Driving biogas vehicles could push emissions down to just one third
Refining biomass into transport fuel would mean a significant reduction in climate emissions in Turku, Salo and Kymenlaakso. Calculations made in the framework of the W-Fuel project show that in these regions, emissions from biogas production and consumption, as envisaged in the so-called methane scenario, would amount to just about 30% of the volume foreseen if biogas was not used as transport fuel.
In Helsinki, on the other hand, the reduction of emissions brought about by using biogas as transport fuel would not be as straightforward. The reason for this is that even in the baseline scenario, there would be biogas produced in Helsinki for the generation of electricity and district heat. If biogas was to be used as transport fuel, the electricity and heat from biogas would have to be generated with another, alternative energy source.
In the W-Fuel project, emissions of carbon dioxide, methane and dinitrogen oxide have been calculated according to two different scenarios. The ‘methane scenario’ envisages a situation where, in 2020, there would be a total of about 50 new or already planned biogas plants in Southern Finland making transport fuel out of biogas, whereas in the ‘baseline scenario’, the biomass would be treated in other ways.
Reduction in vehicle emissions comes first
On the basis of a biomass survey conducted in the W-Fuel project, it was estimated that Turku could be home to 23 new biogas plants producing transport fuel. Salo and Kymenlaakso would have enough biomass resources to cover the needs of 13 and 14 new biogas plants, respectively.
Kaisa Manninen, Researcher at the Finnish Environment Institute, says that the total emissions caused by biogas production have been calculated on the basis of the raw material base to be used in the biogas plants and by attributing each type of waste its specific emission factor. Accordingly, the volume of climate emissions generated without biogas production and transport fuel use has also been calculated.
– In Turku, Salo and Kymenlaakso, the major share of the emission reductions would follow from the fact that biomethane, which generates very little emissions, would replace fossil fuels as transport fuel. However, it should be noted that in the methane scenario, bio-waste and other raw materials used in biogas production cannot be used again in energy production. In this case, it would be important to compensate them with renewable energy sources in energy production, Manninen emphasises.
With respect to energy balance sheet, too, biogas production would be environmentally friendly in the above-mentioned regions. Manninen says that the energy consumed in biogas plants for processing and transport of raw materials and other similar purposes would amount to about 20% of the energy content of the produced biogas.
More variables in the biogas formula in Helsinki
Similarly, in the Helsinki region refining biogas into transport fuel would help reduce emissions, but not as pronouncedly as in the other target areas of the W-Fuel project. The reason for this is that in Helsinki, the biomass will be turned into biogas, and consequently electricity and district heat, in any event. Ville Uusitalo, Project Researcher at the Helsinki Region Environmental Service Authority, says that if biogas is channelled to transport fuel use, eventual emission trends depend very much on the energy source that replaces the biogas used in the generation of electricity and heat in the baseline scenario.
– It is impossible to give a precise reduction rate, as there are so many variables in these processes, Uusitalo summarises.
According to the baseline scenario, the biogas production sites in Helsinki would be the biogas plant at the Ämmässuo waste treatment centre and the waste water treatment plants in Viikinmäki and Blominmäki. In the methane scenario, there would be one more biogas plant to be constructed for the treatment of agricultural biomasses.
The type of the substitute energy source is the key
Using biogas as transport fuel would help reduce greenhouse gas emissions from traffic. But to achieve a significant reduction in the total volume of emissions by channelling biogas into transport fuel use, a low-emission energy source must also be used in producing the substitute heat.
Plans made in the framework of the W-Fuel project are based on the assumption that the heat could be produced with renewable energy sources, such as woodchips. Uusitalo emphasises this to be an important element in enabling maximum emission reductions in the wastewater treatment plants and in the biogas plant at the Ämmässuo waste treatment centre.
– However, it is easier to acquire emission reductions in the plant that processes agricultural biomasses, since the baseline scenario does not provide for biogas production from these biomasses, but only for using them in the usual manner, Uusitalo says.