FACTBOX: Biofuels, cases for the defense and prosecution

(Reuters) - Biofuels are under fire. Critics say they contribute to soaring food prices and damage the environment. Defenders say biofuels are an important alternative to fossil fuels in the fight against global warming.

FOOD VERSUS FUEL -- BIOFUEL IMPACT ON FOOD PRICES

Following are Goldman Sachs estimates of the percentage of agricultural crop that biofuels used globally in 2006. While little wheat is used for biofuel directly, the fuel uses other crops such as corn and rapeseed which could displace land sown to wheat and so impact prices of this vital human food crop.

Wheat Corn Soybean Rapeseed Sugarcane

Human consumption 81 pct 26 pct 31 pct 33 pct 85 pct

Livestock feed 17 pct 67 pct 68 pct 57 pct 0.4 pct

Biofuel 1 pct 7 pct 1 pct 10 pct 14 pct

GREENHOUSE GAS EMISSIONS CUTS -- BIOFUEL COMPARED TO FOSSIL FUEL

Ethanol produced from sugar cane in Brazil delivers the biggest cuts in greenhouse gas emissions compared to gasoline, analysts say, because it is a pure source of sugar and is extensively farmed, unlike grains including corn and wheat which use up energy on the farm and to extract sugar for distillation.

Nobel laureate chemist Paul J. Crutzen last year estimated that ethanol from wheat had as much as twice the global warming impact of gasoline, because of fertilizer use which releases a potent greenhouse gas nitrous oxide.

Following are estimated percentage greenhouse gas emissions cuts that biofuels deliver compared to fossil fuels, using various assumptions. BIOFUEL Ethanol Ethanol Ethanol Biodiesel Biodiesel Ethanol CROP Grains Sugarbeet Sugarcane Rapeseed Palm oil Cellulose (ORIGIN) (EU, U.S.) (EU) (Brazil) (EU) (Malaysia) (planned) SOURCE: IEA 13-30 pct 40-60 pct 90 pct 40-60 pct N.A N.A OECD 25 pct 40 pct 85 pct 50 pct 35 pct 70 pct Crutzen -210 to +10 pct N.A 10-50 pct N.A N.A N.A

Sources: 1. Goldman Sachs, Commodities: Food, Feed and Fuel, March 2007 2. IEA, World Energy Outlook, 2006 3. OECD, Biofuels: is the cure worse than the disease, Sept 2007 4. Crutzen et al., N2O release from agro-biofuel production negates global reduction by replacing fossil fuels, Atmos. Chem. Phys. Discuss., Aug 2007 (Reporting by Gerard Wynn; editing by Janet McBride)