The economic and environmental disadvantages of fossil fuels have led to increased efforts in finding alternative resources to fulfill energy and chemical needs. Following biotechnological advancements in recent decades, bioeconomy emerges as a paradigm to overcome this challenge. In this respect, current efforts are concentrated on (i) relevant research and development on large-scale feasibility, and (ii) enabling policies for bioeconomy practices such as integrated waste valorization and biorefining options.
Duckweeds (Lemnaceae) are efficient aquatic plants for wastewater treatment due to their high nutrient uptake capabilities and resilience to severe environmental conditions. Combined with their rapid growth rates, high starch, and low lignin contents, duckweed could be used as a feedstock for bioprocessing into fuels and chemicals in a biorefinery system. This work evaluates the viability of an integrated wastewater treatment, aquatic plant production, and biorefining process through a series of lab-scale experiments, techno-economic analysis and life cycle assessment.
One barrier in establishment of integrated biorefineries is the lack of policy coherence. In this respect, determination of where bioeconomy stands within sustainability frameworks is essential. This research identifies the synergies that bioeconomy brings among Sustainable Development Goals of the United Nations (SDGs), via brief meta-analysis of related literature.
Experimental studies show that sequential anaerobic bioprocessing of duckweed into ethanol, carboxylates, methane, and soil amendment in a biorefinery system is feasible, with a highest valorization potential of 0.69 gram total bioproduct carbon per gram of duckweed biomass carbon. Techno-economic analysis simulates duckweed yield as 51 dry Mg per hectare, over an area of 141 hectare, fed with municipal wastewater primary effluent. Discounted cash flow analysis reveals a minimum biomass selling price of $25 per dry Mg and a minimum ethanol selling price of $8.2 per U.S. gallon. Life cycle assessment of the base case scenario shows that the recovery of nutrients from wastewater into duckweed biomass produces a net benefit on reducing eutrophication potential, and poses a trade-off on land use due to pond area. In the policy context, considering the current bioeconomy links with SDGs literature, integrated duckweed systems would fall into the cluster of SDGs related to research and innovation (SDG12), water and sanitation (SDG 6), sustainable cities (SDG 11), and knowledge generation (SDG 4), along with strong links to affordable energy (SDG 7) and human health (SDG 3).
By: Dr. Ozgul Calicioglu, Consultant at the Food and Agriculture Organization of the United Nations (FAO), Climate and Environment Division, the Energy and Bioeconomy Team.
Date: 24.04.2019