Biochar, a form of carbon dioxide sequestration (SDR), is a solid material obtained from the carbonization of biomass. This produces a highly porous charcoal. The biomass is then buried in order to lock the carbon into the soil which can improve soil functions and the CO2 typically produced by the natural degradation of biomass is reduced. This practice is over 2,000 years old and biochar can be found throughout the world as a result of forest fires and historic soil management practices.
Slows actual climate change, rather than actively changing the climate itself
Slows the rate of ocean acidification
Enhances the soil and can be made from waste products, such as chicken manure
Sustainable biochar practices can produce oil and gas byproducts that can be used as fuel, providing clean, renewable energy
Measurable and verifiable carbon sequestration value
Competes with global fuel and food production
Will not prevent sea-level rises
Has questionable efficacy and is predicted to only have the ability to offset 10 percent of the warming caused by increases in CO2
Enhanced weathering is the process of exposing large quantities of minerals that are reactive with carbon dioxide in the atmosphere and storing the resulting compound in the ocean or soil. It is considered a form of carbon dioxide removal or CDR.
Has the potential to increase terrestrial and oceanic net productivity
Can be used to improve agricultural output
Dependent on fossil fuels for execution which may reduce overall efficacy
Insufficient data and inability to accurately predict how fluxes in nutrients will impact Earth’s various systems
Applications of rock powder to the land’s surface may increase overall dust
The mobilization of potentially toxic chemicals from silicate rocks may detrimentally affect the food chain
source: Jens Hartmann, A. J.-G. (2013, May 23). Enhanced chemical weathering as a geoengineering strategy to reduce atmospheric carbon dioxide, supply nutrients, and mitigate ocean acidification. Review of Geophysics, pp. 113-149.
Ocean alkalinity enhancement is increasements in the ocean’s alkalinity via the exposure of large quantities of reactive minerals to carbon dioxide in the atmosphere. The resulting compounds are then stored in the ocean or soil. This form of geoengineering is known as carbon dioxide removal (CDR).
Increased solubility of CO2 in ocean waters
Sequestered carbon becomes inorganic carbon that stays in the ocean permanently
Expensive [estimates at more than 1 trillion USD]
There is a lack of infrastructure needed to effectively facilitate the transformation from limestone to quicklime
Has the potential to release more CO2 into the atmosphere if proper storage and capture facilities are not established
Can be harmful to biotic aquatic systems
Alkalinity must be significantly increased to produce worthwhile results
The production of bioenergy with carbon capture and sequestration is considered a form of carbon dioxide removal (CDR). The process begins by growing biomass, burning it to create energy and finally capturing and sequestering the carbon dioxide created in the process. Negative CO2 emissions are generated by combining bio-energy production [biomass fuel power stations, pulp mills and biofuel plants] with carbon capture and storage technology, allowing carbon dioxide to be captured from the atmosphere and remitted back underground.
Can be fueled by any non-fossilized material of biological origin
Encourages the use of renewable energy sources
Provides opportunities for intersectoral collaborations and partnership development
Dependent on the cost of carbon emissions and the prices must be high enough for the process to be economically viable
Unproven technology that is expensive to develop.
Can only be applied to biomass to yield “negative emission” energy
A large number of operations are necessary in order to achieve results
Geoengineering is deliberate, large-scale intervention in Earth’s natural systems to counteract climate change. The two most common forms are:
SOLAR RADIATION MANAGEMENT (SRM)
SRM techniques aim to reflect a small proportion of the Sun’s energy back into space, counteracting the temperature rise caused by increased levels of greenhouse gases in the atmosphere which absorb energy and raise temperatures. Methods include: albedo enhancement, space reflectors and stratospheric aerosols.
CARBON DIOXIDE REMOVAL (CDR)
These techniques aim to remove carbon dioxide from the atmosphere, directly countering the increased greenhouse effect and ocean acidification. These techniques would have to be implemented on a global scale to have a significant impact on carbon(4). Methods include: afforestation, biochar, bioenergy capture and sequestration, ambient air capture, ocean fertilization, enhanced weathering and ocean alkalinity enhancement.
A description of the different forms can be found in the following posts:
Ocean fertilization is an untested carbon dioxide sequestration (CDR) technique that involves dissolving nitrates or iron into the water which will encourage an increase in carbon uptake by phytoplankton. After the plankton blooms, it dies and then sinks to the ocean floor where the carbon will be stored as sedimentary rock.
Will slow the rate of ocean acidification
Does not directly change the actively changing climate, rather it slows future climate change
Will alter marine systems creating new potential problems
Ambient air capture, a form of carbon dioxide sequestration (CDR), involves building large machines that can remove carbon dioxide directly from the ambient air so that the captured CO2 can be stored elsewhere. The three steps of the air capture process are:
Contacting the air
Absorption or adsorption on a sorbent
Recovery of the sorbent
Manages emissions originating from any source
Full-scale operations are able to absorb significant amounts of carbon, e.g. emissions from 300,000 cars
Can remove far more CO2 per acre of land footprint than trees and plants
Enables the direct extraction of CO2 from the atmosphere
Requires an energy source
Large volumes of air must be processed in order to collect meaningful amounts of CO2
sources: Carbon Engineering Ltd. (n.d.). What is air capture? Retrieved from http://www.carbonengineering.com Lackner, K. S., Brennan, S., Matter, J. M., Park, A.-H. A., Wright, A., & Zwaan, B. v. (2012, June 28). The urgency of the development of CO2 capture from ambient air. Retrieved from http://www.energy.columbia.edu