4.5.1 Sweden

Average data used for calculation of passenger cars:

• An average saving of 0.57 EUR/l of petrol equivalent with CNG (at consumer

• Considering 3%/year increase in petrol price and the same as opportunity cost

In the case of the above parameters, the conversion is expected to take place within 2–3 years, while the purchase price of the new car would be repayable in 5–6 years, mainly depending on the mileage and current petrol prices, if there was no problem with refuelling. In the case of a local public CNG filling station, gasfuelled cars can be recommended primarily to those private individuals who are involved in local transport and travel long distances in a year (e.g. local taxi drivers) or those that are more environmentally sensitive and thus appreciate the benefits of

Biomethane production based on various types of waste and its use as a propellant can be found in several places. At this point, we will introduce some international examples, focusing in more detail on wastewater-based biomethane

As the study by Barisa et al. [55] shows, there are many potential waste-based raw materials available to a settlement that are suitable for biogas and biomethane

• The organic proportion of unsorted municipal solid waste (MSW)

• Separately collected biowaste from restaurants and grocery stores

• Organic waste from the industry (e.g. brewer's grain)

• Separately collected green waste from garden and park management

• Wastewater sludge (including the amount generated by the dairy plant)

With regard to their available volume, it can be said in general that in a given settlement the municipal solid waste, separated green waste and sewage sludge produced in the sewage plant make up the largest amount. However, considering the costs of collecting and separating these three types of raw materials, there may be significant differences. The utilisation of sewage sludge in the sewage plant continuously and, in a relatively homogeneous amount, free of charge—can be considered cost-effective in this respect. In addition, other waste materials can be used safely for biogas production and its subsequent purification in sewage plants. In practice, wastewater treatment plants in many cases include organic food waste/by-products that contribute to improving the carbon-nitrogen

• Conversion cost of EUR 1600 and extra purchase cost of EUR 4000

• 15,000 km/year performance (15-year lifetime)

(assuming use of own money in financing)

• 8 l/100 km of petrol consumption

Transportation Systems Analysis and Assessment

prices)

using gas-fuelled cars.

4.5 Reference plants

production.

production:

152

In Linköping, Sweden, biomethane is used in urban transport, not only for buses and heavy and light motor vehicles but also for trains [56]. The total cost of EUR 14,000,000 invested in 1996 can be mentioned as one of the successful examples of the integration of fuel supply for agriculture, the community and individual transportation. In the Linköping waste-to-energy plant, biogas production was initially based on the by-products and wastes of the crop and livestock (slaughterhouse) sector, while in the framework of a development programme, from 2001, they have also produced renewable propellants from organic waste from public institutions and restaurants [57]. Since 2002, there are only biogas buses in the urban transport fleet, and the CO2 emissions have been reduced by more than 9000 tonnes per year [58].

Another Swedish example is the Nordvästra Skånes Renhållning AB (NSR) biomethane plant in Helsingborg, which generates 80 GWh of biomethane per year from 160,000 tonnes of separated food waste. The methane produced is supplied to the grid and is used for the operation of trucks, taxis and private cars. From 160,000 tonnes of digested food waste in the biogas plant, approximately 490 tonnes of N, 90 tonnes of P and 170 tonnes of K are available for recirculation as fertilizer each year [59].

Another interesting example is the Swedish city of Uppsala. As early as 1996, animal manure and slaughterhouse waste were used for biogas production, and then for biomethane production after purification, which was used for the operation of buses. Thereafter, developments in two stages up to 2010 resulted in the production of biomethane from significant quantities of organic waste from their own city and other settlements; annual production has reached 3000,000 Nm3 [60]. Overall 71 of the city buses were fuelled by biomethane, which amounts for 35% of fuel used in public transport in Uppsala in 2014 [61].

Considering the Swedish examples, it is not surprising that in Swedish households 60% of organic waste is collected separately and utilised.

