TECHNO-ECONOMIC AND ENVIRONMENTAL ASSESSMENT OF AGRICUL TURAL AND AGRO-INDUSTRIAL WASTE-TO-ENERGY POTENTIAL IN BRAZIL

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

TECHNO-ECONOMIC AND ENVIRONMENTAL ASSESSMENT OF AGRICULTURAL AND AGRO-INDUSTRIAL WASTE-TO-ENERGY POTENTIAL IN BRAZIL JOANA PORTUGAL-PEREIRA1*, RAFAEL SORIA1, RÉGIS RATHMANN1, ROBERTO SCHAEFFER1, ALEXANDRE SZKLO1 1 Energy Planning Program, COPPE, Universidade Federal do Rio de Janeiro Rio de Janeiro, RJ, Brazil *Corresponding author: [email protected], [email protected] +55-21-9847-93622. Keywords: Bioenergy potential; GIS mapping; Residues; Climate change mitigation, Brazil.

Abstract This study aims to quantify the technical, sustainable and economically feasible potentials of agricultural and agro-industrial residues to generate electricity via direct combustion in centralized power plants in Brazil. Further, the energy savings and greenhouse gas (GHG) reduction potential of replacing diesel-based electricity by bioenergy have been assessed. To this end, an integrated statistical, a GIS-based analysis and a life cycle assessment have been conducted. Results reveal that the technical and sustainable potential is nearly 141 TWh/yr, mainly concentrated in the South, Southeast, and Midwest regions. The residues of sugarcane, soybean and maize crops are the major feedstock for available bioenergy. On the other hand, the economic potential is far lower, accounting to 39 TWh/yr. The total GHG mitigation is nearly 28 million tCO2e and could reach 102 million tCO2e yearly, if the technical potential is considered. The gap between technical and economic potentials implies that constrains to bioenergy are not related to a lack of resources, and as such further policies should be implemented to foster the penetration of bioenergy in the electricity generation portfolio of Brazil. 1- INTRODUCTION The Brazilian power sector is on a knife-edge. Historically, the country has been a World leader on renewable energy, with the share of hydropower and bioelectricity making up approximately 85% of the country’s electricity generation portfolio in 2013 [1]. However, year after year, this contribution has been decreasing. On the one hand, on the demand side, in the last decade, the electricity consumption increased two-fold up to 516 TWh, partly due to the rising quality of life of an emerging middle-class. On the other hand, on the supply side, the expansion of hydropower plant projects has been limited due to socio-environmental conflicts [2][3]. Aggravating the situation, in the summer of 2013 the country faced a very serious drought, which reduced the water level in reservoirs and their generating capacity, highlighting the vulnerability of the country’s supply towards extreme weather events [4][5]. Reflecting the susceptibility of the sector, recently the Fitch Ratings financial agency reduced the Brazil’s trust level of investment fearful of pressures on the energy supply sector and its impacts on the economic sustainability [6]. Forecasts predict that electricity consumption will double from 2010 levels to 1100 TWh in 2035 [7]. Following a business-as-usual scenario, this growth will likely come from fossil fuel resources [8]. In recent years, the Brazilian government has announced aggressive investments to explore pre-salt oil and gas reserves and even unconventional natural gas

