Green Engineering was the focus for the 2021 Akers Design Competition, more commonly referred to as the “Senior Design Project”. For 2021, senior CHBE design teams were looking to solve contemporary chemical engineering problems by incorporating green engineering.
This year the teams’ goal was to achieve process intensification using smaller, more energy-efficient units while minimizing waste generation without sacrificing performance. Potential projects for 2021’s Class ranged from developing a more sustainable process for the production of isopropanol to converting hurricane debris into useful fuel products.
The winning team for the 2021 competition, named Team Plant Based Plant, was tasked with creating a process to produce methyl tetrahydrofuran from agricultural residues.
Employing biomass as a source of energy has recently been of great interest. Energy originated from biomass has grown in appeal with the desire to address Global Warming by shifting away from utilizing oil as an energy source. Biofuels can function as a greener alternative to typical methods of extracting and producing fossil fuels, as their production does not contribute to the increases in carbon emissions worldwide. One platform from which to derive biofuels is furfural, a product of xylose that can be extracted from agricultural residues like wood chips or corn stover. Furfural can react to produce compounds such as methyl tetrahydrofuran (MTHF), a Department of Energy-approved fuel additive. Thus, the production of MTHF offers a sustainable option to decrease our dependence on traditional gasoline.
CHBE Senior Design Projects require complete designs, not just a process flow diagram. Thus, each team must prepare a basic plant design and configuration addressing such parameters as location, availability of necessary feedstocks, supporting utilities, etc. The first step for Team Plant Based Plant, was to select a plant location and desired biomass feedstock. The ideal feedstock for the selected process is one high in hemicellulose content as that is the precursor to the desired final product. The two agricultural residues with the highest hemicellulose content are corn stover and sugarcane bagasse. Due to the limited production season for corn stover, sugarcane bagasse was selected as the biomass feedstock. As this project was a “world view” project, potential locations were not limited to the Continental US. Brazil was selected as the best option due to its tropical climate, making sugarcane bagasse available the majority of the year. With the plant location and feedstock identified, Team Plant Based Plant moved forward to process design.
The design comprised of three main processes: processing the biomass feedstock into lignin, conversion of hemicellulose into furfural, and conversion of furfural into MTHF. Key features of the plant design include a screw conveyor reactor to separate the three components of the biomass feedstock, a recovery boiler to promote heat recovery by burning the lignin, an acid-catalyzed biphasic reactor to maximize the conversion of xylose into furfural, and two fixed bed reactors to produce as much MTHF as possible. This design achieves a 70 mol % conversion of xylose to furfural and a 99 mol % conversion of furfural to MTHF.
Once the plant process design was completed, the team evaluated their design from an economic standpoint, which involved examining the project’s net present value (NPV), internal rate of return (IRR), and the discounted payback period. These metrics were examined across different feed locations and feedstocks to ensure the selected design maximized profitability. Based on a yearly biomass feedstock combination of nine months of sugarcane bagasse, supplemented by 3 months of softwoods (available year-round), and a processing rate of 1,000 tons/day, the design can achieve an NPV of 44 million dollars and an IRR of 30% with a payback period of 5 years.
Team Plant Based Plant, composed of team members Morgan Alana, Christopher Botello, Lauren Chiang, and Patrick Eifert, created an environmentally sustainable and profitable process that is adaptable to many different scenarios of feedstock. By using agricultural residues and taking advantage of byproducts to create energy utilized in the production of the desired end product, the design fulfills this year’s Akers Competition goal of incorporating green engineering in the completed design.