A beeswax candle is the most ecological option for burning candles. It is carbon-free, i.e. it produces the same amount of carbon dioxide when it burns as was committed to it during its manufacture.
The candles we designed burn with a clean flame, smell mildly like honey, and do not contain allergens. Thus, they are usually also suitable for people suffering from respiratory diseases or chemical hypersensitivity.
Molded candles drain some wax when burning, so it's good to have a base when burning.
Beeswax is a valuable and versatile biodegradable natural product. Unburnt candle stubs can easily be used to make e.g. furniture wax, which is suitable for all wooden surfaces. In addition to the wax, you only need olive oil.