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Title:The co-cultivation of rice and algae to improve process economics for algal biofuel production
Author(s):Mazur, Zachary M.
Advisor(s):Schideman, Lance C.
Contributor(s):Davidson, Paul; Zhang, Yuanhui; Wilkinson, Henry
Department / Program:Engineering Administration
Discipline:Agricultural & Biological Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Abstract:Fossil fuels are becoming more and more scarce as the demand for them increases with an increasing population. One way to meet these demands is by increasing the production of fuels from algae. Algal biofuels are currently limited by high costs for land, cultivation ponds, nutrients, and labor resulting in a total cost of 10.9 dollars/gallon of gasoline equivalent (gge-1) according to Lundquist et al., (2010). These can be mitigated by integrating the cultivation of algae with rice and/or by using wastewater as a source of nutrients for rice and algae production. Some algae growth already occurs naturally within a rice field, and it serves as a fertilizer for the rice. This study proposes a co-cultivation system where the growth of algae is actively encouraged and then harvested and processed into a biofuel. Improvements in cost were made by using a plastic HDPE tarp as a way to make harvesting of algae easier, decreasing the overall volume for tanks, not supplying aeration, processing wet biomass into fuel via hydrothermal liquefaction, and using the same land that rice is being grown on. These changes result in a feedstock cost of 7.60 gge-1 before wastewater treatment credits. The amount of fuel potentially produced by this system was also investigated, experimentally. These experiments also quantified the simultaneous treatment of wastewater and the amount of rice grain produced in a co-cultivation system. The experiment was conducted with 4 treatments or approaches to rice cultivation and with 4 replicates of each treatment. The first, the baseline treatment: Water Plus No Plastic with a yield of 7.7 metric tons hectare-1. Another treatment tested the effect of an HDPE tarp: Water Plus Plastic which had a yield of 8.7 metric tons hectare-1. An additional treatment tested the effect of having wastewater and algae grow together: Swine Manure Lagoon Effluent Plus Plastic which had a yield of 7.9 metric ton hectare-1. The final treatment demonstrated the E2 Energy Process by integrating a wastewater produced during the experiment: Swine Manure Lagoon Effluent/Post Hydrothermal Liquefaction Wastewater Plus Plastic which had a yield of 10.3 metric tons hectare-1. All results were analyzed using ANOVA and post-hoc analysis was conducted using least significant difference (LSD) and Tukey’s honest significant difference (HSD) tests. These experimental results were used to determine the effect of co-cultivation on the rice yield. LSD analysis showed that the Swine/PHWW Plus Plastic treatment was statistically different compared to the baseline treatment of Water Plus No Plastic while HSD analysis determined it was not statistically different. Overall, it was determined that yields were at worst the same while there is potential for an increase in yield by using a Swine/PHWW mix since the LSD test determined significance. A credit for wastewater treatment is included and divided between the amount of nitrogen and BOD removed. The experimental results showed that the algae could remove up to 99% of ammonia, 92% of nitrate, and 90% of COD. This results in an overall treatment credit of $$4.50 gge-1 which means the total cost for biofuel production decreases to $3.10 gge-1. The amount of land area devoted to rice cultivation is large, and if this co-cultivation system was implemented in every rice field around the world, 36% of the world’s crude oil supply could come from algae grown in co-cultivation systems. This is a significant portion of the oil supply as biodiesel is currently providing less than 1% of the United States oil supply. A co-cultivation system like this could address multiple broad societal issues including the production of cost-effective biofuels on a large scale and improved water quality in agricultural areas.
Issue Date:2016-12-08
Rights Information:Copyright 2016 Zachary Mazur
Date Available in IDEALS:2017-03-01
Date Deposited:2016-12

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