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

(shale and tight gas) aiming at fostering the resilience and diversity of the energy sector in general and the power supply sector in particular [9]. Paradoxically, increasing the share of fossil fuels in the electricity generation portfolio results in higher greenhouse gas (GHG) emissions, which indirectly intensify the vulnerability of hydropower systems. Thus, the country is currently trapped in a development vicious cycle. Recent attention has been put on bioelectricity, as a feasible alternative to turn this tendency into a virtuous cycle. It would simultaneously diversify energy sources, reduce fossil-fuel dependence, and tackle climate change. Although traditional, dedicated biomass has already a significant expression in the country’s power supply, particularly based on sugarcane bagasse thermal power plants, there is a vast potential from agricultural and agro-industrial residues which are currently not recovered. Instead of being left on the farmland and slowly decomposed, releasing harmful carbon dioxide and methane emissions, this valuable feedstock could be collected and processed to generate electricity via conventional thermochemical processes. Assessing the bioenergy potential is, therefore, essential to characterise feedstock both qualitatively and quantitatively and prospect the potential substitution of fossil fuels and the associated reduction in GHG emissions. A small number of studies can be found in the literature that touches this subject. At the national level, the technical potential for electricity generation from major agricultural crop residues and animal manure has been estimated [10][11]. In more detail, other assessments quantified the energy potentials of the main biomass resources in different regions of Brazil [12][13][14][15]. A common limitation of these studies is the reliance on crude assumptions and simple national statistics to quantify the potential of residue production, disregarding the economic and environmental limitations of residue collection and processing. Further previous studies are restricted to a specific area in the country or to a particular technology. Another downside is the lack of spatial attributes in the bioenergy potential estimation. As highlighted by [16], data about spatial distribution of biomass are needed to optimise industrial production chains with an efficient use of resources. Aiming at overcoming this gap, this study attempts to estimate the technical, sustainable and economic feasible potentials of agricultural and agro-industrial residues to generate electricity via direct combustion in centralised systems in Brazil. Further, it applies an integrated GISbased analysis to map residue availability and assesses how much bioenergy can replace fossil fuel resources and contribute to the reduction of GHG emissions. To this end, a statistical analysis has been conducted, followed by GIS mapping, which identifies optimal locations of bioenergy generation centres, under techno-economic and environmental constraints. Then, a life cycle approach has been adopted to quantify the non-renewable energy and GHG emission savings from replacing fossil-fuel-based electricity. This paper is structured as follows. Section 2 presents the integrated assessment applied in the study, including key theoretical principles about analytical quantification of bioenergy with a statistical based approach and GIS mapping, as well as assumptions applied in the environmental assessment. This is followed by Section 3, which discusses key results, lessons learnt and limitation of the study. Lastly, Section 4 outlines final remarks and implications of the study to policy making. 2- MATERIALS AND METHODS This study adopts a resource-based assessment that takes into account the main characteristics of biomass feedstock (section 2.1) to estimate the theoretical, environmental sustainable and techno-economic potentials to centralised electricity generation via direct combustion in isolated systems (section 2.2). Then, resources have been mapped with a GIS tool,

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

considering logistic and economic limitations in order to estimate an indicator of economic bioenergy potential in rural areas in Brazil, in terms of kWh/yr by km2 (section 2.3). Lastly, a life cycle assessment (LCA) has been conducted to evaluate the fossil fuel saving and GHG reduction of substituting fossil fuel-based marginal electricity by bioelectricity (section 2.4). 2.1 Feedstock characterisation Brazil, one of the World majors’ agricultural producers [17], generates significant biomass in processes arising from harvesting and processing of agricultural products such as rice, cotton, sugarcane, corn, soybeans, among others. Agricultural waste comes from the agricultural phase of the cultivation of certain species, while agro-industrial residues result from the industrial processing of biomass. Much of the agricultural crops produced in Brazil are covered in this work. Among the most important crops, in terms of the potential for use of residues, one can cite sugarcane, corn and soybeans [17]. Three different solid residues are produced from sugarcane processing: straw (during farming), and bagasse and filtercake (in the processing of ethanol). Currently, the main source of agro-electricity in Brazil is sugarcane bagasse (operating capacity of 9.4 GW), due to the large sugarcane production for ethanol, and consequent production of this residue in ethanol distilleries. It is noteworthy that recently other agricultural and industrial sugarcane residues have been widely studied for power generation. Brazil already has in operation a considerable number of biomass power plants beyond sugarcane bagasse, for example: black liquor (1.7 GW), wood residues (371 MW), elephant grass (32 MW), biogas (85 MW), palmist oil (4 MW), charcoal (35 MW) and rice husk (36 MW) [18]. Agricultural residues generated in the corn harvest, which are usually left in the field, are cobs, stalks and stems (culms) and stove. In this study, we considered only stove for the purpose of energy use, with calorific value (LHV), moisture content, RPR, availability of residues and capacity factor shown in Table 1. During the harvest of soybean, the same residues as the corn crop, which are stalks, stems, and leaves, commonly called soybean straw, are produced. The harvester reaps the grain in the field and discards these residues. During processing, products of higher value added, such as bran and soybean oil, are generated. Due to the waste and by-products of soybean for food and feed supplementation competition, only straw from the harvest of soybeans was considered as a residue. Table 1: Characterisation of evaluated residues.

