A Techno-Economic and Life-cycle Assessment of the Production of Fuels and Chemicals from Biomass

Abstract

The greenhouse gas (GHG) emissions footprint of Alberta’s oil sands industry is one of the industry’s most arduous environmental challenges. Alberta’s oil sands industry uses chemicals such as diluent to reduce the viscosity of bitumen to ease its transportation through pipelines. The oil sands industry also relies on fuels such as hydrogen to process heavy hydrocarbons like bitumen into synthetic crude oil. Presently, the leading hydrogen production technology is steam reforming with the help of natural gas. Moreover, hydrocarbon-based diluent and hydrogen production are known to be highly energy-consuming processes that contribute significantly to GHG emissions, causing global warming. Using biomass resources rather than hydrocarbons to produce diluent and hydrogen is an alternative and environmental friendly approach to reduce GHG emissions while still providing useful products to the oil sands industry. Moreover, hydrogen can be used in the transportation, petrochemical, and manufacturing industries. However, more data are required on the most suitable technologies and processes from biomass and also on production costs and GHG emissions. In this research, a comprehensive techno-economic model and a life cycle assessment of various conversion pathways, including hydrothermal liquefaction and fast pyrolysis to diluent, as well as supercritical water gasification and thermal gasification to hydrogen, are developed for the heavy hydrocarbon industry in Western Canada. This analysis includes developing data-intensive economic models to estimate the production cost of hydrogen and diluent from biomass sources through a range of thermochemical conversion pathways. The factors that have the greatest influence on the production costs of hydrogen and diluent are further assessed via sensitivity and uncertainty analyses. An environmental assessment of diluent and hydrogen production is performed through a life cycle assessment that includes developing GHG emissions estimates, as well as comparing different ways of producing desired products. A study on the hydrothermal liquefaction (HTL) of various biomass sources to diluents at a 2000 dry tonnes/day plant capacity resulted in product value of 0.79 - 1.60 $/L. The sensitivity analysis showed that diluent yield, internal rate of return (IRR), and biomass cost had the most on the product value of the diluent. Subsequent study on the economic impacts of microalgae for diluent production through fast pyrolysis for a 2000 dry tonnes/day plant resulted in product value of 1.69 $/L. For hydrogen production, a techno-economic study through algal supercritical gasification and thermal gasification for 2000 dry tonnes/day plant resulted in product values of 4.59 ± 0.10 $/kg and 5.66 ± 0.10 $/kg, respectively. The sensitivity analysis indicated that biomass cost and yield were the most sensitive parameters in the economics. Hydrogen production through bio-oil reforming via hydrothermal liquefaction was assessed followed by techno-economic assessment and associated sensitivity and uncertainty analyses. A processing plant with a capacity of 2000 tonnes/day of dry biomass had a product value of 2.84 ± 0.10 $/kg. The emission results showed that HTL performed better than pyrolysis for diluent production, while HTG had better environmental metrics than thermal gasification for hydrogen production from biomass. The production of diluent from HTL has advantages with the use of high moisture containing microalgae; this technology can reduce energy and corresponding emissions pertaining to microalgal drying. This study provides the requisite information required to explore the technological and economic competitiveness of producing diluent and hydrogen using biomass. The development of such technology can potentially reduce GHG emission loads from the oil sands and help make the industry environmentally friendly.