Frequently Asked Questions

Why are renewable sources boosted?

Biomasses are renewable sources in all respects as they have null impact on the overall CO2 cycle– in fact the CO2 fixed in the plant during its growth is the same released during the various phases of energy conversion. In addition, biomasses involve various advantages that can be summarized as follows:

• They allow the production of energy from renewable source otherwise not energetically exploited in the territory and typically present in large quantity;
• Adopting energetic cultivations you attain environmental advantages deriving from the exploitation of uncultivated or abandoned lands, in line with EU provisions, as well as benefits for the erosion of the agricultural soil and the landslide, implying the consolidation of hydrogeologically unstable sides;
• From the economic point of view, a larger use of biomasses can allow facing up to the home energy demand with a reduction of the rate of dependence on foreign countries;
• In case of specifically designed plants, it is possible to use a part of the thermal energy produced in local ambit, with notable reduction of energy costs and increase of environmental advantages;
• It involves direct and indirect employment spin-offs (plant realization phase, personnel employed for the functioning almost all recruited locally, cleaning, maintenance, collection and transport of biomasses, etc.);
• It incentives the development of industrial, trade and craft activities for the need of finding materials and services;
• The energy conversion occurs through the implementation of the Best Available Techniques for the conversion and for the purification of gaseous fumes; the emissions of the power plants are purified and controlled by fume treatment systems and avoid that the residues of agricultural and forest biomasses are locally burnt increasing the risk of fires and the atmospheric pollution.

Which is the social-economic impact of a biomass power plant?

A biomass power plant, besides producing clean energy, contributes towards the development of the territory, strengthening the economic pre-existing activities and creating new employment prospects, as the inhabitants of the Communes where the power plant is established are involved both in the manufacturing and the management phase of the power plant.

Besides, all direct and indirect sectors connected with the biomass power plant are developed.

Also unused and abandoned territories for the alimentary production find new life. As a matter of fact, the requirements of wood to be used as fuel in power plants stimulates the development of local agro-energetic production chains and exploits those already existing, such as the exploitation of wood coming from the programmed cutting down or from the cleaning of woods, orchards etc.

Which are the technologies for the combustion of biomasses and the fume treatment
used in Bioenergie power plants?

The energy contained in biomasses and used by men and animals through the digestion can be directly used as thermal energy in the combustion process (traditional and prevailing use), for the production of electrical energy (coupled with thermal energy) or concentrated in a variety of solid, liquid or gaseous fuels that make the transport and the final use easier.

In short, the process of biomass conversion into energy can be grouped in two big categories:

• thermochemical processes;

• biochemical processes;

Thermochemical processes are based on the heat action that enables the necessary chemical reactions to change the material into energy and can be used for products and residues whose C/N ratio has values exceeding 30 and the humidity content does not overcome 30%.

The most suitable biomasses for undergoing thermochemical conversion processes are the firewoodand all its by-products (sawdust, shavings, etc.), the most common cultivation by-products of lignocellulosic kind (cereal straw, pruning residues of vines and orchards etc.) and some machining wastes (shells, stones etc.).

Combustion is a chemical oxidation reaction of a fuel with a comburent (air or Oxygen) that occurs at high speed and with strong development of thermal energy. From the thermodynamic point of view it is a conversion process of the chemical fuel energy into heat.

The attained temperature value depends on the calorific power of the fuel, on the type of comburent used and on the fuel/comburent ratio. To obtain a complete combustion, and then the total exploitation of the available chemical energy, you operate with an excess of comburent; the excessive increase is not opportune because it causes a decrease of the maximum attainable temperature.

Combustion, at present, remains the most reliable solution.

The most diffused technologies for the combustion of solid biomasses, at present used in medium-big size plants, are the following:

• Combustion on grate (fixed, mobile, spreader/stoker, air-or water-cooled, etc.); they are suitable for all fuels and turn out to be sufficiently flexible towards the fuel wetness;

• Combustion in powdered phase (sawdust), prevailingly in co-combustion with other fuels;

• Combustion in fluid phase (recirculating fluidized bed, bubble fluid bed) where the fuel is kept in suspension through an air flow from bottom to top.

All cycles foresee then the production of vapour that is expanded into turbines connected with generators for the production of electricity. The fume treatment systems for biomasses are typically:

• SNOx abatement system (SNCR in boiler);

• Partial dust abatement with multicyclone downwards the boiler followed by high-efficiency bag collector or electrostatic filter for the total dust collection from fumes;

• Injection of alkaline reagent for the treatment of acid gases with possible dry reactor;

Besides, it is foreseen a monitoring in continuous of: fume temperature, O2, CO, COT, SO2, HCl, NOx, dusts.

