Power from biomass and waste
Entraining for the Olympics2 September 2004
Generation from landfill sites like Basse di Stura could help the city of Turin solve environmental problems created by the 2006 Winter Games.
As an internationally renowned destination for skiers, the snow-capped Alps beyond Italy’s northwestern city of Turin helped the city win its bid to host the 2006 Winter Olympic Games. However, Italy’s longer-term national goals are focused more on producing green energy than on gold medals.
Italy and other European Union members have charted an ambitious plan to reduce their dependence on fossil fuels and curtail greenhouse gas emissions. To meet those goals, the EU is pushing to produce 22 % of its electricity from renewable sources by 2010. One relatively small but growing renewable source is landfill methane gas (LFG), which is created by the decomposition of organic material.
Methane (CH4) has 21 times the greenhouse potential of carbon dioxide (C02), the gas most closely associated with climate change. Consequently, the Kyoto Protocol and other environmental directives specifically encourage EU members to use their respective landfill methane reserves for energy so that less of the gas can escape into the atmosphere.
While the European Commission has criticised most EU countries for falling short of their original environmental targets, its members are still demonstrating progress on numerous fronts. For example, most of Italy’s regions, including the Piedmont Region (of which Turin is the capital city), have initiated LFG-to-energy projects; a majority of this power is being used for local purposes or sold to the national electrical grid.
One of Italy’s largest – and most recent – LFG projects was completed in July 2004 at the Basse di Stura landfill, on the northern outskirts of Turin. Here, landfill owner and municipal waste disposal company AMIAT SpA. installed six GE Jenbacher 1.4 MW, JGS 420 GS-LL (version A21) generator sets. The six units are supplying a total of 8.4 MW of power for the national grid.
The new operation is AMIAT’s second LFG plant at Basse di Stura, where a smaller, 6.3 MW plant has been operating since 1999.
The Italian government has been formally supporting various renewable energy projects since at least 1991. For example, the public grid operator – or an intermediary – pays an energy provider (in this case, AMIAT) a fee for every kWh produced from a renewable source, such as landfill. The fee is paid under the system known as green certification.
Powering up Basse di Stura
Located five km north of Turin near the Stura di Lanzo River, Basse Di Stura is Europe’s second largest controlled landfill, having first opened during World War II. It underwent a major expansion in 1984.
The entire AMIAT facility covers 890 000 m2 and has a total capacity of 20.9 million cubic metres. In 2003, Basse di Stura received a total of 756 177 tons of various waste material from 323 municipalities, including 560 320 tons of municipal solid waste, according to AMIAT.
Basse di Stura is set to officially close in June 2005, but AMIAT expects to exploit its available biogas reserves there for between 20 and 30 years.
In 1999, AMIAT began exploiting its methane reserves by installing its first power plant, which consisted of four Caterpillar and two Deutz engines. It installed extraction wells as well as analysis and pumping stations. In 2003, Basse di Stura’s operator reported extracting more than 37.2 million Nm3 of biogas and generating 33 484 MHh of electricity, according to published company records.
However, AMIAT realised the potential was there to increase electricity production using a larger and more efficient system. In December 2003, it awarded the turnkey contract to Austria-based GE Jenbacher and GE’s project partner, Italian contractor A.B. Impianti. GE Jenbacher – a division of GE Energy – has installed 200 engines at 130 different landfill sites in Italy for a total installed electrical output of 160 MW. A.B. Impianti has been GE’s primary landfill project partner in Italy, supplying container solutions, and mechanical and electrical systems as well as engineering and installation services.
In June, GE delivered the final two gensets and in July, the plant began generating electricity. The new operation will produce more than 60 000 MW per year (8.4 MW for 7 500 running hours per year). Natural gas serves as the backup fuel.
Operating the system
The Jenbacher power plant’s efficiency rating is greater than 41 % – six percentage points higher than the older plant. The JGS 420 engine is claimed by its maker to have the highest electrical efficiency in the 1.5 MW range for non-natural gas applications.
Since 1998, 90 % of GE Jenbacher’s engines used in landfill applications – including the latest Basse di Stura units – feature the CL.AIR® environmental control system. CL.AIR, a secondary treatment of exhaust gas, is a system for regenerative thermal post-combustion of engine exhaust gases.
Once the gas has been heated to a temperature of about 800 °C, oxidation of unburned hydrocarbon and CO results in the production of steam and CO2. Since there are no catalytic reactions in thermal secondary treatment of exhaust gases, this process is particularly suitable for critical gases such as methane from landfills, where the use of a catalytic converter is possible only to a limited extent, if at all. By using the CL.AIR system, the operator can reduce C02 emissions to a value of less than 300 Nm3, far lower than the government-set limit of 500 mg/Nm3.
In addition to the engines and the CL.AIR systems, GE’s scope of supply included the engine control panels, engine commissioning and start up services and a four-year, full service engine maintenance contract. As part of the maintenance contract, GE Jenbacher is providing full service for the CL.AIR systems and engine control panels.
A.B. Impianti supplied all other equipment and services, including the engine containers as well as the design and installation work. In addition, the contractor supplied and installed the LFG pumping and purification systems and the medium voltage system for delivering the electricity to the national grid. The company also has a long-term service agreement for its equipment.
From landfill to wire
The biogas is first collected in the extraction wells connected to feeder pipes, which then connect to a main pipeline. The gas is pumped from the landfill by four turboblowers (three operational, one on stand-by) that are driven by a pressure control signal. Before being burned in the engines, the gas is cooled by an exchanger/refrigeration unit to eliminate the water content, which is condensed out and drained. At this stage, the gas is filtered to catch any possible suspended particles before the gas is delivered to the engines. This is a crucial step in ensuring maximum availability, since LFG impurities can harm the working parts of the machinery.
Electricity produced by the generators is converted from 690 V to 27 kV (the grid rating) by transformers and then delivered to the grid. AMIAT has a power purchase agreement with Heracom, an electrical energy trader. Energy and green certificates are sold at the current stock exchange market price, which was 0.13 euros per kWh in September 2004.
AMIAT has been pleased with the results of its newest plant. “We are very satisfied with the new plant, particularly the engines’ energy efficiency, their reliability, the high electrical energy output (the engines can produce continuously 100 % of their rated output) and reduced pollutant emissions obtained by the CL.AIR system,” AMIAT said in a prepared statement.
The solid waste business will be intensifying in Turin as the 2006 Winter Olympic Games draw closer. The Games not only bring considerable attention to host city and country, but they also have a major impact on local government services – including municipal waste disposal. The 2006 Games are projected to generate 1600 tons of waste in Turin – six months after Basse di Stura is scheduled to close.
The head of Turin’s Olympic committee, Mario Rossi – who previously served as head of AMIAT for five years – says that steps are being taken to ensure that the Piedmont Region is not overwhelmed by the additional rubbish generated during the Olympics.
“The next winter games will be the most eco-friendly in history,” Rossi recently declared, noting that the city and region are implementing an aggressive waste separation programme. Most waste will be recycled, while the rest will be incinerated, he said.
For Turin and the surrounding Piedmont region, preparing – in an environmentally approved manner – for their municipal waste problems in 2006 and beyond presents a challenge of Olympic proportions.