Terpenes and their derivatives are a diverse family of biological molecules that provide a rich chemical space for finding renewable fuels with superior properties. Plants and microorganisms synthesize terpenes by combining units of isoprene (2-methyl-1,3-butadiene). Products made from one isoprene (hemiterpenes; C5) are suitable as gasoline alternatives, while products from two isoprenes (monoterpenes; C10) and three isoprenes (sesquiterpenes; C15) can replace jet fuels and diesel fuels. Proposals for large-scale production of terpenes include harvesting them from agricultural crops or from microorganisms growing in bioreactors . The compartmentalized nature of terpene biosynthesis provides opportunity to genetically engineer favored organisms such as Eucalyptus or E. coli to make any desired terpene, and to metabolically engineer yields that are beyond the natural baseline . The branched structure of isoprene causes most terpenes to have methyl side chains, which promotes favorable cold-weather properties such as low melting points . The biosynthesis process readily produces rings, including strained rings with carbon numbers as low as three, which gives terpenes high energy densities . The bio-synthesis process can also functionalize the terpenes by adding hydroxyl groups, carbonyls, ether bridges, etc. (These molecules are often termed terpenoids, but we will include them with terpenes.) For some applications, especially current aviation engines, oxygen and double bonds are not acceptable since they compromise energy density and storage stability; therefore terpenes must be hydrogenated to saturated hydrocarbons before they can be used as fuels . However, other cases may be less restrictive; for example, the hemiterpene prenol (3-methyl-2-buten-1-ol) is being investigated as a gasoline blendstock due to its high octanesensitivity and synergistic blending behavior for octane number .