Energy content of biofuel

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.Kenneth E. Heselton (2004), "Boiler Operator's Handbook". Fairmont Press, 405 pages. 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.

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 typeSpecific energy(MJ/kg)Energy Density(MJ/L)CO2 Gas made from Fuel Used(kg/kg)Energy per CO2(MJ/kg) Solid FuelsBagasse (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)n10–16           1.6–16.64      IF 50%(C6H10O5)n+25% (C26H42O21)n+25% (C10H12O3)n1.84 5.44-8.70 Wood fuel (C6H10O5)n16–21            2.56–21.84      IF 45%(C6H10O5)n+25% (C26H42O21)n+30% (C10H12O3)n1.88 8.51–11.17 Charcoal30           5.4–6.6 85–98% Carbon+VOC+Ash 3.63 8.27  Liquid FuelsPyrolysis oil17.5        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 Ecalene28.4        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 Fat37.656    31.68      C55H104O6 Biodiesel37.8        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 FuelsMethane (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)Coal29.3–33.5        39.85–74.43      (Not Counting: CO, NOx, Sulfates & Particulates) ~3.59 ~8.16–9.33 Crude Oil41.868    28–31.4        (Not Counting: CO, NOx, Sulfates & Particulates) ~3.4  ~12.31 Gasoline45–48.3        32–34.8        (Not Counting: CO, NOx, Sulfates & Particulates) ~3.30 ~13.64–14.64 Diesel48.1        40.3        (Not Counting: CO, NOx, Sulfates & Particulates) ~3.4  ~14.15 Natural Gas38–50           (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)Uranium -235 (235U)77,000,000           (Pure)1,470,700,000           [Greater for lower ore conc.(Mining, Refining, Moving)] 0.0   ~55 – ~90Nuclear 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 Methanol4.5466   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 battery0.108    ~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 battery0.162–0.288    ~0.24      (1k–1.5k Cycle Tolerance IF no Memory effect) 0.0   Nickel–metal hydride0.22–0.324    0.36      (300–500 Cycle Tolerance IF no Memory effect) 0.0   Super-iron battery0.33       (1.5 * NiMH) 0.54       (~300 Deep-Cycle Tolerance) 0.0   Zinc–air battery0.396–0.72       0.5924–0.8442   (Recyclable by Smelting & Remixing, not Recharging) 0.0   Lithium-ion battery0.54–0.72      0.9–1.9        (3–5 y Life) (500-1k Deep-Cycle Tolerance) 0.0   Lithium-Ion-Polymer0.65–0.87      (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–Air1.0584–1.5912   5.148–6.3216   (1–3 y Shelf-life) (Recyclable not Rechargeable) 0.0   Aluminium battery1.8–4.788    7.56      (10–30 y Life) (3k+ Deep-Cycle Tolerance) 0.0   PolyPlusBC Li-Aircell3.6–32.4        3.6–17.64      (May be Rechargeable)(Might leak sulfates) 0.0   

Notes

Yields of common crops associated with biofuels production

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

Notes

See also Eichhornia crassipes#Bioenergy Syngas Conversion of units Energy density Heat of combustion

References