opportunity. In this context, this paper has two main goals, quantify the biomass forest potential production in three supply radius and evaluate the costs associated with it. The biomass quantification results of the application of empirical equations to data described in yield tables, and subsequently the use of forestry models. To limit the results it was assumed two production scenarios, the Optimistic and the Conservative, described by the maximum and minimum production respectively In relation to the costs, it was considered the primary and secondary transport and milling. Throughout the paper, were also mentioned some environmental implications that such a project represents The results varies between 179 tons/yr (for the Conservative scenario and for a 50 km radius), and tons/yr (for the Optimistic scenario and in a 100km radius).its use has an associated cost that varies from 29 to 33 /ton. The lack of information on the forestry sector and the absence of bioenergy projects, limited the results accuracy. Keywords: Bulgaria, forestry biomass, biomass equations, production, environment, costs 1

2 Introduction The rise in oil prices has highlighted the increasing dependence of Europe in relation to imported energy. The urgency to take measures to develop the energy sector in Europe in a sustainable approach and to reduce energy dependence boosted the use of renewable energy sources. On one hand, the use of natural resources reduce significantly the need to import energy on the other hand it guarantees the security of supply (COM, 2005). Also, their use contributes to achieve environmental sustainability, in the energy sector. The energy produced from renewable sources, represents smaller environmental impacts, compared to the alternative use of fossil fuels, thus contributing to the mitigation of climate change (MEE, 2008). The three main sources, to achieve sustainable development of the energy sector are biomass, solar and wind power. Of all the sources named the biomass is notable for its variety of sources. According to Directive 2001/77/EC, biomass is defined as the biodegradable fraction of products and residues from agriculture (including vegetal and animal substances), forestry and related industries, as well as the biodegradable fraction of industrial and municipal waste. Then, it is not surprising that biomass represents one of the largest shares in renewable energy consumption in Europe. According to the European Commission in 2004, about 4% of total consumption of primary energy was guaranteed by biomass. This value indicates that the biomass has emerged, at the time as the most important renewable energy source in Europe, providing two thirds of the total energy produced by renewable (EEA, 2006a). With the recent entry in the European Community, Bulgaria undertakes to change their energy behavior, significantly increasing the use of renewable energy. It was then released by the Bulgarian Government a set of action plans intended to encourage use of renewable energy, which clearly shows the interest in energy policy change, depending less and less on imported fuels from Russia. Further proof of the urgent need to change the characteristics of the Bulgarian energy sector, took place at the beginning of 2009, when it was cut off the access to natural gas, the main source of household heating. Before this fact, and combining the vast experience in the forestry sector, the firm Mapa Internacional wants to install a biomass power station in Bulgaria. This power station will use forestry biomass. Since this project represents a high investment, it is essential to determine the feasibility of the project, not only in terms of amount of resource available for consumption, but also in the economic point of view. This paper aims to estimate the potential amount of biomass that Bulgarian forest can produce and also evaluate costs associated with their use. In the context, to quantify the amount of forest residues available for energy use, it was considered only the branches biomass that results from clearing the forests, in operations as thinning and primary and intermediate pruning s and also final cuts of the stand. The calculations were based on the assumption that all the branches biomass will be used for energy purposes, excluding then, for example, the industrial use. The aim is also to mention the main environmental impacts associated with the exploitation of the forest resource. 2

3 Forestry Biomass exploration chain Overall, we can assume that the chain of forest biomass for energy purposes consists of three separate actions (Figure 1). Forest Residues Harvest Method Soil Fertility Biomass collection Erosion Biodiversity Water Resources Vehicles circulation Storage Transport Fuel quality Fuel Characteristics Technology Carbon balance Installation dimension Power station Market penetration Figure 1 Aspects to be considered in a bioenergy project. Source: Adaptation from OECD/IEA (2007). 1. Collecting and transport of forestry residues Forest residues represent all the material that is left in the forest after the exploration of biomass, for commercial use, and are usually made up of branches, bark and leaves. The residues are scattered throughout the forest soil, so it is necessary to proceed to its accumulation - primary transport, removal or trimming. Then, knowing that one of the most important characteristic of biomass is its low density, it is necessary to include a crushing operation. This can occur in three places: in the settlement, in a storage area near the place where the wood was cut or a specific unit. The method of collection is the result of compromise between the specificities of the land and the inherent economic component (DGF, 2003). Environmentally it is necessary to consider that forest residues, have a varied number of functions: they act as a source of nutrients, regulate water resources, help to prevent soil erosion, and also function as habitat for different species. The collection of forest residues means a disturbance of the ecological status of forests. Given this, it is important to ensure that the collection of forest biomass does not increase the existing pressures. Although there is no general agreement, studies such as How much bioenergy can Europe produce without harming the environment?" reveals that to ensure minimization of impacts resulting from the use of biomass, only 70% of the material should be removed (EEA, 2006a). There are many studies indicating that the transfer of waste from the forest to the central production of bioenergy is the key activity in the chain of exploitation, which may contribute to 3

