Sinistore, J. and D. Reinemann
Presented at the All Scientist and GLBRC Sustainability Meeting (2009-05-05 to 2009-05-07 )
GaBi is a comprehensive modeling tool designed to allow the user to create custom models to account for greenhouse gas, energy, material and pollution flows through a system. Within the GaBi modeling environment, the complex biofuels production system can be divided into separately functional process models, which can then be nested into a hierarchy to form a complete model. For example, basic cellulosic ethanol production involves three major production stages: crop production and harvesting, pretreatment and ethanol bioconversion. An independently functional process model can be created in GaBi to model each of these three steps. Additional process models can be nested within each major step to explicitly model a component of the process such as fertilizer production within the crop production stage. The highest-level model in the hierarchy brings all of the individual process models together, yet any of the individual processes can be modified for sensitivity analysis or as new data become available without interfering with the interconnectivity of the model. We have chosen this modeling platform for LCA analysis because of its flexibility in tailoring the complexity of individual process models and the ability to combine process models with a wide range of quantitative methodologies. GaBi is an outstanding platform to facilitate collaboration among GLBRC scientists.
GaBi 4 features standard database and process models of common inputs and outputs, such as electricity, gasoline and diesel from various sources. These preloaded datasets and process models allow the user to quickly and easily assemble the basic structure of a product model, which can later be altered and expanded upon with research or area-specific data. Additional extension databases are available and feature industry specific data and process models. Of interest to this project are the Renewable Raw Materials and the EcoInvent Databases. The Renewable Raw Materials Database features 114 processes from fertilizers & pesticides, tractors and passes, agricultural equipment, industrial intermediate products to crops such as corn, wheat, hemp, flax, rape seat, soybean. This database also features industrial intermediate products for producing biopolymers and fuels. The EcoInvent Database consists of about 2500 unit processes and about 2500 calculated processes of different products and services from energy supply, chemicals, detergent ingredients, transport, agricultural products and processes. EcoInvent processes and products feature detailed data on associated greenhouse gas emissions (from all major greenhouse gasses), as well as air, water and soil pollution. Additional information available here.
Internal consistency checks, various analysis methods and a highly visual model construction process allow the user detailed control over the model and allow for high model transparency.
Cellulosic Ethanol LCA Modeling Variability:
There are many paths to choose from between feedstock and ethanol. Potential biomass feedstocks are innumerable. For the purpose of this study, we are focusing first on corn stover and switchgrass from southern Wisconsin and woody biomass from northern Wisconsin. Certain pretreatment methods are more appropriate for stover and switchgrass while other pretreatments work best with woody biomass. The pretreatment method chosen will determine the efficiency of sugar conversion to ethanol and the type and amount of usable co-product. For example, the AFEX (Ammonia Fiber Explosion) pretreatment method is more suitable for stover and switchgrass, but not suitable for hard or soft wood. A handful of pretreatment methods are suitable for hard and soft wood, but they each produce vastly different co-products whose value must be assess. For example, lignosulfonate is the coproduct of SPORL (Sulfite Pretreatment to Overcome Recalcitrance of Ligninocellulose) pretreatment of woody biomass and it has an established market value. In contrast, other woody biomass pretreatment strategies do not produce an economically viable lignin product, but instead the remaining lignin fraction could be burned to provide process heat. Finally, there are three major fermentation methods currently being researched for conversion of lignocellulose sugars into ethanol. This means that there are two main feedstocks (herbaceous and woody) each with three or more viable pretreatment strategies and three possible biological sugar conversion pathways and as it stands today, there are no commercial scale biorefineries on which this modeling can be based. All paths from feedstock to ethanol must be modeled with flexibility in process conditions as research changes our understanding of second-generation ethanol production.
Back to meeting | Show |