Biofuels, Solar and Wind as Renewable Energy Systems_Benefits and Risks Episode 2 Part 7 pps

390 D. Pimentel, T. Patzek Table 15.9 Inputs per 1,000 kg of biodiesel oil from canola Inputs Quantity kcal × 1000 Costs $ Canola 3,333 kg a 9,355 a $1,419.00 a Electricity 270 kWh b 697 c 18.90 d Methanol 120L i 1,248 i 111.60 Steam 1,350,000 kcal b 1,350 b 11.06 e Cleanup water 160,000 kcal b 160 b 1.31 e Space heat 152,000 kcal b 152 b 1.24 e Direct heat 440,000 kcal b 440 b 3.61 e Losses 300,000kcal b 300 b 2.46 e Stainless steel 11 kg f 158 g 18.72 h Steel 21 kg f 246 g 18.72 h Cement 56 kg f 106 g 18.72 h TOTAL 14,212 $1,625.34 The 1,000 kg of biodiesel produced has an energy value of 9 million kcal. With an energy input requirement of 14.2 million kcal, there is a net loss of energy of 58%. If a credit of 4.6 million kcal is given for the canola meal produced, then the net loss is less. The cost per kg of biodiesel is $1.63. a Data from Table 15.6. b Data from Singh, 1986. c An estimated 3 kWh thermal is needed to produce a kWh of electricity. d Cost per kWh is 7c. e Calculated cost of producing heat energy using coal. f Calculated inputs. g Calculated from Newton, 2001. h Calculated. i Hekkert et al., 2005. are 40% greater than contained in the biodiesel fuel produced. Giving credit for the byproducts produced can reduce the fossil energy inputs only from 10% to 20%. An extremely low fraction of the sunlight reaching a hectare of cropland is cap- tured by green plant biomass. On average only 0.1% of the sunlight is captured by plants. This value is in sharp contrast to photovoltaics that capture more than 10% of the sunlight, or approximately 100–fold more sunlight than the green plant biomass. The environmental impacts of producing either ethanol or biodiesel from biomass are enormous. These include: severe soil erosion; heavy use of nitrogen fertilizer; and use of large quantities of pesticides (insecticides and herbicides). In addition to a significant contribution to global warming, there is the use of 1,000–2,000 liters of water required for the production of each liter of either ethanol or biodiesel. Furthermore, for every liter of ethanol produced there are 6–12 liters of sewage effluent produced. Burning food crops, such as corn and soybeans, to produce biofuels, creates ma- jor ethical concerns. More than 3.7 billion humans are now malnourished in the world and the need for food is critical. Energy conservation strategies combined with active development of renewable energy sources, such as solar cells and solar-based methanol synthesis systems, should be given priority. 15 Ethanol Production Using Corn, Switchgrass and Wood 391 References Ali, M. B. & McBride, W. D. (1990). Soybeans: State level production costs, characteristics, and input use, 1990. 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Tretrieved August 3, 2004, from http://p2library.nfesc.navy.mil/P2 Opportunity Handbook/7 III 13.html Chapter 16 Developing Energy Crops for Thermal Applications: Optimizing Fuel Quality, Energy Security and GHG Mitigation Roger Samson, Claudia Ho Lem, Stephanie Bailey Stamler and Jeroen Dooper Abstract Unprecedented opportunities for biofuel development are occurring as a result of increasing energy security concerns and the need to reduce greenhouse gas (GHG) emissions. This chapter analyzes the potential of growing energy crops for thermal energy applications, making a case-study comparison of bioheat, biogas and liquid biofuel production from energy crops in Ontario. Switchgrass pellets for bioheat and corn silage biogas were the most efficient strategies found for displacing imported fossil fuels, producing 142 and 123 GJ/ha respectively of net energy gain. Corn ethanol, soybean biodiesel and switchgrass cellulosic ethanol produced net energy gains of 16, 11 and 53 GJ/ha, respectively. Bioheat also proved the most efficient means to reduce GHG emissions. Switchgrass pellets were found to offset 86–91% of emissions compared with using coal, heating oil, natural gas or liquid natural gas (LNG). Each hectare of land used for production of switchgrass pellets could offset 7.6–13.1 tonnes of CO 2 annually. In contrast, soybean biodiesel, corn ethanol and switchgrass cellulosic ethanol could offset 