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

Resource

Residue

LHVa) (MJ/kg)

Sugarcane

Straw Bagasse Filtercake Straw Husk Straw Straw Peels and tops Straw Shell and husk Husk Husk Shell Shell Fibres Empty fruit bunches Stems and leaves Straw Straw Stover Straw Straw Straw

Rice Soybean Cotton Cassava Peanut Coffee Coconut Palm oil

Bean Rye Barley Corn Sorghum Oat Wheat

RPRc)

18.62 19.81 19.81 17.22 17.08 20.09 20.10

Moisture contentb) (wdb/wdb%) 6.00 10.39 10.39 8.63 10.00 14.00 14.00

0.22 0.22 0.02 1.54 0.26 2.01 2.81

Availability of residues (wdb/wdb%)d) 65 10 10 100 30e) 100 100

20.09 20.10

14.00 14.00

1.11 2.52

100 100

18.98 19.39 21.50 20.09 15.54 15.62

7.99 10.75 8.10 14.00 7.99 7.99

0.56 0.59 0.84 0.42 0.06 0.12

70 50 90 90 80 80

15.17

12.00

0.20

100

14.33 20.08 19.68 18.67 19.06 19.58 19.54

9.00 8.20 8.81 5.65 7.04 12.32 11.24

1.45 1.61 1.48 1.53 1.90 1.54 1.55

30 100 100 100 100 100 100

Capacity factor (%)f) 50 50 50 50 50 40 25 50 33 33 58 100 100 100 100 100 50 25 25 50 25 25 33

a) LHV of residues has been estimated based on the High Heating Value proposed by [19][20][21][22][23], having as a reference the ultimate analysis of residues [24]. b) After [24]. c) Based on average removal rates proposed by [25] [26] [27][28][29][30] [31][32][33] [34] [35][36][37][38]. d) As for crop straws, except for sugarcane straw, an availability of 100% has been considered, admitting that straw is currently left on the farmland without any recovery. A factor of 65% has been assumed for sugarcane straw, taking into account the rate of farmland that is harvest mechanically with no open-air burning [39]. e) According to [40], 70% of rice husk is directly used in rice production units to generate process heat. Only 30% of total residues are available for bioelectricity generation. f) Considers the period in months per year during which raw materials are available. It is used as a proxy for the period in which the crop harvest occurs. Based on [41].

2.2 Statistical quantification of agricultural and agro-industrial residues Bioenergy potential is constrained by the theoretical capacity of biomass production, its environmental impacts, and techno-economic viability [16][17]. The theoretical capacity defines the maximum available bioenergy under biophysical and agro-ecological conditions that hold down the growth of crops and residues, such as temperature, solar radiation, rainfall, and soil properties. This theoretical potential is albeit limited by environmental constraints, as agricultural residues are important biome regulators. As described by [42], residues create a buffer that mitigate impacts of rain and wind erosion agents, and also protect soil from excessive sunlight and evaporation. Furthermore, several studies ([43][44]) suggest that agricultural residues contribute to nutrient recycling and organic matter fixation, and support microbial and macro invertebrate activity. The techno-economic viability, on the other hand, refers to the fraction of the environmental sustainable theoretical potential which is available under technological possibilities, logistic restrictions, and takes into account competition of

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

other non-energy uses of residues. Figure 1 lays out the schematic difference between the biomass potentials under evaluation in this study. · · · ·

Theoretical potential

Natural and climatic factors Physical restrictions Energy content of resources Method to quantify primary energy

Geographic potential

· Land use and other constraints of area availability.

