In the context of geoengineering, what are the two main categories?

In the context of geoengineering, the correct identification of the two main categories is solar radiation management and carbon dioxide removal.

Solar radiation management refers to techniques aimed at reflecting a small percentage of the sun's light and heat back into space to counteract climate change. This category includes methods such as deploying reflective aerosols in the stratosphere or enhancing the reflectivity of surfaces on the Earth.

Carbon dioxide removal encompasses strategies that seek to remove CO2 from the atmosphere, storing it in ways that can mitigate climate change. This can involve processes like direct air capture, afforestation, and enhancing soil carbon storage.

The other options presented do not represent the primary focus of geoengineering. Energy efficiency and waste reduction are important for sustainable practices but do not fall under geoengineering. Hydraulic fracturing and biomass generation relate more to energy extraction and production rather than climate intervention techniques. Wind and solar energy are forms of renewable energy generation, which, while crucial for reducing emissions, do not specifically pertain to geoengineering methodologies aimed at altering climate processes directly.