Chapter 2: Overview of Biofuel Technologies

While the term “biofuels” can include a range of solid, liquid and gaseous fuels derived from organic matter or “biomass,” the focus of this report is on the development of liquid biofuels, which can be blended with gasoline and diesel and integrated into the existing infrastructure.

2.1 First-Generation Biofuels

First-generation biofuels are those biofuels in production today that rely primarily on food crops as their primary feedstock.

The primary biofuel produced in the US is ethanol (C₂H5_OH), which is the same alcohol found in alcoholic beverages. Ethanol has traditionally been produced by fermenting sugars or starches, which each require slightly different processing. Over 92% of US ethanol is produced from corn kernels, with production being centered in the Corn Belt of the Midwest. Most of the remaining 8% comes from grain sorghum (milo), wheat, barley or other similar grains, with only about 1% coming from agricultural co-products such as beverage waste, cheese whey, and others.⁴

A 10% blend of ethanol and gasoline (E10) has been certified as a motor vehicle fuel by the US EPA and is covered by warranties from every major car manufacturer, so it can be used in any car on the road today.C There are over four million “flex-fuel” vehicles on the road that can run on a blend of up to 85% ethanol (E85),⁵ although few gas stations offer E85 fuel as of yet.

As an established technology, which is easily integrated into our current infrastructure, sugar- or starch-based (“first-generation”) ethanol is likely to dominate US renewable fuels for at least the next five to ten years. However, it also has several disadvantages. Ethanol has only two-thirds of the energy of gasoline per gallon, thus resulting in lower gas mileage, and can’t be transported through conventional oil pipelines.⁶ The greatest limit on first-generation ethanol is the availability of sugar and starch feedstocks, however. Nearly 20% of the US corn crop already goes to ethanol production,D to meet only a small percentage of our gasoline needs.

The other major renewable fuel available today is biodiesel (fatty-acid methyl ester). There is already 1.85 billion gallons of biodiesel production capacity in the US, with another 1.37 billion gallons in capacity is under construction,⁷ although only 250 million gallons of biodiesel was sold in the US in 2006⁸ (compared to over 63 billion gallons of diesel sold).⁹

Biodiesel can be produced from any kind of oil or fat, including waste vegetable oils, virgin vegetable oils and animal fats. Unlike ethanol, which is the same molecule with the same properties no matter what feedstock it is produced from, biodiesel has distinct chemical properties depending on what feedstock oil is used. Biodiesel is produced by combining the oil with an alcohol (commonly methanol) in a process called transesterification, which is straightforward enough to be done in a home kitchen.

You can use either 100% biodiesel (B100) or any blend of 1-99% biodiesel (B1-B99) with petroleum diesel in standard diesel engines, usually with no modifications required.E Biodiesel contains 88-95% as much energy as diesel fuel on average, but its higher cetane rating means there is almost no discernable difference in miles per gallon.¹⁰

Hydrogenation-derived "Renewable Diesel"

The same range of oils and fats that can be used for biodiesel can be fed into a modified hydrotreating unit in a conventional diesel refinery to produce a fuel with very similar properties to diesel, which has been called “hydrogenation-derived renewable diesel” or simply “renewable diesel.”¹¹

Although very similar in terms of its environmental properties to biodiesel, because it can be produced in existing refineries by large oil refiners, the social and economic implications of renewable diesel are different.

There is already a vigorous debate on the federal level over whether incentives for biodiesel should be applied to renewable diesel as well, and policymakers in Oregon are likely to have to consider this issue as well.

However, renewable diesel suffers from the main restraint of first-generation biofuels: they depend on types of biomass (oils or sugars/starches) that are both limited in quantity and also used as food.

2.2 Second-Generation Biofuels

There are a range of technologies currently being commercialized that will allow the production of ethanol, biodiesel and other advanced fuels from cellulosic feedstocks, leading to what are often referred to as “second-generation biofuels.” Cellulose makes up the majority of plants in nature, and cellulosic feedstocks include corn or wheat stalks, forest thinnings, grasses and bushes: all materials that are potentially available in much greater quantities than first-generation feedstocks and won’t compete with food production. Second-generation biofuels are expected to become commercially viable over the next five to ten years, although technological breakthroughs could speed this up.

There are two main groups of technologies for converting cellulose to biofuels: the biochemical (or enzymatic) platform or the thermochemical platform. The biochemical platform uses enzymes to break cellulose down to sugars where it can be converted to ethanol. The thermochemical platform essentially involves heating biomass under conditions of low oxygen. In what is referred to as biomass-to-liquids or BTL, the biomass is gasified and then can be converted into a range of fuels including both ethanol and biodiesel. In fast pyrolysis, biomass is converted directly to a “bio-oil,” which can be used for heating of power generation or refined into a vehicle-grade fuel.

There are only a handful of mostly pilot-scale plants using these technologies in the world. In North America there are only two plants, both located in Canada: Iogen’s pilot-scale enzymatic cellulosic ethanol plant in Ottawa and Dynamotive’s small commercial-scale fast pyrolysis plant in West Lorne, Ontario. The US Department of Energy (USDOE) has just given grants totaling $385 million for six pilot-scale plants using a range of technologies; this, along with a range of other incentives being considered at the federal level, is likely to accelerate the development of cellulosic biofuels considerably. Still, it is likely to be five to ten years before commercial scale production of cellulosic biofuels will really begin to expand.^F

There is also substantial research going into developing new types of fuels that eliminate some of the disadvantages of ethanol or biodiesel. One of the more promising of these is biobutanol. Unlike ethanol, biobutanol (C₄H₁₀O) has nearly the same energy content as gasoline and is less water-soluble and corrosive. This means it could be transported through existing pipelines and blended at a higher level in existing vehicles. BP and Dupont, who have partnered to commercialize biobutanol, are also stating that existing ethanol facilities can be upgraded to produce biobutanol instead, which would eliminate the need for the creation of substantial new infrastructure.¹² Although it looks promising, substantially more study on the possible air and water quality impacts of biobutanol needs to be done before we can be sure of its suitability.