The use of biomethane in the transport sector – a viable option?
The potential of biogas production is substantial and its importance is growing, especially in developing and emerging countries where most of the energetic potential of the available biomass is not yet used and energy demand is high. Apart from the unused energetic potential, stored organic material is causing a lot of undesired and uncontrolled methane emissions. The industrial use of biogas, whether via cogeneration (electricity and heat or cold production) or biomethane upgrading (renewable substitute of natural gas) has a lot of advantages:
- a positive impact on climate change mitigation: methane emissions from stored organic materials are reduced,
- replacement of fossil fuels,
- decentral, storable, flexible and clean renewable energy is produced,
- natural fertilizer (from the digestate) is produced (synthetic fertilizers are substituted),
- odour emissions are reduced, and
- the creation of employment and rural development.
In addition to the above mentioned industrial utilization options for biogas, it can be used directly for cooking, heating or lighting purposes in small scale rural applications, which avoids the use of burning wood and thus smoke and deforestation.
However, in this article we want to focus on the use of biomethane (=upgraded biogas) as a transport fuel.
But what actually are biogas and biomethane?
Biogas is the product of anaerobic digestion (AD). AD is a natural process by which micro-organisms break down organic material in the absence of oxygen. Biogas consists of about 50 – 70% methane, approx. 25 – 45% carbon dioxide and smaller amounts of other trace gases. When methane is separated from carbon dioxide and the trace gases, a fuel of high quality is produced, called upgraded biogas or biomethane.
Figure 1: Opportunities to use biogas for electricity and heat generation or as transportation fuel (Source: German Biogas Association)
Biogas plants can be constructed at nearly any size between some m³ biogas per day up to some thousand m³ per hour. The average biogas plant size in Germany is about 400 kWel (installed electric capacity) which is an equivalent to 200 m³/h biogas production (for this you need approx. 11.000 tons of energy crops, 16.000 tons of organic fraction of household waste or 110.000 tons of manure per year). Caused by the economy of scale biogas upgrading plants usually are only economically viable for higher volume rates (only some projects run on 100 m ³/h, most projects above 500 m³/h).
The possibility of injecting biomethane into the natural gas grid makes biogas a very flexible renewable energy source, because the gas grid offers huge storage capacities and electricity can be produced when it is needed (e.g. when there is no energy production from wind and sun). Furthermore, it can support grid stabilization and be used as transport fuel.
Worldwide, some 500 biogas plants are currently upgrading biogas to biomethane quality. More than 450 of them are located in Europe. Most of these upgrading plants inject biomethane into the natural gas grid in order to be distributed together with natural gas to cogeneration plants or to fillings stations in order to be used as a transport fuel in vehicles. Some of the biogas plants have their own filling stations for cars, buses or heavy vehicles. The direct utilization in filling stations has a lot of potential especially in rural areas in developing countries, where a lot of biomass is available and agricultural products need to be transported with vehicles, which could run on compressed natural gas (CNG), e.g. in the food processing, palm oil or sugar cane industry.
Figure 2: Biogas upgrading plants in Europe (Source: European Biogas Association)
There are several upgrading technologies and processes available on the market, like pressure swing adsorption, physical absorption, membrane separation, water scrubber, chemical absorption or cryogenic separation. The most widely used method in the European Union is water scrubbing, followed by chemical absorption. The choice of method depends on local circumstances, like volume rate of biogas production, raw and product gas quality, flexibility, availability of and demand for heat and several other influencing factors.
Biomethane as a transport fuel
Biomethane has similar heating characteristics to natural gas (which consist of about 92 - 96 % of methane) and CNG, when it is compressed to about 200-250 bar. Biomethane and CNG are different to liquefied petroleum gas (LPG), also called autogas (which contains mainly propane and buthane). Vehicles either use CNG or LPG, but cannot switch between CNG and LPG because the motor is adjusted to one of both fuel qualities..
Liquefied natural gas (LNG), which is currently mainly used in heavy transport (usually ships) is also gaining importance. Several countries have developed plans to create a new LNG infrastructure (ports, fuel stations, vehicles, etc). In future biomethane might be blended with LNG (at least in form of sustainable biomethane certificates). This could be done by physical blending of biomethane and natural gas or virtually by buying “green gas certificates”, i.e. certificates from biomethane injection into the gas grid and virtual trade.
Vehicles running on CNG are making an important contribution towards an environmental friendly energy policy in the transport sector. Of course, the contribution to CO2 savings is even higher when vehicles use biomethane (upgraded biogas) instead of natural gas as a fuel. A vehicle operated with biomethane reduces CO2 emissions by up to 90 % compared to a conventional petrol-fueled vehicle.
