Characteristics of biogas

The Biomass Unit of the CIEMAT Institute of Renewable Energies carried out a thorough study in order to collect as much information as possible on the physical and chemical characteristics of the biogas generated at the landfill site.

The main concern was to have available full preliminary specific information not only on the calorific or energy value of the fuel but also on the presence in the biogas of potentially corrosive compounds that could cause irreparable damage to motors.

Various analyses were carried out in order to determine both calorific value and levels of methane, VOCs (volatile organic compounds), hydrosulphuric acid and water vapour. These compounds are highly corrosive and their presence in substantial concentrations could cause irreparable damage to motors, mainly as a result of the formation of CIH and SH2.

According to the results of the analyses carried out on the main compounds, the methane content is over 50%. This figure confirms the possibility of using the gas as a source of energy, and ensures that the technology envisaged would function properly. It is based on an automatic check of the percentage of methane in the sewer.

The results obtained from the analyses of VOCs and hydrosulphuric acid confirm that the biogas produced may be used without any risk to the energy production equipment. Those compounds which could cause problems by corroding motors are present in small quantities.

However, the analyses also revealed that the biogas is supersaturated with water. This makes it necessary to add a further installation not included in the initial project to eliminate the condensate.

Biogas renewable energy

Helge: We had an early morning chat with Pentti M. He is moving to Spain and we discussed various projects where we could be co-operating. Bioenergy is certainly one of the fields. Pentti informed about the biogas project in Bilbao, Spain.

Biogas is one of the most common sources of renewable energy. It can be produced by the anaerobic fermentation of wood or agricultural or urban waste.

Coherent management of solid urban waste in landfill sites involves the artificial elimination of the gases that accumulate inside the landfill as a result of the actual fermentation of the waste. There are many advantages to using the biogas generated in

Bilbao from urban waste – it is safe, its production generates a considerable profit, it is clean energy, jobs are created, and it contributes to technological development.

Bilbao, located on the estuary of the River Nervion, with a population of more than 400,000, is the administrative capital of the Spanish province of Vizcaya (Biscay).

Since the 1974 crisis, the tertiary sector has taken over from the city's traditional industries. With the creation of the Guggenheim and the new metro, the city's appearance is changing as it takes on a new identity.


Coherent management of Solid Urban Waste (SUW) in landfill sites involves the artificial elimination of the gases that accumulate inside the landfill as a result of the actual fermentation of the waste.

Aware of the problem this poses, the Bilbao municipal authorities, in conjunction with the company operating the landfill site ("Fomento de Construcciones y Contratas, S.A."), in early 1984 devised an ambitious project to assess the possibility of using the biogas generated at the municipal landfill site at Artigas as a source of energy.

The project on this started later that year, with the creation of six shafts and the fitting of a flare stack with a view, initially, to flaring the biogas generated. Work also began on studying the volumes and the physical and chemical characteristics of the Artigas biogas.

It was not until 1988 that the Bilbao municipal authorities, in conjunction with the Basque energy authority ("Ente Vasco de la Energía" – EVE), considered making industrial use of this biogas, which had until then been flared.

A feasibility study was carried out, taking into consideration all the possible uses that could be made of the biogas – sale to industries close to the landfill site, direct use in a furnace to incinerate hospital waste, direct transformation into electricity, etc; the study reached the conclusion that this last alternative was the most viable in technical and economic terms.