Nature provides us with ample sources of energy - we just need to find ways to utilise these effectively

Bio energy - energy derived from biological sources such as corn, urban waste, human and animal waste, crop residues, food waste, wood chips, algae - is not inherently carbon neutral. In certain circumstances - depending upon various factors such as where it is grown and what it is replacing - it may not even be a carbon reducing technology but in most cases it is.

Arguments that compare the carbon emissions per unit of energy from biomass with those of coal - and sometime find the biomass to emit more - are somewhat spurious because they do not consider the sure of the carbon. The carbon energy that is contained in coal, and that is released through combustion, has been locked in the earth's crust for millions of years and would otherwise stay locked in. Biomass combustion simply returns to the atmosphere the carbon that was absorbed as the plants grew.

If we can combine bio energy with carbon capture and storage (BECCS) we can - in principle - shift into carbon negative territory. The carbon absorbed by the plants as they grow ends up being permanently stored in geological formations. A second best option is that it is stored for hundreds (not thousands) of years as biochar in the soil - this has positive benefits for agriculture too, even if storage is not permanent. A third alternative is not to burn bio oil but to inject it into geological formations for permanent storage) a technology pioneered by the US company Charm.

Bioenergy is produced through combustion, anaerobic digestion, gasification, pyrolysis or fermentation. In some cases bio products - such as wood chips - are burned directly to create heat or electricity. In others, there are intermediate stages as when bio-diesel is made from old vegetable oil or other waste, ethanol is made from corn or biochar is made through low / no oxygen high temperature pyrolysis.

Biochar is a particularly interesting product as - used as a soil amendment - it can store significant quantities of carbon and improve soil health, and thus yields.

The downside of bio energy include: cost, pollution created on burning, relative inferiority of the resulting energy product (e.g. ethanol) and competition for space with other crops and - importantly - existing forests.

The upside is that bioenergy can provide an immediate solution, ready to roll out without big changes in how we operate or the hardware we use. Bio diesel manufacturers claim that their product offers a 90% reduction in carbon emissions for vehicles now (i.e. without waiting for the full electric vehicle revolution to occur) and an 80% reduction in emissions for aviation - all based on the circular economy practice of repurposing waste.