Biofuels, Solar and Wind as Renewable Energy Systems_Benefits and Risks Episode 1 Part 10 pot

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Jewell, (ed.), Energy, Agriculture and Waste Management. Ann Arbor Science Publishers, Ann Arbor, pp. 29–47. Zemmelink G. 1995. Allocation and Utilization of Resources at the Farm Level In: A Reseacrh Approach to Livestock Production from a Systems Perspective – Proceedings of the Sympo- sium “A farewell to Prof. Dick Zwart” – Dept. of Animal Production Systems – Wageningen Agricultural University, pp 35–48. Chapter 9 Sugarcane and Ethanol Production and Carbon Dioxide Balances Marcelo Dias De Oliveira Abstract Ethanol fuel has been considered lately an efficient option for reducing greenhouse gases emissions. Brazil has now more than 30 years of experience with large-scale ethanol production. With sugarcane as feedstock, Brazilian ethanol has some advantages in terms of energy and CO 2 balances. The use of bagasse for en- ergy generation contributes to lower greenhouse gases emissions. Although, when compared with gasoline, the use of sugarcane ethanol does imply in reduction of GHG emissions, Brazilian contribution to emission reductions could be much more significant, if more efforts were directed for reduction of Amazon deforestation. The trend however is to encourage ethanol production. Keywords Sugarcane ethanol · CO 2 mitigation · CO 2 balances · bagasse · Co-generation 9.1 Introduction When the oil crisis hit Brazilian economy, and raised concerns about national sovereignty in the mid-70’s, sugarcane industrialists were quick to perceive in the scenario an opportunity to avoid bankruptcy. After some ups and downs of the Brazilian ethanol program the same sector is taking advantage of another scenario, this time related to growing environmental concerns regarding global warming. Brazil now has jumped on the bandwagon of the environmentally friendly fuel al- ternative, and is experiencing a revival of the ethanol program, the Pr ´ o-alcool, first established in the mid 70’s. Government incentives and subsides established by the Pr ´ o-alcool program, let the country to experience a considerable increase of ethanol production and ethanol- fueled automobile passenger fleet. By 1984, 94.4% of the passenger cars in Brazil were fuelled by ethanol. Posterior decline in oil prices associated with increase of M.D. De Oliveira Avenida 10, 1260, Rio Claro - SP - Brazil, CEP 13500-450 e-mail: dias oliveira@msn.com D. Pimentel (ed.), Biofuels, Solar and Wind as Renewable Energy Systems, C  Springer Science+Business Media B.V. 2008 215 216 M.D. De Oliveira Brazilian domestic production and high prices of sugar contributed to an expressive reduction of ethanol production in the country. By 1999, ethanol-fueled cars fell to less of one percent of total sales (Rosa and Ribeiro, 1998). Current enthusiasm with Brazilian biofuels, particularly sugarcane ethanol, is motivated by increasing worldwide concerns with climate change. Government, so- ciety and scientists talk passionately about the benefits of a “green” energy source and possible Brazilian contributions for the reducing of greenhouse gases (GHG) emissions. The ethanol industry is quickly capitalizing the benefits of these cir- cumstances, and Brazilian government is clearly willing to encourage increases for ethanol production. The present study analyses the CO 2 balance for Brazilian sugarcane ethanol and its possible contributions for GHG mitigation. 