Environmental impacts of bioenergy crop production and benefits of multifunctional bioenergy systems

Increasing concerns over dependence on fossil fuels instigated the demand for biofuel production over the past two decades, which has led to an increase in competition for productive agricultural land, shifts in land use among different crops, and conversion of land from other uses into biofuel production. These biofuel-induced changes in land use and management can have significant impacts on the environment, which vary widely across landscapes, bioenergy feedstocks, and production practices. Extensive production of conventional first-generation bioenergy crops such as corn (Zea mays L.) and harvest of corn stover for biofuel production increase soil erosion, water and air pollution, and biodiversity losses. It also causes substantial carbon debt due to the release of a greater quantity of carbon dioxide (CO₂) from land use changes than the greenhouse gas reductions from the displacement of fossil fuels. In contrast, replacing annual crops with perennial grasses, such as switchgrass (Panicum virgatum L.) and Miscanthus x giganteus, provides many environmental benefits, such as reduced sediment and nutrient losses, and increased soil carbon levels and biodiversity, and helps in minimizing climate change impacts. However, the use of productive cropland for bioenergy crops could lead to the competition between food and fiber versus fuel. Marginal and degraded lands where food crops may not be profitable and the conservation reserve areas offer the opportunity to develop economically and ecologically sustainable cellulosic bioenergy systems. However, as the market for cellulosic biofuel is under significant pressure due to highly volatile oil prices, biofuel production systems need to be developed as multifunctional landscapes along with conventional cropping systems to maximize ecosystem functions and minimize food versus fuel competition. This chapter provides an overview of biofuel-related changes in land use and management, discusses associated environmental impacts, and describes potential ways to ensure environmentally sustainable biofuel production.