# Greenhouse Gas Impact of Algal Bio-Crude Production for a Range of CO2 Supply Scenarios  
[PERSON] 1,2,*  
1 Department of Hydro and Renewable Energy, Indian Institute of Technology-Roorkee, Roorkee 247667, Uttarakhand, India 1  
[PERSON] 3  
1 Department of Hydro and Renewable Energy, Indian Institute of Technology-Roorkee, Roorkee 247667, Uttarakhand, India 1  
[PERSON] 4  
1 Department of Hydro and Renewable Energy, Indian Institute of Technology-Roorkee, Roorkee 247667, Uttarakhand, India 1  
[PERSON] 5  
1 Adaron, 1  
[PERSON] 2  
1 Department of Hydro and Renewable Energy, Indian Institute of Technology-Roorkee, Roorkee 247667, Uttarakhand, India 1  
[PERSON] 3  
1 Department of Hydro and Renewable Energy, Indian Institute of Technology-Roorkee, Roorkee 247667, Uttarakhand, India 1  
Footnote 1: email: [EMAIL_ADDRESS]  
Footnote 2: email: {[[https://github.com/journals](https://github.com/journals)]([https://github.com/journals](https://github.com/journals))  
assessment (LCA) for algal biofuel production through the hydrothermal liquefaction (HTL) route for five different locations, namely, Brazil, UK, Spain, China, and Australia. The study predicted significant savings in greenhouse gas (GHG) emissions associated with algal biofuels; these savings depended strongly upon the energy mix of the country, and the source of supply of CO2 was omitted. [PERSON] et al. [5] have performed LCA of biofuels production from microalgae through different conversion routes. The CO2 sourced from industrial flue gases is not considered within the system boundary. A majority of studies have failed to integrate CO2 delivery while assessing the sustainability of an algal biorefinery. Few studies consider losses from the CO2 injection system. [PERSON] et al. [6] have highlighted the excessive energy requirements for long-distance CO2 delivery from power plants. [PERSON] and [PERSON] [6] have reported the global warming potential (GWP) for bio-crude production from different CO2 supply routes. A recent study by [PERSON] et al. [7] has compared the production of microalgae for non-energy purposes from two different CO2 sources. [PERSON] et al. [8] have quantified the GHG emissions from hydrothermal treatment of algae utilizing CO2 from the conversion of biomass feedstocks. They have considered the CO2 production process within the LCA system boundary. Additionally, these studies do not incorporate the diurnal requirement of CO2 for algae growth. The algae growth is expected to take place during the daytime, and the CO2 source needs to be synchronized with the algae growth cycles. A variety of CO2 supply strategies have been proposed [9; 10]. Most of the predicted CO2 supply chains are linked to power plants, both new and existing. Alternately, there are several direct air capture (DAC) technologies to extract CO2 directly from the air, which may then be utilized by any CO2 utilization process [11; 12; 13]; as yet there has been no linking of DAC with an algae-based biofuel production process. Another novel integration is the use of biomass feedstock for supplying CO2 to the biorefinery. The sourcing of CO2 from a renewable and biogenic source has the potential for rendering the whole process carbon negative. A recent simulation study by [PERSON] and [PERSON] [14] points out the necessity of integrating the algae HTL with upstream and downstream processing streams. To overcome the above mentioned challenges, the present study focusses on HTL of algae to produce refined bio-crude, integrating upstream CO2 supply with downstream hydro-treating and hydro-cracking of bio-crude. GHG emissions are quantified for an envisioned 2000 accre algae growth facility to be located in southwest Florida, US. The algae feedstock is produced in photo-bioreactors (PBRs), utilizing a process and design developed by Algenol Biotech [15; 16]. The HTL-oil can potentially be fed into conventional crude refineries after hydro-treating, which would remove excess oxygen and nitrogen in the bio-crude. The HTL process also results in an aqueous phase.