Dry anaerobic digestion allows biogas to be obtained from the processing of substrates with a dry matter content greater than 20% and up to 50%, with a mesophilic process temperature of 37°C, unlike "traditional" anaerobic digestion. which is usually made with material from the agro-zootechnical and food sectors, whose dry matter content is around 10%.
This technology gives excellent results, especially when used with municipal solid waste (MSW) and other organic remains; Its use is spreading throughout Germany and much of Italy.
The Hera Ambiente group is building the largest dry technology plant in Italy, in the municipality of Sant'Agata Bolognese, to obtain biomethane and generate quality compost. This is the first unit to be installed in Italy in a waste management center where the organic fraction of urban solid waste (FORSU) and special waste (mainly green waste and prunings) are valued.
With an investment of 37 million euros, the plant has 4 digesters with a total capacity to treat 100.000 tons of FORSU organic waste and 35.000 tons of prunings and similar waste per year. This makes it possible to obtain 7,5 million cubic meters of biomethane and 20.000 tons of high-quality compost.
Good waste separation at home is key to optimizing the recovery of waste in the treatment center and digesters and reducing its environmental impact. The community itself benefits by having the biomethane obtained to fuel public and private transportation. Part of the biogas obtained is used as fuel in the cogeneration engines that the landfill has.
In the plant, FORSU is crushed and screened to separate plastics and other materials thanks to a Tiger Depack HS20 OSC equipment; The organic fraction is mixed with a quantity of green biomass and enters the digesters.
The Tiger Depack equipment reduces the amount of organic substance in the non-reusable fraction from 50-60% to 5-6%, thereby reducing the weight of waste - mainly plastic and textile materials - by more than 50%. % making its disposal easier and cheaper.
The biomethane produced in Sant'Agata Bolognese already powers some buses and taxis in the city of Bologna and is also distributed to individuals, thanks to its availability at 4 service stations.
According to Tomaso Tommasi di Vignano, CEO of the Hera Group, the company is working on other projects with the aim of giving a “concrete response to the need to treat growing volumes of waste” and “contribute to the improvement of air quality and the carbon footprint.” In addition, he assures, they are studying other innovative processes to enhance other supply chains, such as sewage sludge and pruning, and obtain new generation fuels.
More information
https://ha.gruppohera.it/plants/composting/santagata_bolognese_composting_plant
https://www.tigerdepack.com/it/tiger-depack/hs20-osc.html
