Design and evaluation of biomass utilization systems

Abstract

This thesis designs and evaluates systems to utilize two problematic biomass sources, hurricane debris and invasive water hyacinth, and turn costly cleanup efforts into opportunities for biofuel conversion systems. A novel solution is proposed for each biomass source and techno-economic models accounting for economic, energy, and carbon costs are used to evaluate different options for utilization. Hurricane debris is a feedstock that gets generated in vast quantities in an unpredictable manner, thus its main challenge is its supply chain. We propose a 30MW barge-mounted biofuel conversion system, which travels to hurricane-hit ports and converts debris into biofuels. For a 30MW plant, the break-even per-gallon revenue for profitability was found to be $5.28 per gallon of jet fuel for Fischer-Tropsch synthesis, $0.88 per gallon of heating oil for pyrolysis, and $1.07 per gallon of ethanol for fermentation.

Using May 2019 US national fuel prices, the pyrolysis and fermentation plants were found to operate at a profit of $363.87 and $166.40 per dry ton of consumed hurricane debris respectively. A supply chain model was also created to calculate debris transport costs and evaluate the economic benefits of chipping debris directly in the field, which was found to be 24% more efficient than status quo stationary chipping operations. Water hyacinth is generated predictably and in huge quantities; however, the weight of water hyacinth is up to 95% water and it is thus inefficient to work with. Thus, we propose a novel roller-crusher harvester which grabs, crushes, and directly bags aquatic plants into digesters in-situ on the water. We find that an anaerobic digestion system with the proposed mechanical harvesting system could make a profit of $5.81 per ton of hyacinth, turning a costly problem into an economic opportunity.

Hardware designs, prototypes, and on-water tests then show the viability of the roller-conditioner as a boat-mounted in-situ harvester-crusher. Ultimately, this work shows that careful design and evaluation of utilization systems could turn government aid and charity spent every year on debris and waterway cleanup into a profitable investment.