The clean burning process and price has made heating and cooking with natural gas quite popular in the last couple of decades. However, popularity put a pretty heavy dent in supply, so much so that alternative sources are being explored to meet demand. There are some potentially very green sources of natural gas, but unfortunately some very destructive ones as well. 

On the bright side, there are biogas projects underway that are harnessing methane escaping from landfill sites and other organic materials. While the biogas industry is still in its infancy, it is accessible through Bullfrog power which currently sources natural gas from a landfill site in Quebec.

One not so promising source is from fracking, which is a process for extracting natural gas from shale rock. It involves pumping water and chemicals into shale rock at very high pressure causing the release of methane gas.

While this was at first seen as a relatively harmless extraction method even by environmentalists, it now appears that tapping into this source could be among the more destructive of our fossil fuel operations.

Along with soil and water contamination, there are increased emissions due to unintended methane leaks during the fracking process. In some cases groundwater is so contaminated that water from household taps can even be ignited. Also, extracting natural gas can hardly be called an effective use of our dwindling freshwater supplies.

A study done at Cornell University estimates that over a 20 year period, natural gas fracking will have a greenhouse gas footprint at least 20% higher than coal, and according to the journal Climatic Change,  "perhaps twice as great".

Methods for heating with natural gas:

With a condensing boiler: Water vapor formed during combustion is condensed and recovers the latent heat of condensation. This is a very efficient combustion system, somewhere in the area of 90% to 97%.  There is also very little loss during the transmission of heat energy.
With a conventional boiler: This is a clean burn and it emits very few particles. However, overall efficiency is between 50 and 80%, much lower than a condensing boiler.

Both types of boilers are compatible with hydronic heating systems.

Gas fireplace: A gas fireplace is an efficient way to heat a home and it  creates a nice atmosphere. Source heating is quite enjoyable, and it can allow for heat savings if unoccupied rooms in the house are kept at a lower temperature.