Generally, biogas could be used as transportation fuel but has some disadvantages if not upgraded to natural gas quality, which is why it is not very common. Often biomethane is injected into the natural gas grid. The operator can receive virtual “green gas certificates” for the amount of biomethane injected. The operator of the gas filling station can buy those certificates and takes out the same energy equivalent at a location were a filling station is located. In that case, there has to be a registering system in place to monitor the trade of injected energy compared to ejected energy. Several countries (like Germany, Austria, Switzerland and Sweden) have already established such a biomethane register. If not injected into the gas grid, biomethane can be compressed into gas cylinders to make it storable and transportable. There are examples were biomethane is produced in rural areas, compressed into gas cylinders, transported to fuel stations and sold there.
Biomethane can be used in all engines usually running on natural gas. The burning characteristics of biomethane are even better than natural gas as biomethane only consists of one inflammable component (methane) while natural gas mainly consist of methane but has some amounts of ethane, propane, butane and even hydrogen. Those other chemicals burn at different conditions (temperature, pressure).
The advantage that biomethane can be used equivalent to natural gas is that there are a lot of established state of the art engines available on the market. Biomethane is today already used in cars, heavy duty vehicles, ships and trains. It is the same to using natural gas and is no problem for vehicles of any brand or model, like
- Audi AR Sportback g-tron,
- Opel Combo,
- VW ecoup,
- VW Caddy TGI,
- Skoda Octavia G-TEC,
- Mercedes-Benz B200 NGD, trucks like IVECO Stralis Hi Road Cabinato CNG,
- Mercedes-Benz Econic NGT,
- Renault D Wide CNG,
- SCANIA P/G 280/340 CNG,
- VOLVO FE CNG or busses like
- IVECO Bus Daily City CNG,
- IVECO Bus Urbanway CNG,
- MAN Lions city CNG,
- SCANIA Citywide LE/LF CNG,
- Solaris Urbino 15 CNG/15 LE CNG,
- Solbus Solcity CNG or
- Vectia Vers 12 CNG.
They all can run on CNG or LNG only or as bi-fuel vehicles (running on either gasoline or natural gas). Existing gasoline-powered vehicles can also be converted to run on gas. In fact, especially in developing and emerging countries this is very frequent.
In Germany there are currently about 1,000 natural gas filling stations, the fleet of gas vehicles being around 100,000. Most of the natural gas filling stations sell a mixture of natural gas and upgraded biogas. But some of them also just sell biomethane coming from biogas plants, which makes them even more environmental friendly. In 2015, there were around 22.7 million natural gas vehicles to be found worldwide, led by China, Iran, Pakistan, Argentina, India and Brazil.
A major aspect for use us of biomethane as fuel, apart from protecting the climate, are financial aspects – it saves money, as it is cheaper for consumers to use biomethane/CNG in comparison to petrol or diesel. One aspect policy makers still need to work on is to make this financial advantage be seen easily at the filling stations, as currently natural gas as fuel is sold by kilogram and not by litre, which makes it difficult to compare prices.
Figure 3: Some examples for CNG fueld cars (Source: CNG Models by Audi, Volkswagen, Iveco and MAN)
In 2018 a milestone project is to be commissioned in Konstanz, Germany, where a ferry between Konstanz and Meersburg will run on either CNG or LNG. The biogas for the ferry will be produced by biogas and liquefaction plants nearby and uses industrial and farm residues as substrate.
Figure 4: A ferry fueled by biomethane (Source: Municipality of Konstanz)
Another example for biomethane use is the biogas plant from BSR (Berliner Stadtreinigung) in Berlin, where around 60,000 tons of organic fractions of separate collected household waste are treated in a plug flow reactor. The produced biogas is upgraded to biomethane and injected to the natural gas grid. BSR fills 150 waste collection trucks with biomethane on three own gas filling station. Therefore 2.5 million liters of diesel and 12,000 tons of CO2 can be avoided.
Figure 5: Biogas and biomethane production from household wastes in the city of Berlin (Source: BSR Ruhleben)
Support or incentive systems
The use of biomethane and natural gas in the transport sector offers several advantages to support reaching a low carbon economy and can play an important role to reduce CO2 emissions. But the production of biomethane seems to be more expensive than natural gas. This is only the case, if you don’t take external factors into account like environmental damage as well as positive impacts on rural development and employment.
Typical support or incentive systems for biomethane production are Feed-in Tariffs (for natural gas equivalents or electricity production), quota systems (e.g. renewable energy quota for transportation fuel), laws (e.g. to limit methane or other emissions a biogas plant might be demanded), financial support (tax reductions, elimination of tariffs or duties, fast depreciation or financial incentives to convert a petrol powered car to a CNG and petrol powered vehicle), support on infrastructure or capacity building (e.g. information/studies, networking opportunities, laboratories, etc.).
