Natural gas tens of millions of structures that use the fuel, the individual risk of using natural gas is very low. Natural gas heating systems may cause carbon monoxide poisoning if unvented or poorly vented. In 2011, natural gas furnaces, space heaters, water heaters and stoves were blamed for 11 carbon monoxide deaths in the US. Another 22 deaths were attributed to appliances running on liquified petroleum gas, and 17 deaths on gas of unspecified type. Improvements in natural gas furnace designs have greatly reduced CO poisoning concerns. Detectors are also available that warn of carbon monoxide and/or explosive gas (methane, propane,
Renewable natural gas higher carbon price. SNG is of particular interest in countries with extensive natural gas distribution networks. Core advantages of SNG include compatibility with existing natural gas infrastructure, higher efficiency that Fisher-Tropsch fuels production and smaller-production scale than other second generation biofuel production systems. The Energy Research Centre of the Netherlands has conducted extensive research on large-scale SNG production from woody biomass, based on the importation of feedstocks from abroad. Renewable natural gas plants based on wood can be categorised into two main categories, one being allothermal, which has the energy provided by a source outside of the gasifier. One example