Technical potential

· Technical limitations of technology · Systems performance

· Recovery factor of organic waste · Other sustainability factors

Sustainable potential Economic potential

· Cost projections by technology · Cost projections by fuel · Economical constraints

Market potential

· Energy demand · Competition between technologies, energy sources and regions. · Implications of policies and regulations · Investment capacity and response of investors

Figure 1: Theoretical, environmental sustainable and techno-economic potential of bioenergy generation. Source: Own elaboration, based on [16][45][46].

Considering the techno-economic and environmental constrain described above, this study follows a bottom-up statistical analysis to determine the environmentally friendly and technoeconomic feasible potential of bioenergy from agricultural and residues, as it follows: (

)

Where: RPj Ai Pi RPRj,i ESRj ARj LHVj 

Agricultural residue potential (GWh/year) Agricultural area of crop i (ha/year) Productivity of crop i (ton/ha) Residue of j to product i ratio (#) (see Table 1) Environmentally sustainable removal rate of residue j (%) Availability rate of residue j (%)(see Table 1) Low heating value of residue j (MJ/kg) (see Table 1) Conversion energy efficiency of standalone biomass Rankine power plant (18%LHV) [10]

Similarly, the potential of bioelectricity from agro-industrial residues has been evaluated as follows:

Where: RPk Ai Pi ARk LHVk 

Agro-industrial residue potential (GWh/year) Agricultural area of crop i (ha/year) Productivity of crop i (ton/ha) Availability rate of residue k (%)(see Table 1) Low heating value of residue k (MJ/kg) (see Table 1) Conversion energy efficiency of standalone biomass Rankine power plant (%)

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

Data regarding agricultural harvest area (Ai) and crop yields (Pi) have been collected in national database sets, available from the Brazilian Institute of Geography and Statistics, under the Municipal Agricultural Survey (PAM) for all Brazilian municipalities (5565 in total) in the baseline year 2010 [47]. The biophysical and agro-ecological limitations of residue generation, expressed as the ratio of residue generated per product (RPR i) derivate from the literature, as shown in Table 1. Nonetheless it should be underlined that residue yield varies locally with agricultural practices, climatic conditions and crop yields. As discussed in [48], empirical evidences suggest that residue yields increase up to a certain level and then remain constant after that. Thus, field surveys to measure residue production of crops under different climate conditions in several Brazilian states would reduce the uncertainty of the conducted assessment. The environmental sustainable rate (ESR) assumes that part of the residues needs to remain on the farmland to regulate the ecosystem. This factor should be evaluated locally based on specific crops, climate and soil conditions of agricultural land. However, to the authors’ knowledge, such data are not accessible regarding Brazilian conditions. Thus, in this study, a conservative average removal rate of 30% has been considered (after [25][27] [49][50][51][52][53]). The potential of residues is further restricted by competition with other non-energy uses and logistic constraints, as described by the availably rate (ARi), as presented in Table 1. The electrical conversion efficiency () of the standalone biomass fuelled Rankine power plant is assumed to be 18% [10]. This is rather a conservative assumption, but given the heterogeneous mix of residues with different physicochemical characteristics, the boiler efficient is expected to be lower than under ordinary conditions. 2.3 Spatial quantification Bioenergy from agriculture and agro-industry has significant technical and sustainable potentials in specific municipalities in Brazil. Although this knowledge is important, it is not enough to propose policies and projects that enable its energy recovery. Thus it is fundamental to quantify its economic and market potentials. This paper assessed the economic potential by identifying geographically the best suitable areas for the development of bioenergy power plants by applying a geographic information system (GIS) analysis. The most important criteria to identify the suitability of areas of the bioenergy power plants were the concentration of biomass residues by area and their proximity to power substations. For this purpose, the technical potential was allocated to the respective rural areas of municipalities according to the 2010 political division (5.565 municipalities). Shape files with this division were obtained from IBGE with datum SIRGAS 2000 [47]. Then, shape files were converted to the “GCS South American 1969” geographical coordinates by using the “South America Albers Equal Area Conic” projection. Rural areas of municipalities were calculated using GIS tools. An indicator of concentration of residual biomass was calculated for every municipality by dividing the technical potential (GWh/yr) by the respective area (km2). As a first approximation to estimate the economic potential, it is considered, in a conservative way, that only biomass residues spread within a circle of 50km radius are economically feasible to be used in centralized power plants close to power substations where they could be connected. Similar studies evaluating economic potential for renewable energy sources used similar approaches (40km) as main criteria to restrict the technical potential [54][55]. A shape file containing coordinates of power substations was obtained from the Brazilian electricity regulatory agency (ANEEL) [56]. Using GIS tools a buffer of 50 km

