Exploring the sustainability and sealing mechanisms of unlined ponds for growing algae for fuel and other commodity-scale products

Pond liners for large-scale cultivation of algae for biofuels and bioproducts are a significant source of capital cost and greenhouse gas emissions, both of which can be reduced by using unlined ponds. Concerns about using unlined ponds to cultivate algae focus on the potential for water and nutrient leakage and biological contamination. We review studies of sustainability and physical and biological sealing of unlined ponds and discuss the potential for use of unlined ponds for algae cultivation for commodity products, such as biofuels. Evidence from animal waste disposal, aquaculture, and algae cultivation shows that soils below ponds can develop self-sealing layers at the soil-water interface, termed bioclogging, which provides a solid basis for technology transfer to algae cultivation. The concept of unlined ponds for algal biofuels and bioproducts is tenable and deserves future research to further define acceptable environments for the use of unlined ponds. Further research is needed to determine the viability and longevity of self-sealing, unlined freshwater and saline algae ponds in various soils; the potential effects of the technology on algal productivity and biological contamination; and performance and economic outcomes from combining self-sealing ponds with limited deployment of liners.