The energy content of biofuel is the chemical energy contained in a given biofuel, measured per unit mass of that fuel, as specific energy, or per unit of volume of the fuel, as energy density. A biofuel is a fuel produced from recently living organisms. Biofuels include bioethanol, an alcohol made by fermentation—often used as a gasoline additive, and biodiesel, which is usually used as a diesel additive. Specific energy is energy per unit mass, which is used to describe the chemical energy content of a fuel, expressed in SI units as joule per kilogram (J/kg) or equivalent units.[1] Energy density is the amount of chemical energy per unit volume of the fuel, expressed in SI units as joule per litre (J/L) or equivalent units.[2]


Energy and CO2 output of common biofuels

See also: Orders of magnitude (specific energy density)

The table below includes entries for popular substances already used for their energy, or being discussed for such use.

The second column shows specific energy, the energy content in megajoules per unit of mass in kilograms, useful in understanding the energy that can be extracted from the fuel.

The third column in the table lists energy density, the energy content per liter of volume, which is useful for understanding the space needed for storing the fuel.

The final two columns deal with the carbon footprint of the fuel. The fourth column contains the proportion of CO2 released when the fuel is converted for energy, with respect to its starting mass, and the fifth column lists the energy produced per kilogram of CO2 produced. As a guideline, a higher number in this column is better for the environment. But these numbers do not account for other green house gases released during burning, production, storage, or shipping. For example, methane may have hidden environmental costs that are not reflected in the table. [1]

