Table 4.

Studies associated with the techno-economic and life cycle assessment of hydrogenolysis of glycerol to propylene glycol

Technology	Study objectives	Key findings	References
Route 1: Isothermal hydrogenolysis at high pressure and external hydrogen Route 2: Non-isothermal hydrogenolysis at ambient pressure and external hydrogen. Route 3: Isothermal hydrogenolysis at high pressure and in situ generated hydrogen	Petroleum-derived propylene oxide production method was compared with three different hydrogenolysis routes.	•Route 2 appears to be the most promising from economic and environmental considerations. •Factors such as prices of products, raw material cost, raw material conversion, and feed flow rate have a major impact on the profitability.	Gonzalez-Garay et al., (2017)
Route 1: Propylene glycol production from petroleum-derived feedstocks Route 2: Hydrogenolysis with glycerol from fatty acid production. Route 3:Hydrogenolysis with glycerol from biodiesel production.	Environmental effect of implementing different feedstock for renewable propylene glycol production.	A transition from petroleum-based economy to renewables-based results in a decrease in the environmental impact between 40% and 60% kg CO2 eq.	Nachtergaele et al., (2019)
Route 1: Hydrogenolysis with hydrogen from an external source. Route 2: Hydrogenolysis with hydrogen produced locally from glycerol steam reforming.	Assess the technical and economic impacts of two renewable propylene glycol production routes based on the source of hydrogen.	•An overall cost of production of 1.17 US$/kg was obtained from route 1. •Route 2 led to an increase in the hydrogen production cost to 9.01 US$/kg.	Jiménez et al., (2020)
Hydrogenolysis of crude glycerol with external hydrogen	Evaluate the economic viability combined acrolein and propylene glycol production from crude glycerol	Net present value of USD 376,600,000 was obtained from the production process.	Supramono and Ashshiddiq, (2021)
Route 1: Catalytic hydrogenolysis with external hydrogen Route 2: Catalytic transfer hydrogenolysis	Assess the energy economic and environmental impacts of the two propylene glycol production pathways.	•The overall energy input for route 2 is about 83% of route 1 process. •Route 1 is better in terms of economic and environmental impacts.	Sun et al., (2022)