Towards the implementation of sustainable biofuel production systems

Highlights

• First generation biofuels are the least sustainable biofuel production alternative.

• Implementing more sustainable biofuel production systems is urgently needed.

• Sustainable biofuels need the integration of socioeconomic and environmental goals.

• Economic barriers to adopt these systems can be overcome through policy mechanisms.

Abstract

Novel energy production systems are needed that not only offer reductions in greenhouse gas emissions but also cause fewer overall environmental impacts. How to identify and implement more sustainable biofuel production alternatives, and how to overcome economic challenges for their implementation, is a matter of debate. In this study, the environmental impacts of alternative approaches to biofuel production (i.e., first, second, and third generation biofuels), with a focus on biodiversity and ecosystem services, were contrasted to develop a set of criteria for guiding the identification of sustainable biofuel production alternatives (i.e., those that maximize socioeconomic and environmental benefits), as well as strategies for decreasing the economic barriers that prevent the implementation of more sustainable biofuel production systems. The identification and implementation of sustainable biofuel production alternatives should be based on rigorous assessments that integrate socioeconomic and environmental objectives at local, regional, and global scales. Further development of environmental indicators, standardized environmental assessments, multi-objective case studies, and globally integrated assessments, along with improved estimations of biofuel production at fine spatial scales, can enhance the identification of more sustainable biofuel production systems. In the short term, several governmental mandates and incentives, along with the development of financial and market-based mechanisms and applied research partnerships, can accelerate the implementation of more sustainable biofuel production alternatives. The set of criteria and strategies developed here can guide decision making towards the identification and adoption of sustainable biofuel production systems.

Introduction

Boosting economic growth while halting environmental degradation remains one of the major global challenges for humankind [1]. Current unsustainable use of the Earth’s finite natural capital [2] has led to a wide range of negative impacts on the environment [3], including increasing biodiversity losses [4], alterations in the provision and quality of ecosystem services [5], and climate change [6]. These impacts and the decisions that society makes to reduce them, which include balancing human population growth [7] and planning for solutions based on multiple interacting environmental pressures [8], will have profound implications for global socioeconomic and environmental systems.

How to meet increasing energy consumption demands, while reversing environmental degradation, is a matter of debate [9]. Currently, the provision of energy relies primarily on fossil fuels, with around 5.8 × 10¹¹ GJ consumed globally in 2016, of which 81% was derived from coal, petroleum, and natural gas [10]. Their associated greenhouse gas (GHG) emissions are linked to global warming and its negative impacts on biodiversity [11] and ecosystem services [12]. Limiting global warming to well below 2 °C compared to pre-industrial levels, a goal ratified by 185 parties (i.e., on February 2019) following the 21st Conference of the Parties to the United Nations Framework Convention on Climate Change (UNFCCC) in Paris [13], is expected to require the rapid adoption of renewable energy systems for replacing fossil fuels [14]. Consequently, the share of energy from renewable sources could increase from 9% of total primary energy demands in 2016 to 29% by 2040 [10].

While solar, wind and water as renewable energy sources could provide electricity with lower environmental costs compared to fossil fuels [15], liquid fuels are expected to remain necessary in the transport sector—mainly for aviation, shipping, and long-haul trucking—in spite of an expected increase in electric vehicles [16]. In fact, some scenarios for limiting global warming to 2 °C foresee biofuel production increasing from 9.7 × 10⁶ GJ d^-1 to 4.6 × 10⁷ GJ d^-1 between 2016 and 2040, reaching 16% of total transport fuels [10], though it remains unclear to what degree biofuel adoption would reduce net GHG emissions compared to other climate change mitigation options [17].

Current biofuel production is based on food crops (i.e., first generation biofuels) that compete with agricultural lands and biodiverse landscapes (Box 1, Fig. 1). Furthermore, biofuel production has been linked to several other environmental pressures that may, directly and indirectly, impact biodiversity and the provision of ecosystem services. These pressures [18] include direct and indirect land-use change [19], GHG emissions [20], emission of pollutants (i.e., from pesticides, fertilizers, biofuel production, and final use of biofuels) [21], water depletion [22], soil degradation and erosion [23], and introduction of invasive species [24]. The impacts of biofuels on biodiversity and ecosystem services, however, depend on the type of biofuel production system and several factors associated with its cultivation and production [19], including: the competing land-use and the spatial configurations of biofuel cultivation landscapes [25], their cultivation and conversion technologies [21], their cultivation management practices [26], their invasiveness potential [27], and the presence of co-products (Box 2) [28].

How to identify and implement more sustainable biofuel production alternatives [51], and how to overcome economic obstacles to their implementation, are unresolved challenges [52]. Here, the environmental impacts of several biofuel production alternatives (i.e., first, second, and third generation biofuels) on biodiversity and ecosystem services are evaluated. This information is integrated with criteria and avenues of research for guiding the identification and implementation of sustainable biofuel production alternatives (i.e., those that maximize socioeconomic and environmental benefits). Finally, promising strategies for overcoming economic barriers to adopt more sustainable biofuel production systems are discussed.