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Fuel Type Specific energy
(MJ/kg) 		Energy Density
(MJ/L) 		CO2 Gas made from Fuel Used
(kg/kg)[nb 1] 		Energy per CO2
(MJ/kg)
Solid Fuels
Bagasse (Cane Stalks) 9.6           ~+40%(C6H10O5)n+15% (C26H42O21)n+15% (C9H10O2)n1.30  7.41 
Chaff (Seed Casings) 14.6           [Please insert average composition here] 
Animal Dung/Manure [2] 10-[3] 15              [Please insert average composition here] 
Dried plants (C6H10O5)n 10 – 16            1.6 - 16.64       IF 50%(C6H10O5)n+25% (C26H42O21)n+25% (C10H12O3)n1.84  5.44-8.70 
Wood fuel (C6H10O5)n 16 – 21            [4] 2.56 - 21.84       IF 45%(C6H10O5)n+25% (C26H42O21)n+30% (C10H12O3)n1.88  8.51-11.17 
Charcoal 30            5.4-6.6  85-98% Carbon+VOC+Ash 3.63  8.27 
Liquid Fuels
Pyrolysis oil 17.5         21.35       varies  varies 
Methanol (CH3-OH) 19.9 – 22.7         15.9         1.37  14.49-16.53 
Ethanol (CH3-CH2-OH) 23.4 – 26.8         18.4 - 21.2         1.91  12.25-14.03 
Ecalene 28.4         22.7         75%C2H6O+9%C3H8O+7%C4H10O+5%C5H12O+4%Hx 2.03  14.02 
Butanol(CH3-(CH2)3-OH) 36            29.2         2.37  15.16 
Fat 37.656     31.68       C55H104O6 
Biodiesel 37.8         33.3 – 35.7         ~2.85  ~13.26 
Sunflower oil (C18H32O2) [5] 39.49       33.18       (12% (C16H32O2)+16% (C18H34O2)+71% (LA)+1% (ALA))2.81  14.04 
Castor oil (C18H34O3) [6] 39.5         33.21       (1% PA+1% SA+89.5% ROA+3% OA+4.2% LA+0.3% ALA)2.67  14.80 
Olive oil (C18H34O2) 39.25 - 39.82       33 - 33.48       (15% (C16H32O2)+75% (C18H34O2)+9% (LA)+1% (ALA))2.80  14.03 
Gaseous Fuels
Methane (CH4) 55 – 55.7         (Liquefied) 23.0 – 23.3         (Methane leak exerts 23 × greenhouse effect of CO2) 2.74  20.05-20.30 
Hydrogen (H2) 120 – 142            (Liquefied) 8.5 – 10.1         (Hydrogen leak slightly catalyzes ozone depletion) 0.0    
Fossil Fuels (comparison)
Coal 29.3 – 33.5         39.85 - 74.43       (Not Counting:CO, NOx, Sulfates & Particulates) ~3.59  ~8.16-9.33 
Crude Oil 41.868     28 – 31.4         (Not Counting:CO,NOx,Sulfates & Particulates) ~3.4   ~12.31 
Gasoline 45 – 48.3         32 – 34.8         (Not Counting:CO,NOx,Sulfates & Particulates) ~3.30  ~13.64-14.64 
Diesel 48.1         40.3         (Not Counting:CO,NOx,Sulfates & Particulates) ~3.4   ~14.15 
Natural Gas 38 – 50            (Liquefied) 25.5 – 28.7         (Ethane, Propane & Butane N/C:CO,NOx & Sulfates) ~3.00  ~12.67-16.67 
Ethane (CH3-CH3) 51.9         (Liquefied) ~24.0         2.93  17.71 
Nuclear fuels (comparison)[nb 2]
Uranium -235 (235U) 77,000,000            (Pure)1,470,700,000            [Greater for lower ore conc.(Mining, Refining, Moving)] 0.0   ~55[4] - ~90[3]
Nuclear fusion (2H -3H) 300,000,000            (Liquefied)53,414,377.6         (Sea-Bed Hydrogen-Isotope Mining-Method Dependent) 0.0    
Fuel Cell Energy Storage (comparison)
Direct-Methanol 4.5466   [7] 3.6         ~1.37  ~3.31 
Proton-Exchange (R&D) up to 5.68       up to 4.5         (IFF Fuel is recycled) 0.0    
Sodium Hydride (R&D) up to 11.13       up to 10.24       (Bladder for Sodium Oxide Recycling) 0.0    
Battery Energy Storage (comparison)
Lead-acid battery 0.108     ~0.1         (200-600 Deep-Cycle Tolerance) 0.0    
Nickel-iron battery [8] 0.0487 - 0.1127    0.0658 - 0.1772    (<40y Life)(2k-3k Cycle Tolerance IF no Memory effect) 0.0    
Nickel-cadmium battery 0.162 - 0.288     ~0.24       (1k-1.5k Cycle Tolerance IF no Memory effect) 0.0    
Nickel metal hydride 0.22 - 0.324     0.36       (300-500 Cycle Tolerance IF no Memory effect) 0.0    
Super iron battery 0.33       [9] (1.5 * NiMH) 0.54       [10] (~300 Deep-Cycle Tolerance) 0.0    
Zinc-air battery 0.396 - 0.72       [11] 0.5924 - 0.8442    (Recyclable by Smelting & Remixing, not Recharging) 0.0    
Lithium ion battery 0.54 - 0.72       0.9 - 1.9         (3-5 y Life) (500-1k Deep-Cycle Tolerance) 0.0    
Lithium-Ion-Polymer 0.65 - 0.87       (1.2 * Li-Ion)1.08 - 2.28       (3-5 y Life) (300-500 Deep-Cycle Tolerance) 0.0    
Lithium iron phosphate battery                  
DURACELL Zinc-Air 1.0584 - 1.5912    5.148 - 6.3216    (1-3 y Shelf-life) (Recyclable not Rechargeable) 0.0    
Aluminium battery 1.8 - 4.788     7.56       (10-30 y Life) (3k+ Deep-Cycle Tolerance) 0.0    
PolyPlusBC Li-Aircell 3.6 - 32.4         3.6 - 17.64       (May be Rechargeable)(Might leak sulfates) 0.0    

Notes

  1. ^ While all CO2 gas output ratios are calculated to within a less than 1% margin of error(assuming total oxidation of the carbon content of fuel), ratios preceded by a Tilde (~) indicate a margin of error of up to (but no greater than) 9%. Ratios listed do not include emissions from fuel plant cultivation/Mining, purification/refining and transportation. Fuel availability is typically 74–-84.3% NET from source Energy Balance.
  2. ^ While Uranium-235 (235U) fission produces no CO2 gas directly, the indirect fossil fuel burning processes of Mining, Milling, Refining, Moving & Radioactive waste disposal, etc. of intermediate to low-grade uranium ore concentrations produces some amount of carbon dioxide. Studies vary as to how much carbon dioxide is emitted. The United Nations Intergovernmental Panel on Climate Change reports that nuclear produces approximately 40 g of CO2 per kilowatt hour (11 g/MJ, equivalent to 90 MJ/kg CO2e).[3] A meta-analysis of a number of studies of nuclear CO2 lifecycle emissions by academic Benjamin K. Sovacool finds nuclear on average produces 66 g of CO2 per kilowatt hour (18.3 g/MJ, equivalent to 55 MJ/kg CO2e).[4] One Australian professor claims that nuclear power produces the equivalent CO2 gas emissions per MJ of net-output-energy of a Natural Gas fired power station. Prof. Mark Diesendorf, Inst. of Environmental Studies, UNSW.