0.9, 1.5 and 5.2 tonnes of CO 2 /ha , respectively. R. Samson Resource Efficient Agricultural Production (REAP) – Canada, Box 125 Centennial Centre CCB13, Ste. Anne de Bellevue, Quebec, Canada H9X 3V9, e-mail: rsamson@reap-canada.com C. Ho Lem Resource Efficient Agricultural Production (REAP) – Canada, Box 125 Centennial Centre CCB13, Ste. Anne de Bellevue, Quebec, Canada H9X 3V9 S. Bailey Stamler Resource Efficient Agricultural Production (REAP) – Canada, Box 125 Centennial Centre CCB13, Ste. Anne de Bellevue, Quebec, Canada H9X 3V9 J. Dooper Resource Efficient Agricultural Production (REAP) – Canada, Box 125 Centennial Centre CCB13, Ste. Anne de Bellevue, Quebec, Canada H9X 3V9 D. Pimentel (ed.), Biofuels, Solar and Wind as Renewable Energy Systems, C  Springer Science+Business Media B.V. 2008 395 396 R. Samson et al. The main historic constraint in the development of herbaceous biomass for ther- mal applications has been clinker formation and corrosion in the boiler during combustion. This problem is being overcome through plant selection and cultural techniques in grass cultivation, combined with advances in combustion technology. In the coming years, growing warm-season grasses for pellet production will emerge as a major new renewable energy technology, largely because it represents the most resource-efficient strategy to use farmland in temperate regions to create energy security and mitigate greenhouse gases. Keywords Combustion · bioheat · biomass · net energy balance · grass pellets · switchgrass · energy crop · greenhouse gas · thermal energy · energy security · biomass quality · perennial Acronyms & abbreviations Bioheat: biomass use for thermal applications C 3 : cool season C 4 : warm season Cl: Chlorine GHG: greenhouse gas K: Potassium LNG: liquefied natural gas N: nitrogen RET’s: renewable energy technologies Si: Silica WSG: warm season grass 16.1 Introduction In most industrialized countries, thermal energy represents the largest energy need in the economy. Thermal energy is used for space and water heating in the resi- dential, commercial and industrial sectors, low and high temperature process heat for industry, and power applications. Thermal energy can also be used for cool- ing applications. Rather than supporting biomass for simple thermal applications such as direct heating applications industrialized countries have currently placed emphasis on researching and providing subsidies for more technologically complex innovations such as large industrial bio-refineries. However, governments in indus- trialized nations who have identified the need to develop biofuels for energy security and greenhouse gas mitigation should look more closely at thermal applications for biomass to fulfill these needs. This review therefore examines energy security in section one, identifying opportunities to grow energy crops on farmland in eastern Canada as a means to collect solar energy and convert it into useful energy products 16 Developing Energy Crops for Thermal Applications 397 for consumption. The greenhouse gas (GHG) mitigation potential of switching from fossil fuels to various biofuels produced from energy crops is also examined. Section two then overviews recent advances in the emerging agricultural industry growing grasses for bioheat, identifying opportunities and challenges in advancing this tech- nology for commercial applications in temperate regions of the world. 16.2 Energy Crop Production for Energy Security and GHG Mitigation Since the Arab oil embargo in the 1970s there has been considerable interest in North America in growing both conventional field crops and dedicated energy crops for bioenergy as a means to enhance energy security. The long-term decline in farm commodity prices has also created significant interest in using the surplus produc- tion capacity of the farm sector as a means to produce energy while creating demand enhancement for the farm sector. This decline in farm commodity prices, due to in- novation in plant breeding and production technology, is accelerating the likelihood that large quantities of biomass energy from farms could penetrate energy markets currently dominated by fossil fuels. One of the strongest drivers for biofuel development is the GHG