Carbon dioxide removal and capture for lanfill gas up-grading

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.