Yields of common crops associated with biofuels production

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Crop Oil
(kg/ha) 		Oil
(L/ha) 		Oil
(lb/acre) 		Oil
(US gal/acre) 		Oil per seeds[nc 1]
(kg/100 kg) 		Melting Range (°C) Iodine
number 		Cetane
number
Oil /
Fat 		Methyl
Ester 		Ethyl
Ester
Groundnut (Kernel)42
Copra 62
Tallow 35 - 42 16 12 40 - 60 75
Lard 32 - 36 14 10 60 - 70 65
Corn (maize) 145 172 129 18 -5 -10 -12 115 - 124 53
Cashew nut 148 176 132 19
Oats 183 217 163 23
Lupine 195 232 175 25
Kenaf 230 273 205 29
Calendula 256 305 229 33
Cotton 273 325 244 35 (Seed)13 -1 - 0 -5 -8 100 - 115 55
Hemp 305 363 272 39
Soybean 375 446 335 48 14 -16 - -12 -10 -12 125 - 140 53
Coffee 386 459 345 49
Linseed (flax) 402 478 359 51 -24 178
Hazelnuts 405 482 362 51
Euphorbia 440 524 393 56
Pumpkin seed 449 534 401 57
Coriander 450 536 402 57
Mustard seed 481 572 430 61 35
Camelina 490 583 438 62
Sesame 585 696 522 74 50
Safflower 655 779 585 83
Rice 696 828 622 88
Tung oil tree 790 940 705 100 -2.5 168
Sunflowers 800 952 714 102 32 -18 - -17 -12 -14 125 - 135 52
Cocoa (cacao) 863 1,026 771 110
Peanuts 890 1,059 795 113 3 93
Opium poppy 978 1,163 873 124
Rapeseed 1,000 1,190 893 127 37 -10 - 5 -10 - 0 -12 - -2 97 - 115 55 - 58
Olives 1,019 1,212 910 129 -12 - -6 -6 -8 77 - 94 60
Castor beans 1,188 1,413 1,061 151 (Seed)50 -18 85
Pecan nuts 1,505 1,791 1,344 191
Jojoba 1,528 1,818 1,365 194
Jatropha 1,590 1,892 1,420 202
Macadamia nuts 1,887 2,246 1,685 240
Brazil nuts 2,010 2,392 1,795 255
Avocado 2,217 2,638 1,980 282
Coconut 2,260 2,689 2,018 287 20 - 25 -9 -6 8 - 10 70
Chinese Tallow[nc 2] 4,700 500
Oil palm 5,000 5,950 4,465 635 20-(Kernal)36 20 - 40 -8 - 21 -8 - 18 12 - 95 65 - 85
Algae 95,000 10,000[citation needed]
Crop Oil
(kg/ha) 		Oil
(L/ha) 		Oil
(lb/acre) 		Oil
(US gal/acre) 		Oil per seeds
(kg/100 kg) 		Melting Range (°C) Iodine
number 		Cetane
number
Oil /
Fat 		Methyl
Ester 		Ethyl
Ester

Notes

  1. ^ Typical oil extraction from 100 kg of oil seeds
  2. ^ Chinese Tallow (Sapium sebiferum, or Tradica Sebifera) is also known as the "Popcorn Tree"[5]

See also

References

  1. ^ Kenneth E. Heselton (2004), "Boiler Operator's Handbook". Fairmont Press, 405 pages. ISBN 0881734357
  2. ^ "The Two cap of SI Units and the SI Prefixes". NIST Guide to the SI. Retrieved 2012-01-25.
  3. ^ a b Intergovernmental Panel on Climate Change (2007). "4.3.2 Nuclear energy". IPCC Fourth Assessment Report: Climate Change 2007, Working Group III Mitigation of Climate Change. Retrieved 2011-02-07.
  4. ^ a b Benjamin K. Sovacool.Valuing the greenhouse gas emissions from nuclear power: A critical survey. Energy Policy, Vol. 36, 2008, p. 2950.
  5. ^ Used with permission from The Global Petroleum Club.


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