Carbon Neutral vs Climate Neutral
Carbon Neutrality or net-zero CO2 emission is achieved when anthropogenic (caused or influenced by human) CO2 emitted is compensated with an equivalent amount of CO2 removals from the atmosphere over a specific period. Climate neutrality, on the other hand, refers to a state in which there is no net effect of human activities ot the climate system.1 The term has the same concept as carbon neutrality and only differs in that it extends to other anthropogenic greenhouse gas emissions.2 Thus, being more encompassing in its definition, the term climate neutral has been increasingly adopted to denote the cumulative impacts of all GHG on global warming and climate crisis.3
Carbon Negative vs Climate Positive
Carbon Negative denotes that a process or an organization removes more CO2 from the atmosphere than it emits. Climate Positive has similar denotation as Carbon Negative and differs only in the sense that it extends to other greenhouse gases. Removal of CO2 from the atmosphere can be done through carbon sequestration like planting trees. For a product to be carbon-negative means that the process by which it was produced involved more carbon removal than sequestration.4
Alex Steffen, in his book Carbon Zero: Imagining Cities That Can Save the Planet, implies carbon zero as having an annual carbon emission of zero as a key to achieving climate-balanced global economy.5 Carbon zero means there is no carbon emission at all and therefore the need for sequestration or offsetting is eliminated. Contrast this to carbon neutral which means a balance between emission and absorption of carbon from the atmosphere.6 Carbon zero, therefore, is a more effective but also a more ambitious goal to set to avoid the impacts of climate change versus carbon neutrality.
Biogas, Biomethane and RNG
Biogas refers to the gaseous products that is released from anaerobic digestion of biodegradable materials. It consists primarily of methane (50 – 70%), carbon dioxide (30 – 50%), and some trace amounts of particulates and contaminants. Biogas can be produced from different sources such as landfill waste, animal manure, industrial, institutional, and commercial organic waste, and from lignocellulosic biomass such as wood chips and dedicated energy crops.7
The methane component of biogas is called biomethane or renewable natural gas. Once biogas is purified and upgraded to biomethane, the CH4 concentration is elevated to 90% or greater. RNG that is injected into the natural gas pipelines has CH4 concentration between 96 to 98%.8