How are combustion ashes used?

The combustion ashes of virgin biomasses are rich in mineral elements that are absorbed during the plant growth phase and come from the substratum where the plant grows. In particular, according to the zone where biomasses are cultivated, combustion ashes contain relevant quantities of alkaline substances such as oxides of potassium, of sodium, of calcium, of Magnesium and carbonates.

The ashes produced by biomass plants are subdivided into heavy ashes, that’s to say deriving from the real combustion bed and constituting the predominant part, and light ashes, finer fraction obtained through the purification of combustion fumes by means of filters.

Typically, thanks to their chemical-physical characteristics, their recycling is possible both as element constituting the charge for the production of cements and as amending substance in the formulation offertilizing composites.

In various European nations, some time ago they have already foreseen a direct reuse of ashes from combustion biomasses directly in agricultural fields.

• Is it possible to cogenerate heat and to recycle heat wastes?

The production cycle of electricity of a biomass power plant is based on the Rankine cycle with the vapour production at high temperatures and pressures which is expanded into a turbine that feeds an electricity generator.

For the vapour condensation from the gaseous to the liquid state, for its reuse in the cycle, it is foreseen a condensation system where some low temperature warmth is yielded through a condenser to a closed water cycle.

The project of the thermal cycle, optimized to produce electrical energy in efficient way, implies that even if the involved warmth quantity is high, the temperature at which the warmth is available is low (about 35-40 °C) and this makes it scarcely interesting for civil thermal uses.

The cogeneration of heat is anyway possible if it is taken into account since the design phase, optimizing the overall thermal cycle.

What is the short provisioning chain?

The term “short provisioning chain” identifies the provisioning process of waste of vegetal origin that privileges the biomass within a radius of 70 km from the power plant, with the consequent drastic decrease of costs and pollution due to transport.

The law 29/11/2007 n.222 recognizes to the electrical energy production from biomass from short provisioning chain (that’s to say coming from a production site located in the radius of 70 km) or, as an alternative, from chain agreement, a rise coefficient of green certificates equal to 1.8, against 1.1recognized to biomasses coming from long provisioning chain.

Where does the used biomass come from?

The biomass used by Bioenergie plants is constituted, by order of importance, by:

• Forest residues and wood industry residues deriving from wood maintenance intervention, the machining of sawmills, the transformation of the wood product;

• Agricultural by-products such as pruning brushes, vine-shoots, etc.

• Energetic cultivations for the production of biomasses (wood) for the energetic exploitation. The most interesting species are: poplar, acacia, eucalyptus;

• Agroindustrial residues composed by peanut shells, olive residues and other products coming from the food industry available for energetic purposes;

The plants of Biomasse Italia mainly use biomass coming from selective interventions of forest maintenance of the Calabria basin and additional quantities of peanut shells coming from the machining of oils and olive residues that derive from the production process of olive oil.

The San Marco Bioenergie power plant at Bando d’Argenta receives almost 80% of biomass coming from dedicated productions of decennial poplar groves cultivated in the Padana Plain basin and the remaining part derives from selective interventions of forest maintenance of the Apennine territory. Marginally are used biomasses coming from saw mills or from collections of explants of orchardscultivated in the Ferrara area.

Have supply agreements been signed with farmers for the cultivation of fast growing SRF
biomass?

Fast growing biomasses are wood cultivations with short cutting down cycle (2 – 3 years) characterized by fast growth and large production of biomass. The plantation site must be chosen in the outskirts of the road net and of the Power Plant, to reduce transport costs.

The need of producing wood implies notable induced employment in the primary sector, which differentiates biomass power plants from traditional fuel ones.

Bioenergie promotes the signature of contracts with the producers of fast growing biomasses conforming to acceptability plant requisites also over long periods.

San Marco Bioenergie, according to the contracts signed in 2008, has purchased almost 20,000 tons of fast growing poplar from the suppliers of Veneto, Emilia Romagna and Lombardy.

Which are the actions undertaken by Gruppo Bioenergie for the protection and the respect of the
environment?

The companies of Gruppo Bioenergie have acquired an integrated policy for the protection of the environment, of workers’ health and safety, the pursue of continuous improvement, the personnel’s training and the integration with the territories that house the power plants.

To this end all operational companies are provided with environmental management systemscertified in compliance with ISO 14001 standards.

From the technical point of view, the plants of the group are designed and manufactured applying theBest Available Techniques in force at the design time.

Finally, the policies of Bioenergie promote the saving of natural resources employing high-efficiency productive cycles, the reuse of the treated water resources, the recovery of wastes produced selecting their suppliers among those able to avoid the conveyance to dumps.