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Investigation of the disruption of algal biomass with chlorine

Garoma, Temesgen, Yazdi, Ramin E.
BMC plant biology 2019 v.19 no.1 pp. 18
algae, biofuels, biomass, carbon dioxide, cell viability, chlorine, cost effectiveness, energy efficiency, fossil fuels, fuel production, greenhouse gas emissions, scanning electron microscopy, specific energy
BACKGROUND: Algal biofuel has a potential for reducing dependence on fossil fuel while curbing CO₂ emissions. Despite these potential benefits, a scalable, sustainable, and commercially viable system has not yet been developed. One of the key barriers is the lack of viable methods for disrupting algal biomass for the separation and extraction of bioproducts. This study experimentally investigated the feasibility of using chlorine as an agent for algal biomass disruption. RESULTS: Chlorine was an effective agent for disrupting algal cell, as demonstrated with cell viability and SEM analyses. For disruption studies conducted using algal suspension at 0.02% solids (0.2 g/L), 90% of the algal cells were disrupted in 6 min at 10 mg/L chlorine dose. Moreover, the results demonstrated that the estimated specific energy requirement, specific cost, and GWP for chlorine were lower than those of the existing methods. The energy requirement for chlorine was 3.73 MJ/ kg of dry algae disrupted, while the requirements for the existing methods ranged from 33 to 860 MJ/ kg of dry algae. The GWP for chlorine was 0.3 kg CO₂-eq./kg dry algae, while for the existing methods it varied from 5.9 to 369.8 CO₂-eq./kg dry algae. Despite these advantages, it was observed that residual chlorine reacted with and mineralized the cell contents, which is undesirable. CONCLUSIONS: Future research efforts must be focused on eliminating or reducing the reaction of residual chlorine with cell contents. If this challenge is addressed, chlorine has a potential to be developed into an energy-efficient, cost-effective, and sustainable method for algal biomass disruption. This will in turn will overcome one of the technical bottlenecks, and ultimately increase algal biofuel production and reduce dependence on fossil fuel and curb CO₂ emissions.