What is the order of energy sources for least net carbon dioxide emission?

Peat

Wood pellet fuel

Agricultural Resdidue pellets and ethanol (grasses, corn stover, straw, rice husks)

Biochar sequestration (produced by torrefaction or pyrolysis).

Pyrolysis (Biomass gasification)

what is the order of energy sources for least net carbon dioxide emission?

Peat is the least carbon efficient fuel source when compared to other fossil fuels such as oil, natural gas or coal, and its combustion can emit over 90% of total CO2 emissions of the full peat energy chain.

Burning wood pellets releases as much or even more carbon dioxide per unit of energy as burning coal, so in order for burning pellets to be carbon-neutral the carbon emitted into the atmosphere has to be recaptured in regenerated forests

Biofuels may be carbon-neutral because the plants that are used to make biofuels (such as corn and sugarcane for ethanol and soy beans and oil palm trees for biodiesel) absorb CO2 as they grow and may offset the CO2 emissions when biofuels are produced and burned.

Growing plants for biofuels is controversial because the land, fertilizers, and energy for growing biofuel crops could be used to grow food crops instead. In some parts of the world, large areas of natural vegetation and forests have been cut down to grow sugar cane for ethanol and soybeans and oil palm trees for biodiesel.

Pyrolysis with biochar carbon sequestration provides a tool to combine sustainable soil management (carbon sequestration), and renewable energy production. While producing renewable energy from biomass, carbon sequestration, agricultural productivity, and environmental quality can be sustained and improved if the biomass is transferred to an inactive carbon pool and redistributed to agricultural fields.