9.2 The “Green” Promise Biofuels are frequently portrayed as “clean fuel” (Moreira and Goldemberg, 1999; Macedo, 1998) and considered to be carbon neutral, since CO 2 emitted through combustion of motor fuel is reabsorbed by growing more sugarcane rendering the balance practically zero (Rosa and Ribeiro, 1998). Numerous articles advocate for an increase in biofuels production and consumption as an environmentally friendly option (Macedo, 1998; Moreira and Goldemberg, 1999 and Farrel et al., 2006). Sugarcane ethanol is considered and efficient way of reducing CO 2 emissions of energy production. According to Rosa and Ribeiro (1998), the use of ethanol fuel can have a significant contribution to greenhouse gas mitigation. Moreira and Goldemberg (1999), consider the main attractiveness of the Brazilian ethanol pro- gram, the reduction of CO 2 emissions compared with fossil fuels, as a solution for industrialized countries to fulfill their commitments with the United Nations Framework Climate Change Convention (UNFCCC). Beeharry (2001), points out that since the net CO 2 released per unit of energy produced is significantly lower compared to fossil fuels, sugarcane bioenergy systems stand out as promising candi- dates for GHG mitigation. Feedstock for ethanol production, in this particular case, sugarcane, grows by transforming CO 2 from atmosphere and water into biomass, which is, as mentioned before the reason why such fuel is called carbon neu- tral. Nonetheless, fossil fuel emissions are always associated with any agricultural activity. 9.3 CO 2 Emissions of Sugarcane Ethanol It has been a popular misconception that bioenergy systems have no net CO 2 emis- sions (Beeharry, 2001). Considerable amounts of fossil fuel inputs are required for plant growth and transportation, as well as for ethanol distribution, therefore CO 2 emissions are present during the process of ethanol production. Fertilizers, herbi- 9 Sugarcane and Ethanol Production and Carbon Dioxide Balances 217 Table 9.1 Carbon Dioxide emissions from the agricultural phase of Brazilian sugarcane production Constituent per ha Quantity per ha CO 2 release per unit of constituent 4 CO 2 release Nitrogen 70.0 kg 1 3.14 per Kg 220.0kg Phosphorous (P 2 O 5 ) 23.0 kg 1 0.61 per Kg 14.0kg Potassium (K 2 O) 132.0 kg 1 0.44 per kg 58.1kg Lime 1500.0 kg 1 0.13 per kg 195.0kg Herbicides 0.5 kg 2 17.20 per kg 8.6kg Insecticides 3.0 kg 2 18.10 per kg 54.3kg Diesel fuel ␣ 350.0 L 3 3.08 per L 1078.0kg Total 1628.0kg 1 Grupo Cosan – Brasil. 2 Pimentel and Pimentel – 1996. 3 Based on Pimentel and Pimentel – 1996. 4 West and Marland (2002). ␣ values correspondent to oil consumption of all agricultural activities and transport of sugarcane to distilleries. cides and insecticides have net CO 2 emissions associated with their production, distribution and application. CO 2 emissions from agricultural inputs of sugarcane production are represented on Table 9.1. Sugarcane production also results in emissions of other GHG, namely methane and nitrous oxide. Based on Lima et al. (1999), CH 4 and N 2 O emissions from sugarcane correspond to 26.9 and 1.33 kg per hectare respectively. Such emissions correspond to, based on Schlesinger (1997), 672 kg and 399 kg respectively of CO 2 equivalent. As for its distribution, based on Shapouri et al. (2002), 0.44 GJ are required per m 3 of ethanol, assuming diesel fuel is the source of this energy, and based on West and Marland (2002) CO 2 emissions associated with ethanol distribution are of 227 kg. Therefore net CO 2 emissions from ethanol production is 2926 kg CO 2 /ha of sugarcane (Table 9.2). Theoretically, there are no GHG emissions associated with distillery operations. All the energy required comes from the burning of bagasse, which is a residue of the milled sugarcane. In fact the burning of bagasse generates more energy than the distillery requires, resulting in some surplus of energy. Conceptually CO 2 emissions associated with bagasse burning are not accounted for, since where sequestered Table 9.2 Carbon dioxide emissions from Brazilian ethanol production Process CO 2 equivalent emissions per ha Agriculture 1628 kg CH 4 672 kg N 2 O 399 kg Ethanol distribution 227 kg Total 2926 kg 218 M.D. De Oliveira during sugarcane growth and will be re-absorbed in the next season. The same rationale applies to the ethanol burning in mother vehicles. For accounting purposes a complete combustion is assumed