Impacts of fungal disease on algal biofuel systems: Using life-cycle assessment to compare control strategies.

While the global community is looking for more sustainable sources of energy to combat climate change, algae has positioned itself as a both promising and problematic biofuel feedstock. On one hand, algae have higher photosynthetic efficiencies and higher lipid proportions than terrestrial crops and don’t compete for arable land. On the other hand, a major challenge to algae becoming an economically viable option is its vulnerability to diseases that lead to highly variable production output. Fungal pathogens are one of the most common forms of disease that cause algal feedstocks to crash. In turn, crashes of feedstocks cost significant losses of time and resources. Despite disease being a major bottleneck to commercial production, the life cycle assessments (LCA) used to analyze the viability of algal feedstocks for biofuel have yet to consider the impact of pathogens on life-cycle metrics. Here, we incorporate a disease model into a well-documented LCA for algal biorefineries to compare two sustainability metrics, energy return on investment (EROI) and global warming potential (GWP). We begin by showing the obvious – that failure to consider disease leads to overly optimistic LCA metric outputs. We then go on to compare two different control strategies of disease – chemical and biological. Our analyses show that biological engineering of a multi-species consortium of algae has a greater positive impact on LCA metrics than chemical control of the fungal pathogen using a fungicide. In fact, the addition of a second algal species to a disease susceptible monoculture, when able to engage in interspecies competition, can improve EROI by 68% compared to the 41% improvement of simply applying the most effective fungicide over a 1-year time frame. Biologically engineered algal bi-cultures are advantageous because of what is called the ‘dilution effect’ whereby species that are differentially susceptible to disease exhibit compensatory dynamics that stabilize feedstock production. Collectively, our results emphasize the importance of considering the impacts of disease on algal feedstocks, and suggest that mixed species algal feedstocks can be biologically engineered to reduce greenhouse gas emissions and improve economic viability of biofuel.Master of ScienceSchool for Environment and SustainabilityUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/174092/1/Miyasato_Elena_Thesis.pd