Dry trees, shrubs, and other vegetation as well as lightening strikes.
Solar- the sun is not always shining, for example at night you can't get any energy from the sun
Wind-it's not always windy
Water- there can be drought
Really the main issue of all three of these is that they are not always available
since the concentration of Carbon Dioxide will increase, it would make Q > K, cause equilibrium to shift in the direction with less moles of gas to alleviate the extra pressure. In this case, the reaction will shift left because there are fewer moles of gas present.
Mineral because its not a rock