in both cases. Based on an average production of 80 tons per ha which is representative of the State of S ˜ ao Paulo, (Braunbeck et al., 1999), and ethanol conversion efficiency of 80 L per ton of sugarcane processed (Moreira and Goldemberg, 1999); the amount of ethanol resulting from one ha or sugarcane plantations is 6.4 m 3 . Consequently for production of one m 3 of ethanol, GHG emissions account to 457kg of CO 2 eq production and distribution, this corresponds to approximately 19 kg of CO 2 per gigajoule (kg/GJ) of fuel. Comparative values of CO 2 emission of other fuel sources are indicated on Table 9.3. Estimating the potential for GHG reduction from the use of ethanol derived from sugarcane requires a comparison with the fossil fuel displaced. In Brazil the auto- mobile fleet has basically three fuel options, natural gas, ethanol and gasoline, the last option is actually a mixture of gasoline and ethanol. The proportion of each fuel varies slightly according to government decisions, currently is 75% gasoline and 25% ethanol. Natural gas running automobiles are not manufactured in Brazil, but automobiles can be converted to natural gas at a price ranging from US$ 1200 to US$ 2100. 1 Although conversion to natural gas continues to rise in Brazil stim- ulated by its fuel economy, currently such vehicles represent only about 5% of the automobile fleet. The main attention in this work will be devoted to the impacts of ethanol substitution for gasoline. In 2003, Brazil began to produce flex fuel cars, which can run with both gasoline and ethanol in any proportion using the same tank. In that year about 40 thousand of such automobiles were produced, corresponding to only 2.6% of the new cars. In 2006, flex fuel cars corresponded to almost 60% of the new cars with 1.25 million units (Anfavea, 2007). This augment is directly related with a strategy for increasing biofuel consumption in Brazil, where the consumer is stimulated to use ethanol as an environmental responsible option. The differences in price between ethanol and gasoline also contribute for the scenario. Presently in Brazil, ethanol is about 49% cheaper than gasoline, mostly due to heavier incidence of taxes over gasoline. The Table 9.3 Comparative emissions of different fuels Fuel CO 2 /GJ (kg) Sugarcane ethanol (Brazil) 19 Corn ethanol (USA) 56 ␣ Gasoline 78 ␤ Natural Gas 53 ␤ Coal 92 ␤ Diesel 80 ␤ ␣ Dias de Oliveira et al. (2005). ␤ West and Marland (2002). 1 Based on Dondero and Goldemberg (2005) and considering 1 US$= 2 reais 9 Sugarcane and Ethanol Production and Carbon Dioxide Balances 219 advantage of flex fueled cars is that owners can trade back and forth between ethanol and gasoline according to the prices at the pump. 9.4 Gasoline Versus Ethanol To estimate the effectiveness that ethanol fuel has on reducing GHG emissions for Brazilian conditions, a comparison is made considering the fuel economy of flex fuel automobiles when using ethanol or gasoline. As mentioned before the production and distribution of one m 3 of ethanol results in emissions of 457 kg of CO 2 eq. Assuming a kilometerage for Brazilian flex fu- elled cars of 11.78 km/L for gasoline and 8.92 km/L for ethanol. 2 A flex fuelled car using one m 3 of pure ethanol can run for 8920 km, to travel the same distance using gasoline as fuel 757 L are necessary. Given that gasoline in Brazil is actually sold as a mixture of 75% gasoline and 25% ethanol, such volume of gasohol corresponds to 568 L of gasoline and 189L of ethanol. According to West and Marland (2002), production, distribution and combustion of one m 3 of gasoline result in emissions of 2722 kg of CO 2 , therefore the 568 L of gasoline will result in 1546kg CO 2 .For the 189 L of ethanol, the amount of CO 2 emitted correspond to 86 kg, consequently total CO 2 emissions add up to 1632 kg. Hence ethanol option represents 1175 kg of CO 2 emissions avoided per m 3 produced. In the hypothesis of pure gasoline being used instead of gasohol, to substitute one m 3 of ethanol used, approximately 673 L of gasoline are required, resulting in total emissions of 1832 Kg, that is, 1375 Kg CO 2 more than the ethanol being replaced. 