• Energy Research

Abstract Biofuel production is a key strategy for reducing CO2 emissions globally and is expected to increase substantially in the coming decades, particularly in tropical developing countries. The adoption of sustainable biofuel production technologies that do not place large demands on agricultural or forested lands, has the potential to make a substantial contribution to decreasing greenhouse gas emissions while reducing biodiversity losses and degradation of native ecosystems resulting from high demand for land. With their high productivity per unit area and ability to grow on non-arable lands, microalgal biofuel production systems could become a major sustainable alternative to biofuel production from food crops (first-generation biofuels). However, the potential impacts of microalgal biofuels on food production, biodiversity, and carbon storage, compared to other biofuel production alternatives, are largely unknown. In the present study, the most suitable areas for siting microalgae production farms to fulfill 30% of future transport energy demands were determined within four Neotropical countries with high population densities and high importance for agricultural expansion and biodiversity conservation globally (Colombia, Ecuador, Panama, and Venezuela). These results were contrasted with the best areas for siting oil palm and sugarcane crops to fulfill the same target in future transport energy demands. Microalgal production systems offer the most sustainable alternative for future biofuel production within the Neotropics. Meeting 30% of future transport energy demands with microalgal biofuels reduced land area requirements by at least 52% compared to oil palm and sugarcane. Furthermore, microalgal biofuel production reduced direct competition with agricultural lands, biodiverse areas, and carbon-rich systems within countries, with little overlap with the biodiverse and carbon-rich rainforests. This study can guide decision making towards the identification and adoption of more sustainable biofuel production alternatives in the Neotropics, helping in avoiding unnecessary environmental impacts from biofuel expansion in the region.

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.

Abstract The sustainable, efficient production of biofuel can lead to reductions in greenhouse gas emissions, lowered climate change impact and increased security owing to the fulfilment of global energy demands. Microalgae have been shown as an attractive feedstock for renewable fuel production, such as biodiesel and biogas. To date, more effort has been put towards the production of biodiesel using the lipid contents in algal cells, while less attention has been placed on biogas production through anaerobic digestion. However, anaerobic digestion has the potential to generate energy from waste residues and to mobilize nutrients enabling subsequent recovery and/or recycling. Therefore, anaerobic digestion is an area with strong potential for novel research focusing on the development of a sustainable integrated system of biodiesel and biogas production. The result is essentially a solar power plant, producing fuel with minimal inputs and a closed nutrient loop, a necessity for sustainable and cost-efficient production of biofuel. In this review we discuss relevant studies on biodiesel and biomethane production, including the potential improvements and advantages when using an integrated approach for biodiesel and biogas production with special focus on nutrient recycling.

AbstractSustainable alternatives to fossil fuels are urgently needed to avoid severe climate impacts and further environmental degradation. Microalgae are one of the most productive crops globally and do not need to compete for arable land or freshwater resources. Hence, they may become a promising, more sustainable cultivation alternative for the large‐scale production of biofuels provided that substantial reductions are achieved in their production costs. In this study, we identify the most suitable areas globally for siting microalgal farms for biodiesel production that maximize profitability and minimize direct competition with food production and direct impacts on biodiversity, based on a spatially explicit multiple‐criteria decision analysis. We further explore the relationships between microalgal production, agricultural value, and biodiversity, and propose several solutions for siting microalgal production farms, based on current and future targets in energy production using integer linear programming. If using seawater for microalgal cultivation, biodiesel production could reach 5.85 × 1011 L/year based on top suitable lands (i.e., between 13% and 16% of total transport energy demands in 2030) without directly competing with food production and areas of high biodiversity value. These areas are particularly abundant in the dry coasts of North and East Africa, the Middle East, and western South America. This is the first global analysis that incorporates economic and environmental feasibility for microalgal production sites. Our results can guide the selection of best locations for biofuel production using microalgae while minimizing conflicts with food production and biodiversity conservation.

