(128a) Design of Sustainable Biofuel Supply Chains While Accounting for Spatial Variability of Nutrient Runoff and Ecosystem Services

With increasing demand of biofuels for fulfilling energy requirements, design of sustainable supply chains for sourcing agricultural biomass for feeding such biorefineries is highly essential. There exists a large amount of literature for design of these supply chains with specific focus on biomass availability. Life cycle assessment has been utilized to determine environmental impacts of resultant supply chain design. However, most life cycle inventories do not consider spatial variation of impact. Most biofuel supply chain studies use county level harvesting and corn availability data. Along with that, literature review reveals none of the biofuel supply chain studies have considered the impact of biomass production on waterbodies resulting in harmful algal blooms and eutrophication.

Objective:

In this research work, spatial variability of biomass availability, nutrient runoff as well as ecosystem services is considered while designing supply chains as well as manufacturing processes. A matrix based mathematical framework that uses upstream process based life cycle network as a platform for supply chain design is developed that can perform process design of industrial manufacturing technologies such as biomass to fuel conversion as well as design the upstream supply network of raw materials and downstream movement of finished products. An added novelty of the framework is that it allows incorporation of ecosystem services as unit operations during optimization as a measure of environmental sustainability and designing of ecological systems.

Background:

Sustainable Process Design (SPD) is used to design manufacturing processes while accounting for environmental impacts as an optimization objective along with conventional objectives such as profit or production quantity. {1} Process to Planet (P2P) framework is applied to perform SPD which calculates environmental impact using a hybrid approach to life cycle assessment. {2}

Techno-Ecological Synergy: The Techno-Ecological Synergy (TES) framework {3} considers supply of ecosystem services while satisfying the environmental sustainability condition of maintaining that demand of ecosystem services by technological systems does not exceed the capacity of ecosystems to provide the same.

Approach:

Process design, supply chain design (SPD), technology choices, hybrid life cycle assessment (LCA) as well as ecosystem services are integrated in a comprehensive optimization model to design biofuel supply chains. It is achieved by utilizing the P2P-TES framework that combined the sustainable process design and hybrid LCA characteristics of P2P with the ecosystem service integration of TES. A major novelty of this study is the use of Soil and Water Assessment Tool (SWAT) at spatial resolution of 12 digit Hydrological Unit Codes (HUCs). These models provide detailed information about biomass yield and nutrient runoff from watersheds which are used in the design framework.

Results:

The case study for designing sustainable supply chains is based in the watershed of the Maumee river that drains into Lake Erie. Agriculture in this river’s watershed has been determined to be one of the leading causes for harmful algal blooms in the lake. A SWAT model of the Maumee river watershed is used to simulate corn farming, fertilizer application, biomass yield and nutrient runoff for a ten-year time period. Using ArcGIS databases, information about availability of trucks and railway transportation modes are explored. Information about grain elevator locations are obtained from intermodal facilities database. Using these data, we perform a sustainable supply chain design study to determine the distribution of biorefineries within a spatial region, design the corn-to-bioethanol conversion process and simultaneously determine upstream raw material network while considering tradeoff between food – energy and water quality. Solving for minimization of nutrient runoff, the design solution chooses farms with lower runoff to yield ratio. Wetland ecosystems are incorporated within the design framework for treating nutrient run off from corn farms in the region. With wetlands, we get counterintuitive solutions of choosing farms that have unsustainable nutrient runoff values, but have the available land area for constructing large wetlands for phosphorus removal.

References :

(1) Bakshi, B. R., “Methods and tools for sustainable process design, “Current Opinion in Chemical Engineering, vol. 6, pp. 69–74, 2014. [Online]. Available: http://linkinghub.elsevier.com/retrieve/pii/S2211339814000768

(2) Hanes, Rebecca J., and Bhavik R. Bakshi. "Sustainable process design by the process to planet framework." AIChE Journal 61.10 (2015): 3320-3331.

(3) Bakshi, Bhavik R., Guy Ziv, and Michael D. Lepech. "Techno-ecological synergy: A framework for sustainable engineering." Environmental Science and Technology Letters 49.3 (2015): 1752-1760.

(4) Ghosh, Tapajyoti, and Bhavik R. Bakshi. "Designing Biofuel Supply Chains while Mitigating Harmful Algal Blooms with Treatment Wetlands." Computers & Chemical Engineering(2019).