4 make a project economically unfeasible. Whether is used to produce heat, electricity or both, the project must be competitive, that is, the combustible material should be delivered at the station at the lowest possible cost. Minimizing the cost of biomass use is minimizing the costs associated with the transactions described. 2. Biomass power station The biomass characteristics directly influence the choice of conversion technology, due to its specificity in factors as the content of dry matter, size, shape and consistency. In fact, some features make biomass a good fuel such as, ease of drying, high calorific value, low ignition temperature, high content in volatile compounds, high burn rate and low activation energy. However, factors such as humidity, particle size, density and variety of materials may limit the efficiency of its combustion. This variability requires a wide variety of conversion technologies for bioenergy production. Particularly for forest biomass processes in industrial facilities, it is possible to use combustion, gasification or pyrolisys (Brás et al, 2006). Methodology The amount of forest residues was assessed by two complementary approaches, in a first analysis was estimated the potential amount of biomass in the forest Bulgarian, and then was added a spatial component, which aims to assess not only the amount of biomass in the area around the central, but also the constraints associated with the transport. Related to the transport, this work also intends to determine the costs associated with the material transfer from the forest to the power plant. 1. Quantitative analysis To determine the productive potential of the Bulgarian forests, the study used as background information, yield tables. These represent a basic tool in forest management, as they provide data on the likely production of stands over time, while also providing guidelines for the best way to conduct the stands. The dendometric data in the yield tables, more specifically the diameter at breast height and height, were used in biomass empirical equations. These equations, based on allometric relationships between biomass of trees (M) and its dimensions, height (H) and / or diameter (D) (measured at 1.3 meters above the ground), allow the calculation of biomass production per tree. In its simplest form (eg Equation 1), they depend on the diameter, but can also be a function of height or both parameters. M ( kg / tree ) a D( cm) b Equation 1 Simple allometric relation Source: Zianis,

5 The parameters a and b vary with species, stand age, site quality index, weather, etc. It appeared then that the estimate of biomass, according to these equations, depends largely on the data collected and its significance. This reflects the specificity of their application, that is, besides being specific for each species, depends also on where the sampling was done, so it is necessary to determine the region for which the equation is valid. In the absence of available equations to calculate the quantity of biomass in the Bulgarian forests, and unable to make field visits, it was used the equations used in the Czech Republic and Austria. In total, it was used 13 equations, of which 9 referred to the species of Pine and 4 species of Oak. Then, and since the biomass considered in this work comes from the thinning and final cuts of the settlements, it was applied forestry models. These models are usually defined through the operations and practices carried out during the revolution of settlement, being directly related to the production targets and the forms of exploring the product. For this paper it was used the Portuguese forestry models, adapted to the information available on the yield tables. For the species studied were considered 4 thinnings and final cut. It is also important to note that the production of biomass was only determined for the medium yield class. Finally, being the purpose of this paper the estimation of the forestry residues amount available for burning in a central, it became necessary to limit the results. Then it was considered two scenarios, the Optimist for which biomass production is maximal and the Conservative, for which the equation was chosen to represent the lower production of biomass. At the end, the total branches biomass, was multiplied by the number of years of exploitation of each species. Figure 2 presents the general outline of the methodology used for the biomass quantification. 5

