Biodiversity impacts of bioenergy production: Microalgae vs. first generation biofuels

Abstract

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 different fuels which include biodiesel and bioethanol from plants.However, the environmental impacts of biofuels are not well understood. First generation biofuels (i.e. biofuels 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 area of cultivation land 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 3 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 meeting global energy demand sustainably.

Global mapping of cost‐effective microalgal biofuel production areas with minimal environmental impact

“…We propose best locations for siting microalgal farms for biodiesel production that meet substantial biofuel production levels while avoiding direct land‐use competition with agricultural lands and biodiverse areas, through a GIS‐based multiple‐criteria decision analysis and integer linear programming. We conclude that potential conflicts with food production and biodiversity conservation, as well as with freshwater consumption, can be reduced if cultivation is restricted to human‐transformed dry mainland coasts in tropical and subtropical regions of the world, in contrast to first‐generation biofuels, which need agricultural lands and freshwater (Correa et al, ). However, even in these areas, the prevention of environmental impacts associated with microalgal production would be required.…”

“…These systems are a promising alternative for future biofuel production (Aro, ), primarily because they need less land for producing the same amount of energy compared to first‐generation biofuels, and additionally because they do not need fertile soils for their cultivation (Chisti, ; Correa et al, ; Mata et al, ; Quinn & Davis, ; Schenk et al, ). These advantages could decrease direct competition with agricultural and biodiverse lands, leading to lower competition with food production and reduced habitat loss for native species (Correa et al, ), or free lands for further agricultural production, ecological restoration, and biodiversity conservation (Walsh et al, ). While technological advances in the cultivation, harvesting, and conversion of microalgae into biofuels increase the cost‐effectiveness and sustainability of microalgal production systems (González‐González et al, ; Mu et al, ; Uggetti, Sialve, Trably, & Steyer, ; Venteris, Skaggs, Wigmosta, & Coleman, ; Yang et al, ), further steps are needed to identify the most profitable areas for microalgal biofuel production without competing for arable lands or biodiverse landscapes.…”

“…However, first-generation biofuels, which derive from food crops (e.g., maize, sugarcane, soybean, and oil palm), compete with food production (Pimentel et al, 2009;Tilman et al, 2009) and drive environmental degradation (Correa, Beyer, Possingham, Thomas-Hall, & Schenk, 2017;Fargione, Hill, Tilman, Polasky, & Hawthorne, 2008;Fargione, Plevin, & Hill, 2010;Immerzeel, Verweij, Hilst, & Faaij, 2014;Searchinger et al, 2008), directly competing for agricultural lands and leading to habitat loss for native species (Correa et al, 2017;Fargione et al, 2010;Immerzeel et al, 2014;Koh, 2007;Koh, Miettinen, Liew, & Ghazoul, 2011). Furthermore, they have been linked to increases in CO 2 emissions after carbon-rich systems (e.g., forests and native grasslands) are transformed into biofuel monocultures, which can negate their potential for climate change mitigation (Fargione et al, 2008;Searchinger et al, , 2008.…”

“…At a projected population of nine billion people and a 60% increase in food demand by 2050 compared to 2006(FAO, 2016, biofuel systems not only need to offer climate change mitigation (IPCC, 2015) but also must have limited competition with food production and biodiverse lands (CBD, 2011;Foley et al, 2011). These goals could be achieved by increasing the productivity of first-generation biofuels and their coproducts (e.g., food and animal feed) within current production areas (IEA, 2017a;Souza, Victoria, Joly, & Verdade, 2015;Tomei & Helliwell, 2016) while preventing their expansion into agricultural lands and biodiverse regions (Foley et al, 2011;Souza et al, 2015), coupled with the adoption of systems that do not rely on arable lands (e.g., wastes and microalgae) (Correa et al, 2017;Tilman et al, 2009) able to gradually replace less sustainable biofuel production alternatives (Correa et al, 2019). Microalgal biofuel production systems (i.e., third-generation biofuels) are based on the cultivation of prokaryotic and eukaryotic photosynthetic microorganisms (i.e., microalgae) in recirculation channels open to the atmosphere (i.e., open ponds) or in enclosed culture devices (i.e., photobioreactors), making use of water (fresh, brackish, or saltwater) and nutrients (Chisti, 2007;Lundquist, Woertz, Quinn, & Benemann, 2010;Mata, Martins, & Caetano, 2010;Schenk et al, 2008).…”

The challenging paradigm of interrelated energy systems towards a more sustainable future

“…GHG emissions of bioenergy systems have been the focus of many research studies [423], [424], and recently other relevant environmental impacts have been assessed, including those deriving from Land-Use Change (LUC) [425][426][427], and the impacts on biodiversity, water resources, water, air and soil quality [428][429][430]. In addition, it is of importance to consider social-economic impacts of bioenergy together with environmental impacts when assessing sustainability of bioenergy production [431].…”