Clean Production of Bioplastic and Bio-oil from Solar Energy and CO2

This paper presents a clean technology to convert CO2 into biomass, bioplastic and bio-oil by using a novel artificial photosynthetic system. In contrast to conventional photosynthetic plants and algae, the artificial system decouples the solar energy capture from CO2 fixation so that CO2 can be canptured and converted continuously regardless of the intermittency of insolation. The system consists of a photovoltaic assembly and a water electrolyzer to capture and convert solar energy into H-2 and O-2. An autolithotrophic bacterium is hired to fix CO2 using H-2 in dark conditions. Because the microbial CO2 fixation is not restricted by light, a high cell density (> 20 g/L) was conveniently achieved. The specific cell growth rate on CO2 fixation was about 3 times higher than that of the fastest growing species of microalgae or cyanobacteria. About 50% of cell mass formed from CO2 was polyester, which contains 50% more energy than starch. The biopolyester can be used either as a bioplastic, or processed into bio-oil or other drop-in chemicals. The overall efficiency from solar energy to biomass ranges from 4 to 8%, which is higher than the efficiency of plants and algae (0.5-2%). Efficiency analysis indicates that the solar electricity has the lowest efficiency (10-17%) compared with dark CO2 fixation (32-59%) and water electrolysis (70-80%). The system efficiency can therefore be further improved with new photovoltaic technology. This new technology has a potential of high intensity carbon capture for power plants and oil refineries.