A Quantitative Assessment of the Determinants of the Net Energy Value for Various Biofuels

Many recent studies have investigated the net energy value (in terms of savings of fossil fuel) of biofuel products and have assessed how much greenhouse gases emissions was curtailed by substituting biofuels for fossil fuel. Many of these studies rely on life cycle analyses, but some of them include also a more systemic modeling approach, while a few include a full blown economic analysis of the changes in agricultural and forestry production at the international level. In this study, we start from a large sample of technico-economic studies, and we attempt to unravel the determinants of the main findings in terms of net energy value. Our approach relies on econometric estimates of the effects of various potential determinants across studies. We use statistical decomposition techniques derived from meta-analysis, on a worldwide sample. The preliminary estimates suggest that the large variability across studies can be explained by determinants such as the type of feedstock, the degree of integration of economic mechanisms (from simple static life cycle analysis to large scale modeling accounting for changes in land use), the number of input nests for which energy consumption is controlled for, and to some extent, the type of organization that has carried out the study (suggesting some mandated science). The study makes it possible to construct an explicit formula that corrects for biases in the overall estimate, using hedonic techniques. This should prove useful for estimating the shadow price of greenhouse gas emission reductions and value the positive externalities of biofuels.