Life cycle assessment of gasoline and diesel produced via fast pyrolysis and hydroprocessing

Abstract

Executive SummaryPyrolysis of biomass followed by hydroprocessing may provide infrastructure-compatible transportation fuels that present an advantage over bioethanol, which must be blended with gasoline for use in vehicles and does not address diesel demand. Recent studies analyzed the economics of pyrolysis-derived biofuels and suggested that these biofuels can be cost competitive with gasoline under "n th plant" assumptions. With these advantages, pyrolysis has garnered greater research attention. Despite this, there have been few life cycle assessments (LCA) estimating greenhouse gas (GHG) emissions and net energy value (NEV) of a pyrolysis process.In this work, an LCA of the production of gasoline and diesel from forest residues via fast pyrolysis and hydroprocessing, from production of the feedstock to end use of the fuel in a vehicle, is performed. The fast pyrolysis and subsequent hydrotreating and hydrocracking processes are based on a Pacific Northwest National Laboratory (PNNL) design report. Stages other than biofuels conversion, including forest residue production and harvesting, preprocessing, feedstock transportation, fuel distribution, and vehicle operation, are based on previous work. Probability distribution functions (PDFs) are assumed for key parameters involved in the pyrolysis process. These PDFs, along with PDFs previously used in other supply chain stages, are used as inputs for Monte Carlo uncertainty analysis.This preliminary LCA for the production of gasoline and diesel via pyrolysis and upgrading assumes grid electricity is used and supplemental natural gas is supplied to the hydrogen plant. Monte Carlo uncertainty analysis shows a range of results, with all values besting conventional gasoline in 2005. Grid electricity accounts for 27% of the net GHG emissions in the base case. A sensitivity using biomass-derived electricity shows significant improvement in GHG emissions. Further research to achieve the target fuel yields is needed to reduce the uncertainty of the GHG and NEV results. In addition, other sensitivities, such as biomass-derived hydrogen and reduction in electricity demand through process optimization, should be explored in tandem with their associated technoeconomics. . Ethanol also has a lower energy density than gasoline, which means that a vehicle travels fewer miles on a gallon of ethanol than on a gallon of gasoline. An infrastructure-compatible biofuel that substitutes for conventional gasoline or diesel would overcome these shortcomings.One way to produce infrastructure-compatible biofuels is through fast pyrolysis followed by hydrotreating and hydrocracking. In fast pyrolysis, biomass is rapidly heated to temperatures around 400°C to 500°C in the absence of oxygen, causing thermal decomposition of the biomass and ultimately resulting in a bio-oil. This bio-oil resembles crude oil in appearance but has higher oxygen content and is more acidic. To convert bio-oil to usable transportation fuels, the bio-oil is upgraded through hydrotreating and hydrocracking. In h...

Regional differences in the economic feasibility of advanced biorefineries: Fast pyrolysis and hydroprocessing

“…The economic feasibility of the fast pyrolysis and hydroprocessing pathway is sensitive to many of these factors individually (Brown et al, 2011a;Wright et al, 2010a), suggesting that it will also be sensitive to location, which affects all of these factors simultaneously. definition when lignocellulosic feedstock is utilized (Hsu, 2012). Qualifying as a cellulosic biofuel allows commercial-scale facilities employing the pathway to earn compliance commodities called Renewable Identification Numbers (RIN), which attach to each liter of cellulosic biofuel produced in or imported into the U.S. (Schnepf and Yacobucci, 2012).…”

Integrated biorefineries: CO2 utilization for maximum biomass conversion

“…Similarly, Fig. 9b shows the 'Well-to-Gate' (from biomass cultivation to fuels production) GHG emissions for diesel and gasoline in the present study compared to those in Hsu's study [93] for biomass-derived diesel and Frank, et al's study [76] for algae-derived diesel using OP system. It is found that GHG emissions factors for diesel in our PBR scenario are 65% and 64% smaller than those in Hsu, [93] and Frank, et al's [76] studies, respectively.…”

“…These results are compared with 'well-towheel' GHG emissions for diesel and gasoline reported by Hsu, [93] for stand-alone biomass pyrolysis process and that for refinery gasoline in Fig. 9a.…”

“…With regard to the utilisation of fuel in a passenger vehicle, 0.070 kg gasoline and 0.059 kg diesel are required to travel 1 km [93]. The GHG emissions occurr in vehicle operation when the passenger car travels 1 km, are 0.226 kg CO2 eq.…”

A Review of Life Cycle of Ethanol Produced from Biosyngas

“…In an updated study, ethanol produced by gasification of biomass reduced 65% of GHG emission with reference to gasoline if only the ethanol portion is considered. The GHG emission is estimated to be about 0.21 kg CO 2 eq./L ethanol produced in that updated study (0.01 kg CO 2 eq./MJ of ethanol; 21 MJ/L ethanol is assumed) [62]. Although the biorefinery system reduces CO 2 and CH 4 , releases more N 2 O emissions compared with a fossil fuel system thus has higher impacts in acidification and eutrophication [63,64].…”