Energy content of biofuel

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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]

Contents


Energy and CO2 output of common biofuels

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.

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 10– 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        Archived 2007-02-13 at the Wayback Machine 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) 39.49    33.18    (12% (C16H32O2)+16% (C18H34O2)+71% (LA)+1% (ALA))2.81 14.04 
Castor oil (C18H34O3) 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 Not Counting: 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   Archived 2005-09-11 at the Wayback Machine 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 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     (1.5 * NiMH) 0.54     (~300 Deep-Cycle Tolerance) 0.0   
Zinc–air battery 0.396–0.72     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

CropOil
(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
Copra62
Tallow35–42161240–6075
Lard32–36141060–7065
Corn (maize)14517212918-5-10-12115–12453
Cashew nut14817613219
Oats18321716323
Lupine19523217525
Kenaf23027320529
Calendula25630522933
Cotton27332524435(Seed)13-1 – 0-5-8100–11555
Hemp30536327239
Soybean3754463354814-16 – -12-10-12125–14053
Coffee38645934549
Linseed (flax)40247835951-24178
Hazelnuts40548236251
Euphorbia44052439356
Pumpkin seed44953440157
Coriander45053640257
Mustard seed4815724306135
Camelina49058343862
Sesame 5856965227450
Safflower65577958583
Rice69682862288
Tung oil tree790940705100-2.5168
Sunflowers 80095271410232-18 – -17-12-14125–13552
Cocoa (cacao)8631,026771110
Peanuts8901,059795113393
Opium poppy9781,163873124
Rapeseed 1,0001,19089312737-10–5-10–0-12 – -297–11555–58
Olives 1,0191,212910129-12 – -6-6-877–9460
Castor beans1,1881,4131,061151(Seed)50-1885
Pecan nuts1,5051,7911,344191
Jojoba1,5281,8181,365194
Jatropha1,5901,8921,420202
Macadamia nuts1,8872,2461,685240
Brazil nuts2,0102,3921,795255
Avocado2,2172,6381,980282
Coconut2,2602,6892,01828720–25-9-68–1070
Chinese Tallow [nc 2] 4,700500
Oil palm 5,0005,9504,46563520–(Kernal)3620–40-8–21-8–1812–9565–85
Algae 95,00010,000[ citation needed ]
CropOil
(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

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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. 1 2 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. 1 2 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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