A quick look at natural gas and biogas hybrids

Last year in June, the Institut Français du Pétrole (IFP) participated in the Challenge Bibendum in Mortefontaine, near Paris. IFP presented, with Gaz de France, an all-natural-gas hybrid prototype vehicle developed on a Toyota Prius II base, with which it achieved record fuel efficiency and slashed greenhouse gas emissions compared to a gasoline powered hybrid. The prototype used only 3.56 kg of natural gas for 144 km of combined city and highway driving. In energy terms, this performance is equivalent to a fuel consumption of 3.63 liters of gasoline per 100 km (64.8 miles per gallon). On gasoline the Prius achieves a combined fuel economy of only 5.11 L/100 km (46 mpg). Most impressively, CO2 emissions for the natural gas hybrid were less than 75 g/km.

We have a look at this exceptional car, because it can just as well be fueled by biomethane instead of natural gas, lowering its carbon footprint still further.

Biomethane is obtained from biogas that has been upgraded to natural gas quality. In Europe, the fuel is increasingly used as it is by far the most efficient transport biofuel. In Sweden, Switzerland, Austria and Germany, the gas is already being fed into natural gas grid, and dedicated CNG infrastructures supplied with upgraded biogas are now available. Of all transport biofuels made from dedicated energy crops, biogas by far yields most useable energy per hectare. Researchers have found that for temperate grass species, one hectare can yield between 2,900–5,400 cubic meters of methane per year, enough to fuel an ordinary passenger car for 40,000 to 60,000 kilometers (one acre of crops can power a car for 10,000 to 15,000 miles) (earlier post).

The combination of hybrid technology and biomethane fuel has enormous potential for improving both the fuel economy and cutting the CO2 emissions of vehicles. Last year, the EU published a well-to-wheel analysis of more than 70 different fuels and propulsion technologies but forgot to include biomethane hybrids. After pressure from many organisations, a new version of the document was made available, including the compresed (bio)gas-hybrid (it calls the fuel Compressed Biogas - CBG - analogous to CNG). The CBG-hybrid came out as a concept as efficient and clean as cars powered by hydrogen fuel cells. However, CBG-hybrids do not require the new and expensive infrastructures needed for the hydrogen economy.

The study also looked at coupling carbon capture and storage (CCS) to fuel production. CCS would increase the cost of fuel production, but would considerably reduce greenhouse gas emissions. As we have reported earlier, CCS technologies can be applied to biogas in a cost-effective way, in which case the fuel becomes carbon-negative. Carbon-negative fuels can only be obtained from biomass (more here on a concrete project in the U.S. that is applying CCS to biomass and coal to obtain carbon-neutral jet fuel; if the biomass fraction were to be increased, the fuel would become truly carbon-negative and start taking historic CO2 emissions out of the atmosphere).

In short, one of the cleanest and most efficient vehicles would be a car running on a carbon-negative biofuel coupled to CCS and used in a hybrid-electric propulsion technology or in a fuel cell. The CBG-hybrid would be one of the most promising candidates over the medium term because (1) of all carbon-negative biofuel production pathways, biogas+CCS is the least costly, (2) contrary to hydrogen and fuel cell cars, CNG-hybrids can be brought on the market today, whereas (3) compared to hybrids running on liquid (bio)fuels, CNG-hybrids running on gaseous fuels are more efficient on a well-to-wheel basis:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: natural gas :: CNG :: biogas :: biomethane :: hybrid ::

The IFP and Gaz de France demonstrated that CNG-hybrids can reduce both fuel consumption and CO2 emissions. The vehicle was adapted for natural gas using simple technological solutions, without sacrificing the passenger compartment or the trunk: the gasoline tank is replaced by strong, lightweight natural gas tanks placed under the chassis, with a special manifold, and natural gas injectors replacing the gasoline injectors.

The project was a natural next step in a joint research effort being carried out by IFP and Gaz de France on natural gas as a fuel for vehicles: it was preceded by a first Smart-based demonstrator with a "downsized" engine (an engine having a reduced displacement, turbocharged to preserve performance) running on natural gas alone, developed in 2004, and will soon be followed by a Smart-based natural gas hybrid prototype currently under development.

IFP, a research center active in the fields of energy, transport, and the environment, develops new engine and fuel technologies. In an energy context marked by the need to diversify sources while protecting the environment, IFP devises innovative solutions to meet sustainable mobility needs in the decades to come. Using its unique experience in fuels and engines, IFP is developing alternative fuels (biofuels, synthetic fuels, etc.) and clean, economical vehicles (Natural Gas for Vehicles or biofuels, hybrid powertrains, etc.).

IFP's transport business, and, more specifically, its Powertrain Engineering Business Unit, draws on the skills of multidisciplinary teams, comprising over 200 highly specialized engineers and technicians, and is supported by a very broad range of testing facilities and equipment. The research program is hinged around the following strategic themes: fundamental research (particularly in the field of combustion), low-emission engine technologies (CO2, pollutants, noise), engine control, advanced fuels and lubricants as well as alternative fuels with low greenhouse gas emissions, and demonstrators.

For a number of years, Gaz de France has been using its experience and its extensive industrial experience to make natural gas a genuinely promising alternative fuel. The research that the Group has undertaken in the use of natural gas as a fuel has meant that it is coming to be increasingly used, and that the market is in constant growth, first and foremost with local authorities (buses and cleaning and waste collection vehicles) and, more recently, in company vehicle fleets.

The advantages that natural gas displays mean that it is imposing itself as a credible solution for the necessary changes in road mobility in coming years. Natural gas fuel is a means of reconciling the desires of car users with the challenges facing the transport and energy sectors in the years to come, in terms of the environment, of public health, of energy supplies, prices, performance and comfort of use. Gaz de France offers a whole new energy for automobiles.

References:
IFP: Record fuel efficiency for the first all-natural-gas hybrid prototype developed by IFP and Gaz de France - July 4, 2007.

European Commission, Joint Research Institute, Institute for Environment and Sustainability: Well-to-Wheels reports [updated and revised frequently].

Biopact: A closer look at the revolutionary coal+biomass-to-liquids with carbon storage project - September 13, 2007

Biopact: Report: carbon-negative biomethane cleanest and most efficient biofuel for cars - August 29, 2007

Biopact: Pre-combustion CO2 capture from biogas - the way forward? - March 31, 2007