Microalgae are a promising alternative for future biofuel production. Compared to first- and second-generation biofuels, microalgal production systems offer higher biofuel productivities per unit area and do not necessarily depend on fertile soils or freshwater. However, little is known about how microalgal biofuel production on a scale large enough to meet a nation’s domestic transport energy targets might conflict with agricultural lands and biodiversity in the context of energy independence. Here, we use estimates of lipid productivity, resource availability, and accessibility to identify the most cost-effective areas for fulfilling 30% of each country’s transport energy demands in 2016 and 2050 while avoiding areas of high agricultural and biodiversity value. To fulfill this target, microalgal cultivation would need less than 1.1% of global land area, mainly in drier low-latitude areas or drier lowlands within each country. The most promising countries for microalgal biofuel production are mainly located in North and East Africa, the Middle East, western South America, the Caribbean, and Oceania. In countries with either high energy demands or without available human-transformed dry lands, decreasing targets in microalgal biofuel production or shifting production to countries where impacts are lower, could further reduce potential conflicts with food production and biodiversity.

Energy and fuel demands, which are currently met primarily using fossil fuels, are expected to increase substantially in the coming decades. Burning fossil fuels results in the increase of net atmospheric CO2 and climate change, hence there is widespread interest in identifying sustainable alternative fuel sources. Biofuels are one such alternative involving the production of biodiesel and bioethanol from plants. However, the environmental impacts of biofuels are not well understood. First generation biofuels (i.e. those derived from edible biomass including crops such as maize and sugarcane) require extensive agricultural areas to produce sufficient quantities to replace fossil fuels, resulting in competition with food production, increased land clearing and pollution associated with agricultural production and harvesting. Microalgal production systems are a promising alternative that suffer from fewer environmental impacts. Here, we evaluate the potential impacts of microalgal production systems on biodiversity compared to first generation biofuels, through a review of studies and a comparison of environmental pressures that directly or indirectly impact biodiversity. We also compare the cultivation area required to meet gasoline and distillate fuel oil demands globally, accounting for spatial variation in productivity and energy consumption. We conclude that microalgal systems exert fewer pressures on biodiversity per unit of fuel generated compared to first generation biofuels, mainly because of reductions in direct and indirect land-use change, water consumption if water is recycled, and no application of pesticides. Further improvements of technologies and production methods, including optimization of productivities per unit area, colocation with wastewater systems and industrial CO2 sources, nutrient and water recycling and use of coproducts for internal energy generation, would further increase CO2 savings. Overall pollution reductions can be achieved through increased energy efficiencies, along with nutrient and water recycling. Microalgal systems provide strong potential for helping in meeting global energy demands sustainably.

If humanity aims to avoid further biodiversity losses and environmental degradation, future energy demands must be met through the use of more sustainable energy production systems. Biofuels have been proposed as a more sustainable alternative for energy production as, under several cultivation conditions, they reduce greenhouse gas emissions and facilitate carbon recycling over much shorter time frames than fossil fuels. However, several environmental impacts have been linked to biofuel production, particularly when their cultivation competes with food production and biodiverse lands.Microalgal production systems may become a more sustainable option for the production of biofuels, as a result of their high yields per unit area, their potential to use different types of water (freshwater, brackish water, and seawater), their non-dependence on arable lands, and their potential to use wastewater and CO2 from industries. This project evaluates the several potential environmental impacts of microalgal liquid biofuel production systems compared to first generation biofuels (i.e., food crops such as maize, sugarcane, soybeans, and oil palm), with a focus on vertebrate biodiversity. Additionally, it identifies cost-effective areas for siting microalgal production farms globally, in which profitability is maximized and direct competition with food production and biodiverse areas is minimized. Finally, it evaluates how novel and more sustainable biofuel production systems can be implemented in order to gradually replace less sustainable biofuel production systems, which include those based on food crops.This work improves the understanding of the potential synergies and trade-offs between microalgal biofuel production, agricultural production, and biodiversity conservation at global and regional scales. Furthermore, it provides a framework for identifying best areas for siting microalgal biofuel production farms globally based on targets in energy demands. Microalgal biofuel production systems can help humankind achieve ambitious targets in energy production with lower environmental impacts than first generation biofuels, mainly in terms of reduced land-use changes within high-value agricultural areas and biodiverse lands.