mitigation po- tential of energy crops to produce solid, liquid and gaseous biofuels to replace fossil fuels in our economy. With the increased use of grain crops for liquid biofuels, the past two years have seen a rise in both the demand and price for farm commodities. Also increasing however, are concerns over other important social issues such as the potential for bioenergy to compete with food security, and problems with soil erosion and long-term soil fertility. The production and utilization of crops residues as a global biofuel sources has recently been reviewed (Lal, 2005). The main con- clusions were that the most appropriate use of crop residues is to enhance, maintain and sustain soil quality by increasing soil organic matter, enhancing activity and species of soil fauna, minimizing soil erosion and non-source pollution, mitigating climate change by sequestering carbon in the pedosphere, and advancing global food security through enhancement of soil quality. It was recommended that efforts be undertaken to grow biomass on specifically dedicated land with species of high yield potential, suggesting that 250 million hectares (ha) globally could be put into production of perennial energy crops. The increasing biodiversity loss from agricultural landscapes through crop inten- sification is also a major environmental concern. The rapid development of liquid biofuels in the tropics in the past decade has also caused significant harm to bio- diversity through the conversion of forests into agricultural production. Resource efficient, rather than resource exhausting, bioenergy crop production strategies need to evolve with a priority placed on de-intensification of farm production through the use of perennials and utilization of existing marginal farmlands. This approach would to a much greater extent avoid the biofuel conflicts with food crop production and biodiversity that are now occurring with using annual food crops as biofuels. 398 R. Samson et al. To achieve the objective of resource efficient biomass production we must exam- ine some of the basic factors influencing biomass accumulation: 1. There are two main photosynthetic pathways for converting solar energy into plant material: the C 3 and C 4 pathways. The C 4 pathway is approximately 40% more efficient than the C 3 pathway in accumulating carbon (Beadle and Long, 1985). 2. C 4 species use approximately half the water of most C 3 species (Black, 1971). 3. In temperate climates, sunlight interception is often more efficient with perennial plants because annual plants spend much of the spring establishing a canopy and also exhibit poor growth on marginal soils. 4. Some species of warm season grasses are climax community species and have excellent stand longevity (which also results in decreased economic costs for establishing perennial crops through decreased expenditures for seeding, tillage etc.). 5. C 4 species of grasses contain less N than C 3 species and can be more N-use efficient in temperate zones because the N is cycled internally to the root system in the fall for use in the following growing season (Clark, 1977). It is apparent that the optimal plants for resource-efficient biomass production should be both perennial and C 4 in nature. 16.2.1 Perennial and Annual Energy Crops In North America, the warm continental climate has produced a diversity of na- tive warm season (C 4 ) perennial grasses that have a relatively high energy pro- duction potential on marginal farmlands. In the more humid zones, these species include switchgrass (panicum virgatum), prairie cordgrass (spartina pectinata), eastern gamagrass (tripsacum dactyloides), big bluestem (andropogon gerardii vit- man) and coastal panic grass (panicum amarum A.S. hitchc.). In semi-arid zones and dry-land farming areas, prairie sandreed (calamovilfa longifolia) and sand bluestem (andropogon hallii) are amongst the most productive species. All of these species are relatively thin stemmed, winter hardy, highly productive and are established through seed. Switchgrass was chosen as the model herbaceous energy crop species to concen- trate development efforts on in the early 1990s by the U.S. Department of Energy. It had a number of promising features including its moderate to high