Analisi Del Ciclo Di Vita Di Un Processo Per Rimuovere La Co2 Atmosferica E Contrastare L’acidificazione Del Mare
Year: 2020
Type: article
Abstract: In order to limit global warming "well below 2°C", as agreed in the Paris Agreement, a drastic reduction of the greenhouse gases emissions is urged, as well as removing CO2 from the atmosphere in larger quantities, the more the reduction of emissions is delayed. For this reason, many technologies have been proposed to remove CO2 from the atmosphere (so-called Negative Emission Technologies), and scientific-technical research is fast developing to assess the environmental potential, costs, benefits and critical points of the different options. The article presents a new process that combines commercial industrial technologies with technologies still at the research and development stage or not yet commercially available, in order to remove CO2 from the atmosphere and at the same time to address the acidification of the sea. The process aims to overcome the limitations of other negative emission technologies, such as high costs, high energy demand, or potential competition in water use and land use. The process is based on the following steps: (a) gasification of a solid fuel (e.g. biomass) with consequent production of a syngas; (b) conversion of syngas hydrocarbons and tar oils into hydrogen (H2) and carbon monoxide (CO) in a high-temperature thermal steam reformer; (c) production of Ca(OH)2 (slaked lime) from limestone, using the enthalpy of the hot syngas; (d) spreading in the seawater, by means of ships, slaked lime to contrast the acidification of the sea; (e) sending the syngas to a water-gas-shift reactor with the production of CO2 and H2, which are then separated; (f) final storage of all the CO2 produced in the process; (g) use of H2 for decarbonized energy production. The mass and energy balances show that the total amount of CO2 removed from the process is 3 tonnes per tonne of biomass used. Considering the emissions avoided by using the hydrogen produced by the process, which displace the use of fossil fuels, the overall benefit of the process increases to 3.4 tonnes of removed CO2 per tonne of biomass. To evaluate the environmental impact of the process, a Life Cycle Assessment has been carried out, in which seventeen impact categories have been considered. For “climate change”, the most impacting processes are calcination, feedstock supply and CO2 storage. Considering a cradle-to-grave approach with the LCA methodology, the benefit in terms of CO2 removal is reduced by about 2% (compared to the carbon balance). Thanks to the removal of CO2 determined by the alkalinization of the sea, and to the CO2 stored, as well as the CO2 avoided, the process therefore allows to achieve and higher amount of negative CO2 emissions, compared to the traditional technology of bioenergy with carbon capture and storage (BECCS). The availability of biomass is a limiting factor to the large-scale development of the process.
Source: Ingegneria dell'Ambiente
Institution: Politecnico di Milano
Language: Italian
Subfield: Filtration and Separation
Field: Chemical Engineering
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W3081606166