I created this flow chart to help myself understand the variety of processes used to make ethanol from plants:

The large yellow arrow shows the pathway for "first generation" ethanol production from starches and sugars. This pathway consists of mature technologies: It has been used for centuries to make distilled spirits like vodka or whiskey, and it is used by today's ethanol refineries to make fuel from corn and sugarcane. It is compatible with both small and large-scale production systems. Its increasing use has led to concerns about competition with food supplies, energy efficiency, land-use efficiency, and sustainability. Some of those who feel first generation ethanol technology is irredemably flawed hold out hope for second generation technology...

Production of ethanol from cellulosic feedstocks, like wood or switchgrass, depends on further development of emerging technologies. People are pinning high hopes on such "second generation" ethanol production, with claims that it will allow efficient conversion of non-food feedstocks compatible with sustainable agriculture systems. Despite concerted research efforts to improve second generation technologies, and numerous claims of their superiority over first generation technologies, commercially viable examples are few.

My previous blog posting, with preliminary data from our farm scale study, brought several helpful comments from readers. I will refine our experimental methods to address some of the concerns raised. I see this as collaboration at its best. I am posting this diagram, which is very much a work in progress, in hopes that others may offer corrections, refinements, and critiques.

Michael Bomford provides research and extension services related to organic agriculture and small-scale renewable energy production through Kentucky State University's Land Grant Program.