Agricultural greenhouse CO2 utilization in anaerobic-digestion-based biomethane production plants: A techno-economic and environmental assessment and comparison with CO2 geological storage.

• Design of CO 2 -enriched greenhouses using captured CO 2 from a biogas to biomethane upgrading unit. • Economic and environmental assessment of the proposed CO 2 Utilization route. • Comparison with CO 2 geologically stored plant configurations. • CO 2 utilization route exhibits better economic performance than the CO 2 storage case. • Net greenhouse gas emission savings for the Utilization case are strongly dependent on system/boundary assumptions. Anaerobic digestion plants enable the production of power, heat and fuel. Biogas can be upgraded to biomethane fulfilling grid injection requirements by separating CH 4 from CO 2. By- product CO 2 could be geologically stored or utilized as a feedstock to produce valuable goods, enabling in both cases negative climate change impact fuel production. CO 2 utilization could as well improve plant economics, as a consequence of the profits related to the commercialization of the final products whilst allowing further emission reductions. In this paper, a techno-economic assessment of the use of the CO 2 by-product in CO 2 -enriched agricultural greenhouses for tomato production is discussed. The results of the research show that, depending on the operating mode and the design approach, the use of a greenhouse enables the recovery of 14–67% of the by-product CO 2 when the internal CO 2 concentration is kept at 1000 ppm. In addition, it is estimated that the associated heat and power demand ranges from 0.097 to 0.138 kWh th /kg of used CO 2 and 0.04–0.05 kW e /kg of used CO 2 , respectively. Revenues related to the tomato production are partially offset by the greenhouse capital investment and operating costs; however, a net profit between 16 and 19 p/kg of used CO 2 was calculated, leading to a net profit of 1.3–1.6 p/kWh of injected biomethane. These results show that CO 2 utilization is technically feasible and economically more convenient than CO 2 storage. While both geological storage and CO 2 utilization would allow negative climate change impact fuel production, the net greenhouse emission savings for the utilization configuration were found to be strongly dependent on the assumptions regarding fuel substitution for the produced biomethane. [ABSTRACT FROM AUTHOR]