Environmental sustainability of emerging algal biofuels: A comparative life cycle evaluation of algal biodiesel and renewable diesel

Abstract

Holistic evaluation via a life cycle based approach is critical for guiding the environmentally conscious development of emerging microalgal biofuel pathways. This study models the energy return on investment (EROI) and life cycle greenhouse gas (GHG) emissions for producing algal derived biodiesel and renewable diesel under different production pathways—consisting of a combination of algal cultivation, harvesting, extraction, and coproduct utilization scenarios. The results indicate that in the base‐case scenario(s) the EROI for microalgae fuels range from 0.26 to 1.20 with GHG emissions ranging from 50 to 240 gCO2 equivalent/MJ‐fuel depending on the choice of cultivation variables, coproduct utilization options, and processing technologies. In the improved scenario(s), algal fuels have an EROI ranging from 0.81 to 2.01 and GHG emissions ranging from 30 to 90 gCO2 eq./MJ‐fuel. Furthermore, improved scenarios with favorable EROI and GHG emissions profile for microalgal biofuels are plagued with high technological uncertainty. This suggests that broad advances in algal technologies are required if algal fuels are to be competitive with other leading second generation and advanced biofuels. The choice of fuel conversion technology was found to have a comparatively small impact on overall life‐cycle energy use and GHG emissions. Therefore, the choice of fuel product may be based on other criteria such as fuel storage stability and compatibility with transportation fuel infrastructure. © 2013 American Institute of Chemical Engineers Environ Prog, 32: 926–936, 2013

Carbon capture, storage and utilisation technologies: A critical analysis and comparison of their life cycle environmental impacts

“…Sixteen LCA studies have been conducted for various CCU options to date globally [6,12,38,51,[54][55][56][57][58][59][60][66][67][68][69][70]. Similar to the CCS studies, most have considered fossil-fuel power plants as a source of CO 2 with only three studying the use of CO 2 from chemical plants such as ammonia and hydrogen production [51,60,66].…”

Ultrasound Applications in Lipid Extractions from Microalgae

“…Solar drying has been considered as an alternative but the long processing time and high land requirement make the process not feasible at a large scale. Waste heat drying, the use of heat produced by burning the residual microalgal biomass after oil extraction, has also been suggested as a sustainable drying method [6]. The capability of "recycling" heat provides a good potential to significantly bring down the energy depletion potential of the harvesting process.…”

“…The CO 2 can be provided from either direct injection of flue gas or monoethanolamine scrubbing. Direct injection of flue gas was reported to be the most economical method [6].…”

“…The residual microalgal biomass can also be utilized via combined heat and power (CHP) to produce heat and electricity [6]. The electrical and thermal efficiency of the CHP plant were assumed to be 25 and 56.3 % respectively.…”

Design of Sustainable Biofuel Processes and Supply Chains: Challenges and Opportunities

“…This holistic systems approach captures environmental impacts that are outside the purview of the traditional process design boundary. Life Cycle Assessment (LCA) is one of the most common approaches for evaluating the environmental impact of a product or a process over its entire life cycle, and in recent years has emerged as the predominant method for analyzing the environmental sustainability of emerging biofuel platforms [88][89][90][91][92][93][94][95]. LCA considers impacts throughout all stages of the fuel life cycle-from raw material acquisition, to fuel conversion, and final use.…”