The Italian expertise
The Italian energy industry has taken a leader role for production and utilization of technology applied in the biogas and biomass sector. Italy is internationally one of the technology leaders, particularly in the area of gasification based on organic waste and renewable sources. Italian companies in the bioenergy industry cover the entire cycle of this technology, from the production (CHP systems, biogas and biomethane technology, digesters, combustors and boilers) to the planning (operation and maintenance of bioenergy plants).
Bioenergy means energy produced by biomass (every material originate from living organisms), bioliquids (liquid fuels obtained by biomass) and biogas (gas originate from anaerobic fermentation of organic material).
The term biomass stands for the biodegradable fraction of products, waste and remains of biological origin coming from agricolture (including vegetable and animal substances), from forestry and the connected industries, included fishing, aquaculture and the biodegradable side of the urban and industrial waste (Dlgs 28/2011). This definition includes a wide set of materials, virgin or remains of the agricoltural and industrial production, that can come up in different physical states, with a wide spectrum of calorific powers.
System solutions vary by type of biomasses, utilized technology and final product (only electric energy, combined with heat production, only thermal energy).
Thermal power plants fueled with solid biomasses make the convertion of thermal energy, included in biomass, in mechanic energy and then in electric energy. Sizes of power plants can vary from medium sized thermal power plants, fueled with solid biomasses, usually wood chips, until the small sets feeded with syngas, generated from wood pyrogassification.
Outside a preliminar phase of biomass treatment, thermoelectric biomass plants are quite similar to those feeded with traditional fuels.
The most current types of plants are:
- traditional plants with a combustion furnace of solid mass and boiler, feeding a steem turbine coupled with a generator;
- plants with otto cycle engine or, more rarely, gas turbine feeded by syngas fueled with biomass pyrogassification;
- hybrid thermal power plants using biomasses and conventional sources (the most frequent case is the biomass co-combustion and the conventional souce in the same boiler).
Biogas and landfill gas
Biogas, mainly consisting of methane and carbon dioxide, is derived from the anaerobic fermentation of organic material, of vegetable and animal origin.
Biogas has an excellent calorific power, due to the high methane content. This lends itself to an energy valorization for direct combustion, that takes place in the boiler only producing heat or in engines coupled with generators only producing electricity, or electricity and heat co-generating. Therefore, thermal power plants dealing with biogas convert the thermal energy contained in biogas into mechanical energy and then, subsequently, into electricity.
In case of plants feeded by gas produced by the anaeobic fermentation of the garbage stored in monitored landfills of urban waste, the plant's main parts are:
- section of extraction of landfill biogas;
- section of aspiration and conditioning of landfill biogas;
- section of production of electric energy and torch.
In case of biogas not deriving from landfill, the plant scheme has, instead of the extraction section, a production section and collection of biogas, that then is sent to generators to produce electric energy.
Bioliquids are liquid, raw or refined, fuels. obtained by biomass. They can have vegetal or animal origin.
Their use, aiming to produce electric energy, is consolidated; the production plants have a standard configuration utilizing diesel cycle engines. Those plants, that can have variable sizes, from few kilowatt to some tens megawatt, are usullay composed by:
- storage and fuel treatment equipment;
- equipment of fuel transfer from storage to buffer tank and engines;
- generation groups;
- rivers treatment system;
- cooling or heat recovery system.
In case of medium-big sized plants, it's commonly used a combined cylce aimed to the energetic recovery of combustion smoke heat.
The term “biofuel” means any liquid or gaseous fuel used for transport, obtained by biomass (DLgs. 28/2011 and D.Lgs.55/2011).
Biofuels are usually distinguished in I and II generation biofuels, even if, recently, we have started talking about III and IV generation biofuels.
By first generation biofuels, we mean those that come from agricultural raw materials, such as cereals and sugar cane, which also have an alimentary use and, therefore, present a risk of possible resource competition for the use of an agricultural land. Conventional biofuels, such as biodiesel, bioethanal and bio-ETBE, fall into this first category.
Second generation biofuels are products of raw materials not competing for the same land of the food and agricultural industry (including biofuels produced with lignocellulosic biomass and biofuels produced from waste and by-products).
Recently, III and IV generations biofuels have been discussed in terms of the developments, still in study phase, related to improving quality of raw materials, by using crops that can increase and improve yields. An example of this would be genetically modifying some raw materials and using algae and yeasts.