Integrating Algae with Bioenergy Carbon Capture and Storage (ABECCS) Increases Sustainability

Bioenergy carbon capture and storage (BECCS) has been proposed to reduce atmospheric CO2 concentrations, but concerns remain about competition for arable land and freshwater. The synergistic integration of algae production, which does not require arable land or freshwater, with BECCS (called "ABECCS") can reduce CO2 emissions without competing with agriculture. This study presents a technoeconomic and life-cycle assessment for colocating a 121-ha algae facility with a 2,680-ha eucalyptus forest for BECCS. The eucalyptus biomass fuels combined heat and power (CHP) generation with subsequent amine-based carbon capture and storage (CCS). A portion of the captured CO2 is used for growing algae and the remainder is sequestered. Biomass combustion supplies CO2, heat, and electricity, thus increasing the range of sites suitable for algae cultivation. Economic, energetic, and environmental impacts are considered. The system yields as much protein as soybeans while generating 61.5TJ of electricity and sequestering 29,600t of CO2 per year. More energy is generated than consumed and the freshwater footprint is roughly equal to that for soybeans. Financial break-even is achieved for product value combinations that include 1) algal biomass sold for $1,400/t (fishmeal replacement) with a $68/t carbon credit and 2) algal biomass sold for $600/t (soymeal replacement) with a $278/t carbon credit. Sensitivity analysis shows significant reductions to the cost of carbon sequestration are possible. The ABECCS system represents a unique technology for negative emissions without reducing protein production or increasing water demand, and should therefore be included in the suite of technologies being considered to address global sustainability. Plain Language Summary We evaluated the sustainability of integrating algae production with bioenergy CCS (called ABECCS). Our motivation is to devise an affordable system that removes CO2 from the atmosphere without negatively impacting food security. The International Panel on Climate Change suggested that in addition to zero-emissions systems (such as solar power or crops), negative-emissions systems are needed to mitigate global warming. Bioenergy CCS (BECCS) is a promising negative-emissions approach in which biomass is combusted to generate electricity in conjunction with CCS. However, on a scale relevant to mitigating global warming, the arable land and freshwater requirements for BECCS could be unviable and cause competition with food production. In the ABECCS system, soy cropland is replaced by eucalyptus forests used for BECCS that provides marine algae with CO2, heat, and electricity. The integrated 2,800-ha facility produces as much high-quality protein as soy without increasing freshwater demand, and generates 61.5 TJ of electricity while sequestering 29,600t of CO2 per year. The system is economically viable when receiving $600/t of algae and $278/t of CO2 sequestered. With favorable economic conditions, ABECCS could contribute to the reduction of CO2 in the atmosphere in a sustainable way.