The new Volkswagen eco up! is currently the world's most fuel-efficient natural gas passenger car. The four-seat Volkswagen consumes just 2.9 kg of natural gas (CNG = Compressed Natural Gas) per 100 km; this is equivalent to CO2 emissions of just 79 g/km. This fuel efficiency leads to very low fuel costs: in Germany, the mentioned 100 km cost just over 3 euros in an eco up! that is available as a two-door or four-door; in Italy, the largest market for natural gas cars in Europe, the cost is even less than 3 euros. Today, it is not possible to drive any other all-round car this inexpensively!
Gas engines as interface to alternative energies
However, one of the greatest benefits of natural gas cars like the VW eco up! is the fact that these models are not limited to being powered by just natural gas, but can also be powered by alternative fuels such as renewable biomethane. Produced from plant by-products, biomethane does not compete with food crops; it is also CO2-neutral, because the car only emits as much carbon dioxide in combustion as it absorbed while the plants were growing. Also true: new methods for producing biomethane - such as obtaining it from straw - will further reduce dependency on classic natural gas. An example: In Germany alone, according to a study by the German Biomass Research Centre in Leipzig, up to 13 million metric tonnes of straw remain unused each year. This biomass could theoretically power four million natural gas vehicles. A first facility for producing biomethane from straw has been operating in Germany since February 2012.
Gas also offers the opportunity of storing electrical energy from renewable sources such as wind power. This involves producing hydrogen by electrolysis, which can be used to operate future fuel cell vehicles. However, until this complex and expensive drive technology debuts on a broad scale, the hydrogen can also be used to produce methane in a second step of the process chain. In turn, the methane can be used as a fuel for cars such as the new eco up!. The world of fuel production and drive systems is on the verge of a revolution. In addition, this synthetically produced natural gas can also be used by gas-powered power plants to generate large amounts of electricity at any desired time. In this way, gas produced from wind energy can serve as a 'battery' for the wind power.
Two decades of Volkswagen with natural gas
Volkswagen has been equipping vehicles with natural gas drives since the beginning of the 1990s - at first as a retrofit in conjunction with the IAV subsidiary in Berlin. However, with the growth of natural gas cars, Volkswagen increasingly worked on original plant solutions. One of the goals here was to minimise the effects of natural gas tanks on interior space. The first new car model to be designed for natural gas was the 2002 Golf Estate 2.0 BiFuel - a natural gas powered vehicle of the compact class. Other important milestones followed in 2006 with the market launches of the Caddy 2.0 EcoFuel (Volkswagen Commercial Vehicles) and the Touran 2.0 EcoFuel - these two models extended Volkswagen natural gas drive into the versatile segments of city delivery vehicles and compact vans. In 2009, the Passat debuted as a pioneering 1.4 TSI EcoFuel - thanks to twincharging by supercharger and turbocharger, the new engine offered dynamic performance never before seen in the field of natural gas drives. In the same year, Volkswagen therefore adopted this drive system for the Touran as well; this EcoFuel engine also impressed in the new model generations of the Passat and Touran.
Today - at the end of 2012 - the company offers six natural gas powered vehicles in various classes: the Caddy 2.0 EcoFuel, the extended Caddy Maxi 2.0 EcoFuel (each 80 kW / 109 PS), the Touran 1.4 TSI EcoFuel, the Passat and Passat Estate 1.4 TSI EcoFuel (each 110 kW / 150 PS) and the entirely new eco up! (50 kW / 68 PS). In 2013, the new Golf will also debut in an EcoFuel version. In this vehicle, Volkswagen is offering one of the world's most versatile natural gas vehicle programmes.
Natural gas and biomethane are pioneering fuels
Natural gas exhibits a significantly higher energy content than petrol or diesel: 1.0 kg of natural gas is equivalent to 1.3 litres of diesel or 1.5 litres of petrol. The energy content of 1.0 kg natural gas amounts to 11.69 kWh; the associated quantity of diesel yields 9.86 kWh, the energy content of petrol is 8.77 kWh. In addition, gas offers the advantage that it can be obtained CO2-neutrally from alternative, renewable raw materials and then combusted: in the combustion of industrially generated biomethane, for example, - it has the same chemical structure as natural gas - the amount of CO2 released is equivalent to the amount previously absorbed by the plants during their growth. Crucial here is the fact that biomethane is obtained from plant by-products and not from the food produced by the plant, which excludes any sort of competition with the food chain.
