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Environmental impacts and limitations of third‐generation biobutanol: Life cycle assessment of n ‐butanol produced by genetically engineered cyanobacteria
Author(s) -
Nilsson Astrid,
Shabestary Kiyan,
Brandão Miguel,
Hudson Elton P.
Publication year - 2020
Publication title -
journal of industrial ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.377
H-Index - 102
eISSN - 1530-9290
pISSN - 1088-1980
DOI - 10.1111/jiec.12843
Subject(s) - biofuel , life cycle assessment , greenhouse gas , butanol , fossil fuel , environmental science , photosynthesis , bioenergy , n butanol , pulp and paper industry , sustainability , productivity , waste management , microbiology and biotechnology , environmental engineering , chemistry , production (economics) , botany , biology , ecology , engineering , organic chemistry , ethanol , economics , macroeconomics
Photosynthetic cyanobacteria have attracted interest as production organisms for third‐generation biofuels, where sunlight and CO 2 are used by microbes directly to synthesize fuel molecules. A particularly suitable biofuel is n ‐butanol, and there have been several laboratory reports of genetically engineered photosynthetic cyanobacteria capable of synthesizing and secreting n ‐butanol. This work evaluates the environmental impacts and cumulative energy demand (CED) of cyanobacteria‐produced n ‐butanol through a cradle‐to‐grave consequential life cycle assessment (LCA). A hypothetical production plant in northern Sweden (area 1 ha, producing 5–85 m 3 n ‐butanol per year) was considered, and a range of cultivation formats and cellular productivity scenarios assessed. Depending on the scenario, greenhouse gas emissions (GHGe) ranged from 16.9 to 58.6 gCO 2 eq/MJ BuOH and the CED from 3.8 to 13 MJ/MJ BuOH . Only with the assumption of a nearby paper mill to supply waste sources for heat and CO 2 was the sustainability requirement of at least 60% GHGe savings compared to fossil fuels reached, though placement in northern Sweden reduced energy needed for reactor cooling. A high CED in all scenarios shows that significant metabolic engineering is necessary, such as a carbon partitioning of >90% to n ‐butanol, as well as improved light utilization, to begin to displace fossil fuels or even first‐ and second‐generation bioethanol.