9.5 Bagasse as a Source of Energy The bagasse, is the residue of sugarcane after the same is milled. It has approxi- mately 50% humidity and results in amounts of 280 kg/t of sugarcane (Beeharry, 2001). The burning of bagasse provides heat for boilers that generate steam and produce the energy required for distillery operations. Since the energy generated surpass distillery necessities, this surplus of electricity has potential for being exported, which is usually known as cogeneration, and according to Beeharry (1996), of- fers the opportunity to increase the value added while diversifying revenue sources for distilleries. According to Rosa and Ribeiro (1998), the utilization of sugar-cane bagasse for electricity generation may become the great technological breakthrough for Pr ´ o- ´ alcool in the context of sustained economic development while conserving the environment. They point out that the period of harvest of the sugar cane corre- sponds to the “dry period” in the Brazilian hydroelectric system, thus making the 2 Average values based on three of the most sold cars in Brazil, Volkswagen Gol, Fiat Palio, and Celta-Chevrolet, according to Paulo Campo Grande - Quatro Rodas. 220 M.D. De Oliveira use of bagasse in the area particularly attractive for complementing hydroelectricity generation. Brazilian distilleries generate an average surplus of 1.54 GJ (428 kWh) per ha or sugarcane processed (Dias de Oliveira, 2005). This corresponds to boilers producing steam operating at pressures of 20 bar generating small amounts of electricity (15–20kWh/ton of cane) enough for the needs of the unit (Moreira and Goldemberg, 1999). According to Beeharry (1996), advanced technologies could result in the genera- tion of 0.72 GJ (200 kWh) per ton of sugarcane milled. Such scenario would result in a value of energy surplus per ha or sugarcane of approximately 54 GJ (15000 kWh) or 8.43 GJ (2342 kWh) per m 3 of ethanol. Intermediate values indicated by Beeharry (1996), result in the generation of 0.45 GJ (125 kWh) of electricity per ton of sug- arcane milled, representing a surplus of 32.4 GJ (9000 kWh) per ha of sugarcane or 5.06 GJ (1406 kWh), per m 3 of ethanol. According to personal communication in a visit to the Center for Sugarcane Technology (CTC) – Piracicaba, boilers operating with pressures of 20 bars are so far the standard in Brazilian operating distilleries, with new plants being equipped with boilers that work at pressures of 60 bars, and are capable of generating a surplus of 0.14 GJ (40 kWh) of energy per ton of sugarcane milled. Still according to CTC, advanced technologies are yet economically unfeasible. To better illustrate the impacts that the conditions mentioned above would have in terms of CO 2 emissions, a comparison will be made with current Brazilian sys- tem of electricity generation. According to Brazilian National Agency of Electricity Energy (ANEEL), electricity generation in Brazil comes from the sources indicated on Table 9.4. With the dominance of hydroelectricity generation, Brazilian electricity matrix is responsible for relatively low CO 2 emissions per kWh of electricity produced (kWh el ). Compared with other sources, hydroelectricity has low carbon dioxide in- tensity (Krauter and Ruthers, 2004; Weisser, 2007; van de Vate, 1997). An important point though, made by Rosa and Schaeffer (1995) and Fearnside (2002), is that emissions from hydroelectric dams can be much higher than usually attributed for this source, mostly owning to methane emissions resulting from anaerobic decom- position of organic matter of the inundated areas in hydroelectric reservoirs. Considering Brazilian electric energy matrix and based on West and Marland (2002), Krauter and Ruthers (2004), and van de Vate (1997), each kWh el generated Table 9.4 Brazilian electricity energy matrix Source Percentage Hydroelectricity 80.23 Petroleum 4.54 Gas 11.42 Coal 1.47 Nuclear 2.09 Wind 0.25 Biomass not included. 