productivity, adaptation to marginal farmlands, drought resistance, stand longevity, low nitro- gen requirements and resistance to pests and diseases (Samson and Omielan, 1994; Parrish and Fike, 2005). Table 16.1 illustrates that in Ontario, Canada, C 4 species like corn and switchgrass produce considerably higher quantities of energy from farmland than C 3 crops. The perennial crops were also identified to have the lowest fossil energy input require- ments. Overall, prior to any conversion process, switchgrass produces 40% more 16 Developing Energy Crops for Thermal Applications 399 Table 16.1 Solar energy collection and fossil fuel energy requirements of Ontario Crops per hectare, adapted from Samson et al. (2005) Crop Yield (ODT/ha) Energy content (GJ/ODT) Fossil energy used (GJ/ODT) Fossil energy used (GJ/ha) Solar energy collected (GJ/ha) Net energy (GJ/ha) Canola 1.8 a 25.06.311.345 33.7 Soybean 2.2 a 23.83.27.052.4 45.3 Barley 2.8 a 19.03.911.053.2 42.3 Winter Wheat 4.4 a 18.72.912.882.3 69.5 Tame Hay 4.7 a 17.91.04.784.1 79.4 Grain Corn 7.3 a 18.82.921.2 137.2 116.1 Switchgrass 9 18.80.87.2 169.2 162.0 a OMAFRA, (2007) net-energy gain per hectare than grain corn and five times more net-energy gain per hectare than canola. It also should be noted that corn yields are based on modern hybrid yields in Ontario while switchgrass yields are based on commercial produc- tion of the cultivar cave in-rock, an unimproved cultivar that was collected from an Illinois prairie in 1958. Warm season grasses (WSG’s) function well as perennial energy crops because they mimic the biological efficiency of the tall-grass prairie ecosystem native to North America. They produce significantly more energy than grain corn while at the same time requiring minimal fossil energy inputs for field operations and less fertilizers and herbicides. In industrialized countries, the seed portion of annual grain and oilseed crops be- came the first feedstock for energy applications. However, whole plant annual crops capture much larger quantities of energy per hectare. In Western Europe, whole plant crops such as maize and rye are now commonly harvested for biogas applications. High yielding hybrid forage sorghum, sorghum-sudangrass and millet, also hold promise as new candidates for biogas digestion (Von Felde, 2007; Venuto, 2007). The major advantage of ensiling is that even in relatively unfavourable weather for crop drying, energy crops can be stored and delivered to the digester year round. This is particularly advantageous for thick stemmed species like maize and sorghum which are commonly difficult to dry in areas receiving more than 700 mm of rain- fall annually or have harvests late in the year when solar radiation is declining. In combustion applications, thick stemmed herbaceous species have biomass quality constraints which make them difficult to burn (further discussed in Section 16.3). In warm, humid southern production zones in temperate regions, it may also be difficult to dry the feedstock for combustion applications as the material would be more vulnerable to decomposition. In these situations, crop conversion to usable energy would be facilitated by using a biogas conversion system and storing the crop as silage. Overall, both thick and thin stemmed whole-plant biomass crops can be suc- cessfully grown for biogas applications. Highest biogas yields are achieved when a fine chop and highly digestible silage are used. Conversely, thin stemmed, perennial WSG’s have been identified as the most viable means to store dry crops for com- bustion applications and offer the best potential for improved biomass quality for [...]... Switchgrass Pellets Wood pellets Straw pellets kgCO2e /GJ c 62. 03 23 .40b 36.36d 28 .77 d 8.17e 13.14f 9.19f 8.17e 13.14f 9.19f 8.17e 13.14f 9.19f 8.17e 13.14f 9.19f Net offset emissions including N2 O (kgCO2e /GJ) %h 21 .13h 76 .16b 49 .73 h 57. 09h 84.94 79 . 97 83. 92 79 .73 74 .76 78 .71 65. 52 60.55 64.5 49.40 44.43 48.38 21 77 g 50 58 91 86 90 91 85 90 89 82 88 86 77 84 a Natural Resources Canada, (20 07) Emissions... Perennial Grass Energy Crops Biogas (Anaerobic Digestion) Corn Silage – 15.6 Feedstock 34 52. 9 L ethanol 323 0 L ethanol 1 37 .2 GJ Heat 154 .2 GJ Heat 6 625 m3 biogas 320 0 m3 biogas Gross Energy (GJ/ha) 0. 