Capturing of CO2 directly from air is a relatively new technology. which has the potential to recapture carbon that has already emitted in to the atmosphere. It might hold the answer towards the problem of global warming.
I want to understand that, what are the future and present prospects of this technology?
If you can do it better than plants, surely. But that's going to be hard. Plants use the Rubisco protein which catches the CO2 molecule from the air and physically smashes it into a sugar to increase the number of carbon atoms in it.
No current alternative system will scale to the size needed as far as I am aware. Sodium hydroxide sounds great - but it requires a LOT of energy to make it, and I doubt the sustainability of the process.
I agree with Tony Maine, the biota have been at this for a while. The problem is that humans are digging them up and burning them at a faster rate than the planet can bury it again.
Try switching away from fossil fuels and give the planet a break.
One more point - you have to actually BURY the plants again. Simply growing them is not enough. I am working on a vegetative CO2 sequestration project at the moment. Sure enough - it involves trees and grasses.
All the proposed means of combatting global warming make your brain hurt and your eyes water, some more than others.
The recent IPCC report identified a number of pathways to limit global temperature rise to 1.5C by circa 2050. These pathways included removing CO2 from the atmosphere using bio-energy carbon capture and storage (BECCS) requiring rates of CO2 removal ranging from 1.5 to 25 billion tonnes per year in 2100. The report also states that the maximum potential removal rate by BECCS is 5 billion tonnes per year, so some of the pathways may not be achievable.
The report states that the land area to capture a billion tonnes of CO2 ranges from 31 to 58 million hectares depending on water availability and soil fertility. Taking the mid-point of 45 million hectares, to capture 5 billion tonnes of CO2 per year will require 225 million hectares of energy cropland. Converting this to units more readily visualised this is 2.25 million square kilometres or 869,000 square miles 9 times the land area of the United Kingdom or 25 percent of the USA. This will be new land usage and will require a reduction in pasture land, lowering beef production and requiring a change in our diets.
Assuming that the energy crop is miscanthus grass (can be harvested and regrown without replanting) then the land will yield around 3 billion tonnes of dried product that is pelletised for ease of feeding to a power plant. The Drax biomass plant uses 9 million tonnes per year fed to 4 x 600-MW converted coal-fired pulverised coal units, which once CCS is added will become 4 x 450 MW units providing 12.6 million MWhs of power to consumers and storing 13 million tonnes of CO2 per year. The 3 billion tonnes of pellets will require 330 similarly sized units generating 4200 million MWh (circa 20% of current world generation) and storing 4.5 billion tonnes of CO2 (CO2 capture efficiency of 90%) per year. The current storage rate is just 200 million tonnes per year so quite a scale up.
The biomass would preferably be grown near both the power plant and suitable storage sites. How many potential sites meet these criteria? Also, can the power generated be used in the area? If the power cannot be utilised then it could be used to generate hydrogen by electrolysis and transported for use elsewhere. The harvesting and processing of the biomass will present its own challenges. All very daunting.
Direct air recovery (DAC) is a new technology. A fan passes air over a CO2-sorbent that when saturated is regenerated using steam. Units are small but may progress to larger sizes as the technology evolves. There are four or five companies developing the technology but very little performance information is available. The largest commercial unit captures 900 tonnes of CO2 per year, so to capture 5 billion tonnes of CO2, 5.56 million units will be required. As wind turbines have to be separated to maximize wind energy, so too DAC units will have to be separated to ensure that the inlet air is not depleted of CO2. Assuming (guessing) 30 m (100 feet) separation, an area of 5090 square km (1990 square miles) will be required. Less area by far than for BECCS but an extensive network of power cables and CO2 pipelines will be required between the individual units.
One estimate is that the power and heat demand for the DAC units is around 2 MWh per tonne of CO2 captured without compression for storage. For 5 billion tonnes of CO2 this requires 10 billion MWh per year (approaching 50% of current world generation) all to be provided from renewable sources. Presumably, DAC plants would have to bear the cost of constucting this additional capacity as it is for their sole use. Note that the demand is twice that generated by BECCCS. Equally daunting but for different reasons. There may be a marriage between BECCS and DAC, with the excess energy from BECCS powering DACS. BECCS and DAC units would have to be co-located to use share steam and storage facilities.
As always, the devil is in the details.
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