BIOMASS, LAND-USE CHANGES AND ENVIRONMENTAL IMPACTS: A QUALITATIVE AND QUANTITATIVE REVIEW OF SCIENTIFIC LITERATURE

Non-food biomass production has developed significantly in the latest decades to meet the needs of the bio-economy, and should expand in the future. Concerns around the consequences on land-use prompted a surge in scientific publications over the past 10 years. Attributing LUC to biomass production and ultimately the rising demand for its end-products (eg, biofuels) requires the elicitation of mechanisms relating feedstock production to land use or management changes, and their impacts on the environment. They may be analysed as a three-step causal chain starting with the identification of factors driving feedstock production, the assessment of LUC occurring in response to this demand, and the associated environmental impacts. A key question is whether or not the inclusion of LUC effects in this balance may negate their potential benefits over fossile-based products. Here we surveyed the scientific literature on LUC in general between 1975 and 2014, and retrieved a body of about 240 references which were analysed in details in terms of scope, LUC types, methodologies employed, and overall outcomes. Liquid biofuels accounted for 75% of the bio-based end-products analysed, the remaining 25% being dominated by combustion applications and a marginal contribution of biomaterials and chemicals. The predominant types of LUC included the conversion of annual crops or grassland to perennial crops and grassland to annual crops, followed by the conversion of forests. Although it was difficult to separate between direct and indirect LUC, it was surprising to note that the majority of these changes (60%) occurred in Europe and North America, whereas South America only accounted for 19% of those. In terms of methodologies economic and biophysical models dominated for LUC assessment, and so did life-cycle assessment for the environmental impacts. However, a large fraction of studies relied on much simpler methods. The emissions of greenhouse gases was the first impact category studied, while the impact on biodiversity was rarely evaluated (only 5% of the articles dealt with it), as was the impact on air quality or human health. Overall, the substitution of fossile fuels by biofuels was deemed beneficial even when factoring in LUC effects, but a significant fraction of the studies concluded to the opposite, or to variable outcomes depending on the characteristics of the bio-based value-chain assessed. Some clear-cut trends emerged, such an adverse impact of biomass development on biodiversity or an increase in water consumption. Establishing perennial species presented a more favorable profile than other types of feedstocks. There is a need to widen the scope of LUC studies beyond liquid biofuels, to assess multiple criteria simultaneously, and to improve and harmonize the assessment methodologies.