021 GJ/L 0. 021 GJ/L – – 67. 8 72 . 5 154 .2 1 37 .2 0. 023 2 GJ/m3 74 .2 0. 023 2 GJ/m3 153 .7 Total Conversione (GJ/unit) Energy Production (unit/ha) 15.3 56.6 12. 0 21 .2 13.0 31.0 Energy Used in Productionf (GJ/ha) 52. 5... Switchgrass Cellulosic Ethanol Grain Corn Ethanol Soybean Biodiesel Gross Energy (GJ/ha) Fossil Fuel Substitution Net GHG emission offsets kgCO2 e/GJ Total GHG emission offsets kgCO2 e/ha 154 .2 154 .2 154 .2 154 .2 Coal Heating Oil Liquefied Natural Gas Natural Gas 84.94 79 .73 65. 52 49.4 13098 122 94 10103 76 17 67. 8 Transport gasoline 76 .16 5164 70 .6 18 .2 Transport gasoline Transport diesel 21 .13 49 .73 14 92 905... basis) biogas (Braun and Wellinger, 20 05; L´ pez et al., 20 05) o Grass silage yields 350–450 m3 /tonne (dry matter basis) biogas (De Baere, 20 07; Berglund and B¨ rjesson, 20 06; M¨ hnert et al., 20 05) o a Grain corn has an energy content of 18.8 GJ/ODT (Schneider and Hartmann, 20 05) Switchgrass has an energy content of 18.8 GJ/ODT (Samson et al., 20 05) Corn ethanol yields 473 L/ODT (Farrell et al., 20 06)... field yield of 7. 3 ODT/ha equals 21 . 17 GJ/ha The energy input for switchgrass pellets is 12 GJ/ha, based on field energy inputs of 7. 9 GJ/ha and 4.1 GJ/ha for pellet processing and marketing (Samson et al., 20 00) Biofuels The energy output:input ratio for corn ethanol is 1 .28 :1 (Wang et al., 20 07) , this results in an energy input of 72 . 5/1 .28 = 47. 9 GJ/ha The energy output:input ratio switchgrass cellulosic... Productionf (GJ/ha) 52. 5 15.9 1 42. 2 116.0 61 .2 122 .7 Net Energy Gain (GJ/ha) Table 16 .2 Harvesting Energy from Ontario farmland for biofuel applications: A case study comparing alternative bioenergy crops and conversion technologies in Ontario 16 Developing Energy Crops for Thermal Applications 403 2. 6 Soybean Biodiesel 2. 2 Field Yieldb (ODT/ ha) – 2. 2 22 4 L/ODT biodiesel Net Yield Energy Content Losses (%)c... al., 20 06) Switchgrass ethanol yield is estimated at 340 litres per ODT (Spatari et al., 20 05; Iogen Corporation, 20 08) Soybean biodiesel yields 22 4 L/ODT (Klass, 1998) e Biogas energy = 0. 023 2 GJ/m3 (Klass, 1998) Ethanol energy = 0. 021 GJ/litre (Klass, 1998; Smith et al., 20 04) Electrical energy = 0.0036 GJ/kWh (Klass, 1998) Methyl ester soybean biodiesel = 0.03 524 GJ/litre (Klass, 1998) Field Yielda... gas for residential and commercial heating applications and process heat for industry and power generation, will begin to rely on distant foreign natural gas resources 16 .2. 2 .2 Harvesting Energy from Ontario Farmland for Biofuel Applications: A Case Study To optimize energy security and GHG mitigation potential from bioenergy, a case study has been developed to compare alternative bioenergy crops and. .. Densification 4 92. 3 L 0.03 524 GJ/L 17. 3 biodiesel Total Conversione Gross (GJ/unit) Energy Energy (GJ/ha) Production (unit/ha) 6.8 Energy Used in Productionf (GJ/ha) 10.6 Net Energy Gain (GJ/ha) a Corn and soybean yield is 5 year (20 02 20 07) average in Ontario (OMAFRA, 20 07) b Assuming that corn grain yield is 47% of total plant yield (Zan, 1998), silage corn field yield is equivalent to 7. 3 ODT/ha x 2. 13 =... comprised of 7. 9 GJ/ha for switchgrass production (Samson et al., 20 00), 1% methane leakage (1% of 71 .6 = 0 .7 GJ/ha (Zwart et al., 20 07) ), plus 2. 5% (Gerin et al., 20 08) of energy used for biodigester processing (2. 5% of 71 .6 GJ/ha = 1.8 GJ/ha) Total input is 2. 6 + 10.4 = 13 GJ/ha Bioheat The energy input for corn production in Ontario has been estimated to be 2. 9 GJ/ODT (Samson et al., 20 05) which assuming . 33 .7 Soybean 2. 2 a 23 .83 . 27 .0 52. 4 45.3 Barley 2. 8 a 19.03.911.053 .2 42. 3 Winter Wheat 4.4 a 18. 72 . 9 12. 8 82. 3 69.5 Tame Hay 4 .7 a 17. 91.04 .78 4.1 79 .4 Grain Corn 7. 3 a 18. 82. 921 .2 1 37 .2 116.1 Switchgrass. 500 m 3 / ODT biogas 6 625 m 3 biogas 0. 023 2 GJ/m3 153 .7 31.0 122 .7 Perennial Grass Energy Crops – 10 20 % (H/S) 8.0 400 m 3 / ODT biogas 320 0 m 3 biogas 0. 023 2 GJ/m3 74 .2 13.0 61 .2 Bioheat (Direct. 8.6 7. 3 – 7. 3 18.8 GJ/ODT Heat 1 37 .2 GJ Heat – 1 37 .2 21 .2 116.0 Switchgrass Pellet – 10 18% (H/D) 8 .2 18.8 GJ/ODT Heat 154 .2 GJ Heat – 154 .2 12. 0 1 42. 2 Biofuels Grain Corn Ethanol 8.6 7. 3 – 7. 3