6 Yield Tables Species Pinus nigra Yield Class Age tree number Before thinning After thinning Mean diameter (cm) Basal Area (m^2) Mean height (m) Total volum e Volume (m^3) Main volume Thinning volume I ,7 16,2 4, : : : : : : : : : : : M = f (DAP) M = f (H) M = f (DAP,H) Specie Yield Class Biomass (ton/tree) X nº of removed trees Pinus nigra I 3,2 0,7 2,2 1,7 1,4 2,6 1,4 0,1 0,1 : : Biomass quantity (ton/ha) Forestry Models Species Eq. Interventions 1 st thinning 2 nd thinning 3rd thinning 4 th thinning Final cut TOTAL Pinus nigra ,47 46,31 103,75 191,49 365,37 723, : : : : : : Optimistic Scenario = MAX (Total) Conservative Scenario = MIN (Total) Figure 2 Scheme of the methodology used to quantify biomass 2. Spatial analysis After the biomass quantification of each species considered, it was necessary to estimate the amount that is available in the region where the power plant will be implemented. For this purpose, it s important not only the forest occupation in the study area, but also the representativeness of each species considered. To spatially analyze the availability of biomass was used as a work tool Autocad, in which was introduced a map of Bulgaria that led to draw the boundary of the country, districts and administrative forest regions. Then it was necessary to determine the area for which will be assessed the contribution of biomass to the power plant. Thus, knowing that the distance between the point of collection and the power plant is a limiting factor in energy use of forest biomass, it was assumed three supply radius - 50km, 75km and 100km, around the potential for local implementation of the plant. The radius of supply were established, taking into account that, according to the opinion of the Bulgarian forestry agents, the amount of biomass available in the Bulgarian forest is insufficient for the project presented. For the different radius of supply were identified the regional forestry administrations covered.. 6

7 Then, and based on a Bulgarian forest distribution map was possible to design the forest areas in each one of the regions, determining its influence area in each scenario. With information about the area occupied by each forest region in each supply radius and the information about the proportion that each studied species occupies, it was possible to quantify the biomass available in the three scenarios. This calculation assumes that in each region forest species distribution is uniform. Finally, by multiplying the area occupied by each species in each radius of supply, by the amount of biomass produced in the two scenarios evaluated, it is possible to determine the amount of biomass that exists in the Bulgarian forests. 3. Economic Analysis The economic assessment of forest biomass is quite complex and depends on factors ranging from the very nature of the material collected to fluctuations in market demand for timber. In this paper it was chosen to determine only the costs associated with the exploitation biomass chain, leaving aside all the other variables. The total cost thus results from the sum of individual operations of transport primary, crushing and secondary transport. In the calculations made, it was assumed the estimates of Netto (2008), whereby the cost associated with the primary transport, when using the less efficient machinery, is 7.25 / ton. For the grinding, the same author considered that this operation amounted to a cost of 8.05 / ton. Given that in Bulgaria there is no market adapted to the specifications in exploitation of forest residues on a large scale, it was added a margin of 30% to the value estimated in an attempt to bring the costs of the Portuguese market, more experienced, to the Bulgarian market. For the secondary transport, Netto (2008) based on a survey of the Portuguese transportation companies, set an equation for calculating the cost of transport (Equation 2), taking into account the distance between the origin point and the final destination. Equation 2 Transportation cost as a distance (km) function Source: Netto, 2008 Calculating the costs associated with operations, primary transport, crushing and secondary transport, in the supply radius established, it appears that the secondary transport gains importance, as the distance between the source and destination increases. For the 50km radius the secondary transport represents 26% of the total cost, and in the 100km radius, 36%. Finally, to determine the cost of biomass in each scenario it was enough to multiply the amount of biomass with the total cost. Results As a result of the methodology applied, it was possible to determine the biomass production in the supply areas, for the scenarios studied (Table 1). It should be noted that the total estimated 7

8 quantity takes into account that 30% of forest residues should remain in the forest, to ensure the minimization of the environmental impacts. Whether for the optimistic scenario or for the conservative scenario, the results show that the relation between the distance and amount of biomass produced is greater when we move from the supply radius of 75km to 100km that when it s from the 50km to the 75km. Table 1 Total biomass quantity Scenario Total biomass (tons/yr) 50 km 75 km 100 km Conservative 178,86 404,22 743,10 Optimistic 1 161, , ,96 For the total cost of transporting primary, secondary and grinding, it was estimated that varied between 29 and 33 / ton, depending on the scenario and supply radius chosen Limitations During the developed study, and taking in consideration the purposed objectives, it was noted two limitations that are the leading cause of discrepancy between obtain values and reality: (1) quality of the base information, (2) scenarios and assumptions made. About the base information it must be mentioned the following limitations: The purpose of the yield tables is not the use of biomass as an energy resource, but as a product for the timber industry. So just the trees that have the ideal market characteristics are considered, leaving out trees that not having commercial value, may be used for energetic purposes. Unable to determine the source of the data in the table, its use can be completely unsuitable for the region where the project will be developed The tables present only data for 4 species of trees, and although representative of the Bulgarian forest, others species exists that have more or the same occupation. When using as a work tool Autocad, it is associated with all calculations an error of accuracy. It is also worth noting that the map used as a basis may be outdated, and the occupations nowadays can be very different as a result of fire episodes or expansions of urban centers, for example. With regard to the assumptions made, the variability between the results and reality can be caused by the following: The empirical equations used are adapted to a reality that is not Bulgarian. Despite allow the estimative of biomass for trees different than those for which they were adjusted, the calculation for different species in different growing conditions, directly affects the reliability of results. 8