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

radius was drawn around each power substation. The area of each municipality within the circle was then calculated to estimate the economic bioenergy potential. 2.4 Environmental assessment In order to estimate the energy savings and avoided global environmental loads of substituting marginal electricity generated from diesel by the proposed residue-based bioelectricity system, a comparative consequential life cycle assessment (CLCA) has been conducted in compliance with the ISO 14040-44 guidelines [57]. The assessment has been developed by modelling input and output energy and mass streams with the software SimaPro 8.0.1® [58]. Each system is composed by sub-units, which are segregated in unitary processes. All processes are interconnected through input/output flows. Results were then exported to an Excel interface for further data analysis. Environmental impacts have been assessed based on depletion of fossil fuels and GHG emission indicators1. A product basis functional unit has been selected, as it allows an evaluation from a downstream angle. Thus, impacts have been assessed in terms of the total electricity generated in 2010. System boundaries of the bioelectricity generation system include both upstream (collection, transport, and mechanical pre-treatment of residues) and downstream processes (operation of the power plant to generate bioelectricity). Additionally, it includes the “Cradle-to-Gate cycle” of thermal power plant infrastructure construction, as well as the manufacture of agricultural machineries and equipment. The reference systems describe the baseline pathways substituted by the bioelectricity generation system. Thus, the collection of agricultural residues displaces the impacts of crop residues left on the field, mainly emissions of nitrous oxide (N2O) released by nitrifying and denitrifying microorganisms that convert the nitrogen of aboveground residues into N2O. Further the recovery of agro-industrial residues displaces disposal of waste in landfill and consequent fossil fuel resource consumption and methane emissions. Also, the bioelectricity generated is assumed to substitute marginal electricity generated by a generator engine powered by diesel, and avoided depletion of fossil fuel resources and corresponding GHG emissions. The life cycle inventory has been developed in line with IPCC guidelines [59] and based on secondary data sets of EcoInvent libraries [60] and tailored to reflect the specificities of bioelectricity generated in Brazil (e.g.: carbon and nitrogen content of fuels, collection distance from farmland to processing unit, energy conversion efficiency and capacity factor of the power plant, harvest machinery, etc.). The following paragraphs briefly describe the main assumptions considered to model the bioelectricity and reference systems. 2.4.1 Bioelectricity system The bioelectricity system comprises upstream and downstream processes. Upstream processes include collection of residues and transport from farmland to the power plant unit (50km distance, as discussed in section 2.3). Pre-treatment operations are also taken into account, 1

GWP is calculated as carbon dioxide equivalent (CO2e) by the following expression: CO2e = CO2+ 34∙CH4+ 298∙N2O, according to the GWP factors suggested by IPCC in its 5 th assessment report [61].