9 Sugarcane and Ethanol Production and Carbon Dioxide Balances 221 Table 9.5 Estimated avoided emissions resulted from the use of ethanol as fuel instead of gasoline, and the surplus of electricity generated by distilleries ∗ Scenario Avoided emissions (kg) kWh/ton (GJ/ton) Avoided emissions (kg) per ha use of ethanol fuel Avoided emissions (kg) per ha surplus electricity Total Current 20 7520 59 7579 60 bars boilers ∼ 53 7520 445 7965 Intermediate 125 7520 1251 8771 Advanced 200 7520 2085 9605 ∗ Values calculated do not account for energy losses associated with electricity transmission in Brazil corresponds to net CO 2 emissions of approximately 139 grams, compared with the to 660 g per kWh el of US calculated by West and Marland (2002) or the 530 kg/kWh el and 439 Kg/kWh el of Germany and Japan respectively, as calculated by Krauter and Ruthers (2004). Consequently the surplus of electricity per ha of sugarcane is responsible for 59 kg of avoided CO 2 emissions per ha of sugarcane or 9 kg per m 3 of ethanol produced. With current Brazilian ethanol production of 16 million m 3 , total avoided CO 2 emissions due to electricity generation correspond to 144,000 tons of CO 2 kg/year. In the hypothesis that advanced technologies usually referred to as biomass inte- grated gasifier/gas turbine (BIG/GT) were the standard in Brazilian distilleries, the amount of CO 2 emissions avoided per ha of sugarcane would be of approximately 2085 kg or 326kg per m 3 of ethanol. Intermediate technologies would represent avoided emissions of 1251 kg of CO 2 per ha or 195 kg CO 2 per m 3 of ethanol. Nevertheless, as mentioned before, advanced technologies are not yet economically feasible. Considering differences in emissions from use of ethanol and gasoline, and the potential electricity generation of distilleries, avoided emissions for the possible scenarios of ethanol production in Brazil are summarized on Table 9.5. The results above indicated that consumption of ethanol, produced with current practices in Brazil, reduces CO 2 atmospheric emissions by 1184 kg/m 3 , when com- pared with gasoline use. Cardenas (1993), cited by Weir (1998), reports reduction in CO 2 emission of 1594 kg/m 3 of ethanol used in Argentina. According to Beeharry (2001), the use not only of the bagasse, but also sugarcane tops and leaves can contribute to distilleries potential for electricity exportation; such option however, would imply the elimination of pre-harvest burning and the use of cane residues that would otherwise be left on the soil, contributing to reduce soil erosion. 9.6 Pre-Harvest Burning of Sugarcane and Mechanical Harvest One aspect very criticized of sugarcane production is its pre-harvest burning, which has a series of negative impacts. The practice is adopted in order to facilitate the manual cut of the sugarcane. According to Kicrkoff (1991), pre-harvest burning is [...]... Bagasse use technology CO2 avoided option 1 CO2 avoided option 2 CO2 avoided option 3 CO2 avoided option 4 Current 60 bars boilers Intermediate Advanced 7579 (11 84) 7965 (12 45) 87 71 (13 70) 9605 (15 01) 6939 (10 84) 7325 (11 45) 813 1 (12 70) 8965 (14 01) 66 81 (10 44) 7066 (11 04) 7872 (12 30) 8706 (13 60) 7320 (11 44) 7706 (12 04) 8 512 (13 30) 9346 (14 60) Values in parenthesis represent avoided emissions per m3 and. .. (19 97) Spatial and temporal water quality variability in the Piracicaba river basin, Brazil Journal of the American Water Resources Association, 33, 11 17 11 23 Beeharry, R.P (19 96) Extended sugarcane biomass utilisation for exportable electricity production in Mauritius Biomass and Bioenergy, 11 , 4 41 449 Beeharry, R.P (20 01) Carbon balance of sugarcane bioenergy systems Biomass and bioenergy, 20, 3 61 370... Distribution 0.8 NEV with co-product energy 0.7 f(NEV) / f(avg) 0.6 Sigma: 1. 