What is biogas? From problem to resource

The biogas it is a gas rich in methane and carbon dioxide produced by the natural decomposition of waste present in landfills. In fact, biogas can be used as a fuel in cogeneration plants CHP for the production of electrical and thermal energy to be fed into the network and thermal energy to be used in any district heating systems. If energy recovery is not possible, it can be disposed of through controlled combustion, a process that reduces its polluting impact.

In addition to being captured by landfills and conveyed to cogeneration plants, biogas intended for energy production can be produced starting from animal waste and from what is defined in Italy Forsu, Organic Fraction of Urban Solid Waste. In the case of manure, the residues are collected, transported and treated with an anaerobic process from which biogas is obtained which can be transformed into electricity and heat in a combined way. Examples in this sense are the German citizen of Lünen, north of Dortmund, which aims to meet 30-40% of its energy needs with biogas of animal origin taken from nearby farms; and the city of Berlin, which announced a project to compost dog manure in urban areas to produce biogas.

An example of the production of biogas from kitchen waste it is instead the city of Malmö, in Sweden, where buildings have been designed with a government-sponsored project from which food waste (Forsu) does not end up in the sewer but in a separate system that transforms food waste into methane, which is then burned for energy. Even the city of London, in the UK, is examining a similar system for a 2,000-home construction project.

A system for transforming kitchen waste into energy without preventive interventions is instead that of Food Waste Disposer (DRA), an appliance that can be installed under the kitchen sink that shreds waste and allows its disposal through the sewer system. Half of American homes are equipped with this device, invented in the USA in 1927, and in Europe the city of Stockholm, also in Sweden, has recently introduced the DRA in a structural and organic way within its water management and treatment plants and waste. The expected benefits are the biogas production and the CO₂ reduction linked to the separate collection of Forsu. Obstacles are, albeit limited, higher consumption of water and electricity (for the functioning of the heatsink). However, a multi-criteria approach to waste management suggests the usefulness of the disposer (the balance between resources consumed and resources recovered is positive) as confirmed by the tests carried out.

And in Italy? Just so as not to think that certain things happen are beyond the Alps, in our country the biogas issue is on the agenda and there are already significant business initiatives (rather than legislative). An example that has already hit the headlines is that of MEG - Marcopolo Environmental Group - a Cuneo company that recently launched its "Zooagrobioenergetic Environmental Project of Closed Cycle Supply Chain " for the recovery and energy enhancement of organic matrices from zootechnical biomasses.

Marcopolo withdraws the surplus of animal waste from breeders, in accordance with the provisions of the Nitrate Regulations, thus avoiding air and land pollution, and subjects them to a treatment based on an anaerobic process (MESAD process - Marcopolo Ecotone System Anaerobic Digestion) from which biogas, green energy and a land renovator are obtained, Humus Anenzy, specific for the care of tired and polluted soils. The advantages are quantifiable in the destruction of biogas, in the abatement of carbon dioxide, in the saving of oil and in the production of energy for electricity and heating.

Marcopolo is also the owner of cutting-edge and specific technologies for the reclamation, conveyance and energy enhancement of landfill biogas, a sector in which it has become a leader. The system devised by MEG researchers is based on a complex gas capture mechanism, integrated in the landfill closure project. The biogas is conveyed to the purification system and, through a dedicated chemical-physical process, is purified of the numerous liquid and gaseous pollutants present and then used for cogeneration, through specific eight-cycle endothermic engines, capable of obtaining energy yields, on average around 40%. The green electricity thus obtained is sold to the national grid, while the thermal energy, produced with cogeneration, can be used for district heating. Marcopolo Environmental Group owns over 40 active plants in Italy, built and managed on its own, and a dozen under construction. One plant active and one under construction are located in Portugal.

On the production front of biogas from Forsu, things are a bit more complex. There are no separate sewage systems and despite the positive tests (Lucca, Monghidoro, Biella, Padua and Chieri) and a law - 210/08 - that allows the disposal of organic waste from food waste treated with food waste disposers, subject to the existence of a purification system by the managing body of the Integrated Water Service, still no administration has thought of a real experimental application in the field. Food waste disposers are still on the market and the reference company is the InSinkErator, Division of the international group Emerson. The start of door-to-door separate collection by Forsu in some large cities (Milan in November 2012 on a sample of 400,000 inhabitants), with all the problems involved, is rightly heating up the issue. A recent study byUniversity of Verona he was born in Polytechnic of Turin conducted in parallel with the Chieri trial confirms that the introduction of DRA in homes would have a positive economic impact in general terms,

Video: what is biogas? how did it produce? (October 2020).