L8 Flashcards
What does the IPCC say aboout negative emissions tech?
“the deployment of carbon dioxide removal to counterbalance hard-to-abate residual emissions is unavoidable if net zero Co2 or GHG emissions are to be achieved.”
to stay below 2oc given the amount of carbon already in the atmosphere we will require negative emissions tech to manage the emissions curve in time
What is the best estimate for mitigation and negative emissions per year to limit warming to 2oc
.5-3 Gt per year
What are four NETS?
- direct air capture
-bioenergy with carbon capture and storage
-enhanced weathering
-nature-based climate solutions
Whare are the 4 global resevoirs of carbon?
Atmosphere
land
ocean
geological
What is the broad theoretical underpinning of a NETS?
if we trap carbon and send it back it is not a NET as it is only addressed emissions going forward rather than previous emissions
if it cannot address past emissions it is not an NET
How does direct air capture work?
Takes carbon from the atmosphere and puts it into the geological reserve
filters the air to capture CO2 but requires a lot of air to capture a meaningful amount of CO2
What are the pros and cons of DAC?
low land footprint
high energy requirments –> to regenerate the absorbant requires electricity
high costs - tech might work but too expensive to be supported by the market?
Can DAC be scaled up in time?
We are currently at .001% capacity - fairly advanced development but difficult to model the tech diffusion
risks associated with assuming DAC can be deployed at scale - potential for a global temperature overshoot of .8oc
How does bionergy with carbon capture and storage work? BECCS
Carbon from the atmosphere goes into land (plants) - burn plants for energy and at that point of burning capture the carbon and put in the geological reservoir
this is negative emissions because the plants sequester carbon first and the carbon is captured from the burning
What are the pros and cons of BECCS?
Pros
generates electricity
modest costs
Cons
High land footprint
biodiversity cost is potentially huge - habitat loss is major threat to biodviersity
Is BECCS scalable?
we would need to scale 3x to provide sufficient Co2 capture and prevent warnings
but more emissions associated with bioenergy as you increase production because…
- conversion of habitats to provide bioenergy
- carbon cost of chopping down a forest outweigh the benefits we get from bioenergy
What are the give major threats to biodiversity?
Habitat degradation
pollution
exploitation
climate change
invasive species and disease
How does rock enhanced rock weathering work?
Atmospheric carbon reacts with minerals transferring carbon into geological reserves
silicate rocks applied to a field participate in this reaction
What are the pros and cons of enhanced weathering?
Pro
low land fooprint
moderate energy requirements
moderate costs
can be applied on any land
the most Co2 removal comes from the fertilisation effect on tress
most of the earths crust is silicate rocks - no geographical constraints
Cons
Co2 is emitted in moving rocks around and grinding them into a powder
changes the soil chemistry and could increase soil C emissions - unknown consequences on the soil and the stream water systems
What reaction does enhanced weathering rely on?
The Urey equation
silicate rocks react with Co2 to produce a bicarbonite ion - transported by ground or river water into the ocean – biological participated into bioorganisms shells at the bottom of the ocean = counter ocean acidification
- but this reaction takes place over millions of years