Share of natural gas vehicles in Europe
On the path towards a future independent of fossil-based oil, natural gas and biomethane - as well as the fuels hydrogen and methane produced by electrolysis - will be important elementary building blocks. With new car models like the Volkswagen eco up!, great progress in the area of producing CO2-neutral gas and extending the refilling station infrastructure as well as governmental support for this type of clean drive will make it possible to significantly expand the share of gas vehicles in large areas of Europe.
In Germany, there are currently around 97,000 natural gas vehicles (as of mid-2012); in 2011, the inventory rose by 4.3 per cent. A look at Italy indicates that this share can be significantly increased under optimal constraints. On the other side of the Alps, the inventory of natural gas vehicles doubled from 382,000 to 785,000 cars between 2005 and 2011. Here natural gas vehicles are promoted with tax advantages, rebates in new car purchases, and exemptions from certain traffic rules. In addition, extension of the natural gas refilling station network is subsidised.
In Germany, however, the full potential has not yet been exhausted, although some natural gas providers already offer rebates of up to 1,250 euros for the purchase of a new car with a natural gas drive, the fuel costs less than petrol or diesel due to a reduced energy tax rate and the number of natural gas refilling stations has risen to 911 (as of October 2012). Given these facts, the fuel strategy of the Federal Republic of Germany assumes that the inventory of natural gas vehicles will rise up to 4 per cent by 2020 - that would be around 1.4 million vehicles. Compared to 2012, that would be an immense increase; the trend in Italy shows, however, that this is feasible.
Biomethane as domestic energy source
Biomethane, often referred to as bio-natural gas, continues to increase in importance thanks to its eco-friendly properties and the possibility of producing in industrial processes in the country in which it is consumed. Even when 'pure' natural gas is used, CO2 emissions are reduced by 24 per cent compared to petrol engines. The CO2 emissions situation is further improved when biomethane is used: when 20 per cent biomethane is added to the natural gas at the refilling station, this by itself reduces CO2 emissions by 39 per cent. When fuelled with pure biomethane, the cars emit up to 97 per cent less CO2! In a well-to-wheel analysis (from raw material sourced to the final drive unit), this would make its CO2 emissions comparable - "to those of fuel cell technology or of pure battery-powered electric vehicles - assuming that the electricity and hydrogen are produced from renewable sources," according to the German Energy Agency (dena).
Global natural gas reserves are estimated to be 525,000 billion m3 (as of 2009) and around 3,000 billion m3 of that amount is extracted annually. So, natural gas is finite as well. This makes a forecast by Berlin-based organisation dena related to the German market for natural gas vehicles for the year 2020 that much more important: "Even if the cited 4 per cent goal is reached, all natural gas vehicles could theoretically be powered with pure biomethane by the year 2020."
By mid-2011, there were already 57 biomethane plants in Germany, which fed 64,000 standard cubic metres (std. m3/h) into the natural gas network per hour. Today, biomethane is blended at one-fourth of the available natural gas refilling stations in Germany; in addition, nearly 100 stations already offer pure biomethane. This number is the most of any country in the world. One of the technical leaders among producers of sustainably obtained biomethane in Germany is Verbio AG (Leipzig). The company specialises in producing biomethane from material such as manure, animal waste, biological wastes and straw - renewable sources that do not complete with food production. The company has developed a new type of bio-refinery that produces biomethane exclusively from stillage, a waste product of bioethanol production, and straw. Another way of obtaining gas from renewable materials has been practiced since early 2012: biomethane production from nothing other than straw. Verbio AG is the first company in the world to succeed at this.
Another expansion stage is offered by what is known as e-gas, which is also known as power-to-gas. As already described, in this case electricity is used to produce hydrogen by electrolysis, and in a second step the hydrogen is converted to methane. Together with a number of project partners - such as SolarFuel GmbH and the Centre for Solar Energy and Hydrogen Research (both in Stuttgart), the Fraunhofer Institute for Wind Energy and Energy Systems Technology (Kassel) and EWE Energie AG (Oldenburg) - the Volkswagen Group found a way, for the first time, to store overcapacities of renewable electricity - e.g. from wind generators or solar power - on a grand scale. In the reverse direction, the stored gas can be used to power electrical generation plants. The electricity can then be used to drive electric cars - especially for drives over shorter distances -, or it can be used as a fuel for gas and fuel cell vehicles that can cover long distances. Another benefit is realised in the converting the electrolysis-generated hydrogen into methane: the conversion consumes CO2, ensuring that it is no longer emitted into the atmosphere as greenhouse gas - this methane will make cars like the VW eco up! even cleaner!