BioNGV retrofit: innovation from a mature technology

ECOl’car solution

For CRMT, the bioNGV retrofit is the energy transformation of a new or already in use diesel vehicle, to make it run only on biomethane, by making technical choices adapted to the targeted use case, in order to improve its environmental quality and operational performance. The bioNGV retrofit methodology developed by CRMT over the last 20 years is now applied and presented on a bus (ECOl’car solution) and an agricultural tractor (RES4LIVE project), installed on the forecourt of the Cité Internationale during the Mix.E. exhibition.

ECOl’car solution, Direction bioGNV: conversion of diesel school buses to bioGNV

Context : Born from a partnership between the CRMT and the transport company Berthelet, ECOl’car is the first diesel school bus converted to BioGNV. The solution reflects the desire of transport players to accelerate the energy transition by enabling vehicles in France to respect air quality and to be part of the circular economy with local renewable energy at a competitive cost. To be developed, the ECOl’car solution was financially supported by ADEME via the AURATRANS 2021 programme and TotalEnergies. The project was approved by the CARA competitiveness cluster and supported by GRDF. Use case : The school buses drive an average of 20,000 km per year, are checked every six months and are therefore in very good functional condition after several years of use. They do not need a long range (target 300 km) and make little or no use of the luggage compartments. CRMT retrofit approach: The vehicle was retrofitted by replacing its Euro V diesel engine with the original new CNG equivalent (Euro VI standard). CRMT integrated the new CNG components including a new after-treatment system, and adapted the diesel vehicle’s function package for CNG operation. The CNG tanks are installed in a part of the luggage compartments, which are rarely used in school buses.

RES4LIVE project: Conversion of a diesel farm tractor to bioNGV

Background : RES4LIVE (Renewable Energy Sources for LIVEstock) is a project funded by the European Union through the Horizon 2020 innovation programme, whose partners’ mission is to develop, adapt and test innovative and promising solutions for fossil fuel-free agriculture. The retrofit of the agricultural tractor presented by CRMT provides a solution to reduce the environmental impact of a market segment for which there is not yet an alternative to diesel: small and medium-sized agricultural tractors. The retrofit work also promotes the energy independence of farmers who already produce their own biogas in anaerobic digestion units, by enabling them to consume their own resources (recovery as vehicle fuel). From summer 2022, the tractor retrofitted by CRMT will be tested and monitored in the “Innovation Farm” (InnvationsHof) of the Leibniz Institute for Agricultural Engineering and Bioeconomy ( (ATB), located at the LVAT (Lehr- und Versuchsanstalt für Tierzucht und Tierhaltung e.V.) experimental farm near Potsdam, Germany. Use case : The farm tractor is used on the farm, to move material in the morning and then in the afternoon (4 hours autonomy), next to a biogas plant equipped with a biogas scrubber and a bio-CNG compressor.

CRMT retrofit approach: In this project, the transformation of the vehicle involves the modification of the diesel engine base, to run on bioNGV. The main steps of this transformation :

  • Modification of the engine to adapt it to gas combustion: adaptation of the cylinder head, modification of the pistons and reduction of the compression ratio, implantation of the spark plug.
  • Integration of the gas engine control system of the CRMT: engine computer which controls the gas components (regulation of the air/gas mixture, injectors, ignition, various sensors).
  • Adaptation of the engine control strategies to the tractor’s use on the farm (power and torque requirements).
  • Addition of an after-treatment system to comply with the latest pollutant emission standards for non-road vehicles.
  • Testing and validation of the CNG engine on the NRMM (Non-Road Mobile Machinery) cycle on a test bench in the CRMT premises.

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