Achieving net-zero CO2 emissions from indirect co-combustion of biomass and natural gas with carbon capture using a novel amine blend

Abstract

Due to the aggravating effect of climate change as a result of unprecedented levels of greenhouse gases, particularly CO2, in the atmosphere, the need to minimize CO2 emissions into the atmosphere has become very crucial. The energy sector remains the largest source of CO2 emissions, therefore, a technology which allows for achieving netzero CO2 emissions in this sector is imperative. This research work evaluated the possibility of achieving net-zero emissions (on the minimum) through the application of co-combustion of natural gas and biomass for electricity generation. Based on the study, it is was identified that indirect co-combustion of natural gas with biomass (in the form of producer gas) with carbon capture technology is the way to go towards achieving net-zero CO2 emissions. To effectively describe the process as being a net-zero CO2 emissions approach, Life Cycle Assessment data was applied to the various processes involved in the indirect co-combustion of biomass and natural gas coupled with carbon capture technology. In the first phase of this work, 5M MEA, which is the benchmark solvent for CO2 capture was used as the worst-case scenario to determine the ratio of producer gas-to natural gas (on energy basis) sufficient for achieving net-zero CO2 emissions. Using the SaskPower forecasted electricity generation capacity for 2025/2026 as a case study and applying LCA data to 5M MEA as the solvent for CO2 capture, it was determined that on energy basis, 14.5% of producer gas (balance natural gas) is sufficient for achieving netzero CO2 emissions while satisfying the set electricity generation target. The next phase of the work was to develop an amine blend with an improved CO2 removal efficiency compared to the bench-scale 5M MEA. Four different blends were screened to assess their respective performance against 5M MEA. These included 2:2 AMP: 1-(2HE) PRLD, 2:2 AMP: DEA-1,2-PD, 3:1 1-(2HE) PRLD: AMP and 3:1 1-(2HE) PRLD: DEA-1,2-PD bi-blends. Among these solvents, 2:2 AMP: 1-(2HE) PRLD was the optimum solvent as it demonstrated a high CO2 absorption-desorption parameter compared to the other blends. The absorption parameter for 2:2 AMP:1-(2HE) PRLD was 4.5% higher than that for 5M MEA and the desorption parameter 1,667% higher than 5M MEA. In the last phase, the increased CO2 removal efficiency of the solvent was applied to LCA data to determine the ratio of electricity generation from natural gas and producer gas towards achieving net-zero CO2 emissions when the optimum solvent developed is used in place of 5M MEA. It was determined that at a desorption temperature of 110℃, nearly all the CO2 in the rich amine for the optimum was removed. The CO2 removal efficiency of this solvent is about 31% higher than that for 5M MEA, implying this solvent allows for the removal of higher amount of CO2 in the flue gas stream. From the life cycle massessment, using 2:2 AMP: 1-(2HE) PRLD as the absorbent for CO2 capture in place of 5M MEA, it was determined that the producer gas requirements on energy basis, for cocombusting indirectly with natural gas towards achieving net-zero CO2 emissions is just about 8%. The findings from this work demonstrates that co-combusting biomass with natural gas (which is a lesser emitter of CO2 compared to other fossil fuels) allows for satisfying the energy demands while achieving net-zero CO2 emissions when CO2 capture is applied. The major limitation that has faced the application of bioenergy with carbon capture technology has been concerns over its competition with farmlands for food production. The results obtained from this work has showed that lower amount of biomass would be needed for energy generation via co-combustion with natural gas towards achieve net-zero emissions when a solvent with an improved CO2 removal ability is used as the absorbent in the CO2 capture process.