78 x 10 +4 Btu/Gal 1 sigma = 68% Sigma: 1. 89 x 10 +4 Btu/Gal 0.5 0.4 0.3 0.2 ± 2 sigma = 95% 0 .1 0.0 –70,000 –50,000 –30,000 10 ,000 10 ,000 30,000 50,000 70,000 Co-product Energy Credit NEV (Btu/Gal) Fig 10 .1 Corn to Ethanol Fuel Cycle Net Energy Value (NEV) with and without the co-product energy (Dias De Oliveira et al., 2005; EBAMM,... Stages and Templates The BFCM structures each BFC analysis based on three main analysis stages: 1 Infrastructure (Template 1 given in Table 10 .1) – multi-user services/facilities: 70 Sub-activities (59 distinctive + 11 onsite waste management covering 4 waste steam types) 234 T Gangwer Table 10 .1 Template 1 Infrastructure Stage (j = 1) Phase Sub-phase Activity: sub-activity k Manufacture Equipment Fabricate:... handling facility, Farms Onsite: Waste Management3 Wastewater, Non-aqueous liquids, Solids, Air Emissions includes Maintenance, Repair, Equipment/ Facility Decommissioning Non-aqueous liquids, Solids, Air Emissions 1 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 11 12 12 13 13 13 10 Biomass Fuel Cycle Boundaries and Parameters 235 2 Agriculture (Template 2 given in Table 10 .2) – biomass farm activities/facilities:... Fertilizer Lime Herbicide Insecticide 1 1 1 1 1 1 1 Irrigation system & water Installation Operations/fuel Water Pre-application treatment Maintenance/Repair/Removal 1 1 1 Planting Pre-planting Seed Application Tilling 1 1 1 Field Additives: Operations/fuel Onsite storage Fertilizer application Line application Herbicide application Insecticide application 1 1 1 1 1 Harvest Crop and Silage Processing Operations/fuel... Maintenance/Repair Transport of chemicals to Plant Process water treatment Co-generation Waste dispositioning 1 1 1 1 1 1 Operations/fuel Operations/fuel Maintenance/Repair Waste dispositioning 2 2 2 2 Onsite: Waste Management1 Fuel Handling Facility Transport Fuel Blending Facility Wastes 1 Fuel Feed Stock Onsite: Waste Management1 Wastewater, Non-aqueous liquids, Solids, Air Emissions a module of new BFC process/practice... facilitates modeling and analysis of scenarios involving diverse configurations (e.g., stand alone biomass cycles, crop rotation combined BFC’s), agricultural variations (e.g., fertilization versus crop 10 Biomass Fuel Cycle Boundaries and Parameters 233 Normal Distribution Presentation of NEV Published Data Average: 1. 19 x 10 +4 Btu/Gal Average: –4.40 x 10 +3 Btu/Gal 1. 0 NEV without co-product energy 0.9 Normal... (19 99) Prospects for green cane harvesting and cane residue use in Brazil Biomass and Bioenergy, 17 , 495–506 Cancado, J.E.D (2003) A poluicao atmosf´ rica e sua relacao com a sa´ de humana na regi˜ o ¸˜ e ¸˜ u a canavieira de Piracicaba – SP Cardenas, G.J (19 93) Ethanol from bagasse as fuel, contribution to lowering of CO2 IngenieriaQuimica, 25, 11 3 11 6 Cerri, C.E.P., Sparovek, G., Bernoux, M., Easterling,... greenhouse gas reduction by photovoltaic solar energy Renewable Energy, 29, 345–355 Lima, M.A, Ligo, M.A.V., Cabral, O.M.R., Boeira, R.C., Pessoa, M.C.P.Y & Neves, M.C (19 99) Emissao de gases de efeito estufa provenientes da queima de residuos agricolas no Brasil (SP- Brazil: Embrapa Meio Ambiente) Macedo, I.C (19 98) Greenhouse gas emissions and energy balances in bio-ethanol production and utilization . boilers 7965 (12 45) 7325 (11 45) 7066 (11 04) 7706 (12 04) Intermediate 87 71 (13 70) 813 1 (12 70) 7872 (12 30) 8 512 (13 30) Advanced 9605 (15 01) 8965 (14 01) 8706 (13 60) 9346 (14 60) Values in parenthesis. constituent 4 CO 2 release Nitrogen 70.0 kg 1 3 .14 per Kg 220.0kg Phosphorous (P 2 O 5 ) 23.0 kg 1 0. 61 per Kg 14 .0kg Potassium (K 2 O) 13 2.0 kg 1 0.44 per kg 58.1kg Lime 15 00.0 kg 1 0 .13 per kg 19 5.0kg Herbicides. with increase of M.D. De Oliveira Avenida 10 , 12 60, Rio Claro - SP - Brazil, CEP 13 500-450 e-mail: dias oliveira@msn.com D. Pimentel (ed.), Biofuels, Solar and Wind as Renewable Energy Systems, C  Springer