Economic considerations have featured in both primary analyses and reviews of the biotechnology of fuel ethanol production published in the last 25 years.11 Because a lignocellulosic ethanol industry has yet to fully mature, most of those studies have been derived from laboratory or (at best) small pilot-plant data, and estimates for feedstock and capital investment costs have varied greatly, as have assumptions on

the scale of commercial production required to achieve any intended price/cost target for the product. As with estimates of net energy yield and greenhouse gas reductions (chapter 1, sections 1.6.1 and 1.6.2), the conclusions reached are heavily influenced by the extent to which costs can be offset by coproduct generation (as a source of income) and of the complexity of the total production process, not only as a primary cause for increased setup costs but also a potential source of process efficiencies and additional, saleable coproducts.

Few of the influential studies are full business models for bioethanol, in particular avoiding any computations for profitability, often because the main driver has been to establish and substantiate grounds for initial or continued investment by national and/or international funding agencies — and with the implicit assumption that any production process for fuel ethanol outside Brazil suffers by that very comparison because of the lack of such favorable climatic and economic features (in particular, land use, labor cost, and the dovetailing of ethanol production with a fully mature sugarcane industry). Nevertheless, a historical survey of key points in the develop­ment of the economic case for bioethanol reveals the convergence toward a set of key parameters that will be crucial for any biofuel candidate in the next 10-50 years.