Taking the currently low oil prices into account, the development of a biomethane sector very much depends on public incentive systems. Even biomethane usage can be promoted by different incentives. For example: In Sweden the use of biomethane in transportation is highly supported by financial advantages, but also by additional bonuses like free parking or other benefits for renewable vehicles. In Germany, biomethane production focusses mainly on electricity production. Most of Germany’s biomethane is thus injected into the grid and used in combined heat and power plants (CHP). In UK a renewable energy heat law was passed in order to stimulate the production of biomethane by setting a FiT for gas grid injection. CO2 taxes could be a great asset and a possible incentive for developing and operating biogas projects.
In some regions biomethane production is cheaper than local available fuels. In most countries fossil fuels, often oil based fuels (like (crude) oil, diesel, cerosine, petrol or LPG) have to be imported. Refineries are usually located near ports, which means that the price for fuels close to ports go by world market prices. If fuels have to be transported (and it is often transported for hundreds of km within a country), the costs for the same are much higher in the end compared to the costs of fuels which can be purchased near ports. Especially in those regions were (fossil) fuels are expensive, locally produced biomethane offers cheaper fuel supply. This especially applies to rural areas in emerging and developing countries.
Biomethane in emerging and developing countries
Many emerging and developing countries have a huge biomass, biogas and/or biomethane potential. If local fuel prices are high, biomethane production can offer economical interesting options and promising renewable transportation fuel.
The use of CNG as transport fuel is quite common already, but most vehicles are fueled by natural gas and not on biomethane so far. In New Delhi or Bangkok for example, most taxis, public buses or rickshaws run on CNG. Furthermore, we see that recently some countries like India, Brazil, Colombia, China or Mexico have been working on the political framework which will enable biomethane to be injected into the natural gas grid and that the market for biomethane upgrading and its use in vehicles is picking up. It also needs to be mentioned that in some emerging countries the size of biogas plants is far bigger than the average biogas plant size in Europe for example. That creates also a big potential for biomethane upgrading, as it is far more cost efficient in bigger plants.
In Indonesia, Malaysia or Thailand the palm oil industry is an important business. Crucial from an environmental point of view is that liquid effluents of such an industry is usually stored in open lagoons (Palm oil mill effluent – POME). Those lagoons emit enormous amounts of methane but have huge potential for biogas/biomethane production. If a lagoon is covered, methane emissions are highly reduced. Close to Kuala Lumpur, a plant oil production site has a biogas plant in form of a covered lagoon. The biogas is captured and upgraded to biomethane. This biomethane is then compressed in cylinders and transported to a fuel station.
Biogas upgrading to biomethane quality is a state of the art technology which is practiced in more than 500 biomethane production sites worldwide. Biomethane can substitute fossil fuels and helps to establish sustainable, renewable energy in the transportation sector. The use of biomethane and natural gas in the transport sector has still a lot of potential and its use can make important contributions to CO2 savings. Those savings rise significantly when using just biomethane in vehicles. But in order to make the use of upgraded biogas in transport economically viable, a change in energy policy in the transport sector is necessary, as it needs some form of incentive to push the development. Some examples of incentives are Feed-in Tariffs, biogas-upgrading bonuses, quota systems, tax reduction, CO2 tax, renewable fuel quota etc. Therefore under some circumstances biomethane can be viable and for the consumers it is cheaper anyway to use biomethane/CNG in comparison to petrol, especially when oil prices eventually rise. Of course countries with an existing natural gas grid or countries with huge amounts of available biomass have a better starting point.
CNG-powered vehicles can be a bridging technology or even a parallel technology next to electric vehicles. The latter option is to our opinion the more probable scenario, as the situation in the transport sector is similar to that of renewable energies, where the big asset is diversification and the use of the advantages of different sources like wind, sun or biomass.
erdgas mobil, www.erdgas-mobil.de
Natural Gas Vehicles Association Europe , www.ngva.eu
European Biogas Association, www.eba.org
Biogas-Journal, Environmental compatibility with biogas as transport fuel, Thomas Gaul, October 2015
Biogas-Journal, A technical masterpiece: Ferry operates on biogas, Martina Bräsel, November 2016
German Biogas Association, Fachverband Biogas e.V.
International Affairs Consultant
Telephone +49 (0)30 27 58 179-18
Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH
Consultant (EZ-Scout) at the German Biogas Association
Telephone +49 (0)8161 98 46 811