Situated to the north of Göteborg, Trollhättan has 52 000 inhabitants. The town is a centre for applied technology in the field of environment, transport and energy, and many companies are installed there.

Älvsborgstrafiken, the company which manages the urban public transport system, carries 5 000 passengers per day. In June 1996, the experimental vehicles running on biogas began in Trollhättan, with the introduction of four buses.

The project aimed to bring in fourteen vehicles altogether. Today, they are all running, and several private cars have been added to this total.

The biogas is provided by the Arvidstop wastewater treatment and waste processing plant. The material consists of 75% wastewater and 25% waste from the agrifood industry.

All the buses running in Trollhättan before the introduction of biogas buses, were fitted with catalytic converters and used the most environmentally suitable diesel.

With biofuel, a heavy reduction in emissions has been obtained. According to one estimate, if all the buses ran on biofuel, the municipality would save 8,707.32 euros per year, per bus.

The biogas is produced at the Arvidstorp wastewater treatment and waste processing plant. The material arriving at the station consists of 75% wastewater and 25% waste from the agrifood industry. The plant treats an average of 40 000 m³ of material per day. The resulting organic material is mixed and sent through two digesters with a total capacity of 4 200 m³. It is then broken down by strong anaerobic fermentation (i.e. in the absence of oxygen). This fermentation produces biogas.

After being compressed, the biogas is injected into the distribution network to be routed to the Tingvalla bus station in the town centre, where it is compressed a second time before being stored. The gas in the vehicle tanks is compressed at 200 bar to give the vehicles maximum autonomy. One fill of fuel provides 300- 400 kilometres autonomy, enough for their daily needs.

The biogas buses are generally identical to conventional buses. The only difference is in the use of modified engines and tanks so that they can run on biofuel. All the buses running in Trollhättan before the introduction of biogas buses, were fitted with catalytic converters and used the most environmentally suitable diesel. With biofuel, a heavy reduction in emissions has been obtained.

Taxes are imposed on the quantities of emissions caused by the combustion of diesel and biogas. Except for methane, they are lower for biogas than diesel. According to one estimate, if all the buses ran on biofuel, the municipality would save 8,707.32 euros per year, per bus.

The initial budget, including the production of biogas, storage and distribution, administration and vehicles was 4 909 780 euros. The 1995 changes added an extra 2 907 404 euros to this.

According to this information, the investment linked directly to the production of biogas has not exceeded the initial budget. On the other hand, the investment in setting up the distribution network and storage was higher than expected (budget errors, distribution network longer than envisaged, etc.)

The biogas production site at Trollhättan is economically viable because of Swedish government subsidies. To be viable without subsidies, the site must be expanded and the Municipality must receive income from biogas sales as well as for managing and processing waste sent to the Arvidstorp centre.

Trollhättans Kommun
Phone: +46 520 876 41
anders.lingsten@trollhattan.se

//1996

case

Urban Policy > Urban environment > Environmental sustainability

Renewable energy supplies