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

which include sun-drying, mechanical crunching and conditioning. Farming activities have not been assessed, as energy consumption and environmental loans were entirely allocated to crop products. This assumption admits that farmers only grow crops to collect main products, regardless of the agricultural residues. The inventory employed derived from EcoInvent libraries [60]. Upstream processes include the operation of the biomass power plant and emissions of methane and nitrous oxide from incomplete combustion of residues2. Emission factors were given by [59] and approximated to factors of generic primary solid biomass combustion. The energy required and environmental loans of infrastructure of power plant components (boiler, turbine and generator) have also been inventoried [60]. 2.4.2 Reference systems Agricultural residues left on the field As a baseline, this study assumes that agricultural residues are left on the field to reduce impacts of erosion agents and increase organic matter and nutrient levels of the soil. On the downside, these aboveground residues also contribute to N2O emissions. Their impacts are significantly lower than N2O emissions from inorganic and organic N-fertiliser application and open air burning practices. Nonetheless, they should be also quantified in accordance to IPCC Guidelines of National Greenhouse Gas Emissions [59]. The N2O emissions of crop residues are released directly or indirectly via leaching and runoff from land during nitrification and denitrification processes3. Direct emissions are calculated as a fraction of 1% of the N-content of crop residues [59]. Indirect emissions, on the other hand, are only relevant when runoff exceeds water holding capacity of the soil or when fields are irrigated. As local data are not available, a conservative approach has been adopted, assuming that leaching occurs in 30% of agricultural land in Brazil, as suggested by [59]. Indirect emissions are estimated assuming a fraction of 0.75% of the leached N-content of crop residues. Emissions derived from synthetic and organic N fertilisers, as well as N mineralisation associated with loss of soil organic matter resulting from management of soils, are not considered in the inventory, as these impacts are associated to the agricultural crop. Agro-industrial residues in landfill The reference pathway of agro-industrial residues assumes its disposal in landfills. The decomposition of these residues produces noteworthy amounts of methane via anaerobic degradation of organic matter. This inventory assumes that the decomposable and degradable organic carbon (50%) is totally converted into methane. 2

Biomass life cycle is assumed to be carbon neutral, i.e., carbon dioxide released from biomass combustion equals to the atmospheric carbon dioxide up taken during biomass growth. 3 Nitrifying microorganisms convert NH4+ to NO3- and realise N2O as a by-product. On the other hand, under anoxic conditions desnitrifiers convert nitrogen oxides (NO3-) into atmospheric N2 via N2O.

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

Diesel power plant The bioelectricity produced is assumed to displace the generation of diesel-based electricity in a conventional generator of 5W capacity with a conversion efficiency of 35% [62]. The inventory accounts for the direct impacts of the diesel combustion, as well as the indirect loans of upstream processes from oil extraction and diesel refining and infrastructure components [60]. Direct emissions from carbon dioxide were estimated based on the carbon content of diesel (78.3 wdb/wdb%), whereas methane and nitrous oxide emission factors derivate from default factors of IPCC [59]. Table 2 reveals the overall life cycle inventory assessment of the bioelectricity and reference systems in terms of non-renewable energy consumption and GHG emissions. Table 2: Life cycle inventory of bioelectricity and reference systems. Non-renewable energy consumption (kgoil eq/GWh) BIOELECTRICITY SYSTEM Upsteam - Collection - Transport - Pre-treatment - Infrastructure Downstream - Power plant op. - Infrastructure Total REFERENCE SYSTEMS - Agricultural Residues left on the field - Agro-industrial residues in landfill - Diesel power plant operation

CO2 (kg/GWh)

CH4 (kg/GWh)

N2O (kg/GWh)

GHG (kgCO2e/GWh)