Sewage water-based biomethane production was implemented in Hammarby Sjöstad (Stockholm), Sweden. Within the framework of the project, an integrated closed wastewater-energy system has been implemented based on local authority/ municipal sewage. After the sewage is purified in the system, propellant biogas and biomethane are also produced, as well as heat and electricity. Hammarby Sjöstad is located in one of the most progressive cities in the world with regard to sustainability. The city has reduced carbon emissions by 25% per resident since 1990 and has established a target of reducing emissions to 3 tonnes of CO2 per capita in 2015. This value is extremely low for developed countries, considering the entire country of Sweden has an average emission rate of 4.5 tonnes of CO2 per capita, while the average for Europe is approx. 6.5 tonnes per capita, and the average for the United States is 16.5 tonnes per capita [62, 63].

#### 4.5.2 Hungary

Sewage-based, biomethane propellant production was also implemented in Zalaegerszeg (Hungary) (Figure 3). The investment began in 2011 and cost 140 million HUF (about 444,000 EUR), of which HUF 120 million was for the biogas

Good practice for usage of biomethane and CNG vehicles:

The Possible Role of Large-Scale Sewage Plants in Local Transport

Good practice of biomethane injection into the natural gas grid:

Public transport, sewage treatment and district heating are mostly operated by local authorities and can therefore be influenced by local decisions, so biomethane can be well integrated into local transport systems, and the terms of sale are not dependent on gas suppliers, either. The latter may be significant in the event of potential future gas price rises, which does not affect the cost of locally produced biomethane. At the same time, it should be noted that the economic interests of biomethane-producing wastewater plants are rather geared towards traditional cogeneration technologies rather than biomethane production because of the sig-

From an environmental point of view, it is also noteworthy that the reduction of the emissions of cadmium due to the use of local public transport with CNG occurs right in the city centre, where air pollution is the most serious problem. From the operation point of view, it is essential that in the case of local transport, there is no danger of emptying fuel tanks, since the filling station is available locally, unlike with long-distance transport. The public education objective of technology is not negligible as many people (those travelling by public transport) are affected by the

Midterm proliferation is expected to take place, given that in October 2014 the European Parliament and the Commission adopted the "Clean Fuel for Transport" package, which obliges member states to take the first steps by 2020 in cities and suburbs and by 2025 on motorways, to make CNG fuelling stations for cars and then

nificant electricity and heat demand of sewage treatment technologies.

allow transport by LNG trucks on Europe's main transport lanes.

• Margarethen am Moos (Austria)

DOI: http://dx.doi.org/10.5772/intechopen.86699

• Margarethen am Moos (Austria)

• Rechnitz (Austria)

• Lille (France)

• Madrid (Spain)

• Sevilla (Spain)

• Vienna (Austria)

• Madrid (Spain)

5. Conclusions

• Utzenstorf (Switzerland)

use of environmentally friendly fuel.

155

• Norrköping (Sweden)

• Norrköping (Sweden)

• St. Gallen (Switzerland)

## Figure 3.

Zalaegerszeg wastewater treatment plant with biomethane filling station. Source: Own photo.

cleaning system, while the cost of the filling station was HUF 20 million. Daily biomethane production is 3600 m<sup>3</sup> , while the biomethane's unit cost is 0.52 EUR/m<sup>3</sup> [64]. Although this value is slightly higher than the consumer price of natural gas, it is just about half as much as the price of diesel oil. Since the substituted buses typically run on diesel oil, the use of CBG should result positive economic effect. The composition of the biogas is 65% methane, 30% carbon dioxide and 5% other gases, including hydrogen sulphide. Raw biogas significantly reduces the lifetime of machines because of its hydrogen sulphide content. For a safe and efficient use, a multistage cleaning process is initiated: gas is pressurised through an activated carbon filter, which reduces sulphur content, other gas content and humidity. Subsequently, 75% methane and 25% carbon dioxide gas is subjected to an aqueous wash, whereby the carbon dioxide is converted to carbonic acid and transferred from the biogas to the aqueous solution. During the production of biomethane, the purified biogas is pressed at a pressure of about 6 bars into the washer, in which the chemical transmission process occurs. After aqueous washing, a 99.7% methane gas is produced, which is excellent for use in CNG vehicles. The biofuel produced fuels for municipal vehicles (12 vans and 3 buses). The CO2 saving can be estimated 22 tonnes/year [65, 66].
