This work reports the preliminary evaluations obtained within the UPGAS-LOW CO2 project (LIFE08 ENV/IT/000429) concerning innovative methods for biogas upgrading through CO2 capture and storage. One of the methods studied in this project is chemical absorption of the CO2 contained in landfill gas with a KOH solution followed by carbonation of the spent solution with selected industrial residues to regenerate the alkaline solution and store CO2 in a solid phase (calcite). This paper presents the main results of the lab scale experiments carried out to evaluate the effects o f the main operating parameters on the carbonation reaction so to identify the conditions that allow to maximize the CO2 uptake of the solid residues and the percentage of KOH that can be regenerated for the absorption process. These results provide the dataset for the design of a pilot plant unit to be built and operated in the follow-up of the project

Within the frame of an EC financially supported project - LIFE05 ENV/IT/000874 GHERL (Greenhouse Effect Reduction from Landfill)–a pilot plant was set up in order to demonstrate the feasibility of applying chemical absorption to remove carbon dioxide from landfill gas. After proper upgrading - basically removal of carbon dioxide, hydrogen sulphide, ammonia and other trace gas compound–the gas might be fed into the distribution grid for natural gas or used as vehicle fuel, replacing a fossil fuel thus saving natural resources and carbon dioxide emissions.Several experiences in Europe have been carried out concerning the landfill gas - and biogas from anaerobic digestion - quality up-grading through CO2 removal, but in all of them carbon dioxide was vented to the atmosphere after separation, without any direct benefit in terms of greenhouse gases reduction.With respect to those previous experiences, in this work the attention was focused on CO2 removal from landfill gas with an effective capture process, capable of removing carbon dioxide from atmosphere, through a globally carbon negative process. In particular, processes capable of producing final solid products were investigated, with the aim of obtaining as output solid compounds which can be either used in the chemical industry or disposed off. The adopted absorption process is based on using aqueous solutions of potassium hydroxide, with the final aim of producing potassium carbonate. Potassium carbonate is a product which has several applications in the chemical industry if obtained with adequate quality. It can be sold as a pulverised solid, or in aqueous solution.Several tests were carried out at the pilot plant, which was located at a landfill site, in order to feed it with a fraction of the on-site collected landfill gas. The results of the experimental campaign are reported, explained and commented in the paper. Also a discussion on economic issues is presented

Research in mineral carbonation has moved towards process concepts that combine the capture of CO2 from flue gas with its conversion into stable carbonates. This requires highly reactive source materials that dissolve under lean CO2 pressures and temperatures. Activated serpentine has been used in this study, and its carbonation potential under flue gas conditions has been investigated. Single-step carbonation experiments were performed in stirred reactors with gas-dip tubes, at partial pressures of CO2 up to 1bar, temperatures between 30°C and 90°C, with and without concurrent grinding using a ball mill. The pH and solids were monitored in-situ, and the degree of carbonation of the products was quantified using thermogravimetric analysis. Given the low CO2 pressure, carbonation was successful, as confirmed by the formation of the two magnesium carbonates nesquehonite and hydromagnesite. However, under all conditions investigated, including grinding, the extent of carbonation did not exceed 20%. It was concluded that after the onset of precipitation, the reactor solution in single-step carbonation experiments reaches equilibrium conditions with respect to both serpentine dissolution and carbonate precipitation