Original sentence: But even in areas where shallow ground is too cold to provide adequate heat directly, it can be warmer than winter air.Heat may come from co-generation, from a geothermal electrical plant or from smaller wells or heat exchangers buried in shallow ground
Edited sentence: But even in areas where shallow ground is too cold to provide adequate heat directly, it is still warmer than winter air.Heat may come from co-generation with a geothermal electrical plant or from smaller wells or heat exchangers buried in shallow ground