Liquefied biogas

This technology can be applied in vehicles (typically for heavy-duty applications) powered by an internal combustion engine, and fuelled by biomethane. The biomethane is stored in cryogenic tanks, which enables it to be stored at a higher energy density than compressed methane, and is a cost-efficient solution for long-haul trucks. The liquefied biomethane powertrain, including dedicated piston engine, direct injection device and cryogenic tank, faces some technological challenges:
* insulation of on-board liquefied biogas (LBG) storage in cryogenic tank (-162 °C)
* risk of methane slip and incomplete methane combustion (requires combustion system optimisation and dedicated exhaust after-treatment)
Methane slip can also occur from liquefied natural gas (LNG) tank, which releases the evaporative phase methane under high pressure if the engine is not capable of using it.
For this technology to deliver net emissions reductions, the methane should be produced from renewable sources, as use of fossil methane in current engine technologies has no CO2 emissions benefit relative to diesel powertrains.
Exhaust gas after-treatment catalysts should also be enhanced to compensate for the fact that oxidising of methane molecules is difficult, especially at low temperatures (e.g. during engine warm-up, or when the engine is running at low loads). Indeed, since after-treatment of stoichiometric combustion is a far more cost-effective option for reducing methane and other pollutant emissions than both direct injection and diesel lean combustion, most current research efforts focus on enhancing after-treatment systems. As an example, http://www.h2020-longrun.eu/