Work Authorization to develop a white paper on the potential application of using the steam hydrogasification process to convert biomass materials prevalent in Southern California into synthetic fuels
This study is performed by the College of Engineering – Center for Environmental Research and Technology (CE-CERT) at the University of California, Riverside at the request of the California Energy Commission. The objectives are to evaluate the availability of biomass feedstocks in the Southern California region that can be used for synthetic sustainable fuel production using the thermochemical conversion technology developed by CE-CERT. The report presents five feedstocks that have been identified as the most suitable and also the energy production and process economics assessments for potential production facilities using these feedstocks. A full life cycle analysis has also been performed. The biomass availability assessment has been performed for the entire state of California with an emphasis on Southern California. The estimates show that every year California generates 40.8 million dry tons of biomass and Southern California generates 10 million dry tons of biomass that can be effectively used for fuel production. The biomass available in the state of California can potentially yield 30 million barrels of Fischer-Tropsch (FT) diesel and 9.5 million barrels of naphtha per year. This sulfur free FT diesel can replace approximately 41% of the transportation diesel fuel consumed by California every year. Based on the biomass availability estimates for Southern California, wood residue/waste (pine, cedar), chaparral, paper/cardboard, biosolids and field residue (rice straw) have been selected as the target feedstocks for further study. These preferred feedstocks account for 4.7 million dry tons of biomass feedstocks every year. FT diesel (FTD) and electricity cogenerated along with FTD have been chosen as the target fuels. Two configurations of the CE-CERT process that can maximize these products have been analyzed in detail using computer simulation. Process economics have also been estimated for potential facility sizes of 400 dry Ton Per Day (TPD), 1000 TPD and 4000 TPD. The internal rates of return for small 400 TPD plants vary from 0.8 % to 12.1 % depending on economic variables. The internal rates of return varied from 10 % to as high as 41 % for the 1000 TPD and 4000 TPD plants. It appears that a 1000 TPD facility would be optimum based on feedstock density in most areas of Southern California. Additional scenarios were considered, in particular, a combination of hydrogen for use in fuel cell vehicles and FTD would be attractive in some areas. Laboratory scale gasification experiments of the target feedstocks have been performed at different temperatures using a stirred batch reactor system and high carbon conversions were observed for all of the feedstocks. A full fuel cycle analysis using a generic biomass feedstock in the CE-CERT process has been performed. The results are compared with other fuel/vehicle pathways such as petroleum based gasoline, diesel, cellulosic ethanol, hydrogen and electric vehicles. The results show that FT diesel produced using the CE-CERT technology results in the largest green house gas emission reductions per mile driven. The study demonstrates that there is enormous potential for replacing a significant portion of petroleum base transportation fuels using renewable feedstocks, especially carbonaceous waste streams that are typically sent to land fills. This can result in significant reduction in greenhouse gas emissions, reduced fossil fuel usage and can also mitigate the various problems associated with the disposal of these waste streams. Based on the results of this report, a Process Demonstration Unit (PDU) scale gasifier using a comingled feedstock containing biosolids and biomass (green waste or wood) is proposed as the next step. The operation of this gasifier will provide the information necessary for the construction of a commercial or near commercial scale facility that produces sustainable synthetic fuels from carbonaceous waste streams.