2.98E+00 1.07E+00 1.84E+01 2.83E+00

8.48E+00 2.62E+00 6.26E+01 1.12E+01

1.36E-03 3.53E-03 1.47E-01 1.75E-02

3.02E-04 2.63E-04 2.71E-02 3.61E-04

8.62E+00 2.82E+00 7.57E+01 1.19E+01

0.00E+00 1.03E+00 2.63E+01

0.00E+00 3.87E+00 8.88E+01

5.40E+02 1.27E-02 5.40E+02

7.20E+01 2.01E-04 7.20E+01

3.98E+04 4.36E+00 3.99E+04

0.00E+00

0.00E+00

0.00E+00

2.55E-01

7.59E+01

4.09E-04

0.00E+00

2.87E+02

0.00E+00

9.75E+03

2.47E+05

7.62E+05

3.44E+01

6.18E+00

7.65E+05

3- RESULTS AND DISCUSSION 3.1 Technical and sustainable availability of bioenergy This sub-section presents the technical and sustainable potential of bioenergy, without considering economic limitations, which will be addressed in section 3.2. Figure 2 reveals the spatial distribution of the technical bioenergy potential of selected agricultural and agro-industrial residues in 2010. Overall, the technical bioenergy potential of bioenergy residues is nearly 141 TWh/yr, which is equivalent to 27% of electricity generated electricity in Brazil in 2010. This potential is mainly concentrated in the Southeast (33%), South (28%), and Midwest (27%), which host major agricultural areas, while North and Northeast regions have limited bioenergy potential. Nearly 88% of total potential derives from residues of sugarcane, soybean and maize crops, as these are major agricultural cash crops in Brazil.

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

Figure 2: Technical and sustainable bioenergy potential. 3.2 Economic feasible potential Figure 3 shows the areas in Brazil considered with economic potential to implement centralised bioenergy power plants within 50km from power substations of the national power grid network (see section 2.3). The overall economic potential of bioenergy in Brazil is estimated to be 39 TWh, which represents around 8% of total electricity consumption in 2010. Considering an average capacity factor of 50% (based on Table 1), a complete use of the estimated potential means an installed capacity of around 9 GW. Similarly to the technical potential, major opportunities to implement economic feasible bioenergy power plants are in the Midwest (22 TWh), North-East (9 TWh) and North (7 TWh) regions.

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

Figure 3: Estimation of economic bioenergy potential. Figure 4 makes a zoom over a selected area on Figure 3 with the objective of highlighting some of the Brazilian municipalities with high economic potential. As the results show, in the Midwest and South regions there are municipalities with more than 90 kWh/year/km2.

Figure 4: Economic bioenergy potential in some municipalities of the Midwest region. However, if this economic potential was concentrated in a few areas its deployment would be much easier. Instead, this amount of energy is spread within big areas in Brazil. This is precisely one of the barriers for increasing biomass residues use in the country. Nevertheless, some policies could be proposed to encourage cooperative schemes between agro producers in rural areas. Several authors point out the success of this kind of policies in Denmark [63][64], where networks of agro producers were organized in the form of cooperatives. This type of policy would be even more urgent in a larger country, such as Brazil, lowering transaction costs and allowing for each agro productive unit to supply its

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

biomass residues to a large, centralized power plant, taking advantages of scale and access to financing. Other measure to be considered is the creation of new grids to transport electricity produced in the countryside to the main transmission and distribution lines. In addition, considering that medium and small cities are close to some of the main residues identified in this study, advanced local grids with distributed generation from biomass could also be proposed. Actually, the economic and market potential of biomass residues to fuel small and medium power plants connected to distribution lines and/or local grids should also be evaluated in future works, with an approach similar to Miranda (2013) [65], or even including innovative technological options, such as mini and microgenerators based on Organic Rankine Cycle (ORC). The aim of the current study was to focus on centralized power systems. 3.3 Environmental benefits and energy savings Table 3 lays out the yearly fossil fuel resources and GHG emission savings of replacing diesel-based electricity by bioelectricity. Considering the technical potential of bioenergy, overall environmental loads of bioelectricity generation over a year are 5.63 mil tCO2e, which results in nearly 103 mil ton of avoided GHG emissions. Savings are mainly related to downstream processes, i.e., avoiding combustion of diesel to generate electricity. On the other hand, if considering the economic feasible availability, environmental gains are more moderated, being approximately 28 mil tCO2e. Table 3: GHG emissions of the bioenergy system and avoided impacts Bioelectricity system ((technical sustainable potential)

Bioelectricity system (economic potential)

Avoided impacts (technical sustainable potential)

Avoided impacts (economic potential)

