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Project Profile: Biogas CHP plants in Italy from pig farmer to energy producer

Pietro Bertesago has installed two biogas plants in 2008 and 2010 – both based on CHP modules from MTU Onsite Energy – which supply heat energy to his farm and export energy to earn a generous feed-in tariff from the Italian government.

The biogas business is booming in Italy, where biogas-based electricity qualify for the world’s highest subsidy levels. Eligible plants in operation by the end of 2012 earn 28 euro cents/kWh – up to a maximum of 999 kW – for a period of 15 years. Plants in operation by 2009 enjoy an even longer subsidy period of 20 years.

Corn and liquid manure ferment in a tank to produce biogas which powers the CHP plant.

The scheme’s beneficiaries include Pietro Bertesago, a pig farmer from Moscazzano in the northern Italian province of Cremona. In 2008, he installed the region’s first biogas plant at his farm, about an hour’s drive from Parma, where 2000 pigs are reared for Parma ham.

FROM PIG FARMER TO ENERGY FARMER

The high feed-in tariff was not the only reason Bertesago built his biogas plant. There was also a €1 million (US$1.3 million) loan for which the provincial government in Lombardy took over the interest payments in order to encourage farmers to make the investment. Bertesago used the opportunity to develop the biogas plant as a second source of income because pig farming alone was no longer a high earner. As the farmer recognised at the time: ‘The future is in biogas, not pig farming.’

The plant was supplied by the Austrian company Thöni Umwelttechnik, which specialises in developing and building plants for generating electricity and heat from renewables. Together with ENplus Italia and MTU Italy, Thöni developed a biogas plant and container that met EU specifications as well as Italian regulations.

The core of the generating plant came from Germany: a type GR 370 B5 CHP module from MTU Onsite Energy in Augsburg. The module is based on a 12-cylinder MTU Series 400 biogas engine and the system produces a maximum of 370 kW of electricity and 241 kW of thermal energy. Bertesago feeds the electricity into the public grid and, in winter, he uses the heat from the engine to heat his pigsties.

CHP plant with type 12 V 400 biogas engine. The 6- and 12-cylinder versions produce 120 to 400 kW of electric energy and 160 to 540 kW of thermal energy.

To increase his power output, two years after building the first biogas plant Bertesago added a second CHP unit, also based on an MTU Series 400 engine. In reduced operating mode, each of his CHP plants now produces 282 kW to achieve the 564 kW maximum output capacity a farm of this size is allowed to feed into the grid.

BACK-UP PLANT PAYS OFF

The farmer could also achieve the same output with one larger engine, which could reduce purchase and maintenance costs. But having two smaller MTU engines also offer advantages, such as a reduced risk of failure. If one engine fails, the other can be operated at its maximum output of 370 kW to avoid wasting any of the valuable biogas that bacteria in the fermenter produce.

This methane is more damaging than carbon dioxide so cannot be allowed to escape into the atmosphere unburned. Bertesago would have to use a flare to burn off biogas that cannot be used in his CHP plants, but this is unlikely with two units, as the probability that both will fail at the same time is negligible.

The two plants are taken offline individually for maintenance about eight times a year or after 1000 hours of operation. Maintenance costs for two small modules exceed those for one large one by only 15%, as MTU Italy offers favourable package prices for multiple units.

This difference is more than offset by enhanced earnings through continuous electricity production at MTU’s extremely high efficiency rates. Plants based on this back-up principle also attract financial and insurance benefits as banks and insurance companies reward increased security with more favourable credit and premiums.

The biogas is produced just a few metres from the sties in a large fermenting tank for corn, liquid manure and glycerin. Each day Bertesago’s 2000 pigs produce about 30 tonnes of liquid manure, which is used to produce biogas. Pig manure contains more methane than cattle manure so offers a higher biogas yield. But the liquid manure’s energy content is not enough for biogas production, so 20 tonnes of corn, 2 tonnes of glycerin and 40 tonnes of water are also fed into the fermenting tank.

Twice a day, the farmer has to fill the mixer with corn silage but the dosages and supplement rates for the other constituents are calculated automatically and are computer-controlled.

Bertesago’s daily routine also includes checking the temperature in the fermenter and taking engine data readings. If any irregularities occur, he can contact his customer service technician at MTU Italy, who has remote access to his engine data and can adjust settings or maintenance instructions.

Bertesago aims to completely pay off the loan for building the plant in 10 years. His maximum feed-in rate of 564 kW for 360 days a year will produce revenues of around €1.35 million a year. That also has to cover the cost of producing additional corn crops, which he now needs not only to feed his pigs but also for biogas production.

BIOGAS PLANT IN NEIGHBOURING VILLAGE

A few kilometres from Bertesago’s farm, in the village of Sospiro, dairy farmer Giovanni Bertoni has his farm with 500 cows, which produce about 10,000 litres of milk a day. Since 2010, Bertoni has also had a biogas plant with a type GR 370 B5 CHP module from MTU Onsite Energy. Like Bertesago, he began with a smaller plant. Bertoni is now feeding an initial amount of up to 250 kW into the public grid, because in Italy it is much simpler to get approval for smaller CHP plants up to this size. He uses the heat from the engine to warm the cows’ drinking water in winter and the additional hot water produced is also used for cleaning the cowsheds.

He, too, uses liquid manure from his animals to produce biogas and feeds 10 m3 of manure per day into his fermenter. He has bought extra fields to grow enough corn for biogas production and cultivates 125 hectares of land.

Like Bertesago and Bertoni, more and more Italian farmers are deciding to move into energy production. By 2020, the Italian government wants to cover at least 17% of the nation’s energy consumption from renewable sources, and 40% of that target is earmarked to come from biomass. That is why the government is offering farmers incentives in the form of attractive feed-in tariffs, tax breaks and favourable loans for biogas plant construction.

Nevertheless, potential energy producers know how important reliable plant with low failure potential is for long-term success. In MTU Italy, farmers have a reliable partner on site to provide expert advice and outstanding plant maintenance on excellent terms.

MTU Onsite Energy is the brand name under which the Tognum Group markets distributed power generation systems. The product range includes compact cogeneration modules powered by gas engines up to 2150 kW, or gas turbines up to 45 MW.

www.mtu-online.com

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