9 For forestry models, and having no knowledge about the operating conditions in the Bulgarian forests, its application appears to be not very accurate. The production of biomass, resulting from thinning varies significantly depending on the year of thinning and the number of trees removed. Also, for the calculation of the areas occupied by each species, it was assumed that the forest distribution was uniform, which is hardly realistic. As regards the estimated costs associated with the use of biomass, the assumptions made represent the factor that introduces greater variability in the results. The chain of exploitation of forest residues on a large scale is not a Bulgarian reality. Currently the waste is removed from the forest by the nearby population, and is therefore very difficult to measure the cost of primary transport. Also there are no biomass crushing machines in operation, and therefore the assumed cost associated with this operation cannot transmit the Bulgarian situation. Finally, the equation used to determine the cost of secondary transport is adapted to the Portuguese reality, roads, medium distances, fuel costs, etc. Conclusions With this paper, and despite all the limitations mentioned, it was possible to estimate the total potential of biomass that can be produced in forestry operations, and was therefore fulfilled the intended objective. The results indicate that the estimated amount of waste is not sufficient to meet the power plan biomass consumption. According to the Portuguese experience, a central with the production capacity of 15MW, consumes tons of forest residues per year. It is therefore necessary to find other forms and sources of forest biomass, so that the studied project can turn feasible. Given that such a project requires large investments, it is extremely necessary to study the conditions in the surrounding forest, so that the design of the plant, the technology and plans to exploit the resource can be adequate to reality. Considering the viability of the investment, it is crucial to have accurate information about the availability of raw materials, in quantitative terms, their distribution, seasonal variability and characteristics. It is important to evaluate not only the productive potential of the forest, but also the exploitable potential. In the future it is essential to introduce in the availability analysis, limiting factors that can be conclusive to the exploitability of the biomass, not only in a quantitative but also in an economic approach. By this, I mean that it should be taken into account the limited accessibility to the resource, such as slope, presence or absence of road infrastructure, availability of appropriate equipment, among others. It should also be imposed factors that affects directly the economy of the project such as the distance between the forest and the final destination, the material humidity and contamination, the purchase price of forest material, in other words, it must be taken into account all the variables that affects the quantity and the price at which the biomass is delivered at the plant. 9

10 In conclusion besides the impossibility of measure the actual amount of biomass available for combustion in the central nor the costs associated with their use, this paper gives an idea of the path that must be traversed The work also shows a set of limitations, and the firm can now focus their efforts to fulfill the information gaps and get pointed conclusions about the viability of the project. In this work it was also possible to verify that projects such as biomass power plants represent an opportunity to revitalize rural economies, creating jobs and securing the population. They also develop the forestry sector and, if they are guaranteed good forestry practices, when resource exploitation, there are no environmental impacts of large magnitude. Whether we are given the possibility of depletion of oil reserves or not, whether or not there is consensus on the neutrality of biomass in terms of emissions, its use is certainly a step forward in reducing energy dependence of Bulgaria. References Brás, A. M., Miranda, F., Hipólito, L., & Dias, L. S. (2006). Biomassa e produção de energia. O Minho a Terra e o Homem, COM. (2005). Comunicação da Comissão das Comunidades Europeias (CCE). Plano de Acção Biomassa. Bruxelas. DGF. (2003). Príncipios de Boas Práticas Florestais. Lisboa: Direcção-Geral Florestas. EEA. (2006). How much bioenergy can Europe produce without harming the environment. Copenhaga: European Environment Agency: EEA Report nº 7/2006. MEE. (2008). National Long-Term Programme to Encourage the Use of Biomass for the Period Sofia: Ministry of Economy and Energy. Netto, C. P. (2008). Potencial da biomassa florestal residual para fins energéticos em três concelhos do distrito de Santatém. Lisboa: Universidade Nova de Lisboa Faculdade de Ciências e Tecnologia Departamento de Ciências e Engenharia do Ambiente. OECD/IEA. (2007). Bioenergy project development and biomass supply. IEA: Good practice guidelines. Paris, França: International Energy Agency (IEA). REHES. (Março de 2007). Renewable Energy for Heat Supply in Dwellings with Individual and Local Heating Systems. D6 - Report on the biomass and solar energy potential: Bulgaria, China, Romania, Turkey. Zianis, D. (2008). Predicting mean aboveground forest biomass and its associated variance. Forest Ecology and Management Vol. 256, pp