Of fake trees and moondust sunscreen

From a man-made sun-shield to deflect the Sun's rays to giant artificial trees to sequester carbon, radical and potentially risky solutions to stave off climate change are gaining traction

It sounds like the stuff of science fiction: Mining the Moon, not for rare-earth metals or future energy source Helium-3, but for its dust. However, this could be the future.    

In a paper recently published in PLOS Climate, American researchers used computer modelling to propose an unorthodox idea to cool the Earth — creating large clouds of lunar dust in space to reflect sunlight. Benjamin Bromley, Sameer Khan, and Scott Kenyon have found that the fine lunar dust particles are of the right size to scatter sunlight and shield our planet.

The man-made sun-shield for our warming planet, as the aforementioned paper suggests, shall be formed by shooting moondust out towards the first Lagrange (L1) point — one of five areas in space where the Earth and the Sun’s gravity cancel out each other. The dust would linger between the Sun and the Earth for nearly a week, making sunlight around 2 per cent dimmer for earthlings, after which it would disperse; we would then shoot out more dust. “To achieve sunlight attenuation of 1.8 per cent, equivalent to about six days per year of an obscured Sun, the mass of dust in the scenarios we consider must exceed 10/\10 kg (10 billion kg),” the report says.

In a somewhat similar proposal, a group of Harvard researchers is looking into the effectiveness of spraying tiny particles into the stratosphere to reflect the Sun’s rays and reduce the impact of global warming. The project, known as SCoPEx, has Bill Gates’ financial backing.

Though attempts to block the Sun from space are currently not feasible because of financial and technological limitations, space sunshades, according to reports, have support from the UK’s Royal Society and Nasa, to the European Union.

Such an idea is claimed to be first conceived by one James Early in 1989. The original design involved making a 2,000-km-wide glass occulter on the Moon and placing it at the L1 point. Other similar suggestions include 55,000 wire-mesh mirrors and a planet-girdling ring of tiny umbrellas.
 

Not only do solar geoengineering proposals appear to be unfeasible, but they also have a fair share of critics, as altering the Earth’s atmosphere is a risky business. Calling for a moratorium on solar geoengineering, including stratospheric aerosol injection as proposed by SCoPEx, a group of 60 scientists last year argued a cooler Earth means less water would be evaporating from its surfaces into the atmosphere, changing rainfall patterns, and this could have ripple effects across the world’s ecosystems.

Sunscreen for the Earth, however, is not the only such outlandish suggestion to stem the effects of climate change: Among those is force-feeding plankton blooms.

Planktons are one of the most important carbon sinks and a few scientists have suggested forcing the nutrient-rich water into the Pacific Ocean in certain regions to create feedlots for large plankton blooms. There is also a suggestion of giving our seas and oceans a dose of iron.

The idea is: Because iron helps phytoplankton’s growth, our mega water bodies can be fertilised with iron to create huge plankton blooms which, in turn, will suck some of the excess carbon dioxide for photosynthesis. But this process can easily destroy local marine life and have a far-reaching impact on ecology.

Another idea is burying the crises, literally. Many scientists are of the view of trapping excess carbon dioxide (CO2) underground in aquifers, coal beds, or depleted oil and gas fields. Carbon capture, utilisation and storage (CCUS) is a set of technologies designed to capture CO2 from high-emitting activities, such as thermal power plants and industrial facilities. The captured greenhouse gas is then compressed and transported via pipeline, ship, rail, or truck to be used in a range of applications or permanently stored underground. Though a proven technology, CCUS needs gigantic investments in capital-intensive long-lived assets. Besides, many environmental groups are concerned about the gas seeping out of the ground.

Taking a cue from CCUS projects, Physicist Klaus Lackner has installed an artificial tree on Arizona State University’s campus that silently sucks up CO2, which is collected by resin in a reversible chemical process. According to Professor Lackner, the fake tree, though a prototype, can extract CO2 1,000 times faster than a natural tree. Considering 36 gigatonnes emitted by humans every year, it could take nearly 100 million units, each the size of a shipping container, to extract a tonne of CO2 from the air each day (asme.org).

These climate change mitigation proposals, though interesting, fail on one key parameter: Feasibility, be it financial, technological, environmental or political.

Also, they shouldn’t take the focus away from the primary goal of reducing emissions to counter global warming — because if we have to resort to such radical solutions like mining moon dirt or planting fake trees, it is probably too late for us.