(mil tCO2e/year) 0.01

(mil tCO2e/year) 0.00

(mil tCO2e/year) -0.21

(mil tCO2e/year) -0.06

Downstream processes

5.62

1.55

-102.21

-28.24

Total (cradle-to-gate)

5.63

1.56

-102.43

-28.30

Upstream processes

4- FINAL REMARKS This study sought to quantify the technical, sustainable and economically feasible potentials of agricultural and agro-industrial residues to generate electricity via direct combustion in centralized power plants in Brazil. Further, the energy savings and GHG reduction potential of replacing diesel-based electricity by bioenergy have been assessed. To this end, an integrated statistical, a GIS-based analysis, and a life cycle assessment have been conducted. Overall results reveal that technical and sustainable potential is nearly 141 TWh/yr, mainly concentrated in the South, Southeast, and Midwest regions. Residues of sugarcane, soybean and maize crops are the major feedstock for available bioenergy. On the other hand, the economic potential is far lower, totalling some 39 TWh/yr. This gap implies that constrains to bioenergy penetration in electricity generation portfolios are not related to a lack of resources, but rather owned to economic, logistical, regulatory and political barriers. In fact, agricultural residue resources are spread on the farmland after

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

harvesting activities with limited energy density per km2, which increases collection costs. Thus, a mix of measures could help boosting the use of residues in centralized power systems in Brazil. Firstly, the coordination of small and medium farmers into cooperatives, or even the implementation of ESCOs for investing in power generation facilities, would lower transaction costs. Secondly, investment costs could be lowered through fiscal incentives. Thirdly, connection costs could be reduced through the definition of obligations and control of market barriers from power utilities. Finally, regional and exclusive auctions for residues´ power generation plants could be implemented by the Brazilian government, in accordance to what has been done for other alternative energy sources in Brazil in the last decade. Thus, a fiscal incentive in the form of a Feed-in-Tariff (FIT) would encourage farmers to diversity their activities and include bioenergy in their business portfolio. Another alternative to finance the implementation of centralised biomass power plants could be through official development assistance given by developed country donors to support environmental project, as bioelectricity results in significant GHG reduction from replacing diesel-based electricity. The total GHG mitigation is nearly 28 tCO2e/yr and could reach 102 million tCO2e yearly, if the technical potential is considered. Further, supporting policies to foster centralized generation under a cooperative scheme would result in gains of economy of scale and improve the reliability of the feedstock supply. Also, state governments should reconsider the power distribution network, as several municipalities with high bioenergy technical potential do not have a neighbouring substation unit, which makes non-viable the implementation of a centralised biomass power plant. Despite the efforts to conduct an accurate analysis of bioenergy potential in Brazil, this study presents several limitations that should be revised in future work to enhance robustness of the findings: i. Residue/product ratio and residue removal ratio are site-specific and should be adjusted to Brazilian farming characteristics, rather than assumed based on theoretical values; ii. The availability of residues to bioenergy potential should be further investigated, as a significant amount of leftovers are already used in other economic activities; iii. The combustion of residues is assumed to take place in a common boiler, but physical characteristics of residues might interfere with the boiler efficiency. iv. The density of residues was uniformly considered in each municipality, but in reality residues are heterogeneously concentrated. Thus, further land use analyses should be conducted to specifically characterise the potential of each municipality. v. The economic distance to collect residues was considered to be 50km. Nonetheless, this distance is constrained by several logistic and infrastructure limitations, which should also be better examined. vi. The baseline of this study considered diesel-powered generators as the conventional power option to be replaced. This does not necessarily hold for the Brazilian national grid, where the marginal thermal power plant is better represented by natural gas plants, and the average grid factor is mostly affected by hydropower plants. Future studies should, thus, improve the analysis in order to review the baseline scenario. vii. This study is focused on centralized power options. This affected the choice of the power generation technology and the logistic restriction related to biomass collection. A further study could focus on remote and local generation options, based on other technologies such as ORC.

5th International Conference on Engineering for Waste and Biomass Valorisation - August 25-28